bluuebunny/crossref_metadata_2025 huggingface dataset:
PENGEMBANGAN WEB SERVICE MODUL MAHASISWA PADA SISTEM INFORMASI AKADEMIK UNIVERSITAS NEGERI JAKARTA
Authors: Febrianto Widyoutomo  , Hamidillah Ajie  , Widodo
Published: October 2021

Perkembangan teknologi sebagai bagian dari inovasi yang dapat memberikan banyak kemudahan dalam berbagai bidang. Penerapan teknologi dalam bidang pendidikan mendorong terciptanya sistem informasi yang dapat mengelola berbagai data, baik data akademik maupun non-akademik. Universitas Negeri Jakarta(UNJ) menjadi salah satu perguruan tinggi yang memanfaatkan sistem informasi sebagai sarana pengelola data akademik yang dinamakan SIAKAD UNJ. SIAKAD UNJ saat ini tidak memiliki arsitektur sistem yang maksimal, sehingga belum bersifat adaptif terhadap pengembangan dan pembaruan fitur di dalam sistem. Tujuan dari penelitian ini adalah untuk menghasilkan web service yang dapat digunakan dalam SIAKAD UNJ dan memiliki sifat adaptif terhadap perubahan-perubahan di masa mendatang. Pengembangan web service SIAKAD UNJ dengan metode spiral menggunakan framework Express.js dan menghasilkan 25 endpoint. Pengujian dengan metode unit testing terhadap 25 endpoint menggunakan aplikasi bernama Postman. Hasil pengujian menunjukkan bahwa 25 endpoint yang diuji berfungsi dengan baik, dan layak digunakan sebagai sisi backend yang akan digabungkan dengan sisi frontend untuk menjadi aplikasi SIAKAD UNJ yang utuh.
Dimensões Intraorganizacionais e Funções Gerenciais no Setor Público
Authors: Coelho Fernando Souza , Valadares Josiel Lopes
Published: October 2021

Editorial e prefácio da edição especial APGS-SBAP.
The Use of Borehole Imaging Logs to Optimize Horizontal Well Completions in Fractured Water-flooded Carbonate Reservoirs
Authors: Al-Busaidi Rashid
Published: October 2021

Early water breakthrough has occurred in the Lower Cretaceous carbonate reservoirs (Aptian Shu’aiba Formation) in Yibal and Lekhwair fields, north Oman. Borehole Image logs were run in more than 10 horizontal wells in each field to investigate the role of faults and fracture systems, as well as facies variations and sedimentary features. These logs indicated the presence of highly-fractured zones with both open and cemented fractures. The fractures have orientations consistent with fault patterns interpreted from 3-D seismic data. High density fractured zones, in most cases, correspond to faults, some of which are below seismic resolution. The presence of fractures and/or fracture zones is the primary cause of early water breakthrough. Improved production performance was achieved by perforating non-fractured intervals to avoid early high water cuts.
Delineation of Organic Richness and Thermal History of the Lower Cretaceous Thamama Group, East Abu Dhabi: A Modeling Approach for Oil Exploration
Authors: Taher Ahmed A.
Published: October 2021

The source rocks of the Lower Cretaceous Thamama Group in east Abu Dhabi were identified by using wireline logs. This technique was applied to 33 wells which provided a well-sampled new regional pattern of source rock distribution and thickness. The Thamama Group includes rich source rocks in the Aptian Shu’aiba intra-shelf basin facies and a moderate source rock potential in the dense layers, especially those in the basal part of the Nasr Formation. The reconstruction of the burial and thermal histories indicates that the mature Thamama kitchens are mainly located in the eastern part of Abu Dhabi, adjacent to the foredeep basin and reached optimum maturity levels starting in the Eocene. Westward migration from these kitchens is mainly lateral and updip toward the main Thamama producing fields in central Abu Dhabi. The conclusion that the hydrocarbons migrated laterally is supported by oil to source rock correlation and the vertical distribution of hydrocarbons in the reservoirs.
Shuttle Imaging Radar Views of Some Geological Features in the Arabian Peninsula
Authors: Al-Hinai Khattab G. , Dabbagh Abdallah E. , Gardner Weston C. , Khan Muhammad A. , Saner Salih
Published: October 2021

The Space Shuttle Endeavor, carrying Shuttle Imaging Radar (SIR), has imaged selected parts of the Earth during two missions in April and October, 1994. The SIR instrument acquired remote sensing data in L, C and X bands. The main objective of the experiment was to assess the utility of radar images for multiple geologic, hydrologic and environmental applications. The geologic interpretation of the L-band image strips, over the Arabian Peninsula, reveals faults, folds, joints, details of harrats (basalt flows), karst terrain, and drainage systems beneath thin sand cover which are not visible on other remote sensing images (Landsat and SPOT) and are not shown on existing geologic maps.
Sequence Stratigraphic Modeling of the Lower Thamama Group, East Onshore Abu Dhabi, United Arab Emirates
Authors: Aziz Sabah K. , El-Sattar Mohamed M. Abd
Published: October 2021

