© 2012 Cairn India Limited

IMPORTANCE OF CHEMICAL TREATMENT -- Mayur Dhole

23 Feb., 2013

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Why chemical treatment is important?

Sustain, Maintain & Increase Production (10-3-4: $$$)

Asset Integrity

Maintain Crude & Water quality

Reduce Equipment downtime and Maintenance

OPEX & CAPEX

HSE & Logistics

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Treatment Cost

Expected chemical treatment cost: $ 40 Million/year

Actual chemical treatment Cost: $ 6 Million/year

Operating cost of oil: $ 3 per BBL

Operating cost of oil with Chemicals: 10 cent/bbl

Which is 3.3%of the total operating cost of oil

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The most common types of problems in Oil & Gas Production with chemical used to solve

Problem Chemical Treatment Forward emulsions Demulsifier

Reverse emulsions Reverse emulsion breakers

Scaling Scale Inhibitor

Corrosion Corrosion Inhibitor

Bacterial Growth Biocide

Foaming Anti-foam

Filter-Aid Coagulants, Flocculants

Dissolved oxygen Oxygen scavenger

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Forward emulsions Reverse emulsions

continuous phase being the oil

Dispersed phase being the water Oil droplets are

suspended

Continuous phase being the water

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Several methods are used to break these emulsions: 1. Time 2. Heat- reduces viscosity 3. Chemical- Changes the surface tension at interface, allowing water to break free 4. Electric current in congestion with Heat & chemical-Disrupts the polarity of emulsifying agent causing them to rearrange & break the wall of film

Causes: 1. Heavy polar material in the crude oil (asphaltenes, resins, waxes, etc), 2. Solids (clays, scales, corrosion products, etc), 3. pH, oil and brine composition. 4. The pressure gradient or velocity gradient 5. Mixing or agitation

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Demulsifier

Used to Dehydrate & desalt the oil

Demulsifier has hydrophobic & hydrophilic properties which unable to penetrate the oil &

water film.

Works

Continuous phase being the oil

Dispersed phase being the water

Water Droplets

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Reverse demulsifier Used to Clear & clean the water

Works

Difference:

Demulsifier: Forms water droplet & settle out

Reverse demulsifier: forms oil globe & rise to from layer on the top

Product Selection:

Demulsifier: Bottle-test is typically used.

Reverse demulsifier: Bottle-test & wemco test is typically used.

Flocculation Coagulation

Oil Globe

Coalescence

suspended phase being the oil

Continuous phase being the water

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Scale & Corrosion

Causes:

Primary factors 1. Incompatible water 2. Alkalinity 3. Hardness 4. pH

Other factors 1. Oxidizing agents 2. Carbon dioxide 3. Dissolved solids

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Scale Inhibitor Scale deposits in surface equipment can increase operating pressures and

reduce efficiency

Type of scales: calcium carbonate, calcium phosphate, and magnesium silicate - precipitates out at higher temperature & low pressure. calcium sulfate (gypsum), strontium sulfate, and barium sulfate - precipitates out at lower temperatures & high pressure.

Type of chemical compounds (SI) used: Phosphate esters, phosphonates, and acid polymers

Treatment: Either in squeeze treatments into the producing formation or by continuous injection.

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Brine Chemistry Used for Scale Predictions THUMBLI WATER SAMPLE ANALYSIS FORMATION WATER SAMPLE ANALYSIS

Parameter

Units

Measured Value Parameter Units

Measured Value

Total Suspended Solids mg/l 6.6

Total Suspended Solids mg/l 169

Total Dissolved Solids mg/l 8480 Total Dissolved Solids mg/l 12085

Specific Gravity at 15° C 1.00

Specific Gravity at 15° C 0.995

pH at 20° C 7.76 pH at 20° C 6.8 Components Components Cations Cations

Sodium mg/l 1460 Sodium mg/l 2494 Potassium mg/l 9.09 Potassium mg/l 151.05

Calcium mg/l 275 Calcium mg/l 514 Magnesium mg/l 125 Magnesium mg/l 136

Barium mg/l 0.12 Barium mg/l 78.35 Strontium mg/l 5.38 Strontium mg/l 7.33 Total Iron mg/l 0.53 Total Iron mg/l 11.93

Dissolved Iron mg/l 0.1 Dissolved Iron mg/l 0.3 Anions Anions

Chloride mg/l 2377.4 Chloride mg/l 5830.6 Sulphate mg/l 415 Sulphate mg/l 4

Bicarbonate mg/l 114.9 Bicarbonate mg/l 534.8 Carbonate mg/l 23.18 Carbonate mg/l < 2

Carbon dioxide( aq) mg/l <0.1 Carbon dioxide( aq) mg/l 95.9

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Calcium carbonate scale forming mechanism Carbon dioxide reacts with water to produce carbonic acid CO2 (g) + H2O(l ) H2CO3 (aq) (carbonic acid ) Carbonic acid will continue to dissociate hydrogen, creating new deprotonated species of carbonic acid H2CO3 (aq) + H2O(l) H3O+ (aq) + HCO−3 (aq) HCO−3 (aq) + H2O(l) H3O+ (aq) + CO2− 3 (aq) In the water mixture there will be a mixture of the species H2CO3, HCO−3 and CO2− 3 . CO2− 3 (aq) + Ca2+ (aq) CaCO3 (s)

CaCO3 (s)

