A LABORATORY STUDY OF FOAM FOR EOR IN NATURALLY FRACTURED RESERVOIRS William R. Rossen Bander. I. AlQuaimi
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
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
Gravity Model Fracture aperture size 4
Gravity Model Fracture Correlation Length 5
Gravity Experimental Setup 6
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
Gravity Trapping and of gas (no foam) Desaturation-experiment example (16x10 cm image) 8
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
Gravity and Propagation 1. In-situ 2. Pre-generated 10
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
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
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
Gravity 0.65X0.40 cm image, f g = 0.37, and u t = 0.0021 m/s 2.2X1.5 cm image, f g = 0.25, and u t = 0.0021 m/s Snap-off Leave-Behind 14
Gravity 0.0 s 1 1 0.083 s 0.117 s 0.150 s 2 3 4 0.84X0.64 cm image, f g = 0.88 u t = 0.0021 m/s, and t = 0.15s Lamella Division 15
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
Gravity Injection Benchmark 3000 Pressure gradient, mbar/m 2500 2000 1500 1000 500 0 ~0 72 Gas Injection (No water) 278 Water Injection Water + Gas (fg = (No gas) 0.37) ut = 0.0021 m/s 2389 (fg = 0.37) 17
Gravity Quality Scan 3000 Pressure gradient,mbar/m 2500 2000 1500 1000 500 7 3 1 5 8 6 2 4 0 0,00 0,20 0,40 0,60 0,80 1,00 fg (Fixed u t = 0.0021 m/s) 18
Bubble Size Analaysis (fixed u t = 0.0021 m/s) Gravity fg = 0.25 0.75 0.37 0.88 0.52 0.96 Images captured during stabilized pressure drop 27 cm from injection port of Gas Fraction ( Quality) Gas water 19
Bubble Size Analaysis (fixed u t = 0.0021 m/s) Gravity Bubble Size Analaysis (fixed u t = 0.0021 m/s) µ app, pa s 0,045 0,040 5 8 6 1 2 0,035 7 3 0,030 0,025 4 0,020 0,015 0,010 0,005 0 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
Bubble Size Analaysis (fixed u t = 0.0021 m/s) Gravity fg = 0.37 vt = 0.0021 m/s Surfactant Concentration 1% wt Inlet Outlet 1 2 3 0.8 X 0.77 cm Images Distance from in let, mm 20 120 270 Average bubble size, mm 2 0.250 0.138 0.081 Bubble size, std. dev., mm 2 0.205 0.125 0.056 Number of bubbles 165 217 303 Bubble sizes evolve along fracture: entrance effect 21
Gravity 2. Pre-generated 1. Fine-textured foam 2. Coarse-textured foam 22
Gravity 0,045 0,040 0,035 In-situ Generated Pre-generated 400 Micron Pre-generated 7 Micron v t = 0.0021 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
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 = 0.96 0,01 0,001 0,01 Total Superficial U t, m/s shear-thinning rheology 24
Gravity High Quality Osterloh & Jante,(1992) Low Quality two flow regimes 25
Gravity Flow direction Characterized 1.0X0.86 cm image, fg = 0.37 and ut = 0.0021 m/s 9.1X8.9 cm image, fg = 0.92 and ut = 0.0021 m/s high-quality regime: caused by intermittent generation 26
Gravity and Properties in Five Different Model 27
Gravity Model Fracture aperture size 28
Gravity Model Fracture Correlation Length 29
Gravity Sample 5: f g = 0.46, u t = 0.0007 m/s; black is gas and white is water. Image size 1.6X1.6 cm. 1 2 3 4 Section 1 2 3 4 Distance from inlet, mm 60 150 230 360 Average bubble size, mm 2 2.48 0.66 0.60 0.53 Bubble size, std. dev., mm 2 7.84 0.57 0.48 0.36 Number of bubbles 37 160 176 194 30
Gravity Sample 4 f g = 0.70, u t = 0.0016 m/s; black is gas and white is water. Image size 1.4X1.0 cm. 2 3 4 Section 1 2 3 4 Distance from inlet, mm 60 150 230 360 Average bubble size, mm 2 NA 0.36 0.26 0.14 Bubble size, std. dev., mm 2 NA 0.47 0.40 0.16 Number of bubbles NA 207 216 479 31
