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  • 1.
    Abdelmaksoud, Ahmed
    et al.
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates.;Assiut Univ, Dept Geol, Assiut, Egypt..
    Ali, Mohammed Y.
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Al Suwaidi, Aisha
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Petroleum system of the fold-and-thrust belt of the United Arab Emirates: New insights based on 1D and 2D basin modeling2023In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 158, article id 106567Article in journal (Refereed)
    Abstract [en]

    The hydrocarbon potential of the fold-and-thrust belt (FTB) in the United Arab Emirates (UAE)-Oman mountains has received limited attention to date, leading to a poor understanding of the petroleum systems in this region. Despite the existence of hydrocarbon fields within the FTB, the source rock potential has not been adequately studied. This study aims to address this knowledge gap using 1D and 2D basin modeling approaches to evaluate the petroleum system of the FTB. In addition, gas chromatographs are also used to correlate hydrocarbon occurrences with their source rock. This study's findings identify the Silurian, Upper Cretaceous, Paleocene-Eocene, and Oligocene formations as the primary source rocks in the study area. Silurian shales, encountered in a well in the northern UAE, are currently considered overmature. The Cenozoic source rocks exhibit a spectrum of Total Organic Carbon (TOC) content, ranging from less than 1 to as high as 2 wt%, leading to variable degrees of expulsion efficiency. The maturity of these rocks varies based on their position in relation to the FTB and foredeep, with increasing maturity towards the north. The Upper Cretaceous sequences display low TOC and Hydrogen Index, indicating very low expulsion efficiency. The present-day distribution of maturity is largely influenced by Late Cretaceous and Oligocene-Miocene compressional events that affected the northern and northeastern Arabian Plate. This analysis shows that hydrocarbon expulsion from the Silurian source rocks was initiated during the Middle-Late Jurassic. These hydrocarbons are presumed to have migrated through Upper Permian, Jurassic, and Lower and middle Cretaceous reservoirs. Westward hydrocarbon migration, towards a regional bulge, may have also occurred following compressional events that resulted in lithospheric flexure and formation of the foreland basin. Notably, certain exceptions to migration towards the bulge include structural entrapment of hydrocarbons beneath the main frontal thrust zone of FTB and some structural traps beneath the Lower Fiqa Formation.

  • 2.
    Ali Kalefa El-ghali, Mohamed
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Morad, Sadoon
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Mansurbeg, Howri
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Caja, Miguel A.
    Sirat, M.
    Ogle, N.
    Diagenetic alterations related to marine transgression and regression in fluvial deltaic and shallow marine sandstones of the Triassic Buntsandstein and Keuper formations, the Paris Basin, France2009In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 26, no 3, p. 289-309Article in journal (Refereed)
    Abstract [en]

    The distribution of diagenetic alterations in Triassic fluvio-deltaic, quartzarenitic to sublitharenitic, lowstand systems tract (LST) sandstones of the Grès á Voltzia Formation, anastomosing fluvial, quartzarenitic transgressive systems tract (TST) sandstones of the Grès á Roseaux Formation, and shallow marine, quartzarenitic to sublitharenitic, TST sandstones of the Grès Coquiller Formation, the Paris Basin (France), can be linked to transgression and regression events, and thus to the sequence stratigraphic context. Near-surface eogenetic alterations, which display a fairly systematic link to the depositional facies and sequence stratigraphic framework, include: (i) cementation by meteoric water calcite (δ18O=−8.9‰ and δ13C=−9.1‰) in the fluvio-deltaic, LST sandstones, (ii) cementation by mixed marine–meteoric calcite (δ18O=−5.3‰ to −2.6‰ and δ13C=−3.9‰ to −1.3‰) and dolomite (δ18O=−4.6‰ to −2.6‰ and δ13C=−2.9‰ to −2.3‰) in the foreshore, TST sandstones and below parasequence boundaries (PB), and transgressive surface (TS), and in the shoreface, TST sandstones below maximum flooding surfaces (MFS), being facilitated by the presence of carbonate bioclasts, (iii) dissolution of detrital silicates and precipitation of K-feldspar overgrowths and kaolinite, particularly in the fluvio-deltaic, LST sandstones owing to effective meteoric water circulation, and (vi) formation of autochthonous glauconite, which is increases in abundance towards the top of the fluvio-deltaic, LST sandstones, and along TS, and in the shoreface, TST sandstones, by alteration of micas owing to the flux of seawaters into the sandstones during transgression, whereas parautochthonous glauconite is restricted to the TS sandstones owing to marine reworking. Mesogenetic alterations, which include cementation by quartz overgrowths and illite, display fairly systematic link to fluvio-deltaic, LST sandstones. This study has revealed that linking of diagenesis to transgression and regression events enables a better understanding of the parameters that control the spatial and temporal distribution of diagenetic alterations in sandstones and of their impact on reservoir quality evolution.

