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Title: Evaporite Caprock Integrity. An experimental study of reactive mineralogy and pore-scale heterogeneity during brine-CO2 exposure

Characterization and geochemical data are presented from a core-flooding experiment on a sample from the Three Fingers evaporite unit forming the lower extent of caprock at the Weyburn-Midale reservoir, Canada. This low-permeability sample was characterized in detail using X-ray computed microtomography before and after exposure to CO 2-acidified brine, allowing mineral phase and voidspace distributions to be quantified in three dimensions. Solution chemistry indicated that CO 2-acidified brine preferentially dissolved dolomite until saturation was attained, while anhydrite remained unreactive. Dolomite dissolution contributed to increases in bulk permeability through the formation of a localized channel, guided by microfractures as well as porosity and reactive phase distributions aligned with depositional bedding. An indirect effect of carbonate mineral reactivity with CO 2-acidified solution is voidspace generation through physical transport of anhydrite freed from the rock matrix following dissolution of dolomite. The development of high permeability fast pathways in this experiment highlights the role of carbonate content and potential fracture orientations in evaporite caprock formations considered for both geologic carbon sequestration and CO 2-enhanced oil recovery operations.
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
OSTI Identifier:
1237526
Report Number(s):
LLNL-JRNL--544136
Journal ID: ISSN 0013-936X
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 47; Journal Issue: 1; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
20 FOSSIL-FUELED POWER PLANTS; 54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 02 PETROLEUM geologic carbon sequestration; caprock stability; evaporate; anhydrite; dolomite; fracture; x-ray tomography; enhanced oil recovery