以煤层气、致密砂岩气和页岩气共生为特征的煤系"三气"是一类重要的非常规天然气资源,但我国目前尚未实现规模性共采。煤系"三气"地质条件客观存在的六大基本特点,一方面提供了优越的气源及其保存条件,另一方面造成多套流体压力系统叠置共生,共采兼容性问题突出,常规措施难以解决这一技术难题。控制叠置含气系统共采兼容性的核心地质条件在于2个方面:一是流体能量差异影响到含气系统之间的兼容性;二是不同储层力学性质和孔渗条件差异影响到系统内部共采兼容性。研究认为,层序地层格架、流体能量系统和岩石力学性质是影响叠置含气系统兼容性的3个关键地质要素;实现煤系"三气"共探与共采的基础是对相关地质问题的深刻理解,对共生特性及其共采地质动态的深入阐释则是贯穿煤系"三气"共采工艺优化和技术创新的主线。煤系"三气"共采工艺技术优化和创新的途径,需要以充分释放产能为目标,以叠置含气系统共采兼容性为约束条件。为此,叠置含气系统共采兼容性未来探索方向,集中在关键层高分辨识别、地层流体及能量高分辨识别、共采兼容性定量表征、开发地质单元与开发方式4个方面。

Three gases in coal series,including coalbed methane (CBM),tight sandstone gas and shale gas,are impor- tant unconventional gas resources,but their large scale mining has not been realized in China. Six basic geological characteristics of the“three gases”,on the one hand,provide a superior gas source and preservation condition,and,on the other hand,result in outstanding co-mining compatibility,which originates from the superposed coexistence of mul- tiple sets of fluid pressure systems and could not been resolved with conventional measures. Key geological controls of the compatibility among the superposed gas-bearing system (SGS) are represented as the compatibility from the fluid energy difference among the systems and from the difference of the mechanical properties,pore and permeability of va- rious reservoirs inside the system. It is considered that the sequence stratigraphic framework,fluid energy system and rock mechanics properties are three key factors affecting the compatibility. Foundation for the “three gases”co-explora- tion and co-mining is to understand profoundly the relevant geological controls,and the main approach for the optimiza- tion and innovation of co-mining technology is to expound deeply the geological dynamics during the joint mining, which need to take the compatibility as a constraint condition for the full release of the production capacity in SGS. To this end,the future investigation of the compatibility should be focused on some aspects,such as the high-resolution recognition of key strata and fluid energy system,the quantitative characterization of the compatibility,and the geolog- ical units and model of the “three gases” development.