  • 3.
    Carrillo, Emilio
    et al.
    Univ Barcelona, Dept Geoquim Petr & Prospeccio Geol, C Marti & Franques S-N, E-08028 Barcelona, Spain.;Yachay Tech Univ, Sch Geol Sci & Engn, Hacienda San Jose S-N, San Miguel De Urcuqui, Ecuador..
    Koyi, Hemin A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Nilforoushan, Faramarz
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Univ Gavle, Dept Ind Dev IT & Land Management, Gavle, Sweden.;Lantmateriet, Gavle, Sweden..
    Structural significance of an evaporite formation with lateral stratigraphic heterogeneities (Southeastern Pyrenean Basin, NE Spain)2017In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 86, p. 1310-1326Article in journal (Refereed)
    Abstract [en]

    We run a series of analogue models to study the effect of stratigraphic heterogeneities of an evaporite formation on thin-skinned deformation of the Southeastern Pyrenean Basin (SPB; NE Spain). This basin is characterized by the existence of evaporites, deposited during the Early-Middle Eocene with lateral variations in thickness and lithological composition. These evaporites are distributed in three lithostratigraphic units, known as Serrat Evaporites, Vallfogona and Beuda Gypsum formations and acted as decollement levels, during compressional deformation in the Lutetian. In addition to analogue modeling, we have used field data, detailed geological mapping and key cross-sections supported by seismic and well data to build a new structural interpretation for the SPB. In this interpretation, it is recognized that the basal and upper parts of the Serrat Evaporites acted as the main decollement levels of the so-called Cadi thrust sheet and Serrat unit. A balanced restoration of the basin indicates that thrust faults nucleated at the stratigraphic transition of the Serrat Evaporites (zone with lateral variations of thickness and lithological composition), characterized by a wedge of anhydrite and shale. The analogue models were setup based on information extracted from cross-sections, built in two sectors with different lithology and stratigraphy of the evaporites, and the restored section of the SPB. In these models, deformation preferentially concentrated in areas where thickness change, defined by wedges of the ductile materials, was inbuilt. Based on the structural interpretation and model results, a kinematic evolution of the SPB is proposed. The kinematic model is characterized by the generation of out-of-sequence structures developed due to lateral stratigraphic variations of the Serrat Evaporites. The present work shows a good example of the role of stratigraphic heterogeneities of an evaporite formation which acts as decollement level on structural deformation in a fold-thrust belt. The results of this work have implications for hydrocarbon exploration and are relevant for studying structural geometry and mechanics in shortened evaporite basins. (C) 2017 Elsevier Ltd. All rights reserved.

  • 4. Delle Piane, Claudio
    et al.
    Almqvist, Bjarne
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    MacRae, Colin
    Torpy, Aaron
    Mory, Arthur
    Dewhurst, David
    Texture and diagenesis of Ordovician shale from the Canning Basin, Western Australia: implications for elastic anisotropy and geomechanical properties2015In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 59, p. 56-71Article in journal (Refereed)
  • 5. El-Ghali, M. A. K.
    et al.
    El Khoriby, E.
    Mansurbeg, H.
    Morad, Sadoon
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ogle, N.
    Distribution of carbonate cements within depositional facies and sequence stratigraphic framework of shoreface and deltaic arenites, Lower Miocene, the Gulf of Suez rift, Egypt2013In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 45, p. 267-280Article in journal (Refereed)
    Abstract [en]

