Abstract

Oil and gas well completion and stimulation can be accomplished by the use of bullet impact or the impact resulting from a shaped-charge jet. Jet penetration can have the distinct advantage of leaving a clean and unobstructed hole. The phenomena associated with charge liner collapse are generally understood. The target response to the action of the jet and the resulting fractures are areas which required more research.

A high speed Cordin Framing Camera was used to photograph the jet penetration and fracture formation in models made from Plexiglas. The jet penetration rate, fracture orientation, and Plexiglas. The jet penetration rate, fracture orientation, and radial fracture propagation velocity could be determined with the use of this technique. In addition to Plexiglas, the fracture phenomena in rock under standard temperature and pressure phenomena in rock under standard temperature and pressure conditions were investigated by the authors.

During the jet penetration process, the compressive wave pulse will decrease in magnitude and the manner of failure in the pulse will decrease in magnitude and the manner of failure in the target material will change as the distance from the jet axis increases. Distinct zones of failure are formed concentrically around the jet penetration axis: plastic zone, zone of small radial fractures, zone of large fractures. An understanding of the origin of the fracture zones and their time of formation in relation to detonation is necessary before shaped charges can be more efficiently used for well completion.

The liner angle in the charge and the material of which the liner is constructed has been shown to influence the depth of jet penetration. Little has been published about the fracture penetration. Little has been published about the fracture phenomena in brittle targets resulting from the impact of jets of phenomena in brittle targets resulting from the impact of jets of different compositions and shaped-charge liner angles. The results of this study indicate that fracture orientation and propagation are not only a function of the charge geometry but also propagation are not only a function of the charge geometry but also a function of some physical characteristics of the target material.

Introduction

The May, 1888 issue of "Scribners Magazine" contained an article written by Charles E. Monroe describing his experiments with gun cotton. His experiment proved that the energy of an explosive could be concentrated by changing the geometry of an explosive charge. Cavities carved into gun cotton in the form of letters of the alphabet resulted, after detonation, in the mirror image of these letters being sunken into steel blocks. This cavity effect is known in the United States and England as the Monroe effect.

The lined cavity effect was discovered by accident in 1936 by R. W. Woods at the Physics Dept. of John Hopkins University. During the investigation of an accidental death caused by a blasting cap, Woods found that the dimple in the base of the cap extruded a jet of high velocity copper particles.

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