Papers by Kenneth Okiongbo
Research Journal of Environmental and Earth Sciences, 2019
Hydrochemical investigation of groundwater samples was carried out in Yenagoa, Southern Nigeria i... more Hydrochemical investigation of groundwater samples was carried out in Yenagoa, Southern Nigeria in an attempt to determine the suitability of the groundwater quality for domestic use. Twenty four groundwater samples were collected from domestic boreholes in the study area and were analyzed for major ions. The hydrochemical parameters determined were statistically examined and correlated. Factor analysis was applied to extract the principal factors responsible for the variation in the hydrochemistry. Water Quality Index (WQI) rating was calculated to quantify overall suitability of the water for human consumption. The results show that the correlation coefficient matrix between Electrical Conductivity (EC), Na + and Cl -was significant, which is an indication of seawater influence on the groundwater quality. The geochemistry of the groundwater is controlled mainly by rockwater interaction, ion exchange reactions, reductive dissolution of iron bearing minerals and weathering of silicate group of minerals. The WQI of the study area ranged from 5.7-32.7, indicating excellent water quality.
Ife Journal of Science, 2015
In an attempt to establish empirical electric-hydraulic relationships for the purpose of analyzin... more In an attempt to establish empirical electric-hydraulic relationships for the purpose of analyzing surface resistivity soundings, geoelectrical soundings using the Schlumberger array were carried out in Yenagoa and environs. Fourteen (14) VES stations were occupied across the study area. The field data were interpreted using Interpex IX1D computer software and the aquifer resistivity (ρ) at each location was estimated. The hydraulic conductivity (K) determined from a reference borehole was combined with the normalized electrical conductivity (σ') to estimate a constant K σ'. This constant was integrated with the Dar Zarrouk parameters and used to estimate the hydraulic conductivity and transmissivity values at other VES locations where K values were unknown. The results showed that the hydraulic conductivity varied from 11.3 – 120.9 m/day while the transmissivity varied from 218.8 – 2849.9 m 2 /day. Correlation of geoelectric and hydraulic parameters of the aquifer showed th...
This manuscript aims to figure out shallow channels and their infill lithology in the Southern No... more This manuscript aims to figure out shallow channels and their infill lithology in the Southern North Sea using a 3D seismic data. The authors applied nonlinear spectral decomposition methods and found the distinct low sinuosity channel and its lithological characteristics. Since I am not a specialist in lithological and solid geophysical fields, I reviewed the manuscript from a view point of the general data and geophysical science. I carefully read the manuscript and concluded that this manuscript is not among the scope of the Nonlinear Processes in Geophysics (NPG); therefore, I would like to C1
Geoelectrical sounding method was adopted in the evaluation of aquifer protective capacity and co... more Geoelectrical sounding method was adopted in the evaluation of aquifer protective capacity and corrosivity of near surface materials in Yenagoa city, South South, Nigeria. A total of eleven Vertical Electrical Soundings (VES) stations were occupied using the Schlumberger configuration. Five geoelectric layers were identified. Layers four and five are the likely aquiferous horizons with resistivities >280 Sm. The depth to the aquiferous horizon varied between 6.0-52.0 m, and has a rather irregular distribution and thickness. Corrosivity, isopach and longitudinal unit conductance (S) maps were generated from the combination of first and second order geoelectric parameters. The results indicate that the INC and Opolo areas of the city are characterized by weak protective capacity (0.1-0.2 mhos) while other locations investigated are underlain by materials which could be regarded as moderate (0.2-0.69 mhos) to good (0.7-4.9 mhos) protective capacity. Resistivity values within the sec...
In the Southern North Sea, 3D seismic data had been widely acquired to explore for hydrocarbons, ... more In the Southern North Sea, 3D seismic data had been widely acquired to explore for hydrocarbons, but interpretations of these datasets until now focus mainly on the deep exploration targets of the petroleum companies. Less attention is given to shallow sediments. But these sediments often contain channels that can serve as potential reservoir units. Thus the mapping and identification of these shallow channels and defining their infill lithology is important. In this study, seismic spectral decomposition technique has been used to delineate shallow thin channel geometry in a 3D seismic data acquired in the Dutch sector of the North Sea. The concurrent interpretation of curvature and coherence cubes with seismic facies analysis based on reflection terminations and geometry, amplitude and continuity enables the discrimination between shale versus sand filled channels. The results of the spectral decomposition show two distinct low sinuosity channel features in NNE-SSW direction but becomes diffuse towards the North. The strong negative curvature anomaly along the channels's axes observed in the most negative curvature attribute implies that the sediments within the channels have undergone more compaction. These strong negative curvature anomalies are interpreted to be due to differential compaction of shale filled channels.
