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Fourth EAGE Workshop on Arabian Plate Geology
- Conference date: 09 Dec 2012 - 12 Dec 2012
- Location: Abu Dhabi, United Arab Emirates
- ISBN: 978-94-6282-059-3
- Published: 09 December 2012
38 results
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Keynote Speech: Prof. J. Fred Read (Virginia Tech, USA)
By J. Fred ReadCarbonate platform types relevant to the Jurassic-Cretaceous passive margins of the region include homoclinal ramps, with uniform gentle slopes on the deep ramp of 0.1 degree to a few degrees, along with low energy, distally steepened ramps, in which the gently sloping deep ramp distally steepens (up to several degrees) into the basin, and rimmed margins, characterized by reefal rims and steeper marginal slopes. Modern analogs for interiors of the immense, relatively flat topped platforms that typify the Arabian Peninsula are lacking. Differentiation of the platform interiors generated large intrashelf basins and source rocks in silled, stratified settings, bordered by basinward prograding ramp systems. Low sedimentation rate in platform interiors, differential subsidence and siliciclastic poisoning all may have played a role in formation of the intrashelf basins.
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The Relation between Regional (Palaeo-)stress Engines, Sand Machines, and Carbonate Factories in the Middle East Region
By A. KoopmanRelative sea-level fluctuations exert primary control on patterns of sediment dispersal and differential erosion. Generally subtle, but locally significant lateral variations of “carbonate factories” and “sand machines”, are critically controlled by the combined effects of the global eustacy record and regionalscale structural evolution of the Arabian Plate. It is generally accepted that regional-scale structural development is related to plate-boundary forces, associated with plate-tectonic models of Neo-Tethys, throughout its Mesozoic history. An assessment of the main driving forces (“stress engines”) involved may contribute to better-constrain structural framework models for the Mesozoic Middle East region, including the Late Jurassic–Early Cretaceous time period. No full paper available.
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Sequence Stratigraphy and Depositional Systems in the Late Jurassic to Early Cretaceous (Oxfordian to Valanginian) of the Arabian Plate: Implications for Regional Exploration and Reservoir Description
Authors R.B. Davies and M.D. SimmonsThe Oxfordian to Valanginian succession on the Arabian Plate is dominated by carbonate shelves and intrashelf basin deposits. Evaporites are a major component of Kimmeridgian to Tithonian deposition in both shelf and basinal locations. Siliciclastics are less important, though they increase in the Early Cretaceous. Important petroleum systems reflect the presence of numerous source, reservoir and seal combinations. Local stratigraphy is well understood where there are major petroleum systems but there are considerable stratigraphic, depositional and preservational variations across the Arabian Plate and correlations between more distant areas are not well documented. There is a dearth of comprehensively documented age control. Nevertheless careful sequence stratigraphic analysis means that many correlations can be established, and that a plate-wide sequence stratigraphic framework can be applied. Sharland et al (2001) identified ten plate-wide maximum flooding surfaces in this succession. Further work continues to validate these surfaces world-wide. We use them to discuss the sequence stratigraphy of the interval across the entire Arabian Plate and its importance for future exploration and detailed reservoir description. Our methodology facilitates high resolution Gross Depositional Environment mapping and detailed play fairway analysis. This is fundamental to identifying new stratigraphic trap and continuous play potential across the Arabian Plate.
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Stratigraphic Aspects of the Upper Jurassic to Lower Cretaceous of Saudi Arabia
By G.W. HughesThe Upper Jurassic to Lower Cretaceous, Oxfordian to Valanginian, lithostratigraphic succession of Saudi Arabia is divided into the Jurassic Shaqra Group and the Cretaceous Thamama Group, the boundary of which lies within the uppermost Tithonian. This interval includes at least five third-order sequence boundaries and maximum flooding zones. J60 and K40 are two regionally recognized sequence boundaries, and J50 and J100 represent two regionally established Jurassic maximum flooding surfaces. The Upper Jurassic succession includes shallow- to deep-marine carbonates of the Hanifa (Oxfordian) and Jubaila (Kimmeridgian) formations, and shallow-marine carbonates and evaporites of the Arab (Kimmeridgian) and Hith (Kimmeridgian to Tithonian) formations. The Upper Jurassic to Lower Cretaceous succession includes the shallow to moderately deep carbonates of the Sulaiy Formation (Tithonian to Berriasian) with the overlying Yamama Formation being of Cretaceous age (Valanginian). These formations were deposited in a period of increasing global temperature, during a transitional phase leading to greenhouse.
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Middle Jurassic to Early Cretaceous Calcareous Nannofossils from Onshore North Kuwait: A New Record
Authors A.P. Kadar, S. Crittenden and K.A. KaramA new record of calcareous nannofossil datum markers from Middle Jurassic to Early Cretaceous (Aalenian to Valanginian) strata of onshore North Kuwait has been calibrated with nannofossil marker species of the global Jurassic to Early Cretaceous nannofossil biostratigraphy schemes and compared with calcareous nannoplankton assemblages recorded from Lower to Middle Cretaceous strata offshore Kuwait. The studied sections embrace, in ascending order, the Dhruma, Sargelu, Najmah, Gotnia, Hith, Makhul, Minagish and Ratawi formations and comprise argillaceous limestones, grainstones, packstones, bituminous packstones, wackestones, dolomite, anhydrite, laminated bituminous calcareous mudstone and calcareous shales all representative of a variety of environments from marginal marine (sabkha) and shallow hypersaline (salina) to fully marine mid to outer shelf settings.
