A LABORATORY STUDY OF FOAM FOR EOR IN NATURALLY … faculteit... · 2020. 8. 10. · Foam Generation Velocity Effect Roughness Effect Aperture Effect Gravity Effect Goals and Strategy

A LABORATORY STUDY OF FOAM FOR EOR IN NATURALLY FRACTURED RESERVOIRS

William R. RossenBander. I. AlQuaimi

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CharacterizedFractures

Trapping & Mobilization

Foam Generation

VelocityEffect

RoughnessEffect

Aperture Effect Gravity Effect

Backround

• Gas‐injection EOR can displace nearly all oil contacted, but sweep efficiency is very poor, because of reservoir heterogeneity, gravity segregation and viscous instability

• Foam can help fight all three causes of poor gas sweep• In reservoir rock, foam shows two flow regimes:• High‐Quality regime: result of foam collapse at limiting Pc

• Low‐Quality regime: thought to reflect invariant bubble size, roughly size of pores

• Fractured reservoirs have especially poor sweep efficiency

• Foam generation in fractures is uncertain

3



Foam Generation

VelocityEffect

RoughnessEffect


Goals and Strategy

• Develop rules for foam generation and properties in fractures that would apply broadly to fractures of different apertures, different geometries.

• Conduct studies in a medium where foam can be directly observed. • Conduct experiments on samples as large as possible (avoid entrance effects).

• Obtain a variety of samples with very different fracture apertures, permeabilities, and scales of roughness

Implementation• Conduct experiments in model fractures between glass plates, one

roughened, one smooth • large size, cost effective, and available in different geometries

4



Foam Generation

VelocityEffect

RoughnessEffect


Model Fracture aperture size

5



Foam Generation

VelocityEffect

RoughnessEffect


Model Fracture Correlation Length

6



Foam Generation

VelocityEffect

RoughnessEffect


Experimental Setup

7

Initial Study: Trapping and Mobilization in Fractures

• Trapping and mobilization of bubbles is a key to foam mobility.

• Trapping and mobilization of non‐wetting phase in rock is represented as function of capillary number, [kp/]

• In fractures, permeability k is primarily a function of average aperture, but trapping depends on roughness

• What is best definition of capillary number for trapping in fractures?

8



Foam Generation

VelocityEffect

RoughnessEffect


Desaturation‐experiment example (16x10 cm image)

Trapping and Mobilization of gas (no foam)

9



Foam Generation

VelocityEffect

RoughnessEffect


Trapping and Mobilization

𝑁𝑘 𝛻𝑃𝛾𝑐𝑜𝑠𝜃

Conventional Nca

New Nca

𝑁𝛻𝑃𝑘𝛾

122

𝑑𝑑

𝐿𝑔𝑑

1

1 𝑑𝑑

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,E‐05 1,E‐04 1,E‐03 1,E‐02

Normalized

air saturatio

n

Nca

Sample 1

Sample 2

Sample 3

Sample 4

Sample 5

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,0E‐03 1,0E‐02 1,0E‐01 1,0E+00

Normalized

air saturatio

n

Nca

Sample 1

Sample 2

Sample 3

Sample 4

Sample 5

Force balance on trapped ganglion leads to new Nca for fractures

10



Foam Generation

VelocityEffect

RoughnessEffect


Foam Generation and Propagation

1. In-situ Foam Generation

2. Pre-generated Foam

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Foam Generation

VelocityEffect

RoughnessEffect


0,0

2,0

4,0

6,0

8,0

10,0

12,0

0,0 20,0 40,0 60,0 80,0

Q, m

l/min

ΔP, mbar

P2

P3

• First model : narrow aperture, regular pattern• Single‐phase water injection to determine

hydraulic aperture• Two inner ports used for pressure gradient• The hydraulic aperture estimated to be 66 µm

40 cm

9 cm9 cm

12



Foam Generation

VelocityEffect

RoughnessEffect


1. In‐situ Foam Generation• Can we generate foam, in-situ, in a

fracture?

• How effective is it in reducing gas mobility in the fracture?

13



Foam Generation

VelocityEffect

RoughnessEffect



fracture?Foam generated in our model fracture by mechanisms similar to “3D” porous media

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Foam Generation

VelocityEffect

RoughnessEffect


2.2X1.5 cm image, fg = 0.25, and ut = 0.0021 m/s0.65X0.40 cm image, fg = 0.37, and ut = 0.0021 m/s

Snap‐off Leave‐Behind

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Foam Generation

VelocityEffect

RoughnessEffect


1

2 3 4

0.150 s0.117 s0.083 s

0.0 s

1

0.84X0.64 cm image, fg = 0.88 ut = 0.0021 m/s, and t = 0.15s

Lamella Division

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Foam Generation

VelocityEffect

RoughnessEffect



fracture?

