--> Abstract: Reduction of Stratigraphic Uncertainty from Discovery to Production in the Agbami Field, Deepwater Nigeria, by Janet L. Murphy, Eric Tuitjer, Robert Crown, Monday Ovuede, Dave Goggin, Mike Richey, and Ning Liu; #90082 (2008)

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Reduction of Stratigraphic Uncertainty from Discovery to Production in the Agbami Field, Deepwater Nigeria

Janet L. Murphy1, Eric Tuitjer2, Robert Crown2, Monday Ovuede2, Dave Goggin3, Mike Richey4, and Ning Liu5
1Earth Science Research & Development, Chevron, Sugar Land, TX
2Nigeria Mid-Africa - Agbami Project, Chevron, Lagos, Nigeria
3Reservoir Management Framework, Chevron, Houston, TX
4Nigeria Mid-Africa - NOJV, Chevron, Houston, TX
5Reservoir Performance Services, Chevron, Houston, TX

The deepwater Agbami field, located offshore Nigeria, was discovered in 1998. Four appraisal wells in the following three years confirmed the discovery and led to the initiation of a FEED/Bid process in 2001. Four more wells were drilled prior to the project sanction and unit agreement in 2004. During that time the subsurface view of the field was evolving. Considerable uncertainty was carried with respect to the net-to-gross as well as the connectivity of the sands in the field. The Field Development Plan, which allowed for a phased development of the field, specified the approximate locations and types of wells for the three stages of drilling. The Stage 1 wells, to be completed prior to first oil in mid 2008, included 11 producers, 3 gas injectors, and 3 water injectors. As the wells were drilled, core, log, and pressure data were obtained and used to refine the stratigraphic understanding of the reservoir layers. The subsurface picture of the turbidite systems evolved as the wells were drilled. Each successive well position was reevaluated and its location was optimized prior to drilling. Changes in the stratigraphic understanding of the turbidite systems led to changes in the modeling approach and subsequent revisions in the production forecasts.

Interwell pressure tests were conducted during the well completion phase in order to ascertain connectivity across faults and across channel axis fairways. Outcrop analogues and shallow high resolution seismic images were also used to help clarify the subsurface picture and estimate the degree of connectivity within the reservoirs. Remaining uncertainty still exists in the western end of the field where poor seismic data, sparse well control, and a significant change in the sand distribution patterns suggest additional drilling will be needed in order to clarify the potential of the western reserves.

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