Genesis field, Gulf of Mexico: Recognizing reservoir compartments on geologic and production time scales in deep-water reservoirs

摘要

In this study of the Genesis field, a deep-water Gulf of Mexico oil field, we used log, seismic, and preproduction pressure data to identify static reservoir compartments. Static compartments are defined by boundaries that, over geologic time, are barriers to fluid flow. Within a static compartment, the contact between two fluids will settle at a single elevation. We then evaluated production data, including pressure data from permanent downhole gauges, as a check on our static model and to identify dynamic compartments. Dynamic compartments are defined by boundaries that are not effective barriers to fluid flow over geologic time, but impede flow to the extent that they have a significant impact on contact movement or pressure depletion during production. Having defined static and dynamic compartments, we explored the stratigraphic and structural controls on these compartments in three deep-water reservoirs of Genesis field. The oldest of these, Neb 3, is interpreted as the deposits of an erosionally confined channel complex. Neb 3 has a common oil-water contact throughout the field. During production, Neb 3 development wells showed a common pressure decline trend and had moderate aquifer support. The Neb 2 reservoir is interpreted as the deposits of a muddier, more poorly amalgamated channel complex. At least two different original oil-water contacts were observed in this reservoir before the start of production. Production data also indicated greater com-partmentalization in Neb 2 than that observed in Neb 3. Our pre-production analysis of the Neb 1 reservoir identified at least two different oil-water contacts. With production, multiple barriers and baffles to flow became apparent. Aquifer support ranged from moderate to none. We interpret Neb 1 as the deposits of a channel-levee complex. The connection between channels and levees in Neb 1 appears to be poor. Overall, the stratigraphic architecture of these reservoirs was the underlying control on the degree of compart-mentalization over both geologic and production time scales, with structure (faulting) exerting a lesser control and primarily acting to enhance vertical connectivity between reservoirs via juxtaposition.