Chapter 11 - Geomechanics applications in hydraulic fracturing

Abstract

The impact of in situ stresses on hydraulic fracturing is investigated to enhance stimulation performance. The lithology-dependent stresses indicate that a shale formation has a higher minimum horizontal stress and acts as a barrier of hydraulic fracture propagation when hydraulic fracturing is performed in adjacent sandstones. However, when hydraulic fracturing is performed in a shale oil or gas formation, a stress barrier may not exist on the top or the bottom of the shale reservoir, and this will cause the hydraulic fractures to potentially grow out of the reservoir zone. Effects of the maximum and minimum horizontal stresses, shear stresses, and depletion on the fracture initiation, breakdown, propagation, and containment are investigated. Shear stresses cause hydraulic fractures kinking, and in some cases the hydraulic fractures can eventually curve to the maximum stress direction. However, the curved fractures may create frictions for the proppant transport which affect productivity adversely. It finds that depletion reduces the minimum and maximum horizontal stresses and consequently changes hydraulic fracture propagation behavior when a new well is drilled and stimulated near a production well. Fracture interference and stress shadow are also discussed.