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Callovian to Valanginian Chemostratigraphy of the Eastern Arabian Plate Margin
Authors V. Vahrenkamp and A. Al MansooriFollowing the breakup of Gondwana the northeastern passive margin of the Arabian Plate entered during the Permian a period of long-term thermal subsidence that lasted until renewed tectonic activity in the Early Turonian. This resulted in the more-or-less continuous deposition of mainly carbonate shelf sediments with the section reaching a thickness of up to 4,000 m. A composite carbon-isotope profile for the Callovian to Cenomanian time period has been generated for the eastern Arabian Plate using more than 2,000 carbon-isotope data. The profile has some 1,800 m thickness, is anchored by biostratigraphy, Sr-isotope data and tightly sampled carbon-isotope profiles from various cross-correlated cored wells in the United Arab Emirates and Oman. Further time control is provided by correlation with published curves of carbon-isotope ratio variations through time mainly form the northern Tethys carbonate sequences. A large data set of strontium-isotope data provides absolute time control via correlation with well-dated curves of strontium-isotope ratio variations in seawater over time.
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Middle Jurassic to Early Cretaceous Petroleum Systems of the Arabian Plate
Authors G.J. Grabowski, D.E. Sherrett, T.W. Jones, W.B. Maze and J. KendallWhat are arguably the most prolific petroleum systems in the world are driven by multiple world-class source rocks. These highly organic-rich rocks account for most of the discovered oil and gas on the Arabian Plate. The source rocks were deposited in widespread shallow-marine intrashelf basins and deep-marine basins. They differ in age between basins and are not correlative with global occurrences of organic enrichment. Burial under Mesozoic and Cenozoic strata has caused the source rocks to generate oil and gas. Timing of generation differs mainly by variations in sedimentary load; differences in the kinetics of generation and regional heat flow play a lesser role. In the west of the Arabian Plate, generation occurred under Cretaceous and Paleogene sedimentary load, whereas in and near the Zagros Foldbelt generation continues under recent syntectonic sedimentary load. The most organic-rich source rocks are carbonates containing mainly marine (Type-I/II) organic matter that has generated sulfur-bearing oil and gas. The gas in some carbonate reservoirs is further enriched in H2S derived from thermal-sulfate reduction. Clay-rich source rocks contain a mixture of marine and land-plant (Type II/III) organic matter and have generated a mixture of low-sulfur oil and gas. Gas is more common also where the source rocks are deeply buried and more thermally mature. Low-angle structural dip of highly continuous strata allowed oil and gas to migrate laterally for greater than 150 km from areas of generation to traps, limited only by the extent of structural dip and continuous seal. Intervals of widespread evaporite and shale acted as barriers to vertical migration. Oil and gas migrated to younger rocks through gaps in migration barriers caused by non-deposition or erosion, including localized karst dissolution, or by faults that pierce these migration barriers, commonly where they are thin. Oil and gas generated from Jurassic and Early Cretaceous source rocks are found in many Jurassic, Cretaceous and Cenozoic reservoirs, but rarely occur in older rocks. The Arabian Plate is reservoir rich, with multiple reservoir-seal pairs for oil and gas accumulations. Most reservoir rocks are shallow-marine carbonates and paralic sandstones, but nonmarine and deep-marine sedimentary rocks and even fractured basement are reservoirs in some basins. Shallow burial and limited cementation in the subsurface have favored preservation of porosity and some superb reservoir quality. Most traps are structural. Compressional thrusted anticlines dominate the Zagros Foldbelt, whereas compressional anticlines with reactivated basement-involved faults occur on the Arabian Platform. Halokinesis of deeply buried Cambrian-Precambrian salt forms traps, especially in the offshore Gulf and in Oman. Extensional faulted anticlines form traps in rift basins, notably in Syria and Yemen. The few discovered stratigraphic traps include truncation pinchouts and reefal buildups.
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Northern Rub' Al-Khali Upper Jurassic – Lower Cretaceous Petroleum System
Authors P. van Laer, P. Nederlof, S.A. Ahsan and F. Al KatheeriThe Jurassic–Lower Cretaceous petroleum system in the northern Rub’ Al-Khali Basin contains some of the largest oil and gas accumulations of the Middle East. Carbon isotopes and biomarkers indicate that the main source of hydrocarbons originated from the Jurassic-aged Tuwaiq Mountain and Hanifa basinal source rocks. Other source rocks, despite being less significant and being often overlooked, have also contributed in considerable amounts to the charge and include the Jurassic Jubaila and the Lower Cretaceous Habshan, Thamama and lower Bab intervals. All these source rocks are marine carbonates and the kerogen type is mainly, but not exclusively, represented by the oil-prone, low-activation energy and sulphur-rich type IIS. We are presently reviewing the stratigraphic setting of the source rocks to better map out their thickness distribution and initial source rock properties.
