Schlumberger Vertical Electrical Soundings Research Articles

Exploration of Ground Water Potential of Federal University of Technology, Owerri and Its Environs Using Resistivity Survey

The research focused on evaluating the groundwater potential in the vicinity of Federal University of Technology Owerri (FUTO) using a resistivity survey method. The investigation involved the utilization of eleven Schlumberger vertical electrical soundings (VES). The data collection was conducted using an ABEM Terrameter SAS4000 and then processed with IPI2Win Software, which relies on the conventional theory of curve matching. This process aimed to determine the depth, quality, and subsurface formations of the groundwater. The VES interpretation results revealed the presence of 3-5 geoelectric layers above the aquiferous layers. Various curve types were identified in the study area, including monotonically ascending (AA), bowed-ascending (HA), bowl-bell (HK), and ascending-bell (AK) curves. The majority of the field curves were found to be of the A-shaped type, signifying specific aquifer characteristics. The study indicated that the depth to the water table is relatively shallow in the Ihiagwa area, with an average depth of 7.26 meters. In contrast, the aquifer's depth is deeper around Avu, Nekede, and Eziobodo areas, with a mean depth of 32.33 meters. Obinze had very deep aquifers, with an average depth of 57.75 meters. Furthermore, the study established a relationship between aquifer characteristics and geoelectric parameters, allowing for the estimation of hydraulic conductivity and transmissivity values at all the sounding locations, even in areas lacking boreholes. These hydraulic characteristics showed that the aquifer had protective capacities ranging from 0.036 to 0.509 mhos, transmissivity values ranging from 11856.32 to 28661.28 m2/day, and hydraulic conductivity ranging from 13.47 to 1009.2 m/day. These values suggested that the aquifer materials are highly permeable, facilitating fluid movement within the aquifer. This research demonstrated the effectiveness of surface geophysics in estimating aquifer hydraulic characteristics, particularly in situations where pumping test data are unavailable. It also highlighted the vulnerability of the aquifer to surface contaminants. The findings are expected to be valuable for the long-term planning of groundwater exploitation projects in the study area.

Assessment of effects of a Cemetery leachate on Groundwater Quality using an Integrated Approach

The dependency of residents in the vicinity of cemeteries on groundwater from hand-dug wells as an alternative source of water supply for their domestic use without cognisance of the quality of such water has been a concern. So, this research assesses the effects of a cemetery on groundwater quality using an integrated approach in Edunabon, South-western Nigeria. Thirty groundwater samples from available hand-dug wells were collected and analysed for various physicochemical parameters. GIS cloud data collection server and Mobile Data Collector (MDC) were used to obtain these hand-dug wells' locations and spatial distributions. The determination in variation in physicochemical concentration parameters was obtained using the curve fitting technique of ARCVIEW GIS software and digital map. Physicochemical results were used to calculate Water Quality Index (WQI) of each sample. Two Schlumberger Vertical Electrical Soundings (VES) of 130.0m long were conducted at 10.0m intervals to the wall and the next VES, on each side of the cemetery. Current spacing (AB/2) and apparent resistivity (ρa) data were plotted on a double logarithm paper, curved matched and iterated using IPI2Win software for qualitative and quantitative interpretation. WQI results ranged from (107.37–173.64), (76.60–93.37), (54.94–71.53), (31.29–48.01), and (10.84–25.31) for fourteen, seven, three, four and two hand-dug wells respectively, an indication that the water from these wells was unfit for drinking, very poor, poor, good, and excellent respectively. VES results revealed that first, second and third layers were mainly clayey topsoil (46.7–96.8Ωm), lateritic soil (169.0–551.3Ωm), and weathered layer (3.21–27.4Ωm), which favourably enhances the migration of leachate from the cemetery to the surrounding soils and groundwater. The lowest resistivity values recorded in the second and third layers indicated leachate presence at these hand-dug wells. The integration of GIS and electrical resistivity methods would be useful tools to assess groundwater quality around cemeteries. Keywords: Groundwater quality, Mobile Data Collection, unfit for drinking, Vertical Electrical Sounding, Water Quality index

