Heavy Oil Characterization for Development of Gabela Field, Deepwater Block 14 Angola

William Crane¹, Joy Roth³, Kathleen Mabe¹, Rosaria Ambriz², Cengiz Satik¹, and Todd Lackey^1
1South Africa Business Unit, Chevron, Houston, TX
²Sonangol, Luanda, Angola
³Chevron, Lagos, Nigeria

The Gabela-1 well discovered a heavy oil accumulation trapped stratigraphically in late Miocene turbidites within a submarine canyon in Angola. Challenges to the development include complex stratigraphy and multiple reservoir compartments. The canyon’s high energy environment caused multiple occurrences of erosion and deposition, yielding complex channel geometries. Episodic slumping, debris flows, and poor sorting results in reservoir compartmentalization. Multiple fluid contacts and geochemical analysis of oils are used to define reservoir separation between wells and channels.

Reservoir uncertainties are being addressed by simulating a faulted reservoir model with multiple fluid models. Reservoir models capture the complexity of the stratigraphic and structural framework to evaluate recoveries from water injection. The project team is also linking future data acquisition with uncertainty management plans to reduce risk and ensure capital stewardship. In 2006, appraisal drilling delineated the resource base and defined an additional reservoir compartment. New 3D seismic acquired and processed in 2006-7 is being used to update channel interpretations for reservoir modeling. Conceptual reservoir basis of design includes long horizontal completions with electric submersible pumps in a subsea environment. Facilities concepts include potential tieback to new Block 14 discoveries as well as the use of polymer and multi-laterals.

Angola Block 14 deepwater is operated by Chevron, through its subsidiary Cabinda Gulf Oil Company, with partners Sonangol P&P, Total, ENI, and Galp. The objective of the study is to define a reservoir basis of design and facility concept to economically develop Gabela heavy oil reserves. Chevron has utilized many of the lessons learned from other Block 14 producing fields along with company experience in heavy oil deepwater developments.

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