الفهرس 
Geologic and Hydrogeologic SettingsOnly 14 pages are availabe for public view
Abstract
Summary, Conclusions and Recommendations
The area under study of West El-Minia is bounded between latitudes 28o 00\ 00\\ to 28o 30\ 00\\ N and longitudes 30o 05\ 0\\ to 30 o 30\ 00\\ E and, it has been studied in different aspects. Geologically, the area basically consists of two formations are Samalut Formation, which made up of limestone with shale intercalations underlined by El-Minia Formation, which also consists mainly of limestone, as well as Oligocene clastics, that made up of sand, gravel, with clay intercalations. Structurally, this area was subjected to intense uplifting, that is obvious in the ground elevations through the study area and the topographic features. from the previous hydrogeological studies, there are three main aquifers. They are Oligocene clastic aquifer, Carbonate aquifer and Nubian Sandstone aquifer. This study focuses on studying and exploring the Oligocene and Eocene carbonates aquifers as shallow and deep aquifers. The Eocene carbonate aquifer is considered the main shallow and deep aquifers and more extended than the Oligocene aquifer across the study area.
At this study, the DC- resistivity method and the Time-Domain Electromagnetic method were used, as surface geoelectrical methods for exploring the previous shallow and deep groundwater aquifers and for estimating their geological and hydrogeological characteristics along the study area. The DC resistivity method in the form of 22 Vertical Electrical Soundings (VESs), using Schlumberger array configuration, with max AB/2 700m, were carried out for studying the shallow resistive depths, delineating the shallow groundwater aquifer (Oligocene aquifer) and the shallow depths from the Eocene aquifer, add to exploring the expected structural faults. The results of shallow DC resistivity soundings were integrated with the deep electromagnetic method (TEM) results, which are used for studying and detecting the shallow and deep water-bearing conductive layers (aquifers), where 12 Transient Electromagnetic Soundings (TEMs) were carried out, using the in-loop array configuration in the form of square loop, with side length of 200m.
The geoelectric characteristics of the implied aquifers were estimated, using the forward and inverse modeling for interpreting the measured data from the VES and TEM soundings. The applied initial model of the resistivity data from VESs was obtained, using the automatic multi-layers interpretation technique of Zohdy,(1989(. Then, this model was used as a forward model for Rinvert software (1999), to get the inverse model in the form of actual layers model, including the resistivities, thicknesses and depths of the recorded subsurface geoelectrical layers. While in case of interpreting the TEM data, Steminv software was used to get the smoothed model, which is considered as a forward model and the Tcinv software to get the final inverse layered model. The interpretation of the previous measured data from the two methods was controlled by the accuracy in data measurements, the available subsurface data from the drilled wells and the well logging data, as well as the hydrogeologic data.
The faults, as interesting structural event, were identified, using the structural geologic map, the layers resistivities and the surface and subsurface geologic setting, as well as using the new assumptions of Ammar and Kamal (2018), which depend upon the calculated resistivity curves. from applying these assumptions, it is found that, they were good for determining the existence and absence of faults between any two adjacent VESs, taking into account the change in geological facies. The results of this method were calibrated with the structural geological map of the study area as it showed that, there is agreement between the determined faults from the geologic studies and this technique showing the surface and subsurface faults and their continuity across the study area. Accordingly, there are several faults dissecting the study area. These faults were very interesting in reflecting the hydrogeologic conditions of the aquifers, which are complicated and they effect on the groundwater levels, and also on the groundwater flow through the area. It was believed that, the groundwater of this aquifer is delivered from the underlying deep Nubian sandstone aquifer through faults, as a result of the extensive pressure on it, as Nubian aquifer is considered confined to semi-confined aquifer.
All the results, from interpretation of the VES and TEM soundings, were contoured and translated into hydro-geoelectric sections for simulating the resistivity values of the resistive and conductive layers horizontally and vertically with depth. These results were integrated to show the resolution of the shallow section and the deep section. where the DC-resistivity method give good resolution in the shallow resistive and conductive depths, while the TEM method give good resolution and high sensitivity to the shallow and deep conductive depths. In addition, that the Ramp-off time affects the measured data from the TEM method for investigating the shallow resistive depths and the depth of investigation (diffusion depth), due to the interference of the resulted primary magnetic field and the secondary component, the magnetic field in the early time of receiving TEM response, as well as the effect of the shallow considerable thickness of high resistivity.
