Abel Olayinka - Academia.edu (original) (raw)
Papers by Abel Olayinka
Hydrogeology Journal, 2008
Page 1. Fuzzy logic modeling of the resistivity parameter and topography features for aquifer ass... more Page 1. Fuzzy logic modeling of the resistivity parameter and topography features for aquifer assessment in hydrogeological investigation of a crystalline basement complex MA Adabanija & EO Omidiora & AI Olayinka Abstract ...
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Olayinka, A.I. and Yaramanci, U., 2002. Smooth and sharp-boundary inversion of two-dimensional ps... more Olayinka, A.I. and Yaramanci, U., 2002. Smooth and sharp-boundary inversion of two-dimensional pseudosection data in presence of a decrease in resistivity with depth. European Journal of Environmental and Engineering Geophysics, 7: 139-165. The smooth and sharp-boundary inversion of two-dimensional (2D) apparent resistivity pseudosection data in cases where the half-space has a lower resistivity than the overburden is investigated. The study entailed calculation (by forward modelling) of the synthetic data over simple 2D geologic models and inversion of the data. The 2D structures modelled include vertical fault, graben and horst. The Wenner array was used. The results show that there is generally an improvement in the model misfit with iteration number in smooth inversion; the algorithm can then be expected to iterate to the best solution at a high iteration number where the model resistivity of the substratum approaches the true bedrock resistivity. Inversion of the data using sha...
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Journal of Applied Sciences, 2011
Leachate-effluent from refuse dump site is an important source of groundwater pollution. Conseque... more Leachate-effluent from refuse dump site is an important source of groundwater pollution. Consequently, assessing the impact of leachate is an active area of groundwater research. Geoelectrical imaging was carried out at an abandoned waste dump site in Ibadan, southwestern Nigeria, with the aim of determining how accurately electrical measurements could delineate the influx of leachate into groundwater and surface water. Eight electrical-resistivity profiles were measured. Four of the traverses were conducted on the dump site whereas two traverses were measured towards the lower side to assess possible ingress of the leachate. The other two lines were measured about 300 m from the site to serve as control. Elevation data were collected using Global Positioning System. The resistivity data were inverted using the least-square technique. The inversion delineated regions of low resistivity (<20 Ωm) believed to be leachate derived from decomposed waste. Non-degraded refuse occurred as isolated regions of higher resistivity (>20 Ωm). The highest resistivity regions (>100 Ωm) were interpreted as regolith derived from chemical weathering of the crystalline bedrock. Resistivity-derived thickness of the leachate zone was consistent with the thickness derived from the elevation data. It could be inferred that there was high concentration of leachate towards the lower elevation hence the adjoining stream is prone to pollution. This study showed that 2D imaging can be effective in imaging pollution plumes around refuse dump sites. The method can be useful to assess opportunity for remediation measures in situations where the leachate has reached the groundwater system.
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Journal of Petroleum Exploration and Production Technology
One of the complexities of geomechanical study is in the classification of rock’s properties and ... more One of the complexities of geomechanical study is in the classification of rock’s properties and overpressured intervals—a knowledge which is not only essential for well safety and cost-effective drilling, but crucial in evaluating exploration risk factors and ensuring a successful hydraulic fracturing program. In this study, a more robust prediction of reservoir pressure regime is presented, where the geomechanical distributions of the rock give a distinct correlation. Three wells from the Niger Delta Basin were studied using empirical equations to estimate the elastic properties, wave velocities and the rock physics parameters for each well. From the results obtained, the velocities of compressional wave (Vp) and shear wave (Vs) decrease as porosity increases. Also, a linear correlation exists between Poisson’s ratio and Vp/Vs, where both variables showed distinct behavior and similar trend serving as useful tools for lithology identification. Another significant observation is th...
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Petroleum
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Geomechanics and Geophysics for Geo-Energy and Geo-Resources
A pre-existing plane of weakness along the fault is comprised of a particular pattern of joints d... more A pre-existing plane of weakness along the fault is comprised of a particular pattern of joints dipping at different orientations. The fault stress state, partially defined by the orientation of fault, determines the potential of slip failure and hence the evolution of fault permeability. Here the influence of fault orientation on permeability evolution was investigated by direct fluid injection inside fault with three different sets of fault orientations (45°, 60° and 110°), through the coupled hydromechanical (H-M) model TOUGHREACT-FLAC3D. The influence of joints pattern on slip tendency and magnitude of potential induced seismicity was also evaluated by comparing the resulted slip distance and timing. The simulation results revealed that decreasing the dip angle of the fault increases the corresponding slip tendency in the normal fault circumstance. Also, with changing joints dip angle associated with the fault, the tendency of the fault slip changes concurrently with the permeab...
