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Deepwater Field Development, Offshore Angola - Reservoir Management Strategies for a Complex, Turbidite Channel Environment


Valente Silva1, Joaquim Fernandes1, Dave Goggin2, John Baillie3

(1) Sonangol P&P, Luanda, Angola (2) ChevronTexaco Overseas Petroleum, San Ramon, CA (3) Chevrontexaco Overseas Petroleum, Luanda, Angola

 The Benguela Belize - Lobito Tomboco fields, located offshore Angola in 1300-ft of water, are composed of several, deepwater, turbidite-channel complexes of Miocene age. The pools are combination structural, fault, and stratigraphic traps with cumulative STOOIP approaching 1.5 billion barrels.

High-quality, 3-D seismic allows the construction of high-resolution geologic models for each oil pool. The seismic data provided a sound basis for spatial distribution of reservoir properties high quality mapped based OOIP estimates were made using all available data. Through detailed seismic stratigraphic interpretations and seismic attribute extractions, a map-based probabilistic approach was used to understand the impact of geologic uncertainties on volumetrics . Processes were then followed to define effective porosity, irreducible water saturation, and permeability from the seismic attribute predictions calibrated using cloud transforms. Simulation models were scaled up and created for each field and sector models were developed to further understand the details of displacement and subsurface development options. The results of these simulation models and all the sensitivities run were used to gain a concensus recovery for each channel, fault block and zone within the Block 14 partnership.

This overall approach supports a consensus building methodology with structured products (maps, displacement mechanisms, profile/recovery uncertainties, recovery efficiencies, well placements, well spacing issues, recoveries by reservoir element) at specific points in the modeling process. These work products from 3-D sector and full-field simulation models allow all stakeholders the opportunity to analyze and understand the results and that form a basis for developing forecasts, creating economics and making decisions.