Stress conditions for initiation of secondary fractures from a fractured borehole

A two-dimensional elastic analysis is made of conditions for initiating, by pressurizing a jacketed borehole, secondary fractures that extend perpendicuI ar to the maximum in-situ stress, The problem is uncoupled i nto two parts, first, the tangential stress is calculated at the points of initiation of the secondary fractures as a function of borehole pressure, far-field stress, and length of the prima ry fractures, and second, the stable length of the primary fractures is calculated using I inear elastic fracture mechanics This analysis leads to a simple method for determining ω₁ provided that ω₂ and the primary and secondary breakdown pressures are known, ana does not require determination of the tensi le strength of the rock.