SSRN Electronic Journal, 2018
Land surface subsidence and reservoir compaction due to fluid withdrawal has created a great inte... more Land surface subsidence and reservoir compaction due to fluid withdrawal has created a great interest due to its relevance in gas, oil and groundwater extraction. One serious problem associated with petroleum production is ground subsidence resulting from reservoir compaction (Greetsma, 1973). In Po River delta around Venice, the subsidence rate measured between 1968 and 1969 had increased from its low historic rate to 1.7cm/yr in the industrial area and 1.4cm/yr in the city centre . Goose Creek field south of Houston, in 1918, subsided more than 0.9m . The Wilmington field in California (USA) subsided 10m, Lake Maracaibo fields in Venezuela subsided 3.5m . The Groningen in Netherlands showed noticeable subsidence on seafloor at about 24.5cm (Poland and Davies, 1969). The Norwegian North sea fields (Ekofisk and Eldfisk and Calhall fields) reservoirs compacted; resulting in current subsidence rate of 20cm/yr. The Ekofist field also showed formation pressure decline from the discovery of 7200psi to a potential abandonment at 3200psi resulting in decrease in porosity from 38% to 33% (Barkved and Kristiansen, 2005). Low-strength carbonate reservoirs in Northwest Java field, Indonesia, and fields offshore Sarawak, Malaysia, have also experienced significant subsidence . The Belridge field in California and neighbouring diatomite fields subsided and had numerous well failures . Compaction is the decrease in volume of a reservoir resulting from pressure reduction and production of fluids (water, oil and gas). The term compaction and subsidence describe two distinct processes. Compaction is a volumetric change in a reservoir while subsidence is a change of level of a surface. The surface could be a formation top, the mudline in a submarine area or a section of the Earth's surface above the compacting formation. Land subsidence can lead to flooding over wide areas, particularly when unfavourable meteorological events of high-tide, sea storm, and wind blowing in the direction of the shore take place Carbognin et al., 1984a). These situations could be aggravated by erosion Time-lapse orthometric levelling measurements, acquired in 1988 and 2003 in the south-east Niger Delta basin, are used to estimate surface subsidence resulting from hydrocarbon withdrawal. The value of the subsidence was determined by finding the differences from the orthometric heights in the base and the monitor surveys. The elevation ranges between -30m along river channels and 3m for the base 3D survey while that for the monitor survey shows elevation of -27m to 5m. Hydrocarbon production in reservoir under this area was 89.52stb/day initially and declined to 13.92stb/day, and the reservoir pore-fluid pressure depletion is only 674psi, initially at 3833psi but dropped to 3159psi in 15 years. The results from the analysis show that the rate of land subsidence at each location of levelling varies from 66.67mm yr -1 to 200.00mm/yr with an average of 86.00mmyr -1 . When comparing the land subsidence trend, hydrocarbon production and reservoir pressure declines, there is no positive correlation between the three phenomena. This is an indication that land subsidence is localized where the measurements are carried out mainly in river channels and slopes caused by erosion, and not on a regional scale. The results of this work can be used for engineering and environmental works.
