Prior to perforation technology, wells were "open hole" or "shot hole" (barefoot) completions, sometimes employing liners. But the perforated casing completion was an important and necessary development as wells got deeper, and reservoir conditions became more and more complex. The first mechanical perforator was patented in 1910; there were later improvements, but the depth of the perforation was limited (years later there was brief experimentation with hydraulic punch perforators and even twist drill perforators). Gun perforators have been successfully used as a well completion method since at least 1927; the first patent was 1926, but it did not work. Early gun perforators were "bullet" devices, utilizing actual projectiles (usually steel bullets) to penetrate the well casing. Prior to the introduction of lined shaped charge perforators, almost all research emphasis was placed on increasing the depth of bullet penetration. The lined shaped charge perforator a/k/a the jet perforator or jet charge has displaced the old bullet perforators (nearly to extinction), and this is the story of their development.|
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In January, 1945, Ramsey C. Armstrong founded Well Explosives Company, Inc. in Fort Worth, Texas. Armstrong had acquired an exploding bullet patent, but it did not work. Robert "Bob" McLemore, a petroleum engineer just discharged from the army, and Eugene Tolson joined the company. They decided to pursue perforating technology related to the bazooka, an anti-tank device based on the shaped charge concept. As a result of placing ads in newspapers in areas where DuPont, maker of the explosive end of the bazooka, had manufacturing plants, an applicant mentioned Henry Mohaupt, the inventor of the lined shaped charge. Armstrong contacted Mohaupt in Washington, DC, where he was then working for the Navy, and in October of 1946, Mohaupt and his wife made the long drive from Washington to Fort Worth. Mohaupt was originally promised 50 shares (out of 20,000) of the company; he was later made a full partner.
But we must journey back in time to get the complete story. In 1935, Henry Mohaupt, a chemical engineer, was a machine gunner in the Swiss Army getting ready for WW II. He was disturbed by the ineffectiveness of anti-tank weapons under development. He established a laboratory in Zurich to develop an effective anti-tank weapon that could be used by the infantry soldier. The starting point was the Monroe Effect (1885), where a high explosive with a cavity facing a target leaves an indentation. The Monroe Effect was rediscovered by Von Neumann in 1911, but no practical applications were developed (actually the earliest known reference to the effect appears to be 1792, and there is some indication that mining engineers may have exploited the phenomenon over 150 years ago). In his research, Mohaupt noted that strange things happened when he tried to propel metal discs with conically hollowed out explosive charges. This led him to place a steel cone in the hollowed out explosive; when this device was moved away from the target, no fragmentation of the metal cone occurred, and a narrow hole in the target was created, a hole much deeper than the diameter of the cone (one account mentions earlier work by R.W. Wood of the John Hopkins University Physics Department, saying he discovered the metal liner principle).
Needless to say, development of lined shape charges from 1935-1939 was driven by the need for a workable anti-tank weapon. The British, and the French (assisted by Mohaupt) each started their own research programs after early demonstrations in Switzerland and France generated interest. With conditions deteriorating, the French furnished their secret research to the United States. After the real war started on May 10, 1940, Mohaupt was asked to come to the United States. In October, 1940, after delays because he was not an American citizen, he arrived in the United States and took over direction of the bazooka project. The program was made a high priority and labeled "secret" on June 4, 1941, after a previously skeptical US Ordnance Department finally recognized the significance of Mohaupt's research. Because Mohaupt was an alien, he was thereafter excluded from direct contact with the program, and he assumed a distant advisory role. Later, he joined the army and returned to DuPont on his army assignment. The bazooka was first used in the North African theatre of war, and allowed a foot soldier to stop a tank! Mohaupt filed for US patents in June 1941 (he had done so in Europe before leaving). Mohaupt was briefly pursued by the US Justice Department for violations of the War Secrets Act, but the charges were found to have no merit (what a wonderful way to repay this man for his contributions to the war effort). After the war ended, Mohaupt married and went back to Europe, and upon his return to the US, went to work for the Navy.
Work began at Well Explosives Company, Inc. (in 1948, the name was legally changed to Welex Jet Services, Inc. to avoid the word "explosives"). Money was in such short supply that the first copper cones or liners, reportedly 800, were made by hand. Stanolind Oil and Gas Company sponsored a series of laboratory tests, but no commercial sales were developed.
Byron-Jackson Company (BJ) and Armstrong happened to share the same patent attorney, and a deal was struck after a demonstration of the shaped charges perforating pipe in a canyon near Pasadena. BJ financed further research with about $20,000.00 per month, plus a laboratory and other help, for 50% of the patent rights. Dr. Clyde Davis and Dr. Walter Lawson, the DuPont researchers that began work before Mohaupt arrived in the United States (Mohaupt's French army assistant had preceded him while he was detained in Europe), had also filed for patents on shaped charge technology, but they omitted the liner. Mohaupt's participation, and BJ's money, secured an exclusive license from DuPont.
Next a suitable carrier had to be devised. Softer steels were exhibiting swelling that could cause a gun to become lodged in the well, but if the metal was too hard, it shattered. With a February, 1947 trip to California, McLemore, Tolson, and Mohaupt found a suitable compromise in Timken steel. In September, 1947, they returned to Fort Worth with a working gun, and continued improvements at the Fort Worth facility.
Licenses were issued through BJ; the first licensee was Perforating Guns. After industry resistance, licensing was no longer offered on a selective basis, but was offered to anyone and everyone. All of the major perforating companies soon took out licenses for lined shaped charges, because of the success of the devices. DuPont manufactured the actual shaped charges. In 1955, Jet Research Center (JRC) was formed as a joint venture between BJ and Welex to manufacture perforating charges and do further research. In 1957, Halliburton acquired Welex in what was a terrible merger. When the patents expired in 1961, BJ pulled out of JRC. Mohaupt sold his interest in Welex in 1954, and went on to develop other explosive applications, including StressFrac (see our page Propellant Type HEGF Devices). In early 1999, Halliburton resurrected JRC as a supplier of perforating charges to the independent wireline industry, a nice gesture after closing the doors at MLS; a deed that earned them the nickname "jerks" around here (see our page A Brief Opinionated History of Logging Equipment Manufacturers).
Gearhart-Owen (GO) had difficulty obtaining a license to buy shaped charges. As a result, they could not purchase supplies, like liners, charges, etc. GO believed the denial was trade constraint, while the other side alleged GO lacked the financial strength to afford a license. Welex sued GO alleging trade secret theft (Owen had been Chief Explosives Engineer at Welex). GO responded with two lawsuits of its own. The judge finally ruled in GO's favor in 1962, but only after the Justice Department stepped in and eased the apparent constraint of trade. But being forced to manufacture their own perforating charges was good for GO, as they eventually grew to be the largest supplier of jet charges in the world. The Perforating Supply Company was formed as a subsidiary of GO, and willingly sold perforating supplies to independent wireline companies. Independent perforating companies could now be formed as there was finally a source for materials. Over a period of six years, 200 perforating companies were started, with GO providing technical aid to all, and financial aid to many.
Today, there are several viable suppliers of lined shaped charge perforators to the independent wireline industry.
This page would not have been possible without the unique effort of Dr. Douglas W. Hilchie in his book Wireline - A History of the Well Logging and Perforating Business in the Oil Fields, Douglas W. Hilchie, Inc., Boulder, Colorado, 1990.
Exercise extreme caution when working with explosives. Stay alert and THINK; complacency kills! Follow the guidelines in the American Petroleum Institute (API) Recommended Practices for Oilfield Explosives Safety, RP 67.