Fit-for-Purpose Reserves Assessment for Lucapa Field, Block 14 Deepwater Angola

Kathleen Mabe¹, Roger Severson¹, Jay Byers¹, Danny Clarke¹, and Pat Burdett^2
1South Africa Business Unit, Chevron, Houston, TX
²Decision Strategies, Houston, TX

Lucapa field was discovered in 2006 when the Lucapa-1 well encountered oil in Miocene channel sands on the northern slope of the Congo Canyon in deepwater. Producing rules for Block 14 Angola require the first oil lifting to be within six years of declaring a commercial development. In the current competitive environment, deepwater developments are challenged by taking over three years for facility construction which leaves less time to appraise, assess reserves, define profiles, and choose the facility concept. A fit-for-purpose reserves assessment method was developed to define a probabilistic range in reserves for Miocene reservoirs. In 2007-8, four appraisal wells are drilled to define the development. A conceptual development plan for the Lucapa field is required to be submitted to the Block 14 Concessionaire in the 4th Qtr 2008. The conceptual development plan documents:

- reservoir characterization
- oil in place, recoveries, and profiles
- reservoir basis of design defining the number of wells, injector/producer spacing, well paths, and completion types
- uncertainty management plan
- facility concept
- economics

A systematic approach involving expert interviews, sensitivity analysis, analogue databases, and Monte Carlo techniques were used to capture the uncertainty ranges for:

- Net to Gross
- Depth uncertainty
- Porosity and water saturation
- Fluid contacts and properties
- Fault seal
- Baffles
- Permeability
- Kv/Kh
- Relative permeability

Reservoir modeling techniques are streamlined to quickly assess profiles for the facility concept to be defined in less than a year after the fourth appraisal well is drilled. Additional challenges are associated with drilling in water depths of 3000-6000 feet on the slope of the Congo Canyon, injectites, and complex structure associated with multiple salt domes.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery