Hydraulic Fracturing in Transverse Isotropic Media - A Theoretical Framework
Résumé
Predicting fractures in rocks is one of the most important issues in reservoir engineering for enhancing oil and gas production from low permeable reservoirs and unconventional formations. This work discusses a theoretical framework for predicting fractures through time and space during a stimulation hydraulic fracturing test in anisotropic medium. Special attention focuses on transverse isotropic medium. It applies the poroelastic theory coupled to the Mohr-Coulomb and Griffith failure theory for predicting the fractures orientation against distance from the injection well. A dimensionless failure criterion written in matrix form including principal stresses tensor and elastic rock properties is proposed. It includes the Mohr-Coulomb, Griffith, fractures reactivation and hydraulic fracturing. This formulation is used together with a generalized Hubbert-Willis formula to estimate the critical fracking pressure to be applied at the well head. Analytical expressions are given to predict the propagation of the fracking front through time and space apart from the stimulation well. This formulation, implemented in the Gocad geo-modeler workflow, is applied on a synthetic reservoir case-study to illustrate the concept and discuss the advantages and limitations of the suggested approach.