Anomalous seepage and groundwater accumulation in the basements of shops and houses in Jodhpur City, Rajasthan, are weakening foundations and reducing the lifespan of buildings due to damp walls and erosion. Therefore, identifying favourable fractured zones for groundwater seepage becomes crucial in this area. To investigate groundwater seepage flow paths, integrated geophysical surveys were conducted using self-potential (SP), geo-electrical resistivity, and very-low-frequency (VLF-EM) electromagnetic methods. Seventy-one vertical electrical soundings (VES) were carried out, along with three SP and three VLF profile lines using the Schlumberger array arrangement. The SP anomalies indicate groundwater flow through fractured formations. Geoelectrical and VLF cross-sections revealed the presence of fractured and semi-fractured rhyolite at depths ranging from 10 to 45 metres. The integrated results demonstrate that groundwater seepage flow paths are influenced by joints, cracks, and fractured zones, serving as conduits for groundwater flow in the study area.
Integrated site investigations using VES techniques, SPT, borehole drilling, soil moisture content and specific gravity have been conducted at LFTZ, Lekki, Lagos, Nigeria. VES results correlated with borehole data revealed a lithological sequence with maximum five geoelectric layers. Inferred lithologies include low/moderate resistivity (45.6–206.3 Ωm) topsoil of sand/silty sand followed by a succession of silty sand/sand layers to a depth of about 45 m. Low depth silty sand (resistivity <300 Ωm) is the prevalent soil in the second and/or third strata and sand (resistivity >300 Ωm) is the last layer across the traverses. SPT results correlate well with borehole data showing a subsurface lithological sequence of very loose/loose grading silty sand, loose/medium dense grading silty sand, medium dense/dense grading sand and dense grading sand. Soil density Increases downward in boreholes with SPT N-values (2–24). Grain size distribution curves depict uniformly graded/narrowly graded soil aggregates with Cu and Cc in the ranges 1.33–8.00 and 0.610–2.00, respectively. Moderate moisture content values (16.72–27.82) suggest that the water table is close to the surface toward the nearby Atlantic Ocean. Specific gravity values (2.60–2.78) lie within the range for most soils and indicate that salinity is minimal at the study location.
The assumption that the presence of high seismic amplitude anomalies is mainly due to gas saturation has significantly contributed to drilling failure in "Taadoy" Field. To mitigate failure due to seismic amplitude anomalies, it is imperative to analyse the possible presence of tuning effect in high seismic amplitude anomaly in this field. Seismic to Well tie was used to identify reservoir "Res 500". Presence of hydrocarbon anomaly was determined using seismic amplitudes cross-plot and attribute analyses. Rock Physics Template (RPT) helped to substantiate the presence of gas in the thin sand and acoustic impedance inversion revealed minimal impedance contrast between encasing shale and "Res. 500". Wedge model revealed that reservoir "Res. 500" is 10 m thick while the RPT analysis estimated gas saturation of 25%. This implies that the high seismic amplitude anomaly is due to both gas presence and thickness of the reservoir. Amplitudes Variation with Angles (AVA) response indicated high seismic amplitudes at the top and base of the reservoir. The presence of gas causes high seismic amplitude and gradient trends especially at far angles but with minimal effect with increased gas volume. Superposition of seismic amplitudes due to both gas presence and tuning effect produced the high seismic anomaly observed in Res. 500 reservoir.
An integrated geological and geophysical study utilising electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) was carried out in a new residential area located northeast of New Cairo City and south of the Suez-Cairo Road. The purpose was to characterise the subsurface layer distribution, lithology, and geometry of faults . Initial surface geological mapping identified traces of some faults. Stratigraphically, the study area comprises sedimentary rocks and local basaltic flow outcrops ranging in age from the Middle Eocene (Mokattam Formation) to the Upper Miocene (Hagul Formation). ERT and SRT data were acquired along 15 closely spaced profiles oriented to intersect the expected surface fault zones. ERT delineated electrical conductive zones situated at different depths and composed of shale and altered basalt. Meanwhile, three layers were detected based on velocity values obtained from SRT data analysis. The ERT and SRT results successfully elucidated the fault configuration and its locations, providing crucial information for construction planning. Major structures were concealed and only outlined by the integrated ERT/SRT surveys. This study shows heterogeneous soil conditions and fault damage zones, which may impact some parts of the study area. The study's findings , offering vital information for safe and effective construction planning.