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Geology, Geophysics and Environment
The high global numbers of road accidents due to bad roads and the failure of other engineering s... more The high global numbers of road accidents due to bad roads and the failure of other engineering structures have necessitated this study, particularly as road transport accounts for a higher percentage of cargo movement in African countries. The geophysical investigation was carried out on six failed and two stable sections along the Ibadan-Iwo-Osogbo highway to examine the geological factors responsible for highway failure in the area. A Landsat ETM+ (Enhanced Thematic Mapper Plus) imagery of the study area and its environs was acquired and processed for lineaments analyses. Magnetic, Very Low Frequency Electromagnetic (VLF-EM) and electrical resistivity methods involving Schlumberger Vertical Electrical Sounding (VES) and 2-D imaging using a dipole- dipole array were utilized. Lineaments were identified across failed localities. Lateral magnetic variations in the near-surface geological materials characterized the study area. The 2-D VLF-EM models generated showed conductive zones ...
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Rudarsko-geološko-naftni zbornik
Engineering geological investigation of some unstable and stable sections of the Ibadan-Iwo-Osogb... more Engineering geological investigation of some unstable and stable sections of the Ibadan-Iwo-Osogbo highway was undertaken to unravel the intrinsic reasons responsible for continuous pavement failure along this road. Eighty disturbed and forty undisturbed soil samples were collected at different depths from twenty test pits of six selected failed sections (FS) and two stable sections (SS). Road construction analysis was done on these soil samples using standard methods. Liquid limit (22 - 64% and 32 - 40%), plasticity index (13 - 41% and 12 - 18%) and percentage fines (47 - 59% and 32 - 41%) indicated fair to poor and fair to good subgrade materials of FS and SS respectively. Medium to high plasticity and high clay content of soils of FS are indicative that the soils possess medium to high swelling potential. The activity of clay in soils of FS was approximately 0.3 – 1.2 and classified as inactive to normal clay. High linear shrinkage (> 10%), low compacted density and predominan...
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Journal of Sedimentary Environments
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Journal of African Earth Sciences
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Journal of African Earth Sciences (and the Middle East)
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Journal of African Earth Sciences, 2015
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High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin... more High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin subsidence, very thick clayey members of Agbada and Akata Formations as well as prevailing presence of growth faults had been identified as the main factors responsible for overpressure generation and preservation in the Niger Delta basin. Analysis of porosity dependent parameters such
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Acta Geodaetica et Geophysica, 2013
ABSTRACT Ijebu-Ode and its environs in southwestern Nigeria is located on a geological transition... more ABSTRACT Ijebu-Ode and its environs in southwestern Nigeria is located on a geological transition zone from the Precambrian migmatite gneiss rocks and Cretaceous sedimentary rock units of Abeokuta Group. Unique geological structures, complex coexistence of different rock types and poorly defined basal/lateral contacts between the basement and sedimentary rocks typify tectonic events that accompany crustal thinning and downwarping at the basement/sedimentary-basin edge. This posed serious geological decision challenges especially since it is difficult to characterize the area either as sedimentary or crystalline. Aeromagnetic data were collected, the data were filtered, inverted and enhanced using appropriate software packages and subsequently employed to generate model of the subsurface basement topography. The magnetic intensity distribution in the field ranged from −120 to +80 nT and was found to depend on the size, depth of burial and the thickness of low susceptibility superficial material overlying the magnetite rich crystalline rocks. High magnetic intensity characterized the basement rocks while lower values distinguished the metasediments rocks and sedimentary terrain. The average radial power analysis delineated shallow and relatively deep sources as the two distinct types of magnetic anomalies. Euler deconvolution results referenced to the Minna, Nigeria datum indicate depth range from −80 to +30 m for sources located below and above the mean ground level, respectively. Euler result also revealed that the depth to magnetic sources is heterogeneous and highly erratic around the transition zone, ranging between −25 and +12 m. This study identified rugged and undulating basement topography around the contact zone; it also delineated the lateral and basal contacts between the two coexisting rock types. Aeromagnetic mapping of basement sedimentary transition zone around Ijebu-Ode has proved very efficient in providing relevant information about the nature of the basement topography which provided vital information requisite for drilling and some engineering constructions decisions.
