bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lithostratigraphy and Depositional History of Part of the Midyan Region, Northwestern Saudi Arabia
Authors: Hughes G. Wyn , Grainger David J. , Abu-Bshait Abdul-Jaleel , Abdul-Rahman M. Jarad 
Published: October 2021

ABSTRACT
The Midyan region provides a unique opportunity in which to examine exposures of the Upper Cretaceous and Neogene sedimentary succession. Recent investigations have yielded new interpretations of its depositional environments, stratigraphic relationships, and structure. In this paper, all the lithostratigraphic units of the Midyan succession are considered to be informal in advance of an on-going process of formalization.
The region is bounded to the north and northeast by mountains of Proterozoic rocks and to the west and south by the Gulf of Aqaba and the Red Sea, respectively. The Wadi Ifal plain occupies most of the eastern half of the region, beneath which is a thick sedimentary succession within the Ifal basin. The oldest sedimentary rocks are the fluviatile Upper Cretaceous Adaffa formation and marine siliciclastics and carbonates of the lower Miocene Tayran group, unconformable on the Proterozoic basement. The Tayran group is unconformably overlain by the deep-marine lower Miocene Burqan formation that, in turn, is overlain by marine mudstones, carbonates, and evaporites of the middle Miocene Maqna group. The poorly exposed middle Miocene Mansiyah and middle to upper Miocene Ghawwas formations consist of marine evaporites and shallow to marginal marine sediments, respectively. The youngest rocks are alluvial sands and gravels of the Pliocene Lisan formation.
A complex structural history is due to Red Sea Oligocene-Miocene extension tectonics, and Pliocene-Recent anti-clockwise rotation of the Arabian Plate relative to Africa on the Dead Sea Transform Fault. The Upper Cretaceous succession is a probable pre-rift unit. The Oligocene?-Miocene syn-rift 1 phase of continental extension caused slow subsidence (Tayran group). Syn-rift 2 was an early Miocene phase of rapid subsidence (Burqan formation) whereas syn-rift 3 (early to middle Miocene) was another phase of slow deposition (Maqna group). The middle to late Miocene syn-rift 4 phase coincided with the deposition of the Mansiyah and Ghawwas formations. The Lower Pliocene to Recent succession is related to the drift (post-rift) phase during which about 45 kilometers of sinistral movement occurred on the Dead Sea Fault.
The structural control on sedimentation is evident: the Ifal basin was formed by east-west lithospheric extension; pull-apart basins occur along major left-lateral faults on the eastern coast of the Gulf of Aqaba; and basin-bounding faults controlled deposition of the Burqan, Ghawwas, and Lisan formations. Pliocene to Recent earth movements may be responsible for activating salt diapirism in the Ifal basin. Extensive Quaternary faulting and regional uplift caused the uplift of coral reefs to at least 6 to 8 meters above sea level.
Recognition and Interpretation of Polygenic Discontinuity Surfaces in the Middle Cretaceous Shu’aiba, Nahr Umr, and Natih Formations of Northern Oman
Authors: Immenhauser Adrian , Creusen Anouk , Esteban Mateu , Vonhof Hubert B. 
Published: October 2021

ABSTRACTDiscontinuity surfaces that recorded superposition of marine hardground and subaerial exposure stages are common in the Middle Cretaceous of northern Oman. These surfaces formed during periods of rapid sea-level drop. The marine hardground stages are dominant in the field, whereas the subaerial exposure stage is documented in circumstantial petrographic, geochemical, and biological evidence. The record of a shoaling phase prior to exposure is commonly subtle and incomplete; supratidal deposits are conspicuously absent. Porosity in the limestones underlying the discontinuities is rearranged during subaerial exposure and subsequent burial and hence the permeability of large volumes of limestone is affected at a variety of scales. During marine hardground stages, carbonate cements, iron oxides, and manganese occludes some of the existing pore space. During burial, these intervals may thus have acted as either seals or efficient conduits of fluid flow. The surfaces under study in the Shu’aiba, Nahr Umr, and Natih formations are spaced ten to few tens of meters apart and many of them were traced laterally over distances of 100 kilometers and more between sections at Jebel Akhdar and in the Foothills. This implies that they play an important, but poorly understood role in compartmentalization of carbonate reservoir rocks.
A 9C-2D Land Seismic Experiment for Lithology Estimation of a Permian Clastic Reservoir
Authors: Macrides Costas G. , Kelamis Panos G. 
Published: October 2021

