Hydraulic fracturing is performed to determine the magnitude and direction of the in-situ stress in the process of fluid pumping with an injection rate into a cavity hole that then leads to an increase in pressure and formation of tensile fracturing in the cylinder wall. Breakdown pressure is defined as the wellbore pressure when inducing hydraulic fracturing.

In principle, thick walled hollow cylinder samples are used to perform hydraulic fracturing tests. Specimens are placed in a triaxial cell and subjected to the predetermined stress condition in terms of confining pressure (related to uniform horizontal stress), vertical stress (over-burden stress) and pore pressure. Injecting a constant flow rate into the cavity hole pressurizes the specimen. Simultaneously the volume change of the cavity hole corresponding to the injection pressure is measured. Fluid injection is continued until peak pres-sure is reached.

The hydraulic fracturing fixture can be added to all series of rock triaxial test systems manufactured by our company. A high-pressure intensifier with the required pressure and volume needs to be added to the main system. In combination with these fixtures and our rock testing systems, the user is able to run tests and study the hydraulic fracture initiation and propagation.