A computational procedure is developed for solving the problem of a circular hydraulic fracture propagating under the action of frac-fluid being pumped in at a central wellbore. The crack is modelled as continuous distributions of ring dislocations and the resulting elasticity singular integral equation is solved numerically. The fluid flow equations are approximated by local and global interpolation finite difference schemes. The coupling between elasticity and fluid flow is handled numerically, by two different algorithms: one iterates on crack tip velocity whereas the other varies the time step size until it agrees with the chosen increment in crack length. Sample results are given; it is found that the velocity algorithm is computationally more efficient and more stable. The model allows detailed tracing of pressure distribution and fluid flow in the fracture, even under complex conditions of cyclic injection and fluid rheology. It may serve as a stand-alone model of (horizontal) hydrafracs-especially at shallow depths-or it may be used as a reference frame to test the various numerical formulations/algorithms required for the ongoing development of a fully 3-D hydrafrac simulator.
studies were provided in early reports,4*' but this paper proceeds to the integrated final model capability.
A typical cross-section of the circular hydrafrac is shown in Figure . It consists of three regions: borehole, fluid-penetrated and non-penetrated regions. The dominant equations required are