吉木萨尔凹陷芦草沟组储层特征及主控因素

Reservoir characteristics and main controlling factors of Lucaogou Formation in Jimsar Sag,Jungger Basin

为研究吉木萨尔凹陷芦草沟组页岩油储层特征及主控因素,开展岩心观察、铸体薄片鉴定、扫描电镜分析及全岩分析等工作,研究其岩石学特征、物性特征和成岩作用等。结果表明:芦草沟组岩石类型主要为碎屑岩、碳酸盐岩和混合细粒岩等,成分成熟度和结构成熟度均较低,分选性中等,原生粒间孔和次生溶孔是主要储集空间,砂岩孔隙度平均为7.34%,渗透率平均为0.079 mD,属低渗致密储层;储层发育主要受沉积和成岩双重作用控制,其中沉积作用控制着储层岩石类型的发育和分布,成岩作用过程中压实作用和胶结作用是导致储层孔隙度下降的主要原因,溶蚀作用对储层物性条件起到一定的改善作用。芦草沟组储层共经历了3次致密化阶段,压实作用是早期致密的主要原因,持续压实作用和硅质胶结作用在中期致密化阶段起到主导作用,晚期压实作用和碳酸盐岩、黏土矿物胶结共同作用于储层,使储层进一步致密化。该成果可为开发吉木萨尔凹陷芦草沟组页岩油提供一定理论依据。

In order to study the characteristics and main controlling factors of shale oil reservoir of Lucaogou Formation in Jimsar Sag,core observation,cast thin section identification,scanning electron microscope analysis and whole rock analysis were carried out,and petrological characteristics,physical properties and diagenesis were studied.The results show that the rock types of Lucaogou Formation are mainly clastic rocks,carbonate rocks and mixed fine-grained rocks,with low compositional maturity and structural maturity,medium sorting.Primary intergranular pores and secondary dissolved pores are the main reservoir space.The average porosity of sandstone is 7.34%,and the average permeability is 0.079 mD.It belongs to low permeability tight reservoir.Reservoir development is mainly controlled by sedimentation and diagenesis.Sedimentation controls the development and distribution of reservoir rock types.Compaction and cementation are the main reasons for the decrease of reservoir porosity in the process of diagenesis,and dissolution plays a certain role in improving reservoir physical properties.The reservoirs of Lucaogou Formation have experienced three densification stages.Compaction is the main reason for early densification.Continuous compaction and siliceous cementation play a leading role in middle-term densification.Late compaction,carbonate and clay mineral cementation jointly act on the reservoir to further densify the reservoir.The research results can provide a theoretical basis for the study of of shale oil development in Lucaogou Formation of Jimsar Sag.