Advance and improve experimental techniques to study fluid-assisted fracturing in weakly consolidated sediments.
Verify and characterize the presence of plastic yielding features such as shear banding and cavity expansion.
Study scale and stress effects on hydraulic fracturing behavior in particulate media
Assess the plausibility of using an acoustic monitoring technique to gain additional insights into the fracturing processes, and fracture geometry mapping.
A series of hydraulic fracturing tests were conducted in cohesionless, sediment-like particulate block samples. Passive and active acoustic emissions sensors were used to monitor fracture initiation and development. The results of these investigations confirm that both hydraulic fracture initiation and propagation in particulate media are associated with inelastic deformation mechanisms. We conclude that hydraulic fracturing in cohesionless particulate materials takes place in the following sequence: the pressurization of the borehole is followed by cavity expansion around the borehole; as a result of the yielding associated with cavity expansion, shear strain localization takes place; this localization manifests as one or several shear bands emanating from the expanding cavity; next, fracture initiation occurs at one of these shear bands; lastly shear bands, continuously form and branch ahead of the fracture tip as the fracture propagates. This work also demonstrated that, contrary to conventional wisdom, acoustic monitoring of hydraulic fracturing in weakly-consolidated particulate materials is not only possible, but also provides an effective technique for elucidating important insights into the fracturing processes.
