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geoelectric Sounding for the Determination of Aquifer Transmissivity in Parts of Bayelsa State, South South Nigeria

Journal of Water Resource and Protection 2012年第6期4卷 346-353页

作者： Kenneth S. Okiongbo Ebifuro Odubo Department of Geography and Environmental Management Niger Delta University Wilberforce Island Nigeria Department of Geology & Physics Niger Delta University Wilberforce Island Nigeria

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 m2/day while transmissivity values estimated from the longitudinal unit conductance (Lc) range between 721 - 8991 m2/day. The transmissivity estimated from the pumping test (Tp) data and transmissivity estimated from the longitudinal conductance (Lc) on comparison show excellent correlation (R2 = 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.

关键词： Aquifer Longitudinal Conductance Transmissivity Dar Zarrouk Parameters geoelectric Parameters Yenagoa

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geoelectric Structure of the Crust along the Mbere Trough (South Adamawa) from Audio-Magnetotelluric Data

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International Journal of Geosciences 2013年第8期4卷 1215-1227页

作者： Ludovic Houetchak Kande Joseph Kamguia Jean Marie Tadjou Robert Nouayou Department of Physics Faculty of Science University of Yaounde I Yaounde Cameroon National Institute of cartography Yaounde Cameroon

The South Adamawa trough represents a major structure associated to the tectonic activity in the Adamawa region. The Mbere and the Djerem troughs represent the eastern and the western parts of the South Adamawa trough respectively. The audio-magnetotelluric (AMT) method is used to study the Mbere trough and to bring out tectonic features that affect the basement of this region during the Cretaceous. From analysis and interpretation of AMT data, based on pseudo-section and geoelectric section, two geologic models are constructed across the trough at Belel and Nyambaka. Those models bring more information on the sediments thickness and the borders faults of the trough compared to previous studies. The results shows that the Mbere trough is dissymmetric, and bounded on its northern side by an intra-gneissic fault and on its southern side by two faults with at least one considered as a faulted contact between the granitic and gneissic rocks. The sediments filling of the trough are consist mainly of conglomerates on which lay sandstones. The thickness of these sediments is about 2060 m at Belel and decreases to about 1800 m at Nyambaka, with a low sandstones thickness, which does not exceed 360 m. The basement consists of granite in the South of the trough and gneiss in the North, with resistivity more than 10,000 Ω.m. The Moho is located between 25 and 35 km in the South Adamawa region.

关键词： Adamawa Trough Fault Resistivity Pseudo-Section geoelectric Section

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Characterization of Pan-African Aquifer Layers by the Least Squares Inversion Method Applied on geoelectric Data

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International Journal of Geosciences 2019年第10期10卷 845-859页

作者： Kana T. Idriss Serge H. Pokam Kengni Ndikum Eric Ndoh Blaise P. Gounou Pokam Charles T. Tabod Department of Physics Faculty of Science University of Yaounde I Yaounde Cameroon Department of Physics Faculty of Science University of Bamenda Bamenda Cameroon Department of Physics HTTC Bambili University of Bamenda Bamenda Cameroon.

geoelectric data obtained from forty (40) vertical electrical soundings collected with a Schlumberger device in the Adamawa plateau region, also known as the Cameroon water tower, have been treated by the least-squares inversion method. In order to study the nature and thickness of the aquifer and the necessary geoelectric parameters, quantitative and qualitative interpretations of the data were made. The results obtained showed that: about four to five geoelectric layers have been delimited in the study area with a dominance of the KH curve, which can be used as a reference for future studies. The first two layers constitute an association of clay and laterite with resistivity values ranging from 58 to 9122 Ω·m and whose thickness is between 0.6 and 13.4 m. The third layer is a potentially aquiferous laterite composed of clay, laterite and especially clay sand and cracked/good granite, with a dominance of sandy alteration whose resistivity values are between 81 and 960 Ω·m and its thickness between 12.2 and 26.8 m. The fourth and fifth layers are made up of cracked/good granite with a resistivity ranging from 12-10705 Ω·m with an average value of 1817 Ω·m. This study also shows that the North-East, South-West and South sectors could be the groundwater convergence zones and that the average depth of the basement aquifer roof is about 28.3 m. The geoelectric sections of certain demarcated vertical electrical sounding stations are consistent with the geologic description of the area.

关键词： Adamawa Plateau Region Vertical Electrical Sounding geoelectric Sections Aquifer Groundwater

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Numerical Calculation of geoelectric Fields That Affect Critical Infrastructure

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International Journal of Geosciences 2019年第10期10卷 930-949页

作者： David H. Boteler Risto J. Pirjola Geomagnetic Laboratory Natural Resources Canada Ottawa Canada

One of the modern applications of geomagnetism is determining the effect of geomagnetic disturbances on critical infrastructure such as power systems and pipelines. Assessing the geomagnetic hazard to such systems requires calculation of the geoelectric fields produced during geomagnetic disturbances. Such geoelectric fields can then be used as input to system models to calculate the impact on the system. This paper describes what is involved in calculating the geoelectric fields produced during real geomagnetic disturbances. The theory of geomagnetic induction is presented and used to derive the Earth transfer function relating the geoelectric and geomagnetic field variations at the Earth’s surface. It is then shown how this can be used to make practical calculations of the geoelectric fields and how the calculation process can be verified by comparison with analytic solutions obtained with synthetic geomagnetic variation data. The accuracy of the calculated geoelectric fields for geomagnetic risk assessments is limited, not by the accuracy of the calculation methods, but by the availability of geomagnetic field measurements and Earth conductivity information over the whole extent of the affected infrastructure.

关键词： geoelectric Fields Geomagnetic Disturbances Critical Infrastructure Hazard Assessment

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Saltwater Intrusion in Jizan Coastal Zone, Southwest Saudi Arabia, Inferred from geoelectric Resistivity Survey

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International Journal of Geosciences 2015年第3期6卷 286-297页

作者： Saad Mogren Department of Geology and Geophysics College of Science King Saud University Riyadh Kingdom of Saudi Arabia

This work focuses on the causes of water quality deterioration in the coastal plain of Jizan area, southwest Saudi Arabia using vertical electrical sounding (VES) surveys. Schlumberger electrode array is used in the study with the current electrode spacing ranging from 400 to 600 m to delineate the thickness of the shallow aquifer and its possible interaction with the sea water. The differences in resistivity are associated with the variations in lithology and groundwater saturation and salinity. The interpretation of VES curves reveals low resistivity zones characterizing the study area. These zones reflect saline water intrusion in the coastal aquifer. Generally, it is observed that the resistivity of saturated zone decreases towards the sea, indicating the influence of seawater. Based on the interpretation of the constructed resistivity pseudo-sections and 1-D sequential inversion models, three factors are identified to control the seawater intrusion into the shallow groundwater aquifers: 1) presence of faults that contribute extensively in the seawater intrusion as the seawater invades the coastal aquifers through the crushed rocks in fault zones related to the Red Sea rifting, 2) over-withdrawal of groundwater from the coastal aquifers, resulting in saline water intrusion from the sea into the freshwater aquifer, and 3) the lithological variation where the alluvial sediments of the ancient buried wadi (dry valley) channels provide potential pathways for saltwater intrusion and make a hydraulic connection between the aquifer and the sea water.

关键词： geoelectric Resistivity Seawater Intrusion Jizan Area Saudi Arabia

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Deep geoelectric Structure and Its Relation to Seismotectonics of the Saurashtra Region, Western India

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Open Journal of Earthquake Research 2020年第2期9卷 181-200页

作者： D. N. Murthy K. Veeraswamy T. Harinarayana CSIR-National Geophysical Research Institute Hyderabad India Presently at BS Abdur Rahaman Crescent Institute of Science and Technology Chennai India