E-415 A (Water injection heaters) Cross section of scaled tube

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CaCO3 Mass on Mixing of Waters

Calcium carbonate maximum mass for mixing Mangala and Thumbli waters

0

100

200

300

400

500

600

700

100%Mangala

90%Mangala

80%Mangala

60%Mangala

50%Mangala

40%Mangala

20%Mangala

0%Mangala

Scal

ing

Tend

ency

65C, 1500psi70C, 1800psi85C, 1800psi70C, 5bar85C, 5bar90C, 1bar90C, 5bar120C, 5bar

Mg

/l of

C

aCO

3

Current Ratio of Mangala & Thumbli

Waters

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BaSO4 Mass on Mixing of Waters

Barium sulphate maximum mass for mixing Mangala and Thumbli waters

0

5

10

15

20

25

30

35

40

100%Mangala

90%Mangala

80%Mangala

60%Mangala

50%Mangala

40%Mangala

20%Mangala

0%Mangala

Max

imum

Mas

s (m

g/l)

65C, 1500psi70C, 1800psi85C, 1800psi70C, 5bar85C, 5bar

Current Ratio of Mangala & Thumbli

Waters

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Corrosion Inhibitor Most commonly associated with the presence of hydrogen sulfide, carbon

dioxide, or oxygen. Corrosion inhibitors work by adsorbing onto exposed metal surfaces Four generic groups: amine imidazolines, amines and amine salts, quaternary

ammonium salts, and nitrogen heterocyclic. Corrosion caused by oxygen is controlled by chemical reaction rather than

adsorption. Treatment: Continuous treatment, displacement treatment and squeeze treatment.

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Biocide SRB are the most common biological problem in O&G industry Sulfate reducing bacteria (SRB) reduce the sulfate ion to hydrogen sulfide, which causes chemical

corrosion, steel embrittlement, and fouling of equipment by formation of iron sulfide Biocide is surface acting chemical, which kill the planktonic & sessile bacteria and form film on the

pipe walls.

Types: Chlorine / Hypochlorite, very corrosive, will need a holding tank and neutralizer. Aldehydes:

Formaline, probably one of the more cost effective not everywhere allowed. Gluteraldehyde, probably most common used.(so is THPS) Acrolein, can soften/removed deposits, not everywhere allowed, difficult to apply.

THPS, cost effective, stops FeS formation through chelating Iron. Quaternary type amines, surface active, less cost effective in time kill tests. Calcium Nitrate, to prevent reservoir souring, probably not a good idea in combination with EOR.

Treatment: Slug treatments, batch treatment & continues treatment

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Corrosion mechanism of iron by SRB

The resultant accelerated corrosion mechanism of iron by the sulphate reducing bacteria is illustrated in equations 1. SO4-2 + 8 H = S-2 + 4 H2O (cathodic depolarization by SRB) 2. 8 H2O = 8 OH-1 + 8 H+1 (dissociation of water) 3. 2 H+1 + S-2 = H2S (reversible reaction) 4. Fe+2 + S-2 = FeS (anode corrosion product) 5. 3 Fe+2 + 6 (OH)-1 = 3 Fe(OH)2 (anode corrosion product) Benefits of Biocide: 1. Control system fouling from iron sulfide 2. Protect formations sour oil and gas production 3. Reduce biomass

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System fouling from iron sulfide

Pump suction strainer chocked Produced water pump suction line flushing

Back wash pit after startup Back wash pit at present

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Anti-foam

Antifoam bind to the nucleation sites of the contaminants and reduce their ability

to generate foam. They do this by promoting small bubbles to coalesce into

larger ones until they destabilize and collapse, causing gas separation and

displacing the surface active component on the bubble and making it instable

while promoting the fluid component of the foam to drain away.

Benefits 1. Reduce oil or condensate in gas flow 2. Improve separator efficiency 3. Reduce produced water foaming 4. Improve pump capacity and efficiency 5. Improve produced fluid flow 6. Reduce pump noise and vibration

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Coagulants & Flocculants Flocculation, is a process wherein colloids come out of suspension in the form of

flock or flakes by the addition of a clarifying agent. The action differs from

precipitation in that, prior to flocculation, colloids are merely suspended in a

liquid and not actually dissolved in a solution. In the flocculated system, there is

no formation of a cake, since all the flocks are in the suspension.

Coagulants neutralize the repulsive electrical charges (typically negative)

surrounding particles allowing them to "stick together" creating clumps or

flocks. Flocculants facilitate the agglomeration or aggregation of the coagulated

particles to form larger floccules and thereby hasten gravitational settling. Some

coagulants serve a dual purpose of both coagulation and flocculation in that they

create large flocks that readily settle

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Oxygen scavengers Oxygen scavengers chemically react with oxygen present in your source water, removing

integrity risks it poses and eliminating its potential to react with other ions present in your system

Most commonly chemicals:1) Carbohydrazide 2) Diethyl hydroxylamine (DEHA) 3) Hydroquinone 4) Methyl Ethyl Ketoxime 5) Sodium Sulfite 6) Catalyzed Sodium Sulfite 7) Ammonium Bisulfite.

Stoichiometric requirements

As a rule-of-thumb dose 20 mg/L (ppm) of scavenger in excess to the stoichiometric requirement.

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What do we need for better treatment

Suitable chemical with optimized dosage

Better infrastructure

Identify appropriate & effective injection points

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Questions?

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Thank You……..