准噶尔盆地吉木萨尔凹陷二叠系芦草沟组微—纳米孔隙页岩油原位赋存特征

页岩油储层因微—纳米孔喉体系发育，使得油的赋存分散复杂，状态多样，研究困难。通过场发射扫描电镜、核磁共振、激光共聚焦和纳米CT等技术手段，对准噶尔盆地吉木萨尔凹陷中二叠统芦草沟组页岩油进行了研究。芦草沟组页岩油“甜点”粉—细砂岩和云质粉砂岩孔隙面孔率分布在11.0%~23.5%之间，大于2 μm的粒间溶孔、粒内溶孔占比在49.0%以上。受烃源岩生烃超压运移、孔隙表面吸附和页岩油连续成藏不同阶段油质差异等复杂因素控制，油和孔隙水的分布在微—纳米尺度上具有较强的分异性：“甜点”储层中2~5 μm以上孔隙内中质组分油和游离水赋存于孔隙中心，重质组分油以薄膜状赋存于孔隙表面；2 μm以下孔隙中主要为充填状重质组分油。中质组分油动用性较好，而重质组分油则是未来提高采收率比较现实可行的目标。

In situ occurrence of shale oil in micro-nano pores in Permian Lucaogou Formation in Jimsar Sag,Junggar Basin

The development of micro-nano pores and throats in shale oil reservoirs has made it complicated and diversified for the occurrence and state of oil, and is difficult to be studied. A case study was carried out with the Middle Permian Lucaogou Formation in the Jimsar Sag of Junggar Basin by the approaches of Field Emission Scanning Electron Microscopy (FESEM), Nuclear Magnetic Resonance (NMR), Laser Scanning Confocal Microscope (LSCM) and nano-CT. The plane porosities of siltstones and dolomitic siltstones in sweet spots of the study area range from 11.0% to 23.5%, and the dissolved pores and intragranular dissolved pores larger than 2 μm account for more than 49.0%. The distribution of oil and pore water has strong differentiation in micro-nano scale, which is controlled by complex factors such as overpressure migration of hydrocarbon generation, pore surface adsorption and oil quality difference in different stages of continuous shale oil accumulation. In sweet spot reservoirs, intermediate oil and free water occur in the center of pores larger than 2 μm, while heavy oil exists on pore surface as thin film. Pores with the size smaller than 2 μm are mainly filled with heavy oil. Intermediate oil is relatively easier to be explored, while heavy oil is a more realistic and feasible target for enhanced oil recovery in the future.