Three-Water Differential Parallel Conductivity Saturation Model of Low-Permeability Tight Oil and Gas Reservoirs

Xiangyang Hu, Renjie Cheng (), Hengrong Zhang, Jitian Zhu, Peng Chi () and Jianmeng Sun
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Xiangyang Hu: Zhanjiang Branch, CNOOC China Limited, Zhanjiang 524057, China
Renjie Cheng: Zhanjiang Branch, CNOOC China Limited, Zhanjiang 524057, China
Hengrong Zhang: Zhanjiang Branch, CNOOC China Limited, Zhanjiang 524057, China
Jitian Zhu: Zhanjiang Branch, CNOOC China Limited, Zhanjiang 524057, China
Peng Chi: School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China
Jianmeng Sun: School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China

Energies, 2024, vol. 17, issue 7, 1-19

Abstract: Addressing the poor performance of existing logging saturation models in low-permeability tight sandstone reservoirs and the challenges in determining model parameters, this study investigates the pore structure and fluid occurrence state of such reservoirs through petrophysical experiments and digital rock visualization simulations. The aim is to uncover new insights into fluid occurrence state and electrical conduction properties and subsequently develop a low-permeability tight sandstone reservoir saturation model with easily determinable parameters. This model is suitable for practical oilfield exploration and development applications with high evaluation accuracy. The research findings reveal that such reservoirs comprise three types of formation water: strongly bound water, weakly bound water, and free water. These types are found in non-connected micropores, poorly connected mesopores where fluid flow occurs when the pressure differential exceeds the critical value, and well-connected macropores. Furthermore, the three types of formation water demonstrate variations in their electrical conduction contributions. By inversely solving rock electrical experiment data, it was determined that for a single sample, the overall cementation index is the highest, followed by the cementation index of pore throats containing strongly bound water, and the lowest for the pore throats with free water. Building on the aforementioned insights, this study develops a parallel electrical pore cementation index term, ϕ m ′ , to account for the differences among the three types of water and introduces a parallel electrical saturation model suitable for logging evaluation of low-permeability tight oil and gas reservoirs. This model demonstrated positive application effects in the logging evaluation of low-permeability tight gas reservoirs in a specific basin in the Chinese offshore area, thereby confirming the advantages of its application.

Keywords: low-permeability tight sandstone reservoirs; complex pore structure; fluid occurrence state; electrical conductivity properties; logging saturation model (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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