In situ stress field evaluation of ultra-deep carbonate reservoir: a case study of Ordovician strata in the Shunbei 5 strike-slip fault zone, Tarim Basin, NW China

Carbonate reservoir is the focus of oil and gas exploration and also the subject of much research in the world. High-yield industrial oil and gas flow has been found in the fault-controlled carbonate reservoirs of the Middle Lower Ordovician in the Shunbei area. In the process of drilling and development, this type of reservoir faces many problems closely related to the current stress state, which need to be solved urgently. In this paper, the direction of the maximum horizontal principal stress is determined by using the global positioning system (GPS), the azimuth of fast shear wave propagation, and borehole enlargement. In addition, under the calibration of acoustic emission experiment results, cross-dipole logging data are used to evaluate the in situ stress in the study area. According to the results of the rock mechanics experiment and logging interpretation, the conversion relationship between dynamic and static parameters of rock mechanics is established. Finally, according to the fault and horizon interpreted by 3D seismic data, a 3D geological model of the study area is established. Under the constraint of logging interpretation and experimental results, the stress field in the study area is simulated by the iterative boundary element method. The simulation results show that the distribution of the in situ stress field is affected by the arrangement of faults. From the map view, it shows the segmentation along the fault strike; that is, different segments show different characteristics. In the vicinity of strike-slip faults, the principal stress direction is deflected to varying degrees. The relative error between the simulated value and the measured value is less than 10%, which verifies the reliability of the numerical simulation results. The research results can provide a reference for the determination of optimal mud weights, the optimization of wellbore trajectory, and the selection of acid fracturing operation parameters.