Groundwater potential zones identification in Purwobinangun, Pakem, Sleman, D.I. Yogyakarta using vertical electrical sounding (VES)

Water is crucial part in tourism development. However, not all locations have good and accessible groundwater resources. Ngepring Vineyard in Purwobinangun Village, Pakem District, Sleman, Yogyakarta face this problem. Ngepring vineyard is a developing tourism area at southern mountainside of Merapi which is one of geotourism destination in Indonesia. In its development, there were obstacles to fulfill the water supply for tourism and locals’ daily use. This research aims to determine groundwater potential zone and recommend a drilling point for a new well. Geoelectric resistivity survey conducted to evaluate subsurface condition by measuring and interpretating rock resistivity properties. Schlumberger Vertical Electrical Soundings (VES) configuration used with a maximum spacing from the center point as far as 250 meters with three VES were measured in study area along two N-S profiles perpendicular to one E-W profile. As the results, there is a sand layer at approximately 80m depth interpreted as aquifer. This result can be used as a preliminary study used to determine potential location for a new water resource in Ngepring vineyard.

Geoelectrical Exploration of Groundwater by Using Vertical Electrical Sounding Technique at Wadi Morra, South Sinai, Egypt

Wadi Morra area is one of the most important areas targeted by the government for sustainable development. This development depends mainly on groundwater occurrences. This research aims to explore groundwater in this region, which depends on groundwater for its needs. To achieve this aim, the geoelectrical resistivity method was used, represented by Schlumberger Vertical Electrical Soundings (VESs). Seventeen VESs have been carried out with a maximum half current electrode spacing (AB/2) of 700m. The measured VESs are interpreted qualitatively and quantitatively to construct a geoelectrical model. To detect the water-bearing layers and their extensions, three geoelectric cross-sections in addition to a one-panel diagram were constructed using all the available data. Also, both true resistivity and isopach contour maps of waterbearing layers were created based on these data. The interpretation results indicate that there are five geoelectric layers (A, B, C, D, and E), two of them (C and D) are water-bearing layers. The first water-bearing layer is layer C, which represents the Nubian sandstone aquifer, and the second layer is layer D, which represents the fractured basement aquifer. These two aquifers were observed along the northern part of the Saint Catherine - Nuweiba road that dissects the Wadi Morra basin, while it is absent at the southern part of this road. It is due to the presence of a few faults. According to groundwater occurrences, the study area was divided into two zones. The first zone is zone (A) where the groundwater is present, either in the Nubian sandstone aquifer or in the fractured basement aquifer and the second zone is zone (B) where there is no groundwater at all due to the presence of basement rocks at a few depths. This research also recommends that the best places for drilling productive wells be at zone A.

Geoelectrical Investigation of a Proposed Landfill Site in Ogbomoso, Southwestern Nigeria

An integrated geophysical investigation was carried out at a proposed landfill site along the new Ibadan-Ilorin Expressway in Ogbomoso, Southwestern Nigeria in order to characterize the subsurface and determine the suitability or otherwise of the site for landfill. The study location is underlain by rocks of the basement complex. 29 Schlumberger Vertical Electrical Soundings were conducted along seven traverses each about 100m long, about 20m apart, with station spacing of about 30m and half current electrode spacing varying between 1 and 100m. The VES data were interpreted quantitatively by partial curve matching and 1-D computer iteration and the layer parameters were used to generate the geoelectric sections. Wenner electrical resistivity profiling was also conducted along the traverses with station spacing of 25m and electrode spacing varied between 5 and 15m, and the data were interpreted using 2D inversion procedures. The VES results revealed three layers defined by the topsoil, clay layer and fractured/fresh bedrock. Depth to the bedrock is generally shallow with a mean of 9.0 3.7m. The mean thickness of the saprolite (mainly comprising clay) is 8.6 4.0m. 2D inversion of the resistivity profiling data revealed intense fracturing of the bedrock. The water table is shallow, ranging from 2 to 6m and may be rather close to the landfill base or fall within the landfill wastes. The study area is underlain by clayey overburden capable of protecting groundwater in the underlying aquifer unit from contamination by the leachate dischargeable from the landfill wastes. However, the presence of shallow water table and bedrock fractures may promote contamination of groundwater in the underlying aquifer unit and pose substantial health risk to the host community. It can therefore be concluded that the study area is not a suitable location for siting landfill. Keywords: Contamination, Leachate, Clay, Water table, Bedrock fractures DOI: 10.7176/JEES/11-16-04 Publication date: June 30 th 2021

