Abu Gharadig Basin Research Articles

Khatatba Formation as an active source rock for hydrocarbons in the northeast Abu Gharadig Basin, north Western Desert, Egypt

Rock samples and a suite of oil samples collected from wells drilled in the northeastern part of the Abu Gharadig Basin were studied to determine the petroleum potential of the Middle to Late Jurassic Khatatba Formation as a source rock for oil produced in the basin. Twenty-four cuttings and two cores in addition to three oil samples from the Riviera-1, Swag-2, and Spyglass-1 wells retrieved from the Upper Cretaceous reservoirs were analyzed. Analyses include total organic carbon (TOC), Rock-Eval pyrolysis, and vitrinite reflectance for rock samples and biomarker analyses for liquid hydrocarbons. Results reveal that the Khatatba Formation is an organic-rich source rock with TOC ranging from 1 to 5 wt%, locally exceeding 21 wt% due to the presence of coal interbeds in the depth interval 4,386–4,388 m. Rock-Eval pyrolysis data show that the Khatatba Formation is dominated by algal type II and mixed type II/III kerogens, but type III and type I kerogens also occur. The Khatatba shales and carbonaceous shales have entered the peak-mature stage of the oil generation window. Tmax for the samples ranges from 436 to 449 °C and vitrinite reflectance measurements between 0.76 and 0.92 %Ro. Geochemical analyses reveal that all analyzed oils were generated from thermally mature and organic-rich shale and carbonaceous shale belonging to Middle–Upper Jurassic and Lower Cretaceous source rocks during early and peak stages of the oil window. The correlation between oil samples from NE Abu Gharadig Basin shows that these oils are quite similar and were generated from mixed marine–terrigenous organic matter formed under suboxic–oxic depositional paleoenvironments. However, the differences in bulk and biomarker properties and light-end content of the oil samples can be attributed to thermal maturation, source rock facies variations, or secondary reservoir transformation, such as evaporative fractionation.

Seismic and sequence stratigraphy of Upper Cretaceous–Tertiary succession, eastern Abu-Gharadig Basin, Western Desert, Egypt

This work deals with the sequence stratigraphy of the subsurface Upper Cretaceous and Cenozoic succession of the eastern Abu Gharadig Basin in the Western Desert of Egypt. The micropaleontological inspection of the cuttings from four wells: WD14/1, East Mubarak-1, East Mubarak-2, East Mubarak-3, revealed 23 foraminiferal biozones and six calcareous nannofossil zones and the presence of several hiatuses. The information obtained from biostratigraphic analysis, well data and seismic interpretation for the studied area has enabled the classification the Upper Cretaceous and Cenozoic succession into five major depositional sequences and these units were then correlated with those recorded in the north Western Desert and elsewhere Most of the major sequence boundaries and the unconformity surfaces inbetween compared well with those of Kharga Oasis, Farafra Oasis, the global cycle chart of Haq et al. (1988), the Western European sea-level curve of Hardenbol et al. (1998) and with the sequence boundaries, flooding surfaces and the sea-level curve of Haq and Al-Qahtani 2005, indicating that most of them are caused by global eustasy and some of the sequence boundaries are related to local tectonism. Three of the identified Upper Cretaceous-Cenozoic major sequences coincide with those of Haq and Al-Qahtani 2005 along the Arabian Platform, while two of them were formed due to local tectonic events.

Palynofacies and paleoecology from Abu El Gharadig – 4 well, Northern Western Desert, Egypt

