新疆后峡盆地侏罗系西山窑组煤层厚20~80m,经历了强烈构造改造,浅于1000m的不同井煤层气含量和产能变化大。为解决煤层气控藏因素问题,开展二维地震构造解释和演化研究,应用叠前地震波阻抗反演预测含气量,分析构造对煤层气成藏的关系。结果表明:燕山和喜山两期冲断造山构造运动使气藏遭受不同程度的破坏,中低阶煤先深后浅演化和压力降低导致煤层吸附气含气饱和度普遍偏低,但由于煤储层对游离气的密闭条件不同,导致含气量变化较大,且含气量与单井产能呈明显的正相关;煤层气成因和包含游离气和吸附气的含气量随构造单元、埋深和地层产状等变化而变化;含气量介于7~13m3/t区域以保存好的热成因气-混合气为主,主要分布在埋深900~2500m凹陷;含气量小于4m3/t地区分布在盆地边缘斜坡和凸起构造上,以次生生物气为主;含气量介于4~7m3/t区域分布在以上二者之间的过渡区;在倾角3°~7°的缓坡含气量高,倾角20°~30°的陡坡或大断距断裂带含气量低。复杂构造对煤层气富集起决定性控制作用并对勘探开发具有重要的参考意义。

The coal seam of Jurassic Xishanyao Formation in Houxia Basin, Xinjiang is generally 20 ~ 80 m thick. Due to the strong tectonic transformation of the intermountain basin, the content of coalbed methane and productivity of different wells shallower than 1 000 m vary greatly. In order to solve the problem of the control factors on coalbed methane, we carried out two-dimensional seismic structural in- terpretation and evolution research, and applied prestack seismic wave impedance inversion to predict gas content, and analyzed the relationship between structure and coalbed methane accumulation. The results show that the Yanshan and Himalayan thrust tectonic movements have caused gas reservoirs to suffer different degrees of damage. The evolution of medium and low rank coal from deep to shallow and the decrease of pressure lead to the generally low gas saturation of adsorbed gas in coal seams. Howev- er, due to the different sealing conditions of coal reservoirs for free gas, the gas content changes greatly, and is positively correlated with the single well productivity. The genesis of coalbed methane and the gas content including free gas and adsorbed gas change with the variation of tectonic unit, burial depth and formation occurrence. The gas content in the area of 7 ~ 13 m3 / t is mainly composed of well-pre- served thermogenic gas-mixed gas, which is mainly distributed in the depression with the buried depth of 900 ~ 2 500 m. The areas with the gas content of less than 4 m3 / t are distributed on the slope and convex structure of the basin edge, mainly secondary biogas. The gas content between 4 ~ 7 m3 / t is dis- tributed in the transition zone between the above two. The gas content is high in the gentle slope with a dip angle of 3 ~ 7 degrees, and the gas content is low in the steep slope or large fault zone with a dip angle of 20 ~ 30 degrees. These complex structures play a decisive role in controlling the enrichment of coalbed methane and has important reference significance for exploration and development.