The analysis of shale lamellation crack via rock physics modelling

Abstract The emphasis on oil and gas exploration in shale has persisted for several decades. Significant advancements have been achieved in onshore shale exploration and development. The reservoir features include lamellation cracks, low porosity, a significant disparity between horizontal and vertical permeability, and a complex pore structure. It is crucial to elucidate the interrelationship between elastic and physical parameters in shale reservoirs. Based on an anisotropic background medium, a shale rock physics modelling method for lamellation cracks is proposed in this paper. The effects of lamellation cracks are compared and analysed through the rock physics model, which indicates that the lamellation cracks have a considerable impact on the anisotropy of the shale. The length and number of lamellation cracks significantly influence the Vp/Vs ratio, and this pronounced variation indicates the presence of higher-quality reservoirs. Finally, the predicted velocities were compared with the measured velocities derived from logging data. The high agreement between observed and predicted values confirms the validity of the rock physics model in calculating velocities, elastic parameters, and brittleness indices. The method can be used as a bridge in the characterization of unconventional oil and gas reservoirs.