Study On The Lithofacies Types And Reservoir Space Differences Of The Shale In The Second Member Of Kongdian Formation In The Cangdong Sag

The exploration and development of unconventional oil and gas resources has received increasing attention in the world in recent years.As an important part of unconventional oil and gas resources,shale oil affects the distribution pattern of global energy and the exploration direction of world oil and gas resources.Our country is rich in shale oil resources and has good development prospects.The second member of Kongdian formation in the Cangdong Sag in the study area has the conditions for the formation of shale oil resources and the potential for exploration and development.However,due to the rapid change of stratigraphic lithology,strong heterogeneity and lack of accurate description of the reservoirs,which affects the exploration and development deployment of shale oil.Therefore,research on the reservoir development characteristics of the lacustrine shale in the second member of Kongdian Formation in the Cangdong Sag is of great significance for the exploration and development of shale oil resources.In this thesis,through core observation,thin section identification,field emission scanning electron microscopy,high-pressure mercury intrusion,nuclear magnetic resonance,and lowtemperature nitrogen adsorption experiments,the lithofacies and pore types of the lacustrine shale system of the second member of the Cangdong Sag are finely classified,and Qualitativequantitative characterization of the differences in the reservoir space of different lithofacies,and preferential types of lithofacies.(1)The results show that the shale in the second member of Kongdian formation in the Cangdong Sag is mainly composed of felsic minerals,carbonate minerals,clay minerals and a small amount of pyrite and siderite.There are no obvious dominant minerals on the whole,and the clay content is low.According to the abundance of organic matter,mineral composition and sedimentary structure,the shale of the second member of Kongdian formation in the Cangdong Sag is mainly divided into low organic matter massive lime-dolomitic shale facies,mediumhigh organic matter laminated felsic lime-dolomitic shale facies,low-medium organic matter layered mixed lime-dolomitic shale facies,medium-high organic matter laminated limedolomitic felsic shale facies,medium-high organic matter massive mixed felsic shale facies,medium-high organic matter laminated clay-bearing felsic shale facies,low-medium organic matter massive mixed shale facies and medium-high organic matter laminated mixed shale facies.(2)The study area mainly develops 4 types of pores and 4 types of fractures.The pore types include intergranular pores,intercrystal pores,dissolved pores and organic pores;fractures include structural fractures,interlayer fractures,abnormal high pressure fractures and diagenetic contraction fractures.Among them,intergranular pores,intercrystal pores and dissolved pores with high degree of dissolution are the best developed,providing the main microscopic storage space.(3)On the basis of qualitative analysis,NMR technology,high pressure mercury intrusion and low temperature nitrogen adsorption analysis technology were combined to explore the differences of reservoir space in different lithofacies.The laminated lithofacies pores and fractures are relatively developed and have good reservoir space.In the lithofacies with high clay content,clay minerals fill the intergranular pores and destroy the pores.Laminar development plays an important role in shale reservoir-migration system.Medium-high organic matter laminated felsic lime-dolomitic shale facies(C1)and mediumhigh organic matter laminated lime-dolomitic felsic shale facies(S1)are selected as the dominant facies.