Insights into in-situ imbibition behavior of fracturing fluid in propped shale fractures based on nuclear magnetic resonance:A case study from Longmaxi Formation shale,Sichuan Basin,China  

作　　者：Jing-Jing Guo Kai-Xiang Di Lie-Hui Zhang Yu-Long Zhao Hui-Ying Tang Rui-Han Zhang Ye Tian 

机构地区：[1]National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu,610500,Sichuan,China

出　　处：《Petroleum Science》2024年第1期410-429,共20页石油科学（英文版）

基　　金：The authors gratefully acknowledge the support of the National Natural Science Foundation of China(Grant Nos.52174036,51774243,51904257,51874251);the Sichuan Province Science and Technology Program(Grant Nos.2021YJ0345,2022JDJQ0009,2022NSFSC0186).

摘　　要：Shale gas is an important component of unconventional oil and gas resources.Studying the imbibition behavior is helpful to optimize flowback parameters and enhance gas recovery.Recent imbibition studies have focused on shale matrix,and the pressure conditions discussed were mostly atmospheric.The initial imbibition behavior begins from propped fractures to matrix,but there are few studies working on explaining the imbibition behavior in propped fractures or the phenomenon of many shale wells exhibit higher productivity after a“soaking”period.Therefore,propped fracture samples were designed for imbibition and migration experiments.In order to accurately study the mechanism and main influencing factors of fracturing fluid imbibition and migration in propped and unpropped shale fractures under high temperature and high pressure,a series of experiments based on nuclear magnetic resonance(NMR)were carried out.Results showed that NMR T_(2) spectra of all samples exhibited a bimodal distribution.The final imbibition volume of fracturing fluid was positively related to pressure and fracture width.The imbibition effect of fracturing fluid was more evident in matrix pores under high pressure.In the migration during soaking stage,the fracturing fluid gradually migrated from large pores to small pores and gradually displaced the shale gas from the matrix,thus allowing the water blocking in propped fractures to self-unlock to some extent.Gas permeability decreased in the imbibition stage,while it recovered in the migration stage to some extent.

关 键 词：Forced imbibition Migration SOAKING NMR T_(2)spectra Propped fracture Permeability recovery 

分 类 号：TE311[石油与天然气工程—油气田开发工程]