bluuebunny/crossref_metadata_2025_split huggingface dataset:
Petroleum system analysis of the Mishrif reservoir in the Ratawi, Zubair, North and South Rumaila oil fields, southern Iraq
Authors: Al-Ameri Thamer K. , Al-Khafaji Amer Jassim , Zumberge John 
Published: October 2021

ABSTRACT
Five oil samples reservoired in the Cretaceous Mishrif Formation from the Ratawi, Zubair, Rumaila North and Rumaila South fields have been analysed using Gas Chromatography – Mass Spectroscopy (GC-MS). In addition, fifteen core samples from the Mishrif Formation and 81 core samples from the Lower Cretaceous and Upper Jurassic have been subjected to source rock analysis and palynological and petrographic description. These observations have been integrated with electric wireline log response. The reservoirs of the Mishrif Formation show measured porosities up to 28% and the oils are interpreted as being sourced from: (1) Type II carbonate rocks interbedded with shales and deposited in a reducing marine environment with low salinity based on biomarkers and isotopic analysis; (2) Upper Jurassic to Lower Cretaceous age based on sterane ratios, analysis of isoprenoids and isotopes, and biomarkers, and (3) Thermally mature source rocks, based on the biomarker analysis.
The geochemical analysis suggests that the Mishrif oils may have been sourced from the Upper Jurassic Najma or Sargelu formations or the Lower Cretaceous Sulaiy Formation. Visual kerogen assessment and source rock analysis show the Sulaiy Formation to be a good quality source rock with high total organic carbon (up to 8 wt% TOC) and rich in amorphogen. The Lower Cretaceous source rocks were deposited in a suboxic-anoxic basin and show good hydrogen indices. They are buried at depths in excess of 5,000 m and are likely to have charged Mishrif reservoirs during the Miocene. The migration from the source rock is likely to be largely vertical and possibly along faults before reaching the vuggy, highly permeable reservoirs of the Mishrif Formation. Structural traps in the Mishrif Formation reservoir are likely to have formed in the Late Cretaceous.
Calcimicrobe tubules in uppermost Jurassic Arab-A carbonates of Saudi Arabia
Authors: Wyn ap Gwilym Hughes G. 
Published: October 2021

ABSTRACT
Uppermost Jurassic carbonates from the Arab-A Member of the Arab Formation in the subsurface of eastern Saudi Arabia reveal hollow, intertwined, locally bifurcating, microtubules consisting of a chain-like, uniserial series of inaperturate, stacked, concavo-convex crescentic chambers tentatively assigned to Gahkumella sp. Previously confined to the Oxfordian of North America, and possibly the Lower Cretaceous of Oman, this is believed to be the first observation of such forms in uppermost Jurassic carbonates. The carbonates consist of a lower, transgressive, ooid-foraminiferal lithofacies and an upper, regressive, stromatolite-ostracod lithofacies of which the microtubules are developed in the latter. Comparison of these structures with fossil and Recent cyanobacterial microborings and Oxfordian calcimicrobial tube-like forms suggests probable cyanobacterial affinity. Despite their very limited stratigraphic extent, they may contribute to improving mouldic microporosity of the Arab-A carbonate reservoir.
Calibrating Mid-Permian to Early Triassic Khuff sequences with orbital clocks
Authors: Al-Husseini Moujahed I. , Matthews Robley K. 
Published: October 2021