An evaluation of subsurface contamination in the Farri dumpsite area of Ogun State, Southwestern Nigeria, has been carried out with the aim of determining the degree of contamination and infiltration of leachate into the subsurface soil using the vertical electrical sounding (VES) method. Twenty VES points were probed using the Schlumberger array with a current electrode spacing (AB/2) of 80 m. The resistivity values recorded were processed via the partial curve matching approach, and modelling with WINRESIST software was employed to generate the geoelectric parameters of the subsurface. The interpretation of the data obtained shows the presence of three underlying lithological layers with Q and H geophysical curve type geometry. The lithological layer present in the study area includes topsoil, clayey, sandy clayey and compacted sandy layer with resistivity values ranging from 10.9 to 1091.3 Ωm, 11.4 to 110.9 Ωm, 141.7 to 275.6 Ωm and 1293.7 to 9880.9 Ωm. Overburden thickness varies from 0.5 to 3.2 m across the study area. Three contamination categories (uncontaminated, moderately contaminated and contaminated) were adopted for rating contamination. The geospatial representation of the calculated longitudinal conductance shows that the protective capacity is low in the northwestern part, moderate within the central region, and high in the southeastern and southern parts of the study area.
This study is intended at depicting the aquifer plausible zones in Modomo/Kajola, Ile-Ife using Dar Zarrouk parameters. The study area is situated amid latitudes 830,00–830,500 mN and longitudes 663,500–664,000 mE, overlying pegmatite and granite gneiss in the basement complex terrain. Twenty-eight (28) Schlumberger-array vertical electric soundings (VES) were carried out within the study area with the help of Terrameter SAS 300C. The VES interpretation result reveals three to five geo-electric layers: topsoil, clay/sand/lateritic layer, weathered layer, fractured basement, and fresh basement. The geoelectric sections showed the main aquifers to be unconfined, semi-confined, and confined composed of sandy clay, clayey sand, and sand with different thicknesses (aquifer thickness varying from 3.3 m to 15.8 m with a mean value of 9.9 m). The aquifer hydraulic characteristics show that the longitudinal conductance ( L ) varies from 0.014 Ωm to 1.000 Ωm with a mean value of 0.132 Ωm, the transverse resistance ( T ), varies from 677.4 Ωm2 to 6465.7 Ωm 2 with a mean value of 2291.2 Ωm 2 . The Hydraulic conductivity ( K ) values vary from 29.4 m/day to 126.9 m/day with a mean value of 50.5 m/day. The transmissivity ( T r ) values attained at many layers vary from 418.7 m 2 /day to 465.1 m 2 /day, with a mean value of 449.4 m 2 /day. The GSLI values vary from 2.25 to 4.25 with a mean value of 2.9. Three aquifer plausible zones were depicted involving sandy clay, clayey sand, and sand.
The goal of this research is to develop a new, fast-applying, non-conventional 2D semi-inversion technique that uses data from a previously known control point (e.g. a borehole). The method successfully separated a digitised profile over the Bouguer gravity anomaly map into its components, each of which corresponded to a rock formation being prior chosen from a borehole or control point. The importance of this technique stems from its capacity to automatically analyse the shape of the Bouguer gravity anomaly, as well as its propriety, approximation and given accepted equivalent geological cross-section, utilising an infinite slab model. A preliminary synthetic guidance model (SGM) in this proposed new method is being created from borehole data to simulate the homogeneous density distribution of the rock formations that fill a hypothetical sedimentary basin so that it represents to far extent the history of the region's sedimentation process. The theoretical gravitational effect for each rock formation is estimated using the infinite horizontal slab model for all rock formations of such a hypothetical basin model. The total of these gravitational effects is utilised to invert any gravity profile that crosses the Bouguer gravity anomaly map. The gravity anomalies of the Bouguer profile are then separated and inverted into the comparable rock formation thicknesses or/and depths tracked along the gravity's profile using a simple method. The technique was tested on a synthetic model, a synthetic noisy contaminated model, and real data from two different field cases with different geological and lithological characteristics. The first was in the Tucson Basin in Southeast Arizona, USA, and the second on the Mors Salt Dome in North Jutland, Denmark. The method has demonstrated results comparable with prior known information of the borehole existing in the study areas.
This study aims to estimate the effect of the resolution of the available Digital Height Models (DHMs) on the reduced gravity anomalies and the final computed gravimetric geoid. The region of Egypt is taken to be a prototype test. Different available DHMs are used in this study. The window technique has been used for gravity reduction (Abd-Elmotaal and Kühtreiber 2003). The reduced gravity anomalies are used to compute geoid undulations in each test case employing the 1D-FFT technique. The comparison among the results has been carried out at two levels: the reduced gravity anomalies and the discrepancy in geoid undulations. The results show that using fine DHM with a resolution of 3′′ x 3′′ or using fine DHM with a resolution of 1′′ x 1′′, with a coarse DHM with a resolution of 30′′ x 30 ′′, gives approximately the same results according to the range and the standard deviation. On the other hand, applying 3′′ x 3′′ DHM resolution saves about 80% of the central processing unit (CPU) time necessary for the reduction step. The results show that the difference between the indirect effect in the case of fine DHM 1′′ x 1′′ and the case of fine DHM with a resolution of 3′′x 3 ′′ is very small (about 1 cm). This means that going to 1′′ x 1′′ DHM is not needed for the test region as 3′′ x 3 ′′ can save time and effort and give approximately the same results in both gravity reduction and geoid computation. Finally, it can be concluded that using fine DHM with a resolution of 1′′ x 1′′ and coarse DHM with a resolution of 30′′ x 30′′ are adequate for determining the gravity anomalies and gravimetric geoid for Egypt.The geoid undulation differences between the GPS/levelling points of HARN and our developed geoid provide improvements by about 10 cm concerning the geoid computed from EGY-HGM2016 model . These improvements are considered to be important when we are seeking about 1 cm geoid.
