OIL AND GAS WASTE

This research project is carried out to find out the types of waste generated at the well

during crude oil exploration, development and production

Oil and gas wastes are broadly defined to include; Drilling, operation, and plugging of wells

associated with the exploration, development, or production of oil and gas, including oil and gas

wells, fluid injection wells used in enhanced recovery projects, and disposal wells;

• Separation and treatment of produced fluids in the field or at natural gas processing plants;

• Storage of crude oil before it enters a refinery; • Underground storage of hydrocarbons and

natural gas;

• Transportation of crude oil or natural gas by pipeline; • Solution mining of brine; and • Storage,

hauling, disposal, or reclamation of wastes generated by these activities.

‘Oil and Gas Waste’ includes both hazardous and non‐hazardous wastes arising from

generally oil and gas operations. These wastes may be in a liquid, semi‐liquid or solid form.

A NON HAZARDOUS OIL FIELD WASTE (NOW)

An oil and gas waste may be categorized as non‐hazardous via two avenues ‐ If (1) it meets the

EPA hazardous waste exemption criterion or (2) if it is categorized as non‐hazardous based on

sampling, analytics and/or process knowledge to determine that ignitibility, reactivity,

corrosivity, and toxicity criterion are not exceeded. Both approaches entail details and

misconceptions that challenge accurate categorization of the waste.

NON EXEMPT WASTE

Oil and gas wastes not listed by the EPA as generally exempt may or may not be considered

nonhazardous. If the waste is included in EPA’s non‐exempt list, see Appendix C, the waste does

not meet the ‘uniquely associated with primary field operations’ criterion and may not be

categorized as nonhazardous. Other wastes may be considered non‐hazardous if (1) it meets the

‘uniquely associated with primary field operations’ criterion or (2) the waste is characterized as

non‐hazardous. An oil and gas waste may be categorized as non‐hazardous if it:

• Is not listed by non‐exempt (see Appendix C); and • Is not a Listed Hazardous waste, per

Reference 13 and applicable EPA regulations; and • Is sampled, tested, and does not exceed the

ignitibility, corrosivity, reactivity, toxicity hazardous waste criterion of Reference 13 and

applicable EPA regulations; or • By way of process knowledge is characterized as non‐

hazardous.

A .OIL SPILLAGE

SOURCES OF OIL SPILLAGE

Crude oil spill disasters are due to very many factors such as oil well blow – outs, burst and

leaking pipelines or flow stations, overpressure failure and overflow of process equipment

components, hose failure, failures along pump discharge manifolds, sabotage to well heads and

flow line. The principal factors at play in oil spill at the Niger delta can be broadly classified into

three major groups. (i) Equipment failure due to ageing and malfunctioning of systems, (ii) Act

of sabotage, (iii)Negligence on the part of operators.

ENVIRONMENTAL EFFECTS OF OIL SPILLAGE

The effects of crude oil spills when oil comes ashore it kill shore animals by smothering them, or

if sufficiently fresh, kill them because of its toxic constituents. Oil taints fish and interferes with

fishing activities and navigation. Spilled oil makes a great mess. Polycyclic aromatic

hydrocarbons in crude oil may be toxic, Carcinogenic and teratogenic. Whereas the sea has

enormous capacity to absorb the various attempts by man to degrade it, the streams, creek, rivers,

estuaries, swamps and land have only a little capacity to do so’.

PROBLEMS ASSOCIATED WITH OIL SPILL DISASTER: The devastating effects of oil

spill disaster in Nigeria have long defiled comprehensive solution especially as there are many

unresolved issues on the management of oil spill disaster. The issues can be briefly described as

follows; (1) Oil spill takes time before it is detected and reported to the appropriate agencies.

(2) The response time is too long to allow effective quick cleanup.

(3) Substantial parts of oil spill are caused by act of sabotage and vandals in attempts to claim

damages.

(4) The methods of cleanup and emergency response are not only obsolete they are ineffective.

(5) There are discrepancies in the claim of communities and the estimated damages from the

operating agencies.

(6) There are suspicion by the host communities of the possible cover up of spill by oil

companies (and thus avoid heavy compensation) if the latter (oil companies) want to respond

promptly to oil spill.

(7)The nature of terrain and the characteristics of oil spill areas cannot be ascertained by the oil

companies to send clean up team on time and to fix the price of spill clean up

(8) There is mistrust from the oil companies on the integrity of their contract staff (whom they

accused of framing oil spill to claim allowance).

(9)New and emergency villages spring up at the oil spill site overnight in order to claim

damages.

FATE AND EFFECTS OF SPILLED OIL

This section describes the properties and behavior of spilled oil that are important to a spill

response operation, and the potential effects that the spilled oil and associated response

operations may have in the various environments encountered in the project area.

FATE OF SPILLED OIL

The chemical composition of oil changes due to weathering. Weathering occurs by evaporation,

microbial degradation, chemical oxidation, and photochemical reactions. Some oils weather

rapidly and undergo extensive changes in character, whereas others remain relatively unchanged

over long periods of time. The effects of weathering are generally rapid (1 to 2 days) for

hydrocarbons with lower molecular weights as a result of evaporation. Degradation of the higher

weight fractions is slower and occurs primarily through microbial degradation and chemical

oxidation. The weathering or fate of spilled oil depends on the oil properties and on

environmental conditions. It is important to recognize the dynamic nature of spilled oil and the

fact that the properties of spilled oil can change over time. During a response operation, it is

important to monitor the continuous changes in the properties of the spilled oil, as response

strategies may have to be modified.

(1) Properties; Crude or refined oils vary in their physical and chemical characteristics. These

characteristics affect their volatility, toxicity, weathering rate and persistence. These

characteristics include; (2) Specific gravity (density); Determines if the oil will float on water or

sink. The specific gravity of most crude and refined oils lies between 0.78 and 1.00. The U.S.

petroleum industry has customarily used the so-called °API (Degrees API Gravity). API gravity

is inversely proportional to the true specific gravity and corrects the specific gravity value to

15.5ºC (60ºF), so that on the API scale, freshwater has a specific gravity of 10.00. Light oils with

a low specific gravity (<0.8) have high values on the API Scale (>45), whereas heavier oils have

low API gravity values. The °API gravity places most oils within a convenient range of 10 – 50

°API. The specific gravity of spilled oil will increase with time, as the more volatile (and less

dense)

(3) Pour point — the lowest temperature at which the oil will flow, below which the oil will act

as a semi-solid substance. As ambient air temperatures vary, stranded oil may be alternately fluid

or semi-solid. This property is important in evaluating whether oil will penetrate into sediments

or move down slope.

(4)Viscosity — a measure of the resistance of the oil to flow, or its internal cohesion, that

controls the rates of spreading and the degree to which oil can penetrate into sediments. Low

viscosity oils are light and fluid whereas high viscosity oils are semisolid or tarry. Estimated

viscosity at 70º F of Chad crude is 400–1000 cp (similar to Bunker C).

H 2S unlike other sulphur compounds in crude oils, which tend to accumulate in the

distillation residue, hydrogen sulphide is evolved during distillation or other heating

processes. During an oil spill, this makes it a safety concern, as hydrogen sulphide is a

toxic gas with a time-weighted average (TWA; an 8-hr. exposure limit established by

ACGIH) exposure limit of 10 ppm and a short-term exposure limit (STEL) of 15 ppm

(ACGIH, 1996). Other oil properties to be considered during a response include boiling

point, flash point, surface tension, adhesion, solubility and aromatic content.

Boiling point — determines the temperature at which each hydrocarbon will evaporate.

Many of the light (low boiling) fractions (“light ends”) evaporate at temperatures less

than 20ºC (68ºF). As these light fractions evaporate, the remaining oil is reduced in

volume and becomes denser and more viscous.

Flash point — the lowest temperature at which the fractions of the oil will ignite when

exposed to an ignition source. This is a critical safety parameter; it must be remembered

that a serious hazard may exist if air temperatures are above flash points of light fractions

in spilled oils. Gasoline and other light fuels can be ignited under most ambient

conditions and therefore pose a serious hazard when spilled. Many freshly spilled crude

oils also have low flash points until the lighter components have evaporated or dispersed.

Surface tension — controls the rate at which the oil will spread. Oils with a low surface

tension spread more rapidly, so that a greater surface area is exposed to weathering.

Surface tension is partially controlled by ambient temperatures and decreases as

temperatures increase.

Adhesion — is important in determining whether the oil will stick to sediments or other

materials it comes in contact with.

Solubility — determines if oil will dissolve in water and become toxic to marine life.

Aromatic content — aromatics are more toxic, have a high solubility that may increase

toxic effects, and are more volatile than other hydrocarbon components. Again, it is

important to remember that these properties, and the environmental conditions that affect

them, change over time and should continuously be monitored. For example, as oil

weathers due to evaporation processes after a spill, the specific gravity usually increases,

and the evaporation rate increases with increased temperatures and wind speed.

ON-LAND SPILLS

The pipeline will be buried in order to reduce the risk of leaks and to prevent interference with

agricultural lands and wildlife migration routes. Typically, the pipeline will be buried one meter

underground. In some areas, like stream and road crossings, the pipeline may be buried even

deeper.

Oil movement or flow over the ground surface follows the topography of the land (oilflows

downhill). In general, oil will flow until it reaches a surface water body or a depression, or until

sorbent effects prevent further movement. Oil flowing over land can infiltrate vegetation cover

and soil. The rate of oil movement and depth of penetration are dependent on a variety of factors

and are best determined by direct observation. If ground water becomes contaminated,

contaminants generally remain concentrated in plumes. Because ground water moves relatively

slowly, contaminants do not mix or spread rapidly. Contaminants from ground water may

eventually migrate and appear in surface waters. A leak of heated oil from the pipeline at or near

the pump stations would tend to initially flow faster and be more likely to penetrate permeable or

porous materials than leaks from cooler (pipeline) temperature areas of the oil transportation

system. In the case of a spill, the oil flow speed and ability to penetrate into sediments and soils

would decrease as it cooled.

OFFSHORE SPILLS

The fate of hydrocarbons in the marine environment depends on a number of factors, including

air and water temperatures; the type and amount of nutrients and inorganic substances present;

winds, tides, and currents; and the amount of sediment suspended in the water.

MOVEMENT

Currents and wind are the driving forces for the movement of an offshore oil spill. Ocean

currents have three components: the residual current, the tidal current, and the wind driven

surface currents. Currents produced by fresh or brackish water outflow from a river can also

deflect oil away from a river mouth or estuary.

Residual currents are produced by the long-range motion of water in the ocean caused by the

rotation of the earth, the geometry of the oceans, and temperature differences in the ocean. These

rivers of water within the ocean change slowly, although they may have a seasonal variation.

More localized residual currents can occur due to geometric effects of the ocean-land boundary.

Residual currents generally flow in the same direction for long periods of time. Coastal boundary

currents can trap or contain oil close to a shore (Murray and Owens, 1988) or keep oil away from

a shore. Tidally driven ocean currents are produced by changes in water level caused by

astronomical effects. These currents change both their magnitude and direction with every tidal

cycle. In most cases, the tidal flow is symmetrical with time, particularly in deep water. The net

motion of oil due to tidal currents is very low, even for large currents, because tidal currents

oscillate. If an oil slick is spread over regions with varying water depths, tidal currents can result

in a net advection of the oil. This is due to the fact that the currents are stronger in shallow-water

areas and weaker in deep water. Both the direction and magnitude of future tidal currents can be

predicted easily, after measurements have been taken during tidal cycles. The third type of ocean

current is a surface current generated by the interaction of the wind with the water surface (see

also Section 5.1). The speed of these surface currents is 2–4% of the wind speed (Table 4-2), and

motion is approximately in the direction of the wind. This is the only effect of the wind on oil

motion. Wind-produced waves are oscillatory and do not causes net oil movement in deep water.

PRIMARY WEATHERING PROCESSES

When oil is released onto the water surface, its characteristics start to change due to a number of

physical-chemical processes. All of the processes are interactive. Weathering rates depend on oil

type, physical properties such as viscosity and pour point, chemical properties such as wax

content, amount of oil spilled, weather and sea state conditions, and location (whether oil stays at

sea or is stranded). The primary processes affecting the fate of most spilled oil are: Spreading,

Evaporation, Dispersion, Dissolution and Emulsification. These processes dominate in the first

few days to weeks of a spill, and, except dissolution, these processes may dramatically change

the nature of the oil. In addition, a number of longer term processes include the following:

Biodegradation, Photo- and auto-oxidation and Sedimentation. These longer-term processes are

less important than the first five for the initial prediction of the fate of spilled oil, and their

contribution to the oil fate is typically neglected in models. These are, however, more important

in the later stages of weathering and usually determine the ultimate fate of the spilled oil.

SPREADING: Spreading occurs during the early stages of the spill. According to Fay (1971),

there are three stages of spreading. These are:

(1)Phase One: Gravity-inertia: This early phase occurs immediately after the oil has been

released and is driven by gravity. This is simply due to the fact that oil, being a liquid, will not

remain in a pile. The rate at which the oil moves depends on its inertia; that is, the oil needs time,

due to its mass, to move. The process occurs for a few minutes to hours and is generally finished

by the time a spill response is initiated.

(2)Phase Two; Gravity-viscous: This phase also starts immediately after the oil has been

released and is again caused by gravity. In this phase, however, the viscosity retards the rate of

oil motion. That is, light oil will spread more rapidly than heavy oil. The time span for this

process is from minutes to many hours. As other fate processes act on the oil (for example,

evaporation), viscosity increases, and the spreading process slows.

(3)Phase Three; Surface tension-viscous: This is the final phase of spreading and occurs over a

time period of many hours to days. The driving force is the surface tension, a force at the

molecular level that may make the oil spread on the water. The retarding force is the oil

viscosity.

EVAPORATION

Components of spilled oil evaporate at varying rates and are transported and diluted by

atmospheric processes. Evaporation is usually the most important weathering process in the first

days immediately following a spill. Evaporation may be responsible for the loss of one-third to

two-thirds of an oil spill mass within a few hours or a day (Jordan and Payne, 1980). Rapid

initial loss of the more volatile fractions is.

