High-Resolution Reservoir Modeling of a Deepwater Channel Complex with Thin Beds, Zafiro Field, Equatorial Guinea

Schwans, Peter¹, Marty Cohen², Kim Zauderer², Stephen D. Knapp², Ted C. Lukas³ (1) Devon Energy Company, Houston, TX (2) Devon Energy Company, (3) Consultant, Houston, TX

The Zafiro Field of Equatorial Guinea comprises stacked channel complexes of Miocene-Pliocene clastics deposited in the mid to lower slope position of the Niger Delta. Detailed reservoir models are being built to better understand facies distribution and the impact of thin beds on reservoir performance.

Models integrate 4th - 5th order seismic surfaces, geobodies interpreted in VoxelGeo, petrofacies calibrated to core, and thin-bed data from image logs. The channel complex consists of three multi-stage channels with complex margins. Three reservoir facies are recognized: (1) Massive pebbly sandstones deposited by debris flows; (2) Medium to fine grained sandstones deposited as debris flows and turbidites; and (3) Interbedded sandstones, siltstones, and shales deposited in the proximal overbank by turbidites. Distinct e-log facies or petrofacies calibrated to cores were brought into the modeling process as facies-specific probability curves. The relationship of seismic amplitude to reservoir facies was used to populate the model. Geobodies interpreted in VoxelGeo allow better definition of near-channel overbank areas. The geological model captured the connectivity between wells. The dynamic model evaluated the performance of thin bed regions in the proximal overbank. A history match of the production performance at all wells was achieved primarily by adjusting net-to-gross values in the gas cap. Shut-in pressures, water cuts, and GOR data were all matched successfully at each well.