Rock physics model-based seismic inversion

We demonstrate how to interpret seismic amplitudes for lithology, porosity, and pore fluid by systematically perturbing these properties in the earth, calculating the corresponding elastic properties, and matching the synthetic seismic traces with the real data. A key component of our technique is a site-specific deterministic rock physics model that links the petrophysical to elastic properties. This model also imposes geologically consistent constraints within the lithology-porosity-fluid space. The perturbations are implemented through exhaustive Monte-Carlo simulation of these petrophysical parameters within the rock physics model. The results are inter-related probabilistic values of lithology, porosity, and saturation that may stand behind the seismic amplitude under examination. Trace-by-trace probability density functions of the petrophysical parameters allow the uncertainty in the reservoir properties to be quantified. We demonstrate this model-based inversion technique on well and seismic data from offshore South Africa.