    This study aims to unravel the spatial and temporal distribution of diagenetic alterations of the Mheiherrat Member, the Rudeis Formation (lower Miocene) of the Gulf of Suez rift, Egypt within depositional fades and sequence stratigraphy. The Mheiherrat member is represented by shoreface calcarenites and hybrid arenites (transgressive and highstand systems tracts; TST and HST; respectively) and deltaic rudites and coarse-grained calcarenites and hybrid arenites (lowstand systems tracts; LST). Petrographic, stable O- and C-isotopes, mineral chemical and geochemical analyses have revealed that the arenites are pervasively cemented by eogenetic carbonates and, to small extent, by zeolite and pyrite as well as by telogenetic palygorskite. The shoreface TST and HST calcarenites and hybrid arenites were dominantly cemented by microcrystalline grain-rimming and inter- and intragranular pore-filling calcite (delta O-13(V-PDB) = -3.6 parts per thousand to -0.3 parts per thousand and delta C-13(V-PDB) = -2.3 parts per thousand to -0.7 parts per thousand) and rhombic dolomite (delta C-13(V-PDB) = -3.9 parts per thousand to +0.9 parts per thousand and delta C-13(V-PDB) = -2.5 parts per thousand to -0.7 parts per thousand). These cements are interpreted to be formed by marine to brackish waters with delta O-13(V-SMOW) -1.2 parts per thousand to +3.2 parts per thousand, at temperature of 20-55 degrees C. The deltaic LST coarse-grained calcarenites and hybrid arenites were dominantly cemented by coarse-crystalline, inter- and intragranular pore-filling calcite (delta O-13(V-PDB) -4.4 parts per thousand to -2.3% and delta C-13(V-PDB) = -2.8 parts per thousand. to -1.3 parts per thousand.), which are interpreted to have precipitated from pore waters with delta O-13(V-SWOM) +3.5 parts per thousand. to +5.5 parts per thousand, at temperatures of greater than 55 degrees C. Such pervasive cementation by carbonates is attributed to the occurrence of abundant intrabasinal carbonate grains. The carbonate cement texture is suggested to be controlled by changes in pore-water chemistry owing to transgression and regression events. This case study revealed that better understanding of factors controlling the extent and textural habits of carbonate cements can be achieved when it is linked with depositional facies and sequence stratigraphy.

  • 6.
    El-Ghali, Mohamed Ali Kalefa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Morad, Sadoon
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Mansurbeg, Howri
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Caja, Miguel Angel
    Ajdanlijsky, George
    Ogle, Neil
    Al-Aasm, Ihsan
    Sirat, Manhal
    Distribution of diagenetic alterations in  within depositional facies and sequence stratigraphic framework of  fluvial sandstones: Evidence from the Petrohan Terrigenous Group, Lower Triassic, NW Bulgaria2009In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 26, no 7, p. 1212-1227Article in journal (Refereed)
    Abstract [en]