• How effective is it in reducing gas mobility in the fracture?

17



Foam Generation

VelocityEffect

RoughnessEffect


~0 72278

2389

0

500

1000

1500

2000

2500

3000

Gas Injection (Nowater)

Water Injection(No gas)

Water + Gas (fg =0.37)

Foam (fg = 0.37)

Pressure gradien

t, mbar/m

ut = 0.0021 m/s

Foam Injection Benchmark

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Foam Generation

VelocityEffect

RoughnessEffect


Foam Quality Scan

1

23

4

567

8

0

500

1000

1500

2000

2500

3000

0,00 0,20 0,40 0,60 0,80 1,00

Pressure gradien

t ,mba

r/m

fg

(Fixed ut = 0.0021 m/s)

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Foam Generation

VelocityEffect

RoughnessEffect


Foam Bubble Size Analaysis (fixed ut = 0.0021 m/s)

fg = 0.25

0.37

0.52

0.75

0.88

0.96

Images captured during stabilized pressure drop 27 cm from injection port

Gaswater

Effect of Gas Fraction (Foam Quality)

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Foam Generation

VelocityEffect

RoughnessEffect




71 2

3

4

5 6

0

8

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,000

0,005

0,010

0,015

0,020

0,025

0,030

0,035

0,040

0,045

0,00 0,20 0,40 0,60 0,80 1,00

AverageBu

bbleSize, m

m2

µ app, p

a s

fg

Foam mobility inversely related to bubble size

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Foam Generation

VelocityEffect

RoughnessEffect


Foam Bubble Size Analaysis (fixed ut = 0.0021 m/s)Foam Bubble Size Analaysis

fg = 0.37 vt = 0.0021 m/s Surfactant Concentration 1% wt

0.8 X 0.77 cm Images

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Inlet Outlet

Distance from in let, mm 20 120 270

Average bubble size, mm2 0.250 0.138 0.081

Bubble size, std. dev. , mm2 0.205 0.125 0.056

Number of bubbles 165 217 303

Bubble sizes evolve along fracture: “entrance effect”

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Foam Generation

VelocityEffect

RoughnessEffect


2. Pre‐generated Foam

1. Fine‐textured foam

2. Coarse‐textured foam

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Foam Generation

VelocityEffect

RoughnessEffect


0,000

0,005

0,010

0,015

0,020

0,025

0,030

0,035

0,040

0,045

0,00 0,20 0,40 0,60 0,80 1,00

µ app, p

a s

fg

In‐situ Generated Pre‐generated 400 Micron Pre‐generated 7 Micron

vt = 0.0021 m/s

{might local‐equilibrium value lie between pre‐generated and in‐situ‐generated?

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Foam Generation

VelocityEffect

RoughnessEffect


y = 0,0001x‐0,899y = 0,0003x‐0,806

y = 0,0002x‐0,815

y = 0,0002x‐0,765

0,01

0,1

0,001 0,01

µ app, p

a s

Total Superficial Velocity Ut, m/s

fg = 0.24fg = 0.51fg = 0.88fg = 0.96

shear‐thinning rheology

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Foam Generation

VelocityEffect

RoughnessEffect


Low Quality

High QualityOsterloh & Jante,(1992)

two flow regimes

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Foam Generation

VelocityEffect

RoughnessEffect


1.0X0.86 cm image, fg = 0.37and ut = 0.0021 m/s

9.1X8.9 cm image, fg = 0.92and ut = 0.0021 m/s

Flow

dire

ction

high‐quality regime: caused by intermittent generation

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Foam Generation

VelocityEffect

RoughnessEffect


Foam Generation and Propertiesin Five Different Model Fractures

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Foam Generation

VelocityEffect

RoughnessEffect


Model Fracture aperture size

29



Foam Generation

VelocityEffect

RoughnessEffect


Model Fracture Correlation Length

30



Foam Generation

VelocityEffect

RoughnessEffect


Section 1 2 3 4

Distance from inlet, mm 60 150 230 360

Average bubble size, mm2 2.48 0.66 0.60 0.53

Bubble size, std. dev. , mm2 7.84 0.57 0.48 0.36

Number of bubbles 37 160 176 194

1 3 42

Sample 5: fg = 0.46, ut = 0.0007 m/s; black is gas and white is water. Image size 1.6X1.6 cm.

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Foam Generation

VelocityEffect

RoughnessEffect


Sample 4 fg = 0.70, ut = 0.0016 m/s; black is gas and white is water. Image size 1.4X1.0 cm.

