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  • 1.
    Al-Ramadan, Khalid
    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.
    Norton, A. Kent
    Hulver, Michael
    Linking Diagenesis and Porosity Preservation to Sequence Stratigraphy of Gas Condensate Reservoir Sandstones; the Jauf Formation (Lower to Middle Devonian), Eastern Saudi Arabia2013In: Linking Diagenesis to Sequence Stratigraphy (Special Publication 45 of the IAS) / [ed] Sadoon Morad, Marcelo Ketzer, Luis F. de Ros, John Wiley & Sons, 2013, p. 297-336Chapter in book (Refereed)
  • 2.
    Al-Ramadan, Khalid
    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.
    Proust, Jean-Noel
    Al-Aasm, Ihsan
    Distribution of Diagenetic Alterations in Siliciclastic Shoreface Deposits within a Sequence Stratigraphic Framework: Evidence from the Upper Jurassic, Boulonnais, NW France2005In: Journal of Sedimentary Research, ISSN 1527-1404, E-ISSN 1938-3681, Vol. 75, no 5, p. 943-959Article in journal (Refereed)
    Abstract [en]

    The distribution of diagenetic alterations in Upper Jurassic, siliciclastic shoreface sediments from NW France has been linked to the sequence stratigraphic framework. Calcite cement in mudrocks and sandstones of the transgressive (TST) and lower part of the highstand (HST) systems tracts is microcrystalline and occurs as continuously cemented layers and stratabound concretions. The average δ18OV-PDB (−2.6‰) and 87Sr/86Sr (0.7078) compositions of microcrystalline calcite indicate precipitation from largely marine pore waters.

    Calcite cement in sandstones of the forced regressive wedge (FRWST) and lowstand (LST) systems tracts is poikilotopic and occurs mainly as stratabound concretions. Complete dissolution of the carbonate grains and concomitant precipitation of poikilotopic calcite cement with low average δ18O (−5.3‰) and radiogenic Sr-isotope (0.70882) signatures suggest incursion of meteoric waters into sandstones during relative sea-level lowstand. The poorly lithified sandstones interbedded with sandstones cemented by poikilotopic calcite concretions display evidence of diagenesis under episodes of arid to semiarid paleoclimate, including: (i) partial cementation by opal, chalcedony, gypsum, and minor vadose calcite cement, (ii) mechanically infiltrated clays and Fe-oxides, and (iii) secondary porosity owing to partial dissolution of carbonate grains. The integration of diagenesis into sequence stratigraphy allows better elucidation and prediction of the spatial and temporal distribution of diagenetic alterations and related reservoir-quality modifications in shoreface sediments.

  • 3. Chow, N
    et al.
    Morad, S
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Al-Aasm, I.S
    Geochemical evolution of pore waters and origin of authigenic carbonates in Eocene to Quaternary sediments from the Arctic and Norwegian-Greenland Sea2000In: Journal of Sedimentary Research, Vol. 70, no 3, p. 682-699Article in journal (Refereed)
  • 4.
    De Ros, L.F
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Morad, S
    Broman, C
    De Césero, P
    Gomez-Gras, D
    Influence of uplift and magmatism on distribution of quartz and illite cementation: Evidence from Siluro-Devonian sandstones of the Parana basin, Brazil.2000In: Special Publication, International Association of Sedimentologits, no 29, p. 231-252Article 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.
    Felitsyn, S
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Morad, Sadoon
    Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Solid Earth Geology.
    REE patterns in latest Neoproterozoic-early Cambrian phosphate concretions and associate organic matter2002In: Chem. Geology, Vol. 187, no 3-4, p. 257-265Article in journal (Refereed)
  • 7. Fontana, Simone
    et al.
    Nader, Fadi Henri
    Morad, Sadoon
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ceriani, Andrea
    Al-Aasm, Ihsan Shakir
    Daniel, Jean-Marc
    Mengus, Jean-Marie
    Fluid-rock interactions associated with regional tectonics and basin evolution2014In: Sedimentology, ISSN 0037-0746, E-ISSN 1365-3091, Vol. 61, no 3, p. 660-690Article, review/survey (Refereed)
    Abstract [en]

