柳林地区煤层气勘探开发模式研究

Exploration and Development Model of Coalbed Methane in Liulin Area,China

柳林地区是全国煤层气开发先导示范区,勘探开发技术逐渐完善。基于区域地质规律,分析了煤层气组成、地应力和地温场特点以及不同储层的差异;结合开发方案和技术选择,从开发效果、开发层位、钻完井设计等方面进行了规律探究。山西组煤层气CH4含量、兰氏体积和含气饱和度均较太原组高;地应力和地温场在垂向上呈现分带,以700～850m埋深最小水平主应力最高,地层呈挤压状态;不同煤层物性差异大,水动力变化是层间矛盾的主要因素。在开发效果上,山西组直井较太原组好,太原组产水量普遍较高;水平井产能效果最好,且产量相对稳定。钻井设计中创新性地采用双煤层多分支水平井,充分调用了资源潜力。在煤层气勘探开发实践中,以平衡产能为导向,由地应力、地温场和储层压力3个要素组成地质能量内循环,激励渗透率、产气量和产水量组成的响应外循环;同时以合理的气水排采制度控制内循环,其中钻井和储层改造是释放产能的驱动,合理的排采方案是维系开发平衡的驱动。

Liulin area is one of the key coalbed methane（CBM）development areas in China.Based on the regional geology analysis,the CBM composition,in-situ stress and geo-temperature field,and reservoir differences were illustrated.Additionally,the CBM well development effect,pumped layers choice,and well drilling technologies were systematically discussed.Results show that,the CH4 content,Langmuir volume and gas saturation of Shanxi Formation are higher than those of the Taiyuan Formation.In-situ stress and geotemperature field show vertical belting,and the 700 mto 850mdepth are the minimum horizontal principal stress.The coal properties are different from each other,and the hydrodynamic condition contributes much to the reservoiring difference.Vertical wells which penetrate coals in Shanxi Formation show better gas rate,while in Taiyuan Formation they are of higher water rate.Double-step and multi-branch horizontal wells were adopted,resulting in the full use of coals and better gas rate.Two cycles are proposed,including the inner cycle composed of in-situ stress,geo-temperature and reservoir pressure,and the outer cycle of permeability,gas rate and water rate.During CBM production,the inner cycle stimulates the outer cycle,while the reservoir reconstruction promotes the capability release and well production system maintains production balance.