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ABSTRACT
The purpose of this study is to re-evaluate X field, build a robust velocity model for structural depth map generation for all reservoir intervals, calculate resource volumes and identify new prospects that could be matured and estimate their volumes. The geological consistency of this model required a cross domain integration of seismic data, well log data and subsurface knowledge across the various subsurface disciplines namely, Geology, Geophysics, and Petrophysics. Six reservoirs were mapped from the well correlation carried out across the seven wells in the NE-SW Direction. The occurrence and distribution of the lithostratigraphic units appear to reflect influence of basin morphology and sea level variation. Depositional environments were reconstructed using well log information and other available geologic information. The depositional environments were inferred, and a conceptual model was generated from the gamma ray log shapes identified on the gamma ray log motifs in combination with the density- neutron trends principle. The interpretation of the depositional environment using the logs show shoreface characteristics generally related to Marginal marine depositional environment. Three major lithofacies were interpreted based on the average porosity value and the volume of clay contained with the presence of upper shoreface, Sand-Silt-Shale intercalation of the lower shoreface and marine shales. A total of 43 Faults (synthetic, antithetic, back-to-back, etc..) and 4 hydrocarbon bearing reservoirs were interpreted. Deterministic velocity model was built which was used for Time-to-Depth Conversion because it gave the least errors after the depth map was back interpolated and depth maps were generated with structures conformable to those on time maps. The result from the petrophysical analysis and property modelling has shown that the reservoirs have porosity values that range from 22-30%, and water saturation ranges from 17-57% for various Reservoir Intervals. X Field Environment of deposition is largely marginal marine deltaic deposits with tidal influence. There is abundance of sand in the environment of deposition which enhanced reservoir connectivity across the field. Trapping configuration is a four-way closure in the shallow reservoirs and fault dependent closure in the deeper reservoirs. The closures are products of rollovers anticlines related to growth faults. Four oil and two gas reservoirs were identified and mapped. Base-case estimated STOIIP vary between 5MMBO and – 90 MMBO. Recommendations were made for deeper prospect to be interpreted.
