Global Journal of Geological Sciences

Petroleum system elements analysis of sediment outcrops in the edda area of the Afikpo sub-basin

Celestine N. Nwojiji — 2026-08-19

This study analyzed the petroleum system elements of sediment outcrops deposited within the Edda area in the Afikpo Sub-basin. The area comprises the Nkporo Group and the Coal measures Group (Mamu, Ajali, and Nsukka Formations) in the Southern Nigeria sedimentary basin. The deposits are characterized by a range of lithological units, including shales, sandstones, siltstones, heterolithic units, and coal seams. This work aims to integrate lithostratigraphic, structural, and sedimentological parameters to understand the petroleum prospectivity and unlocks hydrocarbon opportunities within the Afikpo Sub-basin. The methods used in this study includes detailed field/outcrop descriptions, sedimentological and structural analyses. Over ten outcrops were studied and sampled for this study. The field investigations identified thick, organic-rich strata belonging to the Nkporo and coal measure Groups as potential source rocks. The medium- to coarse-grained, well-sorted Afikpo, Owutu and Ajali sandstones, with high porosity and bioturbation, are viable reservoir rocks. At the same time, the interbeds shales and indurated/iron rich siltstones were identified aseffective seals. Hydrocarbon traps identified in the area include: fault, anticlinal folds, and ferruginized indurated siltstones interbedded within the larger sandstone deposits. The depositional environment ranges from deltaic/tidal to shallow marine. The sedimentary sequences present in the study indicate suitable conditions for hydrocarbon generation, migration, and preservation. The vertical stacking of lithostratigraphic units observed in the study area indicates favourable conditions for efficient hydrocarbon production planning and development.

Comparative study of aquifer systems in parts of the basement complex and coastal plain sands of southeastern Nigeria using geophysical techniques and geochemical parameters

Rita A. Archibong — 2026-08-19

This study presents the robust, multi-parameter comparative evaluation of the geophysical and geochemical characteristics of two distinct geological formations in Southeastern Nigeria. The fractured crystalline basement of the Southern Oban Massif (Awi Community) and the porous sedimentary media of the Nigeria Delta Basin (Calabar Municipal). Twenty (20) vertical electrical sounding (VES) points under Schlumberger array, and sixteen (16) groundwater samples were analyzed for the modeling of the groundwater potential, water quality and access irrigation suitability. The geoelectrical modeling delineates high yield, porous aquifers within the sedimentary gravel/sand units in Calabar at depths between 19 and 42.9 m, in contrasts with structurally controlled, weathered to fractured regolith units in Awi. The geochemical analysis of the two formation depicts a host freshwater (TDS ˂ 500 mg/l). Aquifers of both formations suffer from severe geogenic iron contamination up to 5.18mg/l and widespread anthropogenic nitrate loading exceeding the 50mg/l standard. The evaluated water quality through the weight arithmetic water quality index (WQI) yielded values consistently exceeding 300, classifying the untreated groundwater across both formations as unsuitable for direct consumption. Irrigation indices calculated for water samples from both formations presented a critical divergence; low sodium adsorption ratio (SAR) values suggested chemical safety, whereas highly elevated magnesium adsorption ratio (MAR) scores of up to 76.4 % posed a severe long-term risk of soil alkalization and structural degradation. Gibbs and Piper diagram visualization confirmed a transitional lifecycle in Calabar from precipitation-dominated to rock-water interaction-dominated facies, while Awi basement remains tightly cluster within the precipitation- dominated facies regime. Both aquifer systems are characterized by a highly mineralized Ca-Mg-Cl-SO water type, highlighting permanent hardness.

Palynostratigraphy and paleoenvironmental interpretation of late Eocene–early Oligocene sediments in the umuchu -1 well, greater Ughelli Depobelt Niger delta basin

Celestine Nwite Nwojiji — 2026-09-18

The Eocene–Oligocene interval of the Niger Delta Basin remains relatively poorly constrained biostratigraphically relative to the extensively documented Miocene section, and published palynostratigraphic control for this interval is especially sparse in the Greater Ugheli depobelt. This study aims to establish a palynostratigraphic framework for the Late Eocene–Early Oligocene interval of the Umuchu-1 well, in the Greater Ugheli depobelt of the Niger Delta Basin; determine the age of the studied sediments using the established Niger Delta P-zone biozonation; and reconstruct the depositional environments recorded in the well from ecologically diagnostic palynomorph groups. Twenty-four ditch-cutting samples spanning 3240–6535 ft were processed using standard palynological preparation procedures (sequential HCl/HF acid digestion, oxidation, heavy liquid separation, and sieving), mounted on slides, and examined by transmitted-light microscopy. Biozonation followed the informal P-zone scheme of Shell Petroleum Development Company (SPDC) and calibrated against other published low latitude zonation, while paleoenvironmental interpretation used the relative abundance of mangrove, freshwater swamp/forest, savanna, and marine (organic-walled microplankton) palynomorph groups. The interval was subdivided into three subzones P520, P480, and P470 all falling within the Magnastriatites howardi–Verrucatosporites usmensis Low latitude Zone and indicating a Late Eocene to Early Oligocene/Late Eocene age. Paleoenvironmental interpretation revealed a vertically alternating succession of backshore mangrove swamp, backshore freshwater swamp, and a single lower shoreface episode (4790–5090 ft). These alternations record repeated shifts in relative sea level and delta-front position during active progradation of the Late Eocene–Early Oligocene sediments Niger Delta, refine the regional palynostratigraphic framework for an underrepresented stratigraphic interval and depobelt, and offer a basis for well-to-well correlation. The integrated palynostratigraphic and paleoenvironmental framework established here carries direct implications for sequence stratigraphic interpretation, reservoir- and source-rock-facies prediction, and hydrocarbon exploration risk reduction in the underexplored deeper Paleogene section of the basin.

Ground radiometric survey using gamma-ray spectrometer: a case study of Akwa Obio Inwang, Akpabuyo l. G. A., cross river state, Nigeria.

Azogor , W. E. — 2026-10-09

Ground radiometric survey of the concentration of the primordial radioisotope elements (²³⁸U, ²³²Th and ⁴⁰K) was conducted in the soils of Akwa Obio Inwang Community, Cross River State, Nigeria. These investigations, which were aimed at determining the concentration of radioelements and their spatial distribution in the soil within the area, were performed using a portable gamma-ray spectrometer (Pico Envirotec GRS-2 portable spectrometer (PGIS-SP) with a 0.347 l crystal pack). Results shows that the minimum and maximum concentrations of ²³⁸U, ²³²Th and ⁴⁰K were 0.19 and 9.40 ppm, 0.05 and 21.53 ppm, and 0.05 to 0.96 % respectively. The concentration of ²³⁸U, and ²³²Th in the soil were ∼2 times higher than the expected value in normal sedimentary rocks. The elemental ratios were also higher in the area with maximum value of eU/eTh and eU/K of 4.41 and 118.20. Equivalent minimum values are 0.01 and 0.44 respectively. These results show that the natural background uranium and thorium mineralization in the soils are comparatively higher than in normal soils. However, the radioelements concentration in the area is still safe for human occupation since the average absorbed gamma dose rate at 1 m above the ground is 79.29 nGyh^-1. The energy (gamma-ray) of ⁴⁰K is 1.46 MeV, that of ²¹⁴Bi is 1.76 MeV, and ²⁰⁸Tl have energy of 2.62 MeV. These energies constitute the peaks in gamma-ray spectrum However, the area should be freed from nuclear contaminants since such can increase the radioelement concentration of the soils and therefore render the area harmful to human occupation