bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Arab Formation in central Abu Dhabi: 3-D reservoir architecture and static and dynamic modeling
Authors: Grötsch Jürgen , Suwaina Omar , Ajlani Ghiath , Taher Ahmed , El-Khassawneh Reyad , Lokier Stephen , Coy Gordon , Weerd Erik van der , Weerd der , Masalmeh Shehadeh , Dorp Johan van 
Published: October 2021

ABSTRACT
A 3-D geological model of the Kimmeridgian-Tithonian Manifa, Hith, Arab, and Upper Diyab formations in the area of the onshore Central Abu Dhabi Ridge was based on a newly established sequence stratigraphic, sedimentologic, and diagenetic model. It was part of an inter-disciplinary study of the large sour-gas reserves in Abu Dhabi that are mainly hosted by the Arab Formation. The model was used for dynamic evaluations and recommendations for further appraisal and development planning in the studied field.
Fourth-order aggradational and progradational cycles are composed of small-scale fifth-order shallowing-upward cycles, mostly capped by anhydrite within the Arab-ABC. The study area is characterized by a shoreline progradation of the Arab Formation toward the east-northeast marked by high-energy oolitic/bioclastic grainstones of the Upper Arab-D and the Asab Oolite. The Arab-ABC, Hith, and Manifa pinch out toward the northeast. The strongly bioturbated Lower Arab-D is an intrashelf basinal carbonate ramp deposit, largely time-equivalent to the Arab-ABC. The deposition of the Manifa Formation over the Arab Formation was a major back-stepping event of the shallow-water platform before the onset of renewed progradation in the Early Cretaceous.
Well productivity in the Arab-ABC is controlled mainly by thin, permeable dolomitic streaks in the fifth-order cycles at the base of the fourth-order cycles. This has major implications for reservoir management, well completion and stimulation, and development planning. Good reservoir properties have been preserved in the early diagenetic dolomitic streaks. In contrast, the reservoir properties of the Upper Arab-D oolitic/bioclastic grainstones deteriorate with depth due to burial diagenesis.
A rock-type scheme was established because complex diagenetic overprinting prevented the depositional facies from being directly related to petrophysical properties. Special core analysis and the attribution of saturation functions to static and dynamic models were made on a cell-by-cell basis using the scheme and honoring the 3-D depositional facies and property model. The results demonstrated the importance of integrating sedimentological analysis and diagenesis with rock typing and static and dynamic modeling so as to enhance the predictive capabilities of subsurface models.
Surface-piercing salt domes of interior North Oman, and their significance for the Ara carbonate ‘stringer’ hydrocarbon play
Authors: Peters Jeroen M. , Filbrandt Jacek B. , Grotzinger John P. , Newall Mark J. , Shuster Mark W. , Al-Siyabi Hisham A. 
Published: October 2021

ABSTRACT
The six surface-piercing salt domes of interior North Oman form prominent topographic and geological features in an otherwise flat, rocky desert environment. These domes in the central part of the Ghaba Salt Basin have been known since the 1950s but very little data has been published on them. Our geological survey in 2001 provided significant new lithological, stratigraphic, and sedimentological information on the rocks exposed in the domes. This paper provides a comprehensive overview of the morphology, geometry, structural geology and geological evolution of the salt domes. Furthermore, it incorporates relevant information from unpublished subsurface studies to place the new geological field data in the context of ongoing exploration for deep hydrocarbon plays in Oman.
A wide variety of rocks is exposed in the salt domes: carbonates, clastics (conglomerates, sandstones, siltstones and clays), volcanics, evaporites and ‘caprocks’. Constituent rocks and structural style vary considerably from one dome to another, but at the surface the main lithological elements of the diapirs are carbonates and evaporites of the ‘Infracambrian’ (Late Precambrian to Early Cambrian) Ara Group, the uppermost unit of the Huqf Supergroup. Very large exotic blocks of bedded Ara carbonates––commonly hundreds of meters long––are well-exposed and form distinctive hills and ridges, thus allowing detailed field observations on intra-salt carbonate ‘stringers’ that have been carried up by rising diapiric salt. A close correlation exists between the facies of the carbonate exotics in the salt domes and Ara ‘stringer’ carbonates penetrated and extensively cored in recent deep exploration wells in the South Oman Salt Basin. This demonstrates the regional significance of the salt domes for the intra-salt ‘stringer’ hydrocarbon play in Oman. Our work has implications for the prospectivity of other ‘Infracambrian’ evaporite basins in Oman, and possibly also for time-equivalent (‘Hormuz’) salt basins elsewhere in the Middle East.
The Lower Cretaceous carbonate slope-to-platform-margin succession near Khatt, United Arab Emirates: sedimentary facies and depositional geometries
Authors: Eilrich Bernd , Grötsch Jürgen 
Published: October 2021