Abd El Hakam A. Baioumi and Medhat M. M. Mandur Egyptian Petroleum Research Institute (EGYPT) Abdelhakam.bayomi@yahoo.com DOI: 10.7813/2075-4124.2013/5-2/A.3 ABSTRACT Kharita and Baharyia Formations Northern Western Desert, Egypt are characterized by presence of maximum flooding surface and supported by presence of glauconite, underlain by transgressive system tract and overlain prograditional parasequence sets. Moreover, upper part of Kharita and Bahariya formations represent start of agraditional phase. Composition of dispersed sedimentary organic matter SOM shows presence of three main groups.These include amorphous organic matter group, palynomorph group. The cluster analysis of sedimentary organic matter SOM reveals presence of two palynofacies groups AB palynomorph group is present in waxing quantity of cluster C. From previous data results include to environment of deposition is ranged between low to moderate energy fluviomarine to shallow marine environment. Key words: palynofacies, paleoecology, Northern Western Desert 1. INTRODUCTION This study deals with palynofacies of 4 core samples representing Kharita (Middle – Late Albian) and Bahariya formations (Early Cenomanian) from AG well, located in northern part of Western Desert. (long. 28o 30' 15 E and lat. 29˚ 46' 04 N) Fig. 1 The palynofacies recovered from Albian – Cenomanian clastic sediments of Kharita and Bahariya formations are studied to identify associated paleoenvironment. Abu Gharadig Basin is an elongated graben, trending E – W bounded to north and south, respectively by Qattara ridge and Sitra platform [1] and [2] Stated that the source of gases present in Bahariya formation is believed to have been derived from deep deposits of basin As Cretaceous system is considerd as main targets in exploration for petroleum in Egypt, [3-8]. Fig. 1. Location map of studied borehole AG.4

Mapping basement relief of Abu Gharadig Basin, Western Desert of Egypt using 3D inversion of pseudo-gravity data

There are a number of magnetic inversion methods that have been developed to map the structure and depth of sedimentary basins, assuming that sediments are nonmagnetic and underlain by magnetic basement. Gridding/mapping the basement depth estimates from such methods has two significant problems: 1) the magnetic results are dominated by signals coming from the top edges of basement faults such that the depth information from the down thrown sides of the faults is not captured and 2) within the centres of large basins there is often little variation in the magnetic anomaly to provide depth estimates such that when gridding the depth data, grid interpolation has to rely on a sparse distribution of estimated depths. In this study we convert the magnetic data into pseudogravity which is then inverted to produce a 3D basin model with a constant susceptibility basement. This overcomes the interpolation problem since the 3D model now uses the complete pseudo-gravity field as well as the magnetic depth estimates to constrain the depth model. The method is applied to the Abu Gharadig basin, Western Desert, Egypt and generates results which match well controls on basement depth. The advantages of this method over 3D gravity inversion are that the pseudogravity response is not affected by structure within the sediments and is not compensated isostati

Basin Delineation with a 40-Hour Passive Seismic Record

Several geophysical methods exist to delineate the lower interface of a sedimentary basin. Most popularly employed are gravity and magnetic surveys and surface-wave inversion. While all three methods are successful overall in estimating an average basin depth, they fail to find a more detailed depth variation. As an alter- native, we consider three passive seismic techniques, using especially body waves. We analyze 40 hours of data, recorded with 110 stations installed over the Abu Gharadig basin in Egypt. In an earlier study we found the frequency band of 0.09-1.0 Hz to be dominated by body waves. As a first method we apply body-wave seismic interfero- metry (SI). Using body-wave noise, we extract PP and SS reflections from the basin floor. We estimate the depth of the basin to be around 4.8 km. As a second technique we estimate the resonance spectra of the basin, using the horizontal-to-vertical (H/V) spectral ratio. Using surface-wave noise, we find an extremum that is probably related to the complete sedimentary package. Using this peak, we find a basin depth of 5.4 km. Using S-phase arrivals, we find two extrema in the H/V, which are probably related to the S-wave resonances of two distinct layers in the basin. As a third method we compute receiver functions (RFs). Based on the RFs, we can confirm the presence of a large interface in the upper crust, but we cannot well constrain its depth.

Application of biological markers in the recognition of the geochemical characteristics of some crude oils from Abu Gharadig Basin, north Western Desert – Egypt

The objective of this study is to establish the relationship between the hydrocarbons recovered from the Abu Gharadig Basin and Middle Jurassic Khatatba Formation, as well as the previously established Upper Cretaceous Abu Roash-F Member. A suite of fourteen crude oil and condensate samples from the Mesozoic reservoirs (Jurassic-Cretaceous) of the Abu Gharadig Basin (Western Desert, Egypt) was analyzed and geochemically compared with extracts from source rocks of the Middle Jurassic (Khatatba Formation) and the Upper Cretaceous (Abu Roash-F Member). Based on molecular indicators of organic source input, depositional environment and age-diagnostic biomarkers, at least two petroleum systems operate in the Abu Gharadig Basin; those derived from Late Cretaceous marine shales and Jurassic-Early Cretaceous non-marine organic-rich shales as source rocks and possibly a third system appears to be a mixture of them both. The correlation of some Abu Gharadig oils to a Late Cretaceous source establishes a petroleum system involving these marine Cretaceous source rocks.

