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The use of PDMS micromodels to study CO 2 foam transport in porous media

Study on using PDMS micromodels to analyze CO2 foam transport in porous media, tuning wettability, patterning surfaces, and enhancing sweeping with foam in heterogeneous porous media.

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The use of PDMS micromodels to study CO 2 foam transport in porous media

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  1. The use of PDMS micromodels to study CO2 foam transport in porous media Kun Ma, George J. Hirasaki, Sibani Lisa Biswal Department of Chemical & Biomolecular Engineering Rice University, Houston, TX 04/26/2011

  2. Wettability Structure Reservoir conditions for multi-phase flow Wettability of carbonate reservoir rocks (water contact angle,161 samples1) Pores1 and vugs2 in reservoir rock 3. Chilingar, G. V.; Yen, T. F., Energy Sources 1983, 7, (1), 67-75. 1. Image Source: U.S. Department of Energy 2. Image Source: www.slb.com/Schlumberger

  3. Microchannels in porous media Bubble break-up in microchannels2 Microfluidics in EOR process1 • Source: http://www.oil-gas-news.com • Source: this study

  4. Goals of this work • To tune and pattern wettability in micromodels; 2. To investigate foam flow in heterogeneous porous media. 500 μm

  5. Microchannel and photolithography Photoresist Silicon wafer SU-8 photoresist mold PDMS Silicon wafer PDMS curing on SU-8 mold PDMS PDMS after peeling it off the mold • Cubaud, T., U. Ulmanella, and C.M. Ho, Fluid Dynamics Research, 2006. 38(11): p. 772-786.

  6. PDMS surface modification by UV-Ozone [1] Ozone 1. Berdichevsky Y, et al, Sensors and Actuators B-Chemical 2004, 97, (2-3), 402-408.

  7. Wettability control by water immersion Wettability maintenance by keeping UV-ozone-treated PDMS (1-hour curing at 80 °C) surface in contact with DI water.

  8. Schematic of the two-step process of wettability control

  9. An example of wettability patterning (a) Top view of the porous medium in Device A. (b) Top view of the porous medium in Device B. Left: initially saturated with dye solution; Right: after 2 min air injection at a volumetric flow rate of 1.0 ml/hr. The red scale bar at the upper left corner represents 500 μm.

  10. Design of a heterogeneous micromodel 2.57 cm Porous medium 1.19 cm Foam generator

  11. Foam generator surfactant 150 μm bubbles gas surfactant

  12. Heterogeneous porous media High permeable layer: grain radius 150 μm; pore throat 60 μm; porosity 0.45. Low permeable layer: grain radius 50 μm; pore throat 20 μm; porosity 0.45.

  13. 100% air injection to dye solution CO2 is only able to flow through the high permeability region leaving the aqueous solution trapped in the low permeability region Played at 1 frames per second, captured at 10 frames per second. Injected gas flow rate 5.0 ml/hr, injected liquid flow rate 0.0 ml/hr.

  14. 90% air injection to dye solution Adding surfactant to the foam allows the aqueous solution to be swept from both the high and low permeability regions Played at 1 frames per second, captured at 10 frames per second. Injected gas flow rate 4.5 ml/hr, injected liquid (0.2% wt coco betaine) flow rate 0.5 ml/hr.

  15. Image processing by MATLAB Only targeting the aqueous (green dye) solution • Coworked with Dichuan Li, Rice University.

  16. Comparison of saturation profiles 1.1 sec (gas breakthrough) 2.7 sec (gas breakthrough)

  17. Conclusions ★ PDMS-based microfluidic devices provide a facile way to study the effect of wettability and heterogeneity on multi-phase flow in porous media; ★ A simple method has been demonstrated to tune and pattern the wettability of polydimethylsiloxane (PDMS) to generate microfluidic mimics of heterogeneous porous media; ★ Preliminary results in micromodels show that pre-generated foam is able to greatly improve sweep in low permeable region in a heterogeneous porous medium.

  18. Future work • Understand the mechanism of foam propagation in heterogeneous porous media: • permeability dependence • cross flow • effect of surfactants • effect of foam quality • shear thinning effect

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