DISPERSION:

Natural dispersion is the removal of oil from the water surface by its incorporation, in the form

of small droplets, into the water column by wave action. The rate of dispersion depends on the

amount of wave energy at the sea surface. For low energy wave conditions, the rate of dispersion

is low. For high sea states, dispersion may dominate with the result that most of the oil is

removed from the water surface in a few hours. The more viscous the oil, the slower the rate of

dispersion. In the water column, oil is present as small droplets and, thus, has a much higher

surface area in contact with the water. This increases the rate of dissolution and the rate of

natural biodegradation. The rates of both evaporation and dispersion increase with increasing

wind and decreasing viscosity. They are thus competing processes in the oil mass balance.

EMULSIFICATION:

Emulsification is the incorporation of water into oil and is the opposite of dispersion. Small

drops of water become surrounded by oil. In order to emulsify oil, external energy from wave

action is needed. In general, heavier oils emulsify more rapidly than lighter oils. The oil may

remain in a slick, which can contain as much as 70% water by weight and can have a viscosity a

hundred to a thousand times greater than the original oil. Water-in-oil emulsions often are

referred to as “(chocolate) mousse”. Due to its high viscosity, emulsified oil is difficult to

remove from the water surface. Emulsion affects the adhesion properties of oil; this dramatically

affects the on-water recovery options, and an oil-in-water emulsion likely will not stick to shore

zone materials.

SUBMERGED OR SINKING OIL

Oil floats as long as it is less dense that the surrounding water. The density of fresh water is

taken as 1.0 and the density of seawater usually is 1.025 (i.e., it is more dense). As oil weathers

due to evaporation processes after a spill, the specific gravity usually increases. Mixing with

sediments also can alter the specific density of oil. This may occur as oil is washed from a beach

and incorporated with sediments by wave action. Oil on the surface may sink if the density of the

water changes. This may occur in coastal waters where different water bodies meet, such as at

density fronts or at inlets and in estuaries. Current speed and temperature can affect floatation.

The same oil that would sink in calm waters (<0.1 knot) likely will remain on the surface in

currents of more than 0.5 knot. In warm or hot climates, as the water in near shore areas warms

and cools each day, oil that has a density close to that of water may sink during the overnight

cooling and rise again during the daytime warm period, creating sinking and refloating cycles.

Natural collection sites for sinking oils include trenches, depressions and eddy areas. It is often

difficult to obtain information on natural subsurface collection sites.

WHERE OIL STRANDS

On sheltered coasts with small waves; most of the oil will be deposited as a thin band in

the middle to upper intertidal zone (in the zone of wave action).

If washed ashore during periods of storm-wave activity, oil can be carried farther up a

beach and deposited in the supratidal zone (above the limit of most wave action); this oil

is stranded and will not be affected by waves until the next period of high water levels.

On impermeable surfaces (bedrock, solid man-made structures), oil remains on the

surface.

On permeable shores (i.e., shores with sediments), subsurface oil can be present due to

burial and/or penetration.

Oil may penetrate below the surface of a beach, depending on the size of the sediment

and the viscosity of the oil. Only light oils (e.g., a diesel) can penetrate a sand or mixed

sand-gravel beach, whereas all but the more viscous oils can easily penetrate into a

pebble-cobble beach.

ON-LAND SPILLS

It is recognized that despite best management practices the potential exists for accidental releases

of vehicle and equipment fluids and oil to occur. The potential for a spill to occur during

operations allows for the possibility that areas near the pipeline could be affected.

Spills of diesel, gasoline, hydraulic, brake, transmission, and other equipment fluids, as well as

other chemicals, could have an impact on vegetation, animals, and local land use activities. They

could also impact water supplies and aquatic resources if they were to enter surface waters or

groundwater aquifers (see Section 4.2.4, Critical Habitats, discussion of shallow aquifers). Spills

of this nature may tend to be isolated and generally occur on access roads, maintenance facilities,

and other areas where vehicular traffic is common. These impacts would be reduced by control

measures. Any incidents that occur would be small, localized, and intermittent. Crude oil spills

could occur in the Oil Field Development Area and along the PTS during the operational life of

the Project. On land impacts would include infiltration of oil into surrounding vegetation cover

and soils. Animals and birds could ingest contaminated vegetation. Disruption of migration

routes and local activities, such as hunting and agriculture, could also occur, especially during

response activities. Attention should be paid to the considerable numbers of animals that move

through the area regularly on their way to livestock markets. The primary concern of a spill on

land would be to prevent it from impacting surface water channels or groundwater aquifers.

IMPACT OF RESPONSE ACTIVITIES

When soils are moved and compacted by heavy equipment, the particle size and porosity can be

altered, important soil components such as mycorrhiza and seeds can be destroyed, and a loss of

soil nutrients by leaching can occur. Mycorrhiza associated with the root systems of many

tropical plants influence nutrient cycling and germination processes. Response activities utilizing

heavy equipment for oil containment or excavating of oiled soil materials (see Section 8) may

cause a mixing of soil layers and movement of organic materials. Once mixing occurs, essential

nutrients could be leached from topsoil by underlying substrates. This impact would be short-

term and limited to the response area. If soil structure and fertility are degraded by repeated

disturbance, re-establishment of the native vegetation may be greatly retarded. An alternate and

less desirable, successional sequence also could occur, resulting in the rapid establishment of

introduced plant species or undesirable weeds. When this occurs, the normal successional

sequence halts or is dramatically slowed and the regenerative capacity of savanna or forest

habitat could be impaired. Weedy shrubs and woody pioneer species readily re-establish

OFFSHORE SPILLS

Despite best management practices the potential exists for accidental releases of oil to occur

from offshore facilities. The potential for an offshore spill to occur during operations, coupled

with the proximity of the FSO to the shoreline, allows for the possibility that the Cameroon

coastline in the vicinity of the FSO could be affected. The coastal characteristics information

presented in the Cameroon EA, Appendix C, was used to help develop an environmental

sensitivity index (ESI) classification system for the Cameroon coastline between the

Cameroon/Equatorial Guinea border at the mouth of the Ntem River to Point Souelaba at the

mouth of the Cameroon Estuary.

MARINE BIOTA

The effects of an oil spill on marine organisms would depend on the organisms exposed, the

conditions of the exposure, the volume of oil spilled, and other variables at the time of the spill.

Response activities may also affect organisms. Sediment suspension due to disturbance during

response activities could impact the near-shore biota; however, the marine organisms in the FSO

area are well adapted to turbid waters. An oil spill could have potential effects on marine

mammals. Sublethal effects such as changes in normal migration routes and in behavior could

also occur; however, there is a general lack of marine mammal populations in the study area

(none were observed during marine field investigations). Fish could be susceptible to effects of

spilled oil. While juvenile and adult fish would be able to avoid oily areas, the near-surface eggs

and larvae of many species would not be able to do so due to their lack of mobility. Therefore,

these early life stages generally are more susceptible to oil spill impacts. Fish can be affected

indirectly by spilled oil due to death of prey species, or through an effect on reproduction.

Because of the widespread geographic distribution and large reproductive potential of most fish

species, however, recovery from potential impacts as a result of an oil spill is expected to be

rapid. Fishing is a primary economic activity in the proposed project area. Commercial and/or

subsistence fishing could be temporarily halted to avoid harvesting organisms potentially tainted

with oil, or to avoid contamination of boats and gear with oil. Deaths of birds could result from

oil coating their plumage and possibly from the toxic effects of ingesting oil. Certain birds would

be particularly susceptible because they float on the water and dive for food. Sublethal effects

from exposure to spilled oil may also contribute to increased mortality rates under certain

environmental conditions. Although some reduction of phytoplankton productivity could occur

as a result of an oil spill, the impact on phytoplankton populations is expected to be less than

significant because of the widespread distribution and large reproductive potentials of

phytoplankton. Zooplankton could also be affected directly by increased mortality or indirectly

through a decrease in food supply and changes in behavior, respiration, and reproduction.

BENTHOS; The largest impact of an oil spill on the benthic biota probably would result if the

oil sank and coated the bottom. The more toxic, lightweight components probably would have

evaporated or dissolved into the water before the oil reached the bottom. A direct effect would be

mortality from smothering, although some mobile organisms would probably be able to move

through this material. However, for most oil spills, coating of benthic biota has not been

observed.

SANDY INTERTIDAL HABITAT

The physical effects of spilled oil probably would be more significant than chemical toxicity to

the sandy beach biota. By the time the oil reached the shoreline, the more toxic fractions would

likely have evaporated or dissolved. Because of the high-energy nature of sandy beaches, the

residence time of oil is usually short, about one to two tidal cycles. Sandy beaches in the study

area generally have few species, and these species characteristically have a high turnover and

wide geographic distribution. Under these conditions, biotic recovery to pre-spill conditions

would likely occur within one to two years.

ROCKY INTERTIDAL HABITAT

Rocky intertidal habitats in the study area generally support a greater biomass and variety of

plants and animals than do sandy beach habitats. As in the sandy beach habitats, physical effects

of oil would be more likely to cause harmful impacts than would chemical toxicity. Both direct

and indirect effects of spilled oil on rocky habitat organisms could occur. Direct effects include

mortality due to smothering; indirect effects include behavioral changes due to the coating of the

substrate. Although local, short-term impacts could be significant long-term impacts are typically

rare for these habitats. The high-energy nature of the environment generally leads to a relatively

rapid recovery of available habitat and decolonization by most species. Recovery to pre-spill

conditions would likely occur within one to three years.

TOURISM/RECREATIONAL BEACH USE

An oil spill that reaches the beaches could halt the tourism/recreational use of beaches until

cleanup had been completed.. While a decline in tourism might be felt by local population

centers most affected by a spill, the overall level of tourism in the event of a large spill in the

region would be expected to remain relatively stable. Thus, the short term impacts of an oil spill

on tourism/recreation beach use could be significant in the areas affected by the spill; however,

the longer-term impacts would be mitigated by the cleanup.

POTENTIAL IMPACTS DUE TO RESPONSE

Commercial and/or subsistence fishing could be interrupted as a result of fishing vessels being

confined to port by oil containment booms.

RIVER SPILLS

Spills during construction or resulting from pipeline releases at river crossing may lead to oil

impacts on rivers in Chad or Cameroon. In marine oil spills, it is very unusual to consider the

water itself as a resource to be protected. Spilled oil may move over or through the water, but the

water itself is not usually thought to be damaged. For inland spills this is not true. In many cases,

the water is used as a primary resource (potable water) and threats to the water supply are a

public health problem, immediately escalating the level of concern in river spills. If spills are

allowed to enter surface waters, the decrease in water quality following such an event could also

adversely affect botanical, wildlife, and other aquatic resources. Crude oil is generally lighter

than water and floats on the surface, potentially coating or causing impact to animals and plants

that it may contact. While these impacts could be significant, their likelihood of occurrence

would be minimized by the implementation of oil spill response countermeasures and associated

safety and environmental protection measures. Streams and rivers in the project area appear to

support relatively small populations of fish, invertebrates, and other organisms. In the Nanga

Eboko area fishing is mostly on the Sanaga and in small streams. Fishing is less important in

streams and rivers elsewhere in the project area. As in marine spills, the nature of the shoreline

will determine the amount of potential damage that a spill could cause. The flat gradients of the

rivers in southern Chad allow development of extensive sandbanks that attract winter migrant

wading birds as well as local black-crowned cranes (Balearica pavonina), Maribou storks

(Leptoptilus crumeniferus), herons, egrets, and plovers. The vertical, sandy banks are well suited

for colonies of Carmine bee eaters (Merops nubicus) and red-throated bee eaters (M. bulockii).

Flooding can strand pollution at high levels and threaten larger areas than might otherwise be

expected. During a flood event, high water could transport oil into overbank habitats and impact

large areas of the floodplains. Agricultural crops and grazing lands may be affected during these

situations. Floodplains also are recognized as being important historically as fish nursery sites in

Benech and Leveque (in Burgis and Symoens, 1987). The impacts of spill response activities to

these areas would be similar to those for on-land spills. Effects of response operations on

botanical resources could include direct disturbance to, or loss of, individuals or populations of

plant species. Temporary and permanent loss of riverine (gallery) vegetation could occur during

disruptive response operations on the Nya, Loulé and Pendé river floodplains. Erosion and

sediment transport would be minimized during response by the use of prudent erosion control

practices.

CRITICAL HABITATS

Pipeline routing and facility sitting has been undertaken to avoid various biologically important

locations near the project area, including:

Important wildlife habitats in the Faro Reserve.

The Laramanay Wildlife Reserve; a proposed hunting reserve approximately 7 km north

of the proposed pipeline route, east of Bam and Bégangber (see Figure A-1, Appendix

A), which is reported to contain important habitat for elephants that may migrate between

Chad and Cameroon.

The Logon floodplain is a wetland area that contains valuable gallery forest and marsh

habitat that supports relatively diverse bird and mammal populations and provides

important grazing habitat for resident and trans-human livestock.

A large contiguous stand of African bamboo (Oxyanthera abyssinica) northeast of

Bessao contains important timber and fuel wood resources for local residents and also provides

important elephant habitat. This is not currently an official reserve, though it is a recognized area

of value to local residents.

SHALLOW AQUIFERS

Shallow aquifers of the Doba Basin provide almost all of the water supplies for the population of

the area. The most common domestic water supply source is through wells or occasional hand

pumps. Some of the traditional hand dug wells have little protection against surface runoff, and

spilled oil flowing on the ground surface in their vicinity could infiltrate these wells. Some of

these wells are located in the floodplains of nearby streams, are only 5 to 8 m deep, and

presumably capture water of the same or similar quality as that contributing base flows to the

streams in the area. The groundwater gradient follows the topographic slopes. A groundwater

contour map for the upper shallow zones of the aquifer is included as Figure 6.4-3 in the Chad

EA. The data indicate that the direction of shallow groundwater flow in the vicinity of the Komé

and Bolobo well fields is toward the north and northeast, i.e., toward the Nya River, and toward

the east in the vicinity of the Miandoum well field. The clay and silty surface soils within the

project area should form a barrier to the aquifers from above.

