By :

NOVIA RITA, ST. MT

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ALKALINE INJECTIONALKALINE INJECTION

ALKALINE INJECTION

Alkaline injection is a process where pH of the injected water is being controlled in 12 – 13 range to increase oil recovery

Rock characteristics can affect alkaline injection process

General

ALKALINE INJECTION

Screening criteria: Reservoir is suitable for water injection No fracture present No gas cap Reservoir temperature < 200oF Injectivity should be sufficiently high Sandstone reservoir

General

ALKALINE INJECTION

Screening criteria: Oil viscosity < 200 cp Oil acid number > 0.2 mg KOH/gr crude oil Interfacial force tension between crude oil and

caustic solution < 0.01 dyne/cm

Chemicals: NaOH, KOH, NH4OH, Na3(PO4), Na2CO3, etc

General

ALKALINE INJECTION

Lowering Interfacial Tension Generally injected water has capillary number

± 10-6

Oil recovery can be increased by lowering interfacial tension 100 to 1000 times (capillary number raise up to 10-4 or 10-2)

Alkaline solution can lower interfacial tension

Displacement Mechanism

ALKALINE INJECTION

Lowering Interfacial Tension This mechanism is related to acid number,

gravitational force, and viscosity Acid number is amount of KOH in mg required

to neutralize 1 gr of crude oil to have pH = 7 Acid number > 0.5 mg KOH/ gr crude oil

Displacement Mechanism

ALKALINE INJECTION

The Change of wettability from oil wet to water wet can improve mobility ratio

The change of wettability from water wet to oil wet

Emulsification and entrapment This process can improve vertical and

horizontal sweep efficiency

Displacement Mechanism

ALKALINE INJECTION

Emulsification and entrainment

Dissolving rigid interfacial film

Displacement Mechanism

ALKALINE INJECTION

Considerations of laboratory programs: Acid Number

0.5 mg KOH/ gram crude oil Sample should be free of emulsion breaker,

inhibitor, other chemicals Decreasing of interfacial tension

Laboratory Programs

ALKALINE INJECTION

Considerations of laboratory programs: Decreasing of interfacial tension

Alkaline – oil interfacial tension < 0.01 dyne/cm Wettability reversal Emulsion forming Rigid film Mineral – reservoir rock reaction

Laboratory Programs

ALKALINE INJECTION

Field Operation

Water injection can be enhanced into alkaline injection by adding caustic materials

Do Laboratory test to determine optimum alkaline concentration

The main problem is the acceleration of plugging by gypsum at the production well

ALKALINE INJECTION

Application Singleton Field, Nebraska (USA)

1962, injection water Sor = 40 % ; Area of test = 50 acres Average permeability = 330 md Injected slug = 60650 bbl of water containing 2 %

NaOH Alteration water injection to alkaline injection Production increasing up to 28 bopd Recovery 6 % of OOIP

ALKALINE INJECTION

Application Midway – Sunset, California (USA)

NaOH concentration : 1% Area of test: 100acres ; 11 production wells and 3

emulsion injection wells Using radioactive tracer (shows that emulsion injection

lowering water channel) Fresh water is injected before and after slug emulsion

injection to hold salt water emulsion injection Emulsion slug 3% PV of testing area Additional recovery : 12.5% OIP

THANK YOUTHANK YOU

The EndThe End

ALKALINE INJECTION