Drill Hole Data Research Articles

Tectonic history and structural development of the Zallah-Dur al Abd Sub-basin, western Sirt Basin, Libya

The Zallah-Dur al Abd Sub-basin area lies in the western part of the Sirt Basin of Libya. 2D seismic data covering an area of about 32,000 km² were studied along with the formation tops from 240 wells. We mapped a complex network of normal and probable strike-slip faults, generally striking NNW-SSE that control the asymmetry of the basin. Subordinate NE–SW structures acted as transverse faults controlling local depocentres that segment the Zallah-Dur al Abd Sub-basin.A number of active faults in the intra-basin area have been identified in seismic sections with generally moderate to high dip angles, and displaying evidence for positive and negative flower structures. The bordering extensional fault (the Gedari fault) passes at depth into a moderately SW-dipping structure crossing most of the Upper Mesozoic to Cenozoic stratigraphic section. Thickness variations adjacent to other major faults suggest also an original extensional system where inherited high-angle faults were reactivated throughout this time.A detailed analysis of the available seismic reflection and drill hole data shows that an obliquely rifted, multi-cyclic, NNW-SSE trending basin developed during the complex Upper Mesozoic Cenozoic rearrangement of Mediterranean tectonics. Multiple phases of rifting can be observed in the study area affecting a number of different horizons from Upper Cretaceous to Eocene.In the study area, the basin was initiated as a result of a Tethyan oblique extensional rift system that began in the Early Cretaceous and peaked in the Late Cretaceous. The basin reached its rift maturation phase during the Upper Cretaceous as a result of the continuing extensional tectonics on the marginal bounding NNW-SSE trending normal growth faults. During the Alpine-related tectonic pulses of Middle–Late Eocene the Sirt Basin underwent compression resulted in northward tilting of the basin, causing abrupt subsidence in the north and uplift on the basin southern shoulders, possibly driving a late stage of minor regional subsidence.

Basalt distribution and volume estimates of Cenozoic volcanism in the Bowen Basin region of eastern Australia: Implications for a waning mantle plume

The volume of Cenozoic volcanism in eastern Australia has been estimated previously from the outcrop extent of basalts, but drill holes have subsequently revealed subsurface volcanic flows with a cumulative thickness of up to 60 m. The magnitude of Cenozoic magmatism is therefore greater than previously thought, necessitating a re-evaluation of basalt distribution and estimates of eruptive volumes. Drill-hole data were collected from across the Bowen Basin in eastern Australia to compile a regional basalt isopach map. This large dataset comprising ∼150 000 drill-hole logs was used to derive minimum extrusive volume estimates of the Peak Range, Springsure and Buckland volcanoes of approximately 2600 km3, 1460 km3 and 860 km3, respectively. The southward decrease in the volumes of these volcanoes, as well as a southward diminishing pattern of eruption rate, most likely arose from waning plume magmatism. We estimate that from ca 30 Ma (the average age of the Peak Range volcano in Queensland) to ca 10 Ma (the approximate age of the Canobolas volcano in New South Wales), the eruption rate in the east Australian central volcanoes decreased by roughly 15 km3/Ma. Additionally, our dataset suggests that basalt flows in portions of eastern Australia filled pre-existing channels with maximum depths ranging from 60 to 220 m, implying an early- to mid-Cenozoic topography of moderate relief.

Planning for Reliable Coal Quality Delivery Considering Geological Variability: A Case Study in Polish Lignite Mining

The aim of coal quality control in coal mines is to supply power plants daily with extracted raw material within certain coal quality constraints. On the example of a selected part of a lignite deposit, the problem of quality control for the run-of-mine lignite stream is discussed. The main goal is to understand potential fluctuations and deviations from production targets dependent on design options before an investment is done. A single quality parameter of the deposit is selected for this analysis—the calorific value of raw lignite. The approach requires an integrated analysis of deposit inherent variability, the extraction sequence, and the blending option during material transportation. Based on drill-hole data models capturing of spatial variability of the attribute of consideration are generated. An analysis based on two modelling approaches, Kriging and sequential Gaussian simulation, reveals advantages and disadvantages lead to conclusions about their suitability for the control of raw material quality. In a second step, based on a production schedule, the variability of the calorific value in the lignite stream has been analysed. In a third step the effect of different design options, multiple excavators and a blending bed, was investigated.

