Abu Roash Formation Research Articles

Petrophysical reservoir-rock properties and source-rock characterization of Abu Roash Formation in Wadi El-Rayan oil field, Western Desert, Egypt

Wadi El-Rayan oil field is located in one of the most prolific basins in the northern part of the Western Desert of Egypt. This field produces oil mainly from Abu-Roash Formation which is differentiated into various members of which Abu Roash G and F Members are the most important. This study aims to investigate the different reservoir properties of the Abu Roash G Member (ARG) and evaluate the potential contribution of Abu Roash F Member (ARF) as a source. The well logging data of 10 wells are utilized mainly for enhancing the petrophysical and the source rock analyses. The standard logging analyses usually used for characterizing the hydrocarbon reservoirs are applied. A mixed clastic and carbonate approach is applied for detecting the lithology. Fluid saturations (water and hydrocarbon) are estimated using clean and shaley modules. Estimation of total organic carbon (TOC) is based on ΔlogR method as matched with geochemical and Rock Eval pyrolysis measurements. The deduced petrophysical parameters are represented vertically as reservoir analogs and distributed laterally in a number of property variation maps. The study revealed that Abu Roash G Member is divided into zones, of which the reservoir pay zone (RP zone) attains the best reservoir properties. Ranges of 16.5–52.5 and 3.0–19.5 m and 8–26, 19–26, and 45–73% are given for gross and net pay thicknesses, shale volume, effective porosity, and hydrocarbon saturation, respectively. The lateral distribution maps of the reservoir and source rock parameters showed that net reservoir thickness, hydrocarbon saturation, and TOC content increase toward the central of the study area. The ΔlogR overlays revealed that ARF Member is a good source rock which is classified into two overlying zones. The upper zone (ARF-SR1) has fair to good source characteristics, while the lower zone (AFR-SR2) is the main source rock with TOC content range of 2.13 to 4.12%. The Rock Eval and geochemical measurements strongly indicate oil-prone facies with hydrogen indices of 509–705 and S2 yields of 9.42–23.26 mg HC/g. In conclusion, the ARG Member showed good hydrocarbon potentiality and reservoir properties. The organic enrichment of the overlying ARF-SR2 zone offered the main source potentiality. Based on the petrophysical data logs and distribution maps, it is recommended to consider central part of the field for any further hydrocarbon exploration/production activity.

Source rock potential and depositional environment of Upper Cretaceous sedimentary rocks, Abu Gharadig Basin, Western Desert, Egypt: An integrated palynological, organic and inorganic geochemical study

The Abu Gharadig Basin in the northern part of the Western Desert, Egypt is among the most important petroleum provinces in Egypt. Here, Cenomanian to Santonian rocks of Bahariya Formation and Abu Roash A-G members from the GPT-3 well were investigated for their depositional environment, kerogen quality, petroleum generation potential and thermal maturity by geochemical, petrological and palynological methods. The sediments of the Bahariya and Abu Roash formations excluding the Abu Roash “F” Member represent variable shallow marine environments with poor preservation of marine organic matter, whereas there is an excellent preservation in the Abu Roash “F” Member. The basal part of this member is characterized by anoxic, carbonate-rich depositional conditions, high TOC values up to 7%, high HI up to 700 mgHC/gTOC and liptinite-dominated organic matter. Depletion of iron leads to sulfur incorporation into organic matter which is reflected in high thiophene/benzene ratios. Above, sediments are enriched in “terrestrial elements” Fe, Ti, as well as K and Mn. This pattern and the occurrence of the fresh/brackish water algae Botryococcus suggests a regression phase during deposition. The upper part of the Abu Roash “F” Member is again characterized by fully marine, suboxic conditions and a lower thiophene/benzene ratio. The source rock section demonstrates lower thermal maturity compared to the above and below sections based on all microscopic, pyrolysis and biomarker data. This indicates thermal maturity retardation/suppression most likely due to a different organic facies and early diagenetic transformation of kerogen as indicated by the geochemical and palynological data. The source rock heterogeneity indicates a relatively shallow marine environment where the changes in bottom water conditions are very sensitive to sea level fluctuations. Residual oil characterization reveals two reservoir compartments, which are in the Abu Roash “D” and “C” members.The Abu Roash “F” source rocks are compared with time-equivalent sediments in the Tarfaya Basin in Morocco, which represent more distal settings. The more proximal group (A) is characterized by S/Fe ratios between 0.57 and 0.67 indicating suboxic conditions. It has TOC and HI values not exceeding 4% and 600 mgHC/gTOC, respectively, at variable CaCO3 contents. The more distal Tarfaya sediments (group B) have higher TOC and HI as well as high organic sulfur contents. Group A is higher in terrigenous element concentrations. The Tmax of immature source rocks ranges from 410 to 415°C in organic‑sulfur rich samples and from 420 to 430°C in organic‑sulfur poor samples revealing an important impact of organic facies on maturity parameters. Furthermore, there is an inverse relationship between S/Fe and Al2O3/TOC which might become an important tool in paleoenvironmental reconstructions as well as petroleum source rock studies.

