Water Injection 2011

Water Injection Facilities

Typical Changes in Production Rates During

the life time of a 100,000 bopd oil field

PRODUCED WATER TREATING

SYSTEM

Produced Water

from:

FWKO

Treaters

Test Equipment

Etc.

Primary

Treatment

Secondary

Treatment Disposal

Equipment Types

Skim Tank

Skim Vessel

CPI

Cross Flow

SP Pack

HydroCyclone

Equipment Types

CPI

Cross Flow

Flotation

SP Pack

HydroCyclone

Equipment Types

Disposal Pile

Skim Pile

SP Pile

Reinjection

Disposal Wells

Particle size

50 150 m Particle size

10 20 m

Bulk Oil Removal

Large Oil droplet

removal

Small Oil droplet

removal

Plate Coalescers

Parallel Plate Interceptors ( PPI)

Corrugated Plate Interceptors (CPI)

Cross Flow Separators

Metoda diatas bekerja berdasarkan konsep pemisahan secara gravitasi, dimana butir butir minyak bergerak keatas sampai menyentuh plate bagian atas. Minyak yang menempel pada plate kemudian mengalami proses coalescence dan bergerak sepanjang plate dan terpisahkan dengan fasa air.

A

B

h

Oil Droplet

Plate

A

B

h

Plate

Water

OIL

Corrugated Plate Interceptor ( CPI )

Skimmer FWKO

Oil + Emulsion

Oily Water

Gas

Oil + Water

Flotation

Clean Water

Oil + Emulsion

Well

How to Clean Produced Water

Oily Water 1

2 3

Mechanical IGF

Induced Gas Flotation

Gas

Skimmer FWKO

Oil + Emulsion

Oily Water

Gas

Oil + Water

Flotation

Clean Water

Oil + Emulsion

Well

How to Clean Produced Water

Oily Water 1

2 3

Filter 4

Hydrocyclone

Wells

FWKO

GAS FLOTATION

Gun

Barrel

OiLStorage

Tank

Surge

Tank

Crude

Oil

Solid

Filter

Water

Tank

To

Injection

Wells

PUMP

Water Injection

System

Deaeration

Hydrocyclone

CPI

Sale

Point

Gas

O2 , CO2 , H2S

Min 25% of the

water volume

to be injected

Cold water can be deareated by reducing

pressure until the water boils. Vacuum

deareation is often used where a maximum

axygen content of 0.3 ml/liter is permissible.

Removal of Oxygen, CO2 dan H2S dapat

meningkatkan PH, yang selanjutnya dapat

mempermudah terjadinya carbonate scale

formation.

Vacuum Deaerator

Temperature (F) Pressure (psig)

40 0.123

60 0.256

80 0.507

100 0.950

120 1.690

140 2.890

160 4.740

180 7.510

200 11.530

212 14.700

Boiling Point of Water at

Reduced Pressure

Oil Gas Field Surface Facilities

System

Prinsip prinsip Gas Flotation

2mwo

6-w

Rd - ( 10 x 1.786

h t

)

Water

DROPLET

vR

OIL OIL

Water

GAS

h

dm

Dissolved Gas Flotation Cell

Clean Water

Oily

Froth

Oily Water

SKIMMER

Full Stream Pressurization

GAS

Oily

Water

Flotation Cell

Gas

Split - Stream Pressurization

GAS

Oily

Water

Flotation Cell

Gas

Induced Gas Flotation

( IGF )

Modern IGF

Gas Flotation Unit

Mechanical IGF

MECHANICAL EQUIPMENT FOR

INDUCTION

Autostable Floating Skimmer with

Gas Seal

OIL OUTLET DESIGN

OIL

SCHEMATIC OF A

HYDROCYCLONE

FOR WATER OIL

SEPARATION

Du

Ls

Lu

Dc > Du > Do

Over Flow

Under Flow

(Clean Water)

(Oil)

Oil

Liquid

Inlet

WASTE DISPOSAL BY INJECTION IN

UNDERGROUND FORMATION

For many years, the petroleum industry has disposed of oilfield brines by injection into underground formation.

