Wettability of Tight Sandstone Reservoir and Its Impacts on the Oil Migration and Accumulation: A Case Study of Shahejie Formation in Dongying Depression, Bohai Bay Basin

Kunkun Jia, Jianhui Zeng, Xin Wang, Bo Li, Xiangcheng Gao and Kangting Wang
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Kunkun Jia: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Bejing 102249, China
Jianhui Zeng: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Bejing 102249, China
Xin Wang: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Bejing 102249, China
Bo Li: Exploration and Development Institute, Shengli Oilfield Company, SINOPEC, Dongying 257015, China
Xiangcheng Gao: Exploration and Development Institute, Shengli Oilfield Company, SINOPEC, Dongying 257015, China
Kangting Wang: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Bejing 102249, China

Energies, 2022, vol. 15, issue 12, 1-19

Abstract: The migration and accumulation of oil in tight sandstone reservoirs are mainly controlled by capillary force. Due to the small pore radius and complex pore structure of tight sandstone reservoirs, the capillary force is very sensitive to wettability, so wettability significantly affects oil migration and accumulation. However, the study of oil migration and accumulation in tight sandstone reservoirs often needs to combine multiple methods, the process is complex, and the research methods of wettability are not uniform, so the mechanism of wettability affecting oil migration and accumulation is not clear. Taking the tight sandstone of the Shahejie Formation in the Dongying sag, Bohai Bay Basin, as the research object, the wettability characteristics of a tight sandstone reservoir and their influence on oil migration and accumulation were analyzed by means of a pore permeability test, XRD analysis, micro-CT experiment, contact angle tests, spontaneous imbibition experiments, and physical simulation experiments on oil migration and accumulation. The results show that the reservoir is of the water-wet type, and its wettability is affected by the mineral composition. Wettability in turn affects the spontaneous imbibition characteristics by controlling the capillary force. Oil migration in tight sandstone reservoirs is characterized by non-Darcy flow, the oil is in the non-wetting phase and subject to capillary resistance. The key parameters to describe the oil migration and accumulation characteristics include the kickoff pressure gradient, the critical pressure gradient, and ultimate oil saturation. Wettability affects oil migration characteristics by controlling the capillary force. The more oil-wet the reservoir is, the more favourable it is to oil migration and oil accumulation and therefore the higher the reservoir’s ultimate oil saturation is.

Keywords: tight sandstone; wettability; capillary force; oil migration and accumulation (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: 2022
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