Rock Pore Structure Parameters Estimation Via Pre-Stack Inversion

Accurate rock physics parameters can help geophysicists to identify reservoir characteristics and percolation distribution of subsurface media, which is of great significance to evaluation and development of hydrocarbon reservoirs. With the help of seismic rock physics models, the elastic parameters directly related to seismic reflection coefficients can be computed via prestack inversion. However, this inversion process is nonlinear, which results in difficulties in directly computing the rock physics parameters from seismic data. By using the theory of ellipsoid modeling in material mechanics, we first propose a new forward modeling method, and establish a new approximate formula for prestack seismic reflection coefficient with pore structure parameters as the main variables. The pore structure parameters include porosity and equivalent pore aspect ratio (EPAR). A nonlinear optimization strategy is implemented for simultaneous inversion of seven parameters, including modulus, density and pore structure parameters. Tests with synthetic data and real field data verified the effectiveness of the proposed pore structure parameters inversion method and strategy. According to the results of inversion, we interpret the area with low porosity and low aspect ratio as fracture development zone and predict the distribution of carbonate reservoirs.