Landslides articulation in Wadi Hof area southeast of Cairo, Egypt, based on geological and geophysical investigations

Detailed field geological, geoelectrical, hydrochemical, and microbiological studies were executed in the Wadi Hof area, southeastern Cairo, Egypt to delineate the causes of landslides along the train pathway between the eastern Wadi Hof camp and the western clay quarry. The area under consideration is of a gentle slope from east to west. The Eocene limestone rocks constitute the most common outcrops. Structurally, the investigated area was affected by faulting. Geophysically, 1D Schlumberger Vertical Electrical Soundings in addition to 2D Wenner Electrical Resistivity Tomography (ERT) techniques were performed to characterize the shallow subsurface implications. Eight Vertical Electrical Soundings were measured along with two main profiles-oriented northwest-southeast directions. A Schlumberger configuration with electrode separation starting from electrode separations (AB\2) = 1.5 m. to AB\2 = 200 m. was applied. Three 2D Electrical Resistivity Tomography profiles crossing the train pathway were constructed in a nearly east–west direction. The 1D inversion is applied using WinSev3.4 software and the 2D-ERT profiles were computed using the RES2DINV computer software. Moreover, hydrochemical and microbiological investigations in the form of water samples analysis were conducted east and west of the train pathway. The hydrochemical and microbiological characteristics of the analyzed water found that the water origin is different on the sides, east and west of the railway tracks. The integrated interpretations indicate that the study area consists of three main rock units; surface marl, calcareous sand, and, finally, clay to sandy clay units. The water originates from the Eocene limestone aquifer east of the train route directed towards the clay quarry west of the train path. Additionally, the landslides apparently result from the swelling of thick clay layers which leads to subsequent railway destruction shortly thereafter.

Typology of Sounding Curves and Lithological 1D Models of Mineral Prospecting and Groundwater Survey within Crystalline Basement Rocks in the East of Cameroon (Central Africa) Using Electrical Resistivity Method and Koefoed Computation Method

Resistivity method using seventy-sixth (976) Schlumberger vertical electrical soundings along forty-one (41) profiles are conducted in the Batouri and Ngoura subdivisions, East region of Cameroon, to investigate the subsurface layering, mineral potential, and groundwater resource characteristics. Results of quantitative and qualitative interpretation of data using Koefoed computation method reveal two to five layers having geometrical and electrical characteristics of geological layer models: topsoil (0.5 m<ep<3 m; 600<ρ<3000 Ω.m), lateritic soils (3<ep<20 m; 1000<ρ<4000 Ω.m); conductive layer (5<ep<110 m; 100<ρ<1000 Ω.m); fractured/weathered granite (20<ep<60 m; 1000/5000<ρ<3000/9000 Ω.m); clayey layer (5<ep<20 m; 600/1500<ρ<2000/3500 (dry) Ω.m); and fresh granites (ρ>4000 Ω.m). From the qualitative interpretation of VES curves, the subsurface layering is depicted by nine (09) types of sounding curves (G, H, A, QH, KH, HK, HA, HKH, and KHK) characterizing the vertical changes and the typology of sounding curves in the East Cameroon crystalline basements. The lithology of the subsurface is dominated (more than 80%) by geoelectrical and lithological 1D models derived by the H, QH, KH, HK, HA, HKH, and KHK curve types. These models are characterized by the presence of conductive layers and fractured/weathered granites derived from tectonic activities of the region. Also, the resistivity method (VES) applied in this study bring information about variation of the resistivity with depth, geological structures, fractures, and rupture zones in the underground until 120 m depth. These abovementioned information reveal proper hydrogeological and mining conditions for an efficient evaluation of the mineral potential and groundwater resources.

