延川南区块属于深层高阶煤煤层气藏,埋深800~1 500 m、煤阶为贫煤—无烟煤、含气量超过12 m³/t,资源条件有利,但气田单井产能平面差异大。基于气田地质条件综合研究,通过构造对储层生烃、孔渗性、水文地质条件、煤体结构、煤层气赋存的影响性分析,开展构造对煤层气成藏控制作用机理研究,查明煤层气成藏的构造主控因素及其变化规律。结合煤层气开发动态资料,分析区块构造与煤层气井产能的关系,建立煤层气井产能的构造控气模式。研究结果表明,煤层埋深控制了储层的含气性、渗透性,埋深越深,含气性越好,渗透性越差,构造对煤层气富集成藏的主控作用具有两面性,局部褶皱和断层的发育对渗透性具有明显的改善作用,有利于气藏富集,但是构造活动过强,会导致水动力条件增强,煤层气逸散。构造对气井产能的控制作用明显,高产井主要分布于埋深830~1 280 m的局部微幅隆起带翼部的煤层气富集和渗透率改善区,中产井主要分布于埋深大于1 280 m、构造平缓、断层不发育的低渗区;低产井主要分布于构造破坏严重的局部洼陷区以及断层发育带附近的煤层气逸散区。

The southern Yanchuan Block is a deep, high-rank coal-bed methane reservoir with large buried depth at 800~1 500 m, meagre coal or anthracite, and good gas content at 12 m³/t. The resource conditions are relatively favorable, but the single well productivity level of the gas field varies greatly. Based on the comprehensive study of gas field geological conditions, and by the analysis of the influence of structure on reservoir hydrocarbon generation, porosity and permeability, hydrogeological conditions, coal body structure, and CBM storage, the researches on the control mechanism of structure on CBM reservoir formation are carried out to find out the main controlling factors of coal seam formation and its changing rules. Combined with the CBM development dynamic data, the relation between block structure and CBM well productivity is analyzed, and a structural gas control mode for CBM well productivity is established. The research results show that the buried depth of the coal seam controls the gas-bearing and permeability of the reservoir. The deeper the buried, the better the gas-bearing and the worse the permeability. The control effect of tectonic activities on the formation of coal-bed methane has two sides, the local folds and the development of faults has a significant effect on improving permeability, which is conducive to the enrichment of gas reservoirs, but the excessive tectonic activity on the other hand will also lead to the enhanced hydrodynamic conditions and the escape of coalbed methane. The structure has an obvious control effect on the gas well productivity. The high-yield wells are mainly distributed in the coalbed methane enrichment and the permeability improvement areas at the wing of the local micro-uplift belt with a buried depth of 830~1 280 m. The middle-production wells are mainly distributed in the low-permeability areas with a buried depth of more than 1 280 m, whose structure is gentle and the faults are not developed. The low-yield wells are mainly distributed in local depression areas with severe structural damage and CBM escape areas near fault development belts.