Some Mineral Exploration Problems that can be Solved by Mathematics and Geostatistics

Databases usually consist of information drawn from drill hole and similar data. These data very often present some problems which can be solved by using mathematical and geostatistical methods. The present paper deals with the problems of estimating the proportions of lithological types within selective mining units, the problem ofan addition of new drill-holes in an explored deposit and the results in the estimation of its quality or quantity and the problem of safe sampling of gold deposits (sentence is too long). For the first issue, the paper gives an overview of how indicator kriging can be used to make estimates of the proportions of the various lithology within blocks of ground, given the lithology's occurring in the samples. The paper deals with and answers the questions that arise when evaluating an ore deposit after the completion of a drilling or sampling campaign. With the aid of geostatistics one can justify or reject a supplementary sampling program at the same deposit, with all the consequences of such a decision. One of the problems of the sampling procedures during a mineral exploration campaign is the size and the weight of the samples to be taken. The sample proportions matter especially in case ofa gold deposit, due to the rarity and the high value of the mineral. Using the modifiedGy's sampling formula, this paper presents the mathematical considerations and transformations to eventually produce a mathematical formula that enables the exploration personnel to safely sample a deposit of valuable ore.

Structural and stratigraphic evolution of the Iberia–Newfoundland hyper-extended rifted margin: a quantitative modelling approach

Abstract We investigate the evolution of the Iberia–Newfoundland margin from Permian post-orogenic extension to Early Cretaceous break-up. We used a Quantitative Basin Analysis approach to integrate seismic stratigraphic interpretations and drill-hole data of two representative sections across the Iberia–Newfoundland margin with kinematic models for lithospheric thinning and subsequent flexural readjustment. We model the distribution of extension and thinning, palaeobathymetry, crustal structure, and subsidence and uplift history as functions of space and time. We start our modelling following post-orogenic extension, magmatic underplating and thermal re-equilibration of the Permian lithosphere. During the Late Triassic–Early Jurassic, broadly distributed, depth-independent lithospheric extension evolved into Late Jurassic–Early Cretaceous depth-dependent thinning as crustal extension progressed from distributed to focused deformation. During this time, palaeobathymetries rapidly deepened across the margin. Modelling of the southern and northern profiles highlighted the rapid development of crustal deformation from south to north over a 5–10 myr period, which accounts for the rapid change in Tithonian–Valanginian, deep- to shallow-water sedimentary facies between the Abyssal Plain and the adjacent Galicia Bank, respectively. Late-stage deformation of both margins was characterized by brittle deformation of the remaining continental crust, which led to exhumation of subcontinental mantle and, eventually, continental break-up and seafloor spreading.

Response of fluvial, aeolian, and lacustrine systems to late Pleistocene to Holocene climate change, Lower Moravian Basin, Czech Republic