    Sequence stratigraphy of fluvial deposits is a controversial topic because changes in relative sea level will eventually have indirect impact on the spatial and temporal distribution of depositional facies. Changes in the relative sea level may influence the accommodation space in fluvial plains, and hence have impact on types of fluvial system, frequency of avulsion, and style of vertical and lateral accretion. This study aims to investigate whether depositional facies and changes in the fluvial system of the Lower Triassic Petrohan Terrigenous Group sandstones (NW Bulgaria) in response to changes in the relative sea level have an impact on the spatial and temporal distribution of diagenetic alterations. Eogenetic alterations, which were encountered in the fluvial sandstones, include: (i) mechanically Infiltrated clays, particularly in channel and crevasse splay sandstones towards the top of the owstand systems tract (LST) and the base of the highstand systems tract (HST). (ii) Pseudomatrix, which resulted from mechanical compaction of mud intraclasts, occurs mainly in channel sandstones at the base of the LST and towards the top of the HST and thus led to porosity and permeability deterioration. (iii) Calcite (delta O-18(VPDB)= -8.1 parts per thousand to -7.5 parts per thousand and delta C-13(VPDB) = -7.87 parts per thousand to -6.3 parts per thousand) and dolomite (delta O-18(VPDB) = -8.3 parts per thousand to -5.2 parts per thousand and delta 13C(VPDB) = -8.3 parts per thousand to -7.1 parts per thousand), which are associated with palaeosol horizons developed on top of crevasse splay and channel sandstones of transgressive systems tract (TST) and LST: Such extensive eogenetic calcite cements may act as potential layers for the formation of reservoir compartments for underlying sandstones. Mesogenetic alterations include: (i) calcite (delta O-18(VPDB) = -18.4 parts per thousand to -12.8 parts per thousand and delta C-13(VPDB) = -8.6 parts per thousand to -6.8 parts per thousand) and dolomite (delta O-18(VPDB) = -14.7 parts per thousand to - 12.4 parts per thousand and delta C-13(VPDB) = -8.0 parts per thousand to -7.0 parts per thousand), which were formed in all depositional facies and systems tract´sandstones, (ii) illite, which is the dominant diagenetic clay mineral in all depositional facies and systems tracts, was associated with albitization of detrital K-feldspars, and (iii) quartz overgrowths, which are most abundant in TST rather than LST and HST sandstones, because of the presence of suitable infiltrated clays and pseudomatrix in the latter sandstones. Such cementation by calcite, dolomite, and quartz overgrowths and formation of illite led to porosity and permeability deterioration during mesodiagenesis. The results of this study revealed the importance of integration of diagenesis with depositional facies and sequence stratigraphy of fluvial sandstones in improving our ability to predict the spatial and temporal distribution of eogenetic alterations and their subsequent impact on mesogenetic alterations, and thus on reservoir quality modifications.

  • 7.
    El-ghali, Mohamed
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Tajori, Karima
    Mansurbeg, Howri
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ogle, N.
    Kalin, R.M.
    Origin and timing of siderite cementation in Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya2006In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 23, no 4, p. 459-471Article in journal (Refereed)
    Abstract [en]

    The origin and timing of siderite cementation have been constrained in relation to depositional facies and sequence stratigraphy of Upper Ordovician glaciogenic sandstones from the Murzuq basin, SW Libya. Optical microscope, backscattered electron imagery, and carbon and oxygen stable isotope analysis have revealed that siderite is of eo- and mesogenetic origin. Eogenetic siderite is Mg-poor with a mean composition Of (Fe91.7Mg1.5Ca0.3Mn6.5)CO3, and occurs in paraglacial, tide-dominated deltaic highstand systems tract (HST) sandstones, in paraglacial, foreshore to shoreface HST sandstones and in postglacial, Gilbert-type deltaic lowstand systems tract (LST) sandstones. This siderite is typically of meteoric water origin that influxed into the LST and HST sandstones during relative sea level fall and basinward shift of the strandline.Mesogenetic siderite, which engulfs and thus postdates quartz overgrowths and illite, is Mg-rich with a mean composition of (Fe72.2Mg21.7Ca0.8Mn5.3)CO3 and occurs in the paraglacial, tide-dominated deltaic HST sandstones, in paraglacial foreshore to shoreface HST sandstones, in glacial, tide-dominated estuarine transgressive systems tract (TST) sandstones, in postglacial, Gilbert-type deltaic LST sandstones, and in postglacial, shoreface TST sandstones. delta O-18(V-PDB) values of this siderite, which range between -22.6 and -13.8 parts per thousand, suggest that precipitation has occurred from evolved formation waters with delta O-18 values between -14.0 and +1.0 parts per thousand and was either meteoric, mixed marine-meteoric and/or marine in origin by assuming postdating quartz overgrowths and illite temperature between 80 and 130 degrees C.