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Journal of African Earth Sciences, 1997
ABSTRACT The magnitude of errors in the determination of depth to bedrock from Wenner and Schlumb... more ABSTRACT The magnitude of errors in the determination of depth to bedrock from Wenner and Schlumberger resistivity sounding curves, caused by the non-identification of a suppressed layer, has been investigated. The principal objective is to evaluate how the layer thicknesses and resistivities affect the accuracy of depth estimates. In the computations, the intermediate layer in a 3-layer model, in which the resistivity increases with depth, is removed and the 2-layer sounding curve that is electrically equivalent to the 3-layer curve is generated. The results indicate that there is a possibility for large depth underestimations when the resistivity contrast between layers 1 and 2 is very large. This is manifested in a steeply rising terminal branch on the sounding curve. There is a slight decrease in the depth underestimation as the resistivity contrast between layers 2 and 3 increases. Conversely, if the intermediate layer is fairly thick and the resistivity contrasts are not too large, the best-fit 2-layer curve shows large deviations from the 3-layer curve. In such cases, the intermediate layer can be identified, resulting in reliable depth estimates. A field example from Nigeria is presented in which the sounding data has been interpreted so as to account for a prebasement layer of intermediate resistivity, indicative of a fractured granite.
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Journal of African Earth Sciences, 2015
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Bookmarks Related papers MentionsView impact
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High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin... more High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin subsidence, very thick clayey members of Agbada and Akata Formations as well as prevailing presence of growth faults had been identified as the main factors responsible for overpressure generation and preservation in the Niger Delta basin. Analysis of porosity dependent parameters such as interval transit times and interval velocities derived from the seismic records of a field in the Western Niger Delta revealed the presence of overpressured formation at depth of 8670 feet, which is the top of the overpressured zone. The plot of interval transit times against depth gave a positive deflection from normal at the region of overpressure while interval velocity plot gave negative deflection; the ratio of this deviation in both cases is as high as 1.52. Pressure gradient in the upper, normally pressured part of the field was determined to be 0.465 psi/ft., which is within the established nor...
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Hydrogeology Journal, 2008
Page 1. Fuzzy logic modeling of the resistivity parameter and topography features for aquifer ass... more Page 1. Fuzzy logic modeling of the resistivity parameter and topography features for aquifer assessment in hydrogeological investigation of a crystalline basement complex MA Adabanija & EO Omidiora & AI Olayinka Abstract ...
Bookmarks Related papers MentionsView impact
Olayinka, A.I. and Yaramanci, U., 2002. Smooth and sharp-boundary inversion of two-dimensional ps... more Olayinka, A.I. and Yaramanci, U., 2002. Smooth and sharp-boundary inversion of two-dimensional pseudosection data in presence of a decrease in resistivity with depth. European Journal of Environmental and Engineering Geophysics, 7: 139-165. The smooth and sharp-boundary inversion of two-dimensional (2D) apparent resistivity pseudosection data in cases where the half-space has a lower resistivity than the overburden is investigated. The study entailed calculation (by forward modelling) of the synthetic data over simple 2D geologic models and inversion of the data. The 2D structures modelled include vertical fault, graben and horst. The Wenner array was used. The results show that there is generally an improvement in the model misfit with iteration number in smooth inversion; the algorithm can then be expected to iterate to the best solution at a high iteration number where the model resistivity of the substratum approaches the true bedrock resistivity. Inversion of the data using sha...
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Journal of Applied Sciences, 2011
Leachate-effluent from refuse dump site is an important source of groundwater pollution. Conseque... more Leachate-effluent from refuse dump site is an important source of groundwater pollution. Consequently, assessing the impact of leachate is an active area of groundwater research. Geoelectrical imaging was carried out at an abandoned waste dump site in Ibadan, southwestern Nigeria, with the aim of determining how accurately electrical measurements could delineate the influx of leachate into groundwater and surface water. Eight electrical-resistivity profiles were measured. Four of the traverses were conducted on the dump site whereas two traverses were measured towards the lower side to assess possible ingress of the leachate. The other two lines were measured about 300 m from the site to serve as control. Elevation data were collected using Global Positioning System. The resistivity data were inverted using the least-square technique. The inversion delineated regions of low resistivity (<20 Ωm) believed to be leachate derived from decomposed waste. Non-degraded refuse occurred as isolated regions of higher resistivity (>20 Ωm). The highest resistivity regions (>100 Ωm) were interpreted as regolith derived from chemical weathering of the crystalline bedrock. Resistivity-derived thickness of the leachate zone was consistent with the thickness derived from the elevation data. It could be inferred that there was high concentration of leachate towards the lower elevation hence the adjoining stream is prone to pollution. This study showed that 2D imaging can be effective in imaging pollution plumes around refuse dump sites. The method can be useful to assess opportunity for remediation measures in situations where the leachate has reached the groundwater system.
