Estimating in situ stress based on hydraulic fracturing data typically depends on interpretation of the breakdown, secondary breakdown ('reopening') and shut-in pressure. While it has been recognized that the near-wellbore stress field should be taken into account and that the compressibility of the injection system and the viscous flow of the fluid can diminish the accuracy of stress estimates, these issues have not been well quantified. A coupled numerical model that includes the compressibility of the injection system and the flow of a viscous fluid in a plane-strain hydraulic fracture extending from a wellbore, in an impermeable rock, and in the presence of a non-isotropic in situ stress field provides a basic tool for estimating the order of the error associated with hydraulic fracturing stress measurements under nonideal conditions. The main findings of this work are model-based guidelines on the values of relevant dimensionless parameter groups to ensure sufficient accuracy of stress estimates that use idealized models. When these guidelines cannot be met under field conditions, the model can be further applied to obtain first-order corrections that account for compressibility, viscosity and near-wellbore effects.
- Fracture and flow
- Numerical solutions