Novel Deep Pressure-Dependent Shale Anisotropy Petrophysical Modeling and Exact VTI Reflection Coefficient

Research on deep fractured shale petrophysics is crucial for advancing shale seismological mechanisms and guiding the exploration and development of unconventional shale gas and oil. However, the petrophysical laws governing deep shale remain inadequately understood, as current studies often fail to fully consider the combined effects of deep pressure, compaction, and micro-pore structure. To address these limitations, a new anisotropic petrophysical model for deep shale is developed based on the assumption that shale behaves as a VTI (Vertical Transverse Isotropy) medium. This model incorporates the typical effects of deep effective pressure along with the characteristics of microscopic pore structures. Furthermore, the pressure-dependent exact PP-wave reflection coefficient equation for VTI media is derived by integrating the exact Ruger VTI equation. This provides a robust theoretical foundation for pre-stack inversion to predict the pressure and hydrocarbon-bearing characteristics of deep shale formations. The rationale and effective pressure sensitivity of the proposed model are validated through forward analysis, demonstrating its potential for enhancing deep shale characterization.