Gongola Basin Crust-Mantle Structural Analysis For Hydrocarbon Investigation Using Isostatic Residual Gravity Anomalies

The isostatic residual gravity anomaly data of Gongola basin was computed by removing from the Bouguer gravity anomaly field, a regional gravity field calculated for compensation of masses of surface topography. The regional gravity field was computed using the Airy-Heiskanen isostacy model with compensation at the crust-mantle discontinuity. The free air, residual isostatic anomaly, density distribution maps and 2.5D gravity models were utilized in the definition of the basin’s crust-mantle structures. Results showed that: (1) the free air anomaly depicted the edge effect anomaly which correlates with the slope and rise at the NE zone. (2) The isostatic residual anomaly showed three zones: the overcompensated (NE-SE), undercompensated (NW-SW) while the hydrostatic equilibrium zone was found to be the transition between the undercompensated and the overcompensated zones. The distribution of rock densities within the exposed crust is not unimodal. The main component is the granodioritic ones 2.65 - 2.72g / cm3 consisting of plutonic rocks. The granitic component 2.60 - 2.64g / cm3 is common within the subsurface. The high velocities (6.2km/ s) and the modeled high densities from 2.78 - 2.83g / cm3 suggest that the materials comprises high-grade metamorphic mafic intrusive and volcanic rocks. (3) The change in the crustal thickness along the profiles due to intra sediment and basement intrusive provide a measure of the amount of heating that occurred during rifting. Thus, the gravity across the rift system is found to be due to upwelling of low density hot materials which has also affected the hydrocarbon in place. (4) The crustal thickness together with the depositional architecture (e.g. porosity and permeability) should be used to determine the subsurface fluid circulation in terms of hydrocarbon exploration within the rifted basin. The intrusives are potential targets for solid minerals.Key word: Bouguer, Airy Heiskanen model, isostatic residual, free air, isostatic regional gravity, 2.5D gravity model

Groundwater potential mapping in Ikorodu, Lagos State, Nigeria, using multi-criteria analysis and hydrogeophysics

The assessment of the potential groundwater recharge area is extremely important for water quality protection and proper management of ground water systems. The objective of this study was to evaluate systematic groundwater studies using the integration of remote sensing and geographic information systems (GIS) and hydrogeophysics as a tool to identify groundwater potential areas in Ikorodu, Lagos. In this study, various thematic maps (layers) derived from satellite image classification such as: Land use/ Land cover map, soil map, rainfall map, geological map, slope map derived from SRTM Digital Elevation Model, lineament density map obtained as a result if lineament analysis of the principal component of the image, were all integrated using the weighted overlay tool in the spatial analyst toolbox of ArcGIS 10.5. Ranks and weights of classes and sub-classes of the thematic layers were assigned based on their influences on groundwater occurrence. The vertical electrical sounding data obtained from the study area were used to validate the results of the groundwater potential map and also determine the areas with brackish water, saline water and freshwater and the most probable drillable depth for exploration. The results show that the groundwater potential zones of the study area could be classified into five zones with the following percentage for spatial distribution: “very high” potential zone (0.6%), “high” (4.2%), “moderate” (15.8%), “low” 71.7% and very low potential zone (7.7%). The South-Western region of Ikorodu, close to Oriwu has the highest concentration of groundwater. Imota is characterized with Moderate and Low ground water potentials. From the query results, the aquiferous layers were identified, their yield and potentials determined and the depths to which boreholes can be sunk for the drilling of fresh water were found to be between 20m and 120m respectively. Keywords: Groundwater, Remote sensing, GIS, Hydrogeophysics