Two-and-a-Half Dimension Gravity Modeling to Delineate the Structures of the Western Abu Gharadig Basin, Western Desert, Egypt

abstract The present study is a trial to carry out 2½-dimensional gravity modeling to confirm the structures and tectonics of the western Abu Gharadig Basin, Western Desert, Egypt. This is achieved by a sequence of procedures, started by establishing the trends of six 2½-dimensional residual gravity models, most of them passing through the available control wells. Two-and-a-half-dimensional gravity modeling of mass distributions in the subsurface of the study area was performed on the significant residual anomalies of the area, which had been separated from the unwanted regional field. They were separated using the average power spectrum method available in the suite of programs provided by Geosoft (1994). Such 2½-dimensional models were constructed to reveal the dissecting structures and to subdivide the sedimentary sequence of the area into 10 time-rock and rock units (Paleozoic and Jurassic sequences, Alamein-Shaltut, Kharita, Bahariya, Abu Roash, Khoman, Apollonia, and Dabaa), in addition to the underlying basement complex. Some seismic sections were used to help constrain the construction of 2½-dimensional models. Two-and-a-half-dimensional gravity models were constructed after transferring the structural and geologic information (fault elements and depth values) of the two-dimensional gravity models to the base maps. In this way, 10 structural contour maps were established on the tops of the respective stratigraphic units. Generally, these maps reflect the considerable effect of the NE-SW and NW-SE trends as major directions of fracturing in the study area of the northern Western Desert of Egypt.

Extraction of P-wave reflections from microseisms

The last few years there has been a growing number of body-wave observations in noise records. In 1973, Vinnik conjectured that P-waves would even be the dominant wavemode, at epicentral distances of about 40 degrees and onwards from an oceanic source. At arrays far from offshore storms, surface waves induced by nearby storms would not mask the body-wave signal and hence primarily P-waves would be recorded. We measured at such an array in Egypt and indeed found a large proportion of P-waves. At the same time, a new methodology is under development to characterize the lithosphere below an array of receivers, without active sources or local earthquakes. Instead, transmitted waves are used which are caused by distant sources. These sources may either be transient or more stationary. With this new methodology, called seismic interferometry, reflection responses are extracted from the coda of transmissions. Combining the two developments, it is clear that there is a large potential for obtaining reflection responses from low-frequency noise. A potential practical advantage of using noise instead of earthquake responses would be that an array only needs to be deployed for a few days or weeks instead of months, to gather enough illumination. We used a few days of continuous noise, recorded with an array in the Abu Gharadig basin, Egypt. We split up the record in three distinct frequency bands and in many small time windows. Using array techniques and taking advantage of all three-component recordings, we could unravel the dominant wavemodes arriving in each time window and in each frequency band. The recorded wavemodes, and hence the noise sources, varied significantly per frequency band, and – to a lesser extent – per time window. Primarily P-waves were detected on the vertical component for two of the three frequency bands. For these frequency bands, we only selected the time windows with a favorable illumination. By subsequently, applying seismic interferometry, we retrieved P-wave reflection responses and delineated reflectors in the crust, the Moho and possibly the Lehmann discontinuity.

Interpretation of aeromagnetic and gravity data in East Qattara Depression, North Western Desert, Egypt

The study area lies to the east of Qattara Depression at the north of the Western Desert, Egypt. It is bounded by latitudes 29°00′ and 30°00′ N and longitudes 28°00′ and 29°30′ E, including Abu Gharadig basin, which is the most petroliferous basin in the Egyptian Western Desert. Numerous exploratory wells show that the area is characterized by a thick sedimentary section, unconformably overlying the basement rocks. The main objective of the present study is to outline the structural parameters controlling the area under consideration. Aeromagnetic and gravity data were subjected to the analytic signal, 3D Euler deconvolution and edge enhancement techniques. The Analytic signal and 3D Euler deconvolution were utilized mainly to locate the main subsurface contact zones and to determine the depth and structural indices of the expected causative subsurface structural elements. However, the edge enhancement technique was used with various windows to enhance the edges of subsurface structures. The structural indices were estimated to be ranging between 0.16 and 0.26, indicating that the area is mainly controlled by faults. The depth of these structural elements was also estimated to be ranging between <1.37 and 5.29 km. It has been shown that the structural elements of the study area have different directions, trending E-W, ENE, NW, and N-S.

