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