Ceiba Field, Equatorial Guinea: Breathing New Life Into an Old Field

Abstract

The Ceiba Field, Equatorial Guinea hydrocarbon reservoir is composed of moderate energy, weakly confined, stacked muddy leveed channel turbidite complexes deposited in an intra-slope mini-basin during the Campanian. The four-way closure is bound on the top and base by erosional unconformities, and is internally compartmentalized by faulting, shale drapes, interchannel zones, downcutting, and MTDs. As is typical with many West Africa post-salt fields, the reservoir has exceptional seismic illumination with conventional towed streamer data and generally exhibits hydrocarbon-related amplitude anomalies, which are used in reservoir characterization. Ceiba was discovered by Triton Energy in 1999 and first oil was achieved in November 2000 via a subsea gathering system. The field development can be divided into two phases: Phase I (1999 – 2008) and Phase II (2009 – 2013). Our understanding of the field has evolved from the first phase of development when the field was believed to be a relatively homogeneous reservoir with well-connected sands into a field with highly variable reservoir quality, complex compartmentalization and connectivity, and permeability highways, requiring continuous infill drilling. The interaction of the waterflood with the complex Geology yielded an incomplete development in Phase I, which left the opportunities exploited in Phase II. These include behind-pipe oil accessed via recompletions, bypassed/stranded oil targeted with new wells, and water injection managed to arrest production decline, improve sweep efficiency, and maximize recovery. Recent 4D reprocessing of three available seismic surveys has greatly improved the subsurface imaging of Ceiba. Improved imaging is complemented by elastic and rock physics inversion products, which are used as the primary driver for the second phase of development. The new data were understood in a series of steps: First, the 3D seismic was surgically interpreted. Amplitude extractions were used to illustrate the deposystem morphology of the reservoir and place it in a sequence stratigraphic framework that ties well data and dynamic performance. Second, the rock physics inversion was statistically validated using comparisons to existing wells. Lastly, the 4D observations were validated with three workovers. Logging (RST, GR) and well performance confirmed the 4D seismic observations of the highly heterogeneous sweep efficiency within the individual reservoir units.

AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014