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Geochemical Characterization and Volumetric Assessment of the Prolific Mesozoic Source Rocks of the Northeastern Arabian Plate
More LessThe Middle-Upper Jurassic and Lower Cretaceous strata of the NE Arabian Plate contain several prolific world-class source rocks for some of the largest petroleum systems globally. They are located within the Zagros and Mesopotamian Foreland Basins covering north, central and south-eastern parts of Iraq together with western and south-western parts of Iran, particularly the Lurestan and Khuzestan provinces. These source rocks principally include the Bajocian–Bathonian Sargelu, the Callovian–Early Kimmeridgian Naokelekan and the Late Tithonian–Early Berriasian Chia Gara Formations of Iraq and their chronostratigraphic equivalents in Iran. They have charged the main Cretaceous and Tertiary reservoirs throughout Iraq and Iran (in various trap types and sizes) with more than 250 billion barrels of proven recoverable hydrocarbons.
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Regional Framework and Controls on Jurassic Evaporite and Carbonate Systems of the Arabian Plate
More LessDetailed sequence stratigraphic framework shows distribution of evolving sedimentary facies on varying spatial and temporal scales and provides an understanding of the chronostratigraphy, tectonics, climate, palaeogeography, depositional systems and diagenetic trends and petroleum systems of the region and identifies potential exploration plays. Framework is subdivided by surfaces that are the product of local low frequency tectonic movement, associated with Wilson's cycles of tectonic plate motion; further subdivided by surfaces formed during higher frequency eustatic changes in sea level and varying rates of sediment accumulation. Jurassic fields are in shallow water carbonate and evaporite sediments in Saudi Arabia Kuwait, Qatar, the UAE and Yemen associated with high rates of organic production that accumulated in the arid rain shadow of the lea shores of the equatorial seaway flanking the eastern margin of Gondwanaland and the consequent restricted basins were confined behind structural and/or depositional barriers that formed over Hercynian structural highs. The Jurassic section common shallow water carbonate play elements are tied to platform evaporite depositional settings that are comprised of sabkha, salina, and mudflats; and subaqueous salterns; and shallow or deep basin center evaporite plays.
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Upper Jurassic to Lower Cretaceous Stratigraphic Model for the Eastern Arabian Plate
By H.J. DrosteA new stratigraphic model for the Upper Jurassic to Lower Cretaceous has been constructed for the eastern Arabian plate based on well correlations calibrated with seismic.
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Latest Jurassic to Early Barremian Carbonate Systems from the United Arab Emirates to Oman: Regional Stratigraphic Architecture and Controlling Factors
Authors P. Razin, C. Grélaud, E. Dujoncquoy and A. LebecThe latest Jurassic–Early Barremian carbonate systems of the United Arab Emirates (UAE) and Oman are organized as a succession of prograding wedges over almost 300 km towards the northeast. The integration of outcrop and subsurface data allows the definition of clinoform architecture, the proposal of regional correlations, and the characterization of the main stages of evolution of this part of the Arabian Plate (Figure 1).
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Stratigraphy and Depositional History of the Marib-Jawf Basin, Yemen
More LessThe sedimentary fill of the Marib-Jawf Basin is Jurassic and Lower Cretaceous. Initial marine transgression occurred in the Middle Jurassic, with the Kohlan Formation unconformably overlying Paleozoic sedimentary rocks and Precambrian basement. These basal fluvial to nearshore-marine sandstones and shales are conformably overlain by intertidal to shallow-marine carbonates of the Saba Formation of Callovian-Oxfordian to Kimmeridgian age. Extensional faulting formed grabens that deepened during the Kimmeridgian and Tithonian. Up to 6000 feet (2000 meters) of deep-marine sediments unconformably overlie and lap onto high margins of the basin. At the base are outer-shelf/slope argillaceous carbonates and shales of the Arwa Formation. These pass upwards into slope and basinal shales with minor limestones and sandstones of the Meem Formation, which in turn are overlain by shales with interbedded sandstones and limestones of the Lam Formation. The sandstones were deposited by turbidity currents from the margins of the basin, where submarine fan deposits are present. Shales of the Meem and Lam formations are organic rich and are the source rocks for most of the oil and gas in the basin. A drop in relative sea level occurred in the middle to late Tithonian with restriction of the basin from the open ocean. Three progradational sequences (Yah, Sean and Alif Members of the Alif Formation, from base to top) of fluvial-alluvial to deltaic-marine siliciclastic sediments were deposited down the axis of the basin, passing into offshore-marine shales and basinal evaporites to the east. The sandstones are the main reservoirs for oil and gas in the basin. A transgressive shale at the top of the Alif Formation records marine flooding of the basin, followed by deposition of five sequences of basin-filling evaporites of the Safer Formation. Thick halite beds were deposited subaqueously when the basin was filled with hypersaline water and have thin anhydrite beds at top and base. These evaporites are separated by lowstand fluvial to shallow-marine siliciclastics, including thin, organic-rich shales that are minor source rocks for oil. The evaporites are the primary seal for the reservoirs of the Alif Formation. Berriasian-Valanginian shelfal-marine shales and limestones of the Azal Formation unconformably overlie the Safer evaporites. The lower part of the Azal Formation is dominantly limestone and shale, the middle is shale with few thin limestones, and the upper unit has limestone, shale and minor sandstone. These are overlain by the Tawilah Group, possibly as old as Valanginian-lower Hauterivian and at least as young as Aptian in parts of the basin, equivalent to the Qishn Formation to the east. The Tawilah Group is dominated by nonmarine to shallow-marine sandstones and shales with minor thin dolomite and skeletal-limestone beds. Regional erosion truncates the sedimentary fill of the basin, progressively cutting out more strata toward the west and in places exposing Middle Jurassic rocks at the surface.