The Lower Cretaceous (Berriasian to Valanginian) Habshan Formation (Lower Thamama Group) of Abu Dhabi was deposited on a broad carbonate shelf. In east onshore Abu Dhabi, the Habshan Formation consists mainly of limestone and dolomite reaching a thickness of more than 1,100 feet. The depositional environment ranged from shallow-water peritidal to deeper shelf basin. The integration of seismic-stratigraphic, biostratigraphic, lithostratigraphic and electric log data reveals three sequences (I to III) and three shelf edges within the Habshan Formation in east onshore Abu Dhabi. These high energy shelfal sediments prograde toward the basin to the east and northeast with their shelf edges trending north-northwest to south-southeast. The seismic data indicates that the basin was filled in the east during the Hauterivian, after the deposition of Sequence IV (equivalent to the Zakum formation). Good reservoir development is found in the carbonates deposited in the high energy environment along the shelf edge of the Habshan sequence, particularly within the oblique and sigmoidal clinoforms, whereas potential source rocks are expected to be developed basinward. This combination renders the Habshan and Zakum sequences an attractive exploration target, both as structural and stratigraphic traps. Recent exploration activity in the area established the presence of hydrocarbons within the Habshan Sequence III in east onshore Abu Dhabi.
Stratigraphic Trap in the Permian Unayzah Formation, Central Saudi Arabia
Authors: Evans Daniel S. , Bahabri Bassam H. , Al-Otaibi Ahmed M.
Published: October 2021

The recent discovery in Central Saudi Arabia of Arabian Super Light oil in 'Usaylah-1 confirms stratigraphic trap potential of the Permian Unayzah Formation. The trap is an updip pinch-out of an upper Unayzah sandstone along the eastern flank of the north-south trending Hawtah anticline. The seal is the basal shales and siltstones of the Khuff and Unayzah formations and the source rock is the Lower Silurian Qusaiba Shale. The well encountered an oil column of 31 feet in an upper Unayzah eolian dune facies. The areal distribution of the prospect was mapped with a 3-D seismic survey. Seismic horizon slices and relative amplitude maps at the target reflection clearly delineate the trap. The oil-productive Unayzah sandstone is imaged as a high-amplitude reflection in an isolated area of approximately 8 square kilometers. Seismic isochron maps are proving effective in focusing future exploration to areas of similar stratigraphic trap potential in the region.
Geographical Information System in the Exploration Environment
Authors: Abel Roger D.
Published: October 2021

Geographical Information System (GIS) technology has been implemented at Petroleum Development Oman (PDO) within the Exploration Topographic Department, in support of various applications over the previous few years. The primary uses for GIS technology within Exploration are in providing users with simple access to corporate attribute data via a uniform map-based interface, thereby enabling them to carry out data quality control, spatial analysis, and mapping. Initially GIS technology has been implemented with applications linking to the corporate well database, to prospect and lead databases for portfolio management, and to seismic 2-D and 3-D location and interpretation data. Particularly for personnel new to the PDO environment, GIS provides a tool for users to become quickly familiar with the available corporate data and for managers to analyse data in a way not previously possible.
The Challenge of Interpreting 3-D Seismic in Shaybah Field, Saudi Arabia
Authors: Alfara Mohammed N. , Nebrija Edgardo L. , Ferguson Michael D.
Published: October 2021

The giant Shaybah field, situated in the northeastern Rub’ Al-Khali Desert in Saudi Arabia, was discovered in 1968. 2-D seismic and well control were used at the time to delineate the field. A 3-D seismic program was launched in 1993 to develop a detailed geological picture of the field. Over 120 million seismic traces, covering an area of about 1,100 square kilometers, were acquired in flat sabkhas and high sand dunes. The dunes, exceeding 200 meters in height in places, posed a severe statics correction problem. Up to 200 milliseconds of time correction was sometimes applied to the seismic traces in order to compensate for sand-related statics. Also, as verified by vertical seismic profiles, the reservoir level was severely obscured by strong multiples.

In addition to complex topography and multiples, the 3-D structural seismic interpretation had to overcome two further problems. First, the lithology of the gas-capped Shu’aiba reservoir consists predominantly of carbonates which are sealed by a denser, compacted shale. The decrease in density and increase in velocity, at the top of the Shu’aiba reservoir, result in a weak reflection. Second, the top of the Shu’aiba reservoir undulates as a result of rudist build-ups and therefore is not conformable with its base. For these reasons, the top of the Shu’aiba reservoir cannot be mapped as a “phantom” of the much better reflection from the base of the reservoir.

To resolve the uncertainties described above, borehole seismic measurements (specifically offset and zero-offset vertical seismic profiles in vertical wells) were incorporated. These additional measurements provided the required calibration of the seismic, and hence the validation of the structural interpretation. These borehole surveys continue to serve as a reference for on-going efforts to further improve the data quality using more advanced processing techniques.
Production and Geological Implications of the Natih 9C3D Seismic Survey
Authors: Hitchings Victor H. , Potters Hans
Published: October 2021

The Natih Formation in the Natih field is a heterogeneously fractured reservoir being developed by gas/oil gravity drainage. An understanding of the degree and orientation of the fracturing is essential for the optimum development of the reservoir. In order to better understand the fracturing in the reservoir, conventional 3-D (compressional) and limited 9C3D (nine-component, three-dimensional) seismic surveys were made of the Natih field. A revised fault/fracture model was developed from the conventional 3-D survey results in which ‘domains’ of similar fault/fracture character have been defined. Comparison with well-production data indicates that the domains associated with strike-slip or rotational movements (interpreted as being more fractured than adjacent areas) are zones of significantly higher productivity. The 9C3D seismic survey results also show areas or ‘domains’ of variable shear-wave time splitting. A comparison of the fault/fracture domains with the shear-wave time-splitting domains shows a close relationship in which areas of highest shear-wave time splitting coincide with those in which fracturing is most intense. The integration of fault/fracture modeling, well-production characteristics and the 9C3D survey results indicate the potential of the latter as a field-development tool in terms of optimizing well locations, well planning and reservoir management decision making.
Exploration for a Frontier Salt Basin in Southwest Oman
Authors: Blood Mark F.
Published: October 2021

