Relationships between fault characteristics and seismic responses in a large lab-scale tri-axial injection test conducted on a faulted Castlegate Sandstone

Journal Article · 02 August 2022 · Journal of Structural Geology

DOI: https://doi.org/10.1016/j.jsg.2022.104684 · OSTI ID:1977408

Babarinde, Oladipupo  ^[1]; Stanchits, Sergey  ^[2]; Bauer, Robert ^[3]; Frailey, Scott ^[3]; Oye, Volker ^[4]; Sweet, Dustin  ^[5]

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1. Univ. of Illinois at Urbana-Champaign, IL (United States); OSTI
2. Skolkovo Institute of Science and Technology, Moscow (Russian Federation)
3. Univ. of Illinois at Urbana-Champaign, IL (United States)
4. NORSAR, Kjeller (Norway)
5. Texas Tech Univ., Lubbock, TX (United States)

Here to investigate mechanisms causing microseismicity (M_w < 2) at a CO₂ injection site, a large-scale triaxial block experiment was carried out on a faulted (saw-cut) cubic-meter of Castlegate Sandstone. The experiment consisted of injection tests at varying differential stresses, while monitoring and recording pore pressure and acoustic emissions (AEs). During the experiment, ~33,000 AEs and ~14 mm of horizontal displacement/slip, like a strike-slip fault movement, occurred. To understand the AE responses and ascertain fault characteristics near the located AEs, we modeled the topography of the fault surface, fault aperture, and fault-gouge thickness using pre- and post-experiment laser scans of the fault surface on each half of the block. Additionally, we characterized surface roughness parallel and perpendicular to slip. Models show crushing and flattening of the fault surfaces can be linked to the spatiotemporal distribution of AEs within 50 mm of the fault surface. Approximately 65% of AEs were in areas with small aperture (≤300 μm); thicker fault gouge was observed in adjacent areas with wider aperture and shows a two-fold reduction in grain size relative to unaltered Castlegate Sandstone. This work provides a conceptual understanding on fault surface evolution, which can be applied towards modeling of seismic slip.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Center for Geologic Storage of CO2 (GSCO2); Univ. of Illinois at Urbana-Champaign, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0012504
• OSTI ID: 1977408
• Journal Information: Journal of Structural Geology, Journal Name: Journal of Structural Geology Journal Issue: C Vol. 162; ISSN 0191-8141
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English