Browsing by Author "Ajadi, J"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Aeromagnetic and Resistivity Tomography Technique for Investigating Leakage Paths in Apodu Dam, Ilorin Sheet 201, Southwestern Nigeria(Alhikmah University, 2021) Olawumi, HB; Olatunji, S; Ajadi, J; Abubakar, HOThe aeromagnetic and electrical resistivity tomography technique was used to evaluate the foundation conditions and stability of the Apodu earth dam located around Malete, Ilorin Sheet 201, Southwestern Nigeria. The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources controlling subsurface geology. The extracted lineament structures were employed to examine features controlling the distribution of surface and subsurface hydraulic substances cum stability of dam slope. Magnetic lineaments' length and parallelism in some areas suggested installation under a tensional stress field along pre-existing zones of weakness.Magnetic susceptibilities are not uniform in the area and were categorized viz: high, moderate, and low. The magnetic intensity range at Apodu dam is -644.19 to 285.40 nT. The northeastern part of the study area where the Apodu dam is located shows little or no sign of faulting and appears to be more stable structurally. Characterization of the Apodu dam subsurface for seepage appraisal using electrical resistivity tomography technique revealed that the dam is well compacted at the surface but with observed low resistivity values indicative of possible occurrences of weakness zones that are water-bearing in some areas of the dam embarkment body at depths of around 8m and 25m. These observed low resistivity zones indicating a water-bearing weakness zone were connected in RTM1 and RTM2, and a possible water pathway was established. This water pathway is indicative of a possible seepage pathway and adequate measures are expected to be made to arrest the situation. In conclusion, Apodu dam is situated in a geologically stable environment as deduced from the aeromagnetic study but its earth embarkment is suspected to possess areas with possible seepage zones as obtained from the electrical resistivity techniques of investigations. There is therefore a need to quickly remedy the dam earth embankment to ensure the longevity of the dam and avert possible failure.Item Characterization of Petrophysical Properties of Reservoirs in Bima Formation, Northeastern Nigeria: Implication for Hydrocarbon Exploration(Department of Geology School of Physical Sciences, Federal University of Technology, Minna, 2021) Omolaiye, GE; Ajadi, J; Olatunji, S; Jimoh, AY; Ubulom, DENCharacterization of petrophysical properties of reservoirs in Bima Formation was undertaken to understand their spatial distribution and impacts on hydrocarbon saturation in the highly heterolithic siliciclastic sequence. The study was carried out using nine well logs from Maiduguri and Baga/Lake sub-basins within the Borno Basin. Evaluation of the formation reveals largely undifferentiated to highly serrated and lenticular sand bifurcated by shale beds, which reduced their thicknesses variably from 0.61 to 6.1 m. The shale content in the sand bodies ranged from 11.00% to 88.00%. The formation also has variable porosity values, with calculated total porosity ranged from 10.00% to 35.00%. Similarly, effective porosity values spanned between 2.00 to 24.00%. The irregular porosity values also accounted for a wide range of field average permeability estimates computed for the formation, which measured between 0.03 to 319.49mD. Hydrocarbon saturation also varied from 40.00 to 78.00%. Gas accumulation was encountered in Ga-1, Da-1, Ar-1 and Ye-1 wells. These highly thin serrated sand beds with variable porosity and permeability constitute exploration challenges. The very thinly laminated or serrated alternation of sand and shale beds lithofacies of the Bima Formation is supportive of fluvio-lacustrine depositional environments.Item Determination and Distribution of Formations Thickness in Baga/Lake Sub-Basin using Seismic Imaging and Well data, Chad Basin Nigeria(Alhikmah University,, 2021) Olatunji, Saminu; Omolaiye, GE; Ajadi, JThe Borno Basin is located in North-Eastern Nigeria, formed in the Early Cretaceous. Deposition of sediments in the basin occurred during rifting. The sediments are mainly lacustrine shales and sandstones. This work was undertaken by the integration of 3D seismic interpretations and the well data analysis of eight wells fairly distributed in the study area to determine the thickness of the formations within the sub-basin. Da-1 well used in this study was subdivided into stratigraphic units based on the regional stratigraphic subdivision of the Chad basin and was later correlated with other wells using the similarity of observed log responses. Density and sonic logs were used to generate synthetic seismograms for seismic to well ties. Five horizons were interpreted, representing the tops of the formations on the 3D seismic data covering the block, average velocity function with a maximum residual of 0.48% was used for the time to depth conversion in all the generated maps. There is a general thickening of sediments from the west to the east and the estimated thicknesses of the various Formations in the Baga/Lake sub-basin are; Chad (400-750 m), Kerri-Kerri (300-1200 m), Fika (300-1000 m) and Gongila (100-1300 