Palynological, palaeoenvironmental and sequence stratigraphical analyses of a Turonian-Coniacian sequence, Beni Suef Basin, Eastern Desert, Egypt: Implication of Pediastrum rhythmic signature

Sixteen samples from the “E” to “B” members of the Abu Roash Formation encountered in the Beni Suef Basin, Eastern Desert of Egypt were palynologically analyzed for palaeoenvironmental and sequence stratigraphic investigations. The integrated palynofacies and lithofacies analysis of the studied section indicates deposition of five alternating regressive and transgressive sequences in well-oxygenated, proximal shelf settings. The Abu Roash “E” and the upper “D” to the lower “C” members were deposited during pronounced regressive phases in oxic, shallow marginal marine settings. The upper “B” Member was deposited during a recurring regressive phase but of a lower magnitude in oxic, shallow inner neritic conditions. The lower “D” Member was deposited during a minor transgression phase in dysoxic, shallow inner neritic settings. While the upper “C” to the lower “B” section was deposited during a stronger transgressive episode in a relatively deep, inner neritic environment of prominent dysoxic conditions. This interchange in the depositional setting was documented by the pronounced and concurrent, cyclic nature of the freshwater algae, peridinioid dinoflagellate cysts, pteridophyte spores, and reworked sporomorphs with variable intensities. Their increasing and conversely their diminishing trends clearly reflect alternating regressive-transgressive periods of reduced and relatively normal salinity conditions, respectively. Overall, sedimentation of the studied Abu Roash section indicates a recurring rise in sea level, which accentuated during the earliest Santonian time.The analogous peaking in the Pediastrum signals with those of the pteridophyte spores and reworked taxa indicate a good connection between these Pediastrum signals and the pronounced fluviatile influxes of terrigenous sediments during regressive phases. Accordingly, this can be used to identify regressive sequence boundaries and hence the clastic reservoirs. Even with the small counts recorded herein, we believe high ratios of peridinioid/gonyalulacoid dinocysts are significantly paralleled by peaking signals of freshwater algae and regressive sedimentation phases. This must be preliminary documented here. Probably future palynological studies will be able to fully interpret and address this important Pediastrum rhythmic event in different sequence stratigraphic settings.The palynological parameters, age controlled sporomorph marker taxa, lithology, and gamma ray data were used to differentiate the Abu Roash members into three distinctive 3rd order depositional sequences (AR SQ1, AR SQ2, and AR SQ3). These sequences match well with the global stratigraphic sequences Tu 3, Tu 4, and Co 1 and connect the local rise in sea level to the global eustatic sea level rise.