ABSTRACT
In 1997, a nine-component shear wave experiment, the first of its kind in the country, was carried out in central Saudi Arabia over the Umm Jurf and Usaylah fields. The seismic source consisted of conventional and shear-wave vibrators. The objective of the experiment was to test the feasibility of using multicomponent seismic data for lithology estimation and differentiation between sand, silt and shale in the clastic Permian Unayzah Formation. The estimates of average ratios of compressional to shear-wave velocities for the target interval are encouraging as they identified lithologic variations within the Unayzah that are in agreement with the available well logs. Specifically, the seismic ratios correlate satisfactorily with sand/(silt+shale) ratios measured in key wells.
Origin of the Arabian Plate Structures: Amar Collision and Najd Rift
Authors: Al-Husseini Moujahed I. 
Published: October 2021

ABSTRACT
The regularly spaced, N-trending Summan Platform, Khurais-Burgan Anticline, En Nala (Ghawar) Anticline and Qatar Arch in the eastern part of the Arabian Plate appear to have formed during the Precambrian Amar Collision between about 640 and 620 million years ago. This collision occurred along the N-trending Amar Suture (that bisects the Arabian Peninsula at about longitude 45 E) when the Rayn micro-plate in the east was fused to the western part of the Arabian Craton. The great anticlines are bounded by the NE-trending Wadi Batin Fault and NW-trending Abu Jifan Fault that converge on the Amar Suture. Deep wells drilled into these anticlines intersected deformed metasediments that are dated as syn-collisional. The Amar Collision was followed by a widespread extensional collapse of the Arabian-Nubian Shield between about 620 and 530 million years ago. During the final extensional stage, between about 570 and 530 million years ago, the NW-trending Najd Fault System dislocated the Arabian Shield left-laterally by about 250 to 300 kilometers. This dislocation appears to complement NE-oriented intra-continental rifts in Oman, Pakistan, Zagros Mountains and the Arabian Gulf. In these rift basins there accumulated thick sequences of clastic and carbonate rocks and salt, such as the Ara Group in Oman, Salt Range Formation in Pakistan, and Hormuz Series in the Arabian Gulf and Zagros Mountains. During the extensional collapse, the N-trending anticlines probably remained elevated as elongated horsts bounded by normal faults. The intervening subsiding grabens accumulated syn-rift sediments including the Hormuz Salt, and form an inter-fingering pattern between the great N-trending anticlines. The Precambrian anticlines, together with the syn-rift salt form the foundations of most of the hydrocarbon traps in the Arabian Plate.
Predictive Modelling of Naturally Fractured Reservoirs Using Geomechanics and Flow Simulation
Authors: Bourne Stephen J. , Rijkels Lex , Stephenson Ben J. , Willemse Emanuel J.M. 
Published: October 2021

ABSTRACT
To optimise recovery in naturally fractured reservoirs, the field-scale distribution of fracture properties must be understood and quantified. We present a method to systematically predict the spatial distribution of natural fractures related to faulting and their effect on flow simulations. This approach yields field-scale models for the geometry and permeability of connected fracture networks. These are calibrated by geological, well test and field production data to constrain the distributions of fractures within the inter-well space. First, we calculate the stress distribution at the time of fracturing using the present-day structural reservoir geometry. This calculation is based on a geomechanical model of rock deformation that represents faults as frictionless surfaces within an isotropic homogeneous linear elastic medium. Second, the calculated stress field is used to govern the simulated growth of fracture networks. Finally, the fractures are upscaled dynamically by simulating flow through the discrete fracture network per grid block, enabling field-scale multi-phase reservoir simulation. Uncertainties associated with these predictions are considerably reduced as the model is constrained and validated by seismic, borehole, well test and production data. This approach is able to predict physically and geologically realistic fracture networks. Its successful application to outcrops and reservoirs demonstrates that there is a high degree of predictability in the properties of natural fracture networks. In cases of limited data, field-wide heterogeneity in fracture permeability can be modelled without the need for field-wide well coverage.
Tectonic and Geologic Evolution of Syria
Authors: Brew Graham , Barazangi Muawia , Al-Maleh Ahmad Khaled , Sawaf Tarif 
Published: October 2021

