Research On The Potential Of Lacustrine Shale Oil And Gas Resources In The Da'anzhai Section Of The Jurassic In The Central Sichuan Basin

This paper guided by multidisciplinary theories such as petroleum geology,oil and gas geochemistry,geophysical well logging and hydrocarbon accumulation theory,uses a combination of indoor and outdoor,ground and downhole,macroscopic and microscopic research to J1dn13,As the main research interval,the dark shale of the J1dn13 is the main research object,and the small layer is finely divided,which improves the accuracy of the research and lays a foundation for the subsequent research.According to the sedimentary characteristics in the study area,the Da'anzhai(J1dn)Formation of the study area will be It is divided into three sedimentary sub-facies;a variety of experimental instruments are used to study the characteristics of shale reservoirs;combined with the analysis of experimental data foundation,the geochemical characteristics and distribution of dark shale in the Da'anzhai(J1dn)Formation are defined;On the basis of the preferred resource estimation method,the shale oil and gas resources in the Da' anzhai(J1dn)Formation of the study area are estimated.Research shows:(1)The Da'anzhai Formation in the central part of Sichuan Basin can be divided into three sub-sections(J1dn1,J1dn13,J1dn3)from the bottom to top.The J1dn sub-section of the key research section can be subdivided into three small layers:J1dn13a,J1dn13b and J1dn13c.a small layer thickness of 5m?20m,the thickness of the south and northwest of the plane is the largest,the overall appearance of the characteristics from the southeast to the north gradually thinning,b small layer thickness 15m?25m,the plane high value area is located in the southern An Yue-TongNan-HeChuan area,and the trend of gradually thinning from south to north,the thickness of small layer c is 10m?30m,the thickness is the largest in the south and north central part of the study area,the thickness is thin in the west and northeast,and the whole surface is presented.It gradually decreases from the north to the south and gradually decreases from east to west.The boundaries between the three small layers are clear and easy to distinguish.(2)The central part of the Sichuan Basin is the main lacustrine facies,and the J1dn13 sub-sectiont is the main research layer.It mainly develops three sub-facies of the semi-deep lake sub-facies,the shallow lake sub-facies and the lakeside sub-facies.The J1dn13a small layer mainly develops the semi-deep lake sub-facies,the J1dn13b small layer semi-deep lake sub-facies,the shallow lake sub-facies and the lakeside sub-facies all develop,the J1dn13c small layer does not develop the semi-deep lake sub-facies,only the shallow lake sub-facies And the lakeside sub-facies.(3)The shale reservoirs in the Da'anzhai(J1dn)Formation are mainly composed of brittle minerals,which are similar to the Da'anzhai(J1dn)Formation of the northern Yuanba area,the Da'anzhai(Jidn)Formation of the eastern Fuling area,and the Longmaxi Formation of the marine strata.The composition is similar;shale storage The space o rganic pores and inorganic pores coexist,and the pore-permeability is poor.It is a typical tight reservoir.From the shale pore size distribution,the NMR test analysis shows that the mesopores are dominant,and the nitrogen adsorption test shows that the pore size distribution is mainly The range of 50 nm to 100 nm,but the results of both tests show that the pore size distribution is similar to the shale of the Da'anzhai(J1dn)Formation of the Fuling area in the eastern Sichuan Basin,and is superior to the Longmaxi Formation shale in the marine strata.(4)The average thickness of the shale in the J1dn13 sub-section in the central part of the Sichuan Basin is 35 meters,the average thickness of the small layer of J1dn13a is 15 meters,the average thickness of the small layer b is 10 meters,and the average thickness of the small layer of c is 10 meters.From the perspective of organic geochemical conditions,The sedimentary facies analysis shows that the semi-deep lake sub-phase source conditions are optimal,the shallow lake subfacies is second,and the lakeside subfacies are poor.From the vertical horizon analysis,the J1dn13a small layer and J1dn13b small layer hydrocarbon source conditions are optimal.The J1dn13c small layer is poor;the source rocks in the study area are mainly type ?organic.The J1dn13a small layer and the J1dn13b small layer are all high-quality source rocks,and the J1dn13c small layer is medium source rock;the study area is in the northeastern Longgang area,and the Qiulin area in the northwest is higher in the maturity of organic,and the overall trend is gradually decreasing from north to south.(5)The shale oil and gas resources in the study area of the central part of the Sichuan Basin are abundant.The shale oil and gas resources are estimated by the organic thermal simulation parameter method.The maximum value of shale oil is 640,700 tons,and the minimum value is 323,300 tons.The maximum value of shale gas is 3.99 trillion squares and the minimum value is 1.99 trillion squares.The shale oil resources are estimated by pyrolysis method,the value is 688,300 tons,and the above two methods are carried out by the chloroform asphalt "A" method.A supplementary estimate of shale oil resources was obtained,with a result of 976,500 tons.