m). The thickness of the Bima Formation could not be established because the deepest well terminates within the Formation. This is a modification to the previous and widely referenced studies of over fifty decades that based the estimation of formation thickness within the study area on the observed outcrops and the use of a few water boreholes.Item Evaluation of Groundwater Level Time-Dependent Variation and Aquifer Characteristics within Sheet 223 Ilorin North-West, Southwestern Nigeria(Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University, 2022) Ajadi, J; Issa, U; Olatunji, SThe assessment of groundwater level time-dependent variation and aquifer characteristics has been carried out, aimed at knowing the variation in groundwater elevation at the end of the rainy season and at the peak of the dry season. The time-dependent variation was done by direct in situ groundwater level measurement from eighty existing wells. Aquifer characteristics were determined by using pumping test data of the available boreholes in the area, using a modified Jacob's method. Configuration of groundwater level contours shows that the highest groundwater elevation in the area is 445 m and the lowest is 295 m above sea level. Also, areas with water levels ranging between 1 and 2 m are areas of low water level while areas with water levels ranging between 9.5 m and 11 m are areas of high water level. Transmissivity is estimated to range between 3.49 and 8.50 m2 /day with an average value of [5.61 m2 /day, Hydraulic conductivity range between 2.18 × 10-1 and 7.64× 10-2 m /day with an average value of 1.65 x 101 m /day and Storativity range from 3.45 to 9.15 with an average value of 5.04. Areas with shallow water levels, depicting high potential, are in the southern part while the northern part is an area of low groundwater potential. The average value for Storativity is higher than the assigned limit (0.005-0.00005) for most confined aquifers, indicating that the storage potential of the boreholes is high; hence their recharge potential is high.Item Evaluation of Groundwater Level Time-Dependent Variation and Aquifer Characteristics within Sheet 223 Ilorin North-West, Southwestern Nigeria(Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University, 2022) Ajadi, J; Issa, U; Olatunji, SThe assessment of groundwater level time-dependent variation and aquifer characteristics has been carried out, aimed at knowing the variation in groundwater elevation at the end of the rainy season and at the peak of the dry season. The time-dependent variation was done by direct in situ groundwater level measurement from eighty existing wells. Aquifer characteristics were determined by using pumping test data of the available boreholes in the area, using modified Jacob's method. Configuration of groundwater level contours shows that the highest groundwater elevation in the area is 445 m and the lowest is 295 m above sea level. Also, areas with water levels ranging between 1 and 2 m are areas of low water level while areas with water levels ranging between 9.5 m and 11 m are areas of high water level. Transmissivity is estimated to range between 3.49 and 8.50 m2 /day with an average vale of [5.61 m2 /day, Hydraulic conductivity range between 2.18 × 10-1 and 7.64× 10-2 m /dav with an average value of 1.65 x 101 m /day and Storativity range from 3.45 to 9.15 with an average value of 5.04. Areas with the shallow water level, depicting high potential, are in the southern part while the northern part is an area of low groundwater potential. The average value for Storativity is higher than the assigned limit (0.005-0.00005) for most confined aquifers, indicating that the storage potential of the boreholes is high; hence their recharge potential is high.Item Geophysical Assessment for Characterising Leakages from Asa dam, Nigeria(Faculty of Pure and Applied Sciences, Ladoke Akintola University of Technology, 2021) Olawumi, HB; Olatunji, S; Ajadi, J; Abubakar, HOAeromagnetic and Electrical resistivity tomography techniques were used to evaluate the foundation conditions and stability of the Asa earth dam located in Ilorin. The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources that are controlling the subsurface geology. The extracted lineament structures were employed to examine features that are controlling the distribution of surface and subsurface hydraulic substances which affects the stability of the dam. The nature of the magnetic lineaments in some parts of the area suggests rock emplacement under a tensional stress field. Magnetic susceptibilities are not uniform in the area and were categorized viz: high, moderate, and low. The magnetic intensity range at Asa dam is 126.56 to -20.90 nT. The northwestern part of the Asa dam area shows little or no sign of faulting and appears to be more stable structurally than the other part of the study area. Characterization of Asa dam earth embankments for seepage appraisal using resistivity tomography technique revealed that the Asa dam is well compacted with no sign of any seepage. In conclusion, the Asa dam is situated in a geologically stable environment as deduced from the aeromagnetic study, while the earth embankments are well compacted with no sign of seepage as obtained from the electrical resistivity tomography technique of investigationsItem Groundwater