煤层气开发解吸系统及其开采特征

Desorption system and its production behavior of coalbed methane development

煤层气开发靠排水降压采气,解吸系统的划分有利于提高煤层气田整体开发效果。笔者根据我国复杂断块气田地质特征为主的煤层气开发现状分析,针对不同气藏地质条件和由开采工艺造成的不同开采效果,将纵向上开采中能形成相互干扰的一套煤层或多套煤层,平面上一个断块或多个小断块、小圈闭,通过断层、陷落柱、煤矿采空、采动区应力释放或通过煤层压裂、煤层钻水平井等将煤层沟通,形成开采中井间干扰的地区划分为同一个解吸系统。通过典型解吸系统开采特征分析,认为以解吸系统为开发单元:有利于在煤层气开发中合理划分开发层系和开发单元;有效整体控制各井降液速率,实现构造高部位井以产气为主,低部位井以排水降压为主;有利于进行开发动态分析与开发方案调整;有利于优化井位部署,提高煤层气采收率和开发效果。

Water needs to be depleted to develop coalbed methane( CBM),the classification of desorption system is beneficial to enhance the overall development effect of CBM fields. Based on the production status of the CBM field with complex fault blocks,geological conditions of different gas reservoir and development effect caused by production technology in China,the desorption system was defined as one or several sets of coal seams vertically which can be mutual interference during development and one or multiple small fault blocks or small traps horizontally where reservoirs are connected through faults,collapse-columns,stress relief of goafs and mining areas,hydraulic fracturing and horizontal wells drilling. According to the production behavior analysis of typical desorption systems,several benefits of taking desorption system as the development units are recognized which include dividing development strata and units reasonably,controlling the depletion rate of production wells effectively to realize the fact of mainly gas production in wells in the structural high and water production in wells in the structural low,conducting dynamic analysis,adjusting development programs,optimizing well deployment,and enhancing CBM recovery and development effect.