CO2 Immiscible Gas Displacement Recovery

18th Annual CO2 Flooding

Conference, Midland, Texas

Mark H HoltzMark H HoltzDecember 2012December 2012

Immiscible CO2 Flooding Recovery Mechanisms• Oil Swelling• Viscosity Reduction• 3 Phase Relative Permeability (Kr effects)

– Reduce Sor , and Krw

– Accelerated oil recovery, higher core flood recovery (Olsen et. al., 1992, Dale & Skauge, 2005)

• Oil Film Flow– IFT balance between phases in pores

• Improved Volumetric Sweep EfficiencyModified from Fernandez and Pascual. 2007 Spe # 108031

CO2 Effect On Oil Swelling and Viscosity Reduction• The Greater the CO2 Solubility,

The Greater the Oil Swelling and Viscosity Reduction.

• CO2 Solubility– Decreases with increased temperature,– Increases with increased pressure, – Increases with increased Oil API gravity– Gaseous CO2 is more soluble than liquid

• Oil Swelling Increases So

Simon and Graue, JPT 1/1965 SPE # 917

CO2 Effect On Oil Solubility and Viscosity Reduction

From SPE # 129710, Bui, et al., 2010

MMP

At 50% of MMP Viscosity decrease s by 75%

Immiscible CO2 in Under-Saturated Reservoirs, Milne field Example• Oil Viscosity Reduction

is Found to be The Dominant Mechanism

• 6-9 % OOIP Reserve Growth – Simulation of a reservoir

with Pb = 1,875 psi and Pi=3,500 psi

• Milne Point Field Data Supported Lab and Simulation Results.

Ning & McGuire, 2004, SPE # 89353

Experimental Immiscible CO2 Gas Flooding, Viscosity Reduction

• Experimented On 12.4 API Oil

• CO2 Dissolves Readily in Heavy Oil– 4% volume increase– Six-fold reduction in

viscosity• At low pressures flue

gas (CO2 & N2 ) displaced oil almost as well as pure CO2

Zhang, et al., JCPT 2/2006, Paper 2006-014

290 580 870 psi

Effect of Gas Saturation on Residual Oil Saturation, Stone 1, 3 Phase Kr Model

gtorwor aSSS orS orwSWhere:a gtS

= Residual oil saturation = Sor to waterflood

= coefficient = Trapped gas saturation

Author Wetability “a” CoefficientHolmgren and Morse (1951) Water-wet 0.5Kyte Oil-wet 0Skauge (1996) Water-wet 0.5 to 1.0MacAllister et al. (1993) Water-wet 0.75

MacAllister et al. (1993) Mixed-wet 0.25

MacAllister et al. (1993) Oil-wet 0.04

Wetability effects Sor in the presence of trapped gas

SPE # 62997, Kralik et al., 2000

3 Phase Pore Level Interaction• Initially Gas Only Moves into the Oil Bearing Pores because

– Threshold capillary pressure into water saturated pores is much higher.

• Oil Forms a Continuous Layer between Gas and Water.• Water Relative Permeability is Reduced.• Sweep Efficiency is Increased

From Dong et al., 2001, JCPT

2 Menisci

1 Menisci

Oil film

Gas Oil

Kuparuk River IWAG Example• Gas Saturation Reduces

Water Mobility– Reduces water handling– Increases sweep

efficiency• Mechanism Results in

Lower Residual Oil Saturation

From Ma and Youngren,1994 SPE # 28602

Immiscible CO2 Flooding Recovery Mechanisms• Oil Swelling• Viscosity Reduction• 3 Phase Relative Permeability (Kr effects)

– Reduce Sor, and Krw– Accelerated oil recovery, higher core flood recovery

(Olsen et. al., 1992, Dale & Skauge, 2005)

• Oil Film Flow– IFT balance between phases in pores

• Improved Volumetric Sweep EfficiencyModified from Fernandez and Pascual. 2007 Spe # 108031

Oil Spreading and Film Flow

• Positive Spreading Coefficient is a Function of Interfacial Tension Between Fluids

• The Larger the Spreading Coefficient the lower the Sro .

• High Spreading Coefficient Reduced So by Half.

Maeda and Okats, 2008 SPE 116532

Film flow allows more oil to move out of the pore.

