Recognizing Reservoir Compartments on Geologic and Production Timescales Through the Integration of Stratigraphic, Structure and Fluid Data in Deep-Water Reservoirs: An Example from Genesis Field, Gulf of Mexico

Sweet, Michael L.¹, Larry T. Sumpter² (1) ExxonMobil Upstream Research Co, Houston, TX (2) ExxonMobil Upstream Research Company, Houston, TX

A key objective of reservoir description is the early identification of reservoir compartments. Early recognition of compartmentalization requires the integration of structural and stratigraphic data with observations of pressure and fluid contacts. At the exploration and appraisal stage of field life static compartments (i.e., differences in fluid contacts across structural and/or stratigraphic discontinuities) may be recognized. As the field is depleted, other barriers and baffles may become apparent through observation of pressure depletion and aquifer movement.

The Genesis oil field is located in Green Canyon Blocks 205, 160 and 161, Gulf of Mexico. We explored the stratigraphic and structural controls on compartmentalization in two Pleistocene-age, deepwater reservoirs in Genesis Field (Neb 1 and Neb 3). We interpreted the oldest of these reservoirs, Neb 3, as an erosionally confined channel complex. Over a geologic timescale, Neb 3 was a single compartment, with a common oil-water contact throughout the field. As the reservoir was produced, Neb 3 development wells showed a common pressure decline trend and moderate aquifer support indicating communication in the oil column and between the oil column and the aquifer. In contrast, Neb 1 showed at least two different oil-water contacts before production started. Multiple barriers and baffles to flow became apparent with production. Aquifer support ranged from moderate to none. We interpreted Neb 1 as a channel levee complex. The connection between channels and levees appears to be poor and this is an important heterogeneity that was not previously recognized. In the case of the Neb 1 and Neb 3, reservoir architecture was the primary control on the degree of compartmentalization over both geologic and production timescales.