吉木萨尔凹陷二叠系芦草沟组“甜点”成因与分布预测

通过岩石类型、矿物组分、物性特征、沉积环境及成岩作用等资料，对吉木萨尔凹陷二叠系芦草沟组页岩油“甜点”成因与空间分布进行了研究。研究结果表明：①研究区上“甜点”主要为砂质白云岩、泥质白云岩及白云质粉砂岩，下“甜点”主要为泥质白云岩、白云质粉砂岩、粉砂岩及白云质泥岩；上“甜点”平均孔隙度为9.4%，平均渗透率为0.0637mD，下“甜点”平均孔隙度为9.3%，平均渗透率为0.0231mD，均属于中低孔、特低渗储层。②研究区“甜点”储层主要孔隙类型为粒内溶孔和粒间溶孔，上、下“甜点”的差异受沉积环境变化和成岩作用影响，近岸滩和远岸滩物性较好，其次为远岸坝和云坪，压实作用和胶结作用是降低储集能力的两大因素，溶蚀作用可一定程度上改善其物性。③研究区上“甜点”具有“高自然伽马-高电阻率”特征，测井曲线呈尖峰状；下“甜点”具有“中自然伽马-高电阻率”特征；核磁孔隙度大于5.5%可作为识别“甜点”的敏感参数，地震反演剖面上“甜点”具有中高阻抗特征。④下“甜点”段相较于上“甜点”段在凹陷内分布更广，储层物性更优。

Genesis and distribution prediction of sweet spots of Permian Lucaogou Formation in Jimsar Sag

Based on the data of rock types，mineral components，physical properties，sedimentary environment and diagenesis，the genesis and distribution of shale oil sweet spots of Permian Lucaogou Formation in Jimsar Sag were studied. The results show that： （1）The upper sweet spots in the study area are mainly composed of sandy dolomite，argillaceous dolomite and dolomitic siltstone，and the lower sweet spots are mainly composed of argillaceous dolomite，dolomitic siltstone，siltstone and dolomitic mudstone. The upper sweet spots have an average poro-sity of 9.4% and an average permeability of 0.063 7 mD， while the lower sweet spots have an average porosity of 9.3% and an average permeability of 0.023 1 mD，all of them belong to medium-low porosity and ultra-low permeability reservoirs. （2）The pores in the sweet spot reservoirs are mainly intragranular dissolved pores and intergranular dissolved pores. The difference between the upper and lower sweet spots is influenced by depositional environment and diagenesis. The physical properties of inshore shoals and far-shore shoals are better，followed by far-shore dam and dolomitic flat. Compaction and cementation are the two major factors to reduce the reservoir capacity，and dissolution can improve their physical properties.（3）The upper sweet spots have the characteristics of high natural gamma and high resistivity，with peak-shaped logging curve，while the lower sweet spots have the characteristics of medium natural gamma and high resistivity. NMR porosity greater than 5.5% can be used as a sensitive parameter to identify sweet spots. The sweet spots on the seismic inversion section have the characteristics of medium and high impedance.（4）Compared with the upper sweet spots，the lower sweet spots are more widely distributed in the sag and has better reservoir physical properties.