Combined Effects of CO 2 Adsorption-Induced Swelling and Dehydration-Induced Shrinkage on Caprock Sealing Efficiency

Xiaoji Shang, Jianguo Wang (), Huimin Wang and Xiaolin Wang
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Xiaoji Shang: State Key Laboratory for Geomechanics & Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China
Jianguo Wang: State Key Laboratory for Geomechanics & Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China
Huimin Wang: College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
Xiaolin Wang: School of Engineering, University of Tasmania, Hobart 7001, Australia

IJERPH, 2022, vol. 19, issue 21, 1-22

Abstract: Carbon dioxide (CO 2 ) may infiltrate into the caprock and displace brine water in the caprock layer. This causes two effects: one is the caprock swelling induced by the CO 2 adsorption and the other is the caprock dehydration and shrinkage due to CO 2 –brine water two-phase flow. The competition of these two effects challenges the caprock sealing efficiency. To study the evolution mechanism of the caprock properties, a numerical model is first proposed to investigate the combined effects of CO 2 adsorption-induced expansion and dehydration-induced shrinkage on the caprock sealing efficiency. In this model, the caprock matrix is fully saturated by brine water in its initial state and the fracture network has only a brine water–CO 2 two-phase flow. With the diffusion of CO 2 from the fractures into the caprock matrix, the CO 2 sorption and matrix dehydration can alter the permeability of the caprock and affect the entry capillary pressure. Second, this numerical model is validated with a breakthrough test. The effects of the two-phase flow on the water saturation, CO 2 adsorption on the swelling strain, and dehydration on the shrinkage strain are studied, respectively. Third, the permeability evolution mechanism in the CO 2 –brine water mixed zone is investigated. The effect of dehydration on the penetration depth is also analyzed. It is found that both the shale matrix dehydration and CO 2 sorption-induced swelling can significantly alter the sealing efficiency of the fractured caprock.

Keywords: CO 2 geological sequestration; brine water-CO 2 two-phase flow; matrix dehydration; caprock swelling; permeability evolution (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
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