Focused reservoir characterization: analysis of selected sand units using well log and 3-D seismic data in 'Kukih' field, Onshore Niger Delta, Nigeria.

This study focuses on the comprehensive reservoir characterization of the 'Kukih' Field within the onshore northeastern Niger Delta region, Nigeria. The absence of its detailed description with delineated reservoir properties, lateral continuity, and their use to identify potential reservoir quality and heterogeneity necessitated this study. Integrating well log and 3D seismic data, the investigation aims to elucidate reservoir properties, lithofacies, and depositional environments to unravel hydrocarbon potential. The geological setting, encompassing the Agbada Formation of Early and Middle Miocene age, is scrutinized through detailed geologic analysis. Petrophysical evaluation of four well logs (Kukih-1, Kukih-2, Kukih-3, and Kukih-4) facilitated the determination of key parameters such as shale volume, effective porosity, and water saturation. Seismic interpretation further enriched the structural characterization of the field. Results showcase three predominant reservoir sands (A, B, and C) with distinct lithofacies and thickness variations. Effective porosity ranges from Fair to Excellent, with permeability exhibiting high values for hydrocarbon reservoir potential. Water saturation trends, lithofacies distributions, and structural features were illuminated through iso-parametric maps and seismic analyses. Depositional environments were inferred through facies analysis, revealing the presence of funnel-, cylinder-, and bell-shaped successions that hint at intricate marine sedimentary processes. Challenges owing to limited core data were acknowledged, and the integration of methodologies emerged as a pivotal strategy for enhanced reservoir understanding. This study underscores the 'Kukih' Field's hydrocarbon potential, accentuating the significance of multidisciplinary approaches in deciphering complex reservoir systems. In light of the petrophysical analysis derived from the well logs and the identification of structural highs through the structural maps, this study recommends the drilling of unexplored zones exhibiting promising structural characteristics.

A review of the occurrence, distribution, and impact of bitumen seeps on soil and groundwater in parts of southwestern Nigeria.

The impact of bitumen components on soil and groundwater resources is of environmental importance. Contaminants' influx into the environment from bitumen components through anthropogenic activities such as exploration, mining, transportation, and usage of bitumen in all its forms have been reported globally. However, gaps exist in the geogenic occurrence of bitumen in the shallow subsurface such as in southwest Nigeria, contaminating the soil and groundwater resources. This review presents in situ bitumen seeps as a source of geogenic soil and groundwater contaminants in southwestern Nigeria. We conducted a systematic review of literatures based on defined selection criteria. We derived information on the state of knowledge about bitumen seep occurrences and distribution in southwestern Nigeria. Also, the processes that exacerbate bitumen contaminants' influx into soil and groundwater were enunciated. At the same time, case examples highlighted areas for possible in situ bitumen contamination studies in Nigeria. The results of this review showed that a multidisciplinary approach has been employed to assess and monitor the contaminants resulting from the various activities involving the exploitation and application of bitumen in Nigeria. These studies emphasize bitumen contaminants as emanating from anthropogenic sources. The results also suggested that bitumen studies have been mainly exploratory to improve the understanding of the economic potential of the hydrocarbon reserve. Also, recent advances in bitumen contaminants studies accounted for the heterogeneous nature of the bitumen. This allows for the optimized categorization of the mechanism and processes undergone by the different bitumen components when released as environmental contaminants. However, a knowledge gap exists in characterizing and understanding the effects of in situ bitumen seeps as a geogenic source of soil and groundwater contamination. This review identifies the possibility of geogenic soil and groundwater contamination by in situ bitumen seeps in the coastal plain sand of the Dahomey basin in southwestern Nigeria. The impact of the bitumen contaminants on the environment was discussed, while methods for accessing the occurrence and distribution of the bitumen contaminants were highlighted.

Geoelectrical assessment of polluted zone by sewage effluent in University of Ibadan campus southwestern Nigeria.

Sewage effluent was discharged through leaking sewer into the agricultural training farms, University of Ibadan which is used for cultivation of vegetables and cereals, thus constituting threat to human health. This study examined the reliability of the electrical resistivity technique in delineating sewage polluted zones and possible pathways into the groundwater network. The area investigated is underlain by banded gneisses. Ten resistivity Wenner-imaging lines (N-S) were established and inverted section generated using RES2DINV. Thirty VES stations were occupied using Schlumberger array, the current electrode spacing (AB/2) expanded from 1 to 75 m and data analysed using WinResist. 2-D inverted section depicted the top soil and clay unit. Resistivity in the top soil (36-70 Ω-m) showed a decrease of 57 to 78% while the clayey unit (6-18 Ω-m) showed a reduction of 63 to 88% relative to the control units. Plunge in resistivity within the top soil and clay units suggests the presence of pollutants. VES-derived geoelectric section recorded three varying sequences, with a fall in resistivity in the top soil (22-58 Ω-m) and the clay unit (6-15 Ω-m) compared with the reference layers having 233 and 34 Ω-m, respectively; the fractured sections in some parts of the bedrock could serve as a conduit for the seepage of the pollutants into the groundwater system. Drop in resistivity suggests the presence of pollutants within the top soil and clay units. These techniques have helped in mapping out unnatural zones around the farm.