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对研究区内9口探井的石炭系、中-上奥陶统及中-下寒武统3套烃源岩的29个样品进行了有机成熟度测定;利用3条地震剖面读取40个人工井点的地层分层数据,结合已有的地层剥蚀厚度和地温梯度数据,对烃源岩作了详尽的生烃史分析。研究表明,塔西南坳陷北坡源岩在晚第三纪经历了快速埋藏,有机质成熟度快速增加,并伴随有强烈的生烃(气)作用发生;与此相比,巴楚凸起上的烃源岩演化定型期早,在距今250×106a以后没有生烃作用发生。和田河(该区最大的气田)天然气乙烷碳同位素(δ13C2)分布在-37.8‰～-34.9‰,表明生烃母质为Ⅱ型偏腐泥型有机质,根据δ13C1—Ro换算公式,算得Ro在1.67%～2.34%,与烃源岩有机质类型及成熟度(实测值和模拟值)比较,可知其源岩为中-下寒武统源岩。研究认为大部分和田河气田的天然气主要是由塔西南坳陷北坡被第三系地层快速埋藏的中-下寒武统源岩干酪根热裂解生成的,并经过较长距离运移至塔西南坳陷北坡与巴楚凸起的结合部位成藏。
The organic maturity of 29 samples from 9 exploration wells in Carboniferous, Middle-Upper Ordovician and Middle-Lower Cambrian in the study area was measured. Using three seismic sections, 40 artificial Based on the stratigraphic stratification data of well points, combining with the existing denudation thickness and geothermal gradient data, a detailed hydrocarbon generation history analysis of source rocks has been made. The results show that the source rocks on the northern slope of the southwestern Tarim Basin experienced rapid burial in the late Tertiary and the maturity of organic matter increased rapidly with the strong hydrocarbon generation (gas). In contrast, Of the source rock evolutionary setting early, no generation of hydrocarbons occurred after 250 × 106a. The δ13C2 of natural gas from the Hetianhe (the largest gas field in the area) is between -37.8 ‰ and -34.9 ‰, indicating that the hydrocarbon-generating parent material is type Ⅱ partial sapropelic organic matter. According to the δ13C1-Ro conversion formula, Ro 1.67% ~ 2.34%. Compared with the organic matter type and maturity (measured value and simulated value) of source rock, it can be seen that the source rock is a mid-lower Cambrian source rock. The study shows that most of the natural gas in the Hetianhe gas field is mainly formed by the thermal cracking of the middle-lower Cambrian kerogen kerogen rapidly buried in the Tertiary Formation in the northern slope of the Tarim Basin and transported to the southwest of the TACA Sinking north slope and Bachu convex part of the accumulation of reservoir.