Investigation of the Combination Mechanism of Spontaneous Imbibition and Water Flooding in Tight Oil Reservoirs Based on Nuclear Magnetic Resonance

Lei Tao (), Longlong Wang, Jiajia Bai (), Na Zhang, Wenyang Shi, Qingjie Zhu, Zhengxiao Xu and Guoqing Wang
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Lei Tao: School of Petroleum Engineering, Changzhou University, Changzhou 213164, China
Longlong Wang: School of Petroleum Engineering, Changzhou University, Changzhou 213164, China
Jiajia Bai: School of Petroleum Engineering, Changzhou University, Changzhou 213164, China
Na Zhang: College of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
Wenyang Shi: School of Petroleum Engineering, Changzhou University, Changzhou 213164, China
Qingjie Zhu: School of Petroleum Engineering, Changzhou University, Changzhou 213164, China
Zhengxiao Xu: School of Petroleum Engineering, Changzhou University, Changzhou 213164, China
Guoqing Wang: School of Petroleum Engineering, Changzhou University, Changzhou 213164, China

Energies, 2024, vol. 17, issue 3, 1-18

Abstract: As conventional oil reservoirs are gradually being depleted, researchers worldwide are progressively shifting their focus towards the development and comprehensive study of tight oil reservoirs. Considering that hydraulic fracturing is one of the main approaches for developing tight sandstone reservoirs, it is of great significance to explore the mechanism of spontaneous imbibition and waterflooding behavior after hydraulic fracturing in tight oil reservoirs. This research delves into the analysis of tight sandstone core samples obtained from the Shahejie Formation in the Bohai Bay Basin. All core samples are used for a series of experiments, including spontaneous imbibition and water flooding experiments. An additional well-shut period experiment is designed to understand the impact and operational dynamics of well shut-in procedures in tight reservoir development. Utilizing nuclear magnetic resonance (NMR) technology, the pore sizes of a sample are divided into three types, namely, macropores (>100 ms), mesopores (10–100 ms), and micropores (<10 ms), to thoroughly assess the fluid distribution and changes in fluid signals during the spontaneous imbibition and water flooding stages. Experimental outcomes reveal that during the spontaneous imbibition stage, oil recovery ranges from 12.23% to 18.70%, predominantly depending on capillary forces. The final oil recovery initially rises and then falls as permeability decreases, while the contribution of micropores progressively grows as the share of mesopores and macropores deceases. With water flooding processes carried out after spontaneous imbibition, enhanced oil recovery is observed between 28.26% and 33.50% and is directly proportional to permeability. The well shut-in procedures can elevate the oil recovery to as high as 47.66% by optimizing energy balance.

Keywords: tight sandstone; spontaneous imbibition; water flooding; nuclear magnetic resonance; well shut-in (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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