Fig 1
Magnitudes of horizontal stresses at the top of reservoir layer 1 based on Coulomb faulting theory and Anderson’s classification of faults. Permissible stress ranges highlighted in red correspond to the case of breakouts occurrence in layers with rock strength C=40-50 MPa, and an absence of tensile fractures. (The red lines outline the stress conditions for borehole breakouts formation, the green line corresponds to the criterion for occurrence of drilling induced tensile fractures for zero tensile strength. The blue polygon indicates limits of Mohr–Coulomb failure for frictional equilibrium of pre-existing faults. Three regions separated by the blue lines correspond to normal faulting (NF), strike-slip faulting (SS) and reverse faulting (RF) stress conditions.)