ABSTRACTThe Middle East Geologic Time Scale (ME GTS) seeks to document and age-calibrate Arabian Plate transgressive-regressive (T-R) depositional sequences using: (1) Geological Time Scale of the International Commission on Stratigraphy (GTS), and (2) Arabian Orbital Stratigraphy time scale (AROS). AROS is based on an orbital-forcing glacio-eustatic model that offers three orbital clocks to date T-R sequences: (1) Stratons @ ca. 405 Ky; (2) Dozons @ ca. 4.86 My (12 stratons); and Orbitons @ ca. 14.58 My (36 stratons, three dozons). The Earth today is in Orbiton 0, which started ca. 1.5 Ma (SB 0); the ages of lower boundaries of orbitons can be estimated with the formula SB n = n × 14.58 + 1.5 Ma. This scheme was used to calibrate the Arabian Plate’s Mid-Permian to Early Triassic Khuff sequences, which contain one of the largest gas-bearing carbonate reservoirs in the World.The Khuff and equivalent formations have been interpreted by several authors in terms of six long-period sequences in outcrop belts and subsurface sections (Khuff sequences KS6 to KS1 in ascending order). Their type sections are briefly reviewed with emphasis on their boundaries, higher-order architecture and stage assignments. The age calibration starts at the basal Khuff Sequence Boundary (Khuff SB, Sub-Khuff Unconformity) defined in a type section in Al Huqf outcrop in Oman. Above the Khuff SB (ca. 268.9 Ma) the type sections of the oldest Khuff sequences KS6 (ca. 268.9–264.0 Ma) and KS5 (ca. 264.0–259.1 Ma) are defined in Oman and interpreted to each consist of twelve subsequences (stratons) with the predicted architecture of two consecutive dozons. By biostratigraphy they span the Mid-Permian (Guadalupian Epoch), Wordian and Capitanian stages.Type-Sequence KS4 (ca. 259.1–254.2 Ma) is defined in Iran and corresponds to the Wuchiapingian Stage. The Iranian type-Khuff Sequence KS3 (ca. 254.2–249.4 Ma) contains nine subsequences (stratons) grouped between two major exposure surfaces. By correlation to the Changhsingian Stage and Permian/Triassic Boundary (PTrB) type section in South China, it is interpreted as a dozon with three missing stratons. Khuff Sequence KS2 (ca. 249.4–247.8 Ma) contains the PTrB with an orbital age of ca. 249.0 Ma, compared to 251.0 ± 0.4 in GTS and 249.0–253.0 Ma by radiometric dating in its type section. Khuff sequences KS2 and KS1 contain 13 subsequences (stratons) between ca. 249.4–244.1 Ma spanning latest Permian and Early Triassic. The boundary of the Khuff with the overlying Sudair Formation, Sudair Sequence Boundary, is defined in Borehole SHD-1 (Central Saudi Arabia) and calibrated at ca. 244.1 Ma falling near the age of the Early/Mid-Triassic Boundary in GTS. The enclosed Chart shows a work-in-progress correlation of the six Khuff sequences across the Arabian Plate.
Structural architecture of a thin-skinned imbricate fan: Evidence from Mesozoic deepwater sediments in the Jabal Wahrah area of the central Oman Mountains
Authors: Cooper David J.W. 
Published: October 2021

ABSTRACT
In the central Oman Mountains, Mesozoic deepwater off-margin sediments of the Hawasina Complex were emplaced from the northeast onto the Oman continental margin during the Late Cretaceous obduction of the Semail Ophiolite. Detailed field mapping and structural investigation have shown that, in the area studied, margin-ward detachment of continental rise sediments (Hamrat Duru Group) created two major thrust units in the face of the advancing ophiolite and subduction zone wedge of sediments from more distal parts of the Hawasina Ocean.
The upper unit is preserved in jabals Wahrah and Hurah as a wedge-shaped sheet, restoring to at least 60 km perpendicular to the line of emplacement but only about 500 m thick at its maximum. Its thinner leading edge (Jabal Wahrah) comprises a classic thin-skinned imbricate fan which is divided into five laterally continuous structural zones with finer-grained structures that are influenced by local stratigraphical variations in its Early Jurassic to Early Cretaceous section. The rear part of the thrust sheet (Jabal Hurah) behaved more rigidly, reflecting a thicker and more competent sedimentary sequence spanning the Early Triassic to ?mid Cretaceous. With the exception of a major duplex along its trailing edge, significant internal thrusts are rare and shortening is mostly accommodated by asymmetrical folding. This wedge was emplaced over the trailing edge of a lower thrust unit (Hammat Shulayshil), which formed through forward propagation of the Hawasina sole thrust and which was also deformed primarily through SW-directed folding with limited internal imbrication even after a translation during emplacement of at least 150 km.
A second stage of thrusting after the main emplacement phase is linked to renewed locking of the lowest thrust planes in the imbricated Hawasina sediment wedge ahead of the Semail Ophiolite and late-stage motion transferring to higher structural levels closer to the ophiolite as movement of the latter gradually ceased. This resulted in out-of-sequence re-thrusting of higher thrust sheets over lower sheets along existing thrust planes. This was accompanied by the local rotation of parts of the Jabal Wahrah imbricate fan as an effect of the heterogeneous composition of the overlying thrust units, in particular the out-of-sequence emplacement of a mountain-sized thrust block of intra-oceanic reef limestone (Jabal Kawr) over the Hamrat Duru Group immediately to the east.
A third phase of compression then folded and locally thrusted this re-thrust stack. The timing of this phase is not well constrained. It may represent the final effects of the Campanian emplacement; alternatively it may be tentatively linked to limited lateral motion (gravity sliding) of the thrust stack along the flanks of the Al Jabal al-Akhdar anticline during its main growth phase in the Oligocene.
Organic geochemical characteristics and depositional environments of the Jurassic shales in the Masila Basin of Eastern Yemen
Authors: Hakimi Mohammed H. , Abdullah Wan H. , Shalaby Mohamed R. 
Published: October 2021