Bookmarks Related papers MentionsView impact
Journal of Petroleum Exploration and Production Technology
One of the complexities of geomechanical study is in the classification of rock’s properties and ... more One of the complexities of geomechanical study is in the classification of rock’s properties and overpressured intervals—a knowledge which is not only essential for well safety and cost-effective drilling, but crucial in evaluating exploration risk factors and ensuring a successful hydraulic fracturing program. In this study, a more robust prediction of reservoir pressure regime is presented, where the geomechanical distributions of the rock give a distinct correlation. Three wells from the Niger Delta Basin were studied using empirical equations to estimate the elastic properties, wave velocities and the rock physics parameters for each well. From the results obtained, the velocities of compressional wave (Vp) and shear wave (Vs) decrease as porosity increases. Also, a linear correlation exists between Poisson’s ratio and Vp/Vs, where both variables showed distinct behavior and similar trend serving as useful tools for lithology identification. Another significant observation is th...
Bookmarks Related papers MentionsView impact
Petroleum
Bookmarks Related papers MentionsView impact
Geomechanics and Geophysics for Geo-Energy and Geo-Resources
A pre-existing plane of weakness along the fault is comprised of a particular pattern of joints d... more A pre-existing plane of weakness along the fault is comprised of a particular pattern of joints dipping at different orientations. The fault stress state, partially defined by the orientation of fault, determines the potential of slip failure and hence the evolution of fault permeability. Here the influence of fault orientation on permeability evolution was investigated by direct fluid injection inside fault with three different sets of fault orientations (45°, 60° and 110°), through the coupled hydromechanical (H-M) model TOUGHREACT-FLAC3D. The influence of joints pattern on slip tendency and magnitude of potential induced seismicity was also evaluated by comparing the resulted slip distance and timing. The simulation results revealed that decreasing the dip angle of the fault increases the corresponding slip tendency in the normal fault circumstance. Also, with changing joints dip angle associated with the fault, the tendency of the fault slip changes concurrently with the permeab...
Bookmarks Related papers MentionsView impact
Geology, Geophysics and Environment
The high global numbers of road accidents due to bad roads and the failure of other engineering s... more The high global numbers of road accidents due to bad roads and the failure of other engineering structures have necessitated this study, particularly as road transport accounts for a higher percentage of cargo movement in African countries. The geophysical investigation was carried out on six failed and two stable sections along the Ibadan-Iwo-Osogbo highway to examine the geological factors responsible for highway failure in the area. A Landsat ETM+ (Enhanced Thematic Mapper Plus) imagery of the study area and its environs was acquired and processed for lineaments analyses. Magnetic, Very Low Frequency Electromagnetic (VLF-EM) and electrical resistivity methods involving Schlumberger Vertical Electrical Sounding (VES) and 2-D imaging using a dipole- dipole array were utilized. Lineaments were identified across failed localities. Lateral magnetic variations in the near-surface geological materials characterized the study area. The 2-D VLF-EM models generated showed conductive zones ...
Bookmarks Related papers MentionsView impact
Rudarsko-geološko-naftni zbornik
Engineering geological investigation of some unstable and stable sections of the Ibadan-Iwo-Osogb... more Engineering geological investigation of some unstable and stable sections of the Ibadan-Iwo-Osogbo highway was undertaken to unravel the intrinsic reasons responsible for continuous pavement failure along this road. Eighty disturbed and forty undisturbed soil samples were collected at different depths from twenty test pits of six selected failed sections (FS) and two stable sections (SS). Road construction analysis was done on these soil samples using standard methods. Liquid limit (22 - 64% and 32 - 40%), plasticity index (13 - 41% and 12 - 18%) and percentage fines (47 - 59% and 32 - 41%) indicated fair to poor and fair to good subgrade materials of FS and SS respectively. Medium to high plasticity and high clay content of soils of FS are indicative that the soils possess medium to high swelling potential. The activity of clay in soils of FS was approximately 0.3 – 1.2 and classified as inactive to normal clay. High linear shrinkage (> 10%), low compacted density and predominan...
