Reservoir Characteristics And Its Main Control Factors Of J₂s² The In The Wubaochang Area Of Northeast Sichuan Basin

The study area is located in the Wubaochang area in the northeastern part of the Sichuan Basin,and the J2s reservoir in the area is a dense sandstone reservoir.There is an urgent need to study the evaluation of the dense gas potential of the Wubaochang area and provide exploration suggestions for finding reserve reserves in the Wubaochang area.In this study,the lithological characteristics of J2s2 reservoir,the spatial characteristics of J2s2 reservoir storage,and the physical characteristics of J2s2 reservoir were systematically studied using core thin section data,physical data and 3D seismic data in the study area,and the main controlling factors of J2s2 reservoir development were clarified,based on which the distribution of J2s2 effective reservoir was analyzed.The study shows that:1.The J2s2 in the study area is divided into three subsections from the bottom to the top,gradually changing from delta front edge to delta plain deposition.The lowermost sub-section J2s21 is a submerged divergent channel sand body of the delta front,the central sub-section J2s22 is a submerged divergent channel sand body of the delta front and partly a plain margin sand body,and the uppermost sub-section J2s23 is a delta plain branch channel margin sand body.2.The sandstone composition of the sandstone in the J2s2 is less mature,mostly lithic feldspar sandstone and feldspar lithic sandstone,with quartz content between 38%and 82.5%,average content 61%;lithic fragment content ranges from 4.5%to 40%,with an average content of 20%;and the feldspar content ranges from 7%to 31%,with an average content of 19%.Wave-like interlacing laminations are visible on the core,and some wedge-like interlaminations are seen.The structure is predominantly sub-angular,with moderate to high structural maturity.The miscellaneous base in the fillings is mainly clay minerals with 12%content.The zeolite cement is nearly 2%;the chlorite content is about 0.2%.3.The J2s2 in the study area is a typical dense sandstone reservoir.The average porosity is 3.66%,and the lower limit of porosity is 3%according to the minimum flow pore throat radius method.The permeability is mainly concentrated in the range of 1×10-3md.The primary interstice is short,and the secondary pores are mainly pores,with inter-and intra-grain solution pores developing,and microfractures can be seen under the microscope.4.The reservoir physical properties of J2s2 are controlled by two major factors:sedimentary conditions and diagenesis.The middle-coarse-grained sandstone in branch channels has the best physical properties.The compaction intensity in diagenesis is high,and the porosity reduction is 27.91%on average,which is the main reason for the densification of the 2nd member of Shahejie Formation.The amount of porosity reduced by cementation is relatively small,the average amount of porosity reduced by cementation is 3.21%,and the amount of porosity increased by dissolution is 3.08%.5.Combining the seismic reservoir inversion and the spreading of the sedimentary phase zone,the effective reservoir in the J2s2 is portrayed.The results show that the reservoir is most developed in the J2s21,which can reach 40m and is within the micro-phase of the submerged diversion channel,and the reservoir continuity is good.The next is the J2s22,which is in the submerged divergent channel micro-phase with the maximum reservoir thickness up to 20m.The J2s23 is in the delta plain channel micro-phase with the thickest reservoir up to 20 m,and the continuity is slightly less.