Petrophysical analysis of the Kharita and Bahariya reservoirs, Badr El Din-1 Field, Western Desert, Egypt

The Albian-Cenomanian Kharita and Bahariya formations are two of the most important oil-producing reservoirs in the Western Desert of Egypt. The area of study includes the Badr El Din-1 (BED-1) Field in the center of Abu Gharadig Basin about 300 km west of Cairo and 12.5 km north of Abu Gharadig Field (Figure 1). The BED1–1 oil discovery well, drilled in December 1981, was based on seismic and geological interpretations.

Electric fabric of Cretaceous clastic rocks in Abu Gharadig basin, Western Desert, Egypt

Measuring the petrophysical properties of sedimentary rocks in three-dimensions (3-D) has a high priority for interpretation of their physical behaviour. The present work attempts to study the 3-D electric behaviour of the Upper Cretaceous sandstones and clayey sandstones in the Abu Gharadig basin, Egypt. These rocks belong to the Betty, Bahariya, and Abu Roash Formations. The apparent electrical resistivity ( R o ) was measured in three perpendicular directions, one normal to the bedding plane along Z-axis, and the other two directions parallel to the bedding plane and normal to each other, along X-axis and Y-axis. The electrical resistivity ( R o ) was also studied at three NaCl-saline concentrations of R w = 0.53, 0.13, and 0.07 Ω m in ambient conditions, using A–C bridge at 1 kHz. It is proposed that, processing and matching the electric data in 3-D as ellipsoids instead of in 2-D, has led to the electric fabric concept. It is a combination of electric foliation ( F) and electric lineation ( L). Statistical analyses of measured electrical resistivity reveal that the electric fabric at the second brine concentration should be taken into consideration to avoid the effect of clay content. The electric lineation and foliation of the studied sandstones and clayey sandstones at the second concentration are mostly small (1.1–1.5) to moderate (1.5–2.5), with few sandstone samples having high (2.5–5.0) to very high foliation (5.0–7.5), whereas the electric anisotropy values for these samples are small to moderate (1.1–2.5). This fabric is contributed mainly from their electric foliation, indicating some load pressure compaction that led to small to moderate anisotropic grains and flow paths/network pore spaces.

Organic geochemical studies of some early cretaceous sediments, Abu Gharadig Basin, Western Desert, Egypt

A total of 81 shale samples from the Early Cretaceous sediments of seven wells in the Abu Gharadig Basin, were analysed for organic matter quantity, type and maturation. The total organic carbon content of analysed samples ranges between 0.5 and 2.67 wt%, indicating a fair to good organic content. The location of investigated samples on the van Krevelen diagram reflects the presence of kerogens type IV (without hydrocarbon potential), type III (gas-prone) and type II–III (oil and gas-prone). The estimated temperature of maximum pyrolytic hydrocarbon generation of analysed shales ranges between 426 and 447°C, indicating immature to thermally mature organic matter. The shale beds of Kharita Member from the northcentral part of the study area, at depths more than 2164 m, represent gas-prone source beds, while those of Alam El-Bueib Member, at depths more than 2545 m, can be considered potentially as active oil and gas-prone source beds. The present study reveals that the Early Cretaceous Alam El-Bueib Member is more enriched in thermally mature type III and II–III organic-rich shale beds, and consequently can be regarded as the potential source for the oil and gas accumulations in the carbonate reservoirs of the Alamein Member and sandstone reservoirs of the Kharita Member in the Abu El-Gharadig Basin.