    An integrated approach consisting of fracture analysis, petrography, carbon, oxygen and strontium-isotope analyses, as well as fluid-inclusion micro-thermometry, led to a better understanding of the evolution of fluid-rock interactions and diagenesis of the Upper Permian to Upper Triassic carbonates of the United Arab Emirates. The deposited carbonates were first marked by extensive early dolomitization. During progressive burial, the carbonates were affected by dolomite recrystallization as well as precipitation of vug and fracture-filling dolomite, quartz and calcite cements. After considerable burial during the Middle Cretaceous, sub-vertical north-south oriented fractures (F1) were cemented by dolomite derived from mesosaline to hypersaline fluids. Upon the Late Cretaceous maximum burial and ophiolite obduction, sub-vertical east-west fractures (F2) were cemented by dolomite (Dc2) and saddle dolomite (Ds) derived from hot, highly saline fluids. Then, minor quartz cement has precipitated in fractures from hydrothermal brines. Fluid-inclusion analyses of the various diagenetic phases imply the involvement of increasingly hot (200 degrees C) saline brines (20 to 23% NaCl eq.). Through one-dimensional burial history numerical modelling, the maximum temperatures reached by the studied rocks are estimated to be in the range of 160 to 200 degrees C. Tectonically-driven flux of hot fluids and associated diagenetic products are interpreted to have initiated during the Late Cretaceous maximum burial and lasted until the Oligocene-Miocene compressional tectonics and related uplift. The circulation of such hydrothermal brines led to partial dissolution of dolomites (Dc2 and Ds) and to precipitation of hydrothermal calcite C1 in new (mainly oriented north-south; F3) and pre-existing, reactivated fractures. The integration of the obtained data confirms that the diagenetic evolution was controlled primarily by the interplay of the burial thermal evolution of the basin and the regional tectonic history. Hence, this contribution highlights the impacts of regional tectonics and basin history on diagenetic processes, which may subsequently affect reservoir properties.

  • 8. Ketzer, J.M
    et al.
    Morad, Sadoon
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. Solid Earth Geology.
    Predictive distribution of shallow-marine, low-porosity (pseudomatrix-rich) sandstones in a sequence stratigraphic framework- example from the Ferron Sandstone, Upper Cretaceous, USA2005In: Marine and Petroleum Geology, Vol. 23, p. 29-36Article in journal (Refereed)
  • 9.
    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.

  • 10. Luo, J
    et al.
    Morad, S
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. Solid Earth Geology.
    Liang, Z
    Zhu, Y
    Controls on the Archaeozoic-Jurassic Metamorphic-Volcanic Reservoir Quality from the Xinglongtai Buried Hill, Western Depression of Liaohe basin, China2005In: American Association of Petroleum Geologists Bulletin, Vol. 89, p. 1319-1346Article in journal (Refereed)
  • 11.
    Mansurbeg, H
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Morad, S
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Amorosi, A
    Garcia, D
    Marfil, D
    Nystuen, J.P
    The impact of meteoric-water flux on diagenetic alterations in Palaeocene deep-water, marine sandstones, The Shetland-faroes basin, The British continental shelf2005In: Geophysical Research Abstracts, Vol. 75, p. 04781-Article in journal (Refereed)
  • 12. 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.

  • 13.
    Mansurbeg, Howri
    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.
    Plink-Björklund, P.
    El-Ghali, M. A. K.
    Caja, M.A.
    Marfil, R.
    Diagenetic Alterations Related to Falling Stage and Lowstand Systems Tracts of Shelf, Slope and Basin Floor Sandstones (Eocene Central Basin, Spitsbergen)2013In: Linking Diagenesis to Sequence Stratigraphy / [ed] Sadoon Morad, J. Marcelo Ketzer, Luiz F. De Ros, John Wiley & Sons, 2013, p. 353-378Chapter in book (Refereed)
  • 14.
    Morad, S.
    et al.
    Department of Petroleum Geosciences, The Petroleum Institute, Abu Dhabi, United Arab Emirates.
    Al-Aasm, I.S.
    Department of Petroleum Geosciences, The Petroleum Institute, Abu Dhabi, United Arab Emira.
    Sirat, M.
    Schlumberger Oilfield Middle East and Asia, Abu Dhabi, United Arab Emirates.
    Vein calcite in Cretaceous carbonate reservoirs of Abu Dhabi: Record of fluid flow2010In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 106, no 1-3, p. 156-170Article in journal (Refereed)
    Abstract [en]

    Petrographic, geochemical analyses (major, trace and rare-earth elements and C, O- and Sr-isotopes), and fluid-inclusion microthermometry study of vein calcites in primarily Cretaceous reservoir carbonate rocks in oilfields from Abu Dhabi, UAE, helped to unravel the formation conditions and origin of diagenetic fluids.

