Research Article 3-D Seismic Attribute Analysis for Enhanced Prospect Definition of "Opu Field'', Coastal Swamp Depobelt Niger Delta, Nigeria

Abstract

Background and Objective: Analysis of seismic attributes has been an integral part of reflection seismic interpretation for over two decades now. Seismic attributes facilitates structural and stratigraphic interpretation as well as offer hints to formation type and fluid content estimation with the potential benefit of detailed reservoir characterization. The current study evaluated the use of seismic attributes generated from 3D seismic and well log data for characterization of the reservoirs of ʻʼOpu Fieldʼʼ, Coastal Swamp Depobelt, Niger Delta. Materials and Methods: Root mean square (RMS) amplitude, instantaneous frequency and interval average maps were extracted on seismic events with pronounced bright and dim spots. These maps were used to establish the diagnostic ability of 3D seismic attribute analysis in enhancing seismic interpretation and volumetric estimation of the mid Miocene to Pliocene Agbada Formation reservoirs within the Coastal Swamp Depobelt, Niger Delta basin. The methodology involved a well-defined procedure which included the delineation of the various lithologies from the gamma ray log, identification of reservoirs from the resistivity log, regional well correlation, determination of petrophysical parameters, horizon and fault mapping, time to depth conversion, attribute analysis and reserve estimation. Results: Two main reservoirs identified as Sand-A and Sand-B were mapped in the study area using seismic data. Similarly, seven faults labelled F1-F7 and four horizons were mapped within the field. Depth structure maps generated revealed a massive Northeast-Southwest (NE-SW) trending anticlinal structure. Petrophysical analysis revealed a mean porosity value of 18% while the mean permeability values ranged from 63-540 md across the two reservoirs. Water saturation and volume of shale (Vsh) across the reservoirs ranged from 38-90 and 17-82%, respectively. Conclusion: This study revealed that the“Opu Field” has high hydrocarbon potentials and excellent petrophysical characteristics favourable for hydrocarbon accumulation and production. The benefits of integrating structural interpretation, petrophysical evaluation and seismic attributes analysis in prospect identification and reservoir prediction was therefore highlighted in this study.