Comparative assessment of aquifer susceptibilities to contaminant from dumpsites in different geological locations

Geophysical and hydro-chemical investigations have been undertaken within the vicinity of Arapaja, Apete and Sabo dumpsites monolithically underlain by three different rock types namely; Migmatite Gneiss, Quartzite, and Granitic Gneiss respectively in a basement complex of Ibadan, southwestern Nigeria. This was with a view to assessing the pollution potential of the dumpsites on the soil and groundwater in the study locations. Electrical Resistivity methods involving Dipole-Dipole profiling and fifteen (15) Schlumberger Vertical Electrical Soundings (VES) were carried out across two orthogonal traverses established in each of the study locations. A maximum of three subsurface layers namely the topsoil, the weathered layer, and the fresh basement were identified from the geoelectric sections in the three locations. The weathered layer, which constitutes the major aquifer units in the areas and the overlying topsoils were suspected to have been impacted by leachates from the waste dumpsites in the three locations as revealed from characteristic relatively low resistivity values of these layers on the geoelectric sections and the 2D resistivity structures. The hydrochemical analysis of samples from wells in the three locations shows that majority of the analysed cations and anions in the three study locations were within the WHO permissible limits. However, there were indications that parameters such as Pb and Fe2+ in Arapaja and EC, TDS. K+, NO32−, Pb, and Fe2+ in both Apete and Sabo dumpsites were higher than the acceptable limits which revealed possible contamination impacts of infiltrating leachates from these dumpsites on the ambient groundwater in the three locations. This is in agreement with the pollution index rating of these parameters which indicates that they fall within the strongly polluted and seriously polluted classes of 4 and 5. It is further concluded that Arapaja which is underlain by the Migmatite Gneiss rock shows least impact of the infiltrating leachates from the dumpsite relative to other dumpsite locations in Apete and Sabo where the underlying rock types are quartzite and granite gneiss respectively. This can be attributed to the nature of the resulting weathered profile of these rock types which is mostly characterized by impermeable clayey materials in Arapaja and by permeable sandy materials in Apete and Sabo locations.

Geoelectrical exploration of groundwater at West Dayrout Area, Assiut Governorate, Egypt

The study area includes a western limestone plateau with a narrow strip of Nile Valley and extended between Latitudes 27° 27′–27° 43′ N and Longitudes 30° 25–30° 53′ E. The importance of this area increased after the construction of the Dayrout-Farafrah new road. This area was selected from the 1.5 million acre reclamation project. Reclamation depends on groundwater occurrence. So, this research will focus on groundwater exploration. The geoelectrical resistivity method was used for delineating of groundwater occurrence for recommending new localities for drilling wells. Thirty-four Schlumberger Vertical Electrical Soundings (VES) have been carried out with a maximum half current electrode spacing of 700 m. Results of the interpretation through the light of the Eocene aquifer characteristics along the study area indicates that the depth to water in Eocene aquifer varying from 66 to 120 m. and the best area for drilling wells is located in the southwestern, central and southern parts of the study area, where minimum depth to water and maximum groundwater resistivity values within Eocene aquifer are well-represented.

Natural Vulnerability Estimate of Groundwater Resources in the Coastal Area of Ibaka Community, Using Dar Zarrouk Geoelectrical Parameters

The study is aimed at estimating the natural vulnerability of groundwater resources using Dar Zarrouk geoelectrical parameters. Hence, ground-based earth resistance measuring device (OYO McOHM resistivity meter, Model 2115A) and its accessories were deployed for the study. 15 Schlumberger vertical electrical soundings (VES) points distributed along three profiles within the Mbo plain area were conducted. The VES field data were interpreted manually on bilogarithmic plot and then by applying the auxiliary point-partial resistivity curve matching technique. The interpretation was enhanced by sophisticated computer software (IPI2Win). The Dar Zarrouk geoelectrical parameters were deduced from the advanced interpreted results and use to produce contour maps. The lithology identified was of sands sequence of different grain sizes for aquifer zone. The absence of clay formation in the lithology log and low resistivity value (21.49 Ωm) at aquifer’s depth within the VES 5 column suggested saline water ingress. The low range of overburden thickness lies between 0.3 and 4.6 m. The associated overburden longitudinal conductance was found to range from 0.000 to 0.019 Siemens, which was generally low. Therefore, suggesting that groundwater resources in the study area are vulnerable to contamination. Hence, aquifers in the study area were considered to be at high risk of contamination from environmental activities and saline water ingress. The information from study could help in the planning, monitoring and management of potable water supply and development in deltaic coastal aquifer system.

