Browsing by Author "Uko, Etim D."

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    Effects of Near-Surface Air Temperature on Sub-Surface Geothermal Gradient and Heat Flow in Bornu-Chad Basin, Nigeria
    (Department of physics, Nasarawa State Univesity Keffi, 2021-04-01) Tyor, Andrew A.; Uko, Etim D.; Anyanninuola, O.S.; Onengiyeofori, A.
    A study of the effect of near-surface temperature on fields of subsurface geothermal gradient and heat flow has been carried out in the Bornu-Chad Basin, Nigeria, using corrected Bottom-Hole Temperatures (BHTc) lithologic-log data from 9 oil wells. The geothermal gradient using only BHTs ranges from 15.9oCkm-1 to 38.2oCkm-1 with an average of 26.9+/-3.5oCkm-1, while that computed with mean annual temperature and BHTs ranges from 28.2oCkm-1 to 51.5oCkm-1with an average of 37.5+/-2.5oCkm-1. The geothermal gradient using the mean annual temperature and BHTs in the Bornu-Chad is higher than using only BHTs by 7.0oCkm-1. Heatflow ranges from a minimum of 61 mWm-2 to a maximum of 114mWm-2 with an average of 68+/-5.89mWm-2. The isotherm maps exhibit an increasing SW-NE trend. An average heat flow of 68+/-5.9mWm-2 deduced from Bornu-Chad basin is normal for a continental passive margin with age of about 100My. Geothermal gradient results show a distinct and direct relationship with nearsurface conditions. There are indications that surface heat flow is controlled by lithology, geothermal gradient and near-surface solar radiation conditions in the Bornu-Chad basin. Consequently, it is recommended that the mean surface temperature be used in geothermal gradients and heatflows estimations. The knowledge of geothermal properties is very important in the search for geothermal energy in the area of study.
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    Estimation of The Structural Pattern and Sedimentary Thickness Over Part Of Anambra Basin, Nigeria Using Aeromagnetic Data
    (Department of physics, Nasarawa State Univesity Keffi, 2021-02-02) Ikiola, Priscilla E.; Ofoegbu, Charles O.; Uko, Etim D.; Anyanninuola, O.S.
    Aeromagnetic data acquired over part of the Anambra Basin is analyzed to determine the structural pattern and sedimentary thickness of the basin. The study area is covered by high resolution aeromagnetic data on sheets 301 (Udi), 302 (Nkalagu), 312 (Okigwe) and 313 (Afikpo), and lies between latitudes 5o30'0''-6o30'0'' and longitudes 7o0'0"-8o0'0". The whole area was divided into 25 overlapping blocks of 37.2km2 each and a 2D energy spectral analysis was carried out. Total magnetic intensity data was subjected to filtering and analytical techniques to determine the structural pattern, mineralization potential, depth to the basement, variation in the sedimentary thickness. The structural map generated using the vertical derivatives shows that the major structural orientation of the area is in the ENE-WSW trend and the minor trend is the NW to SE direction widespread all over the area. These structures are as a result of the various near-surface magnetic intrusion within the study area. The spectral analysis result shows two depth layers, the deep and the shallow depth, the depth to magnetic basement for the deep anomalous source ranges from 3.3km to 4.84km with an average depth of 3.99km, while the depth to shallow magnetic sources ranges between 0.46km to 0.67km and an average of 0.56km within the area. The mineralization pattern in this area follows the ENE-WSW direction.
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    pectral Analysis of Aeromagnetic Data over Some Parts of Central Benue Trough, Nigeria
    (Department of physics, Nasarawa State Univesity Keffi, 2019-03-28) Ibiene, I.E.; Ofoegbu, Charles O.; Anyanninuola, O.S.; Uko, Etim D.
    The spectral analysis of the magnetic anomalies over some part of Central Benue Trough, Nigeria, has been carried out in order to determine the magnetic source depths and the variability of basement structures. The aeromagnetic maps of the study area was digitized at two kilometer (2km) intervals and were subjected to multi-regression-least-squares analysis in order to obtain the residual field values. Two- dimensional (2-D) spectral analyses were then carried out to determine the average magnetic source depths. The results of the analysis reveal that the thickness of the sedimentary cover in the area varies between 1.25km and 5.60km; and 0.13km and 1.53km for deeper and shallower sources respectively. The results of this study are indicative of the basement overlain being irregular in shape and is associated with faulted structures
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    VELOCITY LAYERING IN THE MIDDLE BENUE TROUGH NIGERIA USING SEISMIC REFRACTION DATA
    (Department of physics, Nasarawa State Univesity Keffi, 2022-01-01) Abdullateef, Abidemi H.; Uko, Etim D.; Ayanninuola, O.S.
    Seismic refraction data was acquired in the Middle Benue Trough which is located in the north central Nigeria with latitude 07.5-08.5oN and longitude 08.00-09.30oE. The aim was to find out how velocity vary in the near- surface layers in the area using seismic refraction data. The seismic survey was investigated at 14 acquisition stations. Two overlapping reversed profiles were shot into 14 stations. Each acquisition station was primed with 0.20kg dynamite loaded at 1.5m below the surface. The recording equipment was McSeis-160MXTM, and monitor record was processed with Microsoft Excel software to determine the velocities from both the forward and reversed shot-points. The results show two distinct layers cases. The thickness of the topmost layer varies between 2.75m and 5.45m with a mean of 4.1m. The velocity of this topmost layer varies between 399.0 ms-1 and 767.0ms-1 with a mean of 604.8ms-1. The velocity of the underlying layer (V1) varies between 1212.5ms-1 and 3257.0ms-1 with a mean of 1757.9ms-1. The velocity increases with depth into the subsurface. The results are useful in locating groundwater aquifer, and in the design of source-receiver arrays for reflection seismic.