准噶尔盆地吉木萨尔凹陷芦草沟组页岩油储层孔隙结构、烃类赋存及其与可动性关系

为研究页岩油可动性与储层孔隙和含油性的关系，采用场发射扫描电镜、激光共聚焦显微镜、纳米CT、高压压汞法与氮气吸附联合分析、核磁共振分析、分子模拟分析等实验技术，对准噶尔盆地吉木萨尔凹陷二叠系芦草沟组页岩油储层孔隙全尺度分布特征、烃类赋存特征进行了定量分析。该页岩油储层各类岩性孔隙分布存在较大差异性，优势岩性为砂屑云岩、长石岩屑粉细砂岩和云质粉砂岩，其中长石岩屑粉细砂岩最好，大于300 nm孔隙占比74.1%，主体以粒间（溶）孔、粒内溶孔为主。微纳米尺度流体赋存具有较大的分异性。重质组分在半径300 nm以上孔隙中呈薄膜状附着于矿物、孔隙表面，300 nm以下呈充填状；中质组分赋存于300 nm以上孔隙中央；水含量较少，赋存于300 nm以上孔隙中央，被中质组分包裹。芦草沟组页岩油孔喉动用下限为50 nm；300 nm以上孔喉中烃类易动用，是当前产能主要贡献体系，采出原油为300 nm以上“大孔”中的中质油；50~300 nm孔喉较难动用，是提高采收率的关键。负压和升温可有效提升纳米孔中烃类的可动性。

Pore structure,hydrocarbon occurrence and their relationship with shale oil production in Lucaogou Formation of Jimsar Sag,Junggar Basin

In order to study the relationship between shale oil production and reservoir porosity or the oil content, experimental approaches including FE-SEM, LSCM, nano CT, high pressure mercury injection and nitrogen adsorption combined analysis, NMR analysis and molecular simulation were used to quantitatively analyze the full-scale distribution and occurrence characteristics of shale oil in Permian Lucaogou Formation of the Jimsar Sag, Junggar Basin. There are significant differences in the pore-size distribution of various lithologies in shale oil reservoir of the Jimsar Sag. The dominant lithology are arenaceous dolomite, feldspar lithic siltstone and dolomitic siltstone, and the best one is feldspar lithic fine sand rock, with pores larger than 300 nm accounting for 74.1%, and the main body is intergranular (dissolved) pores and intergranular dissolved pores. Fluid occurs with large heterogeneous in micro-nano scale. Heavy components with fluorescence wavelength between 600 and 800 nm attached to mineral pore surface as thin film in pores with a radius above 300 nm, and filled in pores with a radius below 300 nm. The medium components with fluorescence wavelength between 490 and 600 nm occur in the center of pores above 300 nm. The water content is low, and occurs in the center of the pores above 300 nm wrapped by the medium component. The lower limit of pore throat production of shale oil in the Lucaogou Formation is 50 nm. Above 300 nm, the hydrocarbon in pore throat is easy to be produced and is the main contribution system of current productivity. The recovered crude oil with medium density is mainly from large pore above 300 nm. Pore-throats distributed between 50 to 300 nm are difficult for the shale oil producing, which is the key to enhance oil recovery. Negative pressure and temperature rise can effectively improve the mobility of hydrocarbons in nano-scale pores.