Determination of Maximum Horizontal Distance (XMHD) Travelled by Landfill Leachate from Lapite Dumpsite in Ibadan, Southwestern Nigeria

Abstract This study was designed to determine Maximum Horizontal Distance (XMHD) travelled by landfill leachate. Twenty - nine Schlumberger Vertical Electrical Soundings (VES) were conducted at 10.0m intervals away from four sides A, B, C and D of Lapite dumpsite. One VES point conducted outside the vicinity of the dumpsite served as a control. VES data were processed. Lowest resistivity values (Y) of VES points and the control point (Yc) were extracted. Curves of Y against X fitted best to yield an equation. XMHD was determined from the generated equation when Y = Yc. The determined (XMHD) on the four sides ranged from78.95m to 179.86m.

GEOELECTRICAL ANALYSIS ON THE GROUNDWATER OCCURRENCE FOR THE DEVELOPMENT OF EAST EL MINYA GOVERNORATE, EGYPT

The investigated area is a part of Nile valley which is surrounded by limestone plateaus of Egypt. It is located between Latitudes 28o 15′ - 28o 45’ N and Longitudes 30o 45- 31o 00′ E, and has a surface area of about 1362 Square kilometers. The geoelectrical resistivity measurements have been carried out, using a Schlumberger array to identify the resistivity and thicknesses of different subsurface layers and determine groundwater occurrences. For these purpose, 44 Schlumberger vertical electrical soundings (VES) were conducted with a maximum half current electrode spacing of 700 m. Results from the quantitative interpretation of sounding data indicate that, the area is generally underlain by five main geoelectrical units (A, B, C, D and E). The main characteristics of these geoelectrical layers as well as, the main features of the constructed geoelectrical cross sections have been interpreted in the case of determining the groundwater occurrences. Based on the results obtained, four water-bearing layers (aquifers) were detected in the investigated area. The Quaternary deposits represented by Pleistocene Neonile Sediments of sands and gravels with clay and Shale lenses (A3) act as the first aquifer which represents a limited distribution in the investigated area. The second water-bearing layer (C1) corresponds to water-bearing limestone of Maghagha Formation which lead to the second aquifer and represents also a limited distribution in the investigated area. The third one (D4) corresponds to water-bearing limestone of Samalut Formation which lead to the third aquifer and represents a wide distribution in the investigated area. The fourth water bearing zone (E) corresponds to water-bearing limestone of Minia Formation which lead to the fourth aquifer and represents a wide distribution in the investigated area. Two priority maps for groundwater exploitation in the investigated area have been presented for each of El Minia and Samalut aquifers. It can be concluded that, the priority is generally increasing toward the southern parts, especially at wadi El Saririia area, where El Minia Aquifer occupy the first category and at wadi El Sheikh Hasan where the two main aquifers of Samalut and El Minia facies are well represented

Hydrogeophysical Characterization of Shallow Unconsolidated Alluvial Aquifer in Yenagoa and Environs, Southern Nigeria

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.

Application of geoelectrical and chemical methods for groundwater assessment in Isheri-North, Ogun state, Nigeria