Potential Evaluation in Parts of Southwestern Nigeria using Dar-Zarouk Parameters(Department of Civil Engineering, Ladoke Akintola University of Technology, Ogbomoso, 2022) Olatunji, S; Issa, U; Ajadi, JDar-Zarouk parameters namely longitudinal conductance, transverse unit resistance, longitudinal resistivity, traverse resistivity, and coefficient of anisotropy; derived from electrical resistivity soundings, were employed in the western and south western portions of Sheet 223 Ilorin NW, Southwestern Nigeria to evaluate the subsurface water prospect. This is aimed at determining the potentiality and vulnerability of groundwater in the area. The longitudinal conductance values obtained range from 0.027 S at VES 3 in the north, indicating the poorest protective capacity, to 26440.95 S at VES 157 in the south, indicating the highest protectivity. Thus, the protective capacity rating of the study area shows very poorly, weak, moderate, good, and excellent ratings at VES stations 10, 12, 9, 2, and 178 respectively. The total transverse resistance range is 8.6 - 32733.87 Ωm2, with the lowest at VES 206 in the southeastern part, indicating high prospects, and the highest at VES 47 in the northern part of the area, indicating poor prospect. The lowest longitudinal resistivity (0.1951 Ωm), indicating high potential as well, occurs at the southern part and while the highest value of 8095.63 Ωm is obtained at the northern part. Furthermore, the coefficient of anisotropy in the area ranges between 0.029 and 5349.78. The southwestern boreholes have values that fall between the standard range of 1.39-1.66, indicating that those protective capacities and high potentiality areas have boreholes with high productivity: In conclusion, most parts of the study area have excellentItem Groundwater Potential Evaluation in Parts of Southwestern Nigeria using Dar-Zarouk Parameters(Department of Civil Engineering, Ladoke Akintola University of Technology, 2022) Olatunji, S; Issa, U; Ajadi, JDar-Zarouk parameters namely longitudinal conductance, transverse unit resistance, longitudinal resistivity, traverse resistivity, and coefficient of anisotropy; derived from electrical resistivity soundings, were employed in the western and southwestern portions of Sheet 223 Ilorin NW, Southwestern Nigeria to evaluate the subsurface water prospect. This is aimed at determining the potentiality and vulnerability of groundwater in the area. The longitudinal conductance values obtained range from 0.027 S at VES 3 in the north, indicating the poorest protective capacity, to 26440.95 S at VES 157 in the south, indicating the highest protectivity. Thus, the protective capacity rating of the study area shows very poor, weak, moderate, good, and excellent ratings at VES stations 10, 12, 9, 2, and 178 respectively. The total transverse resistance range is 8.6 - 32733.87 Ωm2, with the lowest at VES 206 in the southeastern part, indicating high prospects, and the highest at VES 47 in the northern part of the area, indicating poor prospects. The lowest longitudinal resistivity (0.1951 Ωm), indicating high potential as well, occurs in the southern part and while the highest value of 8095.63 Ωm is obtained in the northern part. Furthermore, the coefficient of anisotropy in the area ranges between 0.029 and 5349.78. The southwestern boreholes have values that fall between the standard range of 1.39-1.66, indicating that those protective capacities and high potentiality areas have boreholes with high productivity: In conclusion, most parts of the study area have excellentItem Velocity Analysis for Depth Conversion: A Case Study of Block A, Baga/Lake Sub-basin in the Borno Basin, Northeastern Nigeria(Department of Geology School of Physical Sciences, Federal University of Technology, Minna, 2021) Omolaiye, GE; Olatunji, S; Ajadi, J; Jimoh, AYTime-depth conversion analysis of time-migrated seismic images was undertaken on Block A, Baga/Lake sub-basin of Borno basin Nigeria, to predict the appropriate velocity model suitable for depth conversion away from six existing well control points. Three velocity models were used for the time-to-depth conversion including the average velocity-time analytical function, 2nd Order Polynomial time-depth analytical function, and instantaneous velocity analytical function. The velocity models were tested with the shallow and deep horizons representing the tops of Kerri-Kerri and Gongila Formations penetrated by six wells fairly spread on the 3,891 km? of 3D seismic data. The results show that each model has a variable degree of accuracy after depth conversion at the two formation tops. The average velocity-time analytical technique appeared as the best technique for the time-depth conversion having errors in the range of -0,12 to 145 meters at shallow and deeper formations respectively. The 2nd-order polynomial time-depth analytical function and Vo-K techniques gave a depth uncertainty greater than 135 meters at the shallow formation and over 1,000 meters at the deeper formation. The maximum percentage error recorded for both formations using the average velocity technique was 0.48% this is less than 5% and considered good in the practical situation, it is therefore recommended to be used for velocity modeling and depth conversion study in the Baga/Lake sub-basin of Borno Basin, Northeastern Nigeria.