Study on the Groundwater Accumulation of Oke-Ogba Area using Groundmagnetic Survey

A ground magnetic survey of Oke-Ogba area in Akure part of south western Nigeria was carried out with the aim of establishing dominant hydrogeologic factors responsible for groundwater development of the area. A total of four transverses were established for the groundmagnetic survey, and the results were presented as groundmagnetic profiles of varying magnetic intensities. The  basement topography was obtained from the profiles using half-width method. The interpretation of magnetic intensities of the profiles revealed a network of geological features such as faults, joints and fractures. The high magnetic intensity at the central portion of the constructed magnetic contour map indicates shallow basement. This was corroborated with quantitatively  interpreted result which established overburden thickness to the top of the magnetic basement rock as varied between 3.0 and 21.0m. Groundmagnetic study of Oke-Ogba area has revealed the efficacy of magnetic prospecting technique as a fast reconnaissance tool for identifying geological features and estimation of basement depth. The study has established geological features as more prominent hydrogeologic indicator for groundwater development in the area. @ JASEMJ. Appl. Sci. Environ. Manage. December, 2010, Vol. 14 (4) 25 - 3

Groundwater Prospecting and Exploration in a Low Potential Hard Rock Aquifer: Case Study from Ogbomoso North, South-western Nigeria

Very Low Frequency Electromagnetic (VLF-EM) and Electrical Resistivity methods has been employed to unravel the localized nature of groundwater occurrence in Ogbomoso North, southwestern Nigeria. This was aimed at addressing the growing demand for groundwater use in the area underlain by migmatite gneiss with minor intrusions of pegmatite and quartz veins. Nine profiles comprising five VLF-EM and four electrical resistivity profiles were conducted parallel to the two major azimuths in the area.  The anomalous zones identified on the profiles were further investigated by twelve Vertical Electrical Soundings (VES). Lithologic logs from three boreholes were also used to ground truth the geophysical findings. Quantitative interpretation of VES data showed that the Geoelectrical Succession comprise three to five layer earth models. The aquifer units are localized comprising weathered layer and fractured basement. The lowest yield of 280.6LPH was obtained from well bored on VES point having three-layer earth models made up of resistive-conductive-resistive geoelectric succession. Well bored on VES points having more than three-layer earth models and comprising alternating band of resistive-conductive geoelectric succession have more yield ranging between 520.8LPH and 590.4LPH.  Furthermore, there was strong correlation between geoelectric succession and lithologic sections obtained from the drill cuttings of the bored wells. Keywords: Groundwater Exploration, Geophysical Methods, Lithology Logs, Fractured Basement, Crystalline Rocks

Reservoir characterization and seal integrity of Jemir field in Niger Delta, Nigeria

Ignoring fault seal and depending solely on reservoir parameters and estimated hydrocarbon contacts can lead to extremely unequal division of reserves especially in oil fields dominated by structural traps where faults play an important role in trapping of hydrocarbons. These faults may be sealing or as conduit to fluid flow. In this study; three-dimensional seismic and well log data has been used to characterize the reservoirs and investigate the seal integrity of fault plane trending NW-SE and dip towards south in Jemir field, Niger-Delta for enhanced oil recovery. The petrophysical and volumetric analysis of the six reservoirs that were mapped as well as structural interpretation of the faults were done both qualitatively and quantitatively. In order to know the sealing potential of individual hydrocarbon bearing sand, horizonefault intersection was done, volume of shale was determined, thickness of individual bed was estimated, and quality control involving throw analysis was done. Shale Gouge Ratio (SGR) and Hydrocarbon Column Height (HCH) (supportable and structure-supported) were also determined to assess the seal integrity of the faults in Jemir field. The petrophysical analysis indicated the porosity of traps on Jemir field ranged from 0.20 to 0.29 and the volumetric analyses showed that the Stock Tank Original Oil in Place varied between 5.5 and 173.4 Mbbl. The SGR ranged from leaking (60%) fault plane suggesting poor to moderate sealing. The supportable HCH of Jemir field ranged from 98.3 to 446.2 m while its Structure-supported HCH ranged from 12.1 to 101.7 m. The porosities of Jemir field are good enough for hydrocarbon production as exemplified by its oil reserve estimates. However, improper sealing of the fault plane might enhance hydrocarbon leakage

Investigation of subsurface Geologic Features in Low latitude Crystalline Basement Complex: case study of Oke-Alapata Area, Ogbomoso, South-western Nigeria

