区域构造与演化控制下煤层气富集高产典型模式

煤层气勘探开发对改善我国能源结构、解决煤矿灾害与生态环境问题意义重大。结合我国区域构造与演化过程及煤层气地质条件，将煤层气富集产气模式划分为4种主要类型:构造简单裂隙系统、褶皱系统(较浅向斜轴部、褶皱翼部、次级构造高部位)、冲断构造系统(褶皱冲断带、高陡冲断构造)和构造叠加系统模式。其中，(1) 构造简单裂隙系统模式发育在构造相对稳定的地区，煤层气以深成热成因为主，也可受岩浆热接触作用影响，在裂隙中等发育区形成高产富集区。(2) 褶皱系统模式中，较浅向斜轴部挤压应力利于煤层气保存从而富集产气；褶皱翼部压力分布均匀，封闭性较好，其含气量与渗透率匹配适中形成富集高产带；次级构造高部位模式主要是在构造作用下形成的伴生构造(背斜、鼻隆构造、断块等)高部位形成构造圈闭，生成“气顶”。(3) 冲断构造系统模式中，褶皱冲断带模式中逆冲断层阻止了煤层气的逸散，在靠近逆冲断层的相对构造高点富集产气；高陡冲断构造模式发育在复杂断裂区，深部煤层气在一定温压作用下，解吸游离至上部地层，重新被吸附或部分仍呈游离状态而富集产气。(4) 构造叠加系统模式形成于受多期构造活动共同作用的煤储层中，不同的应力方向和机制引起的构造叠加使含气量和渗透率相匹配，煤层气富集且有一定产量。因此，区域构造特征控制着煤层气富集产气的每个模式，构造演化过程决定了富集产气的不同模式。这些富集产气模式对系统认识中国煤层气富集规律，指导“十四五”煤层气勘探开发具有重要意义。 

Typical coalbed methane (CBM) enrichment and production modes under the control of regional structure and evolution

Coalbed methane (CBM) exploration and development is of great significance to optimize China’s energy structure and cope with coal mine disasters and ecological environment problems. In this paper, combined with regional structure and evolution and CBM geological conditions, the enrichment and recovery modes of CBM are innovatively divided into four categories: simple structural fracture system, fold system (shallower synclinal shaft, fold limb, secondary structural high position), thrust system (fault-thrust-fold belt, high-steep thrust structure) and structural superposition system. Among them, simple structural fracture system mode is often encountered in the areas with relatively stable structure, where the CBM is mainly derived from deep thermogenesis, and can also be reformed by magma thermal contact, forming high-yield enrichment zones with moderately developed fracture. In the fold system mode, the extrusion stress at the shallower synclinal shaft is conducive to the preservation of CBM. The fold limbs with uniform pressure distribution and superior sealing performance are compatible with both gas content and permeability, thus forming high-yield enrichment zones. The secondary structural high position mode refers to the structural traps formed in the high part of the associated structures (anticlines, nose-shaped uplift, fault blocks, etc.) under compression, which generate “gas cup”. In the fault-thrust-fold belt mode, the thrust fault prevents the escape of CBM, and captures gas at the relative structural high position close to the thrust fault. The high-steep thrust structure mode is developed in the complex fault area. Subjected to the specific temperature and pressure fields, the desorbed deep CBM migrates to the upper strata, and is re-adsorbed or partially still in a free state and accumulated. The structural superposition system mode, in contrast to single main control mode, is formed in the coal reservoirs affected by multi-stage tectonic movements. The structural superposition caused by different stress directions and mechanisms superposition achieves optimal matching of gas content and permeability, which is also favorable for CBM enrichment. Therefore, regional structural characteristics control the mode of CBM enrichment and recovery, which is fundamentally determined by tectonic evolution. Conclusions drawn in this study are of great reference value to systematically understanding the law of CBM enrichment in China and guiding the exploration and exploitation of CBM during the 14th Five-Year Plan.