A combined testing and modeling program has been completed with the purpose of providing systematic observations and models of the pulse fracturing process. Approximately eighty individual laboratory tests have been successfully carried out in blocks of scaled rock simulant loaded to a true three-dimension stress state with miniature propellant/explosive charges in a wellbore as the fracturing energy source. Real-time borehole pulse pressure measurements were also obtained. Mathematical models developed include descriptions of borehole pressurization, flaw initiation, gas-driven fracture propagation, and fracture arrest. Measurable material and natural parameters such as moduli, gas permeability, and in situ stress are used in the models. Models include true crack-crack interaction. One of the models is fully two-dimensional and includes fracture curvature in an anisotropic stress field. Results indicate that multiple fractures are created over a broader range of source, material, and natural conditions than had commonly been thought before, but that the conditions conducive to extremely long fracture extension, usually considered desirable, are somewhat difficult to establish and maintain. Several approaches to optimizing and evaluating the process in the field are suggested, including a possible approach to the generation of long fractures. A field test observation is described.

You can access this article if you purchase or spend a download.