What Does
Maximum Horizontal Stress Mean?
Maximum horizontal stress (sH) is an important parameter for modelling wellbore stability and drilling optimization. Maximum horizontal stress can be estimated using the extended leak off test (XLOT) with a fracture reopening test, derived from the Kirsh solution for a circular hole subjected to internal pressure. Underground formations are subjected to stress because of their confined nature.
The stresses are of three types: vertical stress, minimum horizontal stress, and maximum horizontal stress.
Trenchlesspedia Explains Maximum Horizontal Stress
Stresses in underground formations are not uniform and change in magnitude based on direction. The stresses are generally compressive, anisotropic and non-homogenous.
The magnitude of in-situ maximum horizontal stress is determined using the Kirsch equation using parameters such as minimum horizontal stress, unconfined compressive strength, borehole breakouts, friction angle, and cohesion. It can also be determined using breakdown pressure from formation XLOT test. XLOT with fracture reopening test was based on Kirsch solution for a circular hole when it is subjected to internal pressure in a medium that is isotropic, homogenous and lineraly elastic.
It is assumed that the reopening occurs when the minimum tangential stress on the borehole wall is cancelled out by fluid pressure on the borehole wall.