A LABORATORY STUDY OF FOAM FOR EOR IN NATURALLY FRACTURED RESERVOIRS. William R. Rossen Bander. I. AlQuaimi

Transcription

1 A LABORATORY STUDY OF FOAM FOR EOR IN NATURALLY FRACTURED RESERVOIRS William R. Rossen Bander. I. AlQuaimi

2 Gravity 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 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 P c Low-Quality regime: thought to reflect invariant bubble size, roughly size of pores Fractured reservoirs have especially poor sweep efficiency generation in fractures is uncertain 2

3 Gravity 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 3

4 Gravity Model Fracture aperture size 4

5 Gravity Model Fracture Correlation Length 5

6 Gravity Experimental Setup 6

7 Initial Study: Trapping and in 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, [k p/σ] 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? 7

8 Gravity Trapping and of gas (no foam) Desaturation-experiment example (16x10 cm image) 8

9 Gravity Trapping and New N ca Conventional Nca NN cccc = kk γγccccccθθ NN cccc = PPkk ff γγ 12 2 dd t dd HH 2 LLgg dd t 1 1 dd t dd b 1,20 1,20 Normalized air saturation 1,00 0,80 0,60 0,40 0,20 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Normalized air saturation 1,00 0,80 0,60 0,40 0,20 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 0,00 0,00 1,E-05 1,E-04 1,E-03 1,E-02 1,0E-03 1,0E-02 1,0E-01 1,0E+00 Nca Nca Force balance on trapped ganglion leads to new N ca for fractures 9

10 Gravity and Propagation 1. In-situ 2. Pre-generated 10

11 Gravity 12,0 10,0 9 cm 40 cm 9 cm Q, ml/min 8,0 6,0 4,0 2,0 P2 P3 0,0 0,0 20,0 40,0 60,0 80,0 ΔP, mbar 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 11

12 Gravity 1. In-situ Can we generate foam, in-situ, in a fracture? How effective is it in reducing gas mobility in the fracture? 12

13 Gravity 1. In-situ Can we generate foam, in-situ, in a fracture? generated in our model fracture by mechanisms similar to 3D porous media 13

14 Gravity 0.65X0.40 cm image, f g = 0.37, and u t = m/s 2.2X1.5 cm image, f g = 0.25, and u t = m/s Snap-off Leave-Behind 14

15 Gravity 0.0 s s s s X0.64 cm image, f g = 0.88 u t = m/s, and t = 0.15s Lamella Division 15

16 Gravity 1. In-situ Can we generate foam, in-situ, in a fracture? How effective is it in reducing gas mobility in the fracture? 16

17 Gravity Injection Benchmark 3000 Pressure gradient, mbar/m ~0 72 Gas Injection (No water) 278 Water Injection Water + Gas (fg = (No gas) 0.37) ut = m/s 2389 (fg = 0.37) 17

18 Gravity Quality Scan 3000 Pressure gradient,mbar/m ,00 0,20 0,40 0,60 0,80 1,00 fg (Fixed u t = m/s) 18

19 Bubble Size Analaysis (fixed u t = m/s) Gravity fg = Images captured during stabilized pressure drop 27 cm from injection port of Gas Fraction ( Quality) Gas water 19

20 Bubble Size Analaysis (fixed u t = m/s) Gravity Bubble Size Analaysis (fixed u t = m/s) µ app, pa s 0,045 0, , ,030 0, ,020 0,015 0,010 0, ,35 0,30 0,25 0,20 0,15 0,10 0,05 0,000 0,00 0,00 0,20 0,40 0,60 0,80 1,00 fg Average Bubble Size, mm 2 mobility inversely related to bubble size 20

21 Bubble Size Analaysis (fixed u t = m/s) Gravity fg = 0.37 vt = m/s Surfactant Concentration 1% wt Inlet Outlet X 0.77 cm Images Distance from in let, mm Average bubble size, mm Bubble size, std. dev., mm Number of bubbles Bubble sizes evolve along fracture: entrance effect 21

22 Gravity 2. Pre-generated 1. Fine-textured foam 2. Coarse-textured foam 22

23 Gravity 0,045 0,040 0,035 In-situ Generated Pre-generated 400 Micron Pre-generated 7 Micron v t = m/s µ app, pa s 0,030 0,025 0,020 might local-equilibrium value lie between { pre-generated and in-situ-generated? 0,015 0,010 0,005 0,000 0,00 0,20 0,40 0,60 0,80 1,00 fg 23

24 Gravity 0,1 y = 0,0003x -0,806 y = 0,0001x -0,899 y = 0,0002x -0,815 y = 0,0002x -0,765 µ app, pa s fg = 0.24 fg = 0.51 fg = 0.88 fg = ,01 0,001 0,01 Total Superficial U t, m/s shear-thinning rheology 24

25 Gravity High Quality Osterloh & Jante,(1992) Low Quality two flow regimes 25

26 Gravity Flow direction Characterized 1.0X0.86 cm image, fg = 0.37 and ut = m/s 9.1X8.9 cm image, fg = 0.92 and ut = m/s high-quality regime: caused by intermittent generation 26

27 Gravity and Properties in Five Different Model 27

28 Gravity Model Fracture aperture size 28

29 Gravity Model Fracture Correlation Length 29

30 Gravity Sample 5: f g = 0.46, u t = m/s; black is gas and white is water. Image size 1.6X1.6 cm Section Distance from inlet, mm Average bubble size, mm Bubble size, std. dev., mm Number of bubbles

