Stress-dependent permeability of a de-mineralised fracture in shale

Fracture transmissivity as a function of normal and shear stress: First results in Opalinus Clay

“…where T is the transmissivity, h i is the head on the inner surface with radius r i , and h o is the head on the outer surface at radius r o (Gutierrez et al, 2000). For the experimental setup r 0 = 30 mm, r i = 1.96 mm, h 0 = 0.05 m and h i ~ 100 m, transmissivity (m 2 /s) can simply be calculated from: if the fluid flux (Q in µl/hr) and pore pressure (P p in kPa) are known.…”

“…A range of non-linear relationships have been proposed between permeability, porosity, and pressure in shale and mudstones, including exponential and power laws (Dewhurst et al, 1999a;Katsube et al, 1991). Gutierrez et al (2000) investigated experimentally the hydromechanical behaviour of an extensional fracture in Kimmeridge Shale under normal and shear loading. It was shown that, at the time it was created, the fracture probably had about nine orders of magnitude higher permeability than the current permeability of the intact shale.…”

Creating the link between micro-seismic observations and hydro-mechanical changes in the reservoir

“…Shear--induced compaction (versus dilation) for a relatively weak Kimmeridge shale has been characterized by Gutierrez [32], and is shown in the figure to the right. Note, below 3 MPa confining pressure, the fracture dilates; whereas, above this, the fracture shears the asperities into gouge material that plugs the fracture and reduces permeability.…”

Fracture permeability under normal stress: a fully computational approach

“…shale, are rare. Experiments of (Gutierrez et al 2000) performed on Kimmeridge shale revealed irreversible, hysteretic fracture deformation under cyclic normal load. The fracture had nonmatching rough walls in that study.…”

“…reduction in the normal stress, is usually accompanied with hysteresis in the fracture permeability: the fracture permeability is different during unloading from what it was at the same stress during loading (Gutierrez et al 2000). Hysteresis of the fracture permeability under normal loading is a manifestation of a more general irreversibility of rock deformation that also includes, for example, the 'stress-memory' capacity of rocks (Becker et al 2010;Lavrov 2005).…”