Numerical simulation of ultrasonic wave transmission experiments in rocks of shale gas reservoirs

Abstract

Shale gas reservoirs have risen in importance in China’s new power source exploration and development program. The investigation of the propagation of ultrasonic waves in shale forms the basis for the full waveform application of acoustic logging data to the exploration of shale gas. Using acoustic wave theory, initial conditions, vibration source conditions, and stability conditions are developed in combination with experimental background of ultrasonic wave transmission. With improved boundary conditions, we performed numerical simulations of the ultrasound transmission experiments in shale using the high-order staggered-grid finite difference method (second-order in the time domain and fourth-order in the space domain). With programs developed within MatLab, the results obtained from numerical simulations agree well with experimental results based on physical models. In addition, using snapshots of the wave field that give a microscopic perspective, the propagation laws for ultrasonic waves can be analyzed. Using this method, human error is avoided, transmission experiments costs can be reduced and efficiency improved. This method extends the scope of experimental investigations regarding the transmission of ultrasonic waves in a shale gas reservoir with increasing stratification, and thus has great theoretical value and practical significance.

Anisotropy and Energy Evolution Characteristics of Shales: A Case Study of the Longmaxi Formation in Southern Sichuan Basin, China

“…Wang et al [11] performed mechanical experiments on Longmaxi Formation shale in the Changning area, Sichuan Basin, and studied its anisotropy through longitudinal and transverse wave tests. Chen et al [12] studied the relationship between shale acoustic velocity, acoustic attenuation coefficient, and bedding angle using a numerical simulation method. Xu et al [13] systematically studied the influence of the shale bedding structure on ultrasonic characteristics by using the second-order time and fourth-order space staggered-grid finite difference method.…”