Characteristics And Classification Evaluation Of Shale Oil Reservoir Of The Lucaogou Formation In Jimsar Sag

As a national demonstration center for shale oil,the shale oil of the Permian Lucaogou Formation of Jimsar Sag in the Junggar Basin with good shale oil development potential.At present,it has become the focus and hotspot of exploration and development.shale oil reservoirs of Lucaogou Formation in Jimsar Sag are characterized by variable rock types,strong heterogeneity,and complex pore-throat structures,which bring great challenges to the classification,evaluation and efficient development of reservoirs.This paper takes the shale oil reservoir of Lucaogou Formation in Jimusar as the research object,uses core observation,thin section identification,scanning electron microscopy,X-ray diffraction of whole rock and clay minerals,overburden porosity,high pressure mercury injection and nuclear magnetic resonance and other technical means to clarify the basic characteristics of the reservoir and the difference characteristics of the dominant lithologic reservoirs,comprehensively analyze the main controlling factors and the genetic evolution mechanism of the reservoir,and combine the logging data and production data to establish the reservoir evaluation standard and make a classification evaluation.so as to provide a basis for shale oil reservoir evaluation and high-quality reservoir prediction.The main results of this study are:(1)The shale oil reservoirs of Lucaogou Formation in Jimusar sag developed a large set of shale intercalated with thin layers of silt-fine sandstone,dolomite and argillaceous siltstone.The rock types are very complex,and the dominant lithology of the shale oil sweet spot is mainly feldspar lithic fine-grained sandstone,dolomitic silt fine sandstone and argillaceous sandy dolomite.(2)The diagenesis types of the shale oil reservoirs in the study area are mainly compaction,dissolution,cementation and metasomatism.The authigenic minerals such as calcite and chlorite can be visible,and the storage space types are mainly primary pores and secondary dissolved pores,developing a small number of organic pores and fractures.The pore-throat structures of the reservoir are complex.(3)The shale oil reservoir in the study area has strong heterogeneity,and the reservoir performance and oil content of different lithologies are significantly different.The main performance is that the fine-grained sandstone of feldspar cuttings is the best,followed by the dolomitic silt sandstone.The argillaceous sandy dolomite is relatively poor.(4)Shale oil reservoirs in the study area are mainly controlled by structure,sedimentation and diagenesis.The volcanic tectonic movement provides the provenance for the study area,the sedimentary facies belt determines the material basis for the development of the reservoir,and the difference in the type and intensity of diagenesis leads to the differential evolution of the reservoir pores,resulting in obvious differences in the characteristics of the reservoir.(5)The reservoir lithology,physical properties,pore type and pore throat radius are selected as the reservoir classification evaluation parameters,and the shale oil reservoirs of the Lucaogou Formation in Jimsar Sag are divided into Type I,Type II,Type III,Type IV and ineffective reservoirs.Feldspar lithic fine-grained sandstone and dolomitic silt fine sandstone are mainly Type I reservoirs,and Type II or Type III reservoirs are also developed.Micrite dolomite is mainly Type IV reservoir or ineffective reservoir.