Physics -Scholarly Publications
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- ItemOpen AccessRock type based Poroperm and Continuous Predictions in a Tight Gas Formation(Faculty of Science, Obafemi Awolowo University, Ile-Ife, 2018) Ojo, S.A; Olatinsu, O.B; Ozebo, V.C.Porosity from log response such as density provides a continuous representation of pore volume as function of depth in a well, which can be calibrated with core analysis data. Obtaining a continuous log of permeability is not as straightforward as there is yet no means of logging permeability. While DST-derived permeability values are useful in calibrating dynamic models, they only represent an average value over the radius investigated by the test and will not readily correlate to permeability values derived from core especially where there are lateral and vertical permeability variations within the reservoir. It is, however, possible to obtain a depth-continuous permeability estimate by deriving a free regression algorithm known as the poroperm transform function, which defines how the permeability varies as a function of porosity. Such correlations are typically derived empirically from overburden corrected core-derived porosity and permeability data. General porosity-permeability trends are far too scattered to be of use. However, far tighter porosity-permeability trends can be obtained by use of rock typing to identify suitable analogues. The following study highlights how microstructural rock-tying can be used to improve permeability prediction in a set of tight gas sandstone wells. Scanning electron microscopy (SEM) and quantitative X-ray diffraction (QXRD) data were obtained from >200 tight gas sandstone samples from the Southern North Sea for which porosity and permeability measurements had previously been conducted. The SEM and QXRD data were used to derive microstructural and mineralogical rock types respectively. Samples from each rock-types occupy different but overlapping positions on porosity-permeability cross plots. Exponential functions were fitted to porosity-permeability data for each rock type and then applied to the porosity values from wire-line log data to derive continuous permeability estimates. The log porosity curves-being the independent variables of the respective functions, were validated by core observation to avoid error propagation. Continuous permeability curves that honour mineralogical variation were obtained by the use of microstructural rock typing.
- ItemOpen AccessIdentification of depth to top of limestone body within a concession at Ibese, Southwestern Nigeria, using vertical electric sounding(Medwell Publications, 2008) Ozebo, V.C.; Odunaike, R.K; Balogun, A.Ahe depth to top of limestone body within a concession at Ibese, in Ogun state, Southwestern Nigeria was evaluated using the Vertical Electric Sounding (VES). The electrical resistivity method employing the VES technique was used to carry out the geophysical investigation and a total 10 VES data was acquired. Three curve types were identified from the acquired data which are the H, A and HK-type curves. Also a geo-electric section was obtained from the result of the field sounding areas, where all the materials above the limestone is regarded as an overburden. The study area (line) spans 5 km of which the trend (direction) of the limestone was found to be NW-SE. VES locations 2, 5, 6, 7, 8 were found to have a shallow depth which is less than 6 m and can be said to be of economic importance.
- ItemOpen AccessRadiation Exposure to Workers and Villagers in and Around Some Quarry Sites in Ogun State of Nigeria(Medwell Publications, 2008) Odunaike, R.K; Ozebo, V.C.; Alausa, S.K; Alausa, I.MIn this research, the authors employed radiation detection methods to examine the radiation intensity or exposure at 5 quarry sites and their respective neighborhood villages in Ogun State of Nigeria. The highest annual dose rate or exposure of 49.1 micro Sv year 1 was recorded at Equation Limited (Q3) in Obafemi Owode Local Government area in Ogun State of Nigeria. However, this result (49.1 micro Sv year 1) and others from the remaining locations or sites are smaller than the world average of 70 micro Sv year 1 but recommended that workers at quarry sites should always put on masks to eliminate or reduce the amount of radioactive inhalation. Regular comprehensive monitoring of radiation level of each worker by putting on Thermo Luminescent Dosimeters (TLDs) which could be read and interpreted must be encouraged.
- ItemOpen AccessMathematical Model to Predict Conductive Properties of Contaminated Riverbed sand in Ado Odo Ota Local Government Area of Ogun State(Canadian Centre of Science and Education, 2012) Akinyemi, O.D; Rabiu, J.A; Ozebo, V.C.; Idowu, O.AThe possibility of contamination is especially rising due to the increase in the number of industries in the Local Government Area. In this study, riverbed sands were collected from five major rivers in Ado-Odo Ota Local Government Area, and conductivity properties were determined after the samples have been treated with varying concentration of petrol, engine oil, diesel, caustic soda and H2SO4. HANNAN Electrical Conductivity Meter, KD2 Thermal Conductivity Meter and Constant Head Method were used to determine the electrical, thermal and hydraulic conductivities respectively. A mathematical model was developed that describes the effect of contaminants on the electrical (σ), thermal (λ) and hydraulic (k) conductivities of riverbed sand from the major rivers in Ado-odo Ota Local Government Area. The model equation incorporates the bulk density of the riverbed sand samples, as well as the concentration and conductivity of the contaminants as follows: = 0.107x1+ 0.10x2 – 0.017x3 + 1.673, = 1.911x1 + 18.229x2 – 0.015x3 + 47.173 and k = 0.056x1 + 0.381x2 – 0.031x3 + 0.162, where x1, x2 and x3 are bulk density of samples, conductivity and concentration of contaminants respectively. From interpolation analysis, sample from Ilogbo river contained about 30 ml/kg of engine oil, Mosafejo river contained about 10 ml/kg of caustic soda, Ijako river contained about 20 ml/kg of caustic soda, Iju river contained about 10 ml/kg of diesel and Igbogbo river contained 10 ml/kg of H2SO4, thus showing clearly how waste products from industries end up as contaminants in nearby rivers.
- ItemOpen AccessGroundwater Assessment in Apapa Coast-Line Area of Lagos using Electrical Resistivity method(Scholarlink Research Institute, UK, 2011) Ozebo, V.C.; Ajiroba, S.OA study was conducted on some physical characteristics of geological formations in Apapa, a coast-line area of Lagos state with the purpose of determining the extent of deterioration in the quality and quantity of the groundwater due to saline water intrusion and other factors. Applying the Schlumberger configuration of Vertical electrical sounding, (VES) on five locations, data were collected and analysed using both the partial curve matching and microprocessor iterative techniques. Geoelectric sections along XX – XX’, comprising of VES point 3 and 1, and along YY – YY’ made up of VES points 1 and 4 were generated along south-north and West-East directions respectively. The analysed data revealed the presence of sand, clay, sandy clay, clayey sand formations and some intrusions of saline water in the area. The results also indicated that the safest depth for groundwater (devoid of saline intrusion) is 34 m and beyond.