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GEOREF RECORD

Dolomite and dolomitization of the Permian Khuff-C reservoir in Ghawar Field, Saudi Arabia

Mohammed A. Alqattan and David A. Budd
Dolomite and dolomitization of the Permian Khuff-C reservoir in Ghawar Field, Saudi Arabia
AAPG Bulletin (October 2017) 101 (10): 1715-1745

Abstract

The Permian Khuff-C reservoir in Saudi Arabia is known for its lateral and vertical heterogeneity caused mainly by dolomitization. Detailed petrographic analysis of 600 thin sections, from six cored wells, revealed three main replacive dolomite fabrics: (1) fabric-preserving mimetic (FPM), (2) fabric-preserving nonmimetic (FPNM), and (3) fabric-destructive (FD) dolomites. Crystal sizes are mostly less than or equal to 20 mu m for FPM dolomite, less than or equal to 50 mu m for FPNM dolomite, and less than or equal to 100 mu m for FD dolomite. The FPM dolomite decreases in abundance, and FPNM dolomite increases in abundance, with increasing grain content of the facies. The delta (super 18) O values of dolostones (although considered an obsolete term, dolostone is used here to mean rock containing > or =80% dolomite) indicate early dolomitization at low temperatures in Permian seawater or evaporated seawater, with landward facies (mudstone and wackestone) generally dolomitized by more evaporated waters and seaward grainy facies generally dolomitized by less evaporated, more normal marine seawaters. Stratigraphic variations in the dolostones' delta (super 18) O values track with facies variations through fourth-order depositional sequences and indicate that different stratigraphic bodies of dolomite formed from seawaters with different degrees of evaporation. The delta (super 13) C values of the dolostones exhibit temporal trends inherited from the precursor limestones. Variations in the lateral and vertical abundance of dolomite and dolomite fabrics, in the propensity for each facies to be dolomitized, and in the dolomites' oxygen isotopic values all suggest that multiple dolomitization events occurred in the Khuff-C reservoir as depositional cycles accumulated, with some dolostones overprinted by younger events. Average porosities of grain-rich dolostones are greater than those of mud-rich dolostones, indicating that depositional facies preordained porosity distribution within the dolostones. However, the more evaporated the dolomitizing fluid, the more likely dolomitization resulted in lower porosity regardless of facies.


ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 101
Serial Issue: 10
Title: Dolomite and dolomitization of the Permian Khuff-C reservoir in Ghawar Field, Saudi Arabia
Affiliation: Saudi Aramco, Exploration Technical Services Department, Dhahran, Saudi Arabia
Pages: 1715-1745
Published: 201710
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
References: 74
Accession Number: 2017-087907
Categories: Economic geology, geology of energy sourcesSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. chart, 5 tables, sketch map
N23°19'60" - N24°30'00", E49°15'00" - E50°00'00"
Secondary Affiliation: University of Colorado, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by American Association of Petroleum Geologists, Tulsa, OK, United States
Update Code: 201746
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