ABSTRACT
In this paper, organic matter content, type and maturity as well as some petrographic characteristics of the Jurassic shales exposed in the Masila Basin were evaluated and their depositional environments were interpreted using organic geochemical and organic petrological studies. The total organic carbon (TOC) contents of shales in the Sunah, Wadi Taribah, and Kharir fields vary between 2.4% and 4.7% with high Hydrogen Index (HI) values. All shale samples display very low Oxygen Index (OI) values. The Sunah and Wadi Taribah shales contain Type II organic matter, while the Kharir shales contain Type II, with minor contributions from Type I organic matter.
Tmax values for the shales range from 428 °C to 438 °C and vitrinite reflectance values (%Ro) range from 0.52% to 0.80%. These values reveal that the Sunah and Kharir shales are at peak mature stage while the Wadi Taribah shales are early mature. This is supported by their biomarker maturity parameters.
The pristane/phytane (Pr/Ph) ratios range from 1.8 to 2.3. In addition, all shales show a homohopane distribution which is dominated by low carbon numbers, and C35 homohopane index is very low for all shale samples. All these features may indicate that these shales were deposited in a suboxic environment. Sterane distribution was calculated as C27&gt;C29&gt;C28 from the m/z 217 mass chromatogram for all shale samples.
The Sunah, Wadi Taribah and Kharir shales are believed to have good oil generating potential. This is supported by high total organic carbon content, hydrogen indices up to 400 mg HC/g TOC and early to peak mature oil window range.
Diagenesis and fluid system evolution in the northern Oman Mountains, United Arab Emirates: Implications for petroleum exploration
Authors: Breesch Liesbeth , Swennen Rudy , Dewever Ben , Roure François , Vincent Benoit 
Published: October 2021

ABSTRACT
The diagenesis and fluid system evolution of outcrop analogues of potential sub-thrust Cretaceous carbonate reservoirs in the Musandam Peninsula, northern United Arab Emirates, is reconstructed during the successive stages of the Oman Mountains development. Detailed petrographic and geochemical analyses were carried out on fracture cements in limestones and dolomites mostly situated close to the main faults, which were the locations of major fluid fluxes. The main result of this study is a generalised paragenesis subdivided into four diagenetic time periods. Based on analyses of syn-tectonic veins and dolomites a large-scale fluid system is inferred with migration of hot brines with H2O-NaCl-CaCl2 composition along Cenozoic reverse faults. These brines were sourced from deeper formations or even from the basal decollement and infiltrated in the footwall. These results are compared with similar studies, which were carried out in other regions worldwide.
Furthermore some implications for reservoir characteristics and hydrocarbon scenarios could be postulated. It must be noted that the majority of the analysed rocks do not have sufficiently high porosities to be regarded as reservoir rocks. However, some diagenetic processes that can improve the reservoir quality were observed. For example dolomite recrystallisation occurred in patches at the carbonate platform border, which created poorly connected reservoirs. Other possible exploration targets could be the footwall blocks of the Cenozoic reverse fault zones. When the migration of hot brines along these faults and into the footwall would be combined with petroleum migration, the footwall block could act as a potential hycrocarbon trap sealed by the fault. The fluid system evolution is incorporated in a schematic model of the geodynamic framework of the region in order to summarise the different diagenetic and fluid events, which took place during the northern Oman Mountains evolution up to now.
Seismic modelling of a fractured carbonate reservoir in Abu Dhabi, United Arab Emirates
Authors: Ali Mohammed Y. , Worthington Michael H. 
Published: October 2021