  • 8.
    Höök, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Global Energy Systems.
    Bardi, Ugo
    University of Firenze.
    Feng, Lianyong
    China University of Petroleum - Beijing.
    Pang, Xiongqi
    China University of Petroleum - Beijing.
    Development of oil formation theories and their importance for peak oil2010In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 27, no 9, p. 1995-2004Article in journal (Refereed)
    Abstract [en]

    This paper reviews the historical development of both biogenic and non-biogenic petroleum formation. It also examines the recent claim that the so-called “abiotic” oil formation theory undermines the concept of “peak oil,” i.e. the notion that world oil production is destined to reach a maximum that will be followed by an irreversible decline. We show that peak oil is first and foremost a matter of production flows. Consequently, the mechanism of oil formation does not strongly affect depletion. We would need to revise the theory beyond peak oil only for the extreme — and unlikely — hypothesis of abiotic petroleum formation.

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  • 9.
    Jia, Yunzhong
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Chongqing Univ, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China..
    Tang, Jiren
    Chongqing Univ, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China..
    Lu, Yiyu
    Chongqing Univ, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China..
    Lu, Zhaohui
    Chongqing Inst Geol & Mineral Resources, Key Lab Shale Gas Explorat, Minist Nat Resources, Chongqing 401120, Peoples R China..
    Laboratory geomechanical and petrophysical characterization of Longmaxi shale properties in Lower Silurian Formation, China2021In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 124, article id 104800Article in journal (Refereed)
    Abstract [en]

    The Lower Silurian Longmaxi formation is one of the most promising shale gas reservoirs in China. A comprehensive understanding of the shale geomechanical and petrophysical properties is crucial for the successful exploration and extraction of shale gas. We select four representative locations to acquire Longmaxi formation shale samples for the laboratory experiments, to investigate the geomechanical and petrophysical properties through a series of X-ray diffraction (XRD), scanning electron microscope (SEM), uniaxial compression, triaxial compression, tensile strength, and fracture toughness measurements. Laboratory results indicate that: (1) The quartz is the dominant mineral, and phyllosilicate mineral contents vary largelly from 7.30% to 47.80% in Longmaxi shale, which enables a higher brittleness index and fracbility. SEM results show that the high gas storage potential and well micro-fractures development of Longmaxi shale rocks. (2) The phyllosilicate content is vital in determining the uniaxial compressive strength, triaxial strength and elastic properties due to its weaker mechanical properties than tectosilicate minerals; (3) Fracture toughness of Longmaxi shale are relatively higher than shale formations in the USA, which indicate a higher potential to form fracture networks during hydraulic fracturing operations. (4) The anisotropy affects Longmaxi shale mechanical properities extensively due to the high-density bedding planes, which may further influence the fracture network formation during hydraulic fracturing operations. Our results revealed significant non-linear mechanical response as a consequence of shale fabric and mineralogy, which provides necessary information for the in-situ hydraulic fracturing and wellbore stability application during shale gas development in Longmaxi shale formation.

  • 10.
    Khalifa, Muftah
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Morad, Sadoon
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Impact of structural setting on diagenesis of fluvial and tidal sandstones: The Bahi Formation, Upper Cretaceous, NW Sirt Basin, North Central Libya2012In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 38, no 1, p. 211-231Article in journal (Refereed)
    Abstract [en]

    This petrographic, mineral chemical, fluid inclusion, and stable isotopic study shows that the distribution of diagenetic modifications and their influence on reservoir quality and heterogeneity in tidal and fluvial sandstones of the Upper Cretaceous Bahi Sandstones in the rift Sirt Basin, NW Libya varies systematically along a series of closely-spaced, dominantly normal faults between the basin margin and more basinward-located areas. Shallow eogenetic modifications resulting from the percolation of meteoric waters, include infiltration of grain coating clays, kaolinitization of detrital silicates, and cementation by dolomite and K-feldspar overgrowths. Mesogenetic alterations (>70 °C, >2 km) include feldspar albitization, illitization of infiltrated clay and kaolinite, conversion of kaolinite into dickite, and cementation by quartz overgrowths (T h 112 °C-134 °C), barite (T h 145 °C-158 °C) and Fe-carbonates. The restriction of barite and Fe-carbonate cements to the basinward-located sandstones suggests formation by hydrothermal fluids along the faults. Extensive feldspar dissolution and formation of moldic pores in sandstones from the basin margin were probably caused by deep percolation of meteoric waters. Results from this study regarding the structural control on the spatial distribution of diagenetic alterations have implications for constraining the flux of pore fluids and, by extension, reservoir quality in analogous epicratonic rift basins.