Modes of structural evolution of Abu Gharadig Basin, Western desert of Egypt as deduced from seismic data

The present study, which is mainly devoted to the critical analysis of all available drill hole data and seismic reflection records in the Abu Gharadig Basin area which lies principally to the east of the Qattara Depression in the central portion of the Northern Western Desert of Egypt, indicates that the Abu Gharadig Basin is an elliptical, multicyclic, E-W trending structurally-controlled basin developed originally as a result of the deep crustal extensional tectonics that affected Northern Egypt during the Mesozoic Era. The basin seems to have been initiated by a localized mantle bulge that led to the restricted deep crustal extension in the area under study during the early phases of the Alpine movements which took place in Late Jurassic. The basin was brought to its active maturation phase during the Cretaceous as a result of the large-scale extensional tectonics along two major bounding E-W trending listric growth faults. Tilting of the basin, took place during the Uppermost Cretaceous/Early Tertiary as a result of the compressive stresses (NW-SE) that were associated with the Laramide phase during these times.

Acoustic characteristics of the Abu Gharadig Basin sediments, Western Desert, Egypt

The present investigation is mainly devoted to the critical analysis of the available exploratory data obtained from more than 35 deep holes, with the aim of delineating the geo-seismic characteristic features of the different rock units existing within the conspicuous Abu Gharadig Cretaceous Basin. Such a study reveals that the base Tertiary, which is separating the strongly deformed Cretaceous reflectors from the undeformed Tertiary ones, has a medium positive reflectivity, whereas the top Alamein ‘dolomites’ (top Aptian) and the top Massajid (top Middle Jurassic) reflectors have strong positive reflectivity of the first order. Moreover, the top Apollonia (top Middle Eocene) and the top Abu Roash (top Coniacian) are found to show up with a medium of strong positive reflectivity of second order. Also, the top Dabaa (top Oligocene), top Bahariya (top Lower Cenomanian) and top Kharita (top Albian) reflectors are considered as weak variable reflectors of the third order. Implications as to the structural setting of the basin are introduced here in view of such acoustic characteristics when applied to some seismic lines in the area studied.

A geophysical study on the Abu Gharadig basin, Egypt

The area of study comprises one of the most hydrocarbon‐potential basins of the Egyptian Western Desert, the Abu Gharadig basin. Major marine transgression and regression cycles dominated the territory during different geologic times. Those depositional cycles, together with at least three tectonic cycles—the end of the Paleozoic Hercynean, the close of the Jurassic until the Late Cretaceous and, the close of the Cretaceous until Mid‐Teritary—resulted in a highly deformed, thick sedimentary cover. A study of the geophysical anomalies of the basin, including those indicated by aeromagnetic, gravity, and seismic data as well as the study of about 60 deep wells drilled within and around the Abu Gharadig basin, has revealed that the major tectonic disturbances of the area were caused by basement complex block faulting. These major tectonic disturbances have produced great variations in the thickness and distribution of the various geologic units throughout the region. Aeromagnetic anomalies and the wells which reached the basement indicate great variations in the depths and type of the basement complex and the presence of major intrusions in the region. The major fracturing is indicated to be mainly along an east‐west, west‐northwest and east‐northeast directions. The Bouguer gravity anomalies indicate major basement fracturing as well as variations in sedimentary patterns, erosions, and subsequent tectonic disturbances. The most obvious anomalous trends on the gravity map, based on frequency and amplitude, are the north‐east to east‐northeast, the east‐west and the west‐northwest. The main Abu Gharadig depositional center does not show sharp variations because of the homogeneity of the near‐surface rocks and the great basement depth (20 000-40 000 ft). Seismic interpretation has confirmed the presence of all these fracturing trends. It also identified some major structural trends. These are closely related to the depositional centers, and represent potential drilling locations, especially those associated with Late Cretaceous‐Tertiary active contemporaneous faulting.