ENDANGERED AND SENSITIVE SPECIES

The only significant biological habitats remaining in the vicinity of the oil field development

area and pipeline in Chad consist mainly of remnant gallery forest and herbaceous wetland

vegetation in the alluvial floodplains of major watercourses, and occasional stands of African

bamboo (Oxyanthera abyssinica) in the region around Bessao and Baibokoum. The pipeline has

been routed to avoid large stands of bamboo. The Mbéré Rift Valley supports a great variety of

animals, including large mammals. A large portion of the Mbéré Rift Valley in Cameroon

(comprising approximately 60 km of the 320 km pipeline route) is unique in its relative lack of

disturbance. It has a high diversity and abundance of wildlife, including elephant, hippopotamus,

bongo, and eland, and little-disturbed diverse vegetation including wooded savanna and gallery

forest. Response activities are expected to have little impact on those wildlife resources that

remain in the area. Agricultural activity has long since displaced most of the natural habitats and

associated wildlife of the region. Temporarily disturbed areas could be re-colonized and

repopulated by the same species, but probably not by the same individuals, depending on the

degree and extent of disturbance. Such differences could affect the ability of certain species to

return and persist in remaining natural habitat fragments. Consequently, a limited number of

individuals could be affected during response operations. The following regionally sensitive

mammal species have the potential to occur in the study area (see EAs for details).

Giant eland (Tragelaphus derbianus gigas) — formerly occurred in SW Chad in the

wooded savanna zone. It may be completely absent from Chad today.

Red-flanked duiker (Cephalophus rufilatus) - This small antelope species was restricted

to gallery forests in the wooded savanna zone of Logon Oriental and Moyen Chari

prefectures. The population, if it exists, does not appear to be large.

Grey duiker (Sylvicapra grimmia) -This small antelope species was, until recently,

widespread throughout the savanna zone of southern Chad. Its total population today is

not thought to be abundant overall.

Bushbuck (Tragelaphus scriptus) -This species normally is confined to areas with

sufficient cover near permanent water (i.e., gallery forest). Once locally common, total

numbers today are unknown.

Buffon's or western kob (Kobus kob) -This species occurs along permanent watercourses

within the savanna zone. It may still possibly occur on isolated floodplains in less

populated areas.

Roan (Hippotragus equinus) -This species exists in moderate numbers throughout most of

the savanna zone of southern Chad, but has been eliminated from densely populated

regions.

Oribi (Ourebia ourebi) -This species was once widespread in the southern savannas of

Chad, south of latitude 11º north.

African elephant (Loxodontia africana) -Some elephant habitat exists within the

Laramanay Reserve, and there may be some use of this area by seasonally migrating

elephants. Elephants occur in the Mbéré Rift Valley, the forest in the region east of the

Sanaga River, and in the vicinity of the Campo Reserve in Cameroon.

African linsang (Poiana richardsonii) -This species appears to be very rare in the

Cameroon Atlantic littoral evergreen forest and are threatened by continued hunting

pressure.

Gorillas -while uncommon, can be observed in the Semideciduous Forest off the road

between Deng Deng and Bélabo.

The following sensitive bird species have the potential to occur in the study area:

River prinia (Prinia fluviatilis)-This bird species was known only from waterside

Vegetation in a few localities in southern Chad (Chappuis, 1974). It prefers marshy

Floodplain vegetation for nesting and foraging.

The Mbéré Rift Valley is not exceptionally rich in bird species, but it is possible to find

several species of eagle. The rare Abyssinian calao might be present in the zone, as well

as the big bustard.

In addition to the above, there are wildlife species whose status in Chad is thought to be

reasonably secure at present, either within or outside existing parks. These species are

partially protected under Article 25 of Chadian Wildlife Legislation. They include:

Antbear, Aardvark (Orycteropus afer) -The status of this species is uncertain. It is a

nocturnal animal relatively widespread in savanna areas where termite species occur.

Serval (Leptailurus serval) - This felid is a hardy survivor in floodplains and near rivers.

All vultures (Gyps and related genera) — All species currently appear to be stable, but

the white-headed vulture (Gypohierax angolensis) is the least common.

Cattle egret (Bubulcus ibis), little egret (Egretta garzetta), yellow-billed egret (Egretta

Intermedia), and great white egret (Casmerodius alba) — These species are widespread to

occasional along rivers.

Marabou stork (Leptoptilus crumenifer) — This species is common near water.

Saddlebill stork (Ephippiorhynchus senegalensis) — This species is occasionally found

along rivers, lakes, and open flooded areas.

Borassus aethiopum — a threatened endangered tree.

Some species are still numerous in the Semideciduous Forest areas of Cameroon, buare

beginning to decline in numbers. These include the bongo (Boocercus euryceros),blue

duiker, chevrotain, water chevrotain, several monkey species (e.g., potto, galago,

colobus, and chimpanzee), African ground squirrel (Euxerus erythopus), caracal, serval

(Felis serval) and golden cat (Felis aurata). This decline is due to hunting pressure and

loss of habitat from human activity. The warthog is not seen frequently and lion, leopard,

and spotted hyena, though once present, apparently have disappeared from the region.

ARCHAEOLOGICAL AND SACRED SITES

Sacred sites would pose a problem because they are not identified easily by outsiders.

On the other hand, local people state that they would be more than willing to identify such sites

to contractors in advance of response work crews and to move sacred objects to new sites

whenever possible. There is a strong prohibition against the disturbance of physical remains

(buried in household compounds; in most villages, cemeteries are reserved for the burial of

“strangers”). If absolutely necessary, ancestral remains may be moved to another site. This,

however, has to be carried out in close consultation with the owners of the remain sand be

accompanied by certain rituals that should be performed by the descendants themselves. Another

issue involves local religious beliefs. Many areas are considered to merit “special handling”. In a

fishing village in the peri-urban area of Kribi, for example, a water spirit is believed to exist that

needs regular appeasement. In other areas, forest spirits frighten people from certain areas and

cast their curses on individuals who might try to dare the spirits. The appeasement of spirits

involves certain essential rituals that are performed by the local “notables”. In most of the “spirit

culture” areas, locals believe that if projects do not do “what is necessary” they are doomed to

fail. An implication of this sort of belief is that if these rituals are not performed in the manner

considered adequate by the local know how, project-related accidents, no matter how minor, are

likely to be attributed to spirits that are “taking revenge” on those who showed them disrespect.

It is estimated that half of the labor force may refuse to work if accidents are attributed to the

violation of certain rituals, especially if they feel physically or spiritually threatened. It is

essential to note that most sacred areas are neither clearly marked nor easily identifiable. In fact,

they might be known only to the very small groups that perform their rituals there; it is therefore

important to verify the presence of such places in each area when making response operations

decisions.

TREATMENT OIL SPILLAGE

Methods for cleaning up include:

BIOREMEDIATION ACCELERATOR:

Bioremediation: use of microorganisms or biological agents to break down or remove oil.

Oleophilic, hydrophobic chemical, containing no bacteria, which chemically and physically

bonds to both soluble and insoluble hydrocarbons. The bioremediation accelerator acts as a

herding agent in water and on the surface, floating molecules to the surface of the water,

including solubles such as phenols and BTEX, forming gel-like agglomerations. Undetectable

levels of hydrocarbons can be obtained in produced water and manageable water columns. By

over spraying sheen with bioremediation accelerator, sheen is eliminated within minutes.

Whether applied on land or on water, the nutrient-rich emulsion creates a bloom of local,

indigenous, pre-existing, hydrocarbon-consuming bacteria. Those specific bacteria break down

the hydrocarbons into water and carbon dioxide, with EPA tests showing 98% of alkanes

biodegraded in 28 days; and aromatics being biodegraded 200 times faster than in nature they

also sometimes use the hydro fireboom to clean the oil up by taking it away from most of the oil

and burning it.

BURNING

Controlled burning can effectively reduce the amount of oil in water, if done properly. But it can

only be done in low wind, and can cause air pollution. Burning of oil can actually remove up to

98% of an oil spill. The spill must be a minimum of three millimeters thick and it must be

relatively fresh for this method to work. There has been some success with this technique in

Canada. The burning of oil during the Gulf War was found not as large a problem as first thought

because the amount of pollution in the atmosphere did not reach the expected high levels. Field-

testing is needed to check.

USE OF DISPERSANTER

Dispersants act as detergents, clustering around oil globules and allowing them to be carried

away in the water. This improves the surface aesthetically, and mobilizes the oil. Smaller oil

droplets, scattered by currents, may cause less harm and may degrade more easily. But the

dispersed oil droplets infiltrate into deeper water and can lethally contaminate coral. Recent

research indicates that some dispersants are toxic to corals. Watch and wait: in some cases,

natural attenuation of oil may be most appropriate, due to the invasive nature of facilitated

methods of remediation, particularly in ecologically sensitive areas such as wetlands. ; Dredging:

for oils dispersed with detergents and other oils denser than water. ; Skimming: Requires calm

waters.

SOLIDIFYING: Solidifiers are composed of dry hydrophobic polymers that both adsorb and

absorb. They clean up oil spills by changing the physical state of spilled oil from liquid to a

semi-solid or a rubber-like material that floats on water. Solidifiers are insoluble in water,

therefore the removal of the solidified oil is easy and the oil will not leach out. Solidifiers have

been proven to be relatively non-toxic to aquatic and wild life and have been proven to suppress

harmful vapors commonly associated with hydrocarbons such as Benzene, Xylene, Methyl Ethyl,

Acetone and Naphtha. The reaction time for solidification of oil is controlled by the surf area or

size of the polymer as well as the viscosity of the oil. Some solidifier product manufactures

claim the solidified oil can be disposed of in landfills, recycled as an additive in asphalt or rubber

products, or burned as a low ash fuel. A solidifier called C.I.Agent (manufactured by C.I.Agent

Solutions of Louisville, Kentucky) is being used by BP in granular form as well as in Marine and

Sheen Booms on Dauphin Island, AL and Fort Morgan, MS to aid in the Deepwater Horizon oil

spill cleanup.

VACUUM AND CENTRIFUGE: Oil can be sucked up along with the water, and then a

centrifuge can be used to separate the oil from the water - allowing a tanker to be filled with near

pure oil. Usually, the water is returned to the sea, making the process more efficient, but

allowing small amounts of oil to go back as well. This issue has hampered the use of centrifuges

due to a United States regulation limiting the amount of oil in water returned to the sea.

Equipment used includes (1) Booms: large floating barriers that round up oil and lift the oil off

the water.It’s easier to clean-up oil if it’s all in one spot, so equipment called containment booms

act like a fence to keep the oil from spreading or floating away. Booms float on the surface and

have three parts: a ‘freeboard’ or part that rises above the water surface and contains the oil and

prevents it from splashing over the top, a ‘skirt’ that rides below the surface and prevents the oil

from being pushed under the booms and escaping, and some kind of cable or chain that connects,

strengthens, and stabilizes the boom. Connected sections of boom are placed around the oil spill

until it is totally surrounded and contained

(2) Skimmers: Skimmers are machines that suck the oil up like a vacuum cleaner, blot the oil

from the surface with oil-attracting materials, or physically separate the oil from the water so that

it spills over a dam into a tank. Much of the spilled oil can be recovered with skimmers. The

recovered oil has to be stored somewhere though, so storage tanks or barges have to be brought

to the spill to hold the collected oil. Skimmers get clogged easily and don’t work well on large

oil spills or when the water is rough.

(3) Sorbents: These are materials that soak up liquids by either absorption or adsorption. Oil

will coat some materials by forming a liquid layer on their surface (adsorption). This property

makes removing the oil from the water much easier. This is why hay is put on beaches near an

oil spill or why materials like vermiculite are spread over spilled oil. One problem with using

this method is that once the material is coated with oil, it may then be heavier than water. Then

you have the problem of the oil-coated material sinking to the bottom where it could harm

animals living there. Absorbent materials, very much like paper towels, are used to soak up oil

from the water’s surface or even from rocks and animal life on shore that becomes coated with

oil.

(4) Chemical and biological agents: helps to break down the oil Chemicals, such as detergents,

break apart floating oil into small particles or drops so that the oil is no longer in a layer on the

water’s surface. These chemicals break up a layer of oil into small droplets. These small droplets

of oil then disperse or mix with the water. The problem with this method is that dispersants

often harm marine life and the dispersed oil remains in the body of water where it is toxic to

marine life.

(5) Vacuums: remove oil from beaches and water surface

(6) Shovels and other road equipments: typically used to clean up oil on beaches

B. PRODUCED WATER ; Water is very often found together with petroleum in the reservoirs

where the water, as a consequence of higher density than oil, lays in vast layers below the

hydrocarbons in the porous reservoir media. This water, which occurs naturally in the reservoir,

is commonly known as formation water. After oil and gas production has been occurring for a

time, the formation water will reach the production wells and water production will initiate. The

well water-cuts will normally increase throughout the whole oil and gas field lifetime, such that

when the oil production from the field is shut down, the oil content can be as low as a couple of

percent with ninety eight percent water. To maintain the hydraulic pressure in the petroleum

reservoir, which is reduced as soon as production is started, seawater is commonly pumped into

the reservoir water layer below the hydrocarbons. This pressure maintenance due to water

injection causes high extensions in recoverable hydrocarbons but simultaneously contributes to

increased water production.

PRODUCED WATER COMPOSITION: The compositions of formation water originally in

place vary significantly in characteristics between the different reservoirs. As field production is

initiated, produced water composition from the production wells may be continuously

transformed due to injection of seawater, reinjection of produced water, reservoir stimulation,

bacterial activity, introduction of production chemicals and more. Produced water is basically a

mixture of formation water and injected water but also contains smaller quantities of: Dissolved

organics (included hydrocarbons), Traces of heavy metals, Dissolved minerals, Suspended oil

(non-polar), Solids (sand, silt) and Production chemicals. Dissolved hydrocarbons are found

naturally in formation water and can be both toxic and bio-accumulative. Such water-soluble

components, which in produced water are mainly BTEX (benzene, toluene, ethyl benzene and

xylene), polyaromatic hydrocarbons (PAH) and alkylphenols, are together with heavy metals

considered the most harmful contaminants in produced water.

