塔里木盆地寒武系烃源岩分布的重新认识及其意义

Recognition of the distribution of Cambrian source rocks and its significance for exploration in Tarim Basin

塔里木盆地台盆区海相烃源岩的分布是制约油气勘探的主控因素,在构造—古地理背景分析基础上,通过典型井地球化学分析结合测井标定与地震追踪,重新厘定寒武系主力烃源岩分布。结果表明,东部烃源岩主要分布在中-下寒武统泥页岩中,西部烃源岩主要分布在下寒武统泥页岩中,中-上寒武统—下奥陶统碳酸盐岩缺乏有效烃源岩,单井纵向厚度标定东部低于100 m、西部低于40 m,远低于早期预测厚度。寒武系烃源岩并非满盆分布,主要分布在满东凹陷、满西台内洼,并发现塔西南南缘可能发育大面积陆缘斜坡烃源岩,而巴楚—麦盖提、塘古—塔中、塔北等基底古隆起区缺乏烃源岩。受控前寒武纪古隆起与寒武纪弱伸展背景影响,寒武系发育4种构造背景下的烃源岩:主要为台间盆、台内洼烃源岩,以及可能存在被动陆缘斜坡、板块边缘裂谷烃源岩。

Due to the importance of the marine source rocks to the exploration in the Tarim Basin,this paper present a new distribution of the Cambrian source rocks distribution based on the study of tectonic-paleogeography,geochemitry of typical wells and new seismic data.It is shown that the source rocks are mainly mudstones and shales from the Middle-Lower Cambrian in the eastern Tarim and from the Lower Cambrian in the western Tarim.However,the source rocks are sparse in the Lower Paleozoic carbonate rocks.With logging calibration,the source rocks thickness is less than 100 m and 40 m in the eastern and western Tarim,respectively.By the seismic data interpretation,the Cambrian source rock distribution is not full of the basin,but mainly distributed in three areas of the Mandong and Manxi Depressions,and southwestern margin of the Tarim,while sparse source rocks in basement uplifts.Controlled by Precambrian palaeo-uplift and weak extension in the Cambrian Tarim,the source rocks are mainly developed in four tectonic setting:inter-platform basin and inner-platform depression,and the possibly passive margin slope and plate margin rift.