Levi Nwankwo - Academia.edu (original) (raw)

Papers by Levi Nwankwo

Archives of Applied Science Research, 2012

A renewed interest to continually search for hydrocarbon prospects in the deep offshore West Afri... more A renewed interest to continually search for hydrocarbon prospects in the deep offshore West Africa climaxed after the discovery of a rewarding oil prospects around the deep offshore basin of Mauritania. However, recent statistics showed that, viable prospects along this region are increasingly becoming difficult to locate and that, future success will greatly depend on identifying 'structural and stratigraphic traps' within prospective areas. In this study, digitised aeromagnetic data covering part of Niger Delta was processed and gridded to generate the residual map as well as the depth to basement maps. On these maps, potential areas for hydrocarbon traps were delineated accordingly. Oasis Montaj geophysical software was used throughout the data processing and analysis. The average thickness of the sediments or depth to basement varies from 0 km on the outcrops to as much as 10.7 km within the study area, large enough for hydrocarbon accumulation. In addition to that, eleven intrusives were mapped from 2.5D forward and inverse modeling, with lateral extents of 1.5 km-6.0 km. The presence of these intrusives made parts of the study area less favourable for hydrocarbon exploration. The structurally low areas were also outlined from the depth to basement maps. Interestingly, most of the oil producing fields were reportedly located within the structurally low areas of the basin. Hence, it is recommended that a detailed seismic prospecting be carried out around the structurally low areas in 'the new frontiers'.

Global Journal of Pure and Applied Sciences, Dec 3, 2009

An estimate of Curie-point isotherm depths has been made in the northern part of the Nupe Basin, ... more An estimate of Curie-point isotherm depths has been made in the northern part of the Nupe Basin, west of Central Nigeria, from the spectral analysis of aeromagnetic data. Curie-point, the temperature at which rocks lose their ferromagnetic properties, provides a link between thermal models and models based on the analysis of magnetic sources. The result of this study shows that the Curie isotherm depth varies between 12 and 30km in the study area. In the southern portion of the study area, the curie-depth was found above 28km while it was found to be less than 14km in the northern part. It had previously been discovered by earlier workers that Curie-point depths are shallower than 15km for volcanic and geothermal fields, between 15-25km for island arcs and ridges, and deeper than 20km in plateaus and trenches. Therefore, when the values for the study area are compared with these values, the areas with variations less than 15km maybe recommended for further geothermal reconnaissance studies.

Arabian Journal of Geosciences, Aug 30, 2017

Understanding the thermal distribution within the crust and rheology of the earth's lithosphere r... more Understanding the thermal distribution within the crust and rheology of the earth's lithosphere requires the knowledge of the Depth to the Bottom of Magnetic Sources (DBMS). This depth is an important parameter in this regard, which can be derived from aeromagnetic data and can be used as a representation for temperature at depth where heat flow values can be evaluated. In this work, high-resolution aeromagnetic (HRAM) data of part of Chad Basin (covering about 80% of the entire basin), an area bounded by eastings 769,000 and 1,049,900 mE and northings 1,200,000 and 1,500,000 mN, were divided into 25 overlapping blocks and each block was analyzed using spectral fractal analysis method. The spectral analysis method was used to obtain the Depth to the Top of Magnetic Source (DTMS), centroid depth, and DBMS. From the calculated DBMS, the geothermal gradient and heat flow parameters were evaluated and the result obtained shows that DBMS varies between 18.18 and 43.64 km. Also the geothermal gradient was found to be varying between 13.29 and 31.90°C/km and heat flow parameters vary between 33.23 and 79.76 mW/m 2 , respectively. The heat distribution of this area is one of the key parameters responsible for various geodynamic processes; therefore, this work is important for numerically understanding the thermal distribution in Chad Basin, Nigeria since rock rheologies depend on temperature, which is a function of depth.

Asian Journal of Earth Sciences, Dec 15, 2010

IOP conference series, Jul 1, 2018

Depth to magnetic basement and mapping of source geometries were estimated from High Resolution A... more Depth to magnetic basement and mapping of source geometries were estimated from High Resolution Aeromagnetic (HRAM) data of Benisheikh using wavelet transformation technique. This technique was chosen because it has been proven to be a powerful and efficient tool in interpreting potential field data. In this work, a non-orthogonal wavelet function with a good symmetry and higher vanishing moment, Morlet was chosen as the analyzing wavelet. Wavelet power spectrums of the aeromagnetic anomalies were obtained using the scaled normalized analyzing wavelet in order to estimate the depth to the magnetic basement. Also, the square of the absolute value of the wavelet coefficient were plotted against the period in other to identify and map variations of pronounced and least energy values which can be regarded as magnetic source geometric features found from the HRAM data profiles. The results obtained from the analysis have shown the ability of wavelet transform as a tool in depth estimation and mapping of geological features of HRAM data of this part of Nigeria.

