A. OGBAMIKHUMI

This study presents an in-depth structural analysis of the Ugbobo area and its environs, situated within the Igarra Basement Complex in southwestern Nigeria. The primary objective of this research is to shed light on the geological events that have shaped this region, providing valuable insights into its deformational and geological history. To achieve this goal, Landsat imagery was utilized to systematically gather and examine fracture data through various analytical techniques. These techniques include rose plots, stereonets, and pole plots, which enabled the assessment of structural orientations and deformations in the study area. The results obtained from the rose plot analysis revealed a dominant NNE-SSW fracture trend, indicating deformation that can be attributed to the pre-Pan African orogeny. This finding suggests a polyphase deformational history, pointing to significant tectonic activity in the region. Furthermore, the analysis of pole plots showed clustering of poles in the western and eastern directions. The stereonet analysis revealed that the fracture lines are concentrated towards the eastern and western quadrants, indicating that many of these planes are dipping steeply in those directions. The comprehensive understanding of these structural patterns is crucial for reconstructing the deformational and geological history of the terrain. This study contributes significantly to the existing knowledge of the Igarra Basement Complex, providing new insights into the region's tectonic evolution. The findings of this research have important implications for future geological investigations and exploration activities in the area.

The petrographic and mineralogical analysis of siliciclastic and carbonate facies within the southeastern Dahomey Basin, Nigeria, was studied with the aim of interpreting their provenance, depositional environment, diagenetic evolution, and reservoir potential. Thirty three samples were collected and analyzed. Analysis involved X-ray diffraction (XRD) for mineralogical characterization and thin-section petrography for micro-structural and textural evaluation. Six representative samples were analyzed, comprising three siliciclastic units from depths of 1610– 1870 ft and three carbonate units from 730–930 ft across two wells within the study area. The siliciclastic samples are dominated by quartz, feldspar (orthoclase and albite), and muscovite, indicating derivation from granitic and gneissic sources of the Precambrian Basement Complex. Moderate textural maturity and the presence of albitized feldspars suggest limited reworking and shallow burial diagenesis. The carbonate samples, composed mainly of bioclastic and peloidal packstones to wackestones, reflect shallow-marine to outer shelf depositional settings, influenced by mixed carbonate–siliciclastic sedimentation during transgressive phases. Diagenetic features such as sparry calcite cementation, muscovite preservation, and feldspar albitization point to a multi-stage, low-thermal diagenetic history under closed-system conditions. High quartz content, low clay development, and early marine cementation collectively indicate moderate to good reservoir quality, with porosity largely preserved by mechanical rather than chemical processes. The results of petrography and mineralogy of Siliciclastics and Carbonate facies in Southeastern Dahomey Basin revealed that the units are potential for hydrocarbon-bearing reservoirs.

An integrated approach using seismic information was employed for subsurface mapping of SULU reservoir of the Niger Delta basin. The aim of this study was directed towards the generation of a subsurface map, determination of the subsurface structural features for hydrocarbon and prediction of prospecting of the reservoir. The methods employed include analysis of 3D seismic data using Petrel software: faults and horizon deductions from the seismic section were used to generate structural maps which revealed different structural styles present in the studied area and extraction of amplitude. A distinct horizon was mapped. From the horizon nine faults (with five been major) were mapped for the purpose of carrying 3D subsurface structural interpretation. These were used in generating the time structure maps using the Petrel Interpretational tool. The results show that the trapping mechanisms in the field are favourable for hydrocarbon accumulation. Two principal structural trapping mechanisms presents are the rollover anticline and the simple anticline. This study has demonstrated and appreciate the importance of seismic structural interpretation in generation of subsurface maps of reservoir, understanding the structural styles present, amplitude extraction for
prospect ranking.