New Ways in Understanding Borehole Breakouts and Wellbore Stability by Fracture Mechanics Based Numerical Modelling

The knowledge of stress magnitudes and orientation of principle stress axes are essential for calculating mechanical models. Our case study aims to understand the petromechanical conditions of observed borehole breakouts in 4100 m depth by developing a numerical fracture model applying the newly developed software FRACOD2D. We present the determination of the in situ stress state in 4100 m depth by using results from hydraulic stimulation, the Anderson faulting theory and Mohr-Coulomb criterion. Additionally, laboratory tests on well cores encompass the determination of fracture toughness Mode I und Mode II, the latter is based on an innovative experimental approach. The combined use of predicted stress state and geomechanical parameters including the tested parameters from core material, enabled us to calculate the initiation and propagation of analysed borehole breakouts in a testing well. The results represent a key element for future models, that will be processed in order to assess risk zones in a nearby planned well.