CO₂-induced chemo-mechanical alteration in reservoir rocks assessed via batch reaction experiments and scratch testing

Journal Article · 21 September 2017 · Greenhouse Gases: Science and Technology

DOI: https://doi.org/10.1002/ghg.1726 · OSTI ID:1399569

Aman, Michael  ^[1]; Espinoza, D. Nicolas  ^[1]; Ilgen, Anastasia G. ^[2]; Major, Jonathan R. ^[1]; Eichhubl, Peter ^[1]; Dewers, Thomas A. ^[2]

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1. The Univ. of Texas at Austin, Austin, TX (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Here, the injection of carbon dioxide (CO₂) into geological formations results in a chemical re-equilibration between the mineral assemblage and the pore fluid, with ensuing mineral dissolution and re-precipitation. Hence, target rock formations may exhibit changes of mechanical and petrophysical properties due to CO₂ exposure. We conducted batch reaction experiments with Entrada Sandstone and Summerville Siltstone exposed to de-ionized water and synthetic brine under reservoir pressure (9–10 MPa) and temperature (80°C) for up to four weeks. Samples originate from the Crystal Geyser field site, where a naturally occurring CO₂ seepage alters portions of these geologic formations. We conducted micro-scratch tests on rock samples without alteration, altered under laboratory conditions, and naturally altered over geologic time. Scratch toughness and hardness decrease as a function of exposure time and water salinity up to 52% in the case of Entrada and 87% in the case of Summerville after CO₂-induced alteration in the laboratory. Imaging of altered cores with SEM-EDS and X-ray microCT methods show dissolution of carbonate and silica cements and matrix accompanied by minor dissolution of Fe-oxides, clays, and other silicates. Parallel experiments using powdered samples confirm that dissolution of carbonate and silica are the primary reactions. The batch reaction experiments in the autoclave utilize a high fluid to rock volume ratio and represent an end member of possible alteration associated with CO₂ storage systems. These types of tests serve as a pre-screening tool to identify the susceptibility of rock facies to CO₂-related chemical-mechanical alteration during long-term CO₂ storage.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Frontiers of Subsurface Energy Security (CFSES)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1399569
• Alternate ID(s): OSTI ID: 1393992
• Report Number(s): SAND--2017-9043J; {"Journal ID: ISSN 2152-3878",656485}
• Journal Information: Greenhouse Gases: Science and Technology, Journal Name: Greenhouse Gases: Science and Technology Journal Issue: 1 Vol. 8; ISSN 2152-3878
• Publisher: Society of Chemical Industry, WileyCopyright Statement
• Country of Publication: United States
• Language: English