Gravity Inversion of the Gongola Basin Fault Structures Using the Step Model

Gravity anomalies with step-like appearance are often attributed to fault structures. Analysis of gravity anomalies due to such structures is then tantamount to solving the four fault parameters: depth to the surface, sediment thickness, density contrast and the fault dip. In this research, a gravity inversion using the step model was carried out to simultaneously estimate the four parameters of the faulted bed. The model assumes a configuration that the basin is filled with homogeneous sediments. Three characteristic curves were adopted for estimating the fault parameters.Analysis of the residual anomaly profiles of the fault structures showed that the fault structures were independent of the strike length. The estimated depth to the surface and the sediment thickness yielded the basement depth. The basement depth obtained from the gravity profiles showed a maximum basement depth of 1.0 km in the south-western part, and 7.0 km in the north-eastern part of the project area. The estimated basement depth yielded plausible geological model that corroborates with depth obtained using seismic and well information. The computed density contrast was used in the determination of density contrast and rock density maps of the basin. This helped in defining the basin into zones of sedimentary, basement complex and granite pluton

Modeling Malaria Prevalence Rate in Lagos State Using Multivariate Environmental Variations

The aim of this research is to establish the significant effect of environmental factors on malaria prevalence rate within the Local Government Areas of Lagos State. The methodology used was to carry out a statistical analysis of these various environmental factors with the malaria prevalence cases that was recorded in Lagos State using a 5 years data from 2009-2013 of malaria prevalence cases recorded with environmental data for the same time frame, and to further use GIS to show the various Local Government Areas with high severe malaria cases as well as low malaria cases. The result obtained from this analysis shows a significant relationship between the malaria prevalence cases and environmental factors of rainfall, temperature and relative humidity, this helped in developing a predictive model. The outcome from this research work can help the government, Lagos State Ministry of Health and donor agencies both local and international see the Local Government Areas within the state that are most vulnerable to malaria epidemic, and further aid them in policy formation, planning and strategy implementation

Modeling Malaria Prevalence Rate in Lagos State Using Multivariate Environmental Variations

ABSTRACTThe aim of this research is to establish the significant effect of environmental factors on malaria prevalence rate within the Local Government Areas of Lagos State. The methodology used was to carry out a statistical analysis of these various environmental factors with the malaria prevalence cases that was recorded in Lagos State using a 5 years data from 2009-2013 of malaria prevalence cases recorded with environmental data for the same time frame, and to further use GIS to show the various Local Government Areas with high severe malaria cases as well as low malaria cases. The result obtained from this analysis shows a significant relationship between the malaria prevalence cases and environmental factors of rainfall, temperature and relative humidity, this helped in developing a predictive model. The outcome from this research work can help the government, Lagos State Ministry of Health and donor agencies both local and international see the Local Government Areas within the state that are most vulnerable to malaria epidemic, and further aid them in policy formation, planning and strategy implementation.</p

Extraction of lineaments and faults using gravity second horizontal derivative data obtained using Fourier transform

Linear anomalies are important in the interpretation of gravity data because they indicate some important structural features. Gravity anomalies obtained from horizontal derivatives generally reflect lineaments and faults or compositional changes which can describe structural trends of a region. This study involves the delineation of the Gongola basin structural trend based on the convolution between the Fourier kernel obtained from the second horizontal derivative (SHD) of the truncated horizontal plate model (THPM) and the gravity anomaly.Линейные аномалии важны для интерпретации гравитационных данных, поскольку они являются индикаторами некоторых важных структурных особенностей. Крутые градиенты горизонтальных производных гравитационного поля обычно отражают линеаменты и разломы или изменения состава, позволяет описывать структурные тенденции региона. Это исследование направлено на выяснение структурного тренда бассейна Гонгола и основывается на конволюции ядра Фурье второй горизонтальной производной (ДГП) усеченной модели горизонтального слоя и аномалии гравитационного поля.Лінійні аномалії важливі для інтерпретації гравітаційних даних, оскільки вони є індикаторами деяких важливих структурних особливостей. Круті градієнти горизонтальних похідних гравітаційного поля зазвичай відображають лінеаменти і розломи або зміни складу, що дає змогу описувати структурні тенденції регіону. Це дослідження спрямоване на з’ясування структурного тренду басейну Гонгола і ґрунтується на конволюції ядра Фур’є другої горизонтальної похідної (ДГП) усіченої моделі горизонтального шару і аномалії гравітаційного поля