Predicting 3D heterogeneous in situ stress field of Gaoshangpu Oilfield northern area, Nanpu Sag, Bohai Bay Basin, China

Abstract

Research on in situ stress has important theoretical and practical significance for the exploration and development of oil and gas reservoirs. The orientation and magnitude of in situ stress in the Gaoshangpu Oilfield northern area (GO-NA) were analyzed using borehole breakout data and acoustic emission measurements. Mechanical experiments, logging interpretation, and seismic data enabled spatial characterization of rock mechanics parameters. A 3D geological model and 3D heterogeneous rock mechanics field of the GO-NA were constructed. Petrel and ANSYS modeling provided detailed prediction of the 3D stress field in the GO-NA. The results indicate that the maximum horizontal stress orientation in the GO-NA is generally ENE–WSW-trending, with significant changes in in situ stress orientation within and between fault blocks. Along surfaces and profiles, stress magnitudes are discrete and in situ stress is of the Ia-type. Observed inter-strata differences were characterized by five different types of in situ stress profile. Faults are the most important factor in the large distributional differences in the stress field of reservoirs observed within the complex fault blocks, significantly affecting magnitudes and orientations in the stress field. The next most important influence on the stress field is the reservoir’s rock mechanics parameters, which affect in situ stress magnitudes. A strong linear correlation exists between reservoir depth and in situ stress magnitude. This technique provides a theoretical basis for more efficient exploration and development of low-permeability reservoirs. It also serves as a reference for the detailed prediction of inter-well in situ stress in regions with similarly complex fault blocks.