ABSTRACT
The Jurassic and Lower Cretaceous carbonate succession exposed near Khatt provides exceptional conditions for the investigation of sedimentary facies and depositional geometries in a carbonate slope-to-platform-margin setting. A coarsening-upward sequence in Lower Cretaceous limestones indicates decreasing depth of deposition and platform progradation. A pronounced shedding of sediments containing reefal fragments occurs in a slope environment with a well exposed basin-to-platform transect. The carbonate succession consists of mudstone, wackestone, grainstone, coarse rudstone with conglomerate/breccia interbeds, and framestone at the top. The depositional architecture is characterized by the abundance of massive sheet- or channel-like limestone bodies within thinly bedded and generally uniform strata. Quantitative analysis of many carbonate channel deposits and their geometries measured in outcrop led to the distinction of two major types. Type I channel deposits are thin (0.3 to 5 m) but massive, and are commonly irregularly shaped in cross-section. They are as much as 200 m wide. Type I channel deposits are characterized by a wide size range of skeletal and non-skeletal carbonate components. Type II channel deposits, by contrast, are more regularly bedded and have much larger thickness-to-width ratios, in general close to 1:10. Furthermore, they are composed of packstone to grainstone calciturbidite sediments. As with some sheet deposits, they can be correlated through most of the 5.5-km-long Khatt outcrop. Stratigraphically, however, their occurrence is very much restricted, indicating significant alternation of depositional styles as a consequence of changing carbonate platform production and changing sedimentary environments. The data presented here can serve as input for 3-D geological modeling of equivalent depositional environments in the subsurface. They can also be applied to object-based deterministic and stochastic facies modeling.
Reconstruction of the original organic richness in weathered Silurian shale outcrops (Murzuq and Kufra basins, southern Libya)
Authors: Lüning Sebastian , Kolonic Sadat , Loydell David K. , Craig Jonathan 
Published: October 2021

ABSTRACT
The early Silurian in North Africa and Arabia was characterised by widespread deposition of organic-rich shales in palaeo-depressions. The unit represents an important hydrocarbon source rock in the region and can be detected easily in well logs because of strong uranium-related natural radiation. In exposures, however, organic matter is commonly heavily oxidised through weathering so that identification of the unit in the field is difficult. Uranium and pyrite framboids appear to be less vulnerable to weathering and may be used to identify intervals of originally organic-rich shales in exposures. Framboids are discrete spheroidal aggregates of pyrite microcrystallites and their size distribution is thought to be controlled by palaeo-depositional bottom-water redox-conditions. Analyses of fresh Silurian organic-rich shales from a core reveal a close correspondence, for the most part, between total organic carbon, total gamma-ray response, uranium content (as determined by spectral gamma-ray) and framboid parameters. Feasibility tests of the concept have been carried out at two exposures in southern Libya and may form the basis for improved Silurian organic-rich shale distribution maps and more precise age models for Silurian organic-rich depositional phases in northern Gondwana.
Aptian faulting in the Haushi-Huqf (Oman) and the tectonic evolution of the southeast Arabian platform-margin
Authors: Montenat Christian , Barrier Pascal , Soudet Henri J. 
Published: October 2021

