Study On Middle-lower Ordovician Geostress Field In SH Area,Tarim Basin

With the high production breakthrough of ultra deep carbonate reservoirs in SH area of Tarim Basin,it is proved that this area has rich oil and gas resources and good exploration prospects.Taking SH area as the research area,this paper studies the crustal stress distribution characteristics of Yijianfang Formation and Yingshan Formation in SH area,aiming at the main target layers of Ordovician Yijianfang Formation and Yingshan Formation,and comprehensively using geological,logging and seismic data.Firstly,using geological,drilling,logging,and geophysical data from the SH area,a detailed interpretation of the strike slip faults in the study area is conducted,analyzing the intersection relationship between faults and strata,as well as between faults,and establishing a three-dimensional fine structural geological model;Secondly,according to the static rock mechanics parameters obtained from the rock mechanics test results of core samples and the dynamic rock mechanics parameters obtained from the interpretation of logging data,the relationship between dynamic and static rock mechanics is analyzed,the rock mechanics parameter model is established,and the rock mechanics parameter characteristics of the target strata Yijianfang Formation,Yingshan Formation and strike slip fracture in the study area are analyzed;Finally,the crustal stress of a single well is calculated using the logging data,and the boundary conditions are inversed in combination with the regional stress background.The current crustal stress field in the study area is numerically simulated based on the finite element simulation method and combined with the 3D fine structural geological model and the rock mechanics parameter model.The crustal stress test results are used to control the quality of the simulation results,and the crustal stress distribution characteristics of Yijianfang Formation and Yingshan Formation are analyzed,The crustal stress distribution characteristics of strike slip faults and their coupling relationship with structural styles are further analyzed.Gain the following understanding:The geological data and deep seismic data of the SH area indicate that the study area has developed NE strike slip faults,with a total of 29 faults developed.The fault dip is almost greater than 80 °,and the fault displacement is small.The profile shows vertical faults,positive flower shaped,and negative flower shaped structures.Based on the characteristics of fault crossing layers,fault properties,and structural deformation,a three-dimensional fine structural geological model is obtained by processing the intersection relationship between faults and strata,as well as between faults and faults.The research on the characteristics of rock mechanics in the study area shows that the Young’s modulus of Yijianfang Formation in the study area is 41.5-65.75 GPa,the Poisson’s ratio is 0.244-0.314,the Young’s modulus of Yingshan Formation is 44-68.25 GPa,and the Poisson’s ratio is 0.242-0.287.There is a negative correlation between Young’s modulus and Poisson’s ratio.On the basis of the establishment of fine 3D structural geological model and rock mechanics parameter model,the 3D finite element simulation of crustal stress field was carried out.The simulation results show that the distribution range of the maximum horizontal principal stress in the target floor of the study area is 166-266 MPa,the distribution range of the minimum horizontal principal stress is 114-194 MPa,the distribution range of the maximum horizontal principal stress in the Yingshan Formation is 180-272 MPa,and the distribution range of the minimum horizontal principal stress is 108-202 MPa.The error between the simulated and measured values is less than 8%,and the simulation results are within a reasonable error range.The distribution range of the maximum horizontal principal stress in the target layer of the study area is 170-244 MPa for the Yijianfang Formation of the strike slip fault,115-176 MPa for the minimum horizontal principal stress,180-254 MPa for the Yingshan Formation of the strike slip fault,and 108-188 MPa for the minimum horizontal principal stress.The more developed the strike slip fault,the smaller the horizontal principal stress.From the perspective of the relationship between stress and different faults,the internal stress value of the fault zone in the study area is relatively low.Combined with the analysis of fault sliding theory,it is believed that faults at the critical sliding stress have an important control effect on oil and gas enrichment and high production.