In general, from the interpretation of the previous geoelectric soundings, four geo-electrical layers were identified. They are from upper to lower dry Oligocene clastics characterized by resistivity values ranged from 173 to 467 Ωm, dry limestone characterized by resistivity values varied from 273 to 374 Ωm, saturated Oligocene clastics characterized by resistivity values ranged from 2 to 107 Ωm (Oligocene aquifer), then saturated fractured limestone to shally limestone characterized by resistivity values varied from 5 to 188 Ωm (Eocene carbonate aquifer). The estimated depths to the groundwater were ranged from 62 m to 131m, depending on the ground elevations. These depths were matched with the available measured depths from the drilled water wells at the study area.
Also, the iso-resistivity and isopach maps of the recorded layers across the study area were drawn, to delineate the increasing and decreasing resistivity and thickness of these layers, with focusing on the conductive layers. However, the resistivity values indicated that, the shale content at the limestone layers increases toward the northwestern parts. The thickness of the Oligocene clastics increases toward the southern and southwestern directions, and it disappears toward the northern direction.
For confirming the previous results, well log data were collected in the study area, to focus on the depths to groundwater. There are two wells have well logging data, including Gamma-ray log, short and long resistivity logs and caliber log at the limestone aquifer of the first well, while the other well includes Gamma-ray log, single point resistance log, self-potential log and short and long resistivity log at the Oligocene aquifer. There logs were interpreted, using Tech-log software, that reveal and determine the saturated zones, the volume of shale and the porosity values, utilizing both Archie’s and Humble’s formulas for the Oligocene aquifer and the carbonate aquifer.from the analysis of the logs at the two wells, the volume of shale was ranged from 0% to 100% at the carbonate and Oligocene aquifers. The porosity in the Oligocene aquifer varies from 9% to 35%, while the porosity of the carbonate aquifer ranges from 4% to 15.5%. These values are controlled by increasing and decreasing the clay or shale content, and the sand and gravel, as well as the fractures density.
Also, the priority maps were built up based on the resistivities and depths to groundwater. The area can be classified into five categories, from 1 to 5. The first category is the (1st) order in drilling the groundwater production wells, while the fifth category is the (5th) order, that considered the last rank in drilling the water wells. This classification depends upon the resistivity values, which reflect the increase or decrease in clay or shale content, and also the values reflecting the decrease and increase of the fractures density.
Finally and according to the previous results, it can conclude the following;
The rule of forward and inverse modelling is a very powerful tool for interpreting the VES and TEM soundings.
The use of the new assumptions by Ammar and Kamal (2018), in detecting the inferred faults, is a very good approach for confirming the existence or absence of the faults between the measured VESs, using the field or calculated resistivity curves.
The use of low ramp transmitter, which can be low as 2.5 μs, is more preferable in identifying the shallow depths, especially at the parts of high resistive shallow depths,
The accuracy in the results of investigation through using the surface geophysical methods depends upon the accuracy in measurements, understanding how to use the forward and inverse modelling in the interpretation, with assisting the available subsurface geologic and hydrogeologic data.
Four geo-electrical layers were identified. They are from upper to lower dry Oligocene clastics characterized by resistivity values ranged from 173 to 467 Ωm, dry limestone characterized by resistivity values varied from 273 to 374 Ωm, saturated Oligocene clastics characterized by resistivity values ranged from 2 to 107 Ωm (Oligocene aquifer), then saturated frplanactured limestone to shally limestone characterized by resistivity values varied from 5 to 188 Ωm (Eocene carbonate aquifer).
The estimated depths to the groundwater were ranged from 62 m to 131m, depending on the ground elevations.
For drilling a productive groundwater wells across the study area, this should depend on the arrived priority map, taking into account the categories from the 1st order to the 5th order.
The development in the study area should depend mainly on the reservoir properties and on the pre-established priority plan.