Geoelectrical investigation and chemical analyses were carried out at Isheri North area of Ogun State in order to assess the groundwater quality at shallow depth and its deep potential zone for groundwater development. The study area has been selected for investigation due to infiltration of the polluted Ogun River. Forty-three (43) Schlumberger Vertical Electrical Soundings (VES) and chemical analyses of water samples from one hand dug well and two shallow boreholes in the study area were carried out. Four to five geoelectric layers which correspond to top soil, clayey sand, sandy clay, clay and sand were delineated. The longitudinal conductance values (0.02 - 0.106mhos) of the topsoil in the area reveal its poor to weak protective capacity, thus exposing the underlying clayey sand to contamination as reflected from its resistivity values ranging from 4.8-15.1m. This low resistivity zone at shallow depth (3 – 26m), occasioned by infiltration, was further ascertained by high values of conductivity, turbidity, total hardness, TDS, Cl, Fe, and Mn ions in the analyzed water samples taken at depth ranges from 9 – 16m. The results of the analyzed water samples from this shallow zone are beyond international standards for drinking water. The underlying clay resistivity values ranged between 1.9 - 6.1m and thickness varied from 50.8 - 100.5m. This acts as the seal for the underlying aquifer (sand layer). The resistivity of the sand layer varied from 91.7-159m with a depth interval of 101.7-109.4m and 73.4-82.3m in VES 1 and VES 14 respectively. This constitutes the deep aquifer units in the study area. The longitudinal conductance values of the overburden above the profound aquifer units varied between 10.5-33.0 mhos and are indicative of very good to excellent protective capacity rating. Thus, the underlying deep aquifer units are well protected from being contaminated.Keywords: Electrical Resistivity, Groundwater, Aquifer, Geoelectric Section

Hydrogeophysical Evaluation and Vulnerability Assessment of Shallow Aquifers of the Upper Imo River Basin, Southeastern Nigeria

Detailed hydrogeophysical study of the aquifers of the Upper Imo River Basin, Southeastern Nigeria was carried out to delineate the aquifers, evaluate their geometric characteristics and to assess their vulnerability of pollution from surface contaminants. Forty (40) Schlumberger Vertical Electrical Soundings (VES) were carried out in various parts of the study area with a maximum electrode separation of 1000 metres. Four parametric soundings were carried out at the exact positions of existing boreholes with available pumping test and electric log data for the purpose of comparison. The VES data were processed using a combination of curve matching techniques and computer iterative modeling. Layer parameters interpreted from the VES data together with the available well data were used to assess the vulnerability of the shallow aquifers using the DRASTIC model. Results of the study revealed the presence of 4-7 geoelectric layers with a multi-aquifer system. The aquifers are variable in thickness with Umuekwule having the thickest aquifer of 108m while Ukomo Ibeku has the least aquifer thickness of 1.7m. Similarly, depth to water table varies from 0.6m at Ajata ibeku to 91.8m at Umukabia. Information from iso-resistivity model and diagnostic factor revealed a distinct hydrogeological divide in line with the geology of the study area. The aquifer vulnerability index assessment revealed that about 55% of the study area falls within the moderate vulnerability zones with DRASTIC index values ranging from 102 to 140. About 30% of the study area have high vulnerability index while the remaining 15% of the study area have low vulnerability index with DRASTIC index values of between 85 and 99.

Aquifer Vulnerability Investigation Using Geoelectric Method in Parts of Sapele Local Government Area of Delta State, Nigeria

The electrical resistivity survey has been used in the determination of the overburden protective capacity in Amukpe area of Delta State, Nigeria. Nineteen Schlumberger vertical electrical soundings (VES) were carried out with maximum electrode separation of 1000m. The data were presented as VES curves interpreted quantitatively by computer iteration using the Resist Software to obtain the first order geoelectric parameters. Three geoelectric layers namely the topsoil, laterite/clayey sand and sand (medium to coarse grained) were delineated from the survey. The topsoil has resistivity values ranging from 43 to 1067m and thickness varying from 0.8 to 1.6 m. The second geoelectric layer is composed of clayey sand and laterite with resistivity values ranging from 77 to 644 m and thickness varying from 3.8 to 6.7 m. While the third geoelectric layer represents the aquiferous unit with resistivity values ranging from 200 to 1067 m diagnostic of sand (fine to coarse grained). The interpreted geoelectric data correlated with lithologic logs of a borehole drilled in the study area. The overburden protective capacity in an area was evaluated by utilizing the total longitudinal unit conductance values. The generated longitudinal conductance map showed poor protective capacity (

Predicting Soil Corrosivity along a Pipeline Route in the Niger Delta Basin Using Geoelectrical Method: Implications for Corrosion Control

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 was 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.

