Changing stress can affect the ability of fluid to flow along mechanical discontinuities such as faults, fractures, or bedding planes. Stress can cause mechanical discontinuity to reactivate in shear, resulting in an increase in fluid flow. The values for present-day horizontal stress orientation and magnitude can be constrained from structural geology principles via interpretation of mapped active features and wellbore information such as drilling history and image logs. Stress magnitudes and orientation information is used to calculate the shear and normal stress magnitudes acting on the mechanical discontinuities of all possible orientations. Furthermore, the necessary magnitudes of fluid pressure within each mechanical discontinuity that would be required to encourage shear failure reactivation are evaluated.

A laboratory experiment and an example from the Barnett Shale play are presented as an application of the method. The Barnett example identifies likely orientations of pre-existing fractures that could interact with fluids during hydraulic fracture stimulation.