查干凹陷下白垩统烃源岩特征评价

The Lower Cretaceous Source Rock Evaluation in the Chagan Sag,Inner Mongolia

查干凹陷下白垩统发育有苏一段、巴二段和巴一段3套烃源岩。该地区下白垩统三套烃源岩中巴二段是最重要的生油层系,主要成因是深湖-半深湖和滨浅湖环境,以深灰色、灰黑色泥岩为主,有机质成熟度基本达到成熟阶段,局部地区已达到过成熟。同时该段有机质丰度较好,有机质类型主要以Ⅱ型为主。而苏一段和巴一段烃源岩总体评价为中-差烃源岩,为该地区次要烃源岩。下白垩统烃源岩具良好的生烃潜力,油气勘探前景良好。

Three sets of source rocks of the lower Cretaceous are distributed in the Chagan sag of the Yingen-Ejinaqi basin. Based on the analytic technique of the Rock-Eval, GC-MS, GC-MS-MAT, and knowing from the precipitation facies and seismic facies, the results indicate that the Second Member of Bayingebi Formation is the principal source rock, and the possible source rocks in this formation are dark black mudstone and dark grey mudstone deposited in an environment of semi-deep lake or deep lake or lake beach, shallow lake which has a high organic matter abundance, and the organic materials take type II kerogen as the dominant factor. The thermal evolutions of the most organic matter have reached the maturity stage. The quantitative evaluation of hydrocarbon-generating potential of the First Member of Bayingebi Formation and First Member of Suhongtu Formation in the basin is not very high, we can make it as the secondary source rock. Therefore, a better potential ofoil and gas prospect in the Lower Cretaceous of the Chagan Sag area is proposed.