An undrilled Infracambrian-lower Paleozoic salt basin is interpreted as being present in the Dhofar area of southwest Oman. A re-evaluation of the existing seismic and gravity data indicated that the basin is located immediately north of a major NE-orientated basement feature known as the Ghudun-Khasfah High. The basin is centered in the southern part of the Al Hashman Block 36 and the northern part of Mudayy Block 38, both operated by Phillips. Studies conducted by Phillips suggest that the basin has a similar structural history and pre-Silurian stratigraphy to the known salt basins of Oman. New stratigraphically deeper Paleozoic and Infracambrian exploration plays that are proven in the other Oman salt basins are proposed for this undrilled basin. The new plays rely on an unproven Infracambrian Huqf source. Source and reservoir degradation through widespread post-Huqf deformation is possible, but structural modeling and seismic facies analysis, together with the detection of significant micro-seepage anomalies, suggest otherwise. In addition, the identification and gravity modeling of what appear to be salt features on seismic lines support the presence of Lower Cambrian salt swells and piercement structures. The salt features are believed to be age equivalent to the Ara salt section of the upper Huqf Supergroup present in the other salt basins. Phillips has named this potential salt basin the Ghudun Salt Basin.
Upper Burgan Reservoir Description, Northern Kuwait: Impact on Reservoir Development
Authors: Al-Eidan Ahmad J. , Wethington W. Barry , Davies Roger B.
Published: October 2021

The giant Albian upper Burgan reservoir in northern Kuwait is a major productive interval in both the Raudhatain and Sabiriyah fields. It is planned to increase production from the upper Burgan by over 300 percent through the application of field-wide waterflood. Phase 1 of seawater injection was started in 1999. A comprehensive geological study of the upper Burgan has included reviews of all core data, biostratigraphic information, and geochemical and petrographic analyses. The results indicate that the reservoir sandstones were laid down in a complex series of paralic environments ranging from shallow-marine to valley-fill channels. The resultant layering scheme was integrated with all available dynamic data to best define the reservoir architecture and flow units, and to construct a fine-grid 3-D geological model. The geological analysis has had a significant impact on reservoir development, influencing waterflood strategy, pattern orientation and expected performance. In the Raudhatain field, where reservoir connectivity is relatively high, a peripheral waterflood will be implemented (at least initially), whereas the complex structure and stratigraphy of the Sabiriyah field dictate a pattern flood.
Qasim Formation: Ordovician Storm- and Tide-Dominated Shallow-Marine Siliciclastic Sequences, Central Saudi Arabia
Authors: Senalp Muhittin , Al-Duaiji Abdulaziz A.
Published: October 2021

The Middle to Upper Ordovician Qasim Formation is well exposed in the Qasim region of central Saudi Arabia and is recognized from many wells to the north and east. It consists of the Hanadir, Kahfah, Ra’an, and Quwarah members that are arranged in two coarsening-upward progradational sequences that have a total thickness of about 200 m in outcrops. Two sections were measured in each sequence.

The lower sequence is a storm-dominated, shallow-marine depositional system composed of the late Llanvirn to middle Caradoc Hanadir and Kahfah. At least five progradational beach parasequences were identified. The Hanadir overlies deltaic deposits of the upper Saq Formation and marks a major marine transgression onto Gondwana. It is composed of laminated fissile shale formed in an offshore marine environment together with siltstone laminae that indicate periodic influxes of low-density turbidity currents. The overlying Kahfah is composed of shale and sandstone.

The upper progradational sequence consists of the middle Caradoc to middle Ashgill Ra’an and Quwarah members. The Ra’an is a succession of homogeneous fissile shale and minor siltstone laminae formed in an offshore marine environment following a major transgression onto the Kahfah. The overlying Quwarah consists of sandstone and minor amounts of siltstone and shale in its lower parts, and a thickly bedded sandstone facies above. The diagnostic sedimentary structures in the Quwarah are large-scale lens-shaped tidal sand waves composed of sigmoidal bundles deposited in a mesotidal setting of barrier bars, tidal channels, ebb-dominated deltas and lagoons.

In the subsurface, the Formation thickens northeastward (basinward) to over 4,000 ft (1,220 m). In the same direction, the sand-dominated Kahfah and Quwarah gradually become shale-dominated, small-scale bed forms are more abundant, and identification of members based on lithofacies is more difficult.

