Hydraulic Fracturing for Rock Stress Determination
The hydraulic fracturing technique may be used to determine the in-situ rock stress in a
plane perpendicular to borehole. This is done by application of fluid pressure (normally
water) in a test section in a borehole isolated by packers until the rock fails in tension.
The fluid pressures required to generate, propagate, sustain and reopen tensile fractures
in the rock are recorded as function of time, and these may be related to magnitude of
the existing stress field. Directions of measured stress are normally achieved by
observing and measuring the orientation of the hydraulically induced fracture plane by
the use of a so-called impression packer. The induced hydro fracture is oriented parallel
with the major secondary principal stress 0H in a plane perpendicular to the borehole.