SN Applied Sciences, 2019
Hydrochemical analysis of water samples from Yenagoa in the Niger Delta shows widespread occurren... more Hydrochemical analysis of water samples from Yenagoa in the Niger Delta shows widespread occurrence of iron (Fe) in the groundwater. The Fe concentration is more than 0.3 mg/L at many places, and the distribution is heterogeneous both vertically and horizontally. In order to identify the cause of the high heterogeneity, we carried out an integrated study consisting of hydrogeochemical, electrical resistivity sounding and induced polarization (IP) chargeability measurements at eleven sites and 2-D electrical resistivity profiling (at 2 sites). Data processing using inversion techniques resulted in 4-layered resistivity and chargeability-depth models. The results show that clean sand and gravel exhibit high resistivity but low chargeability and normalized chargeability values, whereas clay and sandy clay exhibit relatively low resistivity but high chargeability and normalized chargeability values. In sites where the aquifer is overlain by a thick clay layer, Fe concentration is high (Fe > 0.3 mg/L) in the groundwater and redox potential values range between 118 and 133 mV. We interpret that the low-permeability clay layer creates a relatively atmosphere-isolated state in the underlying aquifer, which is responsible for the reductive ambient subsurface groundwater environment. In sites where the aquifer is capped by silt, Fe concentration is low (< 0.3 mg/L) in the groundwater and redox potential values range between 115 and 164 mv indicating a mild oxidation environment. We interpret that the clay acts as a controlling factor to the Fe enrichment in the groundwater regime. Knowledge of the clay layer, which is identified in the present study, will be helpful in selecting suitable sites for boreholes.
Applied Water Science, 2014
Hydrogeophysical Characterization of Shallow Unconsolidated Alluvial Aquifer in Yenagoa and Environs, Southern Nigeria
Arabian Journal for Science and Engineering, 2015
Groundwater of the Quaternary shallow alluvial aquifer is the only safe and reliable water resour... more Groundwater of the Quaternary shallow alluvial aquifer is the only safe and reliable water resource in Yenagoa and environs, Southern Nigeria. The determination of the aquifer hydrogeophysical parameters is thus critical and constitutes the basic foundation for optimizing the short- and long-term groundwater utilization strategies. In this study, 29 Schlumberger vertical electrical soundings, borehole data, pump test, hydrochemical analysis, and measured and/or calculated hydrogeophysical parameters were integrated to reconnaissance the local aquifer conditions. Aquifer qualitative and quantitative properties in terms of electric and hydraulic conditions were also investigated. The freshwater aquifer was delineated with true resistivity and thickness ranges of 134–664 Ωm and 6.7–41.4 m respectively. Transmissivity and hydraulic conductivity values vary between 189–2609 m2/day and 28–118 m/day, respectively. Porosity ranges between 0.40 and 0.45 and tortuosity ranges between 1.28 and 1.31. Correlation of the results of the geochemical analysis of the groundwater samples with the layer resistivities shows that in the locations where the aquifer is overlain by clay layer (ρ ∼ 10 Ωm) have higher concentrations of dissolved iron (Fe > 0.1 mg/L), whereas the iron concentrations are remarkably low (Fe < 0.1 mg/l) in areas the aquifer is underneath relatively thin silty sand layer (ρ ∼ 349 Ωm). The near-surface lithology acts as a controlling factor for spatial distribution of groundwater iron within the very shallow depths (<20 m). The geochemistry of the groundwater was observed to be controlled mainly by weathering of silicate group of minerals.
Journal of Water Resource and Protection, 2012
The application of geophysical methods in combination with pumping tests provides a cost-effectiv... more The application of geophysical methods in combination with pumping tests provides a cost-effective and efficient alternative to estimate aquifer parameters. In this study, nineteen Schlumberger vertical electrical soundings (VES) were occupied in parts of Bayelsa State using a maximum current electrode separation ranging beweeen 300 -400 m with the aim of estimating the transmissivity of the alluvial aquifer in areas where no pumping test has been carried out. Four of the soundings were carried out near existing boreholes in which pumping test had been carried out. The VES data obtained was interpreted, and layer parameters such as true resistivities and thickness were determined. The geoelectric parameters were used to generate the Dar Zarrouk parameters. Correlating the Dar Zarrouk parameter (e.g longitudinal unit conductance) with transmissivity derived from pumping test data, a constant was found which translate longitudinal unit conductance to transmissivity in a hydrogeological setting where effective porosity is the primary control on resistivity and hydraulic conductivity. Transmissivity determined from the pumping test data range between 1634.0 -5292.0 m 2 /day while transmissivity values estimated from the longitudinal unit conductance (L c ) range between 721 -8991 m 2 /day. The transmissivity estimated from the pumping test (T p ) data and transmissivity estimated from the longitudinal conductance (L c ) on comparison show excellent correlation (R 2 = 0.92). The high transmissivity values agree with the geology of the Benin Formation (Coastal Plain sands) consisting of fine-medium-coarse sands. The results give a useful first approximation of the transmissivity and could be used to site exploratory boreholes.