After deposition of the Quwarah, present-day Saudi Arabia was affected by a Late Ordovician (late Ashgill) glaciation. The Qasim and older formations are deeply incised by glacial channels at the base of the Zarqa and Sarah formations. Basinward, the glacial unconformities (or their submarine erosion surface equivalents) become less significant and a thick succession of the Formation is preserved.
Tectonic Evolution of the Eastern Mediterranean Basin and its Significance for the Hydrocarbon Prospectivity of the Nile Delta Deepwater Area
Authors: Ahmed AbdelAal , Ahmed El Barkooky , Marc Gerrits , Hans-Jürg Meyer , Marcus Schwander , Hala Zaki
Published: October 2021

The deepwater area of the Nile Delta is within the eastern Mediterranean basin on the Nile Delta Cone between the Herodotus abyssal plain to the west and the Levant basin to the east. The complex evolution and interaction of the African, Eurasian and Arabian plates have shaped the Late Miocene to Recent Nile Cone and its substratum. The tectono-stratigraphic framework is controlled by deep-seated basement structures with distinct gravity and magnetic expressions, and by the interaction of the NW-trending Misfaq-Bardawil (Temsah) and NE-trending Qattara-Eratosthenes (Rosetta) fault zones. In addition, significant salt-induced deformation of a Messinian evaporitic sequence up to 4,000 m thick has occurred, together with large-scale rotational block movement. The deformational pattern is largely the result of multiphase tectonic movements along pre-existing basement faults on the continental margin of the Neo-Tethys ocean.

The Nile Cone consists of late Paleogene to Late Miocene sediments that pre-date the Messinian evaporites, and Pliocene-Pleistocene sequences. In the east, the pre-salt deposits (as much as 3,000 m thick) are primarily deepwater sediments with local condensed sequences over syndepositional intrabasinal highs. Shale occurs westward across the Rosetta trend. The Messinian evaporitic sequence exhibits three distinct seismic facies suggesting cyclic deposition with the occurrence of interbedded anhydrite, salt and clastic sequences and pure halite deposition. During the Messinian salinity crisis, large-scale canyons were excavated that resulted in multiphase cut-and-fill clastic systems. The Pliocene-Pleistocene sequences were deposited in a slope to basin-floor setting.

Exploration targets are the Pliocene-Pleistocene deepwater channel and basin-floor turbidite sands in a variety of structural settings. Water depths range from 800 to 2,800 m. The Upper Miocene sequence offers additional exploration objectives in the form of fluvial and/or turbidite sands. The focus of pre-salt exploration is the delineation of distal turbidities within the Serravallian to Tortonian sequence and the identification of new reservoir sequences deposited on pre-existing intrabasinal highs. Hydrocarbon charge has yet to be proven by drilling, but seismic amplitude anomalies and the occurrence of natural surface slicks suggest both gas and liquid charges from pre-salt source rocks through faults and salt-withdrawal windows.
Impact of 3-D Seismic Surveys on Development of the Minagish Oolite Reservoirs, Minagish and Umm Gudair Fields, Kuwait
Authors: Al-Ateeqi Alaa M. , Foster Dave G.
Published: October 2021

The Kuwait Oil Company acquired 2-D and 3-D seismic data from 1996 to 1998 in a program that is believed to be one of the largest undertaken in the region. The 2-D surveys were used to define possible prospective areas, whereas the 3-D surveys have helped to increase the productivity of the existing oil fields. The 3-D surveys acquired over the Minagish and Umm Gudair fields in onshore West Kuwait were two of the first to be completed. The data is of excellent quality with high signal-to-noise ratios and stable phase and amplitude characteristics. The rapid 3-D interpretation was made possible by using state-of-the-art interpretation and visualization software, and has already had a considerable impact on the perception of the subsurface geology of the mainly Cretaceous reservoirs. In both fields, fault patterns were reliably defined for the first time and accurate depth maps resulted from careful attention to the near-surface static corrections, depth conversions and interpretations made from the superior 3-D imaging. These factors have enabled the accurate placement of wells. Acoustic impedance data is being used to define reservoir and aquifer porosity distribution. The impact of the 3-D surveys has enabled optimum development decisions to be made, thus helping to maximize Kuwait’s valuable oil resources.
Stratigraphy, micropaleontology, and paleoecology of the Miocene Dam Formation, Qatar
Authors: Al-Saad Hamad , Ibrahim Mohamed I.
Published: October 2021

The Miocene carbonate Dam Formation is well exposed in the Jebel Al-Nakhash area of southern Qatar. Three sections were measured in a detailed investigation of the Formation’s stratigraphy, micropaleontology, and paleoecology. This biostratigraphic and paleoecologic study was supported by the analysis of microlithofacies and foraminiferal assemblages. Microfossils are predominantly benthic foraminifera represented by 38 species, many of which are milioline and one is a larger form. A Borelis melo melo Local Range Zone of Early Miocene (Burdigalian) age was recognized. The nature and distribution of the benthic foraminiferal assemblage, in association with lithofacies evidence, indicated a general shoaling-upward trend.

The Dam Formation was stratigraphically subdivided into two new formal members. The basal Al-Kharrara Member is made up of limestone, marl, and claystone, and the overlying Al-Nakhash Member is a cyclic assemblage of carbonate, evaporite, and algal stromatolite facies. The lithofacies are grouped into four major types of which limestone, subdivided into six subfacies, is dominant. The Al-Kharrara was interpreted as having been deposited in warm (25°–30°C), clear, shallow waters of the inner neritic zone (0–35 m) that had an elevated salinity (35‰–50‰) and a vegetated substrate. The Al-Nakhash probably formed in an oscillating, very shallow-marine environment (0–10 m deep, including tidal flats), under warm climatic conditions that eventually led to the accumulation of evaporites and algal stromatolites.
Quaternary Development of the United Arab Emirates Coast: New Evidence from Marawah Island, Abu Dhabi
Authors: Evans Graham , Kirkham Anthony , Carter Robert A.
Published: October 2021