Late Pleistocene to Holocene Morava River valley-fill of the eastern Czech Republic reflects the geomorphic evolution of the valley as forced by climate change. Valley-fill stratigraphy was studied through measured sections, optically stimulated luminescence (OSL) and radiocarbon dating, ground-penetrating radar surveys of relict sand dunes, archived drill-hole data, and a comparison of elevations and ages of stratigraphic units. Fluvial systems evolved from meandering with floodplains to braided during MIS 3. Braided fluvio-aeolian systems dominated through MIS 2 and the Last Glacial Maximum (LGM). Valley aggradation occurred during arid glacial times of a low water-to-sediment discharge ratio. Most valley-fill was removed at 13ka with incision by a large-bend meandering river with an estimated bankful paleodischarge 3× larger than the modern Morava River. The Holocene Morava River has varied from meandering to anabranching with low rates of floodplain aggradation. The Bzenec sand body, up to 36m thick, represents an erosional remnant bypassed during late Pleistocene incision and consists of interpreted lacustrine turbidites overlain by braided stream and aeolian dune strata. The turbidites consist of laterally continuous, thin, normally graded beds of rounded and frosted sand grains of aeolian origin. Dates and elevation data argue that the valley lake formed during the LGM through downstream damming by a braided terminal fan and sand dune complex. The turbidites are interpreted to have formed through fluvial undercutting and slumping of dune accumulations as lake level rose. This process forced an erosional unroofing of aeolian accumulations, reflected in inverted OSL dates for the turbidites.

Using production data to improve grade estimation in underground mining

All available data should be used to build a geostatistical model. In underground mining, data have different support volumes: drillhole data are defined at a quasi-point support, while production data represent tonnes of ore mined during a period of time (stopes). Due to the support difference, production data are frequently ignored to update the block grade model. We propose a block kriging approach to combine these two sources of information (point and volumetric support data). A synthetic underground mining case is presented. Two estimation scenarios are evaluated: the first considers only drillhole data, while the second considers both drillhole and production data. Results show that the use of production data improves grade estimation. The improvement is more pronounced where diamond drillholes are sparsely located.

Ultramafic and Mafic Rock Distributions in Central Alaska and Implications for CO2 Sequestration

Understanding the distribution of mafic and ultramafic rocks in Interior Alaska provides important constraints on potential economic uses of these igneous rocks, such as future sites for CO2 sequestration. However, poor surface exposure limits understanding of the subsurface geometry and extent of these rocks. In this study, regional aeromagnetic and gravity surveys, geologic maps, drill hole data, physical rock properties, and magnetic data from surface samples were used to build an integrated potential field model that provides a model of the distribution and volume of two of the most significant of these bodies, the mafic and ultramafic rocks of the Tozitna and Livengood Terranes. Although solutions to theoretically calculated geophysical models are non-unique and consequently subject to unquantified uncertainties, our highly integrated model provides a first-order approximation of the distribution of these rocks. Modeling results indicate that mafic and ultramafic rocks in both Terranes are sheet-like, probably thrust-bounded, and continue to significant depths. First approximation volume estimates suggest that there is up to 3,300 billion m3 of mafic and ultramafic rocks between the surface and 3,000 m depth within 10 km of the existing transportation corridor. The maximum carbonation potential of Mg-bearing minerals via a combination of surface and subsurface CO2 injection techniques in these two Terranes is 722 gigatons of CO2. Assuming an actual CO2 uptake capacity of these rocks of only 1 %, this study indicates there is a sufficient quantity of mafic and ultramafic rocks adjacent to existing transportation corridors to meet foreseeable CO2 sequestration needs in Interior Alaska.

Prediction of rock mass along tunnels by geostatistics

A study is made on the applicability and limitation of geostatistical methods in predicting rock mass quality along tunnel alignments based on investigation drillhole data. Two projects were used as the case study: — Lam Ta Khong Pumped Storage Project for a simple geologic setting and Klong Tha Dan Dam Project for a complex geologic setting. The study showed that the estimated rock mass quality and distribution was reasonably comparable with the field observation value for the case of Lam Ta Khong project but it was not the case for Klong Tha Dan Dam site.

