塔里木盆地中秋1凝析气藏成藏条件及演化过程

2018年12月,塔里木盆地秋里塔格构造带天然气勘探取得重大突破,中秋1井在下白垩统巴什基奇克组测试获高产工业气流,发现了该构造带迄今为止最大的整装凝析气藏。为了给该构造带下一步油气勘探部署提供依据,在充分利用前人研究成果的基础上,基于岩心、薄片、测井及地球化学分析资料,明确了中秋1大型凝析气藏的油气藏特征和气藏类型,分析了该气藏天然气成藏条件并推演其演化过程。研究结果表明:①中秋1大型气藏属于低含凝析油凝析气藏,天然气为煤成气,主要来自区内侏罗系腐殖型煤系烃源岩;②该构造带能够形成大型油气藏的有利地质条件是三叠系和侏罗系发育的两套巨厚高演化烃源岩、白垩系发育的大型辫状河三角洲规模有效砂岩储层、喜马拉雅晚期以来的构造活动形成的大规模楔状叠瓦构造圈闭、古近系和新近系巨厚膏盐岩形成的优越保存条件,以及油气生成与圈闭形成的良好时空匹配;③该气藏具有先油后气、晚期快速气侵聚集成藏的成藏模式,总体上是一个"早期聚油、晚期气侵、改造调整、快速成藏"的成藏过程。结论认为,该构造带油气成藏条件优越,具有广阔的油气勘探前景。

Hydrocarbon accumulation conditions and evolution process of the ZQ1 large condensate gas reservoir in the Qiulitage structural belt,Tarim Basin

In December 2018, a high-yield industrial gas flow was achieved in the test of Well ZQ1 from the Cretaceous Bashijiqike Fm, which was a major breakthrough in natural gas exploration in the Qiulitage structural belt of the Tarim Basin, where the largest condensate gas reservoir has been discovered so far. In order to provide evidences for further oil and gas exploration in this structural belt, this paper made full use of the previous research results, based on the core, thin section, logging and geochemical analysis data of this well, clarified the types and characteristics of this gas reservoir. Also, the gas accumulation conditions of this gas reservoir was analyzed, a gas accumulation model was established, and its evolution process was then deduced. The following results were presented. (1) The ZQ1 large gas reservoir belongs to a condensate gas reservoir with condensate oil, and with coal-derived gas mainly derived from the Jurassic humus-type coal-series source rocks in this area. (2) The geological conditions in this structural belt include the super-thick and high-revolutionary source rocks developed in the Triassic and Jurassic, large effective sandstone reservoirs developed in the Cretaceous large braided river delta, large wedge-shaped tectonic traps that formed due to tectonic activities since the late Himalayan period, and Paleogene and Neogene thick salt rocks provide superior preservation conditions for the gas reservoir formation and good time–space matching of hydrocarbon generation and trap formation. (3) The "first oil and then gas" accumulation process of this condensate reservoir is overally characterized by "oil accumulated at the earlier stage, gas invasion at the later stage, and rapid pooling". It is concluded that hydrocarbon accumulation conditions are superior in the Qiulitage structural belt and it has broad prospects of oil and gas exploration in Tarim Basin. In conclusion, this structural belt with favorable oil and gas conditions presents a good hydrocarbon exploration prospect.