What Does Minimum Horizontal Stress (SH) Mean?
Minimum horizontal stress (sh) is one of the principle stresses that confined underground formations are subjected to. The other stresses are the vertical stress and the maximum horizontal stress. Hydraulic fracture propagates perpendicular to the minimum principle stress. Minimum horizontal stress is estimated using poroelastic theory.
Stresses in underground formations are not uniform and change in magnitude based on direction. The stresses are generally compressive, anisotropic and non-homogenous.
Trenchlesspedia Explains Minimum Horizontal Stress (SH)
Many horizontal wells are drilled in the direction parallel to the minimum horizontal stress in the formation, allowing for multiple transverse fractures that are created hydraulically and enhance production. When the pressure in the fracture is less than the fracture closure pressure, the fracture closes. Hydraulic fractures propagate perpendicular to the least principle stress, which in some formations is the overburden stress, resulting in a hydraulic fracture in the horizontal direction.
In very deep reservoirs, the least principle stress will mostly be horizontal, creating a vertical hydraulic fracture. Minimum horizontal stress changes with depth due to the pore fluid pressure in the vertical direction, and rock lithology. This stress can be measured by acoustic log data analysis or diagnostic fracture testing.