A study of the radioactivity in groundwater from Tanke-Ilorin, Nigeria, has been carried out. Ten... more A study of the radioactivity in groundwater from Tanke-Ilorin, Nigeria, has been carried out. Ten water samples were analyzed by -ray spectroscopy to determine the 226Ra and 228Ra concentrations. The activity concentration values range from 0.81 ± 0.08 to 7.4 ± 2.2 Bq/l for 226Ra and from 1.8 ± 0.3 to 5.6 ± 2.6 Bq/l for 228Ra. The derived Annual Effective Dose received by the population as a result of the ingestion of 226Ra was estimated to range from 0.08 ± 0.01 to 0.12 ± 0.07 mSv/y with an average of 0.39 ± 0.11 mSv/y and 228Ra range from 0.50 ± 0.32 to 1.42 ± 0.70 mSv/y with an average of 0.91 ± 0.31 mSv/y. Consequently, the Annual Effective Dose received, as a result of the combined ingestion of 226Ra and 228Ra, was found to range from 0.81 to 1.74 mSv/y with an average of 1.30 mSv/y. The mean contribution of both 226Ra and 228Ra activities to the committed effective dose from a year’s consumption of drinking water in the study area is, therefore, higher than the tolerable level...

Facta Universitatis, Series: Working and Living Environmental Protection, 2021

An effort has been made in this paper to advocate a panacea to the prevailing energy crisis in Ni... more An effort has been made in this paper to advocate a panacea to the prevailing energy crisis in Nigeria by reviewing the country’s geothermal energy resource potential from regional aeromagnetic calculations. There is widespread occurrence of warm/hot springs in Nigeria, which gives credence to the availability and abundance of geothermal reserves. Results of aeromagnetic investigations also confirm that areas with anomalous high heat flow exist in Nigeria, showing high prospects of employing geothermal energy for direct and indirect energy applications. It is, therefore, imperative for Nigeria to take a quantum leap in holistic renewable energy research and development through appropriate government science advice, policy and environmental management.

Summary This paper presents a regional evaluation of depths to top of magnetic sources (DTMS) fro... more Summary This paper presents a regional evaluation of depths to top of magnetic sources (DTMS) from the spectral analysis of the recently acquired high resolution aeromagnetic (HRAM) data of the entire Sokoto Basin in northwestern Nigeria. The basin is bounded by latitudes 10.00 o N and 14.00 o N and longitudes 3.50 o N and 7.00 o E and has a total surface area of about 111,925 km 2 . This work is in view of the Nigerian Federal Government’s encouragement for extensive hydrocarbon exploration in inland basins. The acquired HRAM data was divided into twenty two (22) overlapping blocks and each block analyzed to obtain DTMS values. The results show that the DTMS (also regarded as sedimentary thickness) vary between 0.59 and 2.11 km with an average of 1.22 km. However, the minimum thickness of sediment required to achieve a threshold temperature for the commencement of hydrocarbon formation is 2.3 km. Therefore, hydrocarbon exploration may not be feasible in the basin.

European Journal of Science and Mathematics Education, 2015

This study was designed to investigate the Effect of Polya Problem-Solving Model on Senior School... more This study was designed to investigate the Effect of Polya Problem-Solving Model on Senior School Students’ Performance in Current Electricity. It was a quasi experimental study of non- randomized, non equivalent pre-test post-test control group design. Three research questions were answered and corresponding three research hypotheses were tested in the study. The study was performed in Ilorin metropolis in Kwara State Nigeria, making use of two schools purposively selected. Sixty Senior Secondary School Two students were used in each school, making a total of One hundred and twenty students. The experimental group was exposed to Polya Problem-Solving Model while the control group was exposed to Lecture method. The two groups were pre-tested and post-tested using Performance Test in Current Electricity (PTCE). Data collected after Six weeks were analyzed using mean, standard deviation and analysis of covariance (ANCOVA), the hypotheses were tested at alpha level of 0.05. The finding...