ABSTRACT
Using extensive surface and subsurface data, we have synthesized the Phanerozoic tectonic and geologic evolution of Syria that has important implications for eastern Mediterranean tectonic studies and the strategies for hydrocarbon exploration. Syrian tectonic deformation is focused in four major zones that have been repeatedly reactivated throughout the Phanerozoic in response to movement on nearby plate boundaries. They are the Palmyride Mountains, the Euphrates Fault System, the Abd el Aziz-Sinjar uplifts, and the Dead Sea Fault System. The Palmyrides include the SW Palmyride fold and thrust belt and two inverted sub-basins that are now the Bilas and Bishri blocks. The Euphrates Fault System and Abd el Aziz-Sinjar grabens in eastern Syria are large extensional features with a more recent history of Neogene compression and partial inversion. The Dead Sea transform plate boundary cuts through western Syria and has associated pull-apart basins.
The geological history of Syria has been reconstructed by combining the interpreted geologic history of these zones with tectonic and lithostratigraphic analyses from the remainder of the country. Specific deformation episodes were penecontemporaneous with regional-scale plate-tectonic events. Following a relatively quiescent early Paleozoic shelf environment, the NE-trending Palmyride/Sinjar Trough formed across central Syria in response to regional compression followed by Permian-Triassic opening of the Neo-Tethys Ocean and the eastern Mediterranean. This continued with carbonate deposition in the Mesozoic. Late Cretaceous tectonism was dominated by extension in the Euphrates Fault System and Abd el Aziz-Sinjar Graben in eastern Syria associated with the closing of the Neo-Tethys. Repeated collisions along the northern Arabian margin from the Late Cretaceous to the Late Miocene caused platform-wide compression. This led to the structural inversion and horizontal shortening of the Palmyride Trough and Abd el Aziz-Sinjar Graben.
A crustal transect across the Oman Mountains on the eastern margin of Arabia
Authors: Al-Lazki Ali I. , Seber Dogan , Sandvol Eric , Barazangi Muawia 
Published: October 2021

ABSTRACT
The unique tectonic setting of the Oman Mountains and the Semail Ophiolite, together with ongoing hydrocarbon exploration, have focused geological research on the sedimentary and ophiolite stratigraphy of Oman. However, there have been few investigations of the crustal-scale structure of the eastern Arabian continental margin. In order to rectify this omission, we made a 255-km-long, southwesterly oriented crustal transect of the Oman Mountains from the Coastal Zone to the interior Foreland via the 3,000-m-high Jebel Akhdar. The model for the upper 8 km of the crust was constrained using 152 km of 2-D seismic reflection profiles, 15 exploratory wells, and 1:100,000- to 1:250,000-scale geological maps. Receiver-function analysis of teleseismic earthquake waveform data from three temporary digital seismic stations gave the first reliable estimates of depth-to-Moho. Bouguer gravity modeling provided further evidence of depths to the Moho and metamorphic basement.
Four principal results were obtained from the transect. (1) An interpreted mountain root beneath Jebel Akhdar has a lateral extent of about 60 km along the transect. The depth-to-Moho of 41 to 44 km about 25 km southwest of Jebel Akhdar increased to 48 to 51 km on its northeastern side but decreased to 39 to 42 km beneath the coastal plain farther to the northeast. (2) The average depth to the metamorphic basement was inferred from Bouguer gravity modeling to be 9 km in the core of Jebel Akhdar and immediately to the southwest. A relatively shallow depth-to-basement of 7 to 8 km coincided with the Jebel Qusaybah anticline south of the Hamrat Ad Duru Range. (3) Based on surface, subsurface, and gravity modeling, the Nakhl Ophiolite block extends seaward for approximately 80 km from its most southerly outcrop. It has an average thickness of about 5 km, whereas ophiolite south of Jebel Akhdar is only 1 km thick. The underlying Hawasina Sediments are between 2 and 3 km thick in the Hamrat Ad Duru Zone, and 2 km thick in the Coastal Zone. (4) Southwest of Jebel Akhdar, reactivated NW-oriented strike-slip basement faults that deformed Miocene to Pliocene sediments were inferred from the interpretation of seismic reflection profiles.
Accurate reservoir characterization to reduce drilling risk in Khuff-C carbonate, Ghawar field, Saudi Arabia
Authors: Dasgupta Shiv N. , Hong Ming-Ren , Al-Jallal Ibrahim A. 
Published: October 2021