Wrench tectonics of Abu Gharadig Basin, Western Desert, Egypt: a structural analysis for hydrocarbon prospects

Mapping based on the interpreted seismic data covering the Abu Gharadig Basin in the northern Western Desert has revealed that the deposition of the Upper Cretaceous succession was controlled by dextral wrench tectonics. This dextral shear accompanied NW movement of the African Plate relative to Laurasian Plate. Structural depth maps of the Cenomanian Bahariya Formation and the Turonian-Coniacian D and A members of Abu Roash Formation display a clear NE-SW anticline dissected by NW-SE normal faults. This anticline represents one of the en echelon folds characterizing the wrench compressional component. The interpreted normal faults reflect the extensional T-fractures associated with the wrenching tectonics. The interaction between the aforementioned NE-SW anticline with the NW-SE extensional faults further confirms the effect of the Upper Cretaceous dextral wrench tectonic. However, the influence of this wrench tectonics was gradually diminishing from the Cenomanian up to the Coniacian times. The NW-SE compressional stress of the dextral wrench compressional component during the Cenomanian up to Coniacian age was greater in NW direction than the SE direction. Three mapped structural closures which are predicted to be potential hydrocarbon traps belonging to the Bahariya Formation and Abu Roash D Member, and are recommended to be drilled in the study area, with potential reservoirs. The regularity of the en echelon array of both anticlines and normal faults within the wrench zones suggests additional closures may be located elsewhere beside the study area.

Palynofacies analysis and palaeoenvironmental reconstruction of the Upper Cretaceous sequence drilled by the Salam-60 well, Shushan Basin: Implications on the regional depositional environments and hydrocarbon exploration potential of north-western Egypt

A palynofacies analysis was carried out on thirty ditch-cuttings from the Upper Cretaceous sequences drilled by the Salam-60 well in the Shushan Basin, north-western Egypt. Quantitative vertical distributions of palynomorphs and particulate organic matter exhibit two palynofacies (PF) types. PF-1 suggests deposition of the clastic-carbonate section of upper Bahariya and the lowermost “G” Member of Abu Roash in a brackish, proximal inner shelf environment of prevailing reducing (suboxic-anoxic) conditions that witnessed occasional local oxic-dysoxic conditions. A slight shift from a proximal to a distal inner shelf environment that witnessed notable fluctuations resulted in deposition of the mainly carbonate section of the uppermost “G” and “F” to “C” members, during a late Cenomanian-Turonian marine transgression, under the same suboxic-anoxic conditions. This relative sea level rise was mostly connected to the global late Cenomanian marine transgression. PF-2 represents the rest of the carbonate section (“B” and “A” members) of Abu Roash and Khoman formations, which was deposited in middle shelf environments of prominent suboxic-anoxic conditions during a major regional marine transgression that was mostly connected to the global Turonian-Maastrichtian eustatic sea level rise. Nevertheless, minor fluctuations in the local Turonian sea level may have occurred. Regional comparison indicates Bahariya and the “G” Member of Abu Roash formations have similar marginal to inner shelf depositional settings across most of the northern Western Desert. Except at western Matruh Basin, where they have a deeper open marine, middle shelf setting. The “F” to “C” members have an outer inner shelf setting in the coastal basins (Shushan and Matruh basins) and a deeper, inner middle shelf setting at the central basinal area (Abu Gharadig Basin). This interbasinal difference in their depositional settings is mostly related to the late Cretaceous tectonic differentiation of Abu Gharadig Basin. The “B” and “A” members of Abu Roash and Khoman formations were deposited in central Abu Gharadig and at southern Matruh basins in deeper, outer shelf and upper to middle slope settings in comparison to their suggested inner middle and outer middle shelf settings in Shushan Basin. This was due to the progressive late Cretaceous tectonic development of Abu Gharadig and Matruh basins. Local pteridophytes on wet lowlands and conifers on elevated hinterlands were growing near Salam-60 under a regional warm and relatively dry palaeoclimate.

Geochemistry, generation and maturation of the hydrocarbons at Wadi Al-Rayan oil field, Western Desert of Egypt

ABSTRACT`The present work aims to study the organic chemistry, the generation and maturation of the hydrocarbons encountered at Abu Roash Formation, Wadi El Rayan oil field. The analysis of source rocks indicates the presence of two organic facies. The first is characterized by high total organic carbon of 0.93–3.39%, strongly oil-prone (Type II), and good potential for oil generation (pyrolysis S2 yields 4.54–23.26 mg HC/g rock and HI 488–705 mg HC/g TOC). The second attains good range of organic carbon from 0.90% to 1.57%, which is a mixed oil and gas (Type II–Type III) of fair hydrocarbon generation (pyrolysis S2 yield of 1.98–5.33 mg HC/g). The kerogen type consists of unstructured lipids and some terrestrial material. Plot of Pr/n-C17 versus Ph/n-C18 indicates that the crude oil was derived from mixed source rock, while the maturity profile assigns oil windows (0.6 Ro%) matching topmost of Abu Roash G Member.