    The vein calcites have diverse crystal shapes (equant blocky, bladed and fibrous) and sizes (up to 3 cm across) and display complex cross-cutting relationships. These calcites display a wide range of stable carbon (δ13CV-PDB = − 11.1‰ to + 9.6‰) and oxygen (δ18OV-PDB = − 12.7‰ to − 2.3‰) isotopic compositions, indicating formation under diverse geological conditions. The oxygen isotopic composition suggests that the precipitation of vein calcites occurred at temperatures of ca. 30–100 °C assuming that the fluids had δ18OV-SMOW values of marine pore waters which evolved to basinal brines (i.e. − 1.2‰ and + 2‰, respectively). These inferred temperatures corroborate the fluid-inclusion microthermometry, which revealed a predominantly single, whole liquid phase that suggests entrapment temperature less than ca. 50 °C. A few two-phase fluid inclusions in equant and bladed calcite indicate precipitation at ca. 68–100 °C and salinity of ca. 3.9–10.1 wt.% equivalent NaCl).

    The carbon isotopic signatures suggest derivation of dissolved carbon from the host marine carbonates and, less commonly, from the degradation of organic matter by methanogenic and sulfate-reducing bacteria. The diverse sources of carbon coupled with the inferred wide range of precipitation temperatures presumably account for the lack of correlation between the carbon and oxygen isotopes. The derivation of dissolved carbon mainly from the host rocks is in good agreement with the marine Sr isotopic ratios of these calcites (87Sr/86Sr = 0.70744 to 0.70766). Rare-earth element patterns suggest significant fluid interaction with upper continental crustal rocks as evidenced by negative Eu anomalies and LREE-enriched patterns.

  • 15.
    Morad, Sadoon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Al-Aasm, Ihsan S.
    Nader, Fadi H.
    Ceriani, Andrea
    Gasparrini, Marta
    Mansurbeg, Howri
    Impact of diagenesis on the spatial and temporal distribution of reservoir quality in the Jurassic Arab D and C members, offshore Abu Dhabi oilfield, United Arab Emirates2012In: GeoArabia, ISSN 1025-6059, Vol. 17, no 3, p. 17-56Article in journal (Refereed)
    Abstract [en]

    This study is based on petrographic examination (optical, scanning electron microscope, cathodo-luminescence, backscattered electron imaging, and fluorescence) of 1,350 thin sections as well as isotopic compositions of carbonates (172 carbon and oxygen and 118 strontium isotopes), microprobe analyses, and fluid inclusion microthermometry of cored Jurassic Arab D and C members from 16 wells in a field from offshore Abu Dhabi, United Arab Emirates. The formation was deposited in a ramp with barrier islands and distal slope setting. Petrographic, stable isotopic and fluid-inclusion analyses have unraveled the impact of diagenesis on reservoir quality of Arab D and C within the framework of depositional facies, sequence stratigraphy, and burial history. Diagenetic processes include cementation by grain rim cement and syntaxial calcite overgrowths, formation of moldic porosity by dissolution of allochems, dolomitization and dolomite cementation, cementation by gypsum and anhydrite, and stylolitization. Partial eogenetic calcite and dolomite cementation has prevented porosity loss in grainstones during burial diagenesis. Dolomitization and sulphate cementation of peritidal mud are suggested to have occurred in an evaporative sabkha setting, whereas dolomitization of subtidal packstones and grainstones was driven by seepage reflux of lagoon brines formed during major falls in relative sea level. Recrystallization of dolomite occurred by hot saline waters (T-h 85-100 degrees C; and salinity 14-18 wt% NaCl). Anhydrite and gypsum cements (T-h 95-105 degrees C; fluid salinity 16-20 wt% NaCl), were subjected to extensive dissolution, presumably caused by thermal sulfate reduction followed by a major phase of oil emplacement. The last cement recorded was a second phase of anhydrite and gypsum (T-h 95-120 degrees C; 16-22 wt% NaCl), which fills fractures associated with faults.

