Seismic Interpretation of Tomboy Field, Offshore Western Niger Delta, Nigeria

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Author(s) S. O. Obaje
Pages 648-660
Volume 2
Issue 9
Date September, 2013
Keywords Seismic Interpretation, Seismic Stratigraphy, Tomboy Field, Surface Boundary
Abstract

The focal aim of the study is to map the structures in the study area using seismic interpretation methodology. Key stratal terminations such as onlaps, toplaps and erosional unconformities (or truncations) were recognised. Nine surface boundaries, namely: four maximum flooding surfaces and five sequence boundaries were detected as peaks and troughs of the seismic onsets, respectively. The maximum flooding surfaces and the sequence boundaries depths were converted to time in milliseconds using check shot data. The converted time represents two-way travel time. Accordingly, the wireline logs were effectively tied to the seismic lines for better stratigraphic interpretation. Biostratigraphic data were used to date the defined surface boundaries and their paleoenvironments of deposition. The structural style of the field is characterised by two systems of antithetic and growth faults. On the seismic lines, shale structures were recognised as zones of chaotic or transparent seismic reflections. The overall geometry of the reflectors is parallel or sub-parallel. On the seismic lines, chaotic reflectors were identified to be associated with small-scale gravity faulting resulting in debris flow. The sandstone-prone facies have greater seismic amplitude values than the shale-dominated units. The seismic expression of such lithology change may have resulted from the juxtaposition of low amplitude and moderately continuous seismic facies (shale-prone) on high-amplitude and variable continuity seismic facies (sand-prone). The identified structural and stratigraphic traps, the reservoir blocks and the depositional environments are useful input to the petroleum system of the area.

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