31 Gravity Sample 4 f g = 0.70, u t = m/s; black is gas and white is water. Image size 1.4X1.0 cm Section Distance from inlet, mm Average bubble size, mm 2 NA Bubble size, std. dev., mm 2 NA Number of bubbles NA

32 Gravity 800 Pressure gradient, mbar/m m/s m/s m/s m/s two foam-flow regimes 0 0 0,2 0,4 0,6 0,8 1 fg Pressure gradient,mbar/m m/s m/s m/s m/s NOT! 0 0 0,2 0,4 0,6 0,8 1 fg 32

33 Gravity Summary of all fractures: Mobility Reduction Factors Sample 2 Sample 1 MRF Sample 5 Sample 4 Sample aperture d H, µm 33

34 Gravity Summary of all fractures: Mobility Reduction Factors Correlation Length of Lp, µm Samples 1, 2 and 3 Sample 4 (increasing dh) Sample 5 (Increasing dh) aperture d H, µm MRF 34

35 Gravity Increase aperture at fixed roughness: two cases 35

36 Gravity Sample 5 dh = µm dh = µm dh = µm Pressure gradient,mbar/m Wide aperture 0 0,2 0,4 0,6 0,8 1 fg 36

37 Gravity d H, µm Average bubble size, mm Standard Deviation, mm No of bubbles Images are captured in section 4, fixed f g of 0.45, and bubbles at the edges are excluded Images are identical in size (1.1X0.86 cm) Larger aperture bigger bubbles 37

38 Gravity 1200 dh = 51.0 µm dh = 71.9 µm dh = µm Pressure gradient,mbar/m Wide aperture 0 0 0,2 0,4 0,6 0,8 1 fg 38

39 Gravity d H Average bubble size, mm Standard deviation, mm No. of bubbles Images are captured in section 4, fixed f g of 0.45, and bubbles at the edges are excluded Images are identical in size (1.7X1.5 cm) Larger aperture bigger bubbles 39

40 Summary and Conclusions generation was observed in the model fractures, mainly by capillary snap-off and lamella division. Hydraulic aperture alone is not enough to determine foamgeneration and mobility reduction. 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 P c *. Bubbles were smaller than pore size in low-quality regime. With fixed roughness, pressure gradient decreases with increasing hydraulic aperture. bubbles became larger as aperture increases. 40

41 Reports and Publications The dissertation has details on both the N ca and foam experiments and analysis and is available online. Search for AlQuaimi at 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), AlQuaimi, B. I., Rossen,W. R. (2017), Capillary Desaturation Curve for Residual Nonwetting Phase in Natural. Accepted by SPE Journal. AlQuaimi, B. I., and Rossen, W. R., "Characterizing Flow in for Enhanced Oil Recovery," presented at the EAGE IOR Symposium, Stavanger, April 24-27,

42 Thank You For Your Attention 42

43 Gravity Pressure Behavior (Low Quality) 4500 Pressure gradient, mbar/m Section 1 Section 2 Section 3 Section Fracture Volume Injected Total superficial velocity = m/s fg = 0.37 Surfactant Concentration 1% wt 43

44 Gravity Pressure Behavior (High Quality) 4000 Pressure gradient, mbar/m Section 2 Section Fracture Volume Injected Total superficial velocity = m/s fg = 0.75 Surfactant Concentration 1% wt 44

45 Gravity ,08 Pressure gradient,mbar/m ut = ut = ut = ut = µ app, pa s 0,07 0,06 0,05 0,04 0,03 0,02 0,01 ut = ut = ut = ut = ,00 0,20 0,40 0,60 0,80 1,00 fg 0 0 0,2 0,4 0,6 0,8 1 fg u t Δ P u t µ app 45

46 Characterized 7-Micron Generator Gravity 1.4X1.5 cm image, fg = 0.37, and vt = m/s 46

47 7-Micron Generator 2500 Gravity 0.70X0.50 cm image v t = m/s Pressure gradient, mbar/m ,00 0,20 0,40 0,60 0,80 1,00 fg Distance from in let, mm Average bubble size, mm Bubble size, std. dev., mm Number of bubbles

48 400-Micron Generator 2500 Gravity 1.21X0.75 cm image v t = m/s Pressure gradient, mbar/m ,00 0,20 0,40 0,60 0,80 1,00 fg Distance from in let, mm Average bubble size, mm Bubble size, std. dev., mm Number of bubbles

49 Gravity Pressure Gradient, mbar/m Pressure Gradient Average bubble size 0,20 0,18 0,16 0,14 0,12 0,10 0,08 0,06 0,04 0,02 0,00 0 0,002 0,004 0,006 0,008 Total superfacial velocity, m/s 3000 Pressure Gradient Avergae bubble size, mm2 Pressure Gradient, mbar/m Average bubble size ,00 0 0,001 0,002 0,003 0,004 Total superfacial velocity, m/s 0,25 Pressure Gradient Average bubble size fg = 0.24 fg = ,18 0,16 0,14 0,12 0,10 0,08 0,06 0,04 0,02 Average bubble size, mm2 Pressure Gradient, mbar/m ,20 0,15 0,10 0,05 Average bubble size, mm2 0 0,00 0 0,002 0,004 0,006 Total superfacial, m/s fg =

50 Gravity Horizontal flow Vertical flow 2500 Pressure gradient, mbar/m ,00 0,20 0,40 0,60 0,80 1,00 f g 50