Investigation of the Pore Characteristics and Capillary Forces in Shale before and after Reaction with Supercritical CO 2 and Slickwater

Chi Zhang, Qian Li (), Yanlin Liu, Jiren Tang, Yunzhong Jia and Tianyi Gong
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Chi Zhang: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Qian Li: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Yanlin Liu: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Jiren Tang: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Yunzhong Jia: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Tianyi Gong: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

Energies, 2024, vol. 17, issue 16, 1-19

Abstract: CO 2 –slickwater hybrid fracturing technology is an essential part of shale gas recovery and CO 2 geo-storage. However, the exposure to supercritical CO 2 (ScCO 2 ) and slickwater can result in potential changes of the pore structures and surface wetting behavior, which affect the gas transportation and CO 2 sequestration security in shale reservoirs. Therefore, in this paper, X-ray diffraction (XRD), low-pressure nitrogen gas adsorption (N 2 GA), mercury intrusion porosimetry (MIP), and fractal analysis were used to describe the pore characteristics of shale before and after ScCO 2 –slickwater coupling treatments. Shale’s surface wettability was confirmed by contact angle measurements. After the ScCO 2 –slickwater treatments, the number of micropores (<3.5 nm) and mesopores (3.5–50 nm) increased, while that of macropores (>50 nm) declined based on the N 2 GA and MIP experiments. Combined with fractal analysis, we argue that the pore connectivity diminished and the pore structure became more complicated. By analyzing the results of XRD, shale pore changes occurring after the ScCO 2 –slickwater treatment can be explained by the adsorption of polyacrylamide (PAM). Contact angle measurement results showed that the shale’s surface treated by ScCO 2 and slickwater was more hydrophilic than that treated by ScCO 2 and water, and indirectly prove our argument above. Hence, the coupling using effect of ScCO 2 and slickwater can impair the negative effect of CO 2 on the shale capillary force to improve shale gas productivity, but it can negatively affect the security of CO 2 sequestration in shale reservoirs.

Keywords: shale; pore structure; supercritical carbon dioxide; slickwater; CO 2 sequestration (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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