ABSTRACT
The Khuff-C reservoir in the Ghawar field is a stratified sequence of cyclic carbonate-evaporite deposits within the Permian Khuff Formation. The reservoir is heterogeneous, complex, and influenced by syndepositional diagenesis. Wells drilled into the Khuff-C in the ‘Uthmaniyah sector of Ghawar are usually prolific producers of non-associated gas but some have intersected poor-quality reservoir intervals with little or no gas production. The Khuff-C reservoir rocks were deposited in a peritidal setting where slight changes in sea level created locally exposed highs. The exposure in an arid climate resulted in outliers of porosity occlusion formed by evaporite cements within the Khuff-C reservoir. The outliers are variably sized and randomly distributed and the challenge is to predict their occurrence in order to avoid them in development drilling. Inverse modeling of the ‘Uthmaniyah 3-D seismic data has identified the tight-porosity outliers as areas of anomalously high acoustic impedance. Integration of 3-D seismic analyses with petrophysical and other well data has improved the reservoir characterization and reduced the drilling risk.
A successful 3-D seismic survey over Bahrain Island
Authors: Postel Jean-Jacques , Mukhtar Abdul Nabi , Feugère Philippe 
Published: October 2021

ABSTRACT
Environmental constraints are critical issues for land seismic operations and require the development of appropriate equipment and methods. In 1998, Compagnie Générale de Géophysique (CGG) acquired and processed seamless seismic data on behalf of the Bahrain Petroleum Company (Bapco) from a complex field on the Island of Bahrain. The operation ran smoothly in spite of the difficulty of working amongst pipelines, wells, and other oil and gas installations; scarps and sabkhas; urban areas; a zoo, golf course, and racecourse; an oil refinery and aluminum smelter; and other industrial and commercial facilities. The survey deployed a wide range of recording equipment including two sets of vibrators and a combination of radio and cable telemetry recording systems, and a fleet-management system.
The successful completion of the survey was achieved through dedicated teamwork. The key elements were as follows: (1) collecting the correct baseline information; (2) detailed planning of the timeframe, human and material resources, adaptation of acquisition techniques to varying circumstances, and health and safety requirements; (3) continuous monitoring of external conditions and the impact of the operation on the environment, in full consultation with the appropriate authorities; (4) maximum flexibility in the field operations so as to allow for changing conditions and unforeseen events; and (5) close partnership between CGG and Bapco at all stages of the project.
A joint CGG/Bapco team designed sophisticated processing methods, with top priority being given to the numerous surface heterogeneities. In particular, the recording of an intensive up-hole survey allowed a dedicated team at CGG in France to compute a robust subsurface model and a precise set of primary statics. Seven velocity layers from the Quaternary sandstone to the base of the calcareous and dolomitic Eocene were mapped. These showed significant lateral and vertical velocity variations within identified geological units. Surface-consistent signal processing with calibration to well data was used to compensate for the variations. Other critical processing steps included detailed velocity control, the application of dip moveout routines with acquisition-irregularity-compensation schemes, Radon demultiples and 3-D algorithms, designed for optimal de-noising and imaging.
These combined efforts led to the delivery of a final 3-D migrated block. As a result, a complete reinterpretation of the area was possible that significantly increased the estimated recoverable oil reserves (particularly by-passed oil) in the Awali field.
Structural setting and tectonic evolution of the Bahariya Depression, Western Desert, Egypt
Authors: Moustafa Adel R , Saoudi Ati , Moubasher Alaa , Ibrahim Ibrahim M , Molokhia Hesham , Schwartz Bernie 
Published: October 2021