A Multiple Training Image Approach for Spatial Modeling of Geologic Domains

Characterization of complex geological features and patterns remains one of the most challenging tasks in geostatistics. Multiple point statistics (MPS) simulation offers an alternative to accomplish this aim by going beyond classical two-point statistics. Reproduction of features in the final realizations is achieved by borrowing high-order spatial statistics from a training image. Most MPS algorithms use one training image at a time chosen by the geomodeler. This paper proposes the use of multiple training images simultaneously for spatial modeling through a scheme of data integration for conditional probabilities known as a linear opinion pool. The training images (TIs) are based on the available information and not on conceptual geological models; one image comes from modeling the categories by a deterministic approach and another comes from the application of conventional sequential indicator simulation. The first is too continuous and the second too random. The mixing of TIs requires weights for each of them. A methodology for calibrating the weights based on the available drillholes is proposed. A measure of multipoint entropy along the drillholes is matched by the combination of the two TIs. The proposed methodology reproduces geologic features from both TIs with the correct amount of continuity and variability. There is no need for a conceptual training image from another modeling technique; the data-driven TIs permit a robust inference of spatial structure from reasonably spaced drillhole data.

IDENTIFATION OF LANSLIDE DIMENSION BASED ON SEISMIC REFRACTION SURVEY IN TENGKILK VILLAGE, KARANGANYAR, CENTRAL JAVA

A seismic refraction survey was conducted at a landslide site, which had destroyed a road and several houses in Tengklik Village, Karanganyar, Central Java, Indonesia. The survey provided insight into the slope stratigraphy, as well as the dimensions of sliding area and depths of the slope failure planes. Field observations and drill-hole data were used to verify the accuracy of seismic refraction data. The seismic velocity measured in the top - sliding layer of sandy silt was less than 900 m/sec, while that in the underlying layer of silty sandstone ranged from 2400 to 900 m/sec. The stable bedrock of andesite breccia underneath the sliding soil layers was about 2500 m/sec. It was apparent that the failure surface was irregular, varies in depth. This failure plane exists at the contact of the andesitic breccia (bedrock) and the sliding layer of silty sandstone. The thickness of the sandy silt ranged from 3 to 5 m at lower part of sliding mass, while at the upper part ranged from 4 to 8 m. The estimated depth of the failure surface ranged from 12 to 24 m. The volume of mass movement is estimated about 111.386 m3 . It was also found that the presence of mountain block at the bedrock of andesitic breccia may resist the movement.

Early Cretaceous construction of a structural culmination, Eureka, Nevada, U.S.A.: Implications for out-of-sequence deformation in the Sevier hinterland

Assessing temporal relationships between foreland and hinterland deformation in fold-thrust belts is critical to understanding the dynamics of orogenic systems. In the western U.S. Cordillera, the central Nevada thrust belt (CNTB) has been interpreted as a hinterland component of the Sevier fold-thrust belt in Utah. However, imprecise timing constraints on CNTB deformation have hindered evaluation of space-time patterns of strain partitioning between these two thrust systems. To address this problem, new 1:24,000-scale geologic mapping and balanced cross sections are presented through the CNTB near Eureka, Nevada, in conjunction with industry drill-hole data, conodont age determinations, and 40 Ar/ 39 Ar and U-Pb ages from volcanic, intrusive, and sedimentary rocks. Our mapping redefines the first-order structures and deformation geometry of the CNTB at the latitude of Eureka. Contractional structures include two north-striking, east-vergent thrust faults, the Prospect Mountain thrust and Moritz-Nager thrust, which are connected as the same fault in cross section, several north-striking map-scale folds, and a Cambrian over Silurian relationship observed in multiple drill holes, corresponding to repetition of ∼2–2.5 km of stratigraphy, that defines the blind Ratto Canyon thrust. Two distinct sets of normal faults cut the contractional structures, and are overlapped by a regional late Eocene (ca. 37 Ma) subvolcanic unconformity. Retrodeformation of both sets of normal faults reveals the existence of the Eureka culmination, a 20-km-wide, 4.5-km-tall anticline with limb dips of 25°–35°, that can be traced for ∼100 km north-south on the basis of Paleogene erosion levels. The culmination is interpreted as a fault-bend fold that formed from ∼9 km of eastward displacement of the Ratto Canyon thrust sheet over a buried footwall ramp. The type exposure of the Early Cretaceous (Aptian) Newark Canyon Formation (NCF) is preserved on top of Mississippian, Pennsylvanian, and Permian rocks on the eastern limb of the Eureka culmination. We propose that the NCF was deposited in a piggyback basin on the eastern limb of the culmination as it grew, which is consistent with published east-directed paleocurrents and provenance data suggesting derivation from proximal late Paleozoic subcrop units. Syncontractional deposition of the NCF is used to define the probable Aptian construction of the Eureka culmination and associated slip on the Ratto Canyon thrust at depth. After deposition, the NCF continued to be folded during late-stage growth of the culmination. Aptian deformation in the CNTB at Eureka postdated migration of the Sevier thrust front into Utah by at least ∼10 m.y. and possibly as much as ∼30 m.y., and therefore represents out-of-sequence hinterland deformation. CNTB deformation was coeval with emplacement of the Canyon Range thrust sheet in the type-Sevier thrust belt in western Utah, and may represent internal shortening of this orogen-scale thrust sheet that acted to promote further eastward translation.