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Stratigraphic Architecture of the Latest Jurassic - Early Cretaceous Carbonate Platform System of Abu Dhabi, United Arab Emirates (UAE)
Authors C. Grelaud, P. Razin, V. Vahrenkamp, D. Popa, F. Al Katheeri, P. Van Laer and K. LeyrerThe integration of subsurface and outcrop data has allowed to build a 200 km NW-SE correlation transect across 7 oil fields in Abu Dhabi. It reveals new possible concepts on the stratigraphic organization of the Late Jurassic-Early Cretaceous systems in the U.A.E.
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Upper Arab Reservoir Correlation in a Giant Gas Field in the United Arab Emirates: Integration of Core, Log, Borehole Image & Pressure Data
Authors F. Al Darmaki, D.A. Lawrence, R.P. Singleton, N. Lucas and E. SwindellsThe upper interval of the Arab Formation is a secondary reservoir objective in a major gas field currently under development in onshore Abu Dhabi, United Arab Emirates (UAE). This presentation will illustrate the impact of integrating core sedimentological descriptions, log response, borehole image and pressure data to develop a sequence-stratigraphic correlation of thin reservoir targets in the upper interval of the Arab Formation.
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Field-scale Heterogeneity of Carbonate Reservoirs from the Arab Fm – Lessons Learned from Seven Case Studies
Authors B.P.R Caline, C. Maza, A. Roumagnac, E. Zuckmeyer and M. RousseauPreparation of robust reservoir model from the Arab Fm relies on thorough characterization of the different carbonate facies from core and thin section examination. However the key step remains to properly extrapolate the detailed facies recognition in cored wells to uncored wells. The objective of this presentation is to illustrate how electrofacies have been successfully first calibrated on few cored wells and then extrapolated to all uncored wells in several hydrocarbon fields in UAE (5 fields) and Qatar (2 fields). The sedimentary interpretation of the Arab reservoirs from the different studied fields is primarily based on the integration of: - high-resolution stratigraphic architecture of the carbonate-evaporite series allowing subdivision of the reservoir interval into meter-scale stratigraphic units, - recognition of depositional and diagenetic trends within each stratigraphic unit in order to constrain the distribution of the main facies. Special attention was paid to properly define along selected cored wells a number of pre-rock types; each of them being characterised by a specific log signature and porosity/permeability relationship. Once this calibration exercise has been carried out, the pre-rock types have been propagated to uncored wells. The robustness of the propagation needs to be validated by few blind tests on cored wells not used in the calibration step. This method has proved to be successful in recognition of the main reservoir facies including grain-supported facies affected by tar mat deposition. Preparation of maps per stratigraphic units where both thickness and proportion of electrofacies are displayed on well basis is used to constrain the field-scale distribution of reservoir facies taken into account the depositional and diagenetic trends provided by regional paleogeographical reconstruction. Results from the seven field case studies will be highlighted during the presentation.
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Regional Stratigraphic Framework, Depositional Environments, and Exploration Concepts of the Upper Jurassic Carbonates and Evaporites, Saudi Arabia
Authors D.Z. Tang, P. Lawrence, W. Tan, A.F. Bakhiet, G. Gregory, S. Wharton and K. ShokairThe Jurassic carbonates host significant oil reserves and produce from giant and super giant oilfields. The Upper Jurassic (Oxfordian) Hanifa Formation and Middle Jurassic (Late Callovian) Tuwaiq Mountain Formation contain world-class hydrocarbon source rocks and carbonate reservoirs. The grainy carbonates of the Arab A, B, C, and D members are among the best Jurassic carbonates reservoirs. The Hith Formation evaporites (Tithonian) provide excellent regional seal of the exceptionally prolific Jurassic petroleum systems. Understanding the regional stratigraphic framework by integrating core, well-logs, and 2-D/3-D seismic interpretations is essential for unlocking the hydrocarbon exploration potential and new exploration opportunities. The Hanifa reservoirs (skeletal/oolitic limestones and packstones) were deposited as prograding clinoforms during the highstand of the Hanifa third-order composite sequence along the margins of the Hanifa intrashelf basin, which was inherited from the Tuwaiq Mountain intrashelf basin. The Hanifa grainstone shoaling complexes shifted further basinward as a result of continuous carbonate growth and progradation, progressively infilling most of the accommodation space that was created after Bathonian time. The organic-rich mudstones of both the Tuwaiq Mountain and Hanifa formations were deposited in the intrashelf basins of the Jurassic Arabian carbonate platform interior. An early Kimmeridgian base-level fall, as revealed from core and 3-D seismic chronostratigraphic analysis, terminated the Hanifa carbonate platform and resulted in substantial subaerial exposure of previous grainstone shoaling complexes and proximal areas. A renewed regional transgression occurred post-Hanifa time, leading to deposition of the Jubaila Formation and infilling the remaining accommodation space. Widespread deposition of packstones and grainstones of the Arab-D Member represents the maximum flooding and the beginning of the late Kimmeridgian sea level fall, which resulted in the deposition of Arab-A, B, C members, and pervasive Hith anhydrite deposits across the region, marking the turning point from a predominantly carbonate factory to an overall evaporite factory. Gross depositional environment (GDE) maps of the Upper Jurassic formations have been reconstructed by integrating core/drill cutting sedimentology, well-log electrofacies, and seismic attributes. These GDE maps depict evolving depositional environments that span the Hanifa intrashelf basin, Arab Formation carbonate platform, and finally the Hith evaporite system. A variety of new exploration concepts has emerged through building a robust stratigraphic framework and reconstruction of gross depositional environments.