ABSTRACTThe problem of identifying and quantifying the brittle deformation of carbonate reservoirs both in the United Arab Emirates (UAE) and elsewhere is addressed. Naturally occurring fractures may substantially increase or decrease the permeability and porosity of reservoirs, and therefore knowledge of location, orientation, density and connectivity of fractures is required to optimise hydrocarbon production. A rock containing parallel fractures can be seismically anisotropic, provided the vertical and horizontal extent and spacing of the fractures is small compared to the seismic wavelength. Seismic anisotropy may be detectable from attributes of pre-stack 3-D seismic data including reflection amplitude variation with offset and azimuth (AVOA). However, in carbonates seismic-velocity anisotropy can result from many different factors, including present-day horizontal stress anisotropy, sedimentological features such as clinoforms, and geological structure. We present a methodology for determining whether a proposed reservoir-fracture model is consistent with the observed seismic data. The approach includes modelling the seismic anisotropy where an essential input parameter is the compliance of the fractures. Since so little is known about this key parameter, we determine an upper bound to fracture compliance from well data and existing laboratory and field data and consequently obtain an upper bound to the seismic anisotropy that might be detected. We apply our method to data from an onshore carbonate oilfield in Abu Dhabi, United Arab Emirates, where analysis of core, log and 3-D post-stack seismic data indicates that open or partially open fractures may be pervasive and could have a dominant influence on reservoir production. Due to poor AVOA data quality our results are inconclusive. However, this case study is a demonstration of the methodology that could be applied elsewhere.
Biostratigraphy and carbon-isotope stratigraphy of the uppermost Aptian to Upper Cenomanian strata of the South Palmyrides, Syria
Authors: Ghanem Hussam , Mouty Mikhail , Kuss Jochen 
Published: October 2021

ABSTRACT
Biostratigraphic and carbon-isotope data were used to introduce a high-resolution stratigraphic reference section of the Upper Aptian to Upper Cenomanian platform carbonates of the South Palmyrides in Syria. We studied the biostratigraphic evolution of the Zbeideh to Abou-Zounnar formations in two sections, based on 42 species of benthonic foraminifera and 38 species of planktonic foraminifera. Comparisons with other Tethyan assemblages allowed determining 11 biozones; six are based on planktonic foraminifera, and five on benthonic foraminifera. Four hiatuses (earliest Albian, Middle–Late Albian, Late Albian–Early Cenomanian, and Mid Cenomanian) are marked by hardgrounds or dolomitic intervals. The planktonic biozones Ticinella bejaouaensis, T. primula, T. praeticinensis, Rotalipora subticinensis, R. globotruncanoides and R. cushmani co-occur with the following benthonic biozones: Mesorbitolina texana partial range zone, M. subconcava range zone, Neoiraqia convexa taxon-range zone, Praealveolina iberica interval zone and Pseudedomia drorimensis range zone. Within this biostratigraphic framework, a new carbon-isotope curve from the South Palmyrides was compared with δ13C records of the Tethyan Realm and England that allows identifying several biotic events and Oceanic Anoxic Events (OAE), recorded in the Upper Albian to Upper Cenomanian succession. The combination of sequence-stratigraphic interpretations and comparisons, with our results have led to an improved understanding of the Cretaceous platform architecture of the South Palmyrides that links the Arabian Platform to the east with the Levant Platform to the southwest.
MIDDLE EAST GEOLOGIC TIME SCALE 2013
Authors: Al-Husseini Moujahed I. 
Published: October 2021

ABSTRACTDuring the Aptian 28 to possibly 34 transgressive-regressive “fourth-order” sequences were deposited on the Arabian Plate. The sequences were controlled by sea-level fluctuations with a relative amplitude of 5–20 m. The fluctuations are interpreted as the glacio-eustatic response to orbital-forcing and assumed to have an average duration of 405 Kyr corresponding to the long-eccentricity orbital cycle. The sequences are referred to as “stratons” and calibrated in the orbital time scale of Matthews and Al-Husseini (2010, abbreviated M&H-2010). An independent study by Huang et al. (2010) counted nearly 33 cycles of 405-Kyr in a deep-marine Aptian succession in the Piobicco core in central Italy. The Italian cycles and Arabian stratons can be correlated in GTS 2004 by the position and age of the oceanic anoxic event OAE1a (Selli Interval, ca. 124.5–123.1 Ma). Two lowermost Aptian stratons and at least nine upper Aptian ones show stratigraphic geometries that imply 40–50 m box-like drops in relative sea level. They provide evidence for the formation of an ice sheet, mainly in Antarctica, that held several 10s of meters sea-level equivalent. The ca. 5-Myr-long late Aptian drop started at Global SB Apt 5 (ca. 117.9 Ma), which correlates to a major eccentricity minimum predicted at 118.2 Ma in the M&H-2010 scale. Similar minima are predicted to recur every 14.58 Myr (36 × 405 Kyr), and to cause major glacio-eustatic drops and regional sequence boundaries (SB). The youngest SB 0 is predicted at 1.586 Ma, and SB 8 (118.2 = 1.586 + 8 × 14.58 Ma) is interpreted to have triggered the late Aptian glaciation. The M&H-2010 scale was tested against the high-resolution sea-level curve derived from benthic foraminiferal δ18O isotopes for the late Miocene to Holocene (9.25– 0.0 Ma, Miller et al., 2005, abbreviated Metal-2005). Antarctica’s glacio-eustatic signature is interpreted as high-frequency sea-level fluctuations with a period of 41 Kyr (obliquity) above -20 m relative to present-day sea level. The fluctuations ride up-and-down on longer-period sea-level cycles (transgression-regression) with amplitudes of 20–40 m. The cycles are bounded by prominent lowstands, have durations of 325–545 Kyr, and an average duration of 405 Kyr. Sequence Boundary SB 0 (predicted at 1.586 Ma) is interpreted at 1.54 Ma, and correlated to Calabrian Global sequence boundary Cala1 (1.54 Ma).
Age and paleoenvironment of the Nukhul Formation, Gulf of Suez, Egypt: Insights from palynology, palynofacies and organic geochemistry
Authors: El Atfy Haytham , Brocke Rainer , Uhl Dieter 
Published: October 2021

