Wang Boyang, Liu Bo, Sun Guoxiang, Bai Longhui, Chi Yaao, Liu Qi, Liu Miao
Key Laboratory of Continental Shale Hydrocarbon Accumulation and Efficient Development, Ministry of Education, Northeast Petroleum University, Daqing 163318, China.
PetroChina Jilin Oilfield Company, Songyuan 138000, China.
ACS Omega. 2021 Apr 28;6(18):12081-12098. doi: 10.1021/acsomega.1c00756. eCollection 2021 May 11.
The Lucaogou Formation (Fm) in the Jimusaer depression is the first large-scale development of a terrigenous clastic sedimentary shale oil reservoir in China. Nearly one billion tons of shale oil resources have been discovered. However, the current exploration and development is concentrated in the eastern part of the sag. The limited geological understanding in the western area has restricted the prediction and development of "sweet spots" for shale oil. To help rectify this, we have studied the petrology, geochemistry, oil content, and pore properties of the second part of the first member (Mbr) of the Lucaogou Fm (Pl ) in a typical well (Ji-X) in the western part of the sag. The results show that Pl in the Jimusaer sag is a mixed fine-grained sedimentary system composed of sandstone, mudstone, and carbonate, which can be divided into seven types: dolomitic mudstone, calcareous mudstone, mudstone, mixed fine-grained rock, argillaceous limestone, sandstone, and argillaceous dolomite. The organic matter type of Pl in well Ji-X is dominated by types I and II, and this is the best source rock in the whole exploration area of the Jimusaer sag. The overall oil saturation is relatively high, but the maturity of crude oil is low, and the overall oil quality is heavy, which is mainly controlled by the sedimentary environment and maturity of source rocks. Lithology and reservoir physical properties are the key to control oil content. The high-quality light oil reservoir lithology is argillaceous dolomite and sandstone. The higher the content of macropores and mesopores, the weaker the heterogeneity of the pore structure, and the better the oil content in the reservoir. There are four light oil sweet spots in the upper part (burial depth less than 4366 m), and there are excellent source rocks with high HI and high organic matter content near each sweet spot. This discovery of shale oil enrichment regularity will effectively guide the development of shale oil in continental lacustrine basins in other parts of the world.
吉木萨尔凹陷芦草沟组是中国首个大规模发育的陆相碎屑沉积页岩油储层。已发现近10亿吨页岩油资源。然而，目前的勘探开发集中在凹陷东部。西部地区地质认识有限，制约了页岩油“甜点”的预测与开发。为解决这一问题，我们研究了凹陷西部典型井（吉X井）芦草沟组一段二亚段（芦一段二亚段）的岩石学、地球化学、含油率及孔隙特征。结果表明，吉木萨尔凹陷芦一段二亚段为砂岩、泥岩和碳酸盐岩组成的混合细粒沉积体系，可分为白云质泥岩、灰质泥岩、泥岩、混合细粒岩、泥质灰岩、砂岩和泥质白云岩七种类型。吉X井芦一段二亚段有机质类型以Ⅰ型和Ⅱ型为主，是吉木萨尔凹陷整个勘探区最好的烃源岩。整体含油饱和度较高，但原油成熟度较低，整体原油质量偏重，主要受烃源岩沉积环境和成熟度控制。岩性和储层物性是控制含油率的关键。优质轻质油储层岩性为泥质白云岩和砂岩。大孔和中孔含量越高，孔隙结构非均质性越弱，储层含油率越好。上部（埋深小于4366米）有4个轻质油甜点，每个甜点附近均有高氢指数和高有机质含量的优质烃源岩。这一页岩油富集规律的发现将有效指导世界其他地区陆相湖盆页岩油的开发。
