Effects of lacustrine organic-rich fine-grained sedimentary rocks on the accumulation of tight oil.

In order to establish the distribution pattern of fine-grained sedimentary rocks and clarify the coupling relationship between lacustrine organic-rich fine-grained sedimentary rocks and tight oil reservoir, the Chang7 Member of Triassic Yanchang Formation in Longdong area was taken as an example to be studied by core description and log interpretation, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Lacustrine organic-rich fine-grained sedimentary rocks were divided into shale and mudstone according to their lithology and texture. The results show that the shale is mainly developed in Chang73 Sub-member, while the mudstone is developed in each sub-member of Chang7 Member. The organic-rich fine-grained sedimentary rocks in Bazhu-Maling-Qingcheng-Huachi area are the thickest in Longdong area. During the Chang73 sedimentary period, the shale was widely distributed in the center of the lake. In the Chang72 sedimentary period, the mudstone and turbidite were interstratified and superimposed. During the Chang71 sedimentary period, the mudstone was only distributed as thin layers between the thick turbidite. The Chang7 tight oil is widely distributed in the turbidite sand bodies, and it is mainly sourced from the Chang73 shale. The distribution of tight oil is controlled by the development of organic-rich fine-grained sedimentary rocks. [ABSTRACT FROM AUTHOR]