Numerical Simulation and Characteristic Analysis of Remote Detection Acoustic Reflection Imaging Logging of Near-Borehole Fracture and Vuggy Reservoirs

Remote detection acoustic reflection imaging logging is a cutting-edge imaging technology that enables precise interpretation of fracture and vuggy reservoirs. In this study, a 3-D elastic wave time-domain staggered nonuniform grid with fourth-order accuracy in space and second-order accuracy in time utilizing the finite-difference method was developed. Numerical simulations of the acoustic field near the borehole were conducted for dipole shear wave imaging, and the effects of fracture width, distance from fracture to the borehole, and hole radius on the reflected wave in acoustic reflection imaging logging under different fillings were analyzed. The radial resolution of the acoustic reflection imaging logging was studied, and the theoretical detection range was discussed. The simulation results show that the shear wave velocity has a significant impact on the reflected wave amplitude. Fractures filled with solid present a parabolic shape as the fracture width changes, while the amplitude of the fracture reflection wave filled with fluid decreases with the increase of the distance from the borehole but does not change with the width of the fracture. The reflected wave of the vug model has the characteristics of weak energy and multiple reflections, and the numerical simulation results of fracture and vug correspond well with models. Using the knowledge of forward modeling, the interpretation of fractures and vugs within 30 m of the borehole was carried out during the actual exploration. This technology significantly improves the detection range of the reservoir near the borehole.