ABSTRACTPalynological results of a detailed study carried out on 56 samples retrieved from two selected wells (GH 404-2A and SA-E6A) of the Hilal and Shoab Ali fields within the southern part of the Gulf of Suez, Egypt, are presented. This study is mainly focused on the poorly dated Nukhul Formation, for which very little information from palynology is available despite its importance from a petroleum viewpoint. The assemblages discovered in our study are moderately preserved and reveal a sparse but significant record of spores and pollen and dinoflagellates together with highly diverse fungi and algal taxa, e.g. Botryococcus and Pediastrum.A latest Oligocene–Early Miocene (Chattian–Aquitanian) age has been suggested for the Nukhul Formation, based on compiling palynostratigraphic and ecologic data obtained from palynomorphs that have previously been assumed to be representatives for this period on a regional scale. In addition, the Oligocene/Miocene Boundary (OMB) could be lithostratigraphically defined within the studied formation, most likely at the boundary between the lower Shoab Ali Member and upper Ghara Member. A fungal/algal ‘event’ within the interval from 11,370–11,430 ft in the GH 404-2A Well may be associated with a strong regressive phase. Such a regression was previously observed in the Nile Delta and other locations around the Red Sea province, and may be assigned to the global Mi-1 glaciation event at the OMB. However, not only glacial-driven eustacy but also tectonic activity related to the Gulf of Suez rifting may have contributed in forming such an event.Palynofacies investigations were carried out under both transmitted and fluorescence microscopy and the results were partly supplemented by existing organic geochemical analyses (GH 404-2A Well) involving Rock-Eval pyrolysis and total organic carbon (TOC) measurements. The analysis was used to interpret the depositional regime, paleoenvironment and thermal maturation history of the studied succession. These results support the temporary existence of shallow, pond- or lake-like aquatic habitats during deposition of the lower Shoab Ali Member that evolved into a shallow-marine environment with the onset of the deposition of upper Ghara Member of the Nukhul Formation.
Origin of gypsiferous intrusions in the Hawasina Window, Oman Mountains: Implications from structural and gravity investigations
Authors: Ali Mohammed Y. , Cooper David J.W. , Searle Michael P. , Al-Lazki Ali 
Published: October 2021

ABSTRACT
Gypsiferous intrusions are exposed in road-cuts in the south-central Hawasina Window in the central Oman Mountains. They are located at lower structural levels in the allochthonous Hawasina Complex and lie along faults that cut Upper Cretaceous structures related to the obduction of the Semail Ophiolite and Hawasina Complex deep-water sediments onto the Arabian Plate. The intrusions form gypsiferous pods that are up to 200 m long, in which the gypsum occurs as a dark, fine-grained matrix that contains a pervasive network of anastomosing veins of gypsum and anhydrite. The intrusions contain abundant sub-angular to sub-rounded litharenites, and less common fragments of chert and fine-grained limestone. Although these clast types are undated, their petrographic characteristics suggest they originate from the local Hawasina (Hamrat Duru Group) country rock. Very well-rounded pebbles and cobbles of feldspathic litharenites, some of which show a well-developed cleavage, and rarer cobbles of well-rounded vein quartz appear to have come from the basement. Gravity investigations indicate salt diapirs are not present beneath the Hawasina Window. Instead, the gypsiferous intrusions are interpreted as having been brought up from depth during compression to form disconnected pods along deep-rooted faults, bringing with them small amounts of the basement country rock. Strontium isotope analysis and regional considerations, in particular the distribution, age and nature of other evaporite units on the eastern Arabian Plate, suggest the gypsum may have its origins in the Neoproterozoic (Ediacaran) to lower Cambrian Ara Group evaporites, perhaps from a previously unknown extension of the Fahud Salt Basin beneath the Hawasina thrust sheets.