Title: CO ₂-induced chemo-mechanical alteration in reservoir rocks assessed via batch reaction experiments and scratch testing

Abstract

Here, the injection of carbon dioxide (CO ₂) 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 CO ₂ 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 CO ₂ 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 CO ₂-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. Themore » batch reaction experiments in the autoclave utilize a high fluid to rock volume ratio and represent an end member of possible alteration associated with CO ₂ storage systems. These types of tests serve as a pre-screening tool to identify the susceptibility of rock facies to CO ₂-related chemical-mechanical alteration during long-term CO ₂ storage.« less

Authors:

Aman, Michael  ^[1];

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Espinoza, D. Nicolas  ^[1];

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Ilgen, Anastasia G. ^[2]; Major, Jonathan R. ^[1]; Eichhubl, Peter ^[1]; Dewers, Thomas A. ^[2]

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+ Show Author Affiliations

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

Publication Date:

2017-09-22

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Frontiers of Subsurface Energy Security (CFSES)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)

OSTI Identifier:

1399569

Alternate Identifier(s):

OSTI ID: 1393992

Report Number(s):

SAND-2017-9043J
Journal ID: ISSN 2152-3878; 656485

Grant/Contract Number:  

AC04-94AL85000; SC0001114

Resource Type:

Accepted Manuscript

Journal Name:

Greenhouse Gases: Science and Technology

Additional Journal Information:

Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2152-3878

Publisher:

Society of Chemical Industry, Wiley

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; micromechanics; chemo-mechanical coupling; dissolution; scratch toughness; carbon storage