The environmental security and quality of every society are important in the determination of hum... more The environmental security and quality of every society are important in the determination of human development and socioeconomic developments and its level of peace. The potential of environmental security of a location depends on the sustainable management of its forest. This is because of the ecological services being rendered by forest to the environment. Thereby, the societal system will need to encourage forest sustainability and security in order to continue to enjoy its ecological services. Forest utilization and poverty are interlinked, since the level of poverty may contribute to the rate of utilization of forest while the rate of utilization of forest contributes largely to environmental security and quality. The study examines the relationship between the level of poverty to the use of forest and its implication on environmental security using Uganda as a case. There has been a continuous reduction in the size of Uganda's Forest Area (Percentage (%) of Land Area) since 1999. The study interconnects the continuous reduction of the Forest Area (Percentage (%) of Land Area) to the country's well-being and livelihoods and suggests its implications on the environmental security and quality. The study advocates sustainable approaches to the management of forest.

Sokoto Basin in northwestern Nigeria is bounded by latitudes 10.00oN and14.00oN and longitudes 3.... more Sokoto Basin in northwestern Nigeria is bounded by latitudes 10.00oN and14.00oN and longitudes 3.50 oE and 7.00 oE and has a total surface area of about 111,925 km2. This study is in line with the Federal Government of Nigeria’s effort on hydrocarbon exploration in inland basins beyond Niger Delta region of Nigeria for a sustainable economic development in Nigeria. The digital residual data acquired from NGSA covered the entire Sokoto Basin was divided into twenty two (22) overlapping blocks and each block analyzed using spectral (Fourier) centroid method to obtain Regional estimation of depths to top of anomalous magnetic bodies. These depths indicate clearly the magnitude of variations in depth of both the basement topograph and other intrusive in the area , these depths information were subsequently used to generate the contour and the 3D map of the area. An analytic signal method was then used to generate a map on which the amplitude of displayed function is directly and simply ...

Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 2021

Abstract The present study interpreted high-resolution aeromagnetic data using spectral analysis ... more Abstract The present study interpreted high-resolution aeromagnetic data using spectral analysis interpretation technique to carry out a regional estimation of geothermal resources of the entire Benue trough, Nigeria. The data was partitioned into 46 overlapping blocks and the depths to top, bottom and center of the magnetic sources for each overlapping data were computed. The calculated depths were then used to determine curie-point depths, geothermal gradients, and heat flow in the basin subsurface. The geothermal gradient in the study area indicated a range of values from 12.5 to 38.3 °C/km with a mean value of 26.0 °C/km, while the curie-point depths vary from 15.0 to 45.3 km with a mean depth of 23.2 km. The study identified four separate geothermal zones namely A, B, D, and F. However, zone F before this study has been unknown. It, therefore, represents an additional geothermal zone to the previous works in the study area. The values of heat flow vary from 31.2 to 95.8 mW m −2 with a mean value of 65.1 mW m −2 . This study provides new insights into the geothermal resources of the Benue trough. The high heat flow values in the entire region might be considered good for geothermal exploration and therefore, the geothermal zones identified should be considered for further investigations. Article Highlights The study identified four separate geothermal zones: A, B, D, and F. The geothermal zone F before this study has been unknown. It provides new insights into the geothermal resources of the Benue trough.

Journal of Applied Sciences and Environmental Management, 2019

In this research paper, the sub-surface heat flow of a part of the Chad Basin, in North eastern N... more In this research paper, the sub-surface heat flow of a part of the Chad Basin, in North eastern Nigerian was estimated using spectral analysis. This was obtained from twenty (20) digitized High Resolution Aeromagnetic (HRAM) data sheet covering the study area. Regional-residual separation using first order polynomial fitting method with three coefficients was carried out on the data map before the application of statistical spectral analysis. Result shows that the centroid depth varies between 9.39 km and 18.31 km. The depth to the Curie temperature isotherm varies between 15.14 km and 33.46 km below the mean sea level. It was also found that the Curie temperature isotherm within the basin is not a horizontal level surface but an undulating surface with geothermal gradients and heat flow ranging between 15.77 and 38.31˚C/Km, and 39.41 and 95.77 respectively. Thus, the calculated average geothermal gradient and heat flow for this area are 23.39˚C/Km and 58.47 respectively. Since average heat flow in thermally normal continental region is 60 and the values in excess of 80-100 are associated with anomalous geothermal conditions, hence the study area can generally be considered as a thermally normal region. But, the northeastern part of the study area with values in excess of 80 is recommended for further investigation.