Film Flow Core Test Example

Component Mole %

N2 77.94

CH4 18.91

C2H6 2.24

C3H8 0.91

Core Flood Results

Maeda and Okats, 2008 SPE 116532

S= 31.2

S= 6.2

Low S obtained by adding 1 mole % iso- butanol to brine

CO2 –Water IFT

• CO2- H2 O IFT Decreases Significantly with Increased Pressure

• Temp 78 Degrees F

725 1450 2176 PSIEspinoza and Santamerina, 2009

Polytetrafluroethlene (PTFE)

Deonized H2O, 78 F

CO2 less SolubleCO2 More Soluble

Increased Sweep EfficiencyMobility Ratio “M”

wkM

o

o

w

w

k

k

M

ow

ow

kkM

Immiscible CO2

Immiscible CO2 results in a cumulative effect of reducing the mobility ratio

Immiscible CO2 Flooding Examples• Core Studies• Field Examples

IWAG Core Studies• Immiscible CO2-Methane WAG on Core• Sor Reduced To 13 %• Over 20% Reserve Growth

SPE # 89360, Fernandez, et, al., 2004

Core Flood Experiments Comparing Applications

• Six foot Berea core flooded immiscibly

• IWAG 58% of residual oil recovered

• GAGD, 65% of residual oil recovered

From Rao et al., 2004

Gas Displacement Recovery Immiscible Reserve Growth Applications

• Gas Assisted Gravity Drainage• Immiscible DisplacementGas cap gasOil reservoir IWAG

• Huff n Puff• Pressure Maintenance

– Pressure maintenance condensate and retrograde condensate reservoirs

– oil reservoirs• Mixed Gas ApplicationsDriving agent for slug/bufferMixed gases for density control

Gas Assisted Gravity Drainage (GAGD) Field Examples

• Mauddud Field, Bahrain, GAGD Obtained Reserve Growth from 25% to 41 % of OOIP “16%” increase (Kantzas et al., 1993)

• Oseberg Field, Gas Injection w/o water flood• Coulummes-Vancouriois field, France (Denoyelle et al., 1986)

– N2 after CO2, well in pattern displayed a 4 fold production increase– 14 Mscf/STB Utilization was recorded

• Alberta Pinnacle Reef Floods (Wizard Lake, Westpem Nisku D), Reserve Growth of 15-40% OOIP. (Howes, B. J., 1988)

• West Hackberry, LA, Reported 30% OOIP Reserve Growth• Others include; Weeks Island, Bay St Elaine, Intisar Libia,

Handil, Borneo, Samaria Field Mexico, Cantarell• Hawkins, Tx, Exxon, Greater than 80% Recovery Efficiency

Immiscible Floods and Pilots• Dodan Field, Turkey, Turkish Pet.,

• 60 MMSCF/D ( 1998 production)• Carbonate reservoir, at 1,500 m (4,900 ft) depth• 9- 15 API, 300 -1000 cp

• Lick Creek Field• Ss, Arkansas, after 5 years CO2 injection = 14.1 BSCF & 1 MM STB oil

produced.• 17 API, 160 cp

• Willmington Field pilots• Fault block 3 tar zone• Fault Block 5, 14 API, 180-410 CP demonstrated incremental tertiary oil recovery

• Ritchie Field• Arkansas, CO2 utilization 6.0 Mscf/STB,• 16 API, 195 cp

• Huntington Beach Field• 14 API, 177 cp oil

• Denbury Resources, Mississippi USA• Brage Oil Field, Fensfjord Formation, (Skauge, A., and Berg, E., 1997)

From Ma and Youngren,1994 SPE # 28602

Kuparuk River IWAG Example• Production Results, 10 to 20% OOIP Increase

0

5

10

20

15

25

30

35

40

Summary/Conclusions• Reserve Growth Development is like playing Horse-

shoes, Close Scores You Points!• There are Fundamental Immiscible Displacement

Mechanisms that Produce Reserve Growth in Watered- out Rocks– Oil Swelling– Viscosity Reduction– 3 Phase Relative Permeability (Kr effects)– Improved Volumetric Sweep Efficiency

Summary/Conclusions• Experimental Data Indicates Why Immiscible Gas

Displacement Works– Immiscible Core Studies– Immiscible micro models– Immiscible simulations

• Fluid Characteristics Matter– Interfacial tension between fluids– Under Saturated and Heavy Oil Examples

• Wetability of The Rock Controls the 3• Pilot and Field Applications Have Proven Immiscible

Displacement

Thank You