ABSTRACT
A major upper Aptian unconformity is recorded on the eastern Arabian Platform, between the lower Aptian Qishn limestone and the Albian Nahr Umr marls. The study of this hiatus, in the western homocline of the Haushi-Huqf Uplift (Eastern Central Oman) provides new data about the evolution of the eastern Arabian Platform during middle Cretaceous times. The limestones of the Qishn formed a shoaling sequence, mainly composed of matrix-rich, coarse-grained sediment with small rudistids and algal build-ups, that led to a subemergent environment. A third-order sequence is recognized in the Qishn platform carbonates, which is partitioned into three minor sequences. The Qishn carbonate was subjected to pre-lithification normal faulting. A thick ferrugineous crust (hardground) covered the top surface of the Qishn as well as the faultscarps before they were buried under the Albian Nahr Umr marls. The faults are dominantly NW-trending, SW-facing, normal faults. The significance of the faulting remains hypothetical. The syndiagenetic NW-SE normal faults may correspond to ‘en-echelon’ faults, combined with a sinistral movement of the Haushi-Nafun Fault (HNF). The HNF acted as a left-lateral, strike-slip fault during late Cretaceous, pre-Maastrichtian times. This movement possibly began earlier, during the late Aptian. It could be related to the dynamics of the eastern Arabian margin during the Cretaceous (Masirah transform margin). There are some indications testifying to the activity of the Masirah transform fault during the early-middle Cretaceous. The margin kinematics may be responsible for the reactivation of nearby large faults affecting the platform basement (for instance the HNF). A slight sinistral reactivation of the HNF may have induced the development of the Aptian NW-trending normal faults. Moreover, the occurrence of early Cretaceous strike-slip movements in the Arabian Platform have already been envisaged, at a plate-scale, as a consequence of the South Atlantic extension. On this assumption, the Aptian fault blocks may have resulted from the development of a sinistral transtension along the HNF.
Sedimentary architecture of Upper Ordovician tunnel valleys, Gargaf Arch, Libya: Implications for the genesis of a hydrocarbon reservoir
Authors: Heron Daniel Le , Sutcliffe Owen , Bourgig Khalid , Craig Jonathan , Visentin Claudio , Whittington Robert 
Published: October 2021

ABSTRACT
In the Murzuq Basin, southwest Libya, as elsewhere in North Africa, Upper Ordovician glaciogenic rocks represent an important hydrocarbon reservoir. In this basin, anastomosing, potentially sand-filled palaeovalley networks within the Upper Ordovician succession have been described from seismic data that provide promising prospects for exploration. However, little is known about the origin and architecture of the palaeovalley-fills. On the Gargaf Arch, an outcrop analogue for these structures occurs and is comparable in scale to the valley networks described in the subsurface. This palaeovalley system is 30 km long with two 4 km-wide tributaries, cut into ice-distal glaciomarine mudrocks and diamictites and filled with ice-proximal sandstones and subordinate shales. It was created by subglacial meltwater erosion and glacial loading of a soft substrate during ice sheet advance. The initial stage of valley-fill involved the deposition of coarse-grained sands and conglomeratic ice-proximal, submarine outwash, as localised mass flows. The main stage of fill was characterised by axially (northerly) prograding, underflow-dominated fan lobes deposited in water depths of up to 80 m. A comparison with coeval valley systems in Mauritania, Algeria, Saudi Arabia and Jordan is provided that highlights the variable regional character of palaeovalley-fills and the influence that water-depth had on architecture.
Albian sea-level cycles in Oman: the ‘Rosetta Stone’ approach
Authors: Immenhauser Adrian , Matthews Robley K. 
Published: October 2021