Petroleum Potential of Western Desert of Egypt: ABSTRACT

The Western Desert of Egypt, despite many discouragements, has major potential as a petroleum province. Approximately 150 exploratory wells have discovered nine commercial oil and gas fields, with flows of oil or gas recorded from an additional 21 wells. All discoveries have been in marine inner shelf sandstones and carbonates that range from Aptian to Turonian in age. Potential reservoir rocks are known in Paleozoic to Tertiary sedimentary rocks. Mature source rocks have been recognized in the Devonian and in Jurassic to Upper Cretaceous strata. Seals, mainly shale, but including carbonates and some evaporites, are present in most formations in most areas. Structural traps are abundant. Despite these favorable factors, in-place reserves of only 800 million bbl of oil and condensate, and up to 1,185 bcf of natural gas have been found. Almost all exploration has been limited to the drilling of relatively small onshore structures and no giant fields have been found. All significant discoveries to date have been in anticlinal traps, commonly modified by faulting. New investigations utilizing a broad regional tectonic framework provide a means both of recognizing the more prospective provinces of the Western Desert and for understanding the structural evolution in terms of the timing of growth folding and growth faulting. These new investigations have been based on an approximately 10 by 10 km (6 by 6 mi) seismic grid and have identified many structural prospects and leads in the onshore area. Most structures are in the Abu Gharadig, Kattaniya (Gindi basin), and northern province of the Western Desert. The Abu Gharadig basin is of particular interest, being recognized as a major rhombochasmic basin containing numerous localized highs provided by northeast-southwest-oriented, doubly plunging (periclinal) anticlines. There are, therefore, suffi ient structures to warrant extensive additional exploration. Particular attention should be given to testing the lower part of the Cretaceous and Jurassic. The Paleozoic section also warrants further attention as demonstrated by a review of drilling results and by indications from gravity data. The new investigations indicate a considerable potential within the Western Desert for discovery of small to moderate-size accumulations of oil and gas. In addition, possible reefal, carbonate End_Page 1207------------------------------ bank, and partially dolomitized trends (largely in the immediate offshore areas) are recognized. More exploration should test these features, which although high-risk leads, may contain giant fields. End_of_Article - Last_Page 1208------------

Habitat of Oil in Abu Gharadig and Faiyum Basins, Western Desert, Egypt

The Abu Gharadig and Faiyum basins are areas which have some of the greatest hydrocarbon potential in the Western Desert of Egypt. Several extensive cycles of marine transgression and regression occurred in these territories through geologic time. The depositional cycles combined with at least 3 tectonic cycles--(1) the Hercynian orogeny at the end of the Paleozoic, (2) from Late Jurassic to early Tertiary, and (3) from Late Cretaceous to middle Tertiary--resulted in a highly deformed, thick sedimentary sequence. This organic-rich Jurassic-Upper Cretaceous-lower Tertiary sequence in large areas of these basins was subjected to enough heat and depth to generate hydrocarbons. It is evident from recent discoveries that these source rocks generated large amounts of high-quali y oil and gas. The Abu Gharadig and Faiyum basins are separated structurally by a major ridge. Both basins are bounded on the north by another major ridge associated with Cretaceous and Tertiary faulting. A major platform with thin sedimentary cover forms the southern boundary. The hydrocarbon potential exists in cyclic sequences of sandstone, shale, and carbonate, having moderate porosities and permeabilities. An important hydrologic phenomenon prevails in major parts of the basins; fresh water has flushed the early Cenomanian and older reservoirs. The eastern part of the Faiyum basin, the southern platform, the Kattaniya high, and the southern and western rims of the Abu Gharadig basin are completely flushed, leaving little chance for hydrocarbon preservation in these localities. Exploration efforts should be concentrated on deep structures close to the main depocenters and inside or very close to the 150°F (65°C) geothermal contour. Contemporaneous structures on the northern rims of the basins should have high potential, resulting from migration of hydrocarbons from the south across major faults. The Jurassic in the northeastern part of the Abu Gharadig basin may provide good hydrocarbon potential. The lower Tertiary sequence present in the troughs also may have large amounts of oil entrapped in situ or resulting in short-distance migration to the northern structures or to the Late Cretaceous-early Tertiary Syrian arc traps.

