Effective Porosity Seismic Inversion for Porous Media Saturated with an Ideal Fluid Using Simulated Annealing

Effective porosity inversion-a key technology for lithology prediction and fluid identification- plays a significant role in oil and gas exploration. Based on the analytical expression of the vertical reflection coefficient of fast P-wave at the interface of fluid-bearing porous media, a seismic record is described as a function of the porosity by combining the quantitative relationship among rock skeleton modulus, rock matrix modulus, and effective porosity. Considering the nonlinear relationship among them, the simulated annealing (SA) method is used to solve the nonlinear inverse problem, and effective porosity inversion is realized by utilizing the reflection coefficients, porosities, and interpretation results of well logs as prior constraints. A series of numerical analyses shows that reasonable constraints can make the inversion converge rapidly to the optimal solution, and the inversion results of porosity are effective and stable and have high resolution and strong noise immunity. The calculations of well data and sandstone reservoir data further verify the practicability of this method, and the solutions are in good agreement with well log porosity.