PRODUCED WATER IMPACT ON THE ENVIRONMENT

The most common practice in use in the North East Atlantic for management of produced water

is treatment in gravity based separation equipment and discharge to sea. For a long time the only

governmental regulation for produced water discharges in this petroleum sector has been

concerning concentration of non-polar oil in water (OIW). Little attention has been given to

dissolved organics. There is now wide agreement within the petroleum industry, governments

and scientists that focus should now be put on dissolved organic components, heavy metals and

production chemicals. The oil in water content shall be as low as possible and the industry shall

make use of best available technology (BAT). The quantity of produced water in Figure 3 that is

not discharged to sea is re-injected into the reservoir or to another formation suitable for

disposal. The long-term effects of such contaminants on the environment are not fully

documented and understood. Some research programmed is completed and several new studies

are underway to map possible consequences for living organisms. Dilution aspects and

movement of species in the oceans makes definite conclusions hard to make. There are so many

variable that the modelling is extremely complex. Results from recent research show however

that fish exposed to alkyl phenols have disturbances in both organs and fertility. These results are

serious and have triggered further investigations.

1 CONVENTIONAL TECHNOLOGY FOR WATER TREATMENT

During petroleum production, vast volumes of liquids have to be managed each day. Deferred

production causes high economical losses and therefore continuous operations are always strived

for. The capacity, reliability and performance of the produced water management system is often

critical for continuous oil production particularly in mature oil field where the water production

can greatly exceed the oil production. The water production system needs to be designed to

receive continuously increasing quantities of water as oil production continues.

2 GRAVITY BASED SEPARATION - FLOTATION

Produced water treatment has traditionally taken place in gravity based equipment, where the

difference in the density of the two liquids to be separated is utilized. Such separation is

commonly performed in huge horizontal tanks at different pressures. Flotation of the lighter

components (oil) can be enhanced by means of finely distribute solution (pressure reduction) and

parallel plate packages installed diagonally in the separation vessel.

3 SEPARATION TECHNIQUES BASED ON FILTRATION

A well known technique for separating non soluble components is by filtration. Several

principles for handling produced water have been considered including microfiltration

membranes and media filters. Such treatment technologies are potentially advantageous because

of very good separation degrees can be achieved. However microfiltrations have found very

limited practical application because of cost and poor operability, very high energy consumption

and degradation of the filters elements with use.

4 CYCLONIC SEPARATION METHODS

The continuous demand for higher treatment capacity in very limited space has resulted in

improved treatment methods. The most commonly used technology in offshore production since

around 1990 is the static hydro cyclone that utilizes available pressure for enhanced speed in

gravity separation. The advantages for this equipment type are high reliability (no moving parts),

low maintenance, requires very little space, and gives good separation effect and high capacity

shows the water (red) going out in the underflow, while oil (blue) is forced into the middle and

led out in the cyclone overflow. Another application for separation of oil and water is high-effect

centrifuges. Because the device is motor driven it is often used for low pressure water streams.

This kind of equipment has high energy and higher maintenance requirements

NEW CHALLENGES IN HANDLING PRODUCED WATER

Gravity based separation techniques have together with static hydro cyclones been the most

extensive method for treating produced water. Other types of equipment have also been utilized,

mostly in special cases with difficult operating treatment characteristics or small volumes,

though to a less extent. Even if produced water systems more or less have functioned as intended

with respect to the design specifications, the future has brought new considerations regarding

what is sufficient treatment. A good alternative for disposal of produced water would be to send

it back into the reservoir where it came from as part of the pressure support, or to another

suitable formation. Unfortunately this requires extensive treatment prior to re- injection and due

to high costs it is an economically viable alternative mainly for fields with large water

production. Reinjection could also cause degradation of the reservoir production quality and

productivity.

RECENT PRODUCED WATER TREATMENT DEVELOPMENTS

As there is still no economically practically method for disposal of all the produced water via re-

injection or various recycle methods, a range of innovative wastewater technologies have been

developed or are under development. The different technologies all have their operating

characteristics that make them suitable for only certain produced waters or operating

characteristics. There is a major focus on new technique to remove dissolved components from

produced water.

1SEPARATION BY FILTRATION

Utilization of membranes has been considered for treatment of oily wastewater to reduce

dissolved components. The new systems include the use of nano filtration membranes. However,

although the filtration method has very good separation effect, the high costs and complexity of

these treatment techniques means that applications are only experimental.

2 WATER TREATMENTS BY EXTRACTION

Another technology that has been widely tested on both pilot and full scale on the Norwegian

continental shelf is rooted in the solvent properties of supercritical liquids (CTour). The process

utilizes liquid condensate (NGL) from the gas scrubbers and injects it into the produced water

upstream of the hydro cyclones. The dispersed and dissolved hydrocarbons, which have higher

solubility in the condensate, go into the condensate phase and are separated in the hydro

cyclones. This equipment has undergone extensive pilot testing and its field tests are imminent.

The process is very sensitive to the available condensate quality.

3 ENHANCED OIL SEPARATIONS BY MEANS OF COALESCENCE

Several modern produced water treatment methods are based on the coalescing of dispersed oil

droplets, often prior to cyclonic separation. The devices are installed upstream of the cyclonic

vessels to increase oil droplet diameters which will result in better separation degree in the hydro

cyclones. The process of coalescence could be accelerated by different means. One method is to

install a special fiber media in the pipelining or the hydro cyclone vessels that attracts oil

droplets and promotes coalescence into larger aggregates. These systems have no effect on

removing dissolved hydrocarbons, but are simple and easily retrofitted. The fiber media is

sensitive to fouling and any abrasive elements (sand) in the water. Other processes include

combinations of chemical injection (coagulation/flocculation) and mechanical agitation in

specially built vessels. Compact flotation units are hybrid cyclone/degassers that could replace

standard degasser equipment.

4 METHODS BASED ON ADSORPTION

Adsorption has proven a successful area in maintaining compliance with produced water

discharges. Unfortunately most processes involve filters and therefore are restricted in volume or

require advanced regeneration processes which could be both energy demanding and expensive.

The adsorption techniques include activated carbon filters with regeneration by wet air oxidation

and oil-adsorbing media canisters based on resins, polymer and clay technologies

5THE NATURE TECHNOLOGY SOLUTIONS

Nature Technology Solution (Nature) provides state of the art treatment and management of

most kinds of contaminated wastewater. Nature is delivering services and equipment for efficient

handling of polluted wastewater from onshore, shipping and the offshore industry Nature offers a

range of physical, chemical and biological treatment methods for industrial wastewater.

THE NATURE PROCESS FOR PRODUCED WATER TREATMENT

The Nature process for treatment of produced water is based on addition of patented

coagulant/flocculants in existing or partially modified water systems. The agent is injected into

the produced water upstream a static mixer or various process equipment (pumps, valves etc.) to

provide sufficient in- mixing. The agent separates dispersed and dissolved hydrocarbons and is

floated and skimmed off in a flotation vessel downstream the in-mixing point.

THE NATURE PROCESS – Why Advantageous?

The Nature process combines coalescence and adsorption and significantly reduces dissolved

and dispersed hydrocarbons from produced water to less than 5 ppm. The Nature process utilizes

documented non- hazardous agents for professional treatment of oily produced water.

Implementation of new process equipment is usually not needed. The Nature technology

provides excellent water handling at low capital and operating costs. Rapid processing time

promotes small, less heavy and more compact treatment facilities.

NATURE EXPERIENCE WITH PRODUCED WATER

Nature technology has achieved good results in separating both polar (dissolved) and non-polar

(OIW) hydrocarbons from several produced water types from the Norwegian continental shelf.

Produced water from the Shell operated Draugen installation was treated with Nature coagulant

in the spring 2002. The OIW concentration was 93 ppm before treatment with nature coagulant.

Three different doses were used during fixed in- mixing and flocculation time of 150 and 120

seconds respectively. Draugen salinity was measured to < 3.4 %. Produced water temperature

was 50 °C. Figure 7 presents reduction of OIW following treatment with three different doses

Nature coagulant CF – 200 (dry The produced water temperature and salinity was 80 °C and 3,6

% respectively. The OIW concentration in the Statfjord C produced water was 19 ppm before

treatment with Nature coagulant. Three different doses of Nature coagulant CF – 200 (dry solid)

were added to the water. Four tests were performed on disposal well water at 50 °C. In- mixing

and flocculation periods were set to 60 and 120 seconds respectively. The water sample from the

disposal pit had such low oil in water concentration (2 ppm) that further testing was cancelled.

The salinity in the Kuwait produced water was quite high, measured to 10 % salt concentration.

C. SLUGE

Crude oil is a major source of energy and feedstock for petrochemicals. Oily sludge, bio-sludge

and chemical sludge are the major sludge generated from the processed sand effluent treatment

plants of the refineries engaged in crude oil refining operations. Refineries in India generate

about 28,220tons of sludge per annum. Various types of pollutants like phenols, heavy metals,

etc. are present in the sludge and they are treated as hazardous waste. Oily sludge, which is

generated in much higher amount compared to other sludge, contains phenol (90-100 mg/kg),

nickel (17-25 mg/kg), chromium (27-80 mg/kg), zinc (7-80 mg/kg), manganese (19-24 mg/kg),

cadmium (0.8-2 mg/kg), copper (32-120 mg/kg) and lead (0.001-0.12 mg/kg). Uncontrolled

disposal practices of sludge in India cause degradation of environmental and depreciation of

aesthetic quality. Environmental impact due to improper sludge management has also been

identified. Salient features of various treatment and disposal practices have been discussed.

Findings of a case study undertaken by the authors for Numaligarh Refinery in India have been

presented. Various system alternatives have been identified for waste management in

Numaligarh Refinery. A ranking exercise has been carried out to evaluate the alternatives and

select the appropriate one. A detailed design of the selected waste management system has been

presented. Sludge generation and management. The major sludge generated from the refineries is

oily sludge, bio sludge and chemical sludge. Sources of sludge generation in refineries have been

depicted in Fig. 2. Oily sludge is usually generated during cleaning operations of crude oil tanks.

In Indian refineries, tanks are usually cleaned once in 4 to 5 years. Oily sludge is also generated

when oily wastewater is treated in an American Petroleum.(1) Biological sludge is usually

generated during biological treatment of waste water. It is obtained from trickling filter and

clarifier unit. Solutions of sodium hydroxide are used primarily to wash the hydrocarbon

products in order to remove dissolved sulphides, mercaptans, phenolic and other acidic

compounds. (2) Chemical sludge is generated during the treatment of caustic treated effluent

with ferric chloride and polyelectrolyte. The quantity of sludge generation depends on various

factors, for example the characteristics of crude oil, effluent and sludge treatment process

involved, etc. The total quantity of sludge generated in Indian refineries is about 28,220

tons/year. In order to meet the growing demands for petroleum products, most of the refineries

are being expanded and new refineries are being set up. The total capacities of the plant after

expansion and future sludge generation scenarios have been depicted. In the refineries in India

oily sludge from wastewater treatment plant is usually stored in lagoons. Oily sludge from the

crude oil tank and the dried sludges from lagoons are disposed of in low-lying areas. A sludge

treatment facility is available in a few refineries. Centrifuge and vacuum filters are used in these

refineries for dewatering and volume reduction of sludge. Bio-sludge and chemical sludge are

usually stored in drying beds. The drying beds in the refineries are provided with filter medium

like sands, gravels, etc. Dried bio sludge is often applied on agricultural land and gardens in

order to exploit its manure potential. However, presence of heavy metals in the sludge is a major

constraint for its safe use as manure.

Environmental impact of disposal activities

The majority of the lagoons of refineries in India are lined with cement and bricks, and a few are

unlined. It has been observed that cracks developed in these lagoons which make a pathway for

the leach to enter the ground water aquifer and thus ground water is contaminated. In lagoons,

disposal of sludge create problems of odour and fire hazard. Uncontrolled disposal of oily sludge

from the tank and dried sludge from the lagoon on land also causes serious environmental

pollution. Leachate contaminated with the pollutants migrates through subsoil strata and pollutes

the ground water. The locations of landfill sites of Indian refineries have mostly been selected

according to availability of land and convenience rather than consideration of the hydro

geological features of the sites. Moreover, the majority of the refineries are located in coastal

areas where the ground water table is high. The sandy soils in these regions promote rapid

infiltration of leachate.

TREATMENT AND DISPOSAL; The salient features of various treatment and disposal

options for refinery sludges and their applicability.

SLUDGE DISPOSAL IN LAGOON/PIT

Containment of oily sludges in a lagoon is one of the commonly used methods for

storage/disposal of sludges. The lagoons are usually lined with bricks and cement. In Kuwait,

sludges are disposed of in the pits located within desert areas (Einawawy Amins et al. 1987).

Lagoons are used as storage places for sludges and cannot provide long term solutions for the

ultimate disposal of sludges. Moreover, lagooning of refinery sludge is not an environmentally

friendly solution to the disposal problem.

INCINERATION OF OILY SLUDGE

Incineration is the process of complete combustion of wastes in the presence of excess air. Time,

temperature and turbulence are the major factors, which control the combustion process. A

significant reduction in the volume of waste is achieved during the incineration process. Though

incineration of sludges is practiced in a few developed countries, it is not popular due to the

following reasons: (1) Fugitive and stack emissions from incineration and products of incomplete

combustion cause environmental pollution. (2) Incineration is the treatment process only and

landfill facilities are still needed for the final disposal of ashes. (3) Ashes resulting from the

incineration process contain heavy metals and need to be disposed of in an environmentally

friendly manner. (4) Commercial incinerators which are available in India are not designed for

the burning of oily sludge from refineries. Non-availability of incinerators appropriate for the

burning of refinery sludge and the emission of polluting gases are the major constraints in

adopting incineration for disposal of refinery sludges in India.

LAND FARMING

Land farming involves the application of wastes in controlled quantities to the land, followed by

application of fertilizer and regular planting of crops. This method depends mainly on the natural

in-situ biological decomposition of hydrocarbons by the vast and varied population of micro

flora in natural soils associated with photo-degradation. The structure of the soil and humus

content are the major factors in the process of hydrocarbon decomposition as they influence oil

and water retention, type and population of microflora and the rate of oxygen transfer. This

method is widely practiced, particularly in North America (Arora et al. 1982) where it is

successfully implemented in a wide range of soil types and climatic conditions. Land farming

has also been tried on an experimental basis in Kuwait (Einawawy Amins et al. 1987) and India.

