Browsing by Author "Raji, Wasi O"

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    ) Evaluation of groundwater aquifer vulnerability in Ilorin Metropolis Using Electrical Resistivity Method of Geophysics
    (European Water resources Associiation, 2019) Raji, Wasi O; Abdulkadir, Kamil, A; Rahman, Rasak, A
    An area of 321.97 km2 in Ilorin Metropolis has been studied, using 312 Vertical Electrical Sounding data obtained in an intensive Electrical Resistivity Survey. The goal of the study is to evaluate the vulnerability of groundwater in the area to contamination with a view to advise Kwara State Government on the safe sites for locating the planned public water project in the different parts of Ilorin. VES data acquired in the area were subjected to manual and computer-aided interpretations to delineate the different geo-electric layers, their hydrogeological significance, and vulnerability of the aquifer. The area was divided into zones, namely, A, B and C. Results of the study revealed presence of five geo-electric layers and two groundwater aquifer layers. The first aquifer corresponds to weathered rock layer, has hydraulic conductivity ranging from 0.1 and 3.0 m/day, lies at shallow depths ranging between 2 and 36 m, and has overburden material whose protective capacity (𝑠) against groundwater contamination is weak (𝑠≤0.19), except in few places in zone C where protective capacity is moderate (0.2≤𝑠≤0.69). The second aquifer layer corresponds to fractured basement rock, lies at depths ranging between 5.0 and 53 m, has overburden layer whose protective capacity against groundwater contamination ranges from moderate (0.2≤𝑠≤0.69) to good (0.7≤𝑠≤4.9). Groundwater in fractured basement rock aquifers is more protected against contamination from dumpsite leachates and anthropogenic wastes than the groundwater in the weathered rock aquifers. Joint interpretation of hydro-dynamic properties of the overburden and aquifer layers of the three zones showed that zone C has the highest groundwater protection capacity, while zone A has the least protection capacity against contamination. Different safe spots were identified for citing boreholes for potable water supply in the three zones. The study recommended that all boreholes for portable water supply, except in few places in zone C, should penetrate the fractured basement rock aquifers to avoid the supply of contaminated groundwater in the future.
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    Petrophysical Analysis of Seismic Energy Attenuation In Reservoir Rocks
    (Faculty of pure and applied Science, Ladoke Akintola University of Science and Technology, LAUTECH, Ogbomosho, 2015) Raji, Wasi O
    The phenomenon controlling the mechanism of intrinsic seismic attenuation, 𝑄!"# !! in waves travelling in earth media is still poorly understood. To give insight to the mechanism – it’s cause and effect, this paper used wave induced fluid flow in partially saturated porous rock as the candidate mechanism responsible for intrinsic attenuation (or absorption) in waves propagating in earth media. Using a hydrocarbon reservoir model containing fully water saturated patches surrounded by partially gas–saturated matrix, changes in compressional rock modulus is estimated at high and low frequency bands as a function of saturation at known irreducible water saturation. The study shows that (i) intrinsic attenuation is saturation dependent, (ii) fluid heterogeneity is a necessary condition for intrinsic attenuation, and (iii) intrinsic attenuation estimated at 0.4 irreducible water saturation (0.6 gas saturation) is higher than the intrinsic attenuation at 0.8 irreducible water saturation (0.2 gas saturation). Numerical wave simulations show that the rock-physics-based estimated attenuation is capable of causing amplitude reduction, waveform distortion, and prolonged travel time in seismic waves traveling from a source to the receiver. Overall, the study links rock physics explanations for seismic attenuation to the waveform distortion and energy depletion commonly observed in exploration scale seismic data. The learning from this study provides insights into seismic amplitude anomaly commonly observed in seismic images of fluid-saturated units.