Normalization of Relative-Permeability Curves of Cores in High-Water-Content Tight Sandstone Gas Reservoir

Bo Hu, Jingang Fu (), Wenxin Yan, Kui Chen and Jingchen Ding
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Bo Hu: Sinopec North China Petroleum Bureau, Zhengzhou 450006, China
Jingang Fu: School of Petroleum and Natural Gas Engineering, Chongqing University of Science and Technology, Shapingba, Chongqing 401331, China
Wenxin Yan: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Kui Chen: Sinopec North China Petroleum Bureau, Zhengzhou 450006, China
Jingchen Ding: Sinopec North China Petroleum Bureau, Zhengzhou 450006, China

Energies, 2025, vol. 18, issue 9, 1-17

Abstract: The gas–water relative-permeability relationship in tight gas is complex due to interactions between the gas and water phases within the porous media in the reservoir. To clarify the fluid occurrence and the gas–water relative-permeability behavior in such reservoirs, the Dongsheng tight water-bearing reservoir from the Ordos Basin of China is taken as the research object. A non-steady state method is employed to explore the co-permeability of gas and water phases under dynamic conditions. The irreducible water saturation of different core samples is analyzed using nuclear magnetic resonance (NMR) centrifugation. The Simplified Stone equation is applied for phase permeability normalization. The results indicate that with the decrease in core permeability, the irreducible water saturation increases, and the gas and water permeability decreases. When the displacement pressure difference increases, the gas phase permeability decreases, and the water phase permeability increases. The centrifugal method is effective in reducing the saturation of bound water in rock cores. The displacement method forms channels using gas, which effectively removes free water, particularly in larger or smaller pores. In contrast, centrifugation further displaces water from smaller or capillary pores, where flow is more restricted. Based on these experimental findings, a relationship between displacement pressure difference, critical irreducible water saturation, and residual gas saturation is established. The Stone equation is further refined, and a phase permeability normalization curve is proposed, accounting for the true irreducible water saturation of rock. This provides a more accurate theoretical framework for understanding and managing the gas–water interaction in tight gas reservoirs with a high water content, ultimately aiding in the optimization of reservoir development strategies.

Keywords: tight sandstone gas reservoir; gas–water relative permeability; irreducible water saturation; normalization (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: 2025
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