Marawah is one of a chain of barrier islands off the coast of Abu Dhabi that separates the Khor Al Bazm lagoon from the open waters of the Arabian Gulf. The island consists of several rocky cores of Pleistocene limestone linked by areas of unconsolidated Holocene carbonates. It has the most complete Quaternary outcrop sequence in the region and the lowest exposed unit, a coralline limestone, had not been recorded previously. The Pleistocene deposits accumulated partly in a shallow-marine environment and partly under eolian conditions. The Marawah sections have revealed new data about the history of the southern Gulf in the late Pleistocene, a time interval of which little was known. The survey has shown that there were periods when sea level was close to present-day levels and other times when it was approximately 4 to 5 m higher than today. A phase of deflation and the development of a field of eolian sand dunes separated these two sea-level highstands. The unconsolidated sediments have accumulated around the Pleistocene rock cores since about 4,500 years BP to give the island its present form. Accumulation occurred because of wave action driven by the northwesterly ‘Shamal’ winds during periods of slightly falling or almost stationary sea level.
Chronostratigraphy, palynofacies, source-rock potential, and organic thermal maturity of Jurassic rocks from Qatar
Authors: Ibrahim Mohamed I. A. , Al-Saad Hamad , Kholeif Suzan E.
Published: October 2021

Strontium isotope, palynological, and total organic carbon (TOC) analyses were made on core samples from the Izhara, Araej, and Hanifa formations of three wells in onshore Qatar. Eleven samples were analyzed for their 87Sr/86Sr ratios. The results gave a chronostratigraphic range of Early Jurassic (Hettangian) to Late Jurassic (Oxfordian), with an overall age range of 202.4 Ma to 157.8 Ma. Maximum flooding surfaces MFS J10 to MFS J50 occur in the Izhara, Araej, and Hanifa formations.

The organic matter in the carbonate sediments of the Izhara, Araej, and Hanifa formations was almost exclusively of marine algal origin dominated by marine microplankton. Organic matter obtained from the Izhara Formation was mature to over-mature kerogen type-III to IV, gas-prone to inert material (mean TOC 0.31%). In the Araej Formation, mature oil-prone and gas-prone kerogen type-II and type-III organic matter occurred in both the lower and upper Araej members (TOC 0.13-0.69%). The stylolitic limestone of the Uwainat member of the Araej Formation has poor potential as a source rock for petroleum (TOC 0.03-0.13%), but is considered to be the main reservoir rock of the Middle Jurassic in Qatar. Mature, highly oil-prone organic matter (type-I and type-II kerogen) was present in black limestone of the Hanifa Formation (mean TOC 0.60%; maximum 0.93%). The limestone is considered to be the most likely petroleum source rock for the underlying and overlying limestone reservoirs of the Uwainat member of the Araej Formation (Bathonian) and the Arab-D member of the Arab Formation (Kimmeridgian) units, respectively.
Paleoecological and paleobiogeographical significance of the rudist Macgillavryia chubbii sp. n. in the Campanian of Oman
Authors: Philip Jean M.
Published: October 2021

Excellently preserved specimens of the large rudist Macgillavryia have been described for the first time from the Campanian Samhan Formation in the vicinity of Filim and Hayy on the eastern side of the Haushi-Huqf massif in Oman. A new species, M. chubbii, was named and found to be equivalent to other species of Macgillavryia from the Caribbean domain. The exceptionally well-preserved holotype with its articulated valves allowed the reconstruction of the functional morphology of the mantle. The indications are that the left valve of M. chubbii covered only a small part of the commissural area, leaving a large part of the mantle of the right valve directly exposed to sea water and sunlight. As a result, M. chubbii has been proposed as a potential candidate for an association with zooxanthellae. Macgillavryia is a typical epifaunal rudist that probably lived in very shallow, clear seas. The shell was not buried during its lifetime but was exposed to epibionts and bioeroders. The excellent exposures allowed the reconstruction of relationships between Macgillavryia and other biotic or abiotic components. They formed a densely packed association with spaces filled by a very coarse bioclastic material. The superpositioning of two or more layers with superstratal growth fabrics created individual rudist banks more than 1 m thick covering several hundred square meters. Paleobiogeographic reconstructions have connected M. chubbii in Arabia with Macgillavryia in the Caribbean by eastward dispersion through the Pacific region.
Reservoir rock classification, Arab-D reservoir, Ghawar field, Saudi Arabia
Authors: Cantrell Dave L. , Hagerty Royal M.
Published: October 2021

An integrated petrographic and petrophysical study of Arab-D carbonates in Ghawar field has provided a new reservoir rock classification. This classification provides a simple but practical method of dividing the complex carbonate rocks of the Arab-D into meaningful reservoir rock types. Each rock type has a distinct pore network as defined by porosity-permeability relationships and capillarity expressed as pore-size distributions and J-function curves. The classification divides the Arab-D carbonates into seven limestone and four dolomite rock types. The amount of matrix (lime mud) and the pore types are the primary controlling parameters for the limestones. The dolomites are divided according to their crystal texture.

The seven limestone reservoir rock types are based on the values of five petrographic parameters: (1) the amount of cement, (2) the amount of matrix (lime mud), (3) the grain sorting, (4) the dominant pore type, and (5) the size of the largest molds. The amount of matrix is the most important of these five parameters. In general terms, six of these seven types fall into two broad families, A and B, each of which can then be subdivided into three members (Types I, II, and III) according to their matrix content. The first family, A, is a fairly coarse-grained, poorly sorted rock with relatively large molds. The second family, B, is a generally fine to medium-grained, well sorted rock with few or small molds. The seventh rock type contains more than 10 percent cement which modifies the pore size distribution enough to warrant a separate reservoir rock type. Each of the reservoir rock types exhibits a distinctive pore-size distribution and, in turn, Leverett J-function or capillarity. The seven types are also characterized by distinctive porosity-permeability relationships.