In India, oily sludge has been applied at the rate of 5-10 kg/m2 on soil of silty clay category to

produce crops burseem & mellet (Gujrat Refinery, 1991). However, the feasibility of this

technique for large-scale application in India is yet to be established. Various environmental

issues such as the presence of oily odour during initial spreading, groundwater pollution due to

migration of leachate contaminated with hydrocarbons, phenols and heavy metals and health

problems associated with the contact of oily sludge need detailed investigations before any large-

scale application.

SECURE LANDFILL OF SLUDGES

In secure landfill techniques, the isolation from air and water is achieved through the use of thick

layers of impermeable clay and synthetic liner. When landfill is completed, it is capped with

layers of clay, flexible membrane liners and soil for vegetation. The top is contoured to prevent

ponding of rainwater on the surface and the vegetated contoured clay cover prevents water

intrusion into the completed landfill. The secure landfill system also employs a leachate

collection system above the bottom liner as a safeguard. Secure landfill is popular in developed

countries such as the USA, UK, Canada, Germany, etc. After dewatering, the sludges are

disposed of by secure landfill technique. Environmental problems encountered during land

disposal have been solved to a large extent by the introduction of secure landfill technique.

ACTIVATED SLUDGE TREATMENT WITH POWDERED ACTIVATED CARBON

(PACT®

The PACT® (Powdered Activated Carbon Treatment) system is similar to the conventional

activated sludge system described above. In this treatment system both biological oxidation and

carbon absorption occur simultaneously, thus enhancing the removal of contaminants in the

wastewater. Most of the powdered activated carbon is recycled with the activated sludge, but the

system requires a continuous makeup of fresh carbon. PACT® systems are generally used for

refinery wastewater in those cases where stringent standards need to be met for certain

contaminants.

SEQUENCING BATCH REACTOR

A sequencing batch reactor (SBR) is a fill-and-draw semi-batch biological treatment alternative

that employs aeration, sedimentation and clarification in a single reactor. The unit processes of

aeration and sedimentation are common to both the SBR and activated sludge systems. In

activated sludge systems the unit operations take place in different basins, while in the SBR the

operations take place in a sequential order in a common basin. Although still practiced in some

refineries, SBR technology is increasingly uncommon and has limited application in refinery

wastewater treatment. The various steps of operation are described below: ● Fill: During the fill

operation, wastewater with the substrate is added to the reactor. The aeration system is not

operated as the reactor is charged with wastewater from the equalization tank. ● React: During

this step, wastewater is aerated in the same way as in the activated sludge system. Biological

activity is initiated in this cycle of operation. ● Settle: In this step, aeration is terminated and

MLSS is allowed to settle. The settling is accomplished under quiescent conditions; no flow

enters, or is withdrawn from the reactor during the settle period. ● Decant: During the decant

period, clarified or treated supernatant effluent is withdrawn from the upper portion of the

reactor. The sludge blanket at the bottom of the reactor is maintained so that it is available as

seed sludge for the next cycle. ● Idle: This is not a necessary step and is usually omitted for the

refinery wastewater treatment system. The idle period is the time between the draw and the fill; it

could be zero or could be days. Generally, it is used in multi-tank systems, thereby providing

time to one reactor to complete its fill phase before switching to another unit.

MEMBRANE BIOREACTOR TECHNOLOGY

Membrane bioreactors (MBRs) are suspended growth biological treatment processes and are a

variation on the activated sludge system. A membrane bioreactor combines a membrane process

(e.g .microfiltration) with a suspended growth bioreactor, thereby eliminating the secondary

clarification used in an activated sludge system. A schematic of a typical MBR system is

D. CEMENTING WASTE

Used for a number of different reasons, cementing protects and seals the wellbore. Most

commonly, cementing is used to permanently shut off water penetration into the well. Part of the

completion process of a prospective production well, cementing can be used to seal the annulus

after a casing string has been run in a wellbore. Additionally, cementing is used to seal a lost

circulation zone, or an area where there is a reduction or absence of flow within the well. In

directional drilling, cementing is used to plug an existing well, in order to run a directional well

from that point. Also, cementing is used to plug a well to abandon it. Cementing is performed

when the cement slurry is deployed into the well via pumps, displacing the drilling fluids still

located within the well, and replacing them with cement. The cement slurry flows to the bottom

of the wellbore through the casing, which will eventually be the pipe through which the

hydrocarbons flow to the surface. From there it fills in the space between the casing and the

actual wellbore, and hardens. This creates a seal so that outside materials cannot enter the well

flow, as well as permanently positions the casing in place. Additives can be include accelerators,

which shorten the setting time required for the cement, as well as retarders, which do the

opposite and make the cement setting time longer. In order to decrease or increase the density of

the cement, lightweight and heavyweight additives are added. Additives can be added to

transform the compressive strength of the cement, as well as flow properties and dehydration

rates. Extenders can be used to expand the cement in an effort to reduce the cost of cementing,

and antifoam additives can be added to prevent foaming within the well. In order to plug lost

circulation zones, bridging materials are added, as well.

Cementing the Well; After casing, or steel pipe, is run into the well, an L-shaped cementing head

is fixed to the top of the wellhead to receive the slurry from the pumps. Two wiper plugs, or

cementing plugs, that sweep the inside of the casing and prevent mixing: the bottom plug and the

top plug. Keeping the drilling fluids from mixing with the cement slurry, the bottom plug is

introduced into the well, and cement slurry is pumped into the well behind it. The bottom plug is

then caught just above the bottom of the wellbore by the float collar, which functions as a one-

way valve allowing the cement slurry to enter the well.

Then the pressure on the cement being pumped into the well is increased until a diaphragm is

broken within the bottom plug, permitting the slurry to flow through it and up the outside of the

casing string.

Bottom and Top Plugs

After the proper volume of cement is pumped into the well, a top plug is pumped into the casing

pushing the remaining slurry through the bottom plug. Once the top plug reaches the bottom

plug, the pumps are turned off, and the cement is allowed to set. The amount of time it takes

cement to harden is called thickening time or pump ability time. For setting wells at deep depths,

under high temperature or pressure, as well as in corrosive environments, special cements can be

employed.

SOURCES OF CONTAMINATION

The main source of this contamination is the drilling of green.

cement or adoption of poor placement procedures.

DIAGNOSIS; Cement contamination will result in:

increased pH

an increase in Pf and calcium

 

a large increase in Pm.

TREATMENT

Prior to drilling cement, pre-treat the mud with 0.5-1.0 lb/bbl

of sodium bicarbonate.

If this is insufficient, treat cement contamination at the rate

of  0.15 lb/bbl sodium bicarbonate per 100 ppm calcium

(determine calcium using procedure below)

If sodium bicarbonate treatment levels are based on filtrate calcium

only, an incorrect treatment level will be obtained.  This is because

the majority of the cement will stay in suspension rather than go into

solution due to the high pH.

To obtain the total calcium level, the following procedure is

recommended:

1. Add 90 cm3 distilled water to 10 cm3 mud.

2. Titrate with 0.1 NH2S04 to a pH of 7.5 - 8.0.

3. Continue mixing for two minutes to ensure no pH rise.

4. Filter the slurry on the standard filter press.

5. Titrate 10 cm3 of filtrate with standard Versenate (001 molar).

Calcium = mls versenate x 4000

Note:

1. When large quantities of cement are drilled it may not be

economical to treat out the contamination due to the large

concentrations of bicarbonate required. In this case, the best

course of action may be to change out the contaminated mud

for new mud or drill cement with sea water if available.

2. When drilling cement, the rig crew shall be aware of the

possibility of plugged/blinded screens.

3. Onshore operations tend to drill cement with well water and

or mud and dump the contaminated mud. 

E. PAINTING WASTE: If you conduct spray painting operations, a hazardous waste

determination must be made on waste paint, solvents/thinners, paint sludge, primer waste, and

spray booth filters. The paints and paint sludges may be hazardous if they contain heavy metals,

such as arsenic, lead and chromium. The solvents may be characteristically hazardous due to

their ignitability or they could be a listed hazardous waste. Also, many primers, lacquers, and

enamels are flammable. Furthermore, during spray painting operations, volatile organic

compounds and hazardous air pollutants are released into the environment. These pollutants are

regulated under the Clean Air Act. Below you will find resources to help owners and operators

of auto repair shops understand and comply with federal, state, and local regulations concerning

painting operations as well as "green" practices to reduce your wastes and emissions from spray

paint.

F. CRUDE OIL RADIOACTIVE TRACERS WASTE; Are used in the oil industry in order to

qualitatively or quantitatively gauge how fluid flows through the reservoir, as well as being a

useful tool for estimating residual oil saturation. Tracers can be used in either interwell tests or

single well tests. In interwell tests, the tracer is injected at one well along with the carrier fluid

(water in a waterflood or gas in a gas flood) and detected at a producing well after some period

of time, which can be anything from days to years. In single well tests, tracer is injected into the

formation from a well and then produced out the same well. The delay between a tracer that does

not react with the formation (a conservative tracer) and one that does (a partitioning tracer) will

give an indication of residual oil saturation, a piece of information that is difficult to acquire by

other means. Tracers can be radioactive or chemical, gas or liquid and have been used

extensively in the oil industry and hydrology for decades.

G. DRILLING FLUID (DRILL MUD): Drill mud (also called cutting mud) is a complex

colloidal mixture of water, bentonitic clays, chemical additives, and trace amounts of oil from

cuttings of the hydrocarbon-bearing zones. This mud serves several purposes in oil drilling as it

is circulated down the inside of the rotating drill from the surface and backup the annular space

between the drill pipe and the drilled hole. At the drill bit/rock interface, it cools and lubricates

the cutting action. As it flows up the annular space, it lifts rock chips which can then be screened

out at the surface. Most important, the column of mud creates hydrostatic pressure which keeps

pressurized oil or gas from being expelled uncontrollably (a “blowout”).Much of this drill mud is

recycled, but after repeated use it picks up fine rock particles and water soluble subsurface

minerals until it is no longer economically practical to recondition it. The colloidal mass can then

be separated from the water either by centrifugal processes or by simply allowing it to settle in a

pit. The remaining fluid is then disposed of by deep injection. Much progress has been made in

the last decade in the employment of low toxicity mud additives, which has enabled the EPA to

issue NPDES permits for offshore discharges of treated muds and cuttings.

One roundtable suggestion was to investigate lower toxicity components or better reconditioning

techniques. Several participants noted that more uniform drilling systems and chemical

formulations in a single oil field or petroleum province might lead to more cost effective

recycling of muds by avoiding the “customized” treatment required when multiple formulations

are used. Another suggestion was to investigate the recycling of used muds or cuttings into

masonry, tiles, bentonite caps for landfills, or other products.

Drill cutting: Drill cuttings are the pieces of rock and soil removed from the ground as a drill bit

cuts a hole for a well. Present technology for disposal of these cuttings is to bury them in a non-

leaching lined landfill which freezes and becomes incorporated into the permafrost on the

Alaskan North Slope. In at least one North Slope oil field, cuttings are ground using a ball mill.

The ground material is then slurried and injected into a permeable subsurface formation.

COMPOSITION OF DRILLING MUD: Water-based drilling mud most commonly consists of

bentonite clay (gel) with additives such as barium sulfate (barite), calcium carbonate (chalk) or

hematite. Various thickeners are used to influence the viscosity of the fluid, e.g. xanthan gum,

guar gum, glycol, carboxymethylcellulose, polyanionic cellulose (PAC), or starch. In turn,

deflocculants are used to reduce viscosity of clay-based muds; anionic polyelectrolytes (e.g.

acrylates, polyphosphates, lignosulfonates (Lig) or tannic acid derivates such as Quebracho)

are frequently used. Red mud was the name for a Quebracho-based mixture, named after the

color of the red tannic acid salts; it was commonly used in 1940s to 1950s, and then was made

obsolete when lignosulfonates became available. Other components are added to provide various

specific functional characteristics as listed above. Some other common additives include

lubricants, shale inhibitors, and fluid loss additives (to control loss of drilling fluids into

permeable formations). A weighting agent such as barite is added to increase the overall density

of the drilling fluid so that sufficient bottom hole pressure can be maintained thereby preventing

an unwanted (and often dangerous) influx of formation fluids.

HEALTH EFFECT ASSOCIATED WITH DRILLING FLUIDS CONTACT:

The risk of adverse health effects from drilling fluids is determined by the hazardous components

of the fluids, additives and by human exposure to those components.

Skin irritation and contact dermatitis are the most common health effects observed from drilling

fluids exposure in human beings, with headache, nausea, eye irritation, and coughing seen less

frequently. The effects are caused by the physico-chemical properties of the drilling fluid as well

as the inherent properties of drilling fluid additives, and are dependent on the route of exposure

such as dermal, inhalation, oral and others.

