SEPM-Journal of Sedimentary Research Abstracts 9/9/02 5:41 PM
THE INFLUENCE OF ROCK FABRIC AND MINERALOGY ON THERMOCHEMICAL SULFATE REDUCTION: KHUFF FORMATION, ABU DHABI
R.H. WORDEN1*, P.C. SMALLEY , AND M.M. CROSS
1School of Geosciences, The Queen's University, Belfast BT7 1NN, U.K. 2BP-Amoco, Chertsey Road, Sunbury on Thames, Middlesex TW17 7LN, U.K. 3Department of Earth Sciences, The University of Manchester, Manchester M13 9PL, U.K.
Present address: Department of Earth Sciences, University of Liverpool, Brownlow Street, Liverpool L69 3BX, U.K. email: [email protected]
ABSTRACT: Thermochemical sulfate reduction (TSR) is the reaction between anhydrite and petroleum fluids at elevated temperatures to produce H2S and calcite. In this study of the dolomite-hosted hydrocarbon gas reservoirs in the Permo-Triassic Khuff Formation, Abu Dhabi, a geochemically well constrained rock--gas system, we demonstrate for the first time a clear influence of rock texture and mineralogy on the rate and extent of TSR reactions and thus on H2S concentration in the gas phase. The controls on the rate on H2S accumulation were:
Localized loss of H2S occurred in the reservoir by reaction with indigenous Fe-bearing clays. Consequently, reservoirs with a relatively high siliciclastic content have less H2S than would be expected from the advanced state of anhydrite replacement by calcite. In order to predict TSR-related H2S concentration in hydrocarbon gases it is thus important to understand the diagenetic
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and textural characteristics of the reservoir as well as the thermal and petroleum-emplacement history.
Revised Mon Oct 2 15:34:36 MDT 2000
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