The four dolomite reservoir rock types are classified according to their dolomite crystal texture, although stratigraphic position and porosity can also be effective in their classification. The four textures are: fabric preserving (Vfp), sucrosic (Vs), intermediate (Vi) and mosaic (Vm). The Vfp dolomite is only found in Zone 1 of the Arab-D where it is the major dolomite type. Vs dolomite occurs in dolomites with more than 12 percent porosity, Vm less than 5 percent and Vi between 5 and 12 percent. Vfp dolomites have pore systems similar to their precursor limestone but the pore systems of the other dolomite types are unique.

A significant finding of this evaluation is that the micropore system in all major limestone rock types in Zones 1 and 2 (upper Arab-D) is consistently an order of magnitude larger than for the same rock types in Zones 3 and 4 (lower Arab-D). The increase in size is believed to be a result of increased leaching in the upper Arab-D. This difference suggests that rocks of similar type from the upper and lower Arab-D will behave differently in terms of their fluid flow and saturation characteristics, and will have different ultimate recoveries.
The Sahmah Formation of Oman: exploration implications for the Rub’ Al-Khali Basin
Authors: Svendsen Nick B.
Published: October 2021

The Sahmah Formation (Safiq Group, Haima Supergroup) of Oman is divided into a lower ‘Shale Member’ (or ‘Sahmah Shale’), and an upper ‘Sandy Member’. The Shale Member was deposited in a deep-marine environment, and the Sandy Member in a marginal marine setting. The formation is greater than 500 meters thick in the Burkanah-1 exploration well, located in south Oman along the eastern edge of the Rub’ Al-Khali Basin. In many areas in Oman, the formation is absent due to erosion by the ‘Hercynian’ unconformity. The age of the Sahmah is generally interpreted as Early Silurian Llandovery; however, recent biostratigraphic studies suggest that it may range in age from latest Ordovician Ashgill to Llandovery. The basal Sahmah Shale (3–10 meters thick) is an excellent source rock, as confirmed by its correlation to the ‘B’ oil in the overlying Permian Gharif Formation in the Sahmah field in central Interior Oman.

This study combined new and previously acquired geological data from 16 wells in Oman, and includes source rock analytical data. A basin model was used to assess the maturation history of the Sahmah Shale, and the hydrocarbon potential of two associated petroleum systems. The first system occurs along the ‘Hercynian’ erosional edge of the Sahmah source rock. The migration pathway involves vertical charging of the overlying Upper Carboniferous-Lower Permian Al Khlata Formation or/and the Permian Gharif Formation. This area constitutes the Sahmah Shale:Gharif Formation(!) Petroleum System. The second Petroleum System, the Sahmah Shale:Hasirah Formation(?), applies to regions where the Sahmah is thick, and intra-Sahmah shales act as a seal. In these regions, if the shale is mature and the pre-Sahmah section is porous, then down charging provides the migration pathway to the trap.
Impact of basin evolution, depositional environment, pore water evolution and diagenesis on reservoir-quality of Lower Paleozoic Haima Supergroup sandstones, Sultanate of Oman
Authors: Ramseyer Karl , Amthor Joachim E. , Spötl Christoph , Terken Jos M.J. , Matter Albert , Hove Marietta Vroon-ten , Borgomano Jean R.F.
Published: October 2021

Sandstones of the Early Paleozoic Miqrat Formation and Barik Sandstone Member (Haima Supergroup) are the most prolific gas/condensate containing units in the northern part of the Interior Oman Sedimentary Basin (IOSB). The reservoir-quality of these sandstones, buried to depths exceeding 5 km, is critically related to the depositional environment, burial-related diagenetic reactions, the timing of liquid hydrocarbon charge and the replacement of liquid hydrocarbon by gas/condensate.

The depositional environment of the sandstones controls the net-sand distribution which results in poorer reservoir properties northwards parallel to the axis of the Ghaba Salt Basin. The sandy delta deposits of the Barik Sandstone Member have a complex diagenetic history, with early dolomite cementation, followed by compaction, chlorite formation, hydrocarbon charge, quartz and anhydrite precipitation and the formation of pore-filling and pore-lining bitumen. In the Miqrat Formation sandstone, which is comprised of inland sabkha deposits, similar authigenic minerals occur, but with higher abundances of dolomite and anhydrite, and less quartz cement. The deduced pore water evolution from deposition to recent, in both the Miqrat Formation and the Barik Sandstone Member, reflects an early addition of saline continental waters and hydrocarbon-burial related mineral reactions with the likely influx of lower-saline waters during the obduction of the Oman Mountains.

