Case, George, Weislogel, Amy, and Coffindaffer, Keith (2014) Petrologic evidence for the diagenesis of the Donovan Sand, Citronelle Field, Alabama, and implications for CO2 storage and enhanced oil recovery. Environmental Geosciences, 21 (4). pp. 141-159.

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Abstract

Geological sequestration of CO2 for enhanced oil recovery (EOR) has been in use for decades, but it now represents a potentially economical method of mitigating anthropogenic CO2 output. However, current understanding of the interaction between injected CO2 and the reservoir rock is limited and prevents accurate estimation of reservoir CO2 capacity. Delineating the diagenesis of the reservoir is useful in predicting post-CO2 injection changes in reservoir porosity and permeability. The Albian Donovan Sand member of the Rodessa Formation, Citronelle Field, Alabama, is the subject of an ongoing Department of Energy CO2-EOR suitability study. The arkosic Donovan Sand is highly heterogeneous, containing conglomeratic intervals, low to extensive poikilotopic calcite cement, loose to tight grain packing, and low <1% to high (5%) porosity (primary and secondary) observed in thin section. It forms the basal members of laterally discontinuous upward-fining parasequences that define a marine to brackish to fluvial delta system. The diagenesis of the Donovan Sand occurred in five stages: 1) pre-burial and compaction–formation of extensive calcite cement; 2) partial dissolution of calcite cement and framework feldspars; 3) secondary calcite cementation, localized dolomitization, and calcite and anhydrite concretion formation; 4) hydrocarbon charge; and 5) pyrobitumen development. Primary porosity is dominant, but substantial secondary porosity was formed during stage 2. Following injection of CO2, water injection and oil and gas production rates dropped below modeled values. We propose that the CO2 injection dissolved calcite cement proximal to the injection well and reprecipitated it nearby with the effect of reducing porosity and/or permeability.

Item ID:	38841
Item Type:	Article (Research - C1)
ISSN:	1526-0984
Date Deposited:	12 May 2015 23:26
FoR Codes:	04 EARTH SCIENCES > 0403 Geology > 040310 Sedimentology @ 60% 04 EARTH SCIENCES > 0403 Geology > 040309 Petroleum and Coal Geology @ 20% 04 EARTH SCIENCES > 0403 Geology > 040306 Mineralogy and Crystallography @ 20%
SEO Codes:	85 ENERGY > 8502 Mining and Extraction of Energy Resources > 850203 Oil and Gas Extraction @ 50% 85 ENERGY > 8598 Environmentally Sustainable Energy Activities > 859802 Management of Greenhouse Gas Emissions from Electricity Generation @ 50%
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