Abstract: Well Xiongtan 1 in Kalayuergun structural belt of western Tabei uplift, Tarim Basin, has made a major breakthrough in oil and gas exploration in the Upper Cambrian Xiaqiulitage Formation in September 2023. This is another significant oil bearing strata discovery that has been made since Cretaceous and Paleogene in Tabei area, demonstrating the three-dimensional multi-layer hydrocarbon accumulation in Tabei area. Based on comprehensively analyzing the structural styles, fault characteristics, as well as the drilling, logging and testing data of Well Xiongtan 1, the paper makes clear the source rock conditions, oil and gas channel, reservoir-cap conditions and trap types of Kalayuergun structural belt, and systematically summarizes the accumulation elements and modes of the Cambrian Xiaqiulitage Formation in Kalayuergun structural belt. Two sets of deep source rocks are developed in Tabei uplift. The hydrocarbon source correlation shows that the Cambrian Yuertusi Formation is the main source rock layer, and the potential source rock is developed in the pre-Cambrian rift trough. Tectonic movement is active in the study area, forming Caledonian, Hercynian and Himalayan faults. NNW-trending strike-slip faults are superimposed with NW- and EW-trending thrust faults, forming an interlaced fault system, which vertically communicates with deep source rocks and reservoirs. Traps of the Upper Cambrian Xiaqiulitage Formation were formed at an early stage, where multiple periods of oil and gas accumulation occurred; under the influence of strong compression in Late Hercynian period, several faults connected with source rocks and related structural traps were initially formed. As a result of the late tectonic movement, the whole area continued to uplift, and formed a large area of continuously distributed tectonic traps in the Upper Cambrian reservoir, capturing oil and gas in multiple stages. The hydrocarbon accumulation mode of "lower generation and upper reservoir, dredging by faults and near-source accumulation" is established. The research results reveal that the Cambrian Xiaqiulitage Formation in western Tabei uplift has a huge exploration prospect, and it is expected to become a new strategic replacement area for increasing reserve and production in the platform area of Tarim Basin.

Key words: structural trap, reservoir-cap association, source rock of rift trough, accumulation stages, Xiaqiulitage Formation, Kalayuergun structural belt, western Tabei uplift

摘要： 2023年9月, 塔里木盆地塔北隆起西部喀拉玉尔衮构造带雄探1井在上寒武统下丘里塔格组获重大油气勘探突破,继白垩系、古近系后,塔北地区又获一重要层系发现,标志着塔北地区具备多层系立体成藏特征。基于构造样式、断裂特征及雄探1井钻井、测井、测试资料的综合分析,明确了喀拉玉尔衮构造带烃源岩条件、油源通道和储、盖条件及圈闭类型,系统梳理了喀拉玉尔衮构造带寒武系下丘里塔格组的油气成藏要素及成藏模式。塔北隆起深层发育两套烃源岩,其中,寒武系玉尔吐斯组为主要烃源岩层,前寒武系裂陷槽烃源岩为潜在烃源岩。研究区构造运动活跃,发育加里东期、海西期和喜马拉雅期断裂,NNW向走滑断裂叠加NW向及EW向逆冲断裂,形成相互交错的断裂体系,垂向沟通深部烃源岩与储集层。研究区上寒武统下丘里塔格组具有早期成圈、多期成藏的特点,晚海西期受强烈挤压作用的影响,多条通源断裂及相关构造圈闭雏形形成,后期构造运动叠加,研究区持续隆升,形成上寒武统大面积连片分布的构造圈闭,捕获多期油气充注。建立了下丘里塔格组“下生上储、断裂输导、近源成藏”的构造油气成藏模式。研究认识揭示,塔北西部寒武系下丘里塔格组具有巨大的油气勘探潜力,有望成为盆地台盆区新的油气增储上产战略接替区。

关键词: 构造圈闭, 储-盖组合, 裂陷槽烃源岩, 成藏期次, 下丘里塔格组, 喀拉玉尔衮构造带, 塔北西部