Pre-drill pore pressure prediction using seismic velocities for prospect areas at Beni Suef Oil Field, Western Desert, Egypt

Pre-drill prediction of formation pore pressure from surface seismic survey is very important for drilling, production, and reservoir engineering because it affects drilling operations and well-planning processes. If it is not properly evaluated, it can lead to numerous drilling problems such as dangerous well kicks, lost circulation, blowouts, stuck pipe, excessive costs, and borehole instability. Pre-drill pore pressure estimation has been obtained from transform models using seismic interval velocities. However, the accuracy of this estimate of pore pressure is directly related to the reliability of these interval velocities. Bulk density was estimated from seismic interval velocity and transit time. Normal pore pressure gradient is estimated from the slope of a trendline that is generated from logarithm transit times versus depth. Overburden pressure at any depth was calculated from the integration of the average interval bulk densities and thicknesses above that depth. Pore pressure has been obtained from overburden pressure and observed interval velocities using modified Eaton’s equation. 154 CDPs were used along 28 seismic lines at Beni Suef basin, Western Desert, Egypt, to accomplish the purpose of this study. Two velocity reversal zones showing abnormally high pore pressure were detected and correlated to Abu Roash and Bahariya Formations. Moreover, pore pressure gradient maps were established for these two zones to predict the possible horizontal fluid flow (migration paths) for the proposal of prospects with lower pressures and less drilling risks. Finally, it is possible to calculate and recommend the required heavier mud weight to drill.

Integrative 1D-2D Basin Modeling of the Cretaceous Beni Suef basin, Western Desert, Egypt

An integrated seismic, borehole petrophysical and geochemical data constrained 1D and 2D basin model study is conducted for the Beni Suef basin (Western Desert, Egypt) to enhance the understanding of the Cretaceous plays while demonstrating how basin modeling can be used to reduce exploration risk and improve exploration success. The Cretaceous petroleum systems consist of two major source rocks (the Upper Cretaceous limestone of Abu Roash “F’’ member, and Lower Cretaceous shales of Kharita and Alam El-Bueib formations), five reservoirs (Cretaceous sandstones of Abu Roash “A, E & G’’, Baharyia and Kharita formations), three seals (Lower Cretaceous and Upper Cretaceous shales of Kharita and Bahariya formations and fine grained limestones of the Abu Roash Formation), and vertical source mixing migration pathways owing to vertical faults resulting from four episodes of elastic crustal extension and above trap lateral migration. The entrapment style of the generated hydrocarbons and its roles on the charge and migration process in the Cretaceous reservoir rocks were determined from the seismic interpretation. Three episodes of uplift erosion (Early Cretaceous, Late Cretaceous-Paleocene, and Paleogene-Neogene) have occurred in the basin and have increased exploration risk in some areas by breaching the integrity of the seal. Migration from the source rock into the trap is mainly vertical migration. However, in areas where the hydrocarbons have escaped through the faults at the boundaries of the basin, migration in the layers above the trap is mainly lateral. The hydrocarbons generated are predominantly oil. The Lower Cretaceous shales of the Kharita and Alam El-Bueib formations exhibit good thickness, total organic content (TOC), kerogen type (mixed type II and III), and maturation.

