Petrophysical inversion of pore and fracture aspect ratios in complex fractured-vuggy reservoirs using TGCOA algorithm

Accurately acquiring elastic and anisotropic parameters is  critical for hydrocarbon prediction. Studies have shown that pore and fracture aspect ratios significantly influence the elastic and anisotropic properties of rocks. However, obtaining accurate pore aspect ratio data is extremely difficult and costly, and conventional logging data typically lack this information. Consequently, pore and fracture aspect ratios are generally assumed to be constant based on experience, which does not accurately reflect the actual geological conditions of the formation. To address this limitation, this study proposes a nonlinear petrophysical inversion method based on the Tetragonula Carbonaria Optimization Algorithm (TGCOA), an algorithm inspired by the nest-building and temperature-regulating behavior of tetragonula carbonaria, notable for its structural simplicity and fast convergence. First, a complex fractured-vuggy petrophysical model and inversion objective function are developed by integrating the Xu-White dual-pore model with the Eshelby-Cheng model. Then, constrained by measured acoustic logging data, the TGCOA global optimization algorithm is employed to perform nonlinear petrophysical inversion, solving for the pore and fracture aspect ratios. Finally, these estimated ratios are used as inputs for the petrophysical model to calculate the elastic and anisotropic parameters of rocks. This method comprehensively utilizes various well-logging data to obtain more accurate elastic and anisotropic parameters. Application of the proposed approach to field data in eastern China demonstrates its high computational efficiency and accuracy.