The Saurashtra Peninsula and its adjoining regions covered by Deccan Traps (DT) are one of the important parts of the Indian continental lithosphere with interesting geophysical anomalies, tectono-thermal evolution since the Mesozoic times. Knowledge on the deep structure beneath these formations is important for understanding the seismo-tectonics of the region. This region has gained importance after the occurrence of a major earthquake (7.9 Mw) north of Saurashtra, namely Bhuj earthquake during 2001. It is also observed that Saurashtra region has experienced several earthquake swarms limited to small regions. Accordingly, it is important to investigate the deep structure of the Saurashtra region from seismotectonics point of view. In our study, magnetotelluric results of the deep crustal structure along five NS oriented traverses are presented. The five traverses are—Halvad-Rohisa (HR), Sapar-Iswaria (SI), Mota Dahinsara-Bamagadh (MB), Jodiya-Jamkhandorna (JJ) and VavBeraja-Devda (VD). The total length of these 5 traverses is about 670 km. The derived deep geoelectric structure is also compared and correlated with gravity data to get more confidence on the derived results. The 2-D geoelectric section has delineated anomalous high conductivity structure at places extending from 20 km to about 40 km. From the spatial correlation, anomalous high conductive structure derived from MT data with intense localized seismic activity is an interesting observation. In the present study, the results of magnetotelluric studies along with other geophysical results are presented.

关键词： Magnetotelluric Seismotectonics geoelectric Structure Earthquakes Electrical Conductivity

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Contribution of Geophysical Prospecting(geoelectrical Method) for the Hydrogeological Reconnaissance of the Region of Ouled Youssef(Tadla's Basin,Morocco)

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地学前缘 2009年第S1期16卷 130-131页

作者： Sanaa el Batali Hassane Sahbi Ali Essahlaoui Mustapha Boualoul Geological Engineering Laboratory Faculty of Sciences

The Turonian aquifer of the Tadla’s basin shows at present a pronounced reduction of its hydraulic potential linked to overexploitation and deficiency of effective *** order to make an evaluation of the resources of ... 详细信息

关键词： Morocco Tadla’s basin climatology geoelectrical method Turonian aquifer isoresistivity geoelectric sections exploitation’s drillings

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geoelectrical Investigation of a Proposed Dam Site in a Sedimentary Terrain: Case Study of Aba River at Amapu-Ideobia, Akanu Ngwa Southeastern Nigeria

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International Journal of Geosciences 2013年第10期4卷 1376-1381页

作者： Sabinus Ikechukwu Ibeneme Kalu Kalu Ibe Alexander Olusegun Selemo Johnbosco Okechukwu Nwagbara Young Ezenwa Obioha Kingsley Obi Echendu Bridget Odochi Ubechu Department of Geosciences Federal University of Technology Owerri Nigeria Department of Physics Federal University of Technology Owerri Nigeria

The geoelectrical investigation of the proposed Aba River dam at Amapu-Ideobia, Akanu Ngwa Southeastern Nigeria has been carried out. The objective of this study is to determine the downward and lateral trends of the rock layers or units along and near the proposed dam axis and deduce the possible structures that may enhance workable design of the dam. ABEM Terrameter SAS 4000 model was used and the symmetrical Schlumberger configuration was adopted. Twelve (12) Vertical Electrical Sounding stations were located and fully occupied along the dam axis. Preliminary input data from the field were fed into Zohdy software to generate real resistivities and depths to geoelectric layers. Five geoelectric layers were interpreted as Loamy Top soil, Alluvial matter, Pebble bed, Sandy lateritic and Gravely sand. Layer 1 (the top loamy soil) was encountered in VES 1, 2, 3, 4, 5, 9, 10, 11 and 12 locations with maximum thickness of 1.5 m in VES 3 and 4. Resistivity values ranged from 216 to 519 Ohm-m. The second layer (lateritic matter) had a maximum lower depth of 5 m in VES 3 and 4 points. This was not encountered in VES 6 point being replaced by alluvium. Resistivity values ranged from 101 to 6190 Ohm-m. Layer 3 was interpreted as a restricted pebble bed which occurred only at VES 6, 7 and 8 locations flanking the river course with thickness of about 3.5 m and resistivity values range of 182 415 Ohm-m. The fourth layer was modeled as the alluvial matter and restricted to the river course (VES 6, 7, 8) locations with base at between 12.5 m in VES 8 and 8 m in VES 6. The last modeled layer (Layer 5) was composed of gravely sandstone that underlined the whole study area apart from the restricted pebble bed at the NE crestal portion (VES 12). No structures like fractures, lineaments and faults that would be of deleterious effect were observed in all the VES points down to about 40 m. However, it was observed that the axial length had overriding sandy matter with high porosity and

