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二叠系是叶城—和田凹陷最为重要的烃源岩层系之一。通过和田凹陷杜瓦地区野外露头剖面及最新钻井分析,并结合有机地球化学测试数据,对二叠系普司格组烃源岩沉积特征、古环境及有机地球化学特征进行研究。结果表明:普司格组烃源岩发育在滨湖、浅湖及半深湖亚相中,乌鲁吾斯塘地区和杜瓦地区为烃源岩沉降中心,以低Pr/Ph值、较高伽马蜡烷指数等为特征,表现出较强还原性、较高盐度下具有一定水体分层的湖相沉积产物。普司格组烃源岩有机碳(TOC)值为0.12%~5.68%,为“差—中等”烃源岩,有机质类型以Ⅱ型、Ⅲ型为主,镜质体反射率RO值为0.72%~1.385%,主体已进入成熟—高成熟阶段。结合地震资料、生储盖条件分析认为,杜瓦地区普司格组烃源岩生烃潜力较好,逆冲推覆体为油气勘探的可能有利区域,准原地质体为塔西南坳陷山前带最为有利的油气勘探区域,原地质体埋深很大,是目前勘探工作面临的主要挑战之一。
Permian is one of the most important source rocks in Yecheng-Hetian Depression. Based on the field outcrop profile and the latest drilling analysis in Dewar area of the Hetian Depression, and combined with the data from organic geochemical tests, the sedimentary characteristics, palaeo - environment and organic geochemical characteristics of the source rocks of Permian Psiju Formation are studied. The results show that the source rocks of the Psijuga group are developed in the lakeshore, shallow lake and semi-deep lake subfacies, and the Urumqi-Sitang area and the Dewar area are the sedimentary centers of the source rocks. With low Pr / Ph, High gamma-rayon index and so on, characterized by strong reducibility, lacustrine sediment with a certain water layer at higher salinity. The organic carbon (TOC) values of source rocks in the Pristis Formation range from 0.12% to 5.68%, and are “poor-moderate” source rocks. The organic matter types are mainly Type II and Type III, and the vitrinite reflectance, RO 0.72% ~ 1.385%, the main body has entered a mature - high maturity stage. Based on the analysis of seismic data, source and reservoir conditions, the hydrocarbon generation potentials of the source rocks in the Psitig Formation in Dewar are good, and the thrust nappe is a possible favorable area for oil and gas exploration. The quasi-original geologic body is the piedmont of the southwestern Tarim basin With the most favorable oil and gas exploration area, the original geological body has a large depth of burial, which is one of the major challenges facing the exploration.