A formation suitable for the injection of waste water obviously must be available.

The formation selected should not allow the waste water to migrate to a fresh water stratum, thereby polluting the

water in that stratum.

Generally, if the selected formation contains salt water, it is reasonable to expect no future pollution of any fresh

water stratum.

The primary purpose of treating injection

water, both waste water and water used in

secondary recovery, is to prevent plugging

of the disposal wells.

Water Quality

The principal factors which define the water quality

are:

(i) solids - dissolved or suspended

(ii) dispersed oil

(iii) dissolved gasses

(iv) bacteria

The Common Sources of Water for

A water Flood

1. Produced water

2. Brine or fresh water from other

subsurface zones (supply wells)

3. Surface water from oceans, lakes,

ponds, streams or rivers

4. Alluvial water wells which draw water

from shallow aquifers which are

connected to a surface water body.

Cations Anions Properties

Calcium (Ca) Chloride (Cl) pH, Suspended Solid (amount, size,

shape, chemical composition)

Magnesium (Mg) Carbonate (CO3) Turbidity, Temperature, SG,

Dissolved oxygen, Dissolved CO2,

Sodium (Na) Bicarbonate (HCO3) Sulfide as H2S, Bacterial Population,

Iron (Fe) Sulfate (SO4 ) Oil Content

Barium (Ba)

Strontium (Sr)

Primary Constituents and Properties

The above constituents and properties are important from the

standpoint of plugging or corrosion.

Common Water Analysis Determination

for Injection Water

Alkalinity

Calcium

Carbonate

Chloride

Hydrogen Ion (pH)

Iron

Magnesium

Silica

Specific Gravity

Specific Resistivity

Sulfate

Total Dissolved Solid (TDS)

Suspended Solids

Issue Effect Treatment

Suspended solids Plugging of Injection formation Filtration

Suspended oil Plugging of Injection formation /

(particularly in presence of solids)

Hydrocyclones /

Flotation / Filtration

Dissolved Gases

{O2 / CO2 / H2 S}

Corrosion of well and facilities.

Plugging of formation by corrosion

products

Degasification

Corrosion inhibitor

Injection

Formation of Solids

{CaCO3 / Ba SO4 /

CaSO4 / FeS}

Equipment and formation plugging

by scale

Scale inhibitor

Injection

Bacteria

{Aerobic / Anaerobic

(sulphate reducing)}

Formation plugging by bacterial

residues or corrosion products

Biocides

Water incompatible

with formation

Loss of permeability of injection

formation

- Pre-treat formation

(clay stabilizers)

- Alter injection water

chemistry

Commonly Handling Problems in

Water Flooding

De-Oxygenation

The presence of Oxygen in concentrations

greater than 5 x 10-3 g/m3 (5 ppb) in water

flood operations can cause severe corrosion

and plugging of the formation by corrosion

products.

Gas Stripping (Left) & Vacuum Deaerator to

Deoxygenate Water

Gas Stripping

Removal of oxygen by gas stripping is based on

lowering of the solubility of oxygen in water by

reducing the oxygen partial vapour pressure.

Henrys Law states that gass solubility is proportional to the vapour pressure of the gas

over water. Oxygen from the water may be

stripped by passing a (low oxygen content)

stripping gas through the water in co-current or

counter-current flow.

Vacuum De-aeration

The principle of vacuum de-aeration is to reduce

the partial pressure of oxygen by boiling the

water. At a temperature of 15C, water boils at a

pressure of about 0.017 atm and the residual

water oxygen content is reduced to 150 ppb.

Chemical Treatment With Oxygen

Scavengers

Oxygen removal to the required 5 ppb level is

rarely possible. Oxygen scavengers are used to

achieve this very low value. Oxygen scavengers

remove oxygen from water by chemical

reaction. A large number of chemical

compounds can be used for this purpose.

