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The Science and a Case The Science and a Case History of COHistory of CO22

Conformance Conformance Through the UseThrough the Use

of of

Complex Nano FluidsComplex Nano Fluids

Glenn Penny, Ph.D., Director of TechnologyGlenn Penny, Ph.D., Director of TechnologyTom Pursley, IOR Technical ManagerTom Pursley, IOR Technical Manager

2

••

Conformance Challenge:Conformance Challenge:––

Divert CO2 from High Perm Streaks or swept areas of reservoir Divert CO2 from High Perm Streaks or swept areas of reservoir into Unswept Reservoir;into Unswept Reservoir;

––

Idea is to Increase CO2 Sweep Efficiency or Utilization;Idea is to Increase CO2 Sweep Efficiency or Utilization;––

Increase Oil Production;Increase Oil Production;

Candidate patterns are generally selected according to the following criteria.1. Unusually high gas rate and high gas/oil ratio (GOR),2. Low wellhead pressure in the contributing injection well.3. Rapid interwell transit.4. Identifiable, high-permeability “thief”

zone.

Previous polymer methods to achieve CO2 conformance and mobility control•

Preformed Polymer gel (PPG)–

Good for very high perm thief zones (>3 Darcies)

•

Crosslinked

Gel Injection–

10 to 15kgal 3-5000 ppm

PAM + Cr–

Incremental oil costs 5 to $7/bbl depending on field (about 150 jobs performed in W TX 15 to 20% with CO2

•

Gelled foam injection (Freidman SPE 38837)–

CO2 replaces 60% of the volume–

Cost of gel conformance decreased 50% to around $3/bbl but only lasted 4 months in a limited field trial

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Previous CO2 Conformance with Surfactants

•

Surfactant injection with the CO2 (Sanders, Linroth

SPE 160016 –

Observed that more CO2 was injected into additional deeper zones but only while surfactant was being pumped

•

SAG Surfactant Alternating gas (Hoefner

SPE 27787)–

some profiles improved while many were not,–

the injection profile modification was highly transient

•

CO2 foam to increase CO2 viscosity to match reservoir oil to achieve favorable mobility ratio (Stephenson SPERE Aug 93)–

An extended field test showed the foam bank propagated only a few meters from the wellbore

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New Technique

••

Strategy:Strategy:––

Develop a low adsorbing high salt and oil tolerant Develop a low adsorbing high salt and oil tolerant foamerfoamer

that that works with CO2 works with CO2

Complex Complex nanofluidnanofluid

((CnFCnF®®

+ + FoamerFoamer))––

Inject Inject CnFCnF

+ + FoamerFoamer

in water phase and follow with CO2 to divertin water phase and follow with CO2 to divert––

Investigate in a CO2 core flood using a Dual Core Flood ApparatuInvestigate in a CO2 core flood using a Dual Core Flood Apparatus s with 50 with 50 mDmD

and 250 and 250 mDmD

Core Plugs.Core Plugs.

••

Action:Action:––

Inject a Complex Inject a Complex NanoNano

Fluid (Fluid (CnFCnF®®) Product Containing a Low ) Product Containing a Low Adsorbing salt tolerant Adsorbing salt tolerant FoamerFoamer

into candidate injection well into candidate injection well followed by CO2 to Create Conformance. followed by CO2 to Create Conformance.

––

Follow production of CO2 and oil before and after.Follow production of CO2 and oil before and after.

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One Method to Mitigate Adsorption is to Formulate in a One Method to Mitigate Adsorption is to Formulate in a Complex Complex NanoFluidNanoFluid

((CnFCnF): Oil/Solvent + Surfactant + Water ): Oil/Solvent + Surfactant + Water

= Clear Additive = Clear Additive

•Ternary diagram shows areas of microemulsion

system stability. •Area of 1 phase indicates oil water and surfactant appear as a single phase.•Oil is dispersed as Droplets that are nano

to

micrometers is size•

Surfactant

WaterOil/

Solvent

1 phase

3 phases

2 phases

Surfactant

WaterOil/

Solvent

1 phase

3 phases

2 phases

Water oil and surfactant form Water oil and surfactant form VeronoiVeronoiType structures on the order of 10Type structures on the order of 10--20 nm20 nm

These structures maintain their integrityThese structures maintain their integrityand clarity even at very dilute concentrationsand clarity even at very dilute concentrations

Ternary DiagramTernary Diagram

1E-3 0.01 0.1 1 10 1000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

PSD

volume-based (P

CS), %

by volume

Dynamic light scattering (PCS)

Emulsion Complex Nanofluid (CnF), neat CnF diluted (20 gpt, 2% KCl)

PSD

wei

ght-b

ased

(aco

ustic

s), %

by

wei

ght

Droplet diameter (m)

Acoustic spectroscopy

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

CnF diluted (2gpt, 2% KCl)

CnFCnF

NanodropletNanodroplet

Size DistributionSize DistributionMaximize Propagation into Reservoir MatricesMaximize Propagation into Reservoir Matrices

10‐20 nm NanodropletWith Foamer

MicellarMicellar

Solutions Vs. Complex Solutions Vs. Complex NanoFluidNanoFluid

σσSLSL

σσLGLG

σσLLLL

σσLGLG

σσSLSL

Injected fluid in contact with the formationInjected fluid in contact with the formation

MicellarMicellar

SolutionSolution CnFCnF

SystemSystem

•• Presence of liquidPresence of liquid--liquid interface prevents surfactant adsorptionliquid interface prevents surfactant adsorption•• Surfactant adsorption minimizes free energy of the systemSurfactant adsorption minimizes free energy of the system

nanodropletsnanodroplets

Adsorption Test: Fluid flowed through a 12Adsorption Test: Fluid flowed through a 12””

X 1X 1””

diameter column diameter column filled with cuttings. Surface tension measured after eachfilled with cuttings. Surface tension measured after each

pore volume.pore volume.