Global Journal of Pure and Applied Sciences, 2014
Fifteen (15) electrical surveys (VES) were carried out and results used to delineate the shallow ... more Fifteen (15) electrical surveys (VES) were carried out and results used to delineate the shallow lithostratigraphic units and evaluate the electrical and hydrogeological characteristics of the aquifer zone of the alluvial deposits in Yenagoa metropolis and environs. The Schlumberger electrode configuration was adopted and maximum current electrode halfspacings (AB/2) ranged from 100 to 200m. The VES data were interpreted using 1D inversion technique software (1X1D, Interpex, USA). A maximum of four geoelectric layers were delineated and the aquifer is characterised by loose sand with resistivity ranging from 136.1 -828.6Ωm and thickness of 8.3-97.6m. The hydraulic conductivity (K = 41.3m/day) value measured in a reference borehole was combined with the normalized electrical conductivity (σ 1 ) from a nearby vertical electrical sounding data. The resulting relation was interpreted with Dar Zarrouk parameters to infer the transmissivity variations at other vertical electrical sounding locations, where K values are unknown. The results showed that the transmissivity is linearly related to the normalized transverse resistance and hydraulic conductivity is also linearly related with normalized aquifer resistivity. Transmissivity values in the aquifer vary from 342.8 to 4030.9 m 2 /day, and hydraulic conductivity K varies from 12.0 -88.0m/day throughout the study area.
Engineering, 2012
Structural failure of buried cast/ductile iron water mains and tanks due to corrosion attacks man... more Structural failure of buried cast/ductile iron water mains and tanks due to corrosion attacks manifests in leaks and is common in most cities throughout Nigeria. The appropriate corrective action, which aims to restore pipe/tank integrity is usually based on proper understanding of the degree of corrosiveness of the soil. In an attempt to determine the potential corrosiveness of the soil to buried metallic structures in Bayelsa State, surface geoelectrical sounding was carried out. Twenty-five Schlumberger Vertical Electrical Soundings (VES) was carried out in the freshwater and meander belt geomorphic zone and the salt water mangrove swamp and estuary complex of the state using a maximum current electrode separation ranging from 200 -400 m. The data obtained was interpreted by computer iterative modeling using a 1D inversion technique software (1X1D, Interpex, USA). The results show a high degree of heterogeneity, both laterally and vertically, which is typical of a complex depositional environment. Generally, the sub-soil condition within the expected depth of installation of water mains and storage tanks (0 -10 m) is slightly or moderately aggressive (effective aggressivity) in the freshwater and meander belt geomorphic zone but is very strongly aggressive in the salt water mangrove swamp and estuary complex. Corrosion cells which may lead to significant corrosion failures may occur in the vicinities of strongly aggressive stations. This poses a significant corrosion risk to metallic water pipes and storage tanks. Current day design should therefore either mandate the use of a non-metallic piping product (water mains) or cathodic protection system. Prediction of potential corrosiveness of a soil and thus the application of proper corrosion control measures will not only protect the environment from spillages but will also avert cost of repair, clean-up and replacement.
Journal of Water Resource and Protection, 2012
Nineteen Schlumberger vertical electrical soundings (VES) were carried out within and around Yena... more Nineteen Schlumberger vertical electrical soundings (VES) were carried out within and around Yenagoa city, South South Nigeria, using a maximum current electrode separation ranging between 300 -400 m. The objectives of the study were 1) to evaluate the possibility of mapping Quaternary sediments to infer the geological structure from the electrical interpretation and identify formations that may hold fresh water with low concentration of conducting minerals such as iron 2) to evaluate the vulnerability of the aquifer in the study area. The interpretation of the data collected was by computer assisted iterative interpretation using 1-D inversion technique software (1X1D, Interpex, USA). The results of the interpretation revealed four distinct geoelectric layers. Sounding curve types obtained in the area are mostly of the form ρ 1 > ρ 2 < ρ 3 < ρ 4 (where ρ is the density) but fresh water lenses with low concentration of conducting minerals such as iron were obtained only in locations that exhibit ρ 1 < ρ 2 > ρ 3 < ρ 4 curve types. Depth to the aquifer ranges from 4.5 m in the vicinity of VES 05 to 27.0 m at the vicinity of VES 14. The resistivity of the aquiferous horizon varies between 60 -2868 Ωm. High transverse resistance values obtained were associated with zones of high transmissivity which agrees with the geology of the Benin Formation (Coastal Plain sands) consisting of fine-medium-coarse sands. The aquifer vulnerability map illustrates the impermeability of the overburden clay layer. Values of >0.5 mhos indicate good protective capacity, while values <0.3 mhos indicate vulnerable zones with probable risk of contamination.
