Depositional Environment and Sequences of SAP-22 and SAP-23 Wells, Greater Ugheli Depobelt, Niger Delta: Insights from Gamma-Ray Log and Core Photographs
Osazuwa Abifade Ogbahon *
Department of Applied Geology, Federal University of Technology, Akure, Ondo State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
This study investigates the depositional environments and sequence stratigraphy of the SAP-22 and SAP-23 wells in the Niger Delta to enhance reservoir characterization and hydrocarbon exploration. Gamma-ray logs were interpreted and converted into lithological profiles using Petrel software. Lithological data were integrated with core log photographs to identify lithofacies and sedimentary structures. The stratigraphic succession is dominated by thick sandstone intervals interbedded with thin shale layers (5–20 ft) in the upper sections, grading downward into alternating sandstone–shale units typical of the Agbada Formation. Interpretation of gamma-ray motifs (bell, cylindrical, funnel, bow, and serrated) in conjunction with lithofacies—planar cross-stratified sandstone (Sp), horizontally stratified sandstone (Sh), heterolithic facies (H-sf), and laminated shale (Fl)–reveals deposition across fluvial, distributary channel, delta front, shoreface, tidal flat, and storm-influenced shelf environments while sedimentary structures indicate predominantly tractional depositional processes. Sequence stratigraphic analysis identifies three depositional sequences, each comprising lowstand, transgressive, and highstand systems tracts. Five sequence boundaries and three maximum flooding surfaces were recognized and correlated between the wells. These results provide a refined stratigraphic framework and improve understanding of reservoir architecture, heterogeneity, and hydrocarbon potential in the Niger Delta Basin.
Keywords: Depositional environment, Niger Delta, gamma-ray log, lithofacies, core photographs.