The Development of Shaped Charges for Oil Well Completion

Abstract

Published in Petroleum Transactions, AIME, Volume 210, 1957, pages 11–18. Abstract A new approach to an old problem has made it possible to do in a relatively short period what has not been accomplished in the past three quarters of a century using strictly experimental methods. A theoretical study was made of the underlying principles whereby a jet is formed by a shaped charge and of the mechanism of the penetration of the target by that jet. It was found that there are more than 10, and perhaps as many as 15 variables affecting the performance of the shaped charge. Only a few calculations are necessary to show that it is physically impossible to investigate all of these variables experimentally. The shaped charge theory has been extended to include a previously littleunderstood mechanism in high explosive phenomena; namely, low order detonation. By superimposing a high order detonation on a zone already undergoing low order detonation, an appreciable improvement in performance is accomplished. The development of a design whereby these phenomena are coordinated in such a way as to develop a jet which is tailored to meet the specific target requirement will be described in detail. The shortcomings or even impossibility of strictly experimental techniques will be illustrated by a discussion of the development of a special-purpose explosive charge. Introduction In an article appearing in the May, 1888 issue of Scribner's' Magazine, Charles E. Monroe described his early experiments with gun cotton (Fig. 1) which led to his name being most frequently connected with our present-day shaped charge. Although the sunken letters or "cavities" in Monroe's gun cotton were not lined, they produced some penetration of an iron plate. The credit for the lined shaped charge, however, should rightfully go to R. W. Wood of the Physics Dept. of Johns Hopkins University, who was responsible for first discovering the fact that a metal liner in a cavity of explosive gave high velocity fragments and/or jets of metal. This discovery was made by Wood inadvertently while investigating an accidental death resulting from an electric blasting cap.