Water Injection System

Chlorination

Chlorination is a widely used, inexpensive,

effective biocide. Chlorine hydrolyses to form

hydrochloric and hypochlorous acid with water

By contrast, chemical incompatibility between injected

sea water and formation water is the cause of the

deposition of sulfate mineral scales. This occurs

because sea water contains reasonable concentrations

of Sulfate anions (up to 2,800 ppm) but is low in divalent

cation {420 ppm Calcium (Ca++), trace Ba++ and

Strontium (Sr++)}. By contrast, many formation waters

contain significant concentrations of barium from tens

of parts per million to thousands.

The solubility of Barium Sulfate (BaSO4 or Barite) is very

low, being only 4% of that of calcium carbonate. Barite is

precipitated by the reaction:

Ba++ + SO"4 Ba SO4

BaSO4 is one of the most insoluble of the scaling minerals.

A similar problem is encountered with Strontium Sulfate

(celestite or SrSO4) in some fields.

A less frequently encountered scale is Calcium Sulphate

(CaSO4). This is due to the unusual solubility behaviour

of Gypsum (CaSO4. 2H2O), the most commonly

encountered form of calcium sulphate. Gypsum has a

solubility maximum at 40C (i.e. it shows reduced

solubility at both higher and lower temperatures). The

issue is complicated by the fact that the equilibrium form

above 40C is Anhydrite (Ca SO4); which is even less

soluble. A further complication is that this transition

temperature is itself dependent on the salinity.


for Injection Water in Oil Field

Alkalinity

Calcium

Carbonate

Chloride

Hydrogen Ion (pH)

Iron

Magnesium

Silica

Specific Gravity


Sulfate


Suspended Solids


for Potable Water

Alkalinity

Calcium

Carbonate

Chloride

Hydrogen Ion (pH)

Iron

Magnesium

Silica

Specific Gravity


Sulfate


Suspended Solids

Arsenic

Bacteriologic

Chromium

Fluoride

Lead

Manganese

Odor

Oxygen

Phenol

Phosphate

Selenium

Turbidity

Zinc

Suspended Solids

Solid concentration

Particle Size Analysis

Particle shapes

Composition of Solids

Turbidity

The main items to be considered in

water source selection

Corrosion

Scaling tendency

Water compatibility

Formation Sensitivity

Water quality

Alkalinity and Acidity

For waters over pH 4.5, alkalinity may range

to 1200 ppm, but it is generally less than 500.

Acidity may range from zero to several

hundred ppm in mine waters.

Hardness

Hardness has usually been referred to as the

soap consuming power of water. Most of this

effect with soap is caused by magnesium

and calcium in the water, but other alkaline

earths give the same effect.

Calcium and magnesium hardness

represent values calculated from the

concentrations of these two ions.

Turbidity

Turbidity simply means that the water is not "

clear " and that it contains undissolved

matter such as suspended solids, dispersed

oil or gas bubbles. It is a measure of the

degree of "cloudiness" of the water. Turbidity

indicates the possibility of formation plugging.

Turbidity measurements are often used to

monitor fiIter performance.

Temperature

The temperature of the water affects the scaling

tendency, the pH and the solubility of gases in

water. The specific gravity of water is also a

function of temperature.

Chemical Composition of Suspended Solids

Determination of the composition of

suspended solids is extremely important. It

makes it possible to ascertain their origin

(corrosion products, scale particles formation

sand, etc.) so that proper remedial action can be

taken. Known edge of their chemical composition

is also important from the standpoint of designing

a cleanout procedure should plugging occur.

Specific Gravity of Water

The magnitude of the specific gravity is a direct indicator of the total amount of

solids dissolved in the water.