Depth to Basement calculation in Southern Thomson, QLD.

Depth to crystalline basement is a major consideration when conducting minerals exploration. The thickness of sedimentary cover concealing mineralised basement rock is a primary factor in determining whether economic greenfields exploration is viable. A good knowledge of depth to basement is therefore critical for tenement selection and drill hole targeting. New airborne magnetic data released in 2012 allows the calculation of a depth to basement surface in the southern Thomson area adjacent to the Queensland - New South Wales border in south Queensland. Available drill hole data shows basement depths from about 100m to over 3km in the study area but is too sparse to create a reliable surface. A combination of different automatic depth to basement techniques, including Euler deconvolution and Naudy, were used. These techniques were preferred due to a regionally extensive high frequency, low amplitude magnetic signature attributed to shallow sources in one of the cover sequences in the study region. This signature created difficulties for depth to basement calculations which involved the use of higher order derivatives. Geosoft's Located Euler calculation was preferred in areas where remanence was evident as it uses the analytical signal grid. This technique was used in combination with standard Euler. Naudy depths were also compared to the Euler solutions, particularly in areas where the drill holes indicated the basement was relatively shallow (where smoothing associated gridding can cause overestimation of source depths). Seismic data available in the north of the study area was interpreted and used as a secondary (along with the drill hole data) quality control check on the basement surface. The calculated depth to basement surface was used to create voxet model for further analysis using gravity and magnetic inversion. The final depth to basement surface defines an area of shallow basement in the south-west of the study area.

Optimised ore selection from conditionally simulated block models

This study considers realistic data for a planned open-pit iron ore mine, but is applicable to any open pit situation. By interpolating drill hole data, grades are generated for a rectangular block model. Each block’s grade vector has components for each analyte (chemical element or compound) influencing ore value. Deriving the average (E-type) over many simulations leads to each block being assigned its expected value, and thus underestimates the overall grade variability. Alternatively, interpolation by means of conditional simulation is a method that implements random sampling from an infinite population of solutions. Each conditional simulation has appropriate overall grade variability, but estimating any block’s mean and variance requires sampling from multiple conditional simulations. For a block model, an ore/waste selection criterion maximises the expected tonnage at a target grade. This criterion is a linear composite of the grade components, with positive coefficients for the beneficial analyte (Fe) and negative coefficients for the deleterious analytes (such as SiO2, Al2O3 and P). Although conditional simulation often leads to a similar expected grade as kriging for each block, the expected maximum tonnage of ore selectable at a target grade may differ from that obtainable from the E-type solution. We apply the linear composite selection criterion to each of 25 conditional simulations, as well as to the E-type block model. Simulation confirms the distribution of product tonnage to have an expected tonnage that is over 20% greater than that of the E-type model. The method also enables a selection probability to be computed for each block, and thus a probabilistic pit boundary distribution to be identified and used in mine planning. Proposed extensions to this method will consider risk-based scheduling of the multiple selection solutions through minimisation of a derived stress factor and treating the mining process as an iterative system with actual or artificial depletions modelled in line with the mine plan, using the updated state (with new information) to re-evaluate the mine plan for subsequent periods.