INHALATION EXPOSURE:

The potential chemical changes in drilling during use and recycling can result in more toxic

substance being released. Since drilling fluids are subjected to elevated temperatures and

increased pressures, there has been a concern that organic components might break down, or

chemical reactions might occur, to form more toxic substances. There was a particular concern

that base oil high in aromatics might contain, or form Polycyclic Aromatic Hydrocarbons

(PAHs), while muds (drilling fluids) based on alkyl benzenes might break down to yield free

benzene. OGP and IPIECA (2009) also reported that drilling fluids are often circulated in an

open system at elevated temperatures with agitation that can result in a combination of vapours,

aerosol and/or dust above the mud pit. In the case of water-based fluids the vapours comprise

steam and dissolved additives. In the case of non-aqueous drilling fluids the vapours can consist

of the low boiling-point fraction of hydrocarbons (paraffin, olefins, naphthenes and aromatics),

and the mist contain droplets of the hydrocarbon fraction used. This hydrocarbon fraction may

contain additives, sulphur, mono-aromatics and/or polycyclic aromatics. It should be noted that

although the hydrocarbon fraction may contain negligible amounts of known hazardous

constituents such as Benzene, toluene, ethylbenzene and xylenes (BTEX) at low boiling point,

these will evaporate at relatively higher rates potentially resulting in higher concentrations in the

vapour phase than anticipated. McDougal et al. (2000), also reported that petroleum distillates

such crude oil, diesel oil (Group I-Non Aqueous Fluids) have been associated with renal, hepatic,

neurologic, immunologic, and pulmonary toxicity when they are inhaled or ingested. They are

also irritating to the skin and mucus membrane. ATSDR (1999a) reported some health effects

associated with inhalation exposure as: Neurological effects, Carcinogenicity, Haematological

effect, Immunological effect, Lymphoreticular effects and pulmonary effects

DERMAL EXPOSURE: Most chemicals are readily absorbed through the skin and can cause

other health effects and/or contribute to the dose absorbed by inhalation of the chemical from the

air. When drilling fluids are circulated in an open system with agitation, there is a high likelihood

of dermal exposure resulting in dermatitis and skin irritation. The potential dermal exposure is

not limited to the hands and forearms, but extends to all parts of the body. Actual exposure

depends on the drilling fluid system and the use of Personal Protection Equipment (PPE). Many

studies indicate that absorption of chemicals through the skin can occur without being noticed by

the worker. In many cases, skin is a more significant route of exposure than the lung (OSHA,

2009).

DERMATITIS AND IRRITATION: Skin contact with drilling fluids or mud can also cause

inflammation of the skin, referred to as dermatitis. Signs and symptoms of dermatitis can include

itching, redness, swelling, blisters, scaling, and other changes in the normal condition of the skin

(Fig. 5, Anonymous, 2009). On the drill floor, in particular, skin contamination can be broad, but

occasionally dermatitis also occurs in divers who make contact with discarded cuttings on the sea

bed (Ormerod et al., 1998). Petroleum hydrocarbons will remove natural fat from the skin, which

results in drying and cracking. These conditions allow compounds to permeate through the skin

leading to skin irritation and dermatitis. Some individuals may be especially susceptibility to

these effects. Skin Fig. 5: Dermatitis of the hands irritation can be petroleum hydrocarbons,

specifically with aromatics and C8-C14 paraffins. Petroleum streams containing these

compounds, such as kerosene and diesel (gas oil), are clearly irritating to skin. This is suggested

to become malignant caused by the paraffins, which do not readily penetrate the skin but are

absorbed into the skin, hereby causing irritation (McDougal et al., 2000). Linear alpha olefins

and esters commonly used in drilling fluids are only slightly irritating to skin, whereas linear

internal olefins are not irritating to skin. In addition to the irritancy of the drilling fluid

hydrocarbon constituents, several drilling fluid additives may have irritants, corrosive or

sensitizing properties (Cauchi, 2004). For example calcium chloride has irritant properties and

zinc bromide is corrosive whereas a polyamine emulsifier has been associated with sensitizing

properties. Although water based fluids are not based on hydrocarbons, the additives in the fluid

may still cause irritation or dermatitis. Excessive exposure under conditions of poor personal

hygiene may lead to oil acne and folliculitis (OGP and IPIECA, 2009). ATSDR (1997)

concluded that it is reasonable to expect that adverse haematological and immunological effects

might occur following dermal exposure to benzene.

ORAL EXPOSURE: Oral exposure is negligible as compared to the other exposure routes such

dermal, inhalation and others. Oral exposure may occur when hands are not well washed before

they are used to handle thing like cigarette. Data for the oral route of exposure are less extensive.

The BTEXs cause neurological effects, generally central nervous system depression, by the oral

route. Renal and hepatic effects are also seen with oral exposure to these compounds. Renal

effects are the basis for the intermediate. The hepatic effects tend to be mild, including increased

liver weight an cytochromes.

Benzene causes haematological effects by the oral route that is similar to those seen from

inhalation exposure.

HIERARCHY OF PRINCIPLE OF CONTROL:

If hazardous components of drilling fluids are identified at each stage of any drilling operation or

areas where drilling fluids are likely to be exposed, together with a risk of exposure then, the

following hierarchy of principles of control should be considered: C Elimination (not feasible)

C Substitution (low toxic base oils, WBFs), C Engineering controls (greater enclosure)

C Administrative controls (rotate jobs, hygiene measures, education of Control of Substances

Hazardous to Health (COSHH), skin management systems and improved laundry practices)

C Personal protective equipment (chemical resistant slicker suit and gloves)

CHALLENGES IN SETTING DRILLING FLUID EXPOSURE STANDARDS:

The health exposure standard of drilling fluid during oil and gas operations has always not be

given the same attention or concern as its effects and risk management guidelines due to the

following challenges:

C Drilling fluids are complex mixtures of variable composition, C It unclear about the longer

term of health effect, C There is no scientific basis on which to set health exposure limit

C Exposure must be made up of all pertinent fractions such aerosol, vapour, etc., and all

variation in composition, C Exposure should reflect the level that can be achieved using good

practices.

EXPOSURE INDICATORS: In spite of the challenges of setting health exposure standards of

drilling fluid exposure to oil and gas workers, Agency for Toxic Substances and Disease

Registry (ATSDR) has researched into the BTEXs which are released as a result of drilling fluids

during agitation under high pressures and temperature. The study presents these findings by

ATSDR as an Exposure Indicator or Lowest Observed Adverse Effect Level (LOAEL) for

drilling fluid exposure to operators to help reduce the dangers of abnormal drilling fluids

exposure.

TREATMENT OF DRILLING FLUIDS AND DRILLING MUD: Contaminated drilling fluids

and mud are a considerable potential hazard to the sensitive marine ecosystem. The appropriate

process treats the contaminated fluids and muds sufficiently so that by the end of the process,

purified and thus unpolluted water can be discharged into the environment. This task is

performed by the high-speed decanters and clarifiers from GEA Westfalia Separator. Drilling

fluids are understood to be viscous emulsions which are circulated through the drilling pipe

during drilling for crude oil in order to pump the milled product upwards at the same time as the

oil. These emulsions rapidly become contaminated with mud, salt water and oil residues. This

means that the drilling fluids have to be continuously cleaned to ensure a smooth drilling

process. The contaminated fluids are also a hazard to the sea; however, so continuous treatment

is all the more important. Once the drilling fluids have passed through a coarse screen and had a

flocculant and a flush liquid added, the coarser solids are separated off by a decanter of the

appropriate output. The liquid phase is initially passed to a slop oil tank. A clarifier from GEA

Westfalia Separator then separates the fine residual solids so that the liquid phase can be

discharged into the environment in the form of pure water after passing through a protective

filter. This complies with the “zero emission” philosophy in an exemplary manner.

Treatment of drilling fluids

To treat drilling mud rich in solids, GEA Westfalia Separator has also developed special high-

speed decanters which, in the form of the Westfalia Separator   cdforce generation, work

efficiently on drilling platforms and FPSOs.

THE ELECTROCHEMICAL METHOD OF DRILLING MUD TREATMENT.

The electrochemical methods of and devices for drilling mud treatment, which became

the basis for electrochemical activation technology, had been over. Drilling mud is a

complex poly-disperse system containing clayey mineral particles in water with added

organic substances - stabilizers, structure forming agents, thinners and fluid loss

additives. The main technological function of drilling mud is bringing drill cuttings

from the well bottom to the surface. Clayey particles in drilling mud are normally

negatively charged, the charge density depending on surface configuration and

chemical composition of clayey particle crystal lattice, as well as on chemical

composition and electrolyte content of the liquid phase of drilling mud. Passing current

through drilling mud commonly results in deposition on the anode of firm clayey crust

made up of the most fine-disperse and highly-charged clayey particles. This crust

prevents products of anode electrochemical reactions from entering the drilling mud,

therefore the solution’s рН value increases due to cathode, actually unipolar,

electrochemical treatment. It was found that in conditions of the same consumed

quantity of specific power, the smaller the cathode area as compared to the anode one,

the stronger thixotropic properties of drilling mud (structural-mechanic strength) with

simultaneously lower dynamic viscosity (paradox). The paradox can be explained in

the following way: electric charges accumulated on the edges and pointed parts of tiny

scales or needle-like particles of argillaceous minerals are several times stronger than

the charges on their flat facets. Under the influence of electrochemical treatment, in a

high voltage electric field close to the cathode surface (in the area of spatial charge),

there increased absolute value of particles’ negative charge, thus enhancing their

repulsion forces and therefore lowering viscosity. At the same time, however,

difference of potentials between the edges and facets of argillaceous particles also

increased, causing growth of forces putting in good order structural arrangement of

interacting clayey particles. So, drilling mud’s structural and mechanical properties

improved due not to mechanical, but to electrostatic adhesion of clayey particles.

Electrochemical and chemical regulation methods, and attempt practical application of

the discovered effect in the process of oil and gas well drilling. The reported effect had

not been known before; therefore the process of unipolar cathode electrochemical

treatment of drilling mud was first called by V.M. Bakhir low-voltage polarization, and

three years later –electrochemical activation. The above-indicated first invention

established a non-chemical method to improve drilling mud parameters by treatment in

an engineering electrochemical system consisting of a current power supply and two

electrodes, the cathode surface area being smaller than the anode one. In this

electrochemical system, the surfaces of drilling rig circulation system coming into

contact with drilling mud actually performed the function of anode. Practical trials

proved the method’s high efficiency, which allowed saving up to 30 % of chemical

reagents commonly used for a well drilling. However, the method had a significant

disadvantage, that is, the necessity to periodically remove clayey crust from anode

surface and laboriousness of this procedure.

H. SCALES

The oil and gas TENORM-contamination arises in the piping, pumps, valves and tanks used in

the drilling and oil-extraction processes due to so-called scale which is mainly a precipitation

containing radioactivity. The radioactivity in the scale is dominated by radium and its daughter

nuclides. The origin of the radioactivity is of course the natural occurrence of uranium and

thorium in the bedrock.

Scale formed in the oil and gas industry is, according to the literature [see for example 1], mainly

barium sulphate. Barium sulphate is a substance more or less famous for its very low solubility

product. Since radium is a chemical analogue to barium, radium will naturally accumulate in the

scale matrix of barium sulphate, which will then become radioactive and in need of treatment/

handling according to the local regulations.

Scale is often removed from piping with high-pressure water-jetting. This results in a slurry of

scale, water and some oil which can be radioactive or not. The piping from which the scale is

removed are often slightly contaminated as well, due to cracks and corrosion on the pipe walls.

In other parts of the North Sea the radium is not the main contamination. In parts where gas is

extracted Po-210 and Pb-210 is the most important contaminant due to the decay of radon in the

gas.

Scale is composed primarily of insoluble barium, calcium, and strontium compounds that

precipitate from the produced water due to changes in temperature and pressure. Radium is

chemically similar to these elements and as a result is incorporated into the scales.

Concentrations of Radium-226 (Ra-226) are generally higher than those of Ra-228.

Scales are normally found on the inside of piping and tubing. The API found that the highest

concentrations of radioactivity are in the scale in wellhead piping and in production piping near

the wellhead. Concentrations were as high as tens of thousands of picocuries per gram. However,

the largest volumes of scale occur in three areas:

(1) Water lines associated with separators, (separate gas from the oil and water)

(2) Heater treaters (divide the oil and water phases)

(3) Gas dehydrators, where scale deposits as thick as four inches may accumulate.

Chemical scale inhibitors may be applied to the piping complexes to prevent scales from slowing

the oil extraction process. If the scales contain TENORM, the radiation will remain in solution

and eventually be passed on to the produced waters. Approximately 100 tons of scales per oil

well are generated annually in the United States. As the oil in a reservoir dwindles and more

water is pumped out with the oil, the amount of scale increases. In some cases brine is introduced

into the formation to enhance recovery; this also increases scale formation. The average radium

concentration in scale has been estimated to be 480 pCi/g. It can be much higher (as high as

400,00s0 pCi/g) or lower depending on regional geology Petroleum pipe scale, consisting of

concentrated inorganic solids such as barium sulfate, can deposit on the inside of down-hole

pipes during the normal course of oil field pumping operations. A portion of this scale has been

shown to contain naturally occurring radioactive materials (NORM), predominantly compounds

of radium. When these pipes are removed from the well, there is a potential for radiation doses to

the oil field workers handling the pipes, especially as the pipes are cleaned for reuse. A thorough

sampling and measurement protocol was applied under a variety of weather conditions in an

outdoor laboratory to obtain an accurate indication of the radiological and aerodynamic

characteristics of scale release and dust dispersion during petroleum pipe scale removal from

out-of-service pipes with a restored, historically relevant outdoor pipe-cleaning machine.

Exposure rate data were also obtained for both the pre-cleaned pipes, and the general area

inhabited by workers during the descaling operation. Four radiation exposure pathways were

investigated: inhalation of pipe scale dust generated during pipe rattling, incidental ingestion of

the pipe scale dust, external exposure from uncleaned pipes, and external exposure from pipe

scale dispersed on the ground. Pipes from three oil fields were rattled to collect as much

industry-representative data as possible. The 226Ra specific activity of the pipe scale ranged from

33.6 ± 0.4 to 65.5 ± 0.7 Bq g-1, depending on the formation. A median atmospheric dust loading

of 0.13 mg m-3 was measured in the operator breathing zone. The respirable fraction was

observed to be about 42% to 46%. Based on cleaning 20 pipes per day,250 d per year on

average, annual committed effective doses for the operator and helper ranged from 0.11 mSv (11

mrem) to 0.45 mSv(45 mrem) for inhalation and from 19 μSv (1.9 mrem) to 97 μSv (9.7mrem)

for incidental ingestion. Worker annual external dose from the pipe racks ranged from 0 to 0.28

mSv (28 mrem). In the deposition experiment, more than 99% by weight of the deposited scale

fell within 2 m of the machine centerline, the vast majority of which was in the downwind

direction. The dose from this deposited material dominated the worker dose estimates. The

annual external dose from dispersed material was estimated to be 2.8 mSv (280 mrem) for the

operator and 4.1 mSv (410 mrem) for the helper.

