Coupled inversion of elastic-seismic data for petrophysical and pore-geometry properties

Seismic petrophysical inversion extracts petrophysical properties from seismic reflections, but conventional methods typically assume uniform pore structures, which limits their effective application in complex-pore reservoirs. Conventional inversion methods using either elastic or seismic data suffer from cumulative errors or low resolution with poor robustness to noise. To address these issues, we propose a coupled inversion method to simultaneously estimate porosity, fluid saturation, mineral content, and the equivalent pore aspect ratio using both elastic (P- S-wave velocities and density) and seismic (amplitudes of different angle gathers) data. The method adopts a Bayesian linear inversion approach with a seismic- petrophysical linearized forward model that represents pore complexities by including the pore aspect ratio as one of objective parameters to be estimated. The inversion is conditioned on coupled elastic and seismic data. We conduct a comparison between the proposed coupled inversion and conventional petrophysical inversion techniques, and we demonstrate that the proposed method improves the inversion accuracy and robustness with respect to noise. Moreover, we also define the initial model of petrophysical parameters required for the linearized inversion. This work provides an efficient and stable petrophysical inversion method for reservoirs with complex pore structures. The inversion output is a model of petrophysical properties of rock, fluid, and fracture properties.