煤系“三气”单井筒合采可行性分析——基于现场试验井的讨论

摘要

煤层气、致密砂岩气和页岩气(三气)在含煤地层叠置共生,能否实现同井筒合采,决定了煤系非常规天然气的开发效率和技术攻关方向.从分析“三气”赋存特征入手,结合鄂尔多斯盆地东缘临兴地区煤层气和致密砂岩气合采试验井生产情况,探讨了“三气”合采可行性.结果表明:“三气”高效产出的关键在于利用机抽设备排出地层产出液,逐步降低井底流压;持续合采过程中单层的气、水产出对其他层位没有干扰;但停排时,由于不同产层能量衰竭程度不同,动液面上升会产生地层水倒灌导致低压层伤害.根据现场试验,“三气”合采是可行的,各产层类似江河支流向干流流动或电路并联形式存在,进入井筒后协同产出,即“储层并联,气水串联,井下检测、井上控制”.今后工作需进一步研究合适的修井工艺防止停井过程中储层伤害.%Coalbed methane,tight sand gas and shale gas (three gases) are superimposed in coal measures,and whether achieving co-production successfully from on well bore determines the development efficiency and technology research direction of unconventional natural gases in coal measures.The paper discusses the co-production feasibility of "three gases",based on the analysis of "three gases" occurrence characteristics and the status of coalbed methane and tight sand gas co-production test wells in Linxing area,east margin of Ordos Basin.The results show that the key for efficient co-production of "three gases" is to discharge the water from stratus by pumping equipment,and decrease the bottom hole pressure gradually.During the continuous production process,the gas and water production from one layers showed no influence to other layers.However,when the production stopped,the working water level may arise and flush into low-pressure strata due to differences in reduction degree of strata energies.Based on the field test,it can be concluded that the co-production of "three gases" is feasible,and different reservoirs show a form of river tributaries flow into the main stream or circuit parallel connection with gases being produced together when going into the well bores.The above is "parallel reservoirs combination with synergetic gas and water flow,downhole monitoring with wellhead controlment".The further researches should be focused on studying appropriate workover process to prevent reservoir damage during well stops.