Fracture-Mechanics Analysis of the Breakdown Process in Minifracture or Leakoff Test

Summary The breakdown pressure—the peak pressure that is reached during pressurization of the wellbore—is interpreted in this paper to correspond to a condition of unstable crack propagation. It is shown that the classical Hubbert and Willis14 and Haimson and Fairhurst9 breakdown criteria represent a condition of fracture initiation in the limiting case of fast and slow pressurization rate, respectively; and that the breakdown pressure, pb, could be either equal to or larger than the fracture-initiation pressure, pi.