Stress-dependent fracture permeability measurements and implications for shale gas production

Hydro-mechanical measurements and x-ray imaging of sheared crystalline rock fractures from EGS Collab experiments 1 & 2

“…The mechanical and hydraulic aperture relationship has been studied extensively for unconventional shale rocks (Frash, 2016(Frash, , 2019cLi et al, 2020). Here, we explore the response of both mechanical and hydraulic fracture aperture to changing effective confining pressure in EGS Collab crystalline rocks.…”

“…Generally, the hydraulic aperture is lower than the mechanical aperture because of the existence of contact areas within the fractures due to fracture roughness and tortuosity (Xiong et al, 2011). Both 13 mechanical aperture and hydraulic aperture are important for fluid flow, with the prior controlling porosity and the latter controlling flow rates (Li et al, 2020). However, mechanical aperture and hydraulic aperture are influenced by effective normal stress (Wu et al, 2017;Fang et al, 2018a).…”

“…To interrelate these parameters, we first relate mechanical aperture with effective confining pressure (Barton et al, 1985) and then we relate mechanical aperture with hydraulic aperture (Witherspoon, 1980). Here, we consider two models for the relationship between the mechanical aperture and effective confining pressure, the Barton et al (1985) model and an exponential decay model (Li et al, 2020). Barton et al model (1985):…”

“…While Barton et al yields the better fit to the data, we prefer the exponential model for our subsequent estimation of the modified Witherspoon factor. Our selection stems from the inability to scale the Barton-Bandis model to fractures of different dimensions, whereas the exponential model is intuitively scalable (Li et al, 2020). Based on the fitted mechanical aperture from the exponential model, we fit the modified Witherspoon factor to the measured mechanical and hydraulic apertures.…”

Million node fracture: size matters?

“…Fractures play an important role in controlling hydraulic and transport properties of fractured rocks. In some types of hydrocarbon reservoirs, they can largely control the reservoir flow (Aguilera 1980;Li et al 2021). Understanding flow, transport and fluid displacement in natural fractures is crucial for optimization of production from such reservoirs.…”