AAPG Annual Convention and Exhibition

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Ceiba Field, Equatorial Guinea: Leveraging 4-D Seismic for Brownfield Redevelopment


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. Using simultaneously processed and inverted 4D seismic data, we demonstrate the importance of maximizing value in a short period of time with practical, predominantly qualitative interpretation focused on establishing fundamentals and understanding sweep heterogeneity and identifying the areas of bypassed oil. After building confidence in the 4D data with statistical validation and a 3-well workover program, we fully exploit the data by executing 6 new drills, all of which validate the interpretation, engineering data, and yield 100% geologic success. We show examples of executed wells where targets were identified in areas previously assumed to be swept and where the well trajectories were designed using the 4D inversion information to avoid water sweep. Further, we demonstrate the quantitative predictability of the rock physics inversion from comparison to petrophysical results from the new wells. We illustrate improved reservoir understanding using detailed geobody mapping of both static oil accumulations and 4D-identified water sweep. We present a methodology for incorporating the 4D data and interpretations to refine Earth models and to assist with history matching. However, even with reservoir simulation models calibrated to the 4D seismic, it remains challenging to predict the dynamic response of the Ceiba reservoir when new completions are added. We will discuss these implications with unanticipated results encountered in well performance (such as rapid water breakthrough) and the lessons learned from them, providing insight in how to better develop similar deepwater fields in the future.