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Evidence for high temperature and 18 O‐enriched fluids in the Arab‐D of the Ghawar Field, Saudi Arabia
Author(s) -
Swart Peter K.,
Cantrell Dave L.,
Arienzo Monica M.,
Murray Sean T.
Publication year - 2016
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/sed.12286
Subject(s) - dolomite , geology , diagenesis , dolomitization , calcite , recrystallization (geology) , isotopes of oxygen , mineralogy , permeability (electromagnetism) , carbonate , geochemistry , petrology , paleontology , chemistry , materials science , facies , metallurgy , biochemistry , structural basin , membrane
Using the clumped isotope method, the temperature of dolomite and calcite formation and the oxygen isotopic composition (δ 18 O w ) of the diagenetic fluids have been determined in a core taken from the Arab‐D of the Ghawar field, the largest oil reservoir in the world. These analyses show that while the dolomites and limestones throughout the major zones of the reservoir recrystallized at temperatures between ca 80°C and 100°C, the carbonates near the top of the reservoir formed at significantly lower temperatures (20 to 30°C). Although the δ 18 O values of the diagenetic fluids show large variations ranging from ca <0‰ to ca +8‰, the variations exhibit consistent downhole changes, with the highest values being associated with the portion of the reservoir with the highest permeability and porosity. Within the limestones, dolomites and dolomites associated with the zone of high permeability, there are statistically significant different trends between the δ 18 O w values and recrystallization temperature. These relationships have different intercepts suggesting that fluids with varying δ 18 O w values were involved in the formation of dolomite and limestone compared to the formation of dolomite associated with the zone of high permeability. These new data obtained using the clumped isotope technique show how dolomitization and recrystallization by deep‐seated brines with elevated δ 18 O w values influence the δ 18 O values of carbonates, possibly leading to erroneous interpretations unless temperatures can be adequately constrained.