Hydraulic fracturing for in situ stress measurements - a simulation and experimental study

Abstract

Hydraulic fracturing is a technique which has been used largely for estimating the subsurface stress state. This technique is best applicable in low permeable formations which are ideally homogeneous and continuum. Performing an in situ hydraulic fracture test, the induced fracture tends to propagate along the direction perpendicular to the direction of least resistance stress from the wellbore. However, the stress anisotropy ratio, as well as the existence of natural fracture planes, may deviate from the results that are expected, or may indeed mislead interpretation. This concept is discussed in this paper through the results of some 2D numerical simulations and lab experiments performed under true triaxial stress conditions. The stress cell, which is capable of applying three independent stresses on a cube of rock with different sizes, was used for the purpose of the experiments. The specifications of the equipment are also described briefly.