Section 1 2 3 4

Distance from inlet, mm 60 150 230 360

Average bubble size, mm2 NA 0.36 0.26 0.14

Bubble size, std. dev. , mm2 NA 0.47 0.40 0.16

Number of bubbles NA 207 216 479

2 3 4

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Foam Generation

VelocityEffect

RoughnessEffect


0

200

400

600

800

1000

1200

1400

0 0,2 0,4 0,6 0,8 1

Pressure gradien

t,mba

r/m

fg

0.0077 m/s

0.0047 m/s

0.0032 m/s

0.0016 m/s

0

100

200

300

400

500

600

700

800

0 0,2 0,4 0,6 0,8 1

Pressure gradien

t, mba

r/m

fg

0.0036 m/s

0.0022 m/s

0.0015 m/s

0.0007 m/s

two foam‐flow regimes

NOT!

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Foam Generation

VelocityEffect

RoughnessEffect


Summary of all fractures: Mobility Reduction Factors

Sample 4

Sample 2

Sample 5

Sample 3

Sample 1

0

10

20

30

40

50

60

70

80

0 200 400 600 800

MRF

dH, µmaperture

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Foam Generation

VelocityEffect

RoughnessEffect


Summary of all fractures: Mobility Reduction Factors

787

2031

563

34

23

799137

162116

0

1000

2000

3000

4000

5000

6000

0 200 400 600 800

Lp, µ

m

dH, µm

Samples 1, 2 and 3 Sample 4 (increasing dH)Sample 5 (Increasing dH)

MRF

aperture

Correlation Length of R

oughne

ss

35



Foam Generation

VelocityEffect

RoughnessEffect


Increase aperture at fixed roughness: two cases

36



Foam Generation

VelocityEffect

RoughnessEffect


0

100

200

300

400

500

600

0 0,2 0,4 0,6 0,8 1

Pressure gradien

t ,mba

r/m

fg

dH = 114.9 µm dH = 144.7 µm dH = 170.1 µm

Sample 5

Wide aperture

37



Foam Generation

VelocityEffect

RoughnessEffect


• Images are captured in section 4, fixed fg of 0.45, and bubbles at the edges are excluded• Images are identical in size (1.1X0.86 cm)

dH, µm 114.9 144.70 170.10

Average bubble size , mm2 0.468 0.74 0.943

Standard Deviation, mm2 0.343 0.438 1.02

No of bubbles 120 55 54

Larger aperture bigger bubbles

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Foam Generation

VelocityEffect

RoughnessEffect


0

200

400

600

800

1000

1200

0 0,2 0,4 0,6 0,8 1

Pressure gradien

t ,mba

r/m

fg

dH = 51.0 µm dH = 71.9 µm dH = 206.9 µm

Wide aperture

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Foam Generation

VelocityEffect

RoughnessEffect


• Images are captured in section 4, fixed fg of 0.45, and bubbles at the edges are excluded• Images are identical in size (1.7X1.5 cm)

dH 51.00 71.90 206.9

Average bubble size, mm2 0.097 0.148 1.37

Standard deviation, mm2 0.114 0.133 1.32No. of bubbles 972 750 78

Larger aperture bigger bubbles

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Summary and Conclusions

• Foam generation was observed in the model fractures, mainly by capillary snap‐off and lamella division.

• Hydraulic aperture alone is not enough to determine foam‐generation and mobility reduction. Roughness scale, both laterally and vertically, plays a significant role. Slit‐shaped throats & wet conditions favor snap‐off.

• Bubble size was inversely related to pressure gradient, as expected• Shear‐thinning behaviour was observed as velocity increases.• Two flow regimes were observed in 2 cases out of 3. However, the

high‐quality regime evidently reflected reduced and fluctuating generation, not collapse of foam at limiting capillary pressure Pc*. Bubbles were smaller than pore size in low‐quality regime.

• With fixed roughness, pressure gradient decreases with increasing hydraulic aperture. Foam bubbles became larger as aperture increases.

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Reports and Publications

• The dissertation has details on both the Nca and foam experiments and analysis and is available online. Search for AlQuaimi at

https://www.tudelft.nl/en/library/

• Journal and Conference Publications• AlQuaimi, B. I., Rossen, W. R. (2017), New capillary number definition

for displacement of residual nonwetting phase in natural fractures.Geophys. Res. Lett., 44 (11), 5368–5373.

• AlQuaimi, B. I., Rossen,W. R. (2017), Capillary Desaturation Curve for Residual Nonwetting Phase in Natural Fractures. Accepted by SPE Journal.

• AlQuaimi, B. I., and Rossen, W. R., "Characterizing Foam Flow in Fractures for Enhanced Oil Recovery," presented at the EAGE IOR Symposium, Stavanger , April 24‐27, 2017.

Thank YouFor Your Attention

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A LABORATORY STUDY OF FOAM FOR EOR IN NATURALLY … faculteit... · 2020. 8. 10. · Foam Generation Velocity Effect Roughness Effect Aperture Effect Gravity Effect Goals and Strategy