Browsing by Author "Adeoye, Taiye, O"

Now showing 1 - 5 of 5
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    Geophysical Investigation of Basement Rock Structures around a proposed Dam Site,
    (Adamawa Stete University, 2017) Raji, Wasiu O; Adeoye, Taiye, O; Ibrahim, K. O.
    A combination of carefully selected geophysical surveys comprising very low frequency electromagnetic (VLF-EM) and electrical resistivity (VES) methods was employed to study the basement rock structures in a proposed dam site within University of Ilorin campus. Data acquired in the survey were processed to inverted subsurface geological model, 2D conductivity structures and geo-electric cross-sections for the area. The results were interpreted to delineate the subsurface rock and structure, the number of geo-electric layers, and to select a suitable area for the construction of dam extension. The four geo-electric layers delineated correspond to lateritic top-soil layer, weathered rock layer, fractured rock layer, and the fresh basement rock. The VLF-EM and resistivity cross-section revealed a series of competent and weak zones. The weak zones are characterized by weathered/fractured rocks, and they correspond to areas of low resistivity anomalies in VES survey and high conductivity anomalies in VLF-EM survey. Competent rock zone corresponds to area of high electrical resistivity anomalies and low conductivities in VLF-EM tomogram. Depth to fresh basement rock in the weak zone ranges from 7.8 – 14.8 m. The competent rock zones correspond to high resistivity anomalies in electrical resistivity cross-section and low conductivity anomalies in VLF-EM tomograms. Depth to fresh basement rock in the competent zone ranges from 3.3 – 6.8 m. the competent zone recommended for the construction of the dam extension.
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    Geophysical mapping of contaminant leachate around a reclaimed open dumpsite.
    (Elsevier, 2017) Raji, Wasiu O; Adeoye, Taiye, O
    Very low frequency electromagnetic (VLF-EM), 2D Electrical Resistivity Profiling (2D ERP) and Vertical Electrical Sounding (VES) methods of geophysics were deployed to map the extent of leachate contamination in near-surface rocks around a popular reclaimed dumpsite in north central Nigeria. Two years after abandon and waste excavation; the dumpsite was converted to a residential area with over 80 houses under construction. Prior to waste dumping operation, clay-seal was installed at 2 m depth around the dumpsite to prevent leachate from the waste material flowing to the adjoining area. Results from VLF, 2D ERP, and VES show presence of leachate contamination in rocks and soil of the reclaimed dumpsite. Leachate has spread laterally up to a distance of about 1 km on the northern and southern parts of the dumpsite centre, and up to a depth of about 20 m. Compared to the results of similar survey in an area outside the dumpsite, leachate infiltration raised the conductivity signature of the rocks around the dumpsite by about 200%: from 7% to 22%. Both VLF-EM and 2D ERP show the presence of approximate north – south oriented structures/fracture characterised by high conductivity. VES results show the presence of four – five geo-electric layers. Important conclusions from the study are that (i) leachate is still present in the rocks and soil of the reclaimed dumpsite two years after the abandonment and excavation of the waste materials, and (ii) the clay seal installed around the dumpsite could not prevent leachate migration to the adjoining areas.
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    Petrophysical Sensitivity of Elastic Modulus and Inverse Quality Factor (1/Q) Analysis in Well Logs,
    (Akamai University Hawaii, USA, 2014) Raji, Wasiu O; Adeoye, Taiye, O
    Theoretical studies and laboratory experiments have shown that seismic attenuation (or inverse quality factor, 1/Q) is sensitive to the presence of fluids, degree of saturation, porosity, fault/fracture, and pressure in porous elastically heterogeneous rocks. However, the probable use of attenuation for reservoir characterization is yet to be tested using well log data. This paper applies the theories of modulus- frequency dispersion to test, theoretically, the sensitivity of P- and S-wave attenuation to the presence of fluids in porous rocks saturated with two or more fluids. Application of the attenuation theory to the analysis of P-wave and S-wave inverse quality factor ( and) in well log data shows that P-wave inverse quality factor is generally higher in hydrocarbon saturated rocks than in brine/water saturated rocks, while the S-wave inverse quality factor does not show direct sensitivity to fluid. A cross plot of the ratio of P-wave and S-wave inverse quality factors, with the ratio of P-wave and S-wave velocities distinguishes gas sand from water sand, and water sand from oil sand. As derived from the analyses, gas sand is characterized by the highest and the lowest ratios; oil sand is characterized by the lowest and the highest ; and water sand is characterized by the and values that plotted between those of the gas and oil sands. The signatures of the bulk modulus, Lame’s first parameter, and compressional modulus show sensitivity to rock fluids. Attenuation analysis in recorded well logs can provide useful guide for hydrocarbon reservoir characterization. (Keywords: Inverse Quality Factor, P-, S- wave, elastic
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    Petrophysical Sensitivity of Elastic Modulus and Inverse Quality Factor (1/Q) Analysis in Well Logs,
    (Akamai University Hawaii, USA, 2014) Raji, Wasiu O; Adeoye, Taiye, O
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    Wavefield Separation For Shear Wave Reflections Enhancement.
    (Federal University of Technology, Minna, Nigeria, 2019) Raji, Wasiu O; Adeoye, Taiye, O; Ibrahim, K. O.; Harris, J. M.
    S-waves in borehole seismic data can provide velocity, attenuation, anisotropy and reflectivity information that are crucial for delineating reservoir geometry and fluid flow structures. Despite the success and other potential benefits of including shear waves in the interpretation of seismic data to discriminate gas related amplitude anomalies from non-hydrocarbon related amplitude anomalies, little efforts have been applied to the development of shear wave technology. S-waves processing is yet to become a routine in borehole geophysics. This paper describes a procedure and some techniques for processing shear waves in a multi-component borehole seismic data– as a precursor for S-wave reflection imaging. The procedure is divided into three key stages, namely: suppression of P-wavefield in the multi-component data; attenuation of non-reflection arrivals in the S-wavefield; and separation of S-S reflection into up-going and down-going components. A set of high resolution crosswell data acquired in a west Texas Oil field, U.S.A is used to test the method. The processed data confirmed the appropriateness of the method presented in this paper. The results yielded separated up-going and down-going S-S reflections that are traceable to the various reflectors depths. Shear wave reflection processing is a key stage in the development of shear wave technology for in oil and gas application.