ABSTRACT
The Albian Nahr Umr Formation of Oman (bounded by the Shu’aiba and Natih formations) recorded high-, intermediate, and low-amplitude regressive-transgressive events. In order to reconstruct these sea-level oscillations in a semi-quantitative manner, six measured sections from different bathymetric positions were investigated across a 500-km-transect. Between these sections, discontinuity surfaces, indicative of sea-level fall and subsequent rise, were correlated. In order to asses the underlying causes of sea-level oscillations we compared the amplitudes and frequencies of the Oman events with published amplitudes and frequencies of factors that affect the water volume in the Earth’s oceans, or the shape of oceanic basins. We used the spatial array and field, chemical and petrographic properties of these rocks as a key for unraveling the unknown factors that caused sea-level change. We concluded that sea-level cycles in Oman either reflect unknown processes we do not understand, or changes in continental ice volumes. Thus, we give serious attention to the concept of orbital forcing and glacio-eustasy.
By modeling an orbital forcing sea-level curve for the Albian, and combining it with stratigraphic modeling of sedimentation response to sea-level change, a data-model comparison was possible. The match of our data-model comparison is expectedly not perfect but surprisingly good, and this approach is definitely worth pursuing. One of the main data-model differences is that the model exclusively reflects the orbital-forcing signal, whereas the Albian rock record in Oman is expected to represent an array of climatic, tectonic and local sedimentological factors. Nevertheless, the good data-model match supports the hypothesis that glacio-eustasy was the dominant driver of Albian sea-level change in Oman. This outcome might prove to be controversial in that it suggests a re-evaluation of the Cretaceous as a period of global, continuous climatic warmth, without significant ice shields at the poles.
This interaction has highlighted the many differences between the stratigrapher’s perspective and modeler’s perspective. There are good and bad points to both perspectives, which we point out and attempt to reconcile here.
Petroleum generation and migration in the Mesopotamian Basin and Zagros Fold Belt of Iraq: results from a basin-modeling study
Authors: Pitman Janet K. , Steinshouer Douglas , Lewan Michael D. 
Published: October 2021

ABSTRACT
A regional 3-D total petroleum-system model was developed to evaluate petroleum generation and migration histories in the Mesopotamian Basin and Zagros fold belt in Iraq. The modeling was undertaken in conjunction with Middle East petroleum assessment studies conducted by the USGS. Regional structure maps, isopach and facies maps, and thermal maturity data were used as input to the model. The oil-generation potential of Jurassic source-rocks, the principal known source of the petroleum in Jurassic, Cretaceous, and Tertiary reservoirs in these regions, was modeled using hydrous pyrolysis (Type II-S) kerogen kinetics. Results showed that oil generation in source rocks commenced in the Late Cretaceous in intrashelf basins, peak expulsion took place in the late Miocene and Pliocene when these depocenters had expanded along the Zagros foredeep trend, and generation ended in the Holocene when deposition in the foredeep ceased. The model indicates that, at present, the majority of Jurassic source rocks in Iraq have reached or exceeded peak oil generation and most rocks have completed oil generation and expulsion. Flow-path simulations demonstrate that virtually all oil and gas fields in the Mesopotamian Basin and Zagros fold belt overlie mature Jurassic source rocks (vertical migration dominated) and are situated on, or close to, modeled migration pathways. Fields closest to modeled pathways associated with source rocks in local intrashelf basins were charged earliest from Late Cretaceous through the middle Miocene, and other fields filled later when compression-related traps were being formed. Model results confirm petroleum migration along major, northwest-trending folds and faults, and oil migration loss at the surface.
Arabian Orbital Stratigraphy: Periodic Second-Order Sequence Boundaries?
Authors: Al-Husseini Moujahed , Matthews Robley K. 
Published: October 2021

ABSTRACTA simplified model of orbital-forcing suggests that the Phanerozoic Eon may be represented by 38 periodic second-order depositional sequences (DS2) each lasting about 14.58 million years (my). The DS2s are separated by second-order sequence boundaries (SB2, maximum regression surface) that should be manifested as regional stratigraphic discontinuities (unconformity, disconformity, time hiatus). To test this simple model, the Arabian succession was reviewed to identify candidate regional stratigraphic discontinuities that might be periodic at 14.58 my. Of the 38 predicted SB2s, 34 regional stratigraphic discontinuities were identified within the uncertainty of biostratigraphic-radiometric age dating, or by stratigraphic position. One SB2 could not be positioned in the succession because of ambiguous biostratigraphic dating. One was predicted within a long-lasting hiatus, and another two were predicted within an undifferentiated formation. The four unidentified SB2s reflect on the limitations of the data sample, rather than on the viability of the model.Because the stratigraphic discontinuities represent age spans with bounding ages that are at best believed to have accuracies of about ± 3.0 my, the model-data correlation was considered inconclusive. The resulting analysis, however, demonstrates that the ages in million years before present (Ma) of interpreted Arabian (and possibly global) sequence stratigraphic surfaces and depositional sequences, as estimated by biostratigraphic-radiometric dating techniques, are highly inaccurate (± 5–10 my). This conclusion suggests that presently used chronostratigraphic correlations across the Arabian Platform should be treated with great caution. The correlation of model SB2s to regional stratigraphic discontinuities, affords an alternative time scale that may eventually assist in the calibration of the biostratigraphic-radiometric time scale. An orbital-forcing time scale has a decided advantage in that it comes with precise third- and fourth-order stratigraphic predictions imbedded as sea-level fluctuations. The next level of testing is whether these orbital-forcing predictions hold up to precise correlation to stratigraphy.
Biostratigraphy of the Lower Palaeozoic Haima Supergroup, Oman; its application in sequence stratigraphy and hydrocarbon exploration
Authors: Molyneux Stewart , Osterloff Peter , Penney Randall , Spaak Pieter 
Published: October 2021

