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

Abstract

The transport of chemically reactive fluids through fractured clay‐rich rocks is fundamental to many subsurface engineering technologies. Here, we present results of direct‐shear laboratory experiments with simultaneous imaging by X‐ray Computed Tomography in Opalinus claystone with subsequent fluid injection to unravel the interplay between mechanical fracture deformation, fluid sorption, and flow. Under constant radial stress (σc = 1.5 MPa), the average mechanical aperture trued¯CT increases with shear displacement. Upon brine injection, trued¯CT is reduced by 40% relative to initial conditions (trued¯CT0=140−250 μm) and fluid‐sorption induces a divergent displacement of the two sample halves (Δh = ±50 − 170 μm) quantified by digital image correlation. None of these changes are observed in a control experiment with decane, indicating that creep is subordinate to swelling in sealing the fracture. Swelling‐induced changes in permeability within the fracture are heterogeneous and largely affect the fracture flow field, as computed using numerical simulations.

Geochemical Insight into CO2 Migration in a Faulted Caprock

“…On the other hand, the difference in arrival time could be caused by chemical retardation of the CO 2 . Retardation might result from fluid-rock or fluid-fluid interactions and mixing of fluids with contrasted chemical composition inducing processes such as adsorption, swelling, dissolution, precipitation, speciation, and ion exchange reactions [54][55][56][57][58]. The temporal evolution of He concentrations at the monitoring interval (Fig.…”

Quantification of the impact of acidified brine on fracture-matrix transport in a naturally fractured shale using in situ imaging and modeling

“…A quantitative and predictive understanding of transport across fracturematrix interfaces in shale formations is vital to the management and engineering of a range of flow and transport processes. These processes include groundwater protection from infiltrating contaminants [1], storage security of geologically sequestered CO 2 [2,3,4], resource recovery following hydraulic fracturing [5,6,7], and long-term nuclear waste storage security [8,9].…”

“…In cases where flow-through experiments are performed under elevated pressure and temperature, typically only one measurement may be possible in a given sample [33]. X-ray computed tomography (X-ray CT) is a key tool used to recover three-dimensional information about fracture geometry and multiphase flow under in situ conditions in geologic materials [34,35,4]. However, quantification of solute transport can be challenging with X-ray CT due to the need to use high photon attenuating tracers.…”

“…4 and C.5 show the aqueous reactions and mineral kinetic reactions respectively. Aqueous kinetic reactions respect a rate-dependent transition state theory (TST) rate law as shown in Equation C.1[56] where (a i ) n indicates the product of rate dependency on all aqueous species, K eq refers to equilibrium constant, k is the reaction rate constant in mol(kg water) −1 yr −1 , and IAP is the ion activity product.…”

Hydro‐Mechanical Measurements of Sheared Crystalline Rock Fractures With Applications for EGS Collab Experiments 1 and 2

“…Characterizing shear slip on natural fractures and faults can better inform predictions of natural or induced seismicity (Hincks et al., 2018), fault stability (Marone & Kilgore, 1993), and stimulated fracture fluid conductivity (Frash et al., 2017). Prior works have investigated frictional strength for stick‐slip behavior (Leeman et al., 2016), permeability evolution during earthquake slip (Im et al., 2018), fault weakening induced by fluid injection (Scuderi et al., 2017), and scaling relations from shear fractures measured in the laboratory to the larger field situation (Frash, Carey, & Welch, 2019; Pyrak‐Nolte & Morris, 2000; Schultz et al., 2008; Wenning et al., 2019, 2021). Accurate site‐specific characterization of shear fractures is especially important for geothermal energy applications where it is hoped that shear‐propping (McClure & Horne, 2014b) could be a good alternative to the conventional proppants that are expected to perform poorly at high‐stress and high‐temperature conditions (Brinton, 2011).…”