关键词： Aba River Amapu-Ideobia Dam Axis Electrical Resistivity geoelectric

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Groundwater Investigation Using geoelectrical Method: A Case Study of the Western Region of Cameroon

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Journal of Water Resource and Protection 2013年第6期5卷 633-641页

作者： Thomas D. A. Keleko Jean Marie Tadjou Joseph Kamguia Tabod Charles Tabod Alain N. S. Feumoe Jean Victor Kenfack Faculty of Science University of Bamenda Bamenda Cameroon Faculty of Science University of Yaounde I Yaounde Cameroon

A geoelectrical survey using the electrical resistivity method was carried out in some villages in the western region of Cameroon to investigate the sub-surface layers and evaluate the characteristics of aquifers. The direct current electrical resistivity method was utilized for the present study. Applying the Schlumberger array, a total of twenty four (24) Vertical Electrical Soundings (VES) were conducted. Quantitative and qualitative interpretations of data were carried out to determine the nature and thickness of the aquifer zone combined with existing litho-logs aided correlation of geoelectric sections to litho-logs. Four to five geoelectric layers were delineated from the survey area. The first layer which is the topsoil has resistivity values ranging from 6 - 949 Ωm and the thickness is between 0.2 - 4.2 m. The second layer which is made up of clay and laterite has resistivity values ranging between 9 - 1862 Ωm and thickness range from 1.0 - 16.4 m. The third and fourth geoelectric layers are made up of clay and granite/basalts with thickness varying from 2.2 - 39.5 m which corresponds to an aquifer horizon. Resistivity values of the aquifer ranges from 10 to 70,506 Ωm. The resistivity map drawn from these measurements shows the presence of a low resistivity zone which indicates the reflection in the direction of ground water from northeast to southwest with the recharge concentrated to the south of the study area. This study has revealed for this area, an average depth of the aquifer of 32 m with the average thickness of the aquifer being 22 m. The geoelectric sections of some VES stations demarcated corroborate very well with the geological description of the area.

关键词： Vertical Electrical Sounding Groundwater geoelectric Section Aquifer Resistivity

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Groundwater exploration using integrated geophysics method in hard rock terrains in Mount Betung Western Bandar Lampung,Indonesia

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Journal of Groundwater Science and Engineering 2022年第1期10卷 10-18页

作者： Rustadi I Gede Boy Darmawan Nandi Haerudin Agus Setiawan Suharno Department of Geophysical Engineering University of LampungBandar LampungIndonesia Department of Environment Science University of LampungBandar Lampung

The presence of hard rock in Mount Betung has caused the misalignment of the groundwater aquifers,and resulted in many drilling failures for *** integrated geophysics method using gravity survey and geoelectric Vertical Electrical Soundings(VES)were conducted to study the effect of basement and hard rock on groundwater *** the gravity method,38 mapping points were carried out randomly,with a distance of 1-2 km ***,from the geoelectric method,51 VES points were acquired at the foot of Mount *** acquisition was conducted with a Schlumberger configuration with AB/2=1 m to 250 *** results show the Bouguer Anomaly in the west is 50-68 mgal due to the presence of hard rock in Mount *** anomaly responds to relatively shallow hard rocks near *** rocks composed of andesite and breccia normally present at the depth of 5-180 m during well *** isopach mapping from VES data(at AB/2=50 m,100 m,and 150 m)shows the dominant constituents of hard *** in hard rock contribute to secondary porosity,which could be a prospect zone that transmit *** finding shows that the fractures are randomly scattered,causing several well failures that have been ***,the fractures in the hard rock at the foot of Mount Betung acts as conduits between recharge at Mount Betung and the aquifer in the Bandar Lampung Basin.

关键词： geoelectric Gravity Groundwater Hard Rocks VES

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