1. China Coal Research Institute,Beijing　 100013,China; 2. Xi’ an Research Institute of China Coal Technology & Engineering Group Corp. ,Xi’ an　710077,China

在煤层气井生产中,生产周期性波动现象在顾桥井田地面煤层气井排采过程中被观测到,是何原因导致这种现象的产生以及如何进行预防,目前国内外还鲜有报道,开展这一问题的深入研究对碎软、低渗煤层高效开发具有重要意义。通过对煤层气井井底流压、地层产气量等生产数据的深入分析,将周期性波动内生产阶段划分为地层产量(井底流压)平稳阶段、地层产量(井底流压)下降阶段和地层产量(井底流压)升高阶段3个阶段;从气管线集输、数据采集仪器和煤储层3个角度出发,结合煤储层特征、储层改造及修井作业结果,分析得到气阻效应是导致生产周期性波动的主要原因,气阻效应的出现又引起了固阻效应,在两者的综合作用下,导致煤层中流体(水、气)流动不畅,出现生产周期性波动特征,并通过数值模拟方法验证了分析的正确性,最后针对造成生产周期性波动现象的原因,建议在该地区下一步的煤层气开发中,采用煤层顶板岩层代替煤层直接压裂,同时通过表面活性剂的优选、分层控压联合排采技术以及支撑裂缝中煤粉的适度产出等预防措施,达到减小气阻效应和固阻效应的目的。

The cyclical fluctuation phenomenon of the coalbed methane (CBM) production well is observed for the first time in Guqiao Coalfield. What causes this phenomenon and how prevents it,which have not been reported at home and abroad. The analysis of preventive measures and causes of cyclical fluctuation in coalbed methane wells production is of great significance for the efficient development of low permeability and soft broken seam. By the in-depth analysis of bottom hole pressure,the gas production and other production data of the coalbed methane wells,the cycle is divided into the stationary stage of production output (bottom hole flowing pressure),the declining stage of production output (bottom hole flowing pressure) and the increasing stage of production output ( bottom hole flowing pressure). Based on gas line gathering,data acquisition instrument and coal reservoir,combined with the coal reservoir characteristics,reservoir stimulation and work over,it shows that the gas resistance effect which leads to the solid effect is the main cause of the production cyclical fluctuation phenomenon. Cyclical fluctuation characteristics occur,as the consequence of the blockade to fluid (water and gas) flow caused by the gas resistance effect and the solid resistance effect,which is also verified by numerical simulation method. Some suggestions are put forward to reduce the air resistance and solid resistance effect,including using the coal seam roof fracturing instead of directly coal seam fracturing,optimizing sur- face active agent,adopting drainage technique of hierarchical control pressure,and producing properly coal fines of propped fracture,etc. .

FAN Yao,ZHANG Qun. Cause analysis and preventive measures of cyclical fluctuation of coalbed methane production wells in Guqiao coalfield[J]. Journal of China Coal Society,2018,43(5):1373-1380.