A study on the flowability of gas displacing water in low-permeability coal reservoir based on NMR technology

作     者：Minfang Yang Zhaobiao Yang Bin Sun Zhengguang Zhang Honglin Liu Junlong Zhao Minfang YANG;Zhaobiao YANG;Bin SUN;Zhengguang ZHANG;Honglin LIU;Junlong ZHAO

作者机构：Department of UnconventionalsResearch Institute of Petroleum Exploration and DevelopmentPetroChinaLangfang065007China Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process(Ministry of Education)China University of Mining and TechnologyXuzhou221008China School of Resource and GeosciencesChina University of Mining and TechnologyXuzhou221116China 

出 版 物：《Frontiers of Earth Science》 (地球科学前沿（英文版）)

年 卷 期：2020年第14卷第4期

页      面：673-683页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：Financial support for this work was provided by the National Natural Science Foundation of China(Grant No.41772155) the Advanced Basic Research Projects of China National Petroleum Corporation(2019B-4910) 

主　　题：coalbed methane low-permeability coal reservoir NMR gas displacing water flowability pore size 

摘      要：Flowability of gas and water through low-permeability coal plays crucial roles in coalbed methane(CBM)recovery from coal *** better understand this phenomenon,experiments examining the displacement of water by gas under different displacement pressures were systematically carried out based on nuclear magnetic resonance(NMR)technology using low-permeability coal samples of medium-high coal rank from Yunnan and Guizhou,*** results reveal that both the residual water content(W_(r))and residual water saturation(S_(r))of coal gradually decrease as the displacement pressure(P)*** P is 0-2 MPa,the decline rates of W_(r) and S_(r) are fastest,beyond which they slow down *** samples with higher permeability exhibit higher water flowability and larger decreases in W_(r) and S_(r).Compared with medium-rank coal,high-rank coal shows weaker fluidity and a higher proportion of irreducible *** relationship between P and the cumulative displaced water content(W_(c))can be described by a Langmuir-like equation,W_(c)=WLP/(PL+P),showing an increase in W_(c) in coal with an increase in *** the low-pressure stage from 0 to 2 MPa,W_(c) increases most rapidly,while in the high-pressure stage(P2 MPa),W_(c) tends to be *** minimum pore diameter(d′)at which water can be displaced under different displacement pressures was also *** d′value decreases as P increases in a power relationship;i.e.,d′the coal gradually decreases with the gradual increase in ***,the d′values of most of the coal samples are close to 20 nm under a P of 10 MPa.