An integrated approach to evaluate reservoir continuity and pressure communication between Nuke JF7 and Otam EF8 reservoirs

Abstract

A major uncertainty exists as regards reservoir continuity across Otam EF8 and Nuke JF7 reservoirs and whether pressure depletion in one reservoir would result in reserve loss in the other if these reservoirs were exploited independently. Reservoir characterization was used to resolve this challenge utilizing a dataset of 3D seismic data, well-log data, biostratigraphic data, fluid composition data, pressure data, and production data via an integrated study. Seismic interpretation was used to characterize the structural and stratigraphic framework of the Niger Delta reservoirs of interest. Fault seal analysis, grain size analysis, fluid composition, and dynamic data analysis were supportive in making inferences on reservoir continuity and pressure communication. Otam EF8 reservoir was identified as a thick, clean sand zone as opposed to the Nuke JF7 reservoir with shaly sand intercalations, which revealed that the EF8 reservoir does not extend to the JF7 reservoir. The permeability and pressure analysis highly suggest communication with its juxtaposing reservoir. The thickness–throw ratio and manual computation of the shale gouge ratio also indicate the potential for fluid communication across the fault. It was established from coupled material balance analysis that these two reservoirs may be in pressure communication, as a relatively good history match was obtained. The study has shown that reservoir continuity and pressure communication across two proximal reservoirs may be mutually exclusive.