Abstract
Hydrocarbon exploration analysis from a seismic stratigraphic approach was carried out within the Beta Field, Coastal Swamp Depobelt, Niger Delta, to identify system tracts and sequence boundaries that could be associated with potential hydrocarbon accumulation. 3D seismic volume and data from four wells were analyzed. Depositional sequences, system tracts, sequence boundaries, and candidate maximum flooding surfaces were picked from logs, while reflection patterns and terminations were interpreted from seismic sections. Log shapes from gamma rays in combination with seismic facies analysis were interpreted in order to delineate lithology, depositional environments and depositional sequences. Seismic attributes were extracted and were draped on gridded surfaces from the interpreted seismic horizons. These were integrated with structure maps to obtain structural and stratigraphic trends, and the possible presence of reservoir sand. Five depositional sequences and nine seismic facies were identified within the field. The depositional sequences were designated Sequences S1 to S5 based on the depth of the occurrences and stacking patterns. This study reveals a progression from fluvial depositional settings to the shelf. The main reservoirs identified are the sand units of the highstand and lowstand within three depositional sequences (S1, S4 and S5) although interbedded sands within the TST of S4 and S5 are also suspected of being potential reservoirs. The channel sand deposits within the study area are suspected to be hydrocarbon bearing as they occurred within the complex fault trapping system popular in the Niger Delta. The application of seismic stratigraphy, as shown in this study, serves to encourage exploration in the Niger Delta where it could be effectively employed for reducing risk in hydrocarbon exploration.
Highlights
Seismic stratigraphy uses seismic reflection patterns to identify depositional sequences to predict the lithology of seismic facies by interpreting depositional processes and environmental settings, and to analyze relative changes in sea level as recorded in the stratigraphic records
The sand units of the highstand system tracts (HST) and lowstand system tract (LST) within sequences 1, 4 and 5 (S1, sequence 4 (S4) and sequence 5 (S5)) are the main reservoirs identified within the field (Fig. 21)
The present study shows that the Beta Field is divisible into five depositional sequences, separated by unconformities and their correlative conformities
Summary
Seismic stratigraphy uses seismic reflection patterns to identify depositional sequences to predict the lithology of seismic facies by interpreting depositional processes and environmental settings, and to analyze relative changes in sea level as recorded in the stratigraphic records. Galloway 1975, Brown & Fisher 1977, Mitchum et al 1977, Payton 1977, Armentrout & Perkins 1991, Miall 1991, Posamentier & George 1994, Galloway 1998, Davies et al 2004, Catuneanu 2006) These studies have shown that seismic stratigraphic principles can help to improve seismic interpretations. As exploration continues to move into frontier regions and into deeper parts of sedimentary basins where well control is limited or lacking, fundamental to delineating drilling targets is interpreting stratigraphy, sedimentary facies, and geologic history from seismic reflection data (Galloway 1976, Cross & Lessenger 1988, Paumard et al 2019, Cawthra et al 2020)
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