Bookmarks Related papers MentionsView impact
Journal of Sedimentary Environments
Bookmarks Related papers MentionsView impact
Journal of African Earth Sciences
Bookmarks Related papers MentionsView impact
Journal of African Earth Sciences (and the Middle East)
Bookmarks Related papers MentionsView impact
Journal of African Earth Sciences, 2015
Bookmarks Related papers MentionsView impact
High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin... more High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin subsidence, very thick clayey members of Agbada and Akata Formations as well as prevailing presence of growth faults had been identified as the main factors responsible for overpressure generation and preservation in the Niger Delta basin. Analysis of porosity dependent parameters such
Bookmarks Related papers MentionsView impact
Acta Geodaetica et Geophysica, 2013
ABSTRACT Ijebu-Ode and its environs in southwestern Nigeria is located on a geological transition... more ABSTRACT Ijebu-Ode and its environs in southwestern Nigeria is located on a geological transition zone from the Precambrian migmatite gneiss rocks and Cretaceous sedimentary rock units of Abeokuta Group. Unique geological structures, complex coexistence of different rock types and poorly defined basal/lateral contacts between the basement and sedimentary rocks typify tectonic events that accompany crustal thinning and downwarping at the basement/sedimentary-basin edge. This posed serious geological decision challenges especially since it is difficult to characterize the area either as sedimentary or crystalline. Aeromagnetic data were collected, the data were filtered, inverted and enhanced using appropriate software packages and subsequently employed to generate model of the subsurface basement topography. The magnetic intensity distribution in the field ranged from −120 to +80 nT and was found to depend on the size, depth of burial and the thickness of low susceptibility superficial material overlying the magnetite rich crystalline rocks. High magnetic intensity characterized the basement rocks while lower values distinguished the metasediments rocks and sedimentary terrain. The average radial power analysis delineated shallow and relatively deep sources as the two distinct types of magnetic anomalies. Euler deconvolution results referenced to the Minna, Nigeria datum indicate depth range from −80 to +30 m for sources located below and above the mean ground level, respectively. Euler result also revealed that the depth to magnetic sources is heterogeneous and highly erratic around the transition zone, ranging between −25 and +12 m. This study identified rugged and undulating basement topography around the contact zone; it also delineated the lateral and basal contacts between the two coexisting rock types. Aeromagnetic mapping of basement sedimentary transition zone around Ijebu-Ode has proved very efficient in providing relevant information about the nature of the basement topography which provided vital information requisite for drilling and some engineering constructions decisions.
Bookmarks Related papers MentionsView impact
Journal of African Earth Sciences, 1997
ABSTRACT The magnitude of errors in the determination of depth to bedrock from Wenner and Schlumb... more ABSTRACT The magnitude of errors in the determination of depth to bedrock from Wenner and Schlumberger resistivity sounding curves, caused by the non-identification of a suppressed layer, has been investigated. The principal objective is to evaluate how the layer thicknesses and resistivities affect the accuracy of depth estimates. In the computations, the intermediate layer in a 3-layer model, in which the resistivity increases with depth, is removed and the 2-layer sounding curve that is electrically equivalent to the 3-layer curve is generated. The results indicate that there is a possibility for large depth underestimations when the resistivity contrast between layers 1 and 2 is very large. This is manifested in a steeply rising terminal branch on the sounding curve. There is a slight decrease in the depth underestimation as the resistivity contrast between layers 2 and 3 increases. Conversely, if the intermediate layer is fairly thick and the resistivity contrasts are not too large, the best-fit 2-layer curve shows large deviations from the 3-layer curve. In such cases, the intermediate layer can be identified, resulting in reliable depth estimates. A field example from Nigeria is presented in which the sounding data has been interpreted so as to account for a prebasement layer of intermediate resistivity, indicative of a fractured granite.
Bookmarks Related papers MentionsView impact
Journal of African Earth Sciences, 2015
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin... more High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin subsidence, very thick clayey members of Agbada and Akata Formations as well as prevailing presence of growth faults had been identified as the main factors responsible for overpressure generation and preservation in the Niger Delta basin. Analysis of porosity dependent parameters such as interval transit times and interval velocities derived from the seismic records of a field in the Western Niger Delta revealed the presence of overpressured formation at depth of 8670 feet, which is the top of the overpressured zone. The plot of interval transit times against depth gave a positive deflection from normal at the region of overpressure while interval velocity plot gave negative deflection; the ratio of this deviation in both cases is as high as 1.52. Pressure gradient in the upper, normally pressured part of the field was determined to be 0.465 psi/ft., which is within the established nor...
Bookmarks Related papers MentionsView impact