  • 11.
    Kordi, Masoumeh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Turner, Brian
    Salem, Alaa M. K.
    Linking diagenesis to sequence stratigraphy in fluvial and shallow marine sandstones: Evidence from the Cambrian-Ordovician lower sandstone unit in southwestern Sinai, Egypt2011In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 28, no 8, p. 1554-1571Article in journal (Refereed)
    Abstract [en]

    By integrating diagenesis and sequence stratigraphy, the distribution of diagenetic alterations and their impact on reservoir quality was investigated within a sequence stratigraphic framework using the fluvial and shallow marine sandstones in the Cambrian-Ordovician succession of southwest Sinai. The pero-graphic and geochemical analysis of the studied sandstone revealed that the eogenetic alterations display fairly systematic spatial and temporal distribution patterns within the lowstand system tract and transgressive system tract, as well as along the sequence stratigraphic surfaces (i.e., sequence boundaries, transgressive surfaces and parasequence boundaries). During relative sea-level fall, percolation of meteoric waters through sandstones of the LST and below sequence and parasequence boundaries resulted in extensive dissolution of detrital grains and formation of kaolinite, authigenic K-feldspar and feldspar overgrowths as well as formation of mechanical infiltrated clays around the detrital grains. During relative sea-level rise, invasion of marine water into the sandstones as a consequence of landward migration of the shoreline, as well as low sedimentation rates encountered in the TST, resulted in the formation of glauconite, apatite and pyrite. Development of pseudomatrix, which was formed by mechanical compaction of mud intraclasts, is mostly abundant along transgressive surfaces and parasequence boundaries of the TST, and is related to the abundance of mud intraclasts in the transgressive lag deposits. The types and extent of eogenetic alterations have an important impact on the distribution of the mesogenetic alterations, including the formation of quartz overgrowths and dickite. Distribution of mesogenetic quartz overgrowths in the sandstones was controlled by the distribution of mechanically infiltrated clays and the presence of eogenetic cement. Sandstones that remained poorly cemented during eodiagenesis and that have thin or discontinuous infiltrated clay rims around the detrital grains were cemented during mesodiagenesis by quartz. The absence of extensive eogenetic cements in the sandstones suggested that the partial deterioration of porosity was mainly due to mechanical compaction. Partial transformation of kaolinite to dickite, which indicates neomorphic change to a better-ordered and more stable crystal structure at the elevated temperatures during mesodiagenesis, is partially a function of distribution of kaolinite during eodiagenesis. The conceptual model developed in this study shows the diagenetic evolutionary pathways in the reservoir sandstones within a sequence stratigraphic context, which in turn provides some insights into the controls on reservoir heterogeneity.

  • 12.
    Koyi, Hemin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Petersen, K.
    Geologisk Institut, Aarhus University, Århus, Denmark.
    The influence of basement fault on the development of salt structures in the Danish Basin.1993In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 10, no 2, p. 82-94Article in journal (Refereed)
    Abstract [en]

    Scaled centrifuged models based on interpreted seismic profiles were used to simulate the salt structures in the Danish Basin. The models consisted of a viscous layer simulating rock salt, overlain by layers of cohesive sand that mimic brittle failure in natural overburdens. Model results support the hypothesis that basement faults trigger the growth of many salt diapirs in the Danish Basin. In plan view, model diapirs are localized as buoyant walls along faults in the overburden which collapsed due to basement fault movement. With further burial, single diapirs rose from these buoyant walls. Some of the diapirs surfaced through the faulted overburden, a few were trapped beneath the competent ‘Cretaceous’ units and others were starved due to lack of supply from below. In section, model diapirs were asymmetric and were rooted on the tip of the faults or located on the rotated footwall blocks. Model diapirs not located over faults were triggered by differential loading and collapsing of overburden layers due to basement block rotation. Models show that the presence of fewer salt structures in the northern than the southern part of the basin is due to differential subsidence and flow of buoyant material from north to south, where they rise diapirically. In the model, the pressure due to loading by overburden layers changed from 1.3 × 102 Pa in the south to 2.3 × 102 Pa in the northern part of the basin. In general, the model results illustrate that basement faults influence diapirs by accumulating buoyant material in half-grabens and introducing a slope and steps at the base of the buoyant layer, weakening its overburden and causing differential loading and compaction. The spreading overhangs of salt diapirs beneath the Cretaceous chalk in the Danish Basin would seal any potential pre-Cretaceous reservoir rocks.

