Direct Probabilistic Inversion with Non-Stationary Rock Physics Depth Trends – a North Sea Demonstration

A novel integrated exploration workflow combining geological constraints (depositional and burial history), calibrated rock physics modelling and direct probabilistic inversion has been demonstrated on data from the North Sea. The main goal is to predict reservoir facies and fluids for key targets from observed seismic AVO data and support prospect generation via calibration to well data and geologic trends/scenarios. The resulting facies and fluid probabilities show evidence for good quality reservoir sandstones filled with gas in an undrilled location in an area with several nearby recent discoveries in the same stratigraphic interval, but at a more deeply buried location than previous discoveries. The derived facies predictions are consistent with seismic AVO-derived relative acoustic impedance and Vp/Vs attributes. This study demonstrates how the understanding of key geological processes are directly implemented in Bayesian probabilistic inversion through non-stationary rock physics thereby decreasing uncertainty.