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Sequence-stratigraphic Framework and Depositional Facies Interpretations in Late Jurassic to Early Cretaceous Section in Saudi Arabia/Kuwait Partitioned Zone (PZ)
Authors Q. Ye, K.D. Kelsch, D. Angstadt, K. Sukhdarshan and R. CorleyHydrocarbons have been found and produced for a long time in PZ area, however, a sequence stratigraphic framework study has never been carried out previously due to poor seismic data. With increased effort in exploring new resources and characterising existing base production, a comprehensive study to examine the sequence stratigraphic framework is vitally important in PZ area. This study is aimed to achieve part of that goal for improved evaluation of future exploration targets.
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Structural and Stratigraphic Trapping of Hydrocarbons within Late Jurassic to Early Cretaceous Section as Observed from Drilling and 2-D/3-D Seismic in Partitioned/Divided Zone of the Kingdom of Saudi Arabia/Kuwait
Authors K. Kelsch, S. Kumar, S. Al-Anazi, R. Corley, M. Ye, P. Thompson and Y. Ahmad MohammadStructural and stratigraphic traps in the Partitioned/Divided Zone (PZ) between the Kingdom of Saudi Arabia and Kuwait suggest minimal tectonics during carbonate build-ups within the Late Jurassic to Early Cretaceous (Figure 1). Today, these same reservoirs are structurally compartmentalized as determined from pressure data, wells and the incorporation of an array of 2-D/3-D seismic data (Figure 2).
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Makhul Formation in Kuwait
Authors G. Gega, A. Al-Fares, G. Ghaida Al-Sahlan, M. Al-Baghli and P. ClewsThe Makhul is an unconventional formation in Kuwait. This paper will compare the Makhul Formation in Kuwait with the Makhul Formation in other Arabian Plate countries and add insights to the differences of the sequence stratigraphy and sedimentology to other studied areas. The sedimentology study provides additional insight into the environments of deposition and digenesis of the Makhul in Kuwait to aid in the complete understanding of this formation. Core, cuttings, thin sections, logs will be evaluated to provide the study with comprehensive insight.
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Distribution of the Reservoir Properties in the Minagish and Rawati Formations (Kuwait): A Complex Interplay of Sedimentation, Depositional Architecture and Diagenesis
Authors H.R. Al-Muraikhi, D. Dutta, S.N. Al-Anezi, B. Vincent, J. Garland and P. GitteridgeMiddle Minagish (Tithonian-Berriasian) and Ratawi (Valanginian) Formations, are oil bearing carbonate reservoirs in the Umm Gudair field of Kuwait. Reservoir property varies widely between these two, due to significant variation in the interplay of sedimentation, depositional architecture, and diagenesis. In order to constrain reservoir properties and predicting their distribution, this study integrates data pertaining to sedimentology, sequence stratigraphy, high resolution petrography, of 3 cored wells (900ft of cores) from the Minagish, and 2 cored wells (350ft of cores) from the Ratawi Formations.
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Integrated Core and Log-based Approach to Enhancing the Understanding of Reservoir Distribution within the Arab Formation, Abu Dhabi: Constraining the Future Reservoir Model Build
Authors K. Garrick, G. Al-Jefri, H. Al-Menhali and I. Al-TamimiCorrelation and prediction of reservoir quality variability/heterogeneity within shallow carbonate ramp deposits of the Arab Formation in an Abu Dhabi offshore field has previously proved challenging. This study, commissioned by ADMA-OPCO, presents the results of integrated sedimentology and reservoir quality assessment of the A to D members of the Arab Formation.
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Characterizing the Relationship between Petrophysical Trends and Diagenetic Cementation Patterns: A Case Study from a Carbonate Arab Reservoir in the Dukhan Field, State of Qatar
Authors H. Al-Ansi, M. Al-Wehaibi and R. StanleyThe Upper Jurassic Arab-C Reservoir in the Dukhan Field is the product of a stable epicontinental shelf subjected to continuous relative sea-level variations, with the preserved sediments representing a complex of syndepositional carbonate lithologies and textures deposited in subtidal, intertidal and sabkha environments. Though the depositional units are spatially correlated within a sequencestratigraphic context, petrophysical observations do not conform to the primary depositional fabric, and a cross-cutting relationship is observed.
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Pre-Buwaib and Late Valanginian Unconformities in Outcrop: Inherited Concepts, Facts, and Stratigraphic Consistency
Authors A.M.S. Memesh, Y.M. Le Nindre, S.M. Dini and D. VasletIn Saudi Arabia, a pre-Buwaib unconformity was mentioned by Powers et al., (1966) on bases of angular discordance and of biostratigraphic changes. According to the Hauterivian and Valanginian ages assumed for Buwaib and underlying Yamama formations respectively by Powers, this unconformity should be equivalent to the late Valanginian unconformity. In fact, both arguments given by Powers for this unconformity were since subject to objection. Therefore, based on previous geological mapping by BRGM-DMMR and on two recent maps by SGS, we discuss the pre-Buwaib unconformity in outcrop and the age of the hiatuses from lat. 26°N to lat. 21°N. This formation is associated to the cycle GSS K30 and the Late Valanginian unconformity is thus identified as the pre-Biyadh unconformity and not as the pre-Buwaib unconformity.
