准噶尔盆地石树沟凹陷平地泉组细粒岩特征及其对准东北地区页岩油勘探的指示意义

Characteristics of fine-grained rocks in the Pingdiquan Formation in Well Shishu 1 and their significances for shale oil explorations in northeastern Junggar Basin

中二叠统是准噶尔盆地重要的烃源岩层位及页岩油勘探层位。岩石地层单元芦草沟组与平地泉组以沙奇凸起相隔。尽管芦草沟组页岩油相关的研究已经取得较多成果,但对沙奇凸起以北广阔的克拉美丽山前地带平地泉组的研究还相对薄弱。以石树沟凹陷平地泉组全井段取心的石树1井为例,通过详细的岩石学、沉积相以及烃源岩参数分析,探讨了克拉美丽山前平地泉组的细粒岩特征、垂向分布及页岩油勘探前景。结果表明:(1)平地泉组为一个完整的三级层序,对应于南缘芦草沟组与红雁池组;有利烃源岩发育在湖平面上升半旋回的上部,即平地泉组下段的中上部,与芦草沟组中上部对应。(2)平地泉组烃源岩以高含量方沸石为特征,与芦草沟组在岩石结构组成上存在一定差异;有机质以内生藻类为主,类型以Ⅰ型和Ⅱ1型为主,与芦草沟组基本一致。(3)平地泉组细粒岩以块状为主,页理相对于芦草沟组欠发育。研究层段下部烃类滞留明显,具备"自生自储"型页岩油勘探潜力。

The Middle Permian is important for hydrocarbon source rock evaluations and shale oil explorations in northeastern Junggar Basin.The Lucaogou Formation and Pingdiquan Formation contain high-quality source rocks in eastern Junggar Basin,which have been tectonically separated by the Sha-qi Uplift.Although there have too many studies on shale oil in the Lucaogou Formation,few studies have been carried out on the Pingdiquan Foramtion in the vast area along the Kelameili Mountains.Well Shishu 1 has full core successions in the Pingdiquan Formation.Based on lithological analyses,and studies on data of source rocks,e.g.TOC,S1 and S2,this study focuses on the following items:source rock evaluations,vertically distributions and prospects of shale oil exploration.The following conclusions have been obtained:(1)The Pingdiquan Formation can be considered as a third-order sequence,which corresponds to combination of the Lucaogou Formation and the Hongyanchi Formation in southern Junggar Basin,and high-quality source rocks are developed in the middle and upper parts of Lower Pingdiquan Formation,which corresponds to the middle and upper Lucaogou Formation.(2)The source rocks in the Pingdiquan Formation have high content of mineral analcime,which is different from that of Lucaogou Formation;the organic matters in the Pingdiquan Formation are mainly algae and the kerogens are dominated byⅠandⅡ1 types,which are the same to those in the Lucaogou Formation.(3)Source rocks in the Pingdiquan Formation are blocky,and laminations do not develop;hydrocarbon was not easy to be expelled,and fine-grained rocks can be considered as"self-generation and self-accumulation"in the lower Pingdiquan Formation along Kelameili Mountains.