HANDLING OF SCALE – A NEW APPROACH

Based on the experience from waste treatment for the nuclear industry and with the same

approach, development of a method for treatment of radioactive material from the oil and gas

industry was started. The aim was to minimize the final waste volume and to produce a waste,

which will not chemically or biologically degrade over long time and maybe produce chelates, as

in a final storage, or being contained in a non-solid matrix. The aim is supported by the intention

that the majority of other materials, for example steel from piping, after treatment which no

longer are classified as radioactive shall be recycled. There is also the intent of the method to

meet environmental demands as they are agreed upon today and also to meet demands that might

be more restrictive in the future. In the oil and gas industry today there are radioactive material

identified on several of the large oilfields [5-8 and references therein]. Depending on the

regulations and legislation the handling of the occurring TENORM material are very different

from site to site. From the above given prerequisites a process which can handle both the scale

and scrapped steel piping was designed. The procedure is divided into two parts, one for the

metal and one for the scale. Discalced and scrapped piping can be melted in order to simplify the

clearance procedure if the authorities or the industry demand it. The scale is treated in a separate

procedure in which the radioactive components are separated from the non-radioactive

components. This means that the amount of radioactive waste that need handling and disposal is

minimised, and therefore also the costs. The procedure also ensures that the waste is dry, not

biodegradable or contains any chelates, which is essential for the repository, especially if the

repository is in contact with water. The process is yet in its development stage but so far a

volume reduction factor of at least 20 is reasonable. This means that the amount of waste after

treatment is only 5 % of the original volume.

H METALS SCRAPS

Treating low-level scrap metals from the nuclear industry. The aim for the treatment is to release

the metals from regulatory control and to recycle the metals outside the nuclear industry.

Studsvik Rad Waste has a permit to store material for 20 years awaiting decay of the

radioactivity. At Studsvik all scrapped metal are melted in one of the induction furnaces. The

induction homogenizes the melt and one sample is representing the whole batch, 3.5 tonnes of

steel. This makes proving the activity content for clearance of the metal very easy. Since

uranium cannot be stored for decay and since there are metals contaminated with uranium that

can be re-used Studsvik RadWaste AB has, in the last few years, developed a method for

decontamination of steel from uranium during the melt process. This method can be used for

TENORM contaminated material as well. With these experiences a handling and clearance of

material from the oil and gas industry can be done according to regulations. Melting of these

materials in an induction furnace has the advantage that any radioactivity left in the metal is

homogeneously distributed. How this material will be released from regulatory control is under

implementation in many countries today and the outcome is to be seen.

I. PIGGING WASTE

What is the purpose of pigging? In order to protect these valuable investments, maintenance

must be done and pigging is one such maintenance tool. During the construction of the line, pigs

can be used to remove debris that accumulates. Testing the pipeline involves hydro-testing and

pigs are used to fill the line with water and subsequently to dewater the line after the successful

test. During operation, pigs can be used to remove liquid hold-up in the line, clean wax off the

pipe wall or apply corrosion inhibitors for example. They can work in conjunction with

chemicals to clean pipeline from various build-ups. Inspection pigs are used to assess the

remaining wall thickness and extent of corrosion in the line, thus providing timely information

for the operator regarding the safety and operability of the line. Pigs (or more specifically) plugs

can be used to isolate the pipeline during a repair. A pig is a device inserted into a pipeline which

travels freely through it, driven by the product flow to do a specific task within the pipeline.

These tasks fall into a number of different areas: (a) Utility pigs which perform a function such

as cleaning, separating products in-line or dewatering the line; (b) Inline inspection pigs which

are used to provide information on the condition of the pipeline and the extent and location of

any problem (such as corrosion for example) and (c) special duty pigs such as plugs for isolating

pipeline. The pipeline layout and features will dictate the geometry of the pig largely. The pig

must be long enough to span features such as wyes and tees yet must be short enough to

negotiate bends. Changes in internal line diameter will influence the design effort required for

the pig. In summary, the correct pig type is chosen for the task but then the pipeline design and

operating conditions will affect the actual design of the pig. The differences between offshore

and onshore pipelines and their intelligent pigging procedures. Offshore pipelines are of thicker wall

than onshore-sometimes up to 35mm thick. Offshore pipelines can have greater operating pressures,

particularly the deepwater pipelines offshore Angola, Brazil or Gulf of Mexico. Maximum operating

pressures onshore can be 100barg but offshore can be 300barg. Flow rates of products both onshore

and offshore are the same dependant upon the type of pipeline or its position with regard to

transporting product either between offshore platforms or from platform to shore.

A cleaning pig for a 6-inch oil pipeline. The wire brush encircles the shaft and scours the interior

of the pipeline. Pigging can be used for almost any section of the transfer process between, for

example, blending, storage or filling systems. Pigging systems are already installed in industries

handling products as diverse as lubricating oils, paints, chemicals, toiletries, cosmetics and

foodstuffs. Pigs are used in lube oil or painting blending: they are used to clean the pipes to avoid cross-

contamination, and to empty the pipes into the product tanks (or sometimes to send a component back

to its tank). Usually pigging is done at the beginning and at the end of each batch, but sometimes it is

done in the midst of a batch, e.g. when producing a premix that will be used as an intermediate

component.

ETYMOLOGY: The original pigs were made from straw wrapped in wire used for cleaning.

They made a squealing noise while traveling through the pipe, sounding to some like a pig

squealing, which gave pigs the name. (Disputed: 'PIG' is an acronym or backronym derived from

the initial letters of the term 'Pipeline Inspection Gauge.').

PIGGING IN PRODUCTION ENVIRONMENTS

A major advantage of piggable systems is the potential resulting product savings. At the end of

each product transfer, it is possible to clear out the entire line contents with the pig, either

forwards towards the receipt point, or backwards to the source tank. There is no requirement for

extensive line flushing. Without the need for line flushing, pigging offers the additional

advantage of a much more rapid and reliable product changeover. Product sampling at the receipt

point becomes faster because the interface between products is very clear, and the old method of

checking at intervals, until the product is on-specification, is considerably shortened.

ENVIRONMENTAL ISSUES

Pigging has a significant role to play in reducing the environmental impact of batch operations.

Traditionally, the only way that an operator of a batch process could ensure a product was

completely cleared from a line was to flush the line with a cleaning agent such as water or a

solvent or even the next product. This cleaning agent then had to be subjected to effluent

treatment or solvent recovery. If product was used to clear the line, the contaminated finished

product was downgraded or dumped. All of these problems can now be eliminated due to the

very precise interface produced by modern pigging systems.

SAFETY CONSIDERATIONS

Pigging systems are designed so that the pig is loaded into the launcher, which is pressured up to

launch the pig into the pipeline through a kicker line. In some cases, the pig is removed from the

pipeline via the receiver at the end of each run. All systems must allow for the receipt of pigs at

the launcher, as blockages in the pipeline may require the pigs to be pushed back to the launcher.

Most of the time, systems are designed to pig the pipeline in either direction. The pig is pushed

either with an inert gas or a liquid; if pushed by gas, some systems can be adapted in the gas inlet

in order to ensure pig's constant speed, whatever the pressure drop is. The pigs must be removed,

as many pigs are rented, pigs wear and must be replaced, and cleaning pigs push contaminants

from the pipeline such as wax, foreign objects, hydrates, etc., which must be removed from the

pipeline. There are inherent risks in opening the barrel to atmosphere and care must be taken to

ensure that the barrel is depressured prior to opening. If the barrel is not completely depressured,

the pig can be ejected from the barrel and operators have been severely injured when standing in

front of an open pig door. When the product is sour, the barrel should be evacuated to a flare

system where the sour gas is burnt. Operators should be wearing a self-contained breathing

apparatus when working on sour systems.

A pig on display in a section of cutaway pipe, from the Alaska Pipeline. Pipeline inspection

gauge or "PIG" in the pipeline industry is a tool that is sent down a pipeline and propelled by the

pressure of the product in the pipeline itself. There are four main uses for pigs:

1. Physical separation between different liquids being transported in pipelines;

2. Internal cleaning of pipelines;

3. Inspection of the condition of pipeline walls (also known as an Inline Inspection (ILI)

tool);

4. Capturing and recording geometric information relating to pipelines (e.g. size, position).

One kind of pig is a soft, bullet shaped polyurethane foam plug that is forced through pipelines to

separate products to reduce mixing. There are several types of pigs for cleaning. Some have

tungsten studs or abrasive wire mesh on the outside to cut rust, scale, or paraffin deposits off the

inside of the pipe. Others are plain plastic covered polyurethane. Inline inspection pigs use

various methods for inspecting a pipeline. A sizing pig uses one (or more) notched round metal

plates that are used as gauges. The notches allow different parts of the plate to bend when a bore

restriction is encountered. More complex systems exist for inspecting various aspects of the

pipeline. Intelligent pigs, also called smart pigs, are used to inspect the pipeline with sensors and

record the data for later analysis. These pigs use technologies such as MFL and ultrasonics to

inspect the pipeline. Intelligent pigs may also use calipers to measure the inside geometry of the

pipeline.

J. AIR EMISSON

The effects of the Nigerian oil industry on global climate change should also raise great concern.

Wasteful gas flaring - the burning of the gas released during oil production – results in enormous

levels of greenhouse gas emissions every year. According to Friends of the Earth Netherlands, in

the Niger Delta alone, these emissions are equivalent to the CO2 emissions of 4 million cars or

of 2 million European households. Gas flaring also causes health problems such as leukemia and

asthma. The acid rain caused by flaring also negatively affects food production. Nigeria is the

largest gas flarer in the world. Nigeria’s flaring is sometimes described as "environmental

racism" since this outdated, harmful and wasteful practice has already been terminated decades

ago in Northern, rich, and industrialized countries.

CRUDE OIL EXTRACTION

GHG emissions in the extraction phase are determined by the interactions of eight main

parameters:age of oil field, gas-to-oil ratio, reservoir depth, pressure, viscosity, American

Petroleum Institute (API) gravity (a measure of how “light” or “heavy” a crude is relative to

water), type of feedstock (e.g., tar sands, conventional crude), and development type [onshore,

offshore, surface mining, steam-assisted gravity drainage (SAGD)]. This study does not consider

coal-to-liquid and gas-to-liquid methods or oil shale.

The ratio of the volume of gas in solution to the volume of crude oil at standard conditions is the

gas-to-oil ratio (GOR). Higher values of GOR lead to higher production of natural gas. The gas

produced can be used in extraction for meeting onsite energy needs, exported, and/or flared and

vented. If it is flared and vented, it can substantially increase life-cycle GHG emissions. A high

GOR can also correspond to production of substantial amounts of oil condensates. The age of an

oil field influences GHG emissions because as fields mature, oil production declines; energy

intensive techniques such as water or gas injection must then be used to extend production levels,

resulting in increased GHG emissions. Heavier crude oils (low API gravity) require more energy

to extract, transport, and refine. Crude oils with higher viscosity require more energy for

pumping. Reservoir depth and pressure also affect energy use in extraction. With a decrease in

depth, friction losses increase in the drill pipe. As fields mature, the initial pressures tend to

decline in the absence of intervention. Maintenance techniques such as water injection are

required to maintain the initial pressure. These pumping or compression techniques involve

pumping fluids back into the reservoir to extract crude oil. If the initial reservoir pressure is high,

the energy required for maintaining the pressure will also be high. Different amounts of energy

are required to extract and upgrade crude oil from different types of feedstock. Tar sands and

conventional oil require completely different extraction technologies. Among tar sands,

differences exist between surface mining and in situ methods such as SAGD, resulting in

different GHG emissions. In addition, the type of oil field development [onshore/offshore,

surface mining, thermally enhanced oil recovery (TEOR), etc.] determines the infrastructure

required. Differences in infrastructure also influence energy requirements affecting GHG

emissions during extraction of crude oil. For example, TEOR requires more energy than any

other conventional form of offshore or onshore crude oil extraction. Note as the age of an oil

field influences GHG emissions because as fields mature, oil production declines; energy-

intensive techniques such as water or gas injection must then be used to extend production levels.

FLARING AND VENTING: Flaring and venting are an important source of GHG emissions

from oil fields. When crude oil is extracted, gas dissolved in crude oil is released, which can be

used for meeting energy needs in extraction, captured and sold as product, or flared and vented.

Flaring refers to disposal of associated gas produced during extraction through burning. Venting

refers to intentional releases of gas and the release of uncombusted gas in flaring (the

combustion efficiency of flaring is not 100%, so some methane is left in the exhaust gas). In this

study, the volume of gas flared is derived from GOR, energy use in the field, and the quantity of

gas exported. Satellite data (e.g., from NOAA) and country-level emission factors [Global Gas

Flaring Reduction (GGFR); World Bank, n.d.] were also used. Besides the volume of gas flared,

gas specifications are important in determining GHG emissions from flaring. In general, gas with

higher energy content per unit volume produces more GHG emissions when flared. One can be

reasonably confident about which oil fields are flaring and which are not from satellite data and

the lack or presence of infrastructure. However, uncertainties exist with regard to the volumes of

gas.

FUGITIVE EMISSIONS: Fugitive emissions represent unintentional or uncontrollable releases

of gas—for example, from valves and mechanical seals. It is difficult to measure fugitive

emissions. The usual practice is to base such measurements on emission factors suggested by the

Canadian Association of Petroleum Producers (CAPP), the U.S. Environmental Protection

Agency (EPA), and the International Association of Oil and Gas Producers (OGP). In this study,

fugitive emissions were determined on the basis of CAPP emission factors (CAPP, 2003) for

equipment fittings such as seals, valves, and flanges. The use of such emission factors can result

in significant errors. The alternative is to use leak detection methods, such as acoustic sensors

and hyperspectral imaging, and optical methods such as tunable diode laser absorption

spectroscopy and laser-induced fluorescence. The costs of monitoring and verification using

these techniques can be high.

TRANSPORT

GHG emissions from crude oil transport to a refinery are a function of distance, API gravity, and

mode of transport. API data were taken from PennWell. Distances between oil fields and

refineries were determined using Port World. Emission factors for a given mode of transport

were taken from GREET (Wang, 2010).

REFINING

GHG emissions from refining are a function of API gravity, sulfur content, and type of refinery.