Paleoecologic and stratigraphic significance of the freshwater algae Pediastrum in the Upper Cretaceous (Turonian) marine deposits, north Western Desert, Egypt

Palynological investigations of samples collected from the Abu Roash Formation, Faghur Hj5-1 well, north Western Desert, Egypt show a low diversity in palynomorph assemblage. This assemblage is mainly dominated by a clear proliferation of Pediastrum (and other allied algal forms, e.g., Scenedesmus and Botryococcus) which today lives exclusively in freshwater. Such a prominent record within the current marine deposits could be considered a good biostratigraphic datum in the Upper Cretaceous (Turonian) period rather than an ecologic event in the north Western Desert, Egypt. The influence of freshwater input on the studied deposits is proven by the presence of heavy minerals including kyanite, zircon, staurolite, and amphiboles encountered in siliciclastic sediments. Most of these minerals are sub-rounded to rounded so they were derived probably from sedimentary rocks. In the studied succession, the presence of Pediastrum reflects sea level fall (i.e., lowstand systems tracts). The occurrence of Pediastrum and other algae in such marine deposits reflects the predominant deposition of fluviatile sediments related to the discharge of rivers into shelf seas.

Seismic – Wireline logs sequence stratigraphic analyses and geologic evolution for the Upper Cretaceous succession of Abu Gharadig basin, Egypt

The Upper Cretaceous megasequence in the northern part of the Egyptian Western Desert has been classified into four 2nd order depositional sequences. These sequences started with the Cenomanian SQ-I topped by the Turonian – Santonian SQ-II. However, both SQ-III and SQ-IV represent the Campanian- Maastrichtian time span. The interpreted 2nd order SQ-I and SQ-II have been further subdivided into six smaller 3rd order sequences (SQ-1 to SQ-6). The depositional history started during the Early Cenomanian times, characterized by wide marine invasion enabled the deposition of the shallow marine Bahariya Formation (SQ-1). The Upper Cenomanian times, witnessed a rapid subsidence, simultaneously with new marine transgressive phase. This is resulted in the deposition of SQ-2, consuming the entire sediments of the Abu Roash G Member. During the Turonian – Coniacian times the northern parts of Egypt showed successive oscillating transgressive – regressive marine cycles led to equivocal sedimentary bodies of the Turonian-Coniacian Abu Roash Formation (SQ-3, SQ-4, and SQ-5). During the Santonian age, the northern parts of Egypt were subjected to tectonic crustal shortening, producing large scale folds. As a result, a new tectonically-overprinted marine depositional cycle started and marked by rapid phase of basin subsidence. This was accompanied by a deep marine invasion covered most of the northern parts of Egyptian lands, depositing the lower parts of the Khoman- B (SQ-6) under transgressive depositional conditions. By the end of Santonian cycle, the upper parts of the Khoman Formation B Member was deposited during a gradual, and slow relative sea level drop ending the deposition of SQ-6. At the beginning of the Campanian – Maastrichtian times, a new widespread sea-level rise associated with basin subsidence. Accordingly, two successive depositional cycles were thus initiated, forming SQ-III and SQ-VI sequences separated by unconformity type-2 boundary (SB-8).

Timing of petroleum generation and source maturity of selected wells in Abu Gharadig Basin, North Western Desert, Egypt

ABSTRACTThe timing of petroleum generation of source rocks is recognized to investigate the maturation level of the proven potential source formations for oil preservation dead lines, and predict the levels of thermal maturity of the studied sequences in terms of hydrocarbon generation and expulsion. For theses purposes four thermal burial history and maturity profiles were constructed of the Abu Gharaig-1 SW Umbaraka-1, GPZ-1, and GPX-1 wells. The results showed Abu Roash and Bahariya formations are immature to mature source rocks and have poor to fair potential to generate both oil and gas and still are within the early stage of hydrocarbon generation till the present time. Alam El Bueib and Masajid formations bear mature source rocks and have good generating capability for generating both oil and gas and entered the oil window since Cretaceous to Miocene times and lies within oil and gas windows at present time. Khatatba Formation bears a mature source rock and has good generating capability for both oil and gas and entered the oil window during Late Cretaceous to Eocene times.

