鄂尔多斯盆地中西部长7段烃源岩及致密油潜力评价

Evaluation of Source Rocks and Tight Oil Exploration Potential of Chang-7 Member in Central and Western Ordos Basin

由于对鄂尔多斯盆地中西部地区延长组长7段烃源岩缺乏深入研究,制约了该区油气勘探的进程。为了阐明其烃源岩生烃条件,在大量资料和前人研究成果的基础上,对该区长7段烃源岩的分布和地球化学特征进行了系统分析,预测了油气有利勘探区,为研究区延长组致密油勘探提供依据。研究表明,长7段沉积期,研究区烃源岩沉积中心位于姬塬、耿湾、环县东部及白豹—纸坊地区,长7段暗色泥岩平均累计厚度大,烃源岩有机质类型好,丰度高,热演化程度较高,已进入生油阶段,属于典型的优质湖相烃源岩,是该区延长组油藏的主力烃源岩。在研究区圈定了6个有利勘探区,分别位于定边以南的油房庄西部地区、姬塬以东地区、铁边城以南地区、铁边城东北部地区、环县东北部地区以及白豹以南地区。

There is lack of profound study on the source rocks in Chang-7member of Yanchang formation in the central and western Ordosbasin,which restricts the oil and gas exploration process in the area.In order to clarify hydrocarbon generation conditions of the sourcerocks in Chang-7member,the paper makes a systematic analysis on distribution and geochemical characteristics of Chang-7source rocksin the area based on enormous amounts of actual data and previous research results,predicts favorable areas for oil and gas exploration andprovides basis for tight oil exploration in Yanchang formation in the study area.The results show that the depocenters of the source rocks inthe study area were mainly located in Jiyuan,Gengwan,Eastern Huan County,Baibo and Zhifang area during the deposition of Chang-7member.The dark shales with large average cumulative thickness in Chang-7member are characterized by good organic matter type,highorganic matter abundance and high thermal evolution degree(indicating a stage of hydrocarbon generation),which belong to typical high-quality lacustrine source rocks and are major source rocks of Yanchang formation in the area.6favorable exploration areas are determinedin the study area,including the western Youfangzhuang area to the south of Dingbian,the area to the east of Jiyuan,the area to the south ofTiebiancheng,northeastern Tiebiancheng area,northeastern Huan county and the area to the south of Baibo.