Application of Internal Olefin Sulfonates Application of Internal Olefin Sulfonates and Other Surfactants to EORand Other Surfactants to EOR..

Part 2: The Design and Execution of an ASP Part 2: The Design and Execution of an ASP Field Test.Field Test.

Marten BuijseMarten Buijse, Ruth Prelicz, Julian Barnes, , Ruth Prelicz, Julian Barnes, ShellShell,,

Claudio Cosmo, Claudio Cosmo, Salym Petroleum DevelopmentSalym Petroleum Development

West Salym field West Salym field

•• Western SiberiaWestern Siberia

•• > 1 bln stb oil in place> 1 bln stb oil in place

•• > 100,000 stb/day> 100,000 stb/day

•• WaterfloodWaterflood

•• Recovery efficiency < 50% Recovery efficiency < 50% �� selected candidate for ASPselected candidate for ASP

•• Reservoir propertiesReservoir properties•• depth = 2200 m., zonal thickness = 5depth = 2200 m., zonal thickness = 5--15 m.15 m.

•• "dirty" sandstone with clays, permeability = 10"dirty" sandstone with clays, permeability = 10--100 md100 md

•• reservoir temperature = 83ºCreservoir temperature = 83ºC

•• crude API density = 30.4, crude viscosity = 2 cpcrude API density = 30.4, crude viscosity = 2 cp

•• TAN = low (no soaps!)TAN = low (no soaps!)

ASP design ASP design –– Surfactant selectionSurfactant selection

General surfactant requirementsGeneral surfactant requirements

•• ultraultra--low IFT at low surfactant concentrationlow IFT at low surfactant concentration

•• optimal salinity must match salinity field brine (2optimal salinity must match salinity field brine (2--3% NaCl)3% NaCl)

•• low rock adsorption low rock adsorption �� anionic surfactantsanionic surfactants

•• stable at reservoir temperature (83stable at reservoir temperature (83ººC) C) �� sulfonates (Rsulfonates (R--SOSO33--))

50•• low emulsion viscosity, no low emulsion viscosity, no liquid crystalsliquid crystals

0

5

10

15

20

25

30

35

40

45

0 5 10 15

So

lub

ilis

ati

on

Pa

ram

ete

r, m

l/m

l

Optimal Salinity, %NaCl

IOS 15-18

IOS 20-24 Low SO3

IOS 20-24 High SO3

IOS 19-23 Low SO3

IOS 19-23 High SO3

IOS 24-28

Moderate

Optimal Salinity

with High Sol

Ratio

Typical

band

liquid crystalsliquid crystals

•• good water solubilitygood water solubility

•• cheapcheap

•• Selected: Internal Olefin Selected: Internal Olefin Sulfonates (IOS)Sulfonates (IOS)

•• also see Part 1 paper: SPE 129766also see Part 1 paper: SPE 129766

ASP design ASP design –– Surfactant selectionSurfactant selectionbenefits of long surfactant tailbenefits of long surfactant tail

Tail

ETail-Oil

Tail

ETail-Oil

WR =EHead-Brine

ETail-Oil

WR =EHead-BrineEHead-Brine

ETail-OilETail-Oil

Ultra-low IFT:

UltraUltra--low IFT (high low IFT (high solubilization) requires solubilization) requires large surfactant oil large surfactant oil interaction energy.interaction energy.

EEtailtail--oiloil (and solubilization) decreases with increasing oil MW.(and solubilization) decreases with increasing oil MW.

�� High MW oils benefit from longHigh MW oils benefit from long--tailed surfactants.tailed surfactants.

Head

oil

brine

EHead-Brine

Head

oil

brine

EHead-Brine

Ultra-low IFT:

• WR = 1

• ETail-Oil and EHead-Brine

must be large.

�� Preference for Preference for

surfactantssurfactants with with long/bulky alkyl tails long/bulky alkyl tails (such as IOS C24(such as IOS C24--28)28)

Surfactant selection and Surfactant selection and crude oil propertiescrude oil properties

•• Salym crude oil: average MW is relatively high.Salym crude oil: average MW is relatively high.

•• Solubilization generally decreases with increasing MW of oil.Solubilization generally decreases with increasing MW of oil.

•• Heavy components (asphaltenes, naphtenic acids) are often Heavy components (asphaltenes, naphtenic acids) are often surface active and move to the oilsurface active and move to the oil--brine interface.brine interface.