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Burial Dolomitization, Late Leaching and Thermochemical Sulphate-reduction Diagenesis in Arab C and D Reservoirs (Kingdom of Saudi Arabia): Impact on Reservoir Properties
Authors C. Taberner, G. Sosa, A. van den Kerkhof, J. Sneep and A. BellDiverse diagenetic processes have been proposed to explain the reservoir properties of the Arab C and D reservoirs in the Middle East: from early diagenesis (e.g. early cementation, dissolution and/or dolomitization) to burial and late burial diagenesis (e.g. compaction, cementation, burial dolomitization, leaching, hydrothermal/fault-related dolomitization). This contribution examines the Arab C and D reservoirs from an onshore field in Saudi Arabia with specific focus on: (1) late diagenetic evolution; (2) timing of burial diagenesis with respect to charge; and (3) their impact on reservoir rock and fluid properties.
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Evidence of Glacio-eustacy during the Late Berriasian to Late Valanginian: Record in the Lekhwair/Habshan/Salil Prograding Geometries, Rayda Basin, Sultanate of Oman
Authors E. Dujoncquoy, P. Razin, C. Grélaud, P. Imbert and G. DupontThe Lekhwair/Habshan/Salil (or LHS) system is a carbonate succession that prograded by 300 km toward the northeast across the eastern part of the Arabian Plate (Rayda Basin) from Berriasian to Early Barremian. The system is organized as a series of large prograding clinoforms with amplitudes ranging from 200 to 350 m.
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A 3D Seismic Chronostratigraphy and Attribute Assessment of Late Jurassic Evaporite Sequences at the Gothnia Basin Margin, Saudi Arabia
Authors S. Wharton, A.M. Bakhiet and P. LawrenceThe Jurassic sequences on the Arabian Platform contain widespread carbonate reservoirs, source rocks and seals, which contribute to a world class petroleum system. Since the Triassic period, the Platform was subjected to alternating periods of transgression and regression and differentiation with intrashelf basins. One key variation in sediment deposition was the formation of evaporite seal beds associated with these intrashelf basins. To elucidate the basin depositional history near the flank of the Gothnia Basin margin, a 3D seismic chronostratigraphy technique and attribute assessment were adopted to assess the evaporite distribution during the Late Jurassic. Seismic chronostratigraphy cubes and Wheeler transform models were generated and interactively assessed for structural controls to deposition and assessment of transgression and regression, unconformity and hiatus events at the basin margin. The seismic chronostratigraphy model, which represents dense semi-automatically generated horizons chronostratigraphic order, was derived from mapping samples in the seismic trace. This allowed the interactive assessment of the Jurassic basin margin depositional history in both time and space, and use of horizon sets for attribute and geobody assessment. The techniques applied in this study area proved beneficial in accurately defining the limits of the evaporite salt beds and basin depositional history during the Late Jurassic
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Subsurface Jurassic-Cretaceous Dolomitization Front Mapping and Characterization, Onshore-Offshore Northeastern Saudi Arabia
Authors W. Tan, D. Tang, K. Shokair, P. Lawrence and A.F. BakhietMassive dolomite had long been documented in the Upper Jurassic and Lower Cretaceous carbonates in the northern regions (onshore and offshore) of Saudi Arabia. These dolomite bodies are characterized by their stratigraphically discordant geometries. Recently more geologic and seismic data have been acquired. Accordingly, a study with the following aims have been undertaken; 1) re-map the dolomite bodies and refine their spatial-temporal geometries, 2) document diagenesis and reservoir qualities within dolomite bodies and across dolomitization front, 3) define a dolomitization system that helps understand the mechanisms of dolomitization and associated diagenetic processes, and 4) predict reservoir qualities within the dolomitization system. This study benefited from integration of variety of data such as core/cutting sedimentology, thin-section petrography, drilling attributes, well logs and seismic attributes. This integrated approach helped not only identify the geometries of dolomite bodies but also depict their fractured natures. Preliminary results revealed that the dolomitization system contains 1) massive dolomite bodies with a spectrum of dolomite textures, varying from very fine to macro-crystalline; 2) a wide range of associated diagenetic processes, including precipitations of ferroan-nonferroan calcite, anhydrite, gypsum, fluorite, kaolinite, silicification (quartz/chert); dedolomitization, emplacement of pyrobitumen-hydrocarbon, and fracturing-leaching; 3) dolomite bodies which show chaotic seismic reflection characters, and exhibit “tornado” geometries when capped with anhydrite seals; and 4) variations in reservoir qualities within dolomite bodies and across dolomitization fronts, which results in reservoir heterogeneities and the potential diagenetic-stratigraphic traps. Two mechanisms have been proposed for onshore and offshore massive dolomitization in terms of their depositional and structural characteristics. This paper offers our current understanding of the Upper Jurassic-Lower Cretaceous regional dolomitization system and diagenetic processes, and provides great insights for reservoir prediction and potential stratigraphic trap exploration opportunities.
