Batanga Sandstone Reservoir: A Turbidite Stratigraphic Trap
D. R. Smith, S. B. Desantis, L. A. Dunne, B. L. Faulkner, R. E. West, 1991. "Batanga Sandstone Reservoir: A Turbidite Stratigraphic Trap", The Integration of Geology, Geophysics, Petrophysics and Petroleum Engineering in Reservoir Delineation, Description and Management, Robert Sneider, Wulf Massell, Rob Mathis, Dennis Loren, Paul Wichmann
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A synergistic approach was instrumental in conducting an exploitation study of the Upper Cretaceous Batanga reservoir of Gabon. The Batanga reservoir is an oil productive, turbidite channel sequence deformed by syn- and post-depositional salt piercement and intrusion. This study illustrates how several techniques derived from geological, geophysical, petrophysical, and reservoir engineering disciplines were integrated into a comprehensive description of this reservoir.
These Oguendjo “B” and “C” fields were discovered in 1981. Nineteen wells have produced 38 MMBO from stratigraphic traps associated with salt diapirism. Oil column heights and productive acreage average 165 feet and 650 acres, respectively, in these two fields.
Regional and local depositional trends were interpreted from isopach maps derived from three dimensional seismic data and from true stratigraphic thickness (TST) log cross sections. Salt uplift contemporaneous with deposition resulted in thicker sands on the flanks of salt piercements. Five separate depositional sequences were identified in each field and are composed of laterally discontinuous proximal channel, medial levee, and distal overbank facies. Using a statistical analysis of wireline log data, the oil productive channel and levee facies were discriminated from non-reservoir rock.
Log analysis and net pay identification of thinly bedded turbidites was accomplished using the “Dual-Water” model for water saturation calculations and the M-N crossplot technique for V-shale calculations. Routine and special core analyses further refined these models. True Vertical Thickness (TVT) logs were used to generate net pay and hydrocarbon pore volume (HPV) estimates for each well.
An estimate of the original oil-in-p1ace based on isochore