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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 Emirates
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
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2012 (English)In: GeoArabia, ISSN 1025-6059, Vol. 17, no 3, 17-56 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
2012. Vol. 17, no 3, 17-56 p.
National Category
Earth and Related Environmental Sciences
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
URN: urn:nbn:se:uu:diva-179591ISI: 000306151000002OAI: oai:DiVA.org:uu-179591DiVA: diva2:545316
Available from: 2012-08-20 Created: 2012-08-20 Last updated: 2012-12-17Bibliographically approved

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Morad, Sadoon
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