Volumetric Assessment through 3D Geostatic Model for Abu Roash “G” Reservoir in Amana Field-East Abu Gharadig Basin-Western Desert-Egypt

The main objective of constructing a geostatic model is to determine the 3-D geometry of the reservoir rock and assess its hydrocarbon volumetrics. To achieve this goal, the Amana oil field is taken as a real example. An integrated methodological approach was applied starting with data collection and quality control and then followed by interpretation of the available geological, geophysical and petrophysical data. The field area is located in the most eastern trough of the Abu Gharadig basin in the East Bahariya Concession in the Western Desert of Egypt. The source rock in this area is the Upper Jurassic Khatatba Formation that was deposited in a continental to inner-middle shelf environment. The reservoir rock is Abu Roash “G” sand, one of the seven lithologic members of the Abu Roash Formation. Interpretation of seismic data together with well logs revealed the presence of a horst block, acting as a good structural trap, meanwhile the Abu Roash “F” carbonate and Abu Roash “G” shale are the seal rocks. Well data have shown that the reservoir rock in the Amana field is the Abu Roash “G” Member, which comprises three sand lithologic zones; namely the upper, meddle and lower zones. Of these zones, the middle one is the most attractive and has the best reservoir quality. The shale content in this sand is 8% compared to 13% and 26% in the upper and lower zones. In addition, the net to gross thickness ratio is less than 18%, more than 35%, and about 10% in the upper, middle, and lower zones, respectively. Data analysis also indicates that the upper and lower zones are appreciably water wet. However, the middle sand zone appears to be prospective. The net pay thickness in this zone varies between 10 and 32 ft, porosity 19-22%, water saturation 18-40% and average permeability 40 md. Based on the geostatic model of the Amana field reservoir, it is concluded that this area is a positive prospect in the most eastern part of the Abu Gharadig basin. The volume of oil (STOLIIP) in Amana reservoir is calculated as 10 million barrels, with an initial recoverable oil of 1.4 million barrels.

Using of Pickett’s plot in determining the reservoir characteristics in Abu Roash Formation, El-Razzak Oil Field, North Western Desert, Egypt

The present work was devoted to evaluate the reservoir characteristics of the Abu Roash Formation in the vicinity of El-Razzak Oil Field, North Western Desert, Egypt. The area of study is bounded by latitudes 30° 25′ and 30° 55′ N and longitudes 27° 50′ and 28° 40′ E. Nine distributed wells were utilized for this study.A new technique has been applied through Pickett’s plot, to develop some of reservoir petrophysical parameters. These parameters include capillary pressure, pore throat aperture radii, height above the free water table and bulk volume of water. This technique depends on the use of log–log plots of effective porosity versus resistivity combined with empirical relationships for calculating the capillary pressure expressed as a function of permeability, porosity and water saturation. Also, this technique gave the values of petrophysical exponents (m, n and a) which were used to calculate the accurate value of water saturation in both clean and shaly rocks and then adjust estimation of hydrocarbon saturation. The integration of these petrophysical parameters on a log–log graph of porosity versus resistivity gives the importance for Pickett plot to be used in reservoir interpretation.

Palynostratigraphy and palaeoenvironmental significance of the Cretaceous palynomorphs in the Qattara Rim-1X well, North Western Desert, Egypt

Palynological and palynofacies analyses were carried out on some Cretaceous samples from the Qattara Rim-1X borehole, north Western Desert, Egypt. The recorded palynoflora enabled the recognition of two informal miospore biozones arranged from oldest to youngest as Elaterosporites klaszii-Afropollis jardinus Assemblage Zone (mid Albian) and Elaterocolpites castelainii–Afropollis kahramanensis Assemblage Zone (late Albian–mid Cenomanian). A poorly fossiliferous but however, datable interval (late Cenomanian–Turonian to ?Campanian–Maastrichtian) representing the uppermost part of the studied section was also recorded. The palynofacies and visual thermal maturation analyses indicate a mature terrestrially derived organic matter (kerogen III) dominates the sediments of the Kharita and Bahariya formations and thus these two formations comprise potential mature gas source rocks. The sediments of the Abu Roash Formation are mostly dominated by mature amorphous organic matter (kerogen II) and the formation is regarded as a potential mature oil source rock in the well. The palynomorphs and palynofacies analyses suggest deposition of the clastics of the Kharita and Bahariya formations (middle Albian and upper Albian–middle Cenomanian) in a marginal marine setting under dysoxic–anoxic conditions. By contrast, the mixed clastic-carbonate sediments of the Abu Roash Formation (upper Cenomanian–Turonian) and the carbonates of the Khoman Formation (?Campanian–Maastrichtian) were mainly deposited in an inner shallow marine setting under prevailing suboxic–anoxic conditions as a result of the late Cenomanian and the Campanian marine transgressions. This environmental change from marginal to open (inner shelf) basins reflects the vertical change in the type of the organic matter and its corresponding hydrocarbon-prone types. A regional warm and semi-arid climate but with a local humid condition developed near/at the site of the well is thought to have prevailed.