Four structural provinces are recognized in the IOSB based on regional differences in the subsidence/uplift history: the Eastern Flank, the Ghaba and Fahud Salt Basins and the Mabrouk-Makarem High. In the Fahud Salt Basin, biodegradation of an early oil charge during Late Paleozoic uplift resulted in reservoir-quality degradation by bitumen clogging of the pore space. On the Eastern Flank and the Mabrouk-Makarem High, however, the early oil bypassed the area. In contrast, post-Carboniferous liquid hydrocarbons were trapped in the Mabrouk-Makarem High, whereas on the Eastern Flank surface water infiltration and loss of hydrocarbons or biodegradation to pore occluding bitumen occurred. In the Ghaba Salt Basin, post-Carboniferous hydrocarbon charge induced a redox reaction to form porosity/permeability preserving chlorite in the reservoirs. The liquid hydrocarbons were replaced since the obduction of the Oman Mountains by gas/condensate which prevented the deep parts (>5,000 m) of the Ghaba Salt Basin from pore occluding pyrobitumen and thus deterioration of the reservoir quality.
Seismic forward model of a Natih Formation outcrop: the Adam Foothills Transect (northern Oman)
Authors: Anne M.Schwab , Peter W.Homewood , Frans S.P.van Buchem , Philippe Razin
Published: October 2021

The platform carbonates of the Natih Formation (Albian-Turonian) are hydrocarbon reservoirs throughout the Middle East. This study uses a high-resolution sequence stratigraphic model built from the Natih outcrops of the Adam Foothills Transect, in northern Oman, as the basis for the construction of synthetic seismic sections along the Natih outcrops. The model covers the seaward progression from a proximal carbonate platform to a distal intrashelf basin. Three third-order depositional sequences had been identified and correlated across the outcrops, and facies were mini-core plugged for petrophysical data measurement, which were then used to construct an impedance model from the stratigraphic model. This impedance model was used to construct synthetic seismic sections with a zero phase Ricker wavelet at varying peak frequencies (80 Hz, 60 Hz and 40 Hz). The high-frequency synthetic seismic identified seismic characteristics of specific depositional environments, notably the organic-rich intrashelf basin, the platform margin and the platform interior. These seismic characteristics were very subtle on the lower frequency data, but could nonetheless be identified. A seismic line passing through a nearly analogous setting in the subsurface Natih was used to try and identify the characteristics observed on the synthetic seismic data. Many of the synthetically-produced characteristics were found on the industry seismic, which shows that this method is a good way of using the detail of the outcrop to help with predictions on the lower frequency/resolution seismic.
Correlation of the Lower Permian surface Saiwan Formation and subsurface Haushi limestone, Central Oman
Authors: Angiolini Lucia , Stephenson Michael H. , Leven Ernst J.
Published: October 2021

The palaeontology of the Saiwan Formation (Lower Permian) of the Al-Huqf outcrop area, Central Oman, has been the subject of significant study, but that of approximately equivalent beds in the subsurface (the Haushi limestone and ‘basal sandstones’ of the lower Gharif member) has been unknown until now. This has meant that the precise relationship between the surface and subsurface units has been poorly understood. A new subsurface brachiopod study has allowed a fourfold biozonation that correlates the surface Saiwan Formation with the subsurface Haushi limestone, implying that previous direct correlation of the Saiwan Formation with the lower Gharif member is not correct. Overall the brachiopod fauna of the subsurface is of lower diversity than that of the outcropping Saiwan Formation, suggesting deposition in quieter and deeper marine settings. The occurrence of a fusulinid assemblage with Pseudofusulina ex gr. karapetovi karapetovi Leven, the first such record in Gondwana, suggests a Sakmarian age for the Haushi limestone, and brachiopod data supports this determination. Subsurface Haushi limestone palynological assemblages, though diverse, are poorly preserved, and no palynomorphs have been recovered from equivalent surface outcrops. However, the distribution of autochthonous algal spores in three of the subsurface Haushi limestone sections suggest a local biozonation that is consistent with that indicated by brachiopods, while the terrestrially-sourced palynomorphs in the subsurface Haushi limestone sections indicate an OSPZ3c age. Surprisingly the sections contain no palynomorphs of unequivoval marine origin. Fusulinids indicate that a Sakmarian age for OSPZ3c is more likely than the Artinskian age suggested by previous palynological studies. The terrestrially sourced palynomorphs also suggest correlation of the carbonates of the Haushi limestone with the highest part of the clastic lower Gharif Member in South Oman, above the Ulanisphaeridium omanensis Biozone or Maximum Flooding Shale in that area. Using the new biozonation, the distribution of facies has been mapped for three time slices. This reveals an increase in carbonate deposition during the Sakmarian due to distancing and deepening of the terrigenous source, coupled with climatic warming, culminating with a regressive trend at the end of the cycle. A progressive increase in carbonate deposition is recorded westward into the basin.
Late Cretaceous to Paleogene post-obduction extension and subsequent Neogene compression in the Oman Mountains
Authors: Fournier Marc , Lepvrier Claude , Razin Philippe , Jolivet Laurent
Published: October 2021

After the obduction of the Semail ophiolitic nappe onto the Arabian Platform in the Late Cretaceous, north Oman underwent several phases of extension before being affected by compression in the framework of the Arabia-Eurasia convergence. A tectonic survey, based on structural analysis of fault-slip data in the post-nappe units of the Oman Mountains, allowed us to identify major events of the Late Cretaceous and Cenozoic tectonic history of northern Oman. An early ENE-WSW extensional phase is indicated by synsedimentary normal faults in the Upper Cretaceous to lower Eocene formations. This extensional phase, which immediately followed ductile extension and exhumation of high-pressure rocks in the Saih Hatat region of the Oman Mountains, is associated with large-scale normal faulting in the northeast Oman margin and the development of the Abat Basin. A second extensional phase, recorded in lower Oligocene formations and only documented by minor structures, is characterized by NNE (N20°E) and NW (N150°E) oriented extensions. It is interpreted as the far-field effect of the Oligocene-Miocene rifting in the Gulf of Aden. A late E-W to NE-SW directed compressional phase started in the late Oligocene or early Miocene, shortly after the collision in the Zagros Mountains. It is attested by folding, and strike-slip and reverse faulting in the Cenozoic series. The direction of compression changed from ENE-WSW in the Early Miocene to almost N-S in the Pliocene.
Megaseismic section across the northeastern slope of the Arabian Plate, Iraq
Authors: Mohammed Sabah A.G
Published: October 2021