Characterisation and 3D modelling of a nuggety, vein-hosted gold ore body, Sunrise Dam, Western Australia

In high-nugget gold ore bodies, samples taken from drill core for gold assay are typically too small to allow for the extreme spatial variability in grade and are a poor representation of the underlying distribution of mineralisation. The GQ North lode at the Sunrise Dam Gold Mine in Western Australia is a good example of an orebody which has a very strong nugget effect (coefficient of variation >20) and that has proved very problematic to model. Gold is hosted in vein stockworks and shear zones and although there is a clear spatial relationship between mineralisation and alteration, high vein density and well-developed foliations, the relationship is best defined statistically because the association between high gold grades and various combinations of these features is non-trivial. We present a method for automating the inclusion of geological data (proxies for gold mineralisation) into the prediction of mineralised rocks, using conditional probability. The method uses the gold assays and the logged geological data to calculate the probability that rocks with particular geological features will be mineralised. The ore body can then be modelled automatically using interpolation software with isosurfaces indicating the regions with highest probability of gold mineralisation. A good understanding of the geological features associated with mineralisation and consistent geological logging are important prerequisites for successful conditional probability modelling of drill hole data.

Preparation for drilling well IDDP-2 at Reykjanes

Preparation has begun for drilling the second deep IDDP well into the saline Reykjanes high-temperature field in SW-Iceland. The site selection for the IDDP-2 drillhole is under review and the prime candidate is essentially the same as the 1st priority site suggested for the Reykjanes field in 2003. More recent drillhole data and new MT surveys have amplified the justification for selecting that site. Deep drilling to 4–5km depth is an important part of the HS Orka exploration strategy for enhanced power production, either by direct use of high energy steam, or by attempting to enhance the field performance by re-injecting geothermal fluid deep into very hot rocks. Pending on several decisions and development in Iceland, outside the control of the IDDP energy consortium, the IDDP-2 well might possibly be drilled to 4–5km depth as early as 2014.

Sedimentary cover in the South Western Desert of Egypt as deduced from Bouguer gravity and drill-hole data

The Western Desert, Egypt includes the major groundwater aquifer in the country. It is apart from the Major Sahara Nubian Aquifer which is present in Sudan, Chad, Egypt and Libya. Thickness of this aquifer is changed laterally from south to north and also from west to east. The changes may structurally or litheologicalley control. The present study is focused on using of Bouguer gravity anomaly mapped at a scale of 1:500,000 and the lithological logs of about 120 deep wells used to determine the thickness of the sedimentary sequence containing the main Nubian sandstone water aquifer in important area of Egypt. The area is located in the southern part of the Western Desert bounded by the latitudes 22°00′–26°30′N, and longitudes 28°30′–33°00′E. The predominant structures affecting the basement rocks and the sedimentary cover were traced and analyzed. The gravity stripping approach was applied to eliminate the gravity effects caused by sedimentary sequence and to separate density anomalies within the sedimentary fill from the influence of rocks at deeper levels in the crystalline crust.The study indicated that the surface of the basement rocks is highly rugged and mostly controlled by structures which have a direct effect on thickness variation of the sedimentary cover all over the area. Regionally the area is characterized by two major intracratonic basins (the Dahkla Basin and the Nile valley Basin) separated by a NE–SW trending swell of the Kharga uplift and bounded at the south by the Oweinat–Bir Safsaf–Aswan uplift. These major tectonic units are controlled by fault structures trending in N–S, E–W, NE–SW, NW–SE, which cut the basement rocks and extend upward in the sedimentary cover. The maximum thickness of sandstone formations is recorded at west Oweinat, west Kurkur, southwest of Aswan, Gramashin, Dakhla oasis and some localities west of Sohag and Qena towns. At these localities the thickness ranges between 600 and 900m. As this formation is the main water aquifer in the study area, therefore these localities are characterized by the presence of big amount of ground water. Accordingly, these areas must take the priority in the sustainable development programs of southern Egypt.