ABSTRACT
An integrated surface mapping and subsurface study of the Bahariya Depression aided the regional subsurface interpretation. It indicated that four major ENE-oriented structural belts overlie deep-seated faults in this part of the ‘tectonically stable’ area of Egypt. The rocks of the Bahariya area were deformed in the Late Cretaceous, post-Middle Eocene, and Middle Miocene-and subsurface data indicated an early Mesozoic phase of normal faulting. The Late Cretaceous and post-Middle Eocene deformations reactivated the early normal faults by oblique slip and formed a large swell in the Bahariya region. The crest was continuously eroded whereas its peripheries were onlapped by Maastrichtian and Tertiary sediments. The tectonic evolution of the Bahariya region shows great similarity to the deformation of the ‘tectonically unstable’ area of the northern Western Desert where several hydrocarbon fields have been discovered. This similarity may indicate that the same phases of deformation could extend to other basins lying in the ‘tectonically stable’ area, such as the Asyut, Dakhla, Nuqura, and El Misaha basins.
Lithological and structural evolution of the northern sector of Dukhan anticline, Qatar, during the early Tertiary: with special reference to sequence stratigraphic bounding surfaces
Authors: Dill Harald G. , Nasir Sobhi , Al-Saad Hamad 
Published: October 2021

ABSTRACTEarly Tertiary sediments are widely exposed in Qatar and only in coastal areas and a few places inland do Holocene deposits mask them. The variable resistance to weathering of the Tertiary sediments is responsible for the general low-relief landscape interspersed with flat-topped hills, the most prominent of which are in western Qatar where they are the surface expression of the Dukhan anticline. The early Tertiary was a time of shallow-marine sedimentation and several transgressive and regressive cycles occurred. Sedimentation began on a dolomitic carbonate shelf, which gave way to a mixed carbonate-siliciclastic shelf that became increasingly calcitic. Coarsening-upward sequences with fine-grained muddy sediments at the base and grainstones and boundstones on top attested to a cyclic change in the energy regime. Small-scale cycles and major unconformities resulted from eustatic sea-level changes. In the Dukhan study area, the most prominent sequence boundary was near the Ypresian-Lutetian boundary. Following this hiatus, a Lutetian transgressive system tract evolved that was terminated by a maximum flooding surface correlated with the named MFS Pg20. Minor unconformities and NE-trending faults of post-Miocene age resulted from the interplay of local diapiric salt movements in the Dukhan anticline and a regionally changing stress field. Extensional faulting was succeeded by a compressional phase that caused the reactivation of some normal faults as steeply dipping reverse faults.Diagenetic processes and the pervasive etching of the landscape formed ferrous, siliceous, and gypsiferous duricrusts. Phosphate was reworked and concentrated above the Ypresian-Lutetian unconformity. Ferricretes were derived from iron-bearing phyllosilicates and disulfides. Ferric iron-oxide hydrates were the result of oxidizing conditions but their parent material furnished evidence of less-oxygenated conditions and a rising sea level during the Lutetian transgression. The studies provided information on the economic potential of aggregates, clay, hydraulic binders, and building stones, and the prediction of subsidence-prone areas.
Lateral clay injection into normal faults
Authors: van der Zee Wouter , Urai Janos L. , Richard Pascal D. 
Published: October 2021

ABSTRACT
The clay content of fault gouge is one of the main factors controlling transport and mechanical properties of a fault zone. This paper addresses the process of lateral clay injection into normal faults, which is one of the many processes contributing to the development of clay smear, and can lead to local enrichment of clay in a fault gouge. We combined field observations with geomechanical models to quantify the parameters leading to lateral clay injection into fault zones. Detailed field study shows that a releasing fault bend in a clay layer is required for clay injection to occur. The clay injection process is often associated with the formation of a branch in the fault and the development of a “squeezing block” which injects the clay into the fault zone. A simple analytical model predicts the onset of clay injection when C = σ'v (1 - sin ϕ) / (2 cos ϕ), where C is cohesion (MPa), σ'v is vertical stress (MPa) and ϕ (°) is friction angle. More detailed analysis using 2-D geomechanical finite element models is in good agreement with the analytical models and allows study of the system at higher fault throw. Results of sandbox models containing layers of an elastoplastic clay analogue also compare well with field observations and numerical models, and show the initiation of the releasing step and the evolution of the clay injection process with increasing fault throw. Using our results it is possible to predict the likelihood of lateral clay injection in the subsurface, in settings like the Gharif formation of the Haushi group of Central and South Oman or the Natih formation of North Oman. This requires an estimation of the mechanical properties of the clays at the time of faulting; data which can be obtained from wireline logs and cuttings. This approach to fault seal analysis emphasizes the mechanical aspects of the clay smear process, in addition to the kinematics which were considered in previous analyses. Its application should lead to improved prediction of fault seal processes in the subsurface.