In this work, a fast method of representation of the basement-sediment contact in a sedimentary zone is presented. The proposed approach is based on the polygonal model and stacked rectangular prism model. This approach consists of separate the Bouguer anomaly into regional and residual ones by using the polynomial method to better locate the sediment deposits. Then, 2D gravity modelling of several profiles plotted on the residual anomaly map is done. The data collected from these models are interpolated by the geostatistical method of Kriging to obtain the model of the basement-sediment contact of the study area. The feasibility and reliability of the proposed approach are demonstrated on synthetic data produced by a prism, and satisfactory results have been obtained. The inversion of real gravity anomalies is presented as a practical example to get a better view of the basement-sediment contact of the transition zone between the Benue and Lake Chad basins. The obtained 2D and models show that the sediment deposits are mainly constituted of sandstones. The maximum depth of these sediments is 5.5 km around the locality of Lagdo. In addition, these sedimentary deposits are less deep and almost absent in the north of Garoua, Bibemi, Kaele and Maroua.
Exploration of new geothermal systems often requires regional-scale investigation. Satellite Land Surface Temperature (LST) products are essential in geothermal anomaly identification and mapping. In this study, seven thermal anomalies covering Egypt were observed using the Sentinel-3 LST images acquired in 2019 and confirmed using the 2020 LST images. In addition, the LST analysis reveals three new anomalies covering the southern part of Egypt (Kalabsha, Natash, and Wadi Allaqi), which are structurally controlled. Nuqra-Kharit-Natash is a good site for geothermal energy owing to the following reasons: 1) the high geothermal gradient beneath the Wadi Natash region (heat flow ~100 mW/m2); 2) the presence of many geothermal anomalies retrieved from the analyses of the Landsat-8 acquired in August 2018; 3) existence of surface geothermal manifestation at the western boundary of the basin includes warm springs and the tufa deposits. Intricate structural patterns, including NW-oriented normal faults, ENE-to-WNW-oriented right-lateral faults, and NNE-oriented sinistral strike-slip faults, characterise Wadi Natash. Wadi Natash LST anomaly shows a solid relation to fault trends. High values of LST are arranged along NW and NNE faults and recorded the peak at the intersection of two fault trends. Recent seismic activity along the NNE fault system enhances the permeability along this trend and its intersection with the NW-oriented fault.
This study analysed the depositional environment and diagenesis of the ASL Member reservoir in the October oil field located in the Gulfof Suez Basin, Egypt. Sedimentological and petrophysical techniques were used to interpret data from four wells: OCT-J7B, GS173-2, GS184-4A, and GS195-3, penetrating various rock types, including sandstone, carbonate, and fractured basement reservoirs. Log correlations of OCT-J7B and GS173-2 showed they penetrated pre-Miocene strata, while GS184-4A and GS195-3 reached the Rudeis section. Based on seismic-based structural maps, all wells except GS173-2 were drilled down-dip of the main Clysmic fault. The Hawara shale and the older shales in the Rudeis section were found to be the reservoir’s lateral seal, and the Lagia shale was found to be its vertical seal. Core analysis of OCT-J7B revealed the ASL as limestone interbedded with shale and sandstone deposited in a proximal submarine fan lobe, while GS184-4A and GS195-3 were located in amid-fan carbonate system. The comparisons of core and log data from the four wells yielded excellent matches, and the iso-parametric mapping delineated reservoir quality horizontally and hydrocarbon potentiality. The study recommends sitting future wells away from uplifts and suggests further reservoir characterization and evaluation of potential zones in the ASL Member.
To interpret geological structures, edge detection is a crucial step. Thus, high-precision computing of the boundaries of possible sources is evolving a necessity to study the subsurface structures. In this study, the tilt-angle, the Tilt-Angle of the total-horizontal gradient, the Tilt-Angle of the Tilt-Angle gradient, and Improved Logistic filters were applied to aeromagnetic data from Gabal Ineji data, South-Eastern-Desert of Egypt. The results have been used to give more precisely accurate structural maps, particularly when compared to revealed geological structures. that gives reliable interpretations. The utilised methods showed that the NW-SE and N-S trends play an effective role in formulating the structural setting of the research area.