ABSTRACTThe siliciclastic Haima Supergroup (Cambrian-Silurian) on the west flank of Al Ghabah Salt Basin in Oman is currently a target for gas exploration following the discovery of significant gas reserves. An understanding of stratigraphical and facies relationships within the Haima is crucial for their exploration and exploitation, and biostratigraphy is one of the more powerful and cost-effective tools that can be deployed to aid such understanding. The biostratigraphy of the Haima Supergroup is based primarily on palynomorphs. The pre-existing biozonation, comprising conventional interval zones, is of low resolution and incorporates misconceptions over the ranges of key species. The work reported here explicitly considered the biostratigraphy of the Haima Supergroup in the context of genetic sequence stratigraphy. It shows that each of the postulated marine-flooding events in the Haima Supergroup is characterised by a unique assemblage of marine palynomorphs. Intervening strata are characterised by low-diversity and sometimes sparse marine palynomorph assemblages, often comprising only sphaeromorph acritarchs, accompanied by terrestrial cryptospores. These low-diversity assemblages indicate proximal-marine to non-marine conditions, consistent with progradation following each marine flood. The sandy prograding deposits in the Haima Supergroup form reservoirs, which are sealed by the shales and mudstones deposited by succeeding marine-flooding events. Lateral changes in marine assemblages indicate onshore-offshore relationships, and have contributed towards mapping the extent of each marine-flooding event, critical for evaluation of the potential areal extent of seals. The result is improved biostratigraphical resolution, which enables more precise correlation between wells, and which has contributed to more detailed palaeogeographical maps and to a better assessment of the distribution of reservoir-seal pairs.
Mixed Late Permian floras and related palaeoenvironments in the Khuff Formation of central Saudi Arabia
Authors: Berthelin Martine , Broutin Jean , Vaslet Denis , Le Nindre Yves-Michel , Halawani Mohammed 
Published: October 2021

ABSTRACTIn the outcrops of central Saudi Arabia, Permian flora have been recovered from the Unayzah Formation and the Midhnab Member of the Khuff Formation. The Unayzah Flora is found in the Unayzah Formation (below the Khuff Formation), and it is a true Cathaysian-Euramerican mixed palaeoflora with a probable age of Middle Permian (either Roadian or/and Wordian). The Unayzah Flora would therefore be coeval with the Gharif Flora from the Al Huqf area of Oman (uppermost Gharif Formation). The Midhnab Flora is found in the continental Midhnab Member (subunit 4) of the Khuff Formation. It is a mixed Late Permian flora related to the Gondwanan, Euramerican and Cathaysian realms. New associations of the Midhnab Flora were discovered at Jal Khartam, Jal al Watah and Wadi al Batan in the Qasim area of central Saudi Arabia. The new Midhnab Flora are systematically described here for the first time. The combination of palaeobotanical and sedimentological data led to the characterisation and organisation of the various palaeoenvironments in which each palaeofloral association was growing. Comparison between the Permian flora of Saudi Arabia, Oman, Anatolia (Turkey) and surrounding realms provides the means for reconstructing a more complete palaeogeographic setting for the Arabian Plate in a global palaeobiogeography.