Electrical resistivity investigation was carried out at Olabisi Onabanjo University campus, Ago-Iwoye, Southwestern Nigeria with the aim of evaluating groundwater potential and aquifer protective capacity of the overburden units in the area. The underlain rocks are predominantly porphyroblastic and banded gneiss, quartzschist and biotite-hornblende granite. Twenty-Four Vertical Electrical Sounding (VES) were probed using Schlumberger array with maximum current electrode spacing (AB/2) of 100 m at each point using the OHMEGA Allied resistivity meter. The data were interpreted using the partial curve matching and computer iteration programme using WINRESIST. Parameters such as overburden thickness, basement resistivity, reflection coefficient and longitudinal conductance were calculated and used for evaluating the groundwater potential and aquifer vulnerability of the study area. The predominant VES curve types obtained are KH, H, A, AKH, HKH and HA. The geoelectric sections show that the area is underlain by 3-5 layers: the topsoil (72.4-1735.6 Ω m), clay/clayey sand/sand/laterite (18.9-1349.5 Ω m), fractured basement (430.7-1021.4 Ω m) and the fresh basement (433.3-7146.4 Ω m). The plotted isopach map showed an overburden thickness range of 4.9-28.2 m with values greater than 20 m at the southeastern and southwestern parts of area. The reflection coefficient range is between 0.62 and 0.98 while protective capacity range is between 0.03 and 0.28. Groundwater potential of the area were classified as high (overburden thickness > 13 m and reflection coefficient < 0.8); medium (overburden thickness > 13 m and reflection coefficient ≥ 0.8); and low (overburden thickness < 13 m and reflection coefficient > 0.8). The protective capacity rating falls between poor to moderate, thus, vulnerable to infiltration of leachate and other surface contaminants. The study therefore helped in identifying favourable groundwater potential and the aquifer vulnerability of the area.

No abstract

This study focuses on the application of 3D static model using 3-D seismic and well log data for proper optimization and development of hydrocarbon potential in KN field of Niger Delta Province. 3D Seismic data were used to generate the input interpreted horizon grids and fault polygons. The horizon which cut across the six wells was used for the analysis and detailed petrophysical analysis was carried out. Structural and property modeling (net to gross, porosity, permeability, water saturation and facies) were distributed stochastically within the constructed 3D grid using Sequential Gaussian Simulation and Sequential Indicator Simulation algorithms. The reservoir structural model show system of different oriented growth faults F1 to F6. Faults 1 and Fault 4 are the major growth faults, dipping towards southwest and are quite extensive. A rollover anticline formed as a result of deformation of the sediments deposited on the downthrown block of fault F1. The other faults (2, 3, 5 and 6) are minor fault (synthetic and antithetic). The trapping mechanism is a fault assisted anticlinal closure. Results from well log analysis and petrophysical models classified sand 9 reservoir as a moderate to good reservoir in terms of facies, with good porosity, permeability, moderate net to gross and low water saturation. The volumetric calculation of modeled sand 9 horizon reveals that the (STOIIP) value at the Downthrown and Ramp segment are 15.7 MMbbl and 3.8 MMbbl respectively. This implies that the mapped horizon indicates hydrocarbon accumulation in economic quantity. This study has also demonstrated the effectiveness of 3-D static modeling technique as a tool for better understanding of spatial distribution of discrete and continuous reservoir properties, hence, has provided a framework for future prediction of reservoir performance and production behavior of sand 9 reservoir. However, more horizontal wells should be drilled to enhance optimization of the reservoir.

The geophysical assessment of groundwater in Awa-Ilaporu, near Ago Iwoye southwestern Nigeria was carried out with the aim of delineating probable areas of high groundwater potential. The area falls within the Crystalline Basement Complex of southwestern Nigeria which is predominantly underlain by banded gneiss, granite gneiss and pegmatite. The geophysical investigation involves the very low frequency electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) methods. The VLF-EM survey was at 10 m interval along eight traverses ranging between 290 and 700 m in length using ABEM WADI VLF-EM unit. The VLF-EM survey was used to delineate areas with conductive/fractured zones. Twenty-three VES surveys were carried out with the use of Campus Ohmega resistivity meter at different location and at locations areas delineated as high conductive areas by VLF-EM survey. The result of VLF-EM survey along its traverse was used in delineating high conductive/fractured zones, it is, however, in agreement with the delineation of the VES survey. The VES results showed 3-4 geoelectric layers inferred as sandy topsoil, sandy clay, clayey and fractured/fresh basement. The combination of these two methods, therefore, helped in resolving the prospecting location for the groundwater yield in the study area.

No abstract