In general, heavy crudes (low API gravity) require more energy to process than light crudes. In

this study, we applied the relationship devised by Keesom, Unnasch, and Moretta (2009),

calibrated to European refineries, to estimate GHG emissions. The relationship between API

gravity and energy consumption is not linear for API gravities above 45. GHG emissions also

vary from one refinery type to another depending on the level of complexity and type of refined

products produced. As a simplification, this study assumes that crude oils are refined in a

notional refinery where GHG emissions are determined entirely by API gravity. The impact of

sulfur content was not considered in this study.

UNCERTAINTIES IN THE ASSESSMENT

There are uncertainties involved in undertaking a carbon intensity assessment such as this. For

instance, some of the most important emissions sources, such as flaring and fugitive emissions,

are not fully monitored by oil companies, and where they are, the data may not be publicly

available. Even where gas flaring and fugitive emissions are monitored, the measurement tools

currently available are subject to a degree of inaccuracy determined by the physical

characteristics of the measurement system. Flare efficiency may also be subject to factors beyond

the control of oil companies, such as local wind conditions. To test the robustness of the results,

we undertook a sensitivity analysis in which key input parameters were varied for three typical

cases (low-, medium-, and high-intensity fields). Emissions from high-intensity fields that flare

are inevitably sensitive to the parameters that determine flaring emissions. For example, when

we used the Canadian model of a default flaring value instead of estimating flaring on the basis

of data about the oil fields, the intensity of the high-intensity case was reduced by nearly 30%.

Varying other parameters resulted in changes of less than 10%.

K. TANK BOTTOMS AND HEAVY HYDROCARBONS

Tank bottoms are defined by the API as basic sediment with water and other materials that

collect in the bottom of treatment and storage vessels, such as production separators fluids

treating vessels, and production impoundments. Tank bottoms can contain hydrocarbons, heavy

metals, sands, emulsions and other solids, which can affect human health and environment. The

API considers tankbottoms to be in the same category as pit sludge’s, paraffin’s and pigging

wastes generated in gathering lines and finds that the primary environmental consideration when

managing these types of waste by maximizing hydrocarbons recovery. There are a number of

innovative reclamation processes, which can be utilized either on or off-site to facilitate

hydrocarbons recovery. Prior to recycling, reclamation and /or disposal, these wastes should be

managed in tank or lined pits or in lined diked piles properly to protect vegetations and surface

waters. Tank bottoms contain heavy metals; hydrocarbons and other solids so before disposed on

off site, it should be checked for flash point, leach able heavy metals content and density and

compared with the results of the road mix oil. There may be permits or other authorization

required from state agencies before road-spreading practices are allowed or sell to road

construction agencies.

TREAMENT

The volume of solids collected in storage tanks been minimized.

Tanks designed to reduce the volume of produced tank bottoms (for example, cone-

shaped bases)?

Gas blanket kept on tanks to reduce oxygen and formation of iron oxides.

Installation of return line to run bottoms through heat-treaters more frequently than

normal.

Have sources of solids been identified? If yes, have engineering or operations solutions

been attempted?

If oil is reclaimed onsite or sent to reputable reclaimer.

Are light oil tank bottoms treated in heavy oil dehydration facilities.

The tank bottoms sent to a refinery coker.

Centrifuge or filter press used to recover oil and water form tank bottoms.

Re-circulation pumps are added to product storage tanks to reduce the settling of heavy

hydrocarbons on tank bottoms.

L. WORKOVER AND COMPLETION WASTES.

Workover and completion wastes result from operations where an oil well’s head is partially

open to the atmosphere and is filled with a water base fluid that maintains pressure on the

formation to prevent blowout. Workover fluid is injected into such a well while the well’s

interior tubing string, valves, packer gaskets, or other components are undergoing maintenance.

When maintenance is complete, the workover fluid is removed from the well before starting

routine operation. Completion fluids are typically used in a well when the well casing is

perforated just before starting production. Both fluids become contaminated with oil and

formation brine. Standard practice for handling workover and completion wastes calls for

separating the oil from the fluid and recycling both the oil and the fluid by filtering and adding

more solute to make up for dilution by formation brine. Although the oil can easily be recycled,

after several uses the base fluid can no longer be brought back to specification. Unreclaimable

fluid is presently disposed of through subsurface injection, but better ways to recycle these fluids

are currently being investigated by industry researchers. One technique to minimize excess fluid

production is to use a continuous mix process, rather than a batch, producing only enough fluid

to fill a well. Selection of fluid components that simplify this process, such as hydrogen sulfide

scavengers, should encourage its use.

M. USED OR SPENT SOLVENTS: Solvents are used in tasks such as cleaning, degreasing, and

painting. Unused solvent intended for disposal is considered a waste.

TREATMENT

ON-SITE RECYCLING: On-site recycling is economical when approximately 8 gallons of

solvent waste is generated per day (Schwartz, 1986). The simplest form of solvent reuse is

termed “downgrading,” which is the use of a solvent that has become contaminated through

initial use for a second cleaning process. For example, precision bearings need very high purity

solvents for cleaning. The solvent acquires very little contamination in usage and can be

downgraded or used for less demanding cleaning operations. More effort is required to recycle

solvent that has become heavily contaminated and the possibilities for both on-site and off-site

recycling or reclamation need to be explored. In vapor degreasing and cold cleaning, the soil

removed accumulates in the equipment. Eventually the solvent becomes too contaminated for

further use and it must be reclaimed or disposed of via incineration. For on-site recycling, many

different separation technologies are available. Commonly used separation technologies for

contaminated solvents include gravity separation, filtration, bath distillation, fractional

distillation, evaporation, and fuel use.

GRAVITY SEPARATION

The use of settling to separate solids and water from solvent often permits the reuse of solvent.

For example, paint thinners may be reused many times if solids are allowed to settle out.

FILTRATION

Filters can be used to remove solids from many solvents thus extending solvent life.

BATCH DISTILLATION

A batch still vaporizes the used solvent and condenses the overhead vapors in a separate vessel.

Solids or high boiling residues (>4000F) remain in the still as a residue. Solvent stills range in

size from 5 gallon to 500 gallon capacity. A vapor degreaser can be used as a batch still for

recycling solvent. This is often done by employing proper boil-down procedures. Detailed

discussion of these procedures is available from major solvent suppliers. In many applications, it

is necessary to keep the water content of the recovered solvent to less than 100 ppm. This can

often be accomplished by distilling off the solvent-water azeotrope, decanting the water, and

then drying the remaining solvent with a molecular sieve, or other desiccant. The water removed

in this operation must then be either treated or drummed for disposal.

FRACTIONAL DISTILLATION

Fractional distillation is carried out in a refluxed column equipped with either trays or packing.

Heat is supplied by a reboiler located at the bottom of the column while heat is removed at the

top of the column by a condenser. Fractional distillation allows for separation of multi-

component mixtures or mixtures of solvent and oils with very similar boiling points.

EVAPORATION

Evaporation can be employed for solvent recovery from viscous liquids, sludges, or still bottoms

resulting from distillation. Scraped or wiped-film evaporators utilize revolving blades which

spread the liquid against a heated metal surface. The vapors are recovered by means of a

condenser. Another type of system, a drum dryer, employs two heated counter-rotating drums

through which the liquid feed must pass. While both systems can handle viscous wastes, the

drum dryer is more tolerant of polymerizable contaminants.

OFF-SITE RECYCLING

If recycling of waste solvent on site is impractical, several off-site recycling schemes are

available.

RECYCLING SOLVENTS EFFICIENTLY

Segregating solvent wastes is usually an essential step prior to recycling. IBM Corporation

reported that segregation may also-increase recycling efficiency; segregating non-chlorinated

from chlorinated solvents resulted in 15 to 20 percent greater yields (Waste Reduction - The

Untold Story, 2985).

MOBILE SOLVENT DEGREASING UNITS

Automobile repair shops in California can lease fully-contained degreasing systems from Safety

Kleen Inc. Safety Kleen provides a batch-tolling service for degreasing solvents; it leases its

mobile units, including solvents, as one system. Safety Kleen periodically replaces the spent

solvent with fresh solvent, and recycles the spent solvent at a separate facility.

WASTE EXCHANGES

Waste exchanges generally exchange some 20 to 30 percent of the wastes they list (Banning,

1983, 1984). At present, the most common wastes listed are solvents and metal wastes. Other

wastes listed include acids, alkalis, other inorganic chemicals, organics and solvents, and metals

and metal sludges.

Toll recyclers: Toll recyclers offer services to generators by supplying solvent wash equipment

and solvent and waste recycling services. The solvent wash equipment is maintained by these

companies and the solvent is replaced periodically. The used solvent is recycled at an off-site

facility. Costs for these services range from 50-90% of new solvent cost.

WASTE EXCHANGE AND BROKERAGE

This is not a technology but an information service. A waste exchange can match a generator of

waste with a facility that can use the waste as a raw material. Commercial waste brokerage

services are also available. A waste generator is matched with a potential waste user who can

utilize the waste as a feedstock. Matching generators and users is based on the knowledge of raw

material inputs and wastes and product outputs of individual industries and firms.

Used Oil and Filters : Used Oil if managed improperly can potentially contaminate drinking

water. In fact, used oil from one oil change can contaminate 1 million gallons of fresh water - a

years' supply for 50 people! Moreover, used oil may be considered hazardous waste depending

on how it is disposed of or mixed with other wastes. Below you will find resources to help

owners and operators properly manage their used oil and filters.

Fueling : While gasoline offers a great advantage to us by powering our cars and buses, it has

some drawbacks too. Gasoline is composed of over 200 different chemicals, but there are four

that are toxic to humans – benzene, toluene, ethyl benzene, and xylene. When people pump

gasoline into their cars, the vapors escape into the atmosphere and can get into people’s lungs

when they breathe and also be deposited on their skin. Gasoline also evaporates very quickly and

pollutes the atmosphere. Certain chemicals called volatile organic compounds (such as benzene)

react with sunlight and form smog in urban areas. Moreover, spills of gasoline can contaminate

our drinking water supplies. A spill of one gallon of gasoline can render one million gallons of

water undrinkable. Finally, gasoline is flammable. A spark can ignite gasoline vapors. Below

you will find resources to help owners and operators manage their fueling operations in such a

way as to miminize its harmful effects, including the installation of vapor recovery systems

which is required for certain areas or gas stations with high monthly throughput under the Clean

Air Act.

Proppants/frac sand: Proppants (also called “frac sand”) refers to the aluminum silicate beads

of varying sizes injected into wells to hold formation fractures open, thus increasing subsurface

oil flow to the wells. When these materials are transported back to facilities with crude oil from

the wells, the beads settle out, along with formation sand, to form a semi-solid sludge in the

bottoms of vessels. This proppant/frac sand now goes into lined landfills in South Alaska, but it

has been suggested that the material could be sold as construction fill if it could be separated

from the crude oil. Janet Platt of BP. Exploration noted that BP considered constructing an oily

waste facility that would have separated the recyclable solids from the oil, but the company

cancelled the project because the viewed as prohibitive. Roundtable participants also raised

concern that less of this proppant/frac sand will likely be produced in the future, making

recycling less feasible economically.

Bottom wastes: Tank bottom wastes are a type of sediment that accumulates in oil field vessels

and pipelines when fluid turbulence is low. These dense sludges are composed of crude oil,

paraffin, asphaltics, reservoir material, drilling mud, and slightly radioactive material (called

NORM--“naturally occurring radioactive material”), in addition to the frac sand/proppant

discussed above. Historically, bottom waste has been put into lined oily waste pits either for

permanent burial or for temporary storage until it can be treated to remove hydrocarbons, usually

by thermal processes. As mentioned previously, BP designed a plant using solvent extraction to

recover salable crude oil from bottom wastes, plus a recyclable solid for construction purposes.

This waste stream was strongly suggested by roundtable participants as a subject for future

research, as it represents a large, potentially toxic waste stream which is not recycled. Partially

cleaned solids might be safely recycled by incorporating them into Portland cement or other

materials for oil field applications. As with drill cuttings, determining acceptable levels of trace

contaminants and methods of reducing analytical costs might also prove fruitful topics for

research.

Dehydration and sweetening wastes: Polyols and glycols are used in the oil and gas industry as

antifreeze and to remove traces of water from natural gas streams in the production of fuel gas. It

was mentioned in the course of the roundtable discussion that waste dehydration polyols and

glycols sometimes emit traces of benzene. Identifying an inhibitor chemical or process of

benzene formation in these processes was suggested as a worthwhile research objective. A

general study of how to reduce or inhibit contamination of triethylene glycol (TEG) and methyl

ethyl glycol (MEG) streams, perhaps by using alternative dehydrating agents, might also be

worthwhile. Hydrogen sulfide (H2S), a corrosive gas more toxic than hydrogen cyanide, is

emitted by sulfate-reducing bacteria growing in subsurface formations and oil field surface

equipment. The evolution of hydrogen sulfide is currently inhibited by using powerful biocides

like acrolein and formaldehyde; unfortunately, these biocides are highly toxic and dangerous

materials. The best way to avoid spills of these materials might be to institute a research and

development project find an effective, but less toxic, biocide to use in their place.

USED OIL AND USED OIL FILTERS:

Engines and other machinery in all areas of operations require lubricating oil and oil filters.

DRUMS AND CONTAINERS: Drums and containers are required for delivery and storage of

chemicals and materials used in all areas of operations.

SANDBLAST MEDIA: Sandblasting is typically used to prepare equipment for painting and to

remove scale from equipment.

PAINT AND PAINT WASTES: Painting is generally required for maintenance of equipment.

Paint thinners, solvents, and unused paint are generated wastes.

PESTICIDES AND HERBICIDES: These chemicals are used to control insects and vegetation at

various locations (e.g., drilling locations).

VACUUM TRUCK RINSATE: Vacuum trucks recover waste liquids generated by various

operations.

SCRAP METAL: Scrap metal consists of damaged tubular or other equipment, crushed drums,

remnants of welding operations, cut drill line, etc. Scrap metal may contain naturally occurring

radioactive materials (NORM). Scrap metal Sheet metal, piping, tubing, wire, cable, empty

drums/containers, tanks, pump housings, valves, fittings, vehicle/equipment parts

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