Threshold Pore Pressure Gradients in Water-Bearing Tight Sandstone Gas Reservoirs

Yong Wang, Yunqian Long, Yeheng Sun, Shiming Zhang, Fuquan Song and Xiaohong Wang
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Yong Wang: Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230026, Anhui, China
Yunqian Long: School of Petrochemical & Energy Engineering, Zhejiang Ocean University, Zhoushan 316022, Zhejiang, China
Yeheng Sun: Exploration and Development Research Institute, Shengli Oilfield Company, SINOPEC, Dongying 257015, Shandong, China
Shiming Zhang: Exploration and Development Research Institute, Shengli Oilfield Company, SINOPEC, Dongying 257015, Shandong, China
Fuquan Song: School of Petrochemical & Energy Engineering, Zhejiang Ocean University, Zhoushan 316022, Zhejiang, China
Xiaohong Wang: Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230026, Anhui, China

Energies, 2019, vol. 12, issue 23, 1-13

Abstract: Tight gas reservoirs commonly occur in clastic formations having a complex pore structure and a high water saturation, which results in a threshold pressure gradient (TPG) for gas seepage. The micropore characteristics of a tight sandstone gas reservoir (Tuha oilfield, Xinjiang, China) were studied, based on X-ray diffraction, scanning electron microscopy and high pressure mercury testing. The TPG of gas in cores of the tight gas reservoir was investigated under various water saturation conditions, paying special attention to core permeability and water saturation impact on the TPG. A mathematical TPG model applied a multiple linear regression method to evaluate the influence of core permeability and water saturation. The results show that the tight sandstone gas reservoir has a high content of clay minerals, and especially a large proportion of illite–smectite mixed layers. The pore diameter is distributed below 1 micron, comprising mesopores and micropores. With a decrease of reservoir permeability, the number of micropores increases sharply. Saturated water tight cores show an obvious non-linear seepage characteristic, and the TPG of gas increases with a decrease of core permeability or an increase of water saturation. The TPG model has a high prediction accuracy and shows that permeability has a greater impact on TPG at high water saturation, while water saturation has a greater impact on TPG at low permeability.

Keywords: tight sandstone gas reservoirs; pore structure; threshold pressure gradient; nonlinear seepage; water saturation (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: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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