A composite seismic image (Megaseismic Line 7) was constructed across Iraq using 16 pre-existing seismic lines that were recorded between 1975 and 1983. The image is the first of 15 megaseismic lines that will eventually form a rectilinear grid that covers Iraq. It is oriented in a SW-NE direction, and extends approximately 500 kilometers from the Iraq-Saudi Arabia border to the Iraq-Iran border. The seismic lines were recorded using a 48-channel system with either a vibroseis or dynamite source. The maximum offset varies from 2,400 to 5,000 meters. The seismic data was reprocessed using a common datum of 300 meters above sea level. Data quality is good where the source was dynamite and the terrain consists of gravel and sand surfaces; it is poor where vibroseis was used or/and the outcrops were carbonates. The final stacked section and Hilbert attributes (reflection amplitude and instantaneous phase) were displayed at different scales to determine the best perspective for interpretation. A total of 14 reflections, corresponding to Miocene to Permian horizons, were identified using synthetic seismograms from five wells. The horizons generally dip towards the northeast, except at the location of the Tel Ghazal oil field where syndepositional growth is inferred. Various seismic stratigraphic geometries, such as sigmoidal features, onlap, toplap and downlap, were identified and used to define disconformities and angular unconformities.

The oldest two horizons that could be picked are from the tops of the Triassic Kurra Chine and Permian Chia Zairi formations. Below the oldest Permian reflection, the middle Carboniferous “Hercynian unconformity” was tentatively picked. The Paleozoic pre-Permian succession is not adequately imaged in the seismic data, nor is the crystalline basement seen. The seismic interpretation was compared to the profiles of the Bouguer gravity anomaly and the total magnetic field, and good correlations were established. The regional line helped identify several previously unknown structural features including the Ma’aniya Depression in the Western Desert, and two anticlinal structures: the first being within that depression and the second directly to the southwest of Tel Ghazal oil field.
Fault growth and coalescence: insights from numerical modelling and sandbox experiments
Authors: Filbrandt Jacek B. , Richard Pascal D. , Franssen Raymond
Published: October 2021

Displacement of strata varies along the strike of faults. This has important implications for the hydrocarbon industry, since for example this affects the occurrence and distribution of fractures along faults in a reservoir and can influence the sealing capacity of faults. As faults grow, neighbouring faults will interact with each other and eventually connect or coalesce. Geometrical fault growth models for coalescence are used to explain a large part of the observed spread of one order of magnitude in Length and Maximum Throw in natural examples of fault populations. Numerical modelling indicates that coalesced (merged) faults tend to return to their steady state growth evolution by accumulating displacement more rapidly than increasing in length, if no further coalescence occurs. Therefore, repetitive coalescence leaves faults “under-displaced” and results in a considerable spread in Length and Maximum Throw. To confirm and support these observations, a series of sandbox experiments was performed, which help improve our understanding of fault growth processes. The fault geometries observed in these models reflect geometries in natural examples, for example in the Natih Formation of Al Jabal al Akhdar in Oman. With increasing strain, repetitive coalescence takes place at all scales. After linkage, a new, coalesced fault behaves as a single, linked segment and accumulates more displacement than increasing length during an increment of strain. The slope of the best fit line of Length vs. Maximum Throw data for the fault population, in double logarithmic space, steepens with increasing strain and stabilises at about one.
Methanogenesis during Shu’aiba diagenesis: examples from Al Shaheen Field, Block 5, offshore Qatar
Authors: Raven Madeleine J. , Dickson Tony
Published: October 2021

Evidence has been found for the involvement of bacterial methanogenic processes in the diagenesis of late Early Aptian Shu’aiba Formation sedimentary rocks from Block 5, offshore Qatar. This is in the form of δ13C values significantly higher than the presumed late Early Aptian marine signal. High δ13C values were recorded in early-formed inclusion-rich calcite that represents neomorphosed aragonite/marine cement (+6.6‰) and the latest precipitated blocky non-ferroan calcite cement (+8.9‰). Oxygen-isotope data suggest that the later methanogenic episode occurred during burial. In bulk rock samples from another well, δ13C values of +6.5 to +11.5‰ were determined from a 10 ft thick zone located 4 ft below the top of the Shu’aiba. In other wells for which data were available the equivalent interval of the Shu’aiba was characterised by expected marine δ13C values. Finally, δ13C values up to +9.1‰ were recorded in a localised area of dolomite replacement immediately beneath the Top Shu’aiba surface, which can be dated to after the onset of Nahr Umr Formation deposition. These are the first reported examples of methanogenic reactions affecting the Shu’aiba Formation and provide new insight into the diagenesis of this formation, which is often assumed to be dominated by meteoric processes. The evidence presented for the resetting of the carbon-isotope composition of the bulk rock has implications for the application of carbon-isotope stratigraphy to the Shu’aiba Formation.