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KrussKruss

100 , Surface Tension 100 , Surface Tension

Higher surface tensions Vs. Pore Higher surface tensions Vs. Pore volvol

shows shows adsorptionadsorption

Adsorption mitigated by Adsorption mitigated by CnFCnF/ME formulation/ME formulation

0

10

20

30

40

50

60

70

80

0 2 4 6 8

Pore Volumes

Surfa

ce T

ensi

on (d

ynes

/cm

)

2% FS

NP

AE

ME

ME+2%FS

Foam viscosity in core Foam viscosity in core vsvs

Surfactant Type, Concentration Surfactant Type, Concentration Salinity and PressureSalinity and Pressure

•• Surfactant Surfactant ConcentrationConcentration

•• Salinity Salinity

•• Pressure Pressure

FoamerFoamer

SelectionSelection

Surfactants Foam SalinityRetention

on Sandstone

Temp Oil

Betaine √ √ X √ √

AOS √ X √√ X

#2Micro-emulsion+Betaine

+AOS good improved decreased good improved

Formulation 1: Betaine : AOS = 2: 8

Static Adsorption of Betaine vs ME+AOS+Betaine

Oil Effect on FoamOil Effect on Foam

Dual Core Flooding Tests with OilDual Core Flooding Tests with Oil

Label Formu-lation

Concn(gpt)

Preflush (PV)

Back Pressure

(psi)

Core permeability

(mD)

Test 1 Betaine 2 0 1200 67 and 9Test 2 #1AOS-BET8-2 5 1 1200 225 and 81Test 3 #2AOS-BET-

CnF17

5 0.5 1200 335 and 70

Test 4 #2AOS-BET-

CnF17

5 0.1 2400 167 and 85

COCO22

WAG ConformanceWAG Conformance

Dual Core System for CODual Core System for CO22

Foam Diversion TestingFoam Diversion Testing

Inject 0.5 PV of 5 Inject 0.5 PV of 5 gptgpt

Formula 2Formula 2150 F 15% Salinity, 1200 150 F 15% Salinity, 1200 psipsi

335 and 70 335 and 70 mdmd

Flow ratio changes from5 to 1 to 2.5 to 2 And is stable with time

Oil Recovery in Dual Core TestsOil Recovery in Dual Core Tests

Test 1BetaineTest 2AOS-BET8-2Test 3AOS-BET-METest 4AOS-BET-ME

Case HistoryCase History

CnFCnF

BasedBased Foam DiversionFoam Diversion

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Reservoir ConditionsReservoir Conditions•Sandstone

Permeability range of 50 mD

and 200 mD•T=150 oF•Formation Brine (FB)

Salinity is 15% TDS with divalent ions•West Texas Crude Oil

API 37.7 at 60oF, MMP = 2200 psi

Field treatment

•

Select injector that has low injection pressure relative to the others.

•

Inject ½

pore volume of CnF

based foam based on suspected flow profile

•

This was 3000 gal of 0.3% CnF

Foamer

injected at the end of the water injection cycle

•

Convert to CO2•

CO2 contacts the foamer

placed in the high perm area

and the CO2 is diverted to lower perm unswept

zones•

Observe CO2 emission rate and oil production rate

CnFCnF

Foam ConformanceFoam Conformance

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CnFCnF FoamerFoamer PumpedPumped

CnFCnF

Foam ConformanceFoam Conformance

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CnFCnF Foam PumpedFoam Pumped

CnFCnF

Foam ConformanceFoam Conformance

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StimOilStimOil FD FD –– 1 Pumped1 Pumped

CnFCnF

Foam ConformanceFoam Conformance

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StimOilStimOil FDFD--1 Pumped1 Pumped

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CnFCnF

Foam ConformanceFoam Conformance

Incremental Incremental ImprovementImprovement

Facts:Facts:

••Improved Production to Date:Improved Production to Date:

14,110 14,110 BblsBbls..••Cost per Incremental Bbl. to date:Cost per Incremental Bbl. to date:

$0.58$0.58

••Improved COP Percentage:Improved COP Percentage:

75%75%••Improved NPV Percentage:Improved NPV Percentage:

75%75%

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CnFCnF

Foam ConformanceFoam Conformance

Conclusions1.

Foamer

created with a combination of CnF+AOS+

Betaine

surfactant mixture is –

more resistant to crude oil ;–

more resistant to high salinity–

Has decreased betaine

adsorption on sandstone;

2.

Dual core flow tests show O.5 PV injection changes flow ratio from 8 to 1 to 2.5 to 2 and recovers 80% of the oil in the low perm core

3.

Field results show that the flared CO2 was reduced from 1.5 MMCFD to 0.5 MMCFC after the CnF

Foam

treatment4.

The production has steadily increased after the CO2 diversion resulting in 14,000 Bbl of oil in 4 months.

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Thank You!Thank You!

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