煤层气低产井高压氮气闷井增产改造技术与应用  

Study and application of stimulation technology for low production CBM well through high pressure N2 Injection-soak

作　　者：曹运兴 石玢 周丹 吴海明 刘同吉 田林 曹永恒 贾猛 CAO Yunxing;SHI Bin;ZHOU Dan;WU Haiming;LIU Tongji;TIAN Lin;CAO Yongheng;JIA Meng(Gas Geology and Engineering Research Center,Henan Polytechnic University,Jiaozuo 454000,China;Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region,Henan Province,Henan Polytechnic University,Jiaozuo 454000,China;Henan Arks New Energy Company Limited,Jiaozuo 454000,China;Hebei Huabei Petroleum Tian Cheng Industrial Group Co.Ltd.,Renqiu 062552,China;Shanxi Lu’an Mining Group Ltd.,Changzhi 046200,China)

机构地区：[1]河南理工大学煤层气/瓦斯地质工程研究中心,河南焦作454000 [2]中原经济区煤层(页岩)气河南省协同创新中心,河南焦作454000 [3]河南方舟新能源股份有限公司,河南焦作454000 [4]河北华北石油天成实业集团有限公司,河北任丘 062552 [5]山西潞安矿业(集团)有限责任公司,山西长治046200

出　　处：《煤炭学报》2019年第8期2556-2565,共10页Journal of China Coal Society

基　　金：山西省科技重大专项资助项目(20111101002)

摘　　要：我国煤层气储层地质条件复杂,低产煤层气井普遍存在。低产井增产改造是中国煤层气行业迫切需要破解的重大理论和瓶颈技术难题。本文所研究的低产井是指投产后经过一个时期排采生产,储层水和煤层气已经大量产出,气产量较低的生产井。这类低产井的一个重要储层属性是双低压特征,即低水压和低气压。针对这类双低压低产井,研究开发了高压氮气闷井储层保护型增产改造技术,并在潞安矿区余吾井田进行了工程试验,获得了预期增产效果。余吾井田山西组3号煤层区域上为低压低渗储层,煤层气井的产量普遍偏低。两口试验井LA-011和LA-016于2008年投产,经过4 a的排采生产,平均日产量只有31 m 3 /d和20 m 3 /d;两井各进行过一次水力压裂二次改造,增产效果仍不明显。两口井试验前的储层压力梯度只有1.0 kPa/m左右,具有典型的低压低产特征。高压氮气闷井增产改造试验于2012年10月进行,分别泵注高压氮气34 800 m 3 和 44 960 m 3 ,泵注结束后关井闷压92 h和112 h,在井口压力降低到1.0 MPa以下时开井排采。在高压氮气闷井期间,实时监测了试验井周边邻井的套压变化,分析高压氮气在煤层中的运移方向,试验结束后进行了1~3 a的排采生产。结果表明:①在高压氮气泵注阶段,位于不同方向邻井的套压不同程度升高,这一方面表明高压氮气具有区域性面状穿透扩展和造缝现象,并清晰指示了高压氮气在煤层中的造缝穿透运移方向,而且高压氮气新生裂缝扩展方向不再受控于原始的区域地应力场方向,主要与排采后均化的局部地应力场有关。②试验前后同一时间段的产量对比表明,氮气闷井改造具有“单井改造,多井增产”的区域性增产效果:即2井(LA-011和LA-016)改造,受到影响的5口井(LA-011,LA-016,LA-013,LA-014和LA-015)同时增产。③增产效果显著,两口试验井日产气增加1.2~8.9倍,3口邻�In China,coal reservoirs are complex and under-performance CBM wells are widely distributed.To develop a novel theory and technology for stimulating these wells again for increasing gas rate is very important for CBM enterprises and the industry.After a long time water drainage and gas production,the reservoir is characterized as low gas pressure and low water pressure,even in dry condition.For re-stimulating these low productive CBM wells meanwhile protecting the sensitive low pressure or dry reservoir,a nitrogen ECBM technology named nitrogen injection-soak (NIS) was developed and tested in two CBM wells located in Yuwu coal mine of Luan mining area,Shanxi Province,China,and some desired results were obtained.The objective reservoir coal No.3 has low pressure and low permeability,and the gas production is generally low in the study area.The two experimental wells LA-011 and LA-016 started pump and production in 2008.Four years production result shown that the average gas rate was only 31 m 3/d and 20 m 3/d .The two wells have been re-stimulated with hydraulic fracturing in 2010,but no desired result reached.The reservoir pressure gradient of the two wells before the current experiment was only 1.0 kPa/m,which were two typical low pressure and low productivity wells.The stimulation trial of NIS was carried out in October 2012.The nitrogen amounted to 34 800 m 3 and 44 960 m 3 were pumped into LA-011 and LA-016,and shut-in times was 92 h and 112 h respectively,then the wells were opened for drainage when the wellhead pressure was lower than 1.0 MPa.During the period of NIS,the casing pressure of adjacent CBM wells was measured for monitoring the nitrogen migration direction in the coal seam.After the NIS experiment,the wells were continually in production for 1 to 3 years.The experiment result shown that:① The casing pressure increase of adjacent wells during injection stage indicates that NIS has a regional stimulation effectiveness,which clearly indicates the migration direction of high pressure nitrogen.The

关 键 词：煤层气 低产井 低压低渗 氮气闷井 增产改造 潞安矿区 

分 类 号：P618.11[天文地球—矿床学]