�� High MW surfactants for improved crude oil compatibility.High MW surfactants for improved crude oil compatibility.�� High MW surfactants for improved crude oil compatibility.High MW surfactants for improved crude oil compatibility.

SARA analysis

Saturates 28.6%

Aromatics 53.9%

Resins 12.2%

Asphaltenes 5.3%

C20+ fraction 56.6%

surface active crude

components at interface

from Narve Aske, Thesis, 2002

Surfactant selectionSurfactant selectionPhase behavior testsPhase behavior tests

•• 0.5% IOS C240.5% IOS C24--2828:: long tail, main long tail, main active surfactantactive surfactant

•• 0.2% IOS C150.2% IOS C15--18:18: increases increases optimal salinity and improves optimal salinity and improves solubilizationsolubilization

oil

brine solubilizationsolubilization

•• 1% SBA1% SBA: improves solubilization : improves solubilization

% KCl: 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5%

salinity

brine

ASP design ASP design –– Laboratory testsLaboratory tests

•• Phase behavior tests, to optimize surfactant formulationPhase behavior tests, to optimize surfactant formulation•• 0.5% IOS240.5% IOS24--28 + 0.2% IOS1528 + 0.2% IOS15--18 + 1% SBA18 + 1% SBA

•• optimum salinity: 1.3% KCl (+ 1% Naoptimum salinity: 1.3% KCl (+ 1% Na22COCO33))

•• Surfactant solubility testsSurfactant solubility tests•• not ideal, but acceptable at reservoir conditionsnot ideal, but acceptable at reservoir conditions

•• Polymer selection: temperature stability, viscosity, rheology, Polymer selection: temperature stability, viscosity, rheology, filtration and core flow testsfiltration and core flow tests•• 1500 ppm Flopaam 3230s 1500 ppm Flopaam 3230s �� 3 cp at reservoir conditions3 cp at reservoir conditions

•• Alkali (minimize surfactant adsorption)Alkali (minimize surfactant adsorption)•• 1% Na1% Na22COCO33

•• Core flow tests for oil displacement efficiency and surfactant Core flow tests for oil displacement efficiency and surfactant adsorptionadsorption

ASP design ASP design –– Core flow testsCore flow tests

40%

50%

60%

70%

80%

90%

100%

% O

il or

Surf

acta

nt

start of

emulsionSurfactant

Oil cut

Cumulative oil

•• 360 md Berea, 2" diameter, 12" length360 md Berea, 2" diameter, 12" length•• recovered 95% of oil remaining after waterfloodrecovered 95% of oil remaining after waterflood•• gravity effects (horizontal core)gravity effects (horizontal core)

0%

10%

20%

30%

40%

0.0 0.5 1.0 1.5 2.0 2.5 3.0Pore Volumes Produced

% O

il or

Surf

acta

nt

emulsionSurfactant

ASP Single well tracer testASP Single well tracer testHow does it work?How does it work?

EsterEsterEthanolEthanol

InjectionInjection: : Ester (40mEster (40m33) + Push water (160 m) + Push water (160 m33).).Ester partially partitions in oil.Ester partially partitions in oil.

ShutShut--in:in: 3 days. Ester partially hydrolyses 3 days. Ester partially hydrolyses to ethanol. Ethanol in water phase.to ethanol. Ethanol in water phase.

Back production:Back production:Ethanol travels faster than ester.Ethanol travels faster than ester.

Result:Result:Ethanol and ester return as separate peaks.Ethanol and ester return as separate peaks.Peak distance is used to calculate SPeak distance is used to calculate Soror..

Figure 5

EtOH (Product) and EtAc (Cover) Tracers

Hypothetical 1-Layer Test Result

0

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Produced Volume (barrels)

Co

ncen

trati

on

EtO

H (

pp

m)

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Co

ncen

trati

on

EtA

c (

pp

m)

EtOH

Example Data

EtAc

Example Data

ASP Single well tracer testASP Single well tracer testpump schedulepump schedule

Stage Volume (m3)

Rate (m3/day)

Comments

Waterflood 1700 200-80 injectivity decline due to skin?

Tracer injection 20 + 80 130 penetration depth: 3 m (10 ft)

Shut-in 3.5 days Tracer hydrolysis EtAc�EtOHShut-in 3.5 days Tracer hydrolysis EtAc�EtOH

Tracer prod. 180 m3 120

KCl preflush 45 120 Spacer; Remove Ca/Mg.

ASP 70 120-90 0.35 PV, based on tracer vol.