Palynology, Stratigraphy and Geometry of the Pennsylvanian continental Santa Susana Basin (SW Portugal)

The continental Pennsylvanian Santa Susana Basin (SSB) is located along an important N-S strike shear zone (Santa Susana Shear Zone - SSSZ) that separates the Ossa-Morena and South Portuguese Zones (SW Portugal). This shear zone controlled the sedimentation of the basin and probably its post-sedimentary evolution. The lower (basal) unit is mostly conglomeratic and is known essentially from drill-hole data while the upper unit, that covers most of the current surface area, is composed by sandstones, shales and some coal beds. Fluvial sedimentary rocks seem to prevail, but evidences of lacustrine sedimentation can be found in restricted areas within the upper unit. Palynological data indicate that at least part of the sedimentation took place during the Early Kasimovian (Cantabrian) but the sporomorph content of different localities suggest that significantly older sediments (Late Moscovian -Early Bashkirian) may be present. Geometrical, structural, and cartographical evidences indicate that the SSB formed as a pull-apart basin along the SSSZ and was later partially uplifted during latest Varsican and Alpine orogenies.>

Geomorphological site classification for the Fujian province

Geomorphological classification of the Fujian province was done based on remote-sensing imaging, digital elevation maps, and slope gradient data acquired by ArcGIS 9.2. The engineering geological units in the Fujian province were divided into five types by the geomorphologic shape and genesis. The relationship among geomorphological type, engineering geological unit, and site category was determined using engineering geological data and site category data. Then, after making a preliminary site classification adjusted by drill hole data, the site was classified into four types: I0, I1, II, and III according to site classification standards of equivalent shear-wave velocity and overburden thickness. The results showed that the site categories in the Fujian province mainly consist of type II, which accounts for 85.26 % of the land area. The percentage of I0 was the smallest, which accounts for only 2.44 % of the total area.

Thickness variation of the sedimentary cover in the south Western Desert of Egypt as deduced from Bouguer gravity and drill-hole data

Bouguer gravity anomaly mapped at a scale of 1:500,000 and the lithological logs of about 120 deep wells were used to determine the thickness of the sedimentary sequence containing the main sandstone water formation in important area of Egypt. The area is located in the southern part of the Western Desert bounded by the latitudes 22°00′–26°30′ N, and longitudes 28°30′–33°00′ E. The predominant structures affecting the basement rocks and the sedimentary cover were also studied. The gravity stripping approach was applied to eliminate the gravity effects caused by sedimentary sequence and to separate density anomalies within the sedimentary fill from the influence of rocks at deeper levels in the crystalline crust.The present study indicated that the surface of the basement rocks is highly rugged and mostly controlled by structures which have a direct effect on thickness variation of the sedimentary cover all over the area. Regionally the area is characterized by two major intracratonic basins (the Dahkla Basin and the Nile valley Basin) separated by a NE–SW trending swell of the Kharga uplift and bounded at the south by the Oweinat–Bir Safsaf–Aswan uplift. These major tectonic units are controlled by fault structures trending in N–S, E–W, NE–SW, NW–SE, which cut the basement rocks and extend upward in the sedimentary cover. The maximum thickness of sandstone formations is recorded at west Oweinat, west Kurkur, southwest of Aswan, Gramashin, Dakhla oasis and some localities west of Sohag and Qena towns. At these localities the thickness ranges between 600 and 900m. As this formation is the main water aquifer in the study area, therefore these localities are characterized by the presence of big amount of groundwater. Accordingly, these areas must take the priority in the sustainable development programs of southern Egypt.