Engineering, 2013
The corrosivity of the top three metres of the soil along a pipeline route was determined using s... more The corrosivity of the top three metres of the soil along a pipeline route was determined using soil electrical resistivity for the emplacement of a conduit intended to serve as a gas pipeline. Fifty-six Schlumberger vertical electrical soundings (VES) were carried using a maximum current electrode separation ranging between 24 -100 m at 2.0 km interval. The data were interpreted using a 1D inversion technique software (1X1D, Interpex, USA). Model resistivity values were classified in terms of the degree of corrosivity. Generally, the sub-soil condition along the pipeline route is non-aggressive but being slightly or moderately aggressive in certain areas due to local conditions prevailing at the measuring stations. Based on the corrosivity along the pipeline route, appropriate cathodic protection methods are prescribed.
Estimation of aquifer hydraulic parameters from geoelectrical method—a case study of Yenagoa and environs, Southern Nigeria
Arabian Journal of Geosciences, 2014
Knowledge of water transmitting properties of an aquifer is crucial for successful groundwater de... more Knowledge of water transmitting properties of an aquifer is crucial for successful groundwater development and management practices in an area. In this study, the determination of aquifer hydraulic characteristics at Yenagoa and environs from Dar Zarrouk parameters was carried out using 14 vertical electrical sounding data (VES) and information from existing boreholes. The Schlumberger electrode configuration was employed for the field data acquisition with a maximum half electrode separation (AB/2) ranging between 100 and 350 m. The VES data were interpreted using 1D inversion technique software (1X1D, Interpex, USA). A maximum of four geoelectric layers were delineated and the aquifer is characterized by loose sand with resistivity ranging from 136.1 to 828.6 Ωm and thickness of 8.3–97.6 m. Using the VES results and water resistivity, porosity was determined using modified Archie’s equation. The hydraulic conductivity (K) values obtained from three reference boreholes were combined with the electrical resistivity obtained from the respective nearby VES stations to determine a diagnostic constant (Kρ). The resulting relation was interpreted with Dar Zarrouk parameters to infer the hydraulic conductivity (K) and transmissivity (T) variations at vertical electrical sounding locations, where K values are unknown. The results indicate that porosity varies between 0.09 and 0.32. The hydraulic conductivities range from 0.8 × 10−4 to 6.6 × 10−4 m/s while the transmissivity values vary between 1.1 × 10−3 and 29.6 × 10−3 m2/s. The high transmissivity values are consistent with the aquifer being unconsolidated with fine–medium–coarse sands.
Anisotropy Parameter Estimation Using Semblance Based Rational Interpolation Technique
Journal of Applied Sciences, 2008
ABSTRACT The presence of anisotropy influences many aspects of seismic wave propagation and there... more ABSTRACT The presence of anisotropy influences many aspects of seismic wave propagation and therefore has profound implications for conventional data processing schemes in exploration seismics. Here, we have studied the lateral variation of the anellipticity parameter (η), the horizontal velocity (vhor) and normal moveout velocity (vnmo) using 2D surface seismic data acquired in the Gulf of Mexico. Data processing included application of a bandpass filter to remove frequencies outside of the useful signal bandwidth; formation of supergathers by vertically stacking nine consecutive common midpoint (CMP) gathers to enhance signal-to-noise ratio and frequency-wavenumber (F-K) filtering to suppress coherent noise. Frequency-offset (F-X) deconvolution and coherency filtering to further suppress residual random noise and enhance signal continuity. Moveout curves for three reflection events of interest were obtained by application of a rational interpolation procedure to tau-p derived travel times and offsets. Semblance analysis carried out on each of the moveout curves yielded η, vhor and vnmo. The results show that the effective and interval values of η varies mainly between 0.03-0.16±0.01 and 0.03-0.2±0.03, respectively. Effective values of vnmo and vhor vary between 1850-2250±111 and 1975-2475±122 m sec-1, respectively. Interval values of vnmo and vhor vary between 1750-2650±120 and 2100-3100±122 m sec-1, respectively. The results suggests that in ensembles 1-4 and 7-9, layer 2 is a shaly formation while layers 1 and 3 are sandy formations characterised by considerably reduced anellipticity.
