Probabilistic Seismic-petrophysical Inversion Applied for Reservoir Characterization in Offshore Nile Delta

We apply a two-step probabilistic seismic-petrophysical inversion for the characterization of a clastic, gas-saturated, reservoir in offshore Nile delta. The first step is a Bayesian linearized amplitude versus angle (AVA) inversion in which the reflection seismic data are used to derive the elastic properties in the reservoir zone and the associated uncertainties. The estimated elastic properties constitute the input to the second step, which is a probabilistic petrophysical inversion in which we take into account the uncertainties associated with the rock-physics model, with the estimated elastic properties and with the recorded seismic data. In particular, we formulate the petrophysical inversion considering a Gaussian mixture distribution for the petrophysical properties. This allows us to properly describe the multimodality and the correlation that characterize the distribution of these properties in the reservoir zone where sand channels are surrounded by thick shale sequences. In addition, in the petrophysical inversion we test two different rock-physics models that link the elastic properties to the petrophysical properties. The first is an empirical linear model, whereas the second is a theoretical non-linear model. The synthetic and the field data inversions confirm the reliability of the two different rock physics models and the applicability of the inversion method.