3D Reservoir Grid Construction and Characterization of a Deepwater Turbidite Reservoir, Angola

Ricardo P. Van-Deste
ChevronTexaco, Houston, TX

ChevronTexaco and its Block 14 partners (Sonangol P&P, TotalFinaElf, AGIP and Petrogal) have developed and applied a reservoir characterization workflow to produce integrated and detailed geologic models that have been used to reach consensus on OOIP, recoveries and development plans for the Tombua field in the deepwater Angola. Tombua is located in the eastern central portion of Block 14 in 300 meters of water and contains 10 turbidite-channel complexes of Miocene age. The pools are combination structural, fault, and stratigraphic traps with cumulative STOOIP approaching 800 million barrels. The resource base is defined by a discovery well drilled in 2001 followed by 7 appraisal penetrations drilled over the past 2 years.

The characterization workflow incorporates all well data along with high resolution 3D seismic to construct detailed reservoir maps and geologic models for each zone and channel. Routine core analysis and wireline log analysis were integrated with core derived reservoir facies in an iterative approach to define effective porosity, irreducible water saturation, and permeability for reservoir and non-reservoir. Seismic attribute extractions and depositional models provided a sound basis for spatial distribution of reservoir properties for detailed 3D geological models as well as for high quality mapped based OOIP estimates.

The earth models will then be scaled up for simulation to evaluate recoveries from both primary depletion and secondary through water injection.