OFFSHORE ENVIORNMENTAL IMPACT

Nome da EmpresaNOME DO EVENTO OCORRIDO EM __/__/__

OFFSHORE ENVIONMENTAL IMPACTS

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Course Out lines:

1-Oil Pollution of the Sea2-Oil spills in the sea3-Waste discharges during the offshore oil and gas activity

4- Gas impact on fish and other marine organisms5-Accidents during the offshore oil and gas development.



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Oil Pollution of the Sea

• Tables 1 and 2 show the variety of oil pollution sources and give expert estimates of the scales of distribution and impact of each of these sources on the marine environment


Table 1. Sources and scale of oil pollution input into the marine environment


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Types and Source of Input Environment Scale of Distribution and Impact

Hydrosphere Atmosphere Local Regional Global

Natural:Natural seeps and erosion of bottom sediments

+ - + ? -

Biosynthesis by marine organisms + - + + +

Anthropogenic:Marine oil transportation (accidents, operational discharges from tankers, etc.)

+ - + + ?

Marine non-tanker shipping (operational, accidental, and illegal discharges)

+ - + ? -

Offshore oil production (drilling discharges, accidents, etc.) + + + ? -

Onland sources: sewage waters + - + + ?

Onland sources: oil terminals + - + - -

Onland sources: rivers, land runoff + - + + ?

Incomplete fuel combustion - + + + ?


3. DADOS DO ACIDENTE E DO ACIDENTADO/ VICTIM AND ACCIDENT INFORMATION


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Table 2. Estimates of global inputs of oil pollution into the marine environment

(thousands tons/year of oil hydrocarbons)

Source 1973* 1979** 1981* 1985*** 1990***

Land-based sources:Urban runoff and discharges

2,500 2,1001,080(500-1,250)

34% 1,175 (50%)

Coastal refineries 200 60100(60-600)

- -

Other coastal effluents - 15050(50-200)

- -

Oil transportation and shipping:Operational discharges from tankers

1,080 600700(400-1,500)

45% 564 (24%)

Tanker accidents 300 300400(300-400)

- -

Losses from non-tanker shipping

750 200320(200-600)

- -

Offshore production discharges

80 6050(40-60)

2% 47 (2%)

Atmospheric fallout 600 600300(50-500)

10% 306 (13%)

Natural seeps 600 600200(20-2,000)

8% 259 (11%)

Total discharges 6,110 4,670 3,200 100% 2,351


4. DESCRIÇÃO DO ACIDENTE / ACCIDENT DESCRIPTION


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Oil spills in the sea

Oil spills in the marine environment•Fate and behavior of oil in the marine environment:Complex processes of oil transformation in the marine environment start developing from the first seconds of oil's contact with seawater. The progression, duration, and result of these transformations depend on the properties and composition of the oil itself.

•Physical transport:the distribution of oil spilled on the sea surface occurs under the influence of gravitation forces. It is controlled by oil viscosity and the surface tension of water. Only ten minutes after a spill of 1 ton of oil, the oil can disperse over a radius of 50 m, forming a slick 10-mm thick. The slick gets thinner (less than 1 mm) as oil continues to spread, covering an area of up to 12 km2 .

Dissolution: Most oil components are water-soluble to a certain degree, especially low-molecular-weight aliphatic and aromatic hydrocarbons. Polar compounds formed as a result of oxidation of some oil fractions in the marine environment also dissolve in seawater


Oxidation and destruction:Chemical transformations of oil on the water surface and in the water column start to reveal themselves no earlier than a day

after the oil enters the marine environment. They mainly have an oxidative nature and often involve photochemical reactions.

Microbial degradation:The fate of most petroleum substances in the marine environment is ultimately defined by their transformation and degradation

due to microbial activity. About a hundred known species of bacteria and fungi are able to use oil components to sustain their

growth and metabolism.

Self-purification:As a result of the processes previously discussed, oil in the marine environment rapidly loses its original properties and

disintegrates into hydrocarbon fractions. These fractions have different chemical composition and structure and exist in

different emigrational forms


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Waste discharges during the offshore oil and gas activity

Sources, types, and volumes of waste dischargesPractically all stages and operations of offshore hydrocarbon production are accompanied by undesirable discharges of liquid, solid, and gaseous wastes.