Paleozoic and Mesozoic Stratigraphy and Oil Potential of Western Desert: ABSTRACT

The depocenter of the Paleozoic basin in western Egypt lies in the northwestern part of the Western Desert. The sediments are primarily terrigenous (with two minor phases of vulcanicity) laid down in an epicontinental sea. The depositional axis of the basin, where thicknesses in excess of 2,800 m (9,200 ft) have been recorded, has a northwesterly trend to the vicinity of the Siwa Oasis. A less well-defined shallower basin with a northerly trend lies to the southwest. The facies show such similarities to those found in the Ghadames and Murzuq basins that the same formational names are applied. Farther east, a possible Paleozoic basin lies in the Abu Gharadig area where 1,300 m (4,265 ft) of sediments were drilled. The limits of this presumed basin are questionable since ba ement was not reached. Following the deposition of the Paleozoic section, there was a marked hiatus; the time of Hercynian movements for Permian and Triassic beds is absent. Uplift and the presence of volcanics dated in Permian-Carboniferous time are indicative of Hercynian tectonic activity. Only in Early Jurassic time did the seas again begin to encroach upon the Western Desert area from the Salum basin in the northwest and the Wadi Natrun basin to the east and northeast. This process continued, until by the time of the Oxfordian transgression maximum there was a relatively uniform carbonate cover to about lat. 29°N over the Western Desert. Further tectonic uplift accompanied by faulting and marine regression is dated from late Kimmeridgian time to the beginning of the Cretaceous, when transgression began once again. The pattern of transgression, however, differs from that of the Jurassic; the two basins, the more westerly Matru basin and the easterly Alamein basin, both have north-northeasterly trends, although by Aptian times they are less clearly distinguishable. The dominant feature, new in the Western Desert, was the development of an east-west extensional basin, the Abu Gharadig basin, in Cretaceous time. It was bounded on the north (30°N) by the Rabat Abu Rivash ridge, which persisted through the Cretaceous. The trough became less distinctive in Cenozoic times when a further trough, the Tiba basin, developed north of the ridge. Production from the northern Western Desert until recently has been disappointing. Exploration results from the Paleozoic Section have yielded little, but the existence of a marine section suggests that the area northeast of Siwa still has potential. The thick deeply buried Jurassic marine sequence in the Western Desert may be the source for at least part of the production from Cretaceous horizons in the Abu Ghradig, Alamein, and Razzak oil and gas fields. End_of_Article - Last_Page 495------------

Oil and Gas Prospects in Egypt

Accumulations of oil were first known in Egypt since 1968, some ten years after the famous Drake well in Pennsylvania in August 1859. These oil accumulation were found as seepages in tunnels dug for extracting sulphur in the area of Gemsa on the West coast of the Gulf of Suez. Since that time exploration activites were conducted on and off throughout a long history of operations which witnessed the use of the latest developments in exploration tools and techniques. So far, the main oil province in Egypt is the Gulf of Suez Basin, where the bulk of oil reserve have been found. Other hydrocarbon provinces are the Nile Delta Basin, the Abu Gharadig Basin and the Alamein ridge, both in the Western Desert. Three important gas discoveries were made in the Nile Delta Basin two of which are offshore, in addition to other so for non commercial gas finds. In addition to the known oil and gas discoveries the exploration activities throughout that long period contributed volumenous geological and geophysical material and data which added appreciably to the geology of Egypt at large, and in particular to the petroleum geology of the country. The Gulf of Suez oil province displayed very favourable conditions for the generation and trapping of hydrocarbons in Miocene and Pre-Miocene pools though at the same time it displayed very complicated geological setting which renders the exploration work a difficult task. The Nile Delta Basin, on the otherhand, is a relatively very recently explored area. Accordingly, extensive exploration work is still needed in order to evaluate the hydrocarbon possibilities of that basin. So for, gas has been discovered at a number of locations in lower Pliocene-Miocene pools. Whether future work would prove that oil generation took place remains to be seen. The Western Desert did not yet display the required response with regards to the exploration work conducted till now. To date, only few small discoveries have been made with oil and gas pools mainly vvithin the Upper and Lower Cretaceous. Recent advances in seismic techniques are helping in locating deeper structures, which might prove instrumental in the upgrading of the oil possibilites of the region. At present, the exploration activities are going on in the different oil and gas provinces in Egypt. These activilles are expected to increase and are also expected to expand to new areas in the eastern part of the Gulf of Suez Basin, offshore and onland, in Northern Sinai and in the Offshore Mediterranean. These new areas are believed to house very good prospects which will be tested not before long. It is also hoped that progress in seismic tools and techniques will add to the possibilities of finding more oil and gas.