Tectonically controlled diagenesis and fluid evolution in Al Khlata reservoir sandstones, Sultanate of Oman

Ramseyer, Karl; Juhasz-Bodnar, Katalin; Bücker, Carsten; Hoppe, Peter; Matter, Albert; Terken, Jos; Amthor, Joachim E.; Driehorst, Frauke (2019). Tectonically controlled diagenesis and fluid evolution in Al Khlata reservoir sandstones, Sultanate of Oman. In: Siliciclastic reservoirs of the Arabian plate. AAPG Memoir: Vol. 116 (pp. 37-82). Tulsa, Oklahoma: American Association of Petroleum Geologists (AAPG) 10.1306/13642173M1183804

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Late Carboniferous to early Permian glacigenic Al Khlata Formation reservoirs account for one of the largest hydrocarbon productions in the Sultanate of Oman. Tectonic activities caused a varied subsidence, uplift, and erosion history resulting in present-day formation depths between surface exposure and approximately 4000 m (13,125 ft). Furthermore, tectonism caused fluid incursions leading to mineral reactions and porosity-modifying processes. Since deposition, the pore water evolved from low-salinity and negative d18OVSMOW value to a high-salinity brine with a positive d18OVSMOW value. This change is related to Ara salt halokinesis beginning at approximately 200 Ma. At the eastern flank of the Ghaba Salt Basin, low saline intervals occurred isochronously with the obduction of the Hawasina Nappes–Samail Ophiolite. Dilution event(s) and changes to negative d18OVSMOW values occurred between 60 and 50 Ma because of intraplate deformation creating new fluid pathways. Reservoir quality deterioration results from compactional porosity loss and heavy quartz cementation. Authigenic quartz precipitated as zoned syntaxial overgrowths cogenetically with calcite, Fe-dolomite, anhydrite, and kaolinite. Hydrochemical modeling of kaolinite precipitation indicates a link to CO2 migration rather than meteoric water infiltration. The onset of quartz cementation was contemporaneous with the obduction of the Hawasina Nappes–Samail Ophiolite irrespective of burial temperature, thus indicating a tectonic rather than a purely kinetic control.

Item Type:

Book Section (Book Chapter)

Division/Institute:

08 Faculty of Science > Other Institutions > Emeriti, Faculty of Science
08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Ramseyer, Karl

Subjects:

500 Science > 550 Earth sciences & geology

ISBN:

9780891813989

Series:

AAPG Memoir

Publisher:

American Association of Petroleum Geologists (AAPG)

Language:

English

Submitter:

Karl Ramseier

Date Deposited:

26 Aug 2019 16:33

Last Modified:

06 Nov 2019 11:50

Publisher DOI:

10.1306/13642173M1183804

BORIS DOI:

10.7892/boris.132565

URI:

https://boris.unibe.ch/id/eprint/132565

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