--> --> Infill Evolution of a Ponded Basin and Implications for Reservoir Development, Gulf of Mexico

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Infill Evolution of a Ponded Basin and Implications for Reservoir Development, Gulf of Mexico


An intraslope mini-basin in the Gulf of Mexico is host to a mature prolific multi-reservoir field that has been in production since 1996. During the ponding stages in the Late Miocene the basin recorded high sedimentation rates and the occurrence of cycles of bypass and backstepping with reservoir architectures dominated by channel and lobe complexes. During deposition of the sediments incipient salt diapirism contained and deflected channelized flows that entered the mini-basin. A main channel system traversing the basin from northwest to southeast and at oblique angle to the sill has been identified in the subsurface as a key element of the reservoirs architecture. During erosive conditions the channel reached the size of a canyon with bypass beyond the mini-basin. In ‘highstand’ conditions the channel experienced backfilling and migrated laterally close to the diapir. In the middle and marginal portions of the mini-basin the unconfined flows deposited lobes that filled the space by compensational stacking. Fluctuations in sedimentation rates, topography and accommodation space influenced the scale of lobes and internal arrangement of bedforms. The resulting architecture of the reservoirs involves different scales and magnitudes of heterogeneity with a varying impact depending of the recovery process. For a reservoir deposited towards the end of an infill cycle, the reservoir scale heterogeneity is manifested under depletion as uneven pressures and sweep due to the presence of stratigraphic baffles. The baffles comprise inter-lobe shales and shale drapes along migrating channels that together with the laminated turbidites further reduce the reservoir kv/kh. An integrated study to evaluate opportunities to increase the ultimate recovery made use of models at different scales to quantify the impact of key uncertainties under different scenarios.