The use of PDMS micromodels to study CO 2 foam transport in porous media
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Transcript of The use of PDMS micromodels to study CO 2 foam transport in porous media
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
Reservoir conditions for multi-phase flow
1. Image Source: U.S. Department of Energy2. Image Source: www.slb.com/Schlumberger
WettabilityWettabilityStructureStructure
Pores1 and vugs2 in reservoir rock
3. Chilingar, G. V.; Yen, T. F., Energy Sources 1983, 7, (1), 67-75.
Wettability of carbonate reservoir rocks (water contact angle,161 samples1)
Microchannels in porous media
1. Source: http://www.oil-gas-news.com2. Source: this study
Microfluidics in EOR process1 Bubble break-up in microchannels2
Goals of this work
1. To tune and pattern wettability in micromodels;
2. To investigate foam flow in heterogeneous porous media.
500 μm
Microchannel and photolithography
Silicon wafer
Silicon wafer
PDMS
PDMS
Photoresist
SU-8 photoresist mold
PDMS curing on SU-8 mold
PDMS after peeling it off the mold1. Cubaud, T., U. Ulmanella, and C.M. Ho, Fluid
Dynamics Research, 2006. 38(11): p. 772-786.
PDMS surface modification by UV-Ozone
1. Berdichevsky Y, et al, Sensors and Actuators B-Chemical 2004, 97, (2-3), 402-408.
Ozone[1]
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.
Schematic of the two-step process of wettability control
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.
Design of a heterogeneous micromodel
2.57 cm
1.19 cm
Foam generator
Porous medium
Foam generator
150 μm
surfactant
surfactant
gas bubbles
Heterogeneous porous media
Low permeable layer: grain radius 50 μm; pore throat 20 μm; porosity 0.45.
High permeable layer: grain radius 150 μm; pore throat 60 μm; porosity 0.45.
100% air injection to dye solution
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.
CO2 is only able to flow through the high permeability region leaving the aqueous solution trapped in the low permeability region
90% air injection to dye solution
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.
Adding surfactant to the foam allows the aqueous solution to be swept from both the high and low permeability regions
Image processing by MATLAB
Only targeting the aqueous (green dye) solution
Coworked with Dichuan Li, Rice University.
Comparison of saturation profiles
1.1 sec (gas breakthrough)
2.7 sec (gas breakthrough)
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.
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