Geothermal Energy Science, 2017

A regional estimation of Curie-point depths (CPDs) and succeeding geothermal gradients and subsur... more A regional estimation of Curie-point depths (CPDs) and succeeding geothermal gradients and subsurface crustal heat flow has been carried out from the spectral centroid analysis of the recently acquired highresolution aeromagnetic (HRAM) data of the entire Bida Basin in north-central Nigeria. The HRAM data were divided into 28 overlapping blocks, and each block was analysed to obtain depths to the top, centroid, and bottom of the magnetic sources. The depth values were then used to assess the CPD, geothermal gradient, and subsurface crustal heat flow in the basin. The result shows that the CPD varies between 15.57 and 29.62 km with an average of 21.65 km, the geothermal gradient varies between 19.58 and 37.25 • C km −1 with an average of 27.25 • C km −1 , and the crustal heat flow varies between 48.41 and 93.12 mW m −2 with an average of 68.80 mW m −2. Geodynamic processes are mainly controlled by the thermal structure of the Earth's crust; therefore this study is important for appraisal of the geo-processes, rheology, and understanding of the heat flow variations in the Bida Basin, north-central Nigeria.

Geothermics, 2015

An estimate of depths to the bottom of magnetic sources (DBMS) in the upper part of Sokoto Basin,... more An estimate of depths to the bottom of magnetic sources (DBMS) in the upper part of Sokoto Basin, northwest Nigeria has been made from the modified centroid method based on a fractal source distribution of magnetic sources and spectral analysis of aeromagnetic data. DBMS is used as an estimate of the Curiepoint depth and hence a proxy for temperature at depth. Aeromagnetic maps covering an area bounded by latitudes 12.5 • N and 13.5 • N and longitudes 4.0 • E and 6.0 • E were digitized at an equal spacing of 1 km. Six profiles were subsequently mapped out on the magnetic data covering different geological parts for the purpose of spectral centroid analysis. The result shows that the DBMS varies between 11.37 km and 28.18 km. Consequently, geothermal gradient varies between 20.58 • C/km and 51.02 • C/km, while the ensuing heat flows vary between 51.45 mW/m 2 and 127.55 mW/m 2. The thermal structure of the earth's crust is one of the main parameters controlling geodynamic processes. This study is crucial for quantitative understanding of the geo-processes and rheological/rock-physics parameters in the study area.

Facta Universitatis Series Working and Living Environmental Protection, Oct 17, 2014

An assessment of the natural radioactivity in sachet drinking-water samples in Ilorin, Nigeria ha... more An assessment of the natural radioactivity in sachet drinking-water samples in Ilorin, Nigeria has been carried out. Gamma-ray spectroscopic analysis of the samples revealed the presence of 40 K, 226 Ra and 228 Ra radionuclides in high proportions. The activity concentration values range from 174.20 ± 34.19 to 376.02 ± 65.03 Bq l-1 , 9.36±2.87 to 22.52±6.20 Bq l-1 and 9.85±3.88 to 23.88±7.47 Bq l-1 for 40 K, 226 Ra and 228 Ra respectively. The derived annual effective dose received by the population as a result of the ingestion of 40 K was found to range from 0.39±0.08 to 0.85±0.15 mSv y-1 , 0.96±0.38 to 2.30±0.63 mSv y-1 for 226 Ra and 2.48±0.98 to 6.01±1.88 mSv y-1 for 228 Ra. Consequently, the effective dose received as a result of the combined ingestion of 226 Ra and 228 Ra was found to range from 1.27 to 2.32 mSv y-1. These contributions of both 226 Ra and 228 Ra activities to the committed effective dose from a year's consumption of the drinking-water are higher than the tolerable level of 1 mSv y-1 to the general public for prolonged exposure as recommended by ICRP, and much more than WHO's recommended level of 0.1 mSv y-1 for drinking-water. Therefore, it is strongly recommended that calculated efforts should be made by relevant regulatory authorities in Nigeria to protect the populace from adverse radiological health implications.

Journal of Volcanology and Geothermal Research, 2015

Evaluation of Curie-point depths, geothermal gradients and nearsurface heat flow from high-resolu... more Evaluation of Curie-point depths, geothermal gradients and nearsurface heat flow from high-resolution aeromagnetic (HRAM) data of the entire Sokoto Basin, Nigeria