| The fractured tight sandstone reservoir of the Lower Cretaceous Bashijiqike Formation is the key field in the exploration and development of ultra-deep natural gas in the Kuqa Depression,and its main gas producing sections are the first member of Bashijiqike Formation(K1bs1)and the second member of Bashijiqike Formation(K1bs2).It is of great significance for the exploration and development of ultra-deep natural gas in this area to identify the fracture development characteristics and the vertical and horizontal distribution law.In this paper,by using core,thin section,borehole wall imaging logging,conventional logging and 3D seismic data,machine learning and numerical simulation of reservoir geomechanics,on the basis of analyzing the characteristics and influencing factors of reservoir fracture development,the longitudinal and transverse distribution law of tight sandstone reservoir in Bashijiqike Formation of Kesen Gas field is predicted and evaluated.Structural fractures are mainly developed in this area,among which high Angle structural shear fractures are the main ones.The tectonic fractures are mainly struck near NE-SW,NW-SE,NEE-SWW and N-S,and the dominant directions of effective fractures are near N-S,NW-SE and NEE-SWW.The degree of fracture development is mainly affected by structural factors such as structural location and fault.The higher the position of structure and the closer the distance from fault,the higher the strength of fracture development.The second is the depositional factor.The fractures are mainly developed in siltstone,and the fractures are most developed in the sedimentary microfacies of distributary channel.The fracture density increases with the decrease of rock mechanical layer thickness.The fractures are mainly unfilled and the filling property of K1bs1 is higher than that of K1bs2.The single well fracture identification by ensembling Fracture Indicator Parameter method,Random Forest method,Nuclear Principal Component Analysis method and Support Vector Machine method shows that the fracture development strength of the K1bs2 of well A1-A8 is greater than that of the K1bs1 in Kesen gas field.In western well A9,A10,A11 and A12,the fracture development strength of K1bs1 is greater than that of K1bs2.According to the fracture plane prediction results of the Gradient Boosting Decision Tree based on3 D seismic attributes and the numerical simulation method of reservoir geomechanics,the fracture development degree in the west of Kesen gas field is higher than that in the east,and the fracture development degree in the south is higher than that in the north. |
