Seismic Petrophysics of Siliceous Deep-Sea, Opal-Bearing Sediments for Successful Play-Based Exploration

This integrated analysis of complex, seismic petrophysical data sets will foster future exploration and development by (1.) differentiating seismic anomalies caused by fluids, diagenetic events or overpressure; (2.) by discriminating reservoir from non-reservoir; (3.) by predicting spatial distribution of pay thickness. Specifically, this work focuses on the analytical integration of complex data sets from Upper Cretaceous, Opal CT-bearing deep-sea sediments. The analysed data includes: cores, mud logs, wireline and PLT data, seismic maps, isochores and paleo-facies maps. Quantitative interpretation of deep-sea siliceous reservoirs requires sensible rock physics analysis due to (1.) the complexity of diagenetic processes; (2.) changing mineralogical assemblages; (3.) the effect of Opal phase transitions on physical and elastic properties. Rock Physics analysis for each individual interval is conducted to exclude possible averaging and/or duplication of petrophysical property values, thus, properly discriminating reservoir from non-reservoir. Calibration of rock physics results provide a good match with the well test. Results from Rock Physics analysis demonstrate that combined, bivariate analysis of elastic properties helps separate intervals of high-porosity, hydrocarbon-charged deep-sea sediment from water-wet anomalies. Uncertainty analysis of results identifies those key geological & sedimentological factors, that drive seismic expression and influence reservoir properties, and, ultimately, spatial prediction of pay thicknesses.