Facies Analysis of Afenmai Field in Eastern Niger Delta of Nigeria, Using Combined Geophysical Logs, Lithologic and Paleontological Data

Abstract

Facies analysis of Afenmai field was carried out to generate some of the information required for upgrading the status of this old discovery into development stage. This is conventionally performed either by singly correlation lithologic tops, or biozones, or geophysical log motifs. This often results in false reservoir continuity and attendant disappointing results. In this study, sequence stratigraphic principles were employed in an integrated approach to relate the combination of geophysical log data, lithologic and paleontologic information to time-significant lithostratigraphic surfaces. The top of the Agbada Formation and base of E8000 sand were found to be sequence boundaries. The top of E8000 sand is a transgressive surface, while the base of E4000 sand constitutes a maximum flooding surface. The E8000 sand belongs to lowstand systems tract, while the lithofacies sandwiched between the top of E8000 and base of E4000 sands constitute transgressive systems tract. The D-sands together with E1000 to E4000 sands form highstand systems tract. The lithofacies below the base of E8000 sand also belong to the highstand systems tract. Potential stratigraphic traps exist along regional unconformity surface which constitutes the sequence boundary that defines the top of Agbada Formation. Opportunities for infill well drilling were established between wells 6 and 7, as well as between wells 1 and 2.