Delineation of Subsurface Structures in Toja Field in the Niger Delta Using Well-Logs and Seismic Data

Abstract

The subsurface structures delineation of TOJA Field southwest Niger Delta using well-log and seismic data is here presented. The reflectivity seismic amplitude and acoustic impedance, spectra decomposition volume derivatives were used for reservoir delineation. Seismic data and well logs have been integrated through seismic inversion as part of the techniques deployed in the delineation of subsurface structures in the Niger Delta basin. Well logs were tied to seismic data using four wells from four fields in the Niger Delta. Reflectivity seismic data was inverted to generate a 3D distribution of P-impedance in the fields of interest. Fluid and lithology sensitivity analysis including cross-plotting, forward seismic modelling and Gassmann fluid substitution was performed to delineate various subsurface structures. The TOJA prospect is a footwallclosure located behind the main bounding fault, north of the TOJA Field. The Field's structure is a faultdependent footwall closure with a dip component in the shallow levels. The structure is bounded by three faults; a large east-west fault forms the boundary between the TOJA Field to the South and the TOJA North Field. This fault is relayed by a minor fault that delimits the southwestern end of the accumulation. A northeastsouthwest bounding fault separates the TOJA structure from the SATRA accumulations to the east and has a throw of between 200 and 400 ft. The results of this study can lead to a more cost-effective method for defining the Field Development Plan (FDP), through the use of seismically constrained reservoir information that would provide better well placement to achieve improved production.