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The Influence of Relative Sea Level Variation on Depositional Settings of the Late Jurassic Arab Formation in a Giant Gas Field, United Arab Emirates
Authors D. Green, D.A. Lawrence and M. Al MansouriDetailed core description of multiple wells within a giant UAE gas field has enhanced understanding of the depositional make-up and possible controls on depositional style for the Arab Formation. In this field, the Arab Formation differs from other areas such as Qatar in that anhydrite and dolomite are scarce in the lower Arab Formation units and recognition of any sequence stratigraphic boundaries is limited. In summary the limestone-dominated reservoir units combine to reflect a large-scale shallowing-upwards trend from basinal/outer, mid-ramp to inner ramp depositional settings, based on core-derived facies association analysis. The facies associations are defined according to sedimentological and faunal characteristics and form genetically related, larger-scale units reflecting a low-energy, mid to outer ramp depositional setting, which grades sharply into an inner ramp shoal and shoal complex depositional setting. Within the low-energy units of the lowest Arab Formation reservoir, mudstones are interbedded with bioclast-rich accumulations of variable thickness and an uncertain origin. The vertical spacing of these units may be a function of random/non-random cyclicity (?Milankovitch) and reflect variation in depositional slope angle and hence slump/debrite deposits or deeper water faunal communities. The transition from the distal depositional setting to the proximal depositional setting occurs over a relatively narrow zone into oolitic grainstones as the system progrades. The grainstones form a thick sequence of bedded units reflecting both shoal and intershoal areas within an inner ramp depositional setting, but cyclicity is not apparent in this interval. The small-scale cyclicity present in the lower Arab Formation units may potentially be equal to those that are defined by dolomite-anhydrite cycles in Qatar, but in this area of Abu Dhabi, the overall distal setting has negated the development of these mixed evaporite-carbonate cycles. The implications of this include a lack of intraformational seals and a uniformity of lithofacies (i.e. limited variation), which is also expressed in the more proximal inner ramp deposits and provides for good reservoir potential.
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Termination of the Gotnia Salt and its Effects on the Petroleum System of the Partitioned Zone, Saudi Arabia and Kuwait
Authors R.A. Corley, M. Ye and S. KumarThe Partitioned Zone is an area located along the southern border of the State of Kuwait and the northeastern portion of the Kingdom of Saudi Arabia. The Gotnia Formation of Late Kimmeridgian to Early Tithonian age lies unconformable below Sulaiy/Makhul formations and conformable above the Jubaila Formation, within the Partitioned Zone. Gotnia age-equivalent formations, on the Arabian Platform, include the Arab-Hith formations of Saudi Arabia, Qatar and United Arab Emirates. The Gotnia Formation extends from southern Iraq through Kuwait reaching a maximum thickness of approximately 1,500 feet in southern Kuwait. The termination of the Gotnia Formation is approximately 50 km south of its recorded maximum thickness. Terminus of the Gotnia Formation is mappable and extends in an east-west direction through the Partitioned Zone. Extensive 3-D and 2-D seismic coverage allows detailed identification of the southern pinch-out of the Gotnia Formation. Subsurface control is also aided by several deep wells on either side of the Gotnia pinch-out. This effort will demonstrate and define the structural and stratigraphic nature of the Gotnia Formation’s southern terminus and its effect on the petroleum system within the Partitioned Zone. No full paper available.
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Regional Settings and Characteristics of an Oxfordian Hot Shale
Authors M.C. Poppelreiter, W. Kolkmann, H. Hordijk and M. StevanovichDevelopment of predictive geological rules is vital for successful exploration and development. The “sweet spotting” concept is widely used to predict areas with better-than-average porosity and permeability. However the definition of sweet spots in unconventional plays is still an emerging concept. Empirical observations from a decade of unconventional development in North America suggest better-than-average production is governed by a combination of favorable matrix permeability, presence of natural fractures and source-rock richness and maturity.
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Sequence Stratigraphy and Sedimentology of the Upper Jurassic Arab and Hith Formations, Abu Dhabi, United Arab Emirates
Authors A. Al-Mansoori and C. J. StrohmengerThe Kimmeridgian–Tithonian Arab and Hith formations are part of the highstand sequence set of a second-order supersequence, built by five third-order composite sequences: (1) J70 Sequence, Jubaila/ Arab-D; (2) J80 Sequence, Arab-C; (3) J90 Sequence, Arab-B; (4) J100 Sequence, Arab-A/Lower Asab Oolite; and (5) J105 Sequence, Upper Asab Oolite/Hith), bounded on top by sequence boundary J110_ SB. The J70 to J105 sequences belong to the highstand sequence set of the Upper Jurassic second-order supersequence and show progradation of the facies belts towards the east. Through time, the lagoon behind the barrier bar complex became increasingly evaporitic being dominated by salina-type deposits during Hith deposition (J105 Sequence).
