银根—额济纳旗盆地天草凹陷构造-沉积体系演化及油气成藏条件分析

天草凹陷位于银根—额济纳旗盆地白垩纪断陷盆地群的西北部,经历了早白垩世断陷发生、发展阶段,晚白垩世坳陷阶段,第三纪到第四纪挤压抬升等主要的构造演化发展阶段。其中,第一阶段是形成盆地沉积建造的主要时期,沉积了2000～3000m的早白垩世沉积,其间经历了两次大的湖侵、湖退过程,对应沉积了两套浅湖-半深湖相烃源岩和扇三角洲相砂体。天草凹陷油源、储层、保存、圈闭配套匹配以及油气运聚等油气成藏条件好,用类比法和盆地模拟法计算的凹陷总资源量的期望值为0.89亿吨。下白垩统巴音戈壁组上部是主要的含油层系,位于凹陷东西两侧的巴勒断阶带、哈尔构造带是天草凹陷油气勘探的重要领域。

STRUCTURAL-DEPOSITIONAL SYSTEM AND FACTORS AFFECTING THE HYDROCARBON POOL FORMATION IN TIANCAO DEPRESSION, THE YINGEN- EJINAQI BASIN

Located in the northwest of the Cretaceous rift basin group in Yingen Ejinaqi basin, the tectono-sedimentary evolution of Tiancao depression involves three main periods, the first period is the occurrence and development of the rift in earlier Cretaceous, the second period is the sagging during later Cretaceous and the third period is squeezing and uplifting during Tertiary and Quaternary. The sedimentary formation of Tiancao depression, consisting of 2,000 to 3,000 meters Lower Cretaceous sedimentary rocks, was formed mainly during the first period. During the first period, two large-scale lake transgression and regression events occurred, which resulted in the formation of two sets of shallow, shallow-semi-deep lacustrine facies source rocks and fan delta sand bodies. Factors favorable for the pool formation in Tiancao depression include source rock, hydrocarbon reservoir, preservation, trap, oil and gas accumulation conditions, etc. The estimated total resource in Tiancao depression is 89 million tons based on basin simulation and analog study. The upper part of the Bayingebi formation is the main petroleum-bearing stratum. Bale fault and Haer structural zone, which are located at the east and west respectively, are the key areas for hydrocarbon exploration in Tiancao depression.