Gravity 800 Pressure gradient, mbar/m 700 600 500 400 300 200 100 0.0036 m/s 0.0022 m/s 0.0015 m/s 0.0007 m/s two foam-flow regimes 0 0 0,2 0,4 0,6 0,8 1 fg Pressure gradient,mbar/m 1400 1200 1000 800 600 400 200 0.0077 m/s 0.0047 m/s 0.0032 m/s 0.0016 m/s NOT! 0 0 0,2 0,4 0,6 0,8 1 fg 32
Gravity Summary of all fractures: Mobility Reduction Factors 80 70 60 Sample 2 Sample 1 MRF 50 40 30 20 10 Sample 5 Sample 4 Sample 3 0 0 200 400 600 800 aperture d H, µm 33
Gravity Summary of all fractures: Mobility Reduction Factors Correlation Length of Lp, µm 6000 5000 4000 3000 2000 Samples 1, 2 and 3 Sample 4 (increasing dh) Sample 5 (Increasing dh) 787 563 34 137 799 23 116 162 2031 1000 0 0 200 400 600 800 aperture d H, µm MRF 34
Gravity Increase aperture at fixed roughness: two cases 35
Gravity Sample 5 dh = 114.9 µm dh = 144.7 µm dh = 170.1 µm Pressure gradient,mbar/m 600 500 400 300 200 100 0 Wide aperture 0 0,2 0,4 0,6 0,8 1 fg 36
Gravity d H, µm 114.9 144.70 170.10 Average bubble size, mm 2 0.468 0.74 0.943 Standard Deviation, mm 2 0.343 0.438 1.02 No of bubbles 120 55 54 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
Gravity 1200 dh = 51.0 µm dh = 71.9 µm dh = 206.9 µm Pressure gradient,mbar/m 1000 800 600 400 200 Wide aperture 0 0 0,2 0,4 0,6 0,8 1 fg 38
Gravity d H 51.00 71.90 206.9 Average bubble size, mm 2 0.097 0.148 1.37 Standard deviation, mm 2 0.114 0.133 1.32 No. of bubbles 972 750 78 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
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
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 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. 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, 2017. 41
Thank You For Your Attention 42
Gravity Pressure Behavior (Low Quality) 4500 Pressure gradient, mbar/m 4000 3500 3000 2500 2000 1500 1000 Section 1 Section 2 Section 3 Section 4 500 0 0 10 20 30 40 Fracture Volume Injected Total superficial velocity = 0.0021 m/s fg = 0.37 Surfactant Concentration 1% wt 43
Gravity Pressure Behavior (High Quality) 4000 Pressure gradient, mbar/m 3500 3000 2500 2000 1500 1000 500 Section 2 Section 3 0 0 10 20 30 40 Fracture Volume Injected Total superficial velocity = 0.0021 m/s fg = 0.75 Surfactant Concentration 1% wt 44
Gravity 3000 0,08 Pressure gradient,mbar/m 2500 2000 1500 1000 500 ut = 0.0049 ut = 0.0030 ut = 0.0021 ut = 0.0010 µ app, pa s 0,07 0,06 0,05 0,04 0,03 0,02 0,01 ut = 0.0010 ut = 0.0021 ut = 0.0030 ut = 0.0049 0 0,00 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
Characterized 7-Micron Generator Gravity 1.4X1.5 cm image, fg = 0.37, and vt = 0.0021 m/s 46
7-Micron Generator 2500 Gravity 0.70X0.50 cm image v t = 0.0021 m/s Pressure gradient, mbar/m 2000 1500 1000 500 0 0,00 0,20 0,40 0,60 0,80 1,00 fg Distance from in let, mm 20 120 270 360 Average bubble size, mm 2 0.028 0.024 0.028 0.024 Bubble size, std. dev., mm 2 0.060 0.026 0.034 0.028 Number of bubbles 701 677 564 448 47
400-Micron Generator 2500 Gravity 1.21X0.75 cm image v t = 0.0021 m/s Pressure gradient, mbar/m 2000 1500 1000 500 0 0,00 0,20 0,40 0,60 0,80 1,00 fg Distance from in let, mm 20 120 270 360 Average bubble size, mm 2 0.343 0.250 0.107 0.100 Bubble size, std. dev., mm 2 0.439 0.175 0.072 0.068 Number of bubbles 132 227 305 486 48
Gravity Pressure Gradient, mbar/m 3000 2500 2000 1500 1000 500 0 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 3000 2500 2000 1500 1000 500 0 0,00 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 = 0.31 0,18 0,16 0,14 0,12 0,10 0,08 0,06 0,04 0,02 Average bubble size, mm2 Pressure Gradient, mbar/m 2500 2000 1500 1000 500 0,20 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 = 0.51 49
Gravity Horizontal flow Vertical flow 2500 Pressure gradient, mbar/m 2000 1500 1000 500 0 0,00 0,20 0,40 0,60 0,80 1,00 f g 50