Ground Magnetic survey has been carried out to investigate subsurface geology of Oke-Alapata area of Ogbomoso, Southwestern Nigeria. Magnetic measurements were recorded using proton precession magnetometer. The objectives of the research include determination of depth to magnetic source, investigation of subsurface reliefs and magnetic anomalies signatures associated with geological features such as joints, fractures and lithologic contacts as well as update the geology of the area. The ground magnetic survey was preceded by geological mapping of the area. A total of ten profile lines were traversed in an east-west direction with an inter-profile spacing of 100m and station interval of 5m. The magnetic data obtained were processed and plotted on profiles to obtain the magnetic signatures of the subsurface.  The data were subsequently interpreted qualitatively and quantitatively. The geological mapping revealed the presence of migmatite-gneiss and quartzite at the northern and southeastern part respectively of the study area. The magnetic anomalies ranged from minimum negative peak value of -400nT to maximum peak value of 520nT. The detected geological features include joints and fractures as well as rock-rock contact between Migmatite-gneiss and quartzite. The depth to magnetic source ranged from 6.1m at the southeastern part to 10.8m at the northeastern part of the study area. The strong correlation between the geological map of Oke Alapata, the identified geologic features and the magnetic anomalies interpretations has exemplified the use of magnetic anomalies signatures in characterizing geologic features in a low latitude crystalline basement complex studied. Keywords: Ground Magnetic Survey, Subsurface Geology, Joints, Fractures, Rock-Rock contact, Ogbomoso, Nigeri

Geophysical investigation of abandoned back-filled railway line: implication on adjacent buildings

A geophysical investigation was carried out on a back-filled segment of an abandoned railway route at Okebadan Estate, Ibadan using electrical resistivity imaging. The study is aimed at depicting the cause(s) of settlement that led to building foundation failure. Five profile lines were established during the study and the apparent resistivity values obtained from the traverse were plotted against the mid-point of electrode separation using least-squares inversion algorithm. Pockets of low resistivity region were obtained from the inverted sections with resistivity values ranging from 77 Ω-m to ˂400 Ω-m. The suspected back-filled earth materials were suspected to be clay and clayey sand. Results indicated that materials used in back filling the abandoned rail route were not well compacted. Consequently, the structural failure of buildings along this abandoned route was attributed to differential settlements of clays and clayey sands on which they were erected.Keywords: Backfill, Foundation, Resistivity, Settlemen

Geomagnetic Signature Pattern Of Industrial Layout Orile Igbon

Ground magnetic data at Industrial Layout Orile Igbon was analyzed with a view to determining the areas that are competent for the construction of factories and other related buildings (e.g. high-rise administrative buildings). The study area falls within latitude 080 13′ 59.22″ to 080 15′ 0″ North and longitude 0040 17′ 05.0″ to longitude 0040 19′ 01.1″ East of Southwestern Nigeria. The ground magnetic survey was carried out, the acquired data was processed and analyzed. The qualitative interpretation revealed features like faults, contact between two rocks and fracture zones. However, the quantitative interpretation gave the overburden thickness to the top of the magnetic basement rock as varied between 6.0 and 33.5 m. Interpretation of ground magnetic data revealed that Industrial Layout Orile Igbon comprise of zones underlain with thin as well as thick overburden. It is therefore advisable that people should not ignorantly built factories making use of heavy machines where there is thick overburden as it might lead to subsidence or total collapse in the future. This could occur when the vibration of these heavy machines is transferred to the subsurface which might lead to ground motion which later has effect on the factory’s foundatio

Effect of Open Dumpsite on Undeground Water in Ganmo,Ifelodun LGA, Kwara State, North Central Nigeria.

This study imbibes Geophysical survey involving electrical resistivity methods (Electrical Re- sistivity Tomography and Vertical Electrical Sounding), Physico-chemical analysis and Bacte- ria Analysis of the underground water samples. Geophysical survey were conducted around a 35 years old solid waste dumpsite in Ganmo, one of the districts in Ifelodun LGA, Kwara State, North Central Nigeria, located between latitude 8�2502500 to 8�2504100N and longitude 4�3603600 to 4�3606200E, with the view to assessing the extent of impact of the waste dumpsite on the quality of the groundwater in the study area. Electrical Resistivity Pro�ling and vertical elec- trical sounding stations were established using Werner and Schlumberger con�guration with half { currents electrode spacing that ranged from 1 to 100 m. A digital read out resistivity meter was used to acquire data in the area. A contaminant leachate plume was delineated in 2-D resistivity sections as low resistivity zones. The 2-D resistivity imaging was identi�ed as bluish zones of low resistivity 20.9 m with the depth ranging from 0.25 to 3.96 m in the entire inverse model sections. The low resistivity value of 20.9 m revealed that the groundwater around the dumpsite has been contaminated to the depth of 3.19 m compare to the measured water levels. The VES results were presented in terms of resistivity, thickness and depth. The VES interpreted results delineated three subsurface layers comprising topsoil, weathered layer and the fresh basement of which the three (3) layer geo-electric sections are both H-type and A-type sounding curve. The result indicated that the 3rd layer VES has high resistivity value ranging from 650.0 to 2264.3 m whose depth and thickness could not be reached. Three (3) water samples were collected, two samples from the closest hand dug wells and one sample from bore-hole for analysis. The hydro-physicochemical analysis conducted showed that wells are in good conditions actually the concentration of various parameters tested are below the WHO and FEPA standard. The result of the bacterial analysis of the water samples collected showed presence of bacterial species load of E. coli and Klebsiella which can cause severe health hazards. It is concluded that the water is not safe for domestic consumption. However water treatment is hereby recommended on all wells around the study area