Waterflood Inspection and system

Analysis

Dissolved

Iron

(mg/l)


Analysis

Turbidity

( JTU )


Analysis

Corrosion

Rate

(mpy)

1 2 3 4 5 6 7

No Item Record Indication

1 Iron Increase corrosion

decrease deposition

2 Calcium decrease Possibly scale formation

3 Bicarbonate decrease Deposition unless the PH is being changed

4 Carbonate decrease Deposition unless the PH is being changed

5 Sulfate decrease Deposition as Ca SO4 and or Ba SO4

6 Temperature Change in temperature affect scale formation

7 H2S increase Sulfate reducing bacteria

decrease The presence of oxidizing agent in the system (air)

8 Suspended

Solid

increase Corrosion, scale formation, bacterial activity.

decrease deposition

Waterflood Inspection and System Analysis

No Item Record Indication

9 Turbidity Increase Increase plugging solid

decrease deposition

10 Water quality

11 Corrosion

rate

closed Increase indicate a oxygen entry

12 Oxygen Measurement Should be taken along the system

13 Oil carryover Check all separation system

14 Filter

Operation

Check upstream and downstream point

15 Bacteria

Count

Check all the time

16 Visual

inspection

Very important , most reliable method

Water Analysis Results

Core Holder

Measuring

Cylinder

Constant Rate Pump

Transfer

Vessel

Pressure

Gauge Pressure

Gauge

Valve 2 Valve 1

Schematic of Coreflood Apparatus

OIL

Sea Water Source for Water Injection

Water Quality Plot

1

10

100

Excellent

Poorest

10 20 30 40

Flow Rate

(ml/sec)

Liquid Volume Injected

SLOPE

The wells can be plugged by :

Entrained solid,

Oil and bottom settlings,

Sulfur,

Bacteria,

Precipitation of salts after treatment.

While a few parts per million of plugging material

do not appear to be very great amount, the large

volume of water injected in some wells can

accumulate these few parts per million into a

considerable mass of material which can plug a

well.

When the water is disposed of by injection into a

sand formation, the sand face acts as a filter.

Example:

If 10,000 barrels of water containing 5 ppm ( parts

per million ) of a plugging material are injected

daily, 17.4 pounds of solids will collect each day

on the surface of the sand, resulting in over 500

pounds per month and probable plugging of the

well. Well plugging is not caused by only solids

volume, but also due to particle size of the solids.

Injection Rate Decline due to impairment by

one of Four Mechanisms

Well bore narrowing

Invasion

Perforation Plugging

Well bore fill-up

An Injection System for water

disposal

Gathering system of water waste,

Collection center,

Water treatment facilities,

Injection well

Evaluating Suitability of Subsurface Disposal

Project

Geology

1. The areal extent

2. Thickness

3. Lithological character,

Water Composition

Whenever possible, water samples representing all aquifers

penetrated should be collected and analyzed. Samples of the

disposal brine should also be analyzed. Compatibility tests

should be made with waters that are to be mixed in the

operation.

Well and Reservoir Data

A study of the performance records of existing production and

disposal wells is helpful in predicting future requirements for disposal

system. The disposal reservoir and its ability to handle waste water is vital

to the success of the project.

Porosity

Porosity is used to determine the storage capacity of the reservoir. It is

designated as absolute and effective porosity.

Absolute porosity is the percentage of pore volume in the rock, without

regard for interconnection of pore spaces. Rock of high porosity may have

low permeability, because there is no connection between pores.

Permeability

The ability of reservoir rock to let fluid flow through its interconnected pore

volume or its fluid conductivity is termed its permeability (K).

Injection Rate

Darcy equation can be used to calculate the rate of

brine or waste disposal into a subsurface formation

containing fluid.

Components of a Subsurface Brine

Disposal System

Gathering System for Waste Injection Water,

Collection Center,

Water Treatment Plant,

Injection well,

Pumps

Collection Center

A collection center is a tank or lined pond used to

collect waste water from various heater treaters and

separators in the field. From here, the water is

pumped or gravity flowed to the treating plant.

Injection water containing oil will generally plug the

injection formation. Since waste water from heater

treater contains a small amount of oil which was

not removed, or oil accumulated from leaks, it may

be necessary to remove this oil before water is

injected.

