Print this pageDeep-Water Slump and Debris Flow-Dominated Reservoirs of the Zafiro Field Area, Offshore Equatorial Guinea
FAMAKINWA, SIMEON BOLAJI, G. SHANMUGAM, R.J. HODGKINSON, and LANE C. BLUNDELL
The Zafiro Field, discovered March 1995 and put on stream August 1996, is the first significant oil field in Equatorial Guinea. Detailed analysis of over 1500 feet of conventional cores from the Pliocene Intra-Qua Iboe (IQI) interval suggests the producing reservoir is dominated by debris flows, slumps and bottom-current reworked (BCR) sands. A deep-marine slope or base-of-slope setting is proposed.
The reservoir exhibits a mounded external seismic geometry with chaotic internal reflections. They also display various electric log motifs including blocky, fining-upward and coarsening-upward trends. The fining-upward log motif is usually a manifestation of abundant mud clasts in the upper part of the sand interval rather than an indication of shaliness. Dimensions of debris flow units estimated through seismic amplitude extraction work correlated to logs and cores, are in agreement with empirical thickness-to-width ratios (1:30-60) derived from modern and ancient examples.
The main reservoir has an average thickness of 100 feet and excellent reservoir quality with porosities in the 20-35% range and permeabilities between 1000 mD and 3000 mD. DST flow rates are over 10,000 BOPD. The IQI reservoir sands in the Edop Field area of Nigeria that occur updip from the Zafiro Field exhibit analogous depositional facies and reservoir properties. The Edop-Zafiro trend provides a test case for slope to base-of-slope systems and has implications for future deep-water plays in Equatorial Guinea.