Reservoir Characterization and Quality Control of the Cretaceous Pinda Formation in the Mafumeira Field; Block 0, Angola

Jessica M. Ali-Adeeb¹, Peter Sixsmith¹, Bryan Bracken⁴, Sunday Shepherd³, and Robert Scamman^2
1Exploration & Reservoir Characterization Services, Chevron, San Ramon, CA
²Asset Development, Chevron, Houston, TX
³Exploration & Reservoir Characterization Services, Chevron, Houston, TX
⁴Earth Sciences R&D, Chevron, San Ramon, CA

The Albian Pinda Fm, Angola, is a marginal marine, mixed carbonate-clastic system deposited during growth faulting and rafting during the opening of the S. Atlantic during the Cretaceous. Pinda reservoirs are characterization challenges due to complex marginal- to shallow-marine reservoir architecture, mixed carbonate/siliciclastic mineralogy, and lack of clear seismic facies. The Mafumeira Pinda reservoir extends >15 kms along a rafted fault block where the full Pinda section is more than 3000 ft thick.

A stratigraphic characterization of two 1000+’ cores from the Mafumeira Field in 2003 tied the stratigraphic framework to four other uncored wells in the field. The purpose of the study was to improve our understanding of reservoir stratigraphy in the field and improve predictions of reservoir performance for evaluating development alternatives. Detailed core and stratigraphic analysis indicated progradational cycles of marine shelf/shoreface sediments overlain by lagoon, tidal flat/redbed and fluvial channel sediments. Each cycle is capped by a transgressive surface of sub-regional extent, forming the foundation of the sequence stratigraphic framework.

A further appraisal well was drilled in 2007 to address reservoir uncertainty issues, and 1000’ of new core was taken. Analysis of the core was integrated with the existing stratigraphic framework. The results from the latest well reinforced that framework, clarified several stratigraphic uncertainties, and identified additional reservoir targets. This framework was then used to evaluate dynamic engineering data and guide interpretation of poor resolution seismic data for the construction of field-scale reservoir models.

The addition of this new data illustrates the necessity of having good well control as well as wireline-log and core data to fill our gaps of understanding in field-scale reservoir characterization.

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