부산대학교 도서관

Well log and core data were used to carry out detailed facies, sequence stratigraphic, and petrophysical analyses of the "Iota field" in the onshore Niger Delta Basin. The aim was to recognize facies distribution, environments of deposition, stratigraphic framework, reservoir continuity, and property distribution for better understanding of reservoir characteristics across the field. Sedimentological evidence reveals the occurrence of fifteen lithofacies, which were further classified into eight facies associations. The facies associations depict deposition in the offshore, offshore transition, lower shoreface, upper shoreface, estuarine channel, tidal channel, and fluvial channel environments. Sequence stratigraphic analysis reveals the occurrence of three maximum flooding surfaces and three sequence boundaries, which reflect series of transgressive and regressive episodes during the Serravallian-Tortonian age. Two depositional sequences comprising lowstand system tract, transgressive system tract, and highstand system tract packages were recognized. The sand and shale of the fluvial, tidal, estuarine, shoreface and offshore deposits, constitute the reservoir and seal/source rock packages. Correlation indicates that the reservoir packages have good lateral continuity, except where channel incision has occurred. Petrophysical analysis shows that the reservoir units have fair-to-good porosity and good- to-excellent net-to-gross qualities. Dominance of oil-bearing zones were detected at shallow to deeper interval at the northern section of the study area, with few gas-bearing intervals occurring at the intermediate intervals of the southern section. Overall, integrated analytical approach has provided more insight into the facies and reservoir quality distribution, thus reducing subsurface reservoir uncertainties. [ABSTRACT FROM AUTHOR]