  • 16.
    Morad, Sadoon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Al-Ramadan, Khalid
    King Fahd Univ Petr & Minerals, Dept Earth Sci, Dhahran, Saudi Arabia .
    Ketzer, João Marcelo
    De Ros, L. F.
    The impact of diagenesis on the heterogeneity of sandstone reservoirs: A review of the role of depositional facies and sequence stratigraphy2010In: American Association of Petroleum Geologists Bulletin, ISSN 0149-1423, E-ISSN 1558-9153, Vol. 94, no 8, p. 1267-1309Article in journal (Refereed)
    Abstract [en]

    Diagenesis exerts a strong control on the quality and heterogeneity of most elastic reservoirs. Variations in the distribution of diagenetic alterations usually accentuate the variations in depositional porosity and permeability. Linking the types and distribution of diagenetic processes to the depositional facies and sequence-stratigraphic framework of clastic successions provides a powerful tool to predict the distribution of diagenetic alterations controlling quality and heterogeneity. The heterogeneity patterns of sandstone reservoirs, which determine the volumes, flow rates, and recovery of hydrocarbons, are controlled by geometry and internal structures of sand bodies, grain size, sorting, degree of bioturbation, provenance, and by the types, volumes, and distribution of diagenetic alterations. Variations in the pathways of diagenetic evolution are linked to (1) depositional facies, hence pore-water chemistry, depositional porosity and permeability, types and amounts of intrabasinal grains, and extent of bioturbation; (2) detrital sand composition; (3) rate of deposition (controlling residence time of sediments at specific near-surface, geochemical conditions); and (4) burial thermal history of the basin. The amounts and types of intrabasinal grains are also controlled by changes in the relative sea level and, therefore, can be predicted in the context of sequence stratigraphy, particularly in paralic and shallow marine environments. Changes in the relative sea level exert significant control on the types and extent of near-surface shallow burial diagenetic alterations, which in turn influence the pathways of burial diagenetic and reservoir quality evolution of elastic reservoirs. Carbonate cementation is more extensive in transgressive systems tract (TST) sandstones, particularly below parasequence boundaries, transgressive surface, and maximum flooding surface because of the abundance of carbonate bioclasts and organic matter, bioturbation, and prolonged residence time of the sediments at and immediately below the sea floor caused by low sedimentation rates, which also enhance the formation of glaucony. Eogenetic grain-coating berthierine, odinite, and smectite, formed mostly in TST and early highstand systems tract deltaic and estuarine sandstones, are transformed into ferrous chlorite during mesodiagenesis, helping preserve reservoir quality through the inhibition of quartz cementation. The infiltration of grain-coating smectitic clays is more extensive in braided than in meandering fluvial sandstones, forming flow barriers in braided amalgamated reservoirs, and may either help preserve porosity during burial because of quartz overgrowth inhibition or reduce it by enhancing intergranular pressure dissolution. Diagenetic modifications along sequence boundaries are characterized by considerable dissolution and kaolinization of feldspars, micas, and mud intraclasts under wet and warm climates, whereas a semiarid climate may lead to the formation of calcrete dolocrete cemented layers. Turbidite sandstones are typically cemented by carbonate along the contacts with interbedded mudrocics or carbonate mudstones and marls, as well as along layers of concentration of carbonate bioclasts and intraclasts. Commonly, hybrid carbonate turbidite arenites are pervasively cemented. Proximal, massive turbidites normally show only scattered spherical or ovoid carbonate concretions. Improved geologic models based on the connections among diagenesis, depositional facies, and sequence-stratigraphic surfaces and intervals may not only contribute t optimized production through the design of appropriate simulation models for improved or enhanced oil recovery strategies, as well as for CO2 geologic sequestration, but also support more effective hydrocarbon exploration through reservoir quality prediction.

  • 17.
    Morad, Sadoon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ketzer, J.M.
    De Ros, L.F.
    Linking Diagenesis to Sequence Stratigraphy: An Integrated Tool for Understanding and Predicting Reservoir Quality Distribution2013In: Linking Diagenesis to Sequence Stratigraphy / [ed] Sadoon Morad, J. Marcelo Ketzer, Luiz F. De Ros, John Wiley & Sons, 2013, p. 1-36Chapter in book (Refereed)
    Abstract [en]

    Sequence stratigraphy is a useful tool for the prediction of primary (depositional) porosity and permeability. However, these primary characteristics are modified to variable extents by diverse diagenetic processes. This chapter demonstrates that integration of sequence stratigraphy and diagenesis is possible because the parameters controlling the sequence stratigraphic framework may have a profound impact on early diagenetic processes. The latter processes play a decisive role in the burial diagenetic and related reservoir-quality evolution pathways. Therefore, the integration of sequence stratigraphy and diagenesis allows a proper understanding and prediction of the spatial and temporal distribution of diagenetic alterations and, consequently, of reservoir quality in sedimentary successions.