The collection center may also serve as an oil brine

separator. The incoming water passes through a

baffle system system which separates the oil by

gravity, then a skimmer removes it.

Water Treatment Plant

There are two general type of disposal system: the

open and the closed type.

Since surface Temperature and Pressure are different from those in the reservoir, the chemical equilibrium of the water

may be changed.

Dissolved carbon dioxide, hydrogen sulfide, methane, and other gas will probably escape from the water.

The gases above certainly will be removed on aeration, and oxygen will be dissolved in the water.

Slightly soluble carbonate will precipitate due to the loss of carbon dioxide. These solids are removed by coagulation,

sedimentation, and filtration.

The dissolved oxygen may cause the water to be very corrosive. However, oxygen corrosion can be

minimized by using a de-aerator to remove the

oxygen or using corrosion resistant flow line and

injection tubing.

Closed System

Designed to exclude oxygen (trouble maker).

Contains very small amount of oxygen.

Requires very little chemical treatment.

More difficult to exclude oxygen from the system (not economical to remove

oxygen)

Open System

No attempt is made to exclude oxygen from the system.

Oxygen-saturated surface water is used as a source water.

A water is intentionally aerated to remove H2S and or CO2.

Open system makes internal coating, lining or plastic pipe a necessity is most system to control corrosion, economically.

Source Solid

removal Water

Storage

Injection

Pump Wells

OPEN SYSTEM

Wells

Source Solid

removal Water

Storage

Injection

Pump

CLOSED SYSTEM

Oxygen

Removal

SURFACE WATERS

Skimmer, Gas

Flotation Unit,

Filter, Membrane

Heater,

Vacuum,

Sulfite Ion,

Hydrazine

Source Solid

removal Storage Injection

Pump Wells

OPEN SYSTEM

Source Solid

removal Storage Injection

Pump Wells

CLOSED SYSTEM

Oxygen

Removal

SUBSURFACE

WATERS

AERATION

1.5 micron 10 micron

Typical Disposable Filter Cartridges

Oil

Outlet

Oily

Water

Water outlet

Skimmer Tank

To Remove Oil from Water

4 Stages Gas Flotation

Cell

Untuk memisahkan padatan yang halus dan

butiran minyak yang sangat kecil dari air

Oil

Clean

Water

Saturated with oxygen - very corrosive

Contains suspended solids and marine organisms. Amount

varies with location and depth. Normally must be filtered.

Contains aerobic bacteria and sul fate reducing bacteria.

Fouling must be prevented in the intake system.

Calcium carbonate scale is likely to form in the injection

wells and heat exchange equipment.

Sea water

( 1 )

( 2 )

( 3 )

( 4 )

( 5 )

Produced Water

( a ) Usually contains dissolved H2S and/or C02,

Corrosivity varies.

( b ) May contain suspended solids.

( c ) 0il carryover is a frequent problem.

( d ) Sulfate reducing bacteria are often present.

( e ) Scale formation is possible.

Subsurface Source Water

(a ) May or may not be corrosive, depending on composition. 0xygen

Leakage into source well annulus i s a frequent problem.

( b ) May be scale forming. Normally scaling water would not be used unless

absolutely necessary.

( c ) If sufficiently fresh, formation sensitivity must be considered.

( d ) Sulfate reducing bacteria can be a problem.

( e ) May contain suspended solids . Normally this is not a serious problem,

and many source waters do not require filtration .

( f ) Watch for incompatibility with formation water. Possible scale problems

introducing wells after breakthrough.

Necessary to examine in detail the

possibility of:

1. Corrosion

2. Scale formation

3. Water compatibility

4. Formation sensitivity

5. Removal of suspended solid

6. Bacterial activity

7. Oil carryover

Concerns in designing An Injection

System Possible water sources

Open or close system

Material selection, coating and lining

Chemical addition,

Possibility of dissolved gas removal

Need for filtration

Need for oil skimming tanks or flotation cells

The use of split injection systems to avoid mixing incompatible waters

Sampling points

Monitoring devices

Documents

Water Injection 2011