Abstract
The growth and link-up of mini-crack initiated at perforated holes from a deviated cased wellbore were studied by analyzing the behavior of cracks in the tangent plane of the borehole. Muskhelishvili's complex potential functions were used to construct the Green's function, which related the fracture opening displacements and external loads, for computational analysis of the problem.
It was demonstrated that, at a small perforation spacing, the mini-cracks from the perforated holes will link-up forming a large fracture along the wellbore. For cased wellbores, however, the fracture opening surface is not a smooth surface and there are large amount of rock masses entrapped by the connecting cracks. A rough fracture opening area and the entrapped rock masses might be the reason for the reported high friction loss in several deviated cased wells. It was also demonstrated that the situation could be greatly improved when the wellbore was fractured at a pressure which is much higher than the breakdown pressure.
