Novel Near Wellbore Rock Typing and Upscaling Workflow to Improve Reservoir Characterisation and Modelling of Carbonates

This study illustrates a novel near wellbore rock typing and upscaling approach to obtain fit-for-purpose rock typing scheme to improve the characterisation and simulation of a highly heterogeneous offshore carbonate field, Field X. The key geological heterogeneities present in Field X were caused by late burial (mesogenetic) dissolution, such as chalky micro-porosity, macro-porosity including vuggy and moldic pores, leached stylolites and associated tension gashes. The prime challenges addressed are to incorporate the influence of diagenesis on reservoir petrophysical properties, adequately represent the multi-scale and multi-modal pore types and integrate dynamic data through rock typing. Another major issue is to upscale the petrophysical properties of the rock types to the reservoir model using appropriate geostatistical tools. The rock typing and upscaling methodology we adopted involves the geological-petrophysical classification of these heterogeneities through systematic evaluation of the key paragenetic events, and considers the crucial aspects of near wellbore modelling and upscaling. The outcome of this study has significantly improved characterization of porosity and permeability distributions and dynamic calibration in Field X. As a result, a new alternative geomodel scenario was obtained, which is now much better constrained to the reservoir geology and shows improved match to historic production data.