  • 13. Mansurbeg, Howri
    et al.
    De Ros, L. F.
    Morad, Sadoon
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ketzer, J. M.
    El-Ghali, M. A. K.
    Caja, M. A.
    Othman, R.
    Meteoric-water diagenesis in late Cretaceous canyon-fill turbidite reservoirs from the Espirito Santo Basin, eastern Brazil2012In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 37, no 1, p. 7-26Article in journal (Refereed)
    Abstract [en]

    Parameters controlling the diagenetic evolution of passive margin, marine turbidites, which are important targets of hydrocarbon exploration, are poorly constrained in the literature. This study aims to unravel the conditions of diagenesis and its impact on the reservoir quality evolution from late Cretaceous canyon-filling turbiditic sandstones of the onshore portion of Espirito Santo Basin, eastern Brazil. Kaolinization (delta O-18 = +13.3 parts per thousand to +15.2 parts per thousand; delta D = 96.6 parts per thousand to -79.6 parts per thousand) and dissolution of framework silicate grains is attributed to meteoric water incursion during eodiagenesis in response to a considerable fall in relative sea-level. Eogenetic alterations also include cementation by siderite (average delta O-18 = -72 parts per thousand; delta C-13 = +9.3 parts per thousand) and pyrite. Progressive sediment burial (present depths = 1530-2027 m) resulted in the formation of poikilotopic calcite, ferroan dolomite-ankerite (average delta O-18 = -7.9 parts per thousand; delta C-13 = +2.9 parts per thousand), minor amounts of quartz overgrowths and in partial dickitization of kaolinite. Isotopic values of calcite and dolomite-ankerite follow two trends of co-variance of delta C-13 with decreasing delta O-18 and increasing temperature. From a composition closer to marine (approximate to 0 parts per thousand), one trend goes towards positive delta C-13 values (up to +22.4 parts per thousand for calcite; +18.6 parts per thousand for dolomite-ankerite), indicating increasing input of carbonate from methanogenic fermentation. The other trend develops towards negative delta C-13 values (down to -17.2 parts per thousand for calcite; 15 parts per thousand for dolomite-ankerite), suggesting increasing contribution from thermal decarboxylation with increasing temperature and depth. Despite the presence of various cement types, mechanical compaction was more important than cementation in reducing depositional porosity in the onshore Urucutuca sandstones.

  • 14.
    Mansurbeg, Howri
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Morad, Sadoon
    El-ghali, Mohamed A.K.
    Salem, Alaa
    Nystuen, J-P
    Caja, M.A.
    Marfil, R.
    Garcia, D.
    Amorosi, A.
    Diagenesis and reservoir quality evolution of paleocene deep-water, marine sandstones, the Shetland-Faroes Basin, British Continental Shelf2008In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 25, no 6, p. 514-543Article in journal (Refereed)
    Abstract [en]

    The Palaeocene, deep-water marine sandstones recovered from six wells in the Shetland-Faroes Basin represent lowstand, transgressive and highstand systems tract turbiditic sediments. Mineralogic, petrographic, and geochemical analyses of these siliciclastics are used to decipher and discuss the diagenetic alterations and subsequent reservoir quality evolution. The Middle-Upper Palaeocene sandstones (subarkoses to arkoses) from the Shetland-Faroes Basin, British continental shelf are submarine turbiditic deposits that are cemented predominantly by carbonates, quartz and clay minerals. Carbonate cements (intergranular and grain replacive calcite, siderite, ferroan dolomite and ankerite) are of eogenetic and mesogenetic origins. The eogenetic alterations have been mediated by marine, meteoric and mixed marine/meteoric porewaters and resulted mainly in the precipitation of calcite (δ18OV−PDB=−10.9‰ and −3.8‰), trace amounts of non-ferroan dolomite, siderite (δ18OV−PDB=−14.4‰ to −0.6‰), as well as smectite and kaolinite in the lowstand systems tract (LST) and highstand systems tract (HST) turbiditic sandstone below the sequence boundary. Minor eogenetic siderite has precipitated between expanded and kaolinitized micas, primarily biotite. The mesogenetic alterations are interpreted to have been mediated by evolved marine porewaters and resulted in the precipitation of calcite (δ18OV−PDB=−12.9‰ to −7.8‰) and Fe-dolomite/ankerite (δ18OV−PDB=−12.1‰ to −6.3‰) at temperatures of 50–140 and 60–140 °C, respectively.

