Swelling and embedment induced by sub- and super-critical-CO2 on the permeability of propped fractures in shale

Chemo‐Mechanical Coupling in Fractured Shale With Water and Hydrocarbon Flow

“…The potential to generate permeability by induced damage continues to raise concerns regarding the deployment of large‐scale geologic CO 2 storage (Cappa & Rutqvist, 2011; Zoback & Gorelick, 2012) and of nuclear waste repositories (Urpi et al., 2019), where shale and mudstone form the main seal system that prevents the escape of fluids. Yet, field evidence shows that it is technically difficult to sustain hydrocarbon production from shale reservoirs, requiring the use of “proppants” (Hou et al., 2020). While the quantitative evaluation of the risk of induced seismicity underpins the feasibility of these subsurface operations (Ellsworth, 2013; Juanes et al., 2012; Rubinstein & Mahani, 2015), addressing the consequences of the presence of fractures in a damaged clay‐rich rock remains an outstanding research question.…”

Mechanisms of tripartite permeability evolution for supercritical CO2 in propped shale fractures

“…7(a). The severe swelling strain may consume ~80% of the effective aperture (Hou et al, 2020). Swelling stresses of 9.6-24.7 MPa may result upon introduction of CO2 at 10 MPa and 44°C measured by uniaxial compaction/swelling test on montmorillonite and shale (Zhang et al, 2018).…”

“…Impacts of CO2-matrix interaction (such as swelling) are relatively less prominent, especially for shales because of their lower organic contents. However, recent studies in high-organic-content Green River shale indicates that swelling could consume as much as 50% of the permeability and increase embedment by a factor of ~2 (Hou, Elsworth, & Geng, 2020).…”

“…(3) The CO2 phase transition is observed to dramatically change permeability in simple powders (Jia, Tsau, & Barati, 2018), intact coal (Zhi, Elsworth, & Liu, 2019) and propped fractures in shale (Hou et al, 2020;. A sudden increase in density and kinetic energy may enhance the sorption capacity and plasticize the solid material to generate a precipitous drop in permeability around the critical point.…”

Review of fundamental studies of CO2 fracturing: Fracture propagation, propping and permeating

“…8. The swelling independently contributes 9-56% ((∆b 2 -∆b 3 )/(∆b 2 -∆b 1 )) of the total sorbinginduced fracture loss, which may be evaluated from the adsorbed mass (Hou, Elsworth and Geng 2020).…”