The proportions and amounts of discharged wastes can change considerably during production. For example, the amount of solid drilling cuttings usually decreases as the well gets deeper and the hole diameter becomes correspondingly smaller.

Produced waters, including injection waters and solutions of chemicals used to intensify hydrocarbon extraction and the separation of the oil-water mixtures, are one of the main sources of oil pollution in the areas of offshore oil and gas production.

Recently, a technology was developed to remove the drilling wastes, especially cuttings, by reinjection their slurry into a geological formation. This gives some hope to achieving zero discharge of oil-containing wastes during offshore oil and gas production



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Chemical composition of discharged wastes

As noted earlier, the spectrum of chemicals entering the marine environment at different stages of oil and gas production is very wide. They include many hundreds of individual compounds and their combinations



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Drilling fluids and cuttings: Drilling wastes deserve special attention. The volume of drilling wastes usually ranges from 1,000 to 5,000 m3 for each well. Such wells can number into dozens for one production platform and many hundreds for a large field.

Produced waters: Produced waters usually include dissolved salts and organic compounds, oil hydrocarbons, trace metals, suspensions, and many other substances that are components of formation water from the reservoir or are used during drilling and other production operations. Besides, produced waters can mix with the extracted oil, gas, and injection waters from the wells. All of the above make the composition of the discharged produced waters very complex and changeable. It is practically impossible to speak about some average parameters of this composition, especially because reliable and complete analytical studies of these wastes are very rare



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Other wastes:

Large quantities of produced waters, drilling mud's and drilling cuttings, discussed above, as well as discharges of storage displacement and ballast waters are the source of regular and long-term impacts of the offshore industry on the marine environment



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Gas impact on fish and other marine

organisms

•The first important feature of interaction between gaseous traces and marine organisms is the quick fish response to a toxic gas as compared with fish response to other dissolved or suspended toxicants.

Medical toxicology distinguishes between three main types of intoxication by methane:

Light: results in reversible, quickly disappearing effects on the functions of central nervous and cardiovascular systems

Medium: manifests itself in deeper functional changes in the central nervous and cardiovascular systems and increase in the number of leukocytes in the peripheral blood

Heavy: results in irreversible disturbances of the cerebrum, heart tissues, and alimentary canal



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Another critical environmental factor that directly influences the gas impact on water organisms is the concentration of dissolved oxygen. Numerous studies show that the oxygen deficit directly controls the rate of fish metabolism and decreases their resistance to many organic and inorganic poisons.

•This decrease sometimes depends more on the species characteristics and the rate of their gas metabolism rather than on the nature of the poison



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Accidents during the offshore oil and gas development.

Accidents inevitably accompany offshore development. They are the sources of environmental pollution at all stages of oil and gas production. The causes, scale, and severity of the accidents' consequences are extremely variable. They depend on a concrete combination of many natural, technical, and technological factors.

Examples of Offshore Accidents:

1-Drilling accidents:Drilling accidents are usually associated with unexpected blowouts of liquid and gaseous hydrocarbons from the well as a result of encountering zones with abnormally high pressure.

2- Transportation and storage accidents:2.1- Tanker transportation: The main causes of tanker accidents that lead to large oil spills include running aground and into shore reefs, collisions with other vessels, and fires and explosions of the cargo

2.2- Storage: Underwater storage tanks with capacities of up to 50,000 m3 are built near the platform foundations or are anchored in the semi submerged position in the area of developments and near the onshore terminals. Of course, a risk exists of damaging the underwater storage tanks and releasing their content, especially during tanker loading operations and under severe weather conditions.

2.3- Pipelines: Complex and extensive systems of underwater pipelines have a total length of thousands of kilometers. They carry oil, gas, condensate, and their mixtures. These pipelines are among the main factors of environmental risk during offshore oil developments

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OFFSHORE ENVIORNMENTAL IMPACT