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Determination of contact angles for three-phase flow in porous media using an energy balance

DOI: 10.1016/j.jcis.2020.07.152 DOI Help

Authors: Martin J. Blunt (Imperial College London) , Abdulla Alhosani (Imperial College London) , Qingyang Lin (Imperial College London) , Alessio Scanziani (Imperial College London) , Branko Bijeljic (Imperial College London Department of Earth Science and Engineering)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Colloid And Interface Science , VOL 582 , PAGES 283 - 290

State: Published (Approved)
Published: September 2020

Open Access Open Access

Abstract: Hypothesis: We define contact angles, h, during displacement of three fluid phases in a porous medium using energy balance, extending previous work on two-phase flow. We test if this theory can be applied to quantify the three contact angles and wettability order in pore-scale images of three-phase displacement. Theory: For three phases labelled 1, 2 and 3, and solid, s, using conservation of energy ignoring viscous dissipation ðDa1s cos h12  Da12  /j12 DS1 Þr12 1⁄4 ðDa3s cos h23 þ Da23  /j23 DS3 Þr23 þ Da13 r13 , where / is the porosity, r is the interfacial tension, a is the specific interfacial area, S is the saturation, and j is the fluid–fluid interfacial curvature. D represents the change during a displacement. The third contact angle, h13 can be found using the Bartell-Osterhof relationship. The energy balance is also extended to an arbitrary number of phases. Findings: X-ray imaging of porous media and the fluids within them, at pore-scale resolution, allows the difference terms in the energy balance equation to be measured. This enables wettability, the contact angles, to be determined for complex displacements, to characterize the behaviour, and for input into pore-scale models. Two synchrotron imaging datasets are used to illustrate the approach, comparing the flow of oil, water and gas in a water-wet and an altered-wettability limestone rock sample. We show that in the water-wet case, as expected, water (phase 1) is the most wetting phase, oil (phase 2) is inter- mediate wet, while gas (phase 3) is most non-wetting with effective contact angles of h12 % 48 and h13 % 44, while h23 1⁄4 0 since oil is always present in spreading layers. In contrast, for the altered-wettability case, oil is most wetting, gas is intermediate-wet, while water is most non-wetting with con- tact angles of h12 1⁄4 134 $ 10;h13 1⁄4 119 $ 10, and h23 1⁄4 66 $ 10.

Journal Keywords: Contact angle; Imaging; Wettability; Multiphase flow in porous media; Curvature; Three-phase flow

Subject Areas: Earth Science, Physics

Instruments: I13-2-Diamond Manchester Imaging