Improvement of pressure-saturation changes estimations from time-lapse PP-AVO data by using non-linear optimization method

First-order approximations of seismic parameters in AVO intercept and gradient changes are not sufficient to estimate changes in saturation and effective stress accurately. Analysis from an unconsolidated reservoir and a compacting reservoir show that we need to consider higher order terms in seismic parameters to reduce the inaccuracy of the estimates. Furthermore, improper approximation of rock physics parameters increases the error in the estimates. Here, we implement a non-linear optimization method to estimate changes in saturation and pressure using reflectivity equation directly. We test the applicability of this non-linear optimization method on synthetic data for both the above-mentioned reservoir scenarios over a wide range of realistic saturation and pressure changes. We observe that the inversion results using the new method are reasonably good for both reservoir scenarios.