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Pore‐scale simulation of density‐driven convection in fractured porous media during geological CO 2 sequestration
Author(s) -
Chen Cheng,
Zhang Dongxiao
Publication year - 2010
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2010wr009453
Subject(s) - brine , carbon sequestration , instability , convection , porous medium , dissolution , lattice boltzmann methods , carbon dioxide , geology , convective mixing , porosity , mineralogy , environmental science , petrology , soil science , atmospheric sciences , mechanics , chemistry , geotechnical engineering , physics , organic chemistry
Global warming is attributed to the excessive emission of greenhouse gases, one of whose main components is carbon dioxide (CO 2 ). A promising long‐term solution for mitigating global warming is geological CO 2 sequestration, which is the capture and storage of enormous amounts of CO 2 in underground reservoirs in order to reduce CO 2 build up in the atmosphere. In this study, a pore‐scale lattice Boltzmann method was used to simulate density‐driven convection in a porous medium with a fracture, to study geological CO 2 sequestration in deep saline aquifers. The CO 2 ‐brine interface was located at the top of the domain. Both fracture width and body force were varied to generate different Ra numbers in order to investigate the effect of Ra on the convection. All simulated data can be fitted by the same trend, implying that the characteristic length of the system was dominated by the fracture width. When Ra was high enough, increasing Ra did not reduce the critical time for the onset of instability apparently. Also, it did not increase the maximum peak vertical velocity noticeably. Therefore, there existed asymptotic values for the critical time and maximum peak vertical velocity. With high Ra numbers, the high‐frequency oscillation of turbulence greatly enhanced the dissolution of CO 2 into brine. After the onset of convective instability, the brine with a high CO 2 concentration intruded into the underlying unaffected brine, which increased the interfacial area between the CO 2 ‐rich brine and unaffected brine, and consequently favored the migration of CO 2 into the fracture and porous medium. This study is the first pore‐scale one investigating density‐driven convection during geological CO 2 sequestration in deep saline aquifers, whereas most existing research is focused on the field scale and the dissolved CO 2 concentration at the top boundary is usually assumed to be saturated.