Research Journal of Applied Sciences, 2011
This study investigates the effective stress -porosity relationship above and within the oil wind... more This study investigates the effective stress -porosity relationship above and within the oil window in the Kimmeridge Clay Formation (KCF) in the North Sea Basin (UK) using effective stress and porosity determined from wireline logs and pore pressure data. Porosity was determined from an empirical porositysonic transit -time transform, calibrated using shale and mudstone core porosity measurements from Jurassic shales in the North Sea. Effective stress was determined from the total overburden stress and pore pressure. The total overburden stress was calculated by integration of the density log. The results show that porosity range between ~11-20% in the pre-generation zone but decreased to <5% within the oil window. Compaction coefficient ($) values above the oil window vary from ~0.08-0.09 M/Pa, but vary from ~0.05-0.06 M/Pa within the oil window implying that deeper burial and a high degree of chemical precipitation and cementation has created a stiff matrix giving rise to low $ values. The effective stress-porosity relationship above and within the oil window reflects a possible decrease in effective stress occasioned by increase in porosity in the pregeneration zone.
Research Journal of Applied Sciences, 2011
In this study, the effects of petroleum generation and expulsion on shale porosity is explored by... more In this study, the effects of petroleum generation and expulsion on shale porosity is explored by evaluating the compaction of the Kimmeridge Clay Formation (KCF) within the oil window using log data and shale samples from the KCF within the depth and temperature range of ~1.5-5.0 km and 90-157ºC, respectively. Petrophysical properties e.g porosity and pore-size distribution were measured, and permeability was calculated using empirical models based on the measured porosities. Transit-time values from the sonic logs recorded at depths in the wells were the cores were recovered were calibrated against the porosities determined from the core samples. Bulk geochemical parameters e.g., Total Organic Carbon (TOC), Hydrogen Index (HI) were determined. The volume reduction in the KCF within the oil window due to petroleum generation and expulsion, and compaction due to loss of pore space was determined using the geochemical and log derived porosity data emplaced into empirical relations. Porosities above the oil window range from ~15-20%, but decreased to <5% at the end of the oil window. Pore-sizes decrease from ~11 nm to between 6-8 nm at the depth range of 1.5-5.0 km. Permeability decreased from 4.8 nD to ~0.095 nD. The quantitative estimations of volume reduction within the oil window indicate that for ~8.0wt% initial TOC sediment, a bulk volume reduction of 13% of the initial volume is due to oil expulsion, and ~12% is due to loss of pore space.
Research Journal of Applied Sciences, 2011
This study presents a data set comprising estimated permeabilities of 22 natural mudstones which ... more This study presents a data set comprising estimated permeabilities of 22 natural mudstones which also have been characterised in terms of their pore size distribution, porosity, grain density and Total Organic Carbon (TOC) content. Pore size distribution and grain density were determined using mercury porosimetry and pycnometer method. TOC was determined by direct combustion of the organic carbon in LECO RLS-100 Carbon Sulphur analyser. Permeabilities were estimated based on the measured pore throat size distribution plus assumed pore alignment and pore shape using the model of Yang and Aplin. TOC and grain density ranges from 3.44-9.98% and 2.61-2.70 g/cm 3 , respectively. Porosity decreases from ~24-3% between the depth range of 1515-4781 m. The pore size distribution data show that the mean pore radius decreases from ~36-2 nm within the same depth range, the shift to smaller mean pore radii is driven primarily by the collapse of pores larger than 10nm with increase in consolidation. These values represent some of the smallest pore sizes known for rocks and in part provide a qualitative explanation for the low shale permeabilities. Estimated vertical permeabilities range from 9.5×10G 23 to 8.6×10G 21 m 2 . In general, permeability decreases logarithmically with porosity.
Volumetrics of Petroleum Generation and Compaction of the Kimmeridge Clay Formation
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Papers by Kenneth Okiongbo