Reservoir characterization and by-passed pay analysis of philus field in Niger delta, Nigeria

Hydrocarbon resources have become the most essential commodity contributing to any nation’s growth and development in the recent years. For the past decades now, the quest for hydrocarbon resources has been increasing in an arithmetic rate that its supply can no long-er meets the demand for its consumption today. In petroleum industry, seismic and well log analyses play a vital role in oil and gas ex-ploration and formation evaluation. This study is aimed to effectively characterize the reservoirs and analyze the by-passed pay in Philus Field, Niger-Delta, Nigeria in order to look into the economic viability and profitability of the volume of oil in the identified reservoir(s). The faults in the study area trend in NW-SE direction and dip towards the south. Seven reservoirs were mapped on Philus field. A dis-covery trap and a by-passed (new prospect) trap were mapped out on the field. The petrophysical analysis showed that porosity of Philus field was 0.24. The volumetric analysis showed that the Stock Tank Original Oil in Place of discovery trap (Philus field) ranged from 1.6 to 43.1 Mbbl while that of new prospect trap ranged from 18.1 to 211.3 Mbbl. It is recommended that the oil reserve of Philus field needs to be recalculate

Geoexploration of radioelement'sdatasets in a flood plain of crystal linebedrock

The datainthisarticlecontainsstatisticalanalysisofradioelement in Odo-Oba flood plainofcrystallinebedrock,Southwestern Nigeria. Thedatawereacquiredalongtwenty-twotraverses.The length ofeachtraverseisafunctionofitsaccessibilityinthestudy area. Thetraversescoveredtheareausedforagriculturalpractices and theareawherethesefarmproductsarebeingsoldtoeither the retailersortheconsumers.Descriptiveandmultivariatesta- tistical analyseswereusedtoexplorethemeasuredemitted gamma radiationinOdo-Oba flood plain.Thedatasetcanprovide insights intotherisksinvolvedinexposuretooutdoorradiationin a commercialcentrewhentheaverageoutdoorgammaradiation levels arecomparedtotheglobalthresholdvaluesfromthereg- ulatory bodiessuchasWorldHealthOrganization,National ResearchCouncil,UnitedStatesEnvironmentalProtectionAgency, FederalEnvironmentalProtectionAgency,InternationalCommis- sion onRadiologicalProtection,theUnitedNationsScientific Committee ontheEffectsofAtomicRadiation,andFederalRadia- tion ProtectionServiceamongother

Investigation into the types of fracture and viable depth to substratum of a housing estate using geophysical techniques

Mapping of the configuration of bedrock is paramount in civil engineering and hydrogeological settings. In civil engineering, areas that are extensively fractured (either shallow or deep) are adjudged as weak zones whereby these provinces are regarded as copious zones for groundwater exploration. Very Low Frequency Electromagnetic (VLF-EM) and ground magnetic survey were carried out in Olupona Housing Estate along seven traverses with interstation spacing of 20 m. For the two methods, traverses 1 to 3 were taken in North-South azimuth which covered distance 300 m while traverses 4 to 7 were acquired along East-West azimuth which covered distance 400 m. VLF-EM results revealed Type-1 fracture along traverse 1, traverses 2 to 4 showed no fracture but a fairly competent bedrock. Type-2 fractures were revealed on traverses 5 to 7 while Type-3 fracture was shown on traverse 5 alone. Ground magnetic results depicted that the depths to biotite or biotite muscovite granite are relatively deep. The mineral rocks with very thin, intermediate, and very thick bodies have their depths range as 14.7 m, 11.0 m and 8.8 m respectively. On the average, the depths to these mineral rocks from the surface varied from 6.5 to 19.6 m. The trends of the identified fractured zones are NE-SW and NW-SE directions. It is concluded that in order to avoid building collapse in future, construction of high-rise buildings is unadvisable in the study area. If the identified fractured zones are properly maximized for groundwater exploration, the fractured zones can be optimized such that reservoir(s) can be constructed so as to supply water to the houses for domestic usage