  • 18. Nader, F.H.
    et al.
    De Boever, E.
    Gasparrini, M.
    Liberati, M.
    Dumont, C.
    Ceriani, A.
    Morad, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lerat, O.
    Doligez, B.
    Quantification of diagenesis impact on the reservoir properties of the Jurassic Arab D and C members (Offshore, U.A.E.)2013In: Geofluids, ISSN 1468-8115, E-ISSN 1468-8123, Vol. 13, no 2, p. 204-220Article in journal (Refereed)
    Abstract [en]

    An increasing need exists to quantify the impact of diagenesis on complex and heterogeneous geological reservoirs and to predict the related field-scale porosity-permeability distribution. Development of approaches to quantify diagenetic events is an important step towards the construction of integrated numerical reservoir models predicting the impact of successive diagenetic events on petrophysical properties at various scales. This article describes two distinct approaches, which allow capturing, quantifying and explaining reservoir heterogeneities of the Jurassic Arab Formation (offshore oilfield in Abu Dhabi, U.A.E.) at the field and plug scale. Based on a classical diagenesis study, whereby the major diagenetic phases were characterized, distribution patterns were highlighted to further explain reservoir heterogeneities through a set of 2D interpolation diagenesis maps across the field. The best reservoir properties are encountered in the central-northern (grainstones with syntaxial calcite overgrowth cement – typical of Arab D) and south-western (dolostones – typical of Arab C) parts of the oilfield. Following another independent approach at the scale of the plug, quantification of rock components and description of the pore space connectivity and geometry are obtained by 2D and 3D image analyses, μ-CT and pore network modelling. This latter approach resulted in a better understanding of the effect of anhydrite dissolution on the pore structure of the investigated dolostone. The overall, presented workflow provides valuable constraints for assessing reservoir heterogeneities in statistical field-scale models.

  • 19. Salem, A.M
    et al.
    Ketzer, J.M
    Morad, S
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. Solid Earth Geology.
    Diagenesis and reservoir-quality evolution of incised-valley sandstones: evidence from the Abu-Madi gas reservoirs (Upper Miocene), the Nile Delta Basin, Egypt2005In: Journal of Sedimentary Research, Vol. 75, p. 572-584Article in journal (Refereed)
  • 20.
    Vieira, Marcela Marques
    et al.
    Univ Fed Rio Grande do Norte, Ctr Ciencias Exatas & Terra, Dept Geol, Natal, RN, Brazil..
    Sial, Alcides Nobrega
    Univ Fed Pernambuco, NEG LABISE, Dept Geol, Recife, PE, Brazil..
    De Ros, Luiz Fernando
    Univ Fed Rio Grande do Sul, Programa Posgrad Geociencias, Porto Alegre, RS, Brazil..
    Morad, Sadoon
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Petr Inst, Dept Petr Geosci, POB 2533, Abu Dhabi, U Arab Emirates..
    Origin of holocene beachrock cements in northeastern Brazil: Evidence from carbon and oxygen isotopes2017In: Journal of South American Earth Sciences, ISSN 0895-9811, E-ISSN 1873-0647, Vol. 79, p. 401-408Article in journal (Refereed)
    Abstract [en]

    This study has utilized carbon and oxygen isotopic data to unravel the origin of Holocene beachrock cements of Rio Grande do Norte State coast, northeastern Brazil. The cements are exclusively constituted of Mg-calcite, with isopachous prismatic rim, equant spar, cryptocrystalline coating or pore-filling, pseudo-peloidal, radial and scalenohedral habits. The delta O-18(VPDB) values of most (93%) of the samples range from -1.8 parts per thousand to +0.5 parts per thousand, which are compatible with precipitation from marine waters. The delta C-13(VPDB) values of these cements are +1.7 to +3.6 parts per thousand (average + 3.05 parts per thousand) suggesting derivation from marine dissolved carbon. In a few cases, the Mg-calcite cement shows low delta C-13(VPDB) (-7.3% o and -7.8 parts per thousand) and delta O-18(VPDB) (-4.4 parts per thousand and -4.3) values, which may indicate precipitation or recrystallization of marine cements under the influence of meteoric waters.

  • 21. Worden, R.H
    et al.
    Morad, S
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Quartz cementation in oilfield sandstones: a review of the key controversies2000In: Special Publication, International Association of Sedimentologists, no 29, p. 1-20Article in journal (Refereed)
1 - 21 of 21
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