Geothermal History of Hydrocarbon Generation of Wells in the North Western Desert, Egypt

Forty-two rock samples representing seven formations (Ras Qattara, Khatatba, Masajid, Alam El Bueib, Kharita, Baharyia, and Abu Roash) and six thermal burial history modeling of wells (Tut-1x, Kahraman-1, Yasser-1, Salam-3x, Meleiha-4x, and El-Kharita-1x) were used to characterize potential source rocks for generating capability of oil preservation in terms of hydrocarbon generation and expulsion. The results showed that Ras Qattara Formation started to generate hydrocarbons during Paleocene, Khatatba Formation during Late Cretaceous-Eocene, Masajid Formation during Late Cretaceous-Late Miocene, Alam El Bueib Formation during Late Cretaceous-Oligocene, and Kharita Formation during Miocene times. Bahariya and Abu Roash formations are still immature and do not reach the onset of hydrocarbon generation.

Palynology and palynofacies of the Upper Cretaceous succession of the El-Noor-1X borehole, northwestern Egypt

Palynological and palynofacies analyses were carried out on some middle–upper Cretaceous samples from the El-Noor-1X borehole, northern Western Desert, Egypt. Palynological age has lead to a refinement of the original ages suggested by the drilling company. Upper Albian–Lower Cenomanian, Upper Cenomanian, and Turonian–Coniacian were recognized. The palaeoenvironment was interpreted on the basis of the ecological preferences of the palynomorphs. It was fluctuating between marginal to inner-middle shelf environment. Distribution of araucaroid pollen and xerophytes suggests that arid or semi-arid paleclimate prevailed during the deposition of the studied sediments. A warm tropical palaeoclimate is suggested on the basis of abundance of hygrophilous plants. Based on the recovered palynological organic matter, two palynofacies were recognized: palynofacies A for the Bahariya Formation, which suggests kerogen type III, and palynofacies B for the upper Bahariya and Abu Roash Formations, which suggests kerogen type IX. Data gathered from the theoretically estimated vitrinite reflectances, which are based on spore/pollen coloration, and visual pterographic kerogen analysis are used to define the source rock potentialities of the studied sediments.

The Cenomanian/Turonian oceanic anoxic event in the Razzak Field, north Western Desert, Egypt: Source rock potential and paleoenvironmental association

The Western Desert of Egypt is one of the world’s most prolific Jurassic and Cretaceous hydrocarbon provinces. It is one of many basins that experienced organic-rich sedimentation during the late Cenomanian/early Turonian referred to as oceanic anoxic event 2 (OAE2). The Razzak #7 oil well in the Razzak Field in the northern part of the Western Desert encountered the Upper Cretaceous Abu Roash Formation. This study analyzed 23 samples from the upper “G”, “F”, and lower “E” members of the Abu Roash Formation for palynomorphs, particulate organic matter, total organic carbon (TOC) and δ 13C org in order to identify the OAE2, determine hydrocarbon source rock potential, and interpret the depositional environment. The studied samples are generally poor in palynomorphs, but show a marked biofacies change between the lower “E” member and the rest of the studied samples. Palynofacies analysis (kerogen quality and quantity) indicates the presence of oil- and gas-prone materials (kerogen types I and II/III, respectively), and implies reducing marine paleoenvironmental conditions. Detailed carbon stable isotopic and organic carbon analyses indicate that fluctuations in the δ 13C org profile across the Abu Roash upper “G”, “F”, and lower “E” members correspond well with changes in TOC values. A positive δ 13C org excursion (∼2.01‰) believed to mark the short-term global OAE2 was identified within the organic-rich shaly limestone in the basal part of the Abu Roash “F” member. This excursion also coincides with the peak TOC measurement (24.61 wt.%) in the samples.