Polymer/brine 150 120-150 displace ASP

Tracer injection 40 +160 175

Shut-in 4 days Tracer hydrolysis EtAc�EtOH

Tracer prod. 320 120

ASP Single well tracer testASP Single well tracer testPressure and ratePressure and rate

180

210

240

270

300

m3/d

ay o

r b

ar

Start injection ASP.

BHTP

0

30

60

90

120

150

12:00 16:00 20:00 00:00 04:00 08:00 12:00Time - hrs

m3/d

ay o

r b

ar

Brine in wellbore.

Finished ASP injection.

Start post buffer

Injection rate

ASP at perfs

ASP Single well tracer testASP Single well tracer testResultsResults

•• Complex (nonComplex (non--ideal) tracer responseideal) tracer response

•• Can be explained assuming multiple layers + crossflowCan be explained assuming multiple layers + crossflow

200

250

Co

nc

en

tra

tio

n E

tOH

(p

pm

)

600

700

800

Co

ncen

tra

tio

n N

PA

(p

pm

)

Best-Fit 3-Layer

Model: Sor = 0.23

NPA tracerEtOH

0

50

100

150

0 20 40 60 80 100 120 140Produced Volume (m

3)

Co

nc

en

tra

tio

n E

tOH

(p

pm

)

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100

200

300

400

500

Co

ncen

tra

tio

n N

PA

(p

pm

)

Layer 2 accepted 18% of the

tracer-carrying fluid.

Layer 3 accepted 60% of

the tracer-carrying fluid.

NPA tracerEtOH

Layer 1 accepted

22% of the tracer-

carrying fluid.

Remaining oil saturation reduced from 23% to 2%

ASP Single well tracer test.ASP Single well tracer test.Complex tracer response.Complex tracer response.

NonNon--ideal tracer response ideal tracer response traced back to multiple traced back to multiple layers + crossflow.layers + crossflow.

ShutShut--in. Tracer hydrolysisin. Tracer hydrolysis

EtAc

EtOH

no crossflow with crossflow

high k

medium k

low k

push

shut-in, tracer hydrolysis

shut-in, hydrolysis + crossflow

tracer injection

ShutShut--in. Tracer hydrolysisin. Tracer hydrolysis

EtAc EtAc �� EtOHEtOH

Backproduction. EtOH Backproduction. EtOH travels faster than EtAc.travels faster than EtAc.

Tracer responseTracer response

single peak EtOH and EtAc

backproduction

complex tracer response

0

50

100

150

200

250

0 20 40 60 80 100 120 140Produced Volume (m

3)

Concentr

ation E

tOH

(ppm

)

0

100

200

300

400

500

600

700

800

Concentr

ation N

PA

(ppm

)

Layer 2 accepted 18% of the

tracer-carrying fluid.

Best-Fit 3-Layer

Model: Sor = 0.23

Layer 3 accepted 60% of

the tracer-carrying fluid.

NPA tracerEtOH

Layer 1 accepted

22% of the tracer-

carrying fluid.

0

100

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300

400

500

0 20 40 60 80 100 120 140 160 180

Produced Volume (m3)

Conc. EtO

H (ppm

)

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1600

Conc. EtA

c (ppm

)

EtOH

Example

Data EtAc

Example Data

backproduction

ConclusionsConclusions

•• West Salym crude oil has a significant fraction of high MW West Salym crude oil has a significant fraction of high MW components that are (partly) surface active and interact with components that are (partly) surface active and interact with the surfactant at the oilthe surfactant at the oil--brine interface.brine interface.

•• Theoretical considerations suggest the use of surfactants with a Theoretical considerations suggest the use of surfactants with a long alkyl tail, to maximize interaction energy with oil.long alkyl tail, to maximize interaction energy with oil.long alkyl tail, to maximize interaction energy with oil.long alkyl tail, to maximize interaction energy with oil.

•• In phase behavior tests, high solubilization was observed with In phase behavior tests, high solubilization was observed with a high MW (long tailed) IOS surfactant (IOS C24a high MW (long tailed) IOS surfactant (IOS C24--28).28).

•• In core flow tests, the ASP formulation based on IOS24In core flow tests, the ASP formulation based on IOS24--28 28 recovered 90+% of the oil remaining after waterflooding.recovered 90+% of the oil remaining after waterflooding.

•• A successful ASP test was performed in the field, in which the A successful ASP test was performed in the field, in which the SSoror in the near wellbore was reduced by more than 90%in the near wellbore was reduced by more than 90%