Groundwater Exploration in Alakuta-Awotan area of Ibadan, Southwestern Nigeria

Fast growing population of Alakuta-Awotan area of Ibadan has warranted the need to develop the water availability in the area. The area lies within the basement complex terrain of southwestern Nigeria typified by banded gneiss and minor intrusion of pegmatite and quartz vein. This study was carried out to characterize the aquifer units and anisotropic properties of fractures for evaluation of groundwater development in the area. Hydro-geologic investigation was carried out on forty-five wells to study the groundwater system and dynamics in shallow aquifers. This study was integrated with twenty-two Schlumberger vertical electrical soundings to further investigate the different subsurface geo-materials with the aim of delineating the thickness and continuity of the aquiferous zone. Six radial soundings were conducted to study the directional properties of the anisotropic rock and thus indicate the orientation of fractures and extent of the fracturing. Measured static water level and well head varied from 0.8 to 9.9 m and 182 m to 209 m respectively indicating that groundwater generally flow towards the eastern and southwestern parts from two main discharge sites in the northwestern part of the study area. Interpretation of the twenty-two Schlumberger vertical electrical soundings generally shows three layered earth structure notably top soil, saturated/sandy/lateritic clay and weathered/fractured/fresh basement which are mostly of the “H” curve type. Overburden isopach map revealed that the depth to the bedrock varies from 3 to 23 m. The main aquifer (weathered basement) is relatively shallow and most wells in the study area terminate in the second layer. The main water - bearing unit in the area of study is the weathered basement and the fractured basement which are within the second and third geoelectrical layers respectively. The weathered/fractured basement resistivity values vary from 62 Ohm-m and 9807 Ohm-m with thickness values ranging from 2.2 m to 36 m. Polygons produced from six radial sounding showed the predominant structural trends of fractures on the banded gneiss. The radial resistivity survey results show that there is significant anisotropy between 0 - 50 m depth generally striking NE-SW, NW-SE and N-S showing the major structural trend of basement fractures. Coefficient of Resistivity Anisotropy ranges between 1.03 and 1.38. Variation of apparent resistivity is strongest at the eastern and southern parts of the study area with coefficients of 1.33, 1.38, and 1.30. This relatively high coefficient of anisotropy implies higher- permeability anisotropy. The directionality of the trends could be responsible for the depressions in the weathered/ fractured basement. The regions with thick weathered/fractured basement/depressed zones are likely to be most promising sites for borehole drilling.

2D and 3D resistivity inversion of Schlumberger vertical electrical soundings in Wadi El Natrun, Egypt: A case study

Abstract The Wadi El Natrun area is characterized by a very complicated geological and hydrogeological system. 45 vertical electrical soundings (Schlumberger array) were measured in the study area to elucidate the peculiarity of this unique regime, specifically the nature of waterless area. 2D and 3D resistivity inversion based on the finite element technique and regularization method were applied on the data set. 2D and 3D model resolution was investigated through the use of the Depth and Volume of Investigation Indexes. A very good matching was found between the zones of high resistivity, the waterless area, and the non-productive wells. The low resistivity zones (corresponding to Lower Pliocene clay) were also identified. The middle resistivity fresh water aquifer zones were recognized. Available results can assist in the aquifer management by selecting the most productive zone of groundwater.

Delineation of the Aquifer in the Curin Basin, South of Zahedan City, Iran

Resistivity method using 596 Schlumberger vertical electrical soundings along 26 profiles are conducted in the Curin basin, Iran to investigate the sub-surface layering and aquifer characteristics. The results of quantitative and qualitative interpretation of data reveal four layers. The true resistivity of the top soil varies from 3 to 800 ohm-m while the thickness varies from 0.5-15 m. The second layer (dry alluvium) is thicker than the surface layer with resistivity values less than 100 ohm-m. The third layer, which constitutes an aquifer, has resistivity values of less than 10 ohm-m and depth values of less than 30 m in most locations. The maximum depth of aquifer is 60 meters in the northwest and southeast portion of the study area. The fourth layer (bedrock) is characterized by two electric resistivity values ranges. In most parts of the area, it is more than 60 ohm-m, corresponding probably to slate, while in other areas, it is less than 60 ohm-m, corresponding probably to shale. Finally from the quantitative interpretation of VES curves, the limits of the aquifer were determined.