Induced Stresses Near Staged Fractures and Impacts on SRV Region in Low-permeability (Tight, Fractured and Shale) Formations

摘要

Stresses induced near a hydraulic fracture are calculated in an elastoplastic Mohr-Coulomb type formation. While an effective compressive stress increase may reduce the permeability in the formation, the induced shear stresses and dilatant zone developed can increase the stimulated reservoir volume (SRV) and the size of an enhanced permeability zone. Therefore, the induced shear stresses and dilatant zone are used in this article in order to quantify the SRV. It is emphasized that when the SRV is characterized by elastic strains then it may not be always maintained, whereas those irreversible or dilatant volumetric strains can be the key for producing economically in a low-permeability reservoir. It is suggested therefore, that a production enhancement is dominated by the cohesion and orientation of the natural fracture network and in-situ stress ratios.