鄂尔多斯盆地姬塬地区长8油层组物源分析

位于鄂尔多斯盆地的姬塬地区上三叠统延长组长8油层组,具有四周均发育三角洲沉积和多物源供给的岩相古地理特征。应用储集砂岩薄片鉴定和骨架碎屑组分、重矿物类型及其组合类型的分析结果,结合沉积构造、古生物及砂岩分布三次趋势面分析等技术方法,对姬塬地区长8油层组物源特征进行了综合分析,并认为：①长8油层组沉积期该区物源来自东北、西北及西南3个方向,以西北和东北为主物源方向,不同物源方向的砂体于研究区中部的半深湖区发生汇集;②不同方向物源区的母岩性质有差别,西北方向的物源区母岩为火山岩、浅—中级变质岩组合,东北方向主要为火山岩-低级变质岩组合,西南方向主要为变质岩-沉积岩组合;③长8油层组砂体和岩性油藏的展布都具有同物源方向延伸的特点。上述研究成果为姬塬地区长8油层组砂体和岩性油藏预测提供了地质依据。

Provenance analysis of the 8th oil-bearing member of Yanchang Formation,Upper Triassic, Jiyuan area, Ordos Basin

During the deposition of the 8th oil-bearing member of Yanchang Formation, Upper Triassic, deltaic depositional systems were developed and muti-provenances were provided around Jiyuan area, which was located in the middle-western part of Ordos Basin. Based on the analysis of thin sections,detrital framework grains and heavy minerals and their associations, and with the combination of sedimentary structures, paleontology and the tripartite trend surface analysis of sandbody distributions, the provenance of the 8th member in Yanchang Formation was studied, and the following results were concluded: ①The sources during the deposition of the 8th oil-bearing member of Yanchang Formation were from northeast, northwest and south. ②There were certain differences in the nature of source rocks. The northwest source area was dominated by volcanic rocks and light to middle metamorphic rocks association, the northeast by volcanic rocks-lower metamorphic rocks association, and the southwest by metamorphic rocks-sedimentary rocks association. ③The distribution directions of sand bodies were same to that of the lithologic reservoirs. The above results would provide important geological basis for the prediction of sand bodies and lithologie reservoirs in the 8th oil-bearing member of Yanchang Formation.