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《Fault-Block Oil & Gas Field》 2014-02
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Experimental evaluation on damage induced by fracturing fluids in tight coal rock gas reservoirs

Kang Yili;Zhou Laicheng;Chi Xiaoming;Li Xiangchen;Chen Defei;Chen Fei;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University;Changqing Downhole Technology Service Company,CNPC Chuanqing Drilling Engineering Co.Ltd.;  
Stimulation is essential for obtaining economic productivity in tight coal rock gas reservoirs.However,the stimulation effect of some coalbed methane wells is far from expected goal because of reservoir damage induced by fracturing fluids after fracturing operation.Domestic and overseas researchers mostly use artificial coal samples suppressed by coal fines to evaluate the formation damage induced by fracturing fluid,which cannot reflect the natural structure characteristics of coal rock reservoirs authenticly.Salt sensitivity and experimental evaluation of fracturing fluids damage were carried out for the tight columnar coal rock in Ningwu Basin.Based on salt sensitivity experiment,1% concentration was ascertained for KCl.The experiment results of fracturing fluids damage show that for the average damage degree,surfactant solution is 46.61%,clear fracturing fluid A is 39.12% and ion balance fracturing fluids is 85.42%.The contact angle decreased after coal samples being exposed to those three kinds of fracturing fluids,and hydrophilism enhanced,as a consequences,fracturing fluids return back difficultly.Whereas coal samples permeability increased by 46.57% and hydrophilism was poorer because of clear fracturing fluid B which shows weak acidity.Through a comprehensive analysis,it is considered that the adsorption of hydrophilic fracturing fluids is the main mechanism of coal rock gas reservoirs damage.Method and awareness have been gained from research,which can provide some references for fracturing fluids design of tight coal rock gas reservoirs.
【Fund】: 国家重点基础研究发展计划(973计划)项目“深井复杂地层漏失与井壁稳定机理及预测”(2010CB226705);; 西南石油大学研究生创新基金资助课题“新型煤层防塌与储层保护钻井完井液技术研究”(GIFSS0709)
【CateGory Index】: TE377
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