    Quartz overgrowths and outgrowth, which post- and pre-date the mesogenetic carbonate cements is more common in the LST and TST of distal turbiditic sandstone. Discrete quartz cement, which is closely associated with illite and chlorite, is the final diagenetic phase. The clay minerals include intergranular and grain replacive eogenetic kaolinite, smectite and mesogenetic illite and chlorite. Kaolinite has been subjected to mesogenetic replacement by dickite. The K-feldspar and plagioclase grains have been albitized. Dissolution of calcite cement and of framework grain (feldspar, volcanic fragments and mud intraclasts) has resulted in a considerable enhancement of reservoir quality.

  • 15.
    Sattar, Nauman
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. ¨.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Ahmad, Nadeem
    United Energy Pakistan, Karachi, Pakistan..
    Seismic stratigraphy and hydrocarbon prospectivity of the Lower, Cretaceous Knurr Sandstone lobes along the southern margin of Loppa High, Hammerfest Basin, Barents Sea2017In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 85, p. 54-69Article, review/survey (Refereed)
    Abstract [en]

    The Lower Cretaceous Knurr Sandstone deposited along the southern slope of Loppa High and overlain by the Kolje and Kolmule seals forms an attractive play in the Hammerfest Basin of the Barents Sea. Late Jurassic organic-rich Hekkingen shale directly underlies the Knurr Sandstone and acts as a source to provide effective charge. Three wells, 7120/2-2, 7122/2-1 and 7120/1-2, have proven the Knurr-Kolje play in structural traps, with an oil discovery in 7120/1-2. Prospectivity related to stratigraphic traps is, however, highly under-explored. In order to document and map the reservoir distribution and stratigraphic-trap fairway, the Lower Cretaceous sedimentary package containing the Knurr Sandstone is divided into a number of depositional sequences and systems tracts using key regional seismic profiles calibrated with logs. Mapping of the key surfaces bounding the Knurr sandstone has been carried out using all the seismic vintages available from Norwegian Petroleum Directorate (NPD).The thick massive nature of the sandstone (123 m in well 7122/2-1), sedimentary features characteristic of gravity flow deposits, high-resolution internal seismic reflections and stratal geometries (truncations and lapout patterns), and sequence stratigraphic position of the Knurr Sandstone on seismic profiles confirm that the lobes identified on the seismic section are gravity driven base of the slope lobes. These Knurr lobes and slope aprons were formed as a result of uplift of the Loppa paleo-high in the Late Jurassic to Early Cretaceous times which caused subaerial exposure and incision. The characteristic mounded, lobate geometry evident on the seismic can be mapped along the toe-of-slope and records multiple stacked lobes fed by multiple feeder canyons. Lateral partitioning and separation of the lobes along the toe-of-slope could potentially create strati graphic traps. The existing 2D seismic coverage is, however, not sufficient to capture lateral stratigraphic heterogeneity to identify stratigraphic traps. 3D seismic coverage with optimum acquisition parameters (high spatial and vertical resolution, appropriate seismic frequency and fold, long offsets and original amplitudes preserved) can allow for the reconstruction of 3D geomorphologic elements to de-risk potential stratigraphic traps prior to exploratory drilling.

  • 16.
    Talbot, Christopher J.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Hydrothermal salt - but how much?2008In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 25, no 2, p. 191-202Article in journal (Refereed)
1 - 16 of 16
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