Sleeve-fracturing limitations for measuring in situ stress in an anisotropic stress environment

In order to determine the far-field in situ stress using the sleeve-fracturing technique, two and three discrete fractures must be produced for the double-fracture and single-fracture method, respectively. Numerical modelling of the sleeve-fracturing process, using the fracture mechanics code FRANC2D/L, showed that the initiation and propagation of discrete fractures, using the single or double sleeve-fracture method, was controlled by the far-field in-plane stress ratio. The numerical modelling also provided the characteristic shapes of the pressure–displacement curves for sleeve fracturing under various boundary conditions and highlighted the difficulty of detecting the inflection points in the pressure–displacement curves for the sleeve-fracture method, a key to the successful interpretation of the in situ stress data.