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Use of Surface Analogue for 3-D Geological Modelling of the Arab D Reservoirs - Example from Jabaloyas Outcrops (Eastern Spain)
Authors B.P.R Caline, C. Pabian-Goyheneche, J.P. Rolando, G. San Miguel, M. Aurell, B. Badenas, N. Grasseau and V. MartinezThe poster illustrates how an Upper Kimmeridgian analogue exposed in NE Spain has been used to characterise the internal heterogeneities of a low-angle carbonate ramp that includes the development of reef build-ups formed by colonial forms (corals, stromatoporoids), and microbial crusts with associated encrusting organisms. Results from this outcrop analogue have been applied for improving oil recovery from the Arab D reservoirs of a mature field in UAE. The well-exposed outcrops around the Jabaloyas village (Eastern Spain) have been used for detailed facies and sequence stratigraphic reconstructions within a 16–22 m thick series. These outcrops show strike and non-strike sections across a 12 km2 area (i.e. 4 x 3 km). Seventeen stratigraphic profiles were carried out to control vertical and lateral facies distribution. The facies follows an overall retrogradational-progradational trend with the development of low-energy peloidal-skeletal wackestone-packstone in the middle part of the sequence. Different types of grain-supported facies (ooidal, peloidal, intraclastic, skeletal) are found both in high-energy mid-ramp domains and inner ramp areas. The studied series is bounded by discontinuities that are traceable across a total of 17.5 km linear distance and encompasses coral-microbial build-ups 5 to 15 m high developed in mid-ramp setting during the stages of maximum accommodation gain. A total of 274 reefs have been mapped across the different reconstructed 2D transects. Most of them have pinnacle or conical geometry. Well-cemented discontinuity surfaces were used to identify four stages of sedimentary evolution, two of them including individual episode of reef growth. Some trends on the spatial density and on the fabric within each stage have been recorded. The overall distribution of the main facies were included in a full-field model (20 x 20 m grid increment) while the geometry, size and distribution of the reefs were better adjusted in sector models (1 x 1 m). These models assess the distribution of reservoir bodies and their connectivity. They are now used as a template for diagenesis modelling and constitute the geological input for simulation models.
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Hydrocarbon Prospectivity of the Late Jurassic – Early Cretaceous Makhul Formation in North and Northwestern Kuwait
Authors R.T. Arasu, S.K. Singh, T.F. Al-Adwani, B.Z. Khan, J. Macadan and A.F.N. Abu-GhaneejThe Makhul Formation is the lowermost sequence of Tammama Group in Kuwait sub-basin, deposited during late Tithonian to early Beriasian age. The formation is dominantly argillaceous mudstone with packstone and rare wackestone. In the northern parts of Kuwait the lower Makhul is depicted in the 2D/3D seismic as prograding reflection package, downlaping onto the Hith Formation top. The upper Makhul section has parallel to sub-parallel reflection pattern in the area. The acoustic impedance of the lower Makhul is very low, comparable to shale impedance and grading to relatively higher impedance towards top. That the tight reservoirs of the Makhul Formation have hydrocarbon potential is proven. Fractures are present in the Makhul rocks as seen in the available core data and image logs. They may play vital role for the sustainable production from these unconventional reservoirs. 3D Seismic based high resolution edge mapping has brought out near evenly spaced sub-vertical discontinuities. The wells that have intersected discontinuities gave high gas readings in the mud log. Low frequency anomalies could be indicators of hydrocarbon/fractures. The challenge is to understand the trapping mechanism and geomechanical properties and to identify ‘sweet spots’ for commercial success.
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3-D Carbonate Seismic Stratigraphy of the Berriasian–Valanginian Minagish Field Region, Kuwait
Authors M. Al-Baghli and J.D. PigottMuch previous exploration in the Minagish Field of Kuwait has concentrated upon prospectivity of the principle structures facilitated by 3-D seismic with much less attention directed toward stratigraphic studies. Therefore, questions concerning the seismic imagery of carbonate reservoir quality and seal potential owing to facies changes accompanying allocyclic (global tectono-eustatic) and autocyclic (depositional) processes with a paragenetic overprint (diagenetic-fracture history) have been only modestly studied. The focus of this investigation is upon the carbonate seismic facies placed within a sequence-stratigraphic framework.
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Reconstruction of Late Jurassic Oolite Shoal Paleoenvironments in a Giant Gas Field, Onshore United Arab Emirates
Authors D.A. Lawrence, F. Al Darmaki, D. Green, Y. Bouzida and G. PopaThe Late Jurassic Arab Formation is being developed in a major gas accumulation located onshore southern UAE. The reservoir intervals form a large scale shallowing-upward cycle capped by the widespread Hith anhydrite topseal. The lower Arab Formation consists of wackestones to mudstones of mid ramp to basinal setting (Arab D Member) overlain by foreshoal and oolitic grainstone shoal deposit of the Arab C Member. The succeeding Upper Arab (A & B Members) comprises alternations of dolomitic limestone and anhydrite of restricted lagoon to backshoal and sabkha / salina origin.
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Re-evaluation of the Late Jurassic to Early Cretaceous Stratigraphy of Abu Dhabi
Authors V. Vahrenkamp, P. Van Laer, K. Leyrer, D. Popa, F. Al Katheeri, P. Razin and C. GrelaudThe Late Jurassic to Early Cretaceous sequences of the Arabian Platform form a key petroleum province with super-giant carbonate reservoirs. Despite this economic importance and an excellent database the stratigraphy still contains ambiguities with possible alternative interpretations of far-reaching implications.
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From Geochemistry to Stratigraphy: Unraveling the History of Three Oil Machines in Kuwait
Authors R. Andriany, A. Al-Khamiss and G. Al-SahlanThe application of biological markers (biomarkers) as geochemical fossils for exploration, development, and production purposes is growing rapidly. Their ability to retain the chemical structures during geological processes has been utilized to differentiate among three main source-rock intervals from Late Jurassic to Early Cretaceous. Two source-rock intervals, the Oxfordian Najmah and Berriasian Makhul formations, have been recognized as two giant oil machines. The presence of a fine-grained interval in the Hith Formation opens a new target for exploration.
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