Turonian Rudist Facies from Abu Roash area, North Western Desert, Egypt

Five radiolitid rudist species are described from the Turonian sequence of Abu Roash area. They are recognized in three rudist biostromes that occur in two informal members of Abu Roash Formation; the Rudist- and the Actaeonella-bearing limestone–marl members. The three biostromes show autochthonous and parautochthonous fabrics and moderate to high packing potential. The first rudist biostrome at the base of the Rudist-bearing limestone–marl member (Middle Turonian) contains Durania gaensis, Praeradiolites ponsianus and Bournonia fourtaui. The second biostrome in the same member consists of Bournonia roashensis. The third biostrome that recognized in the Actaeonella-bearing limestone–marl member (Late Turonian) consists of Durania arnaudi. Rudist biostromes in the Rudist-bearing limestone–marl member were deposited on subtidal rudist shoals with moderate to high energy versus that of the Actaeonella-bearing limestone–marl member that deposited in low to moderate energy on deeper part of subtidal rudist shoals. The exposed Turonian succession at Abu Roash area could be divided into three depositional sequences bounded by three sequence boundaries (paleosols and angular unconformity). The first rudist biostrome in the Rudist-bearing limestone–marl member represents the lower part of the transgressive systems tract of the first depositional sequence. The deepening upward trend of the transgressive systems tract is due to increase of accommodation space in transgressive context during relative sea-level rise episode. On the other hand, the second rudist biostrome in the Rudist-bearing limestone–marl member and the third rudist biostrome in the Actaeonella-bearing limestone–marl member are in shallowing-upward set sequence forming the highstand systems tract of the first and third depositional sequences. This indicates that, the accommodation space was being filled more rapidly than was being created during the highstand stage.

South Alamein petroleum system (Western Desert, Egypt)

ABSTRACT The South Alamein study area is located in the Western desert of Egypt between the prolific petroleum trends of Razzak-Alamein and Baharriya. The petroleum system of the area has been evaluated within an exploration framework. Potential source rocks in the Cretaceous Alam El Bueib and Abu Roash Formations and the Cenozoic Apollonia Formation display good petroleum potential; however, they are thermally immature over a large part of the studied area. Compilation of existing data and new measurements have been carried out to determine the initial source potential of the Jurassic Khatatba Formation source rock as well as its kinetic parameters for hydrocarbon generation. Results show that maturation of the Jurassic source rock does not occur below 140 °C or a vitrinite reflectance of around 0.9%. This combination of temperature and vitrinite reflectance is not unusual for a mixed type II-type III source rock, but has crucial implications for exploration in the area. The main hydrocarbon kitchens are located northward of the study area and migration to the south began around 40 Ma ago. The hydrocarbons are primarily trapped in the crest of the Mesozoic tilted blocks. It is believed that both migration and trapping have been influenced by fault hydraulic behaviour. Since this behaviour is complex, a sensitivity analysis was carried out on the migration pathway compared with the fault sealing factor to understand the filling history of the structures.

The Geochemical Correlation of Oils and Source Rock Extracts of Some Wells in the North Western Desert, Egypt

Many parameters, such as saturates (%), saturates/aromatics ratio, Cmax, C21 + C22/C28 + C29, CPI, pristane/phytane, pristane/n-C17, and pristane + n-C17/phytane + n-C18, obtained from liquid and gas chromatographic analyses are used for geochemical correlation of “10” oil and “4” extracts samples from wells Umbarka-14, Kalabsha-1, Meleiha-4, El Kharita-1, Badr El Din-1,3,4, WD-19, 33 and Abu Gharadig-12 in the North Western Desert. The results revealed that there is a close genetic relationship and remarkable similarities in the origin and maturation for the oils and extracts of the Khatatba and Alam El Bueib source rocks. In contrast, Abu Roash and Bahariya formations show no correlation with the oil. This indicates that Khatatba and Alam El Bueib source rocks seem to act as a source and reservoir for oil generation in the studied wells.