In 1951, Henry Mohaupt will apply for a U.S. patent for his “Shaped Charge Assembly and Gun,” based on World War II anti-tank technology he patented a decade earlier – a conically hollowed out explosive fired from bazookas.

Cement casing, developed in 1919 by Erle P. Halliburton’s New Method Oil Well Cementing Company, Duncan, Oklahoma, isolates wellbore zones and guards against collapse.

But far down the borehole, a newly completed well’s cemented casing stands between the petroleum company’s massive investment and the production of oil or gas.

In the early days of well “perforating” technology, a variety of mechanical means of penetrating casings were used.

A 1902 invention used a scissors-like expanding mechanism to drive and then retract “perforating levers” through the casing.

The U.S. Patent Office records many technologies designed to solve the problem of safely perforating well casing. In 1902, one invention (Patent No. 702,128) relied upon a scissors-like expanding mechanism to drive and then retract “perforating levers” through the casing.

The 1930s brought various downhole “guns” that shot steel-jacketed bullets through casing and about a foot into the producing formation.

By the 1930s, “bullet” devices using projectiles – usually steel bullets – would become the most popular among oilmen.

“A device for perforating casing after it has been installed in a well” is designed by Ira J. McCullough of Los Angeles. His April 18, 1939, invention fired downhole projectiles to increase a well’s production.

McCullough received two patents for his multiple bullet-shot casing perforator and mechanical firing system. The innovations, a technology that simultaneously fires charges at several depths, will help improve well production.

“It is the object of my invention to provide a device for perforating a well after the casing has been installed in the well in which there is plurality of projectiles, each of which is adapted to be propelled by the burning of a separate charge of powder,” McCullough reports.

“The charges of powder are simultaneously ignited in order that all of the projectiles will be shot or projected from the apparatus at substantially the same time and with ample force and velocity to penetrate a plurality of casings and intervening walls of cement,” he explains.

McCullough’s device (patent no. 2155322) also included a “disconnectable means” that – once the charges are lowered into the borehole – can render percussion inoperative as “a safeguard against accidental or inadvertent operation.”

The First Perforating Guns

“Across America were numerous cased wells which produced poorly or not at all. Various methods had been tried to get at the oil-bearing formations in these wells – with little success,” notes Noel Atzmiller of Baker Atlas Corporation, Houston.

“A new and effective method of casing perforation was needed, one that could accurately reach the profitable strata without splitting the casing or breaking the cement-to-casing bonds,” he adds in a 1977 article. In 1930, two enterprising oilfield tool salesmen, Bill Lane and Walt Wells, came up with the idea of using guns to get the oil.

Although not a “machine gun” as noted in this August 1938 Popular Science Monthly article, vital production technologies provide explosive energy to cut through casing and strata – and produce petroleum.

The two inventors envisioned a tool which would shoot steel bullets through casing and into the formation.

After many tests, the two men created a multiple-shot perforator which fired bullets individually by electrical detonation of the powder charges.

“By late 1935 Lane-Wells had a small fleet of trucks, and the company was growing rapidly into being the leading provider of well-perforation technology,” Atzmiller concludes.

Meanwhile, improved drilling methods made deeper wells possible.

An August 1938 Popular Science Monthly article describes exploration and production technologies used for “the deepest hole man has ever made in the crust of the earth” – a 15,000-foot well in Wasco, California.

“Apparently the well had just missed an oil pool, blocked off from it by a formation impervious to oil,” notes the article.

At this point, another of the latest scientific aids to oil men, the “underground machine gun,” was called into play.

Down the well on the end of a cable went a torpedo-shaped cylinder of steel, studded with recessed knobs along its outer shell. Each knob formed the barrel of a pistol.

As the device reached the 13,100-foot level, a thousand feet below the former world’s deepest “producer,” an operator at the surface closed an electric switch.

Slugs of solid steel punctured the well casing and ripped through the surrounding sand. As if released from a bullet riddled tank, oil gushed through the holes and up the pipe…

Inventors continue to scramble and multiple gun barrel type devices assume many forms as the problems of control and “sanding up” of the producing strata are challenged.

Solutions will come from battlefields.

Bazooka Technology

The tank was a new and terrible weapon during World War I.

Improved perforating technology evolves from the rocket grenade used in the Army’s M1A1 “bazooka.”

Attacks on infantry positions produced chaos. By the 1930s, further advancements in German armor had military planners in England and France scrambling to develop a counter weapon.

Henry Mohaupt’s revolutionary idea was to use a conically hollowed-out explosive charge to direct and focus the detonation’s energy.

Swiss Army veteran and chemical engineer Henry Mohaupt brought his research to America, where the U.S. Army’s Ordnance Department put him in charge of its secret program to develop an anti-tank weapon.

Mohaupt’s idea for using a conically hollowed-out explosive charge to direct and focus the detonation’s energy ultimately produced a rocket grenade used in the Army’s 60-millimeter, M1A1 Rocket Launcher – the GI’s bazooka.

After the war, the industrial potential of shaped charges prompted a Fort Worth, Texas, company, Well Explosives Company, to recruit Mohaupt. His September 24, 1951, patent submission for a “Shaped Charge Assembly and Gun” brought bazooka technology to the oilfield.

Almost any drilling process will create some damage to the formation adjacent to the wellbore, explains Schlumberger, an oilfield service company founded in 1926. Bypassing the damage is a key objective when perforating.

“This invention relates to improvements in means for perforating casing in wells and for perforating and fracturing earth formations around well bores,” Mohaupt explained in his patent application for the new downhole technology.

Focused explosive energy easily cut through casing and strata. In the coming years, Welex Jet Services (formerly Well Explosives Company), DuPont and others continued to explore these opportunities.

Inventors scrambled and multiple gun barrel type devices assumed many forms to solve the problems of control and “sanding up” of the casing.

Today, petroleum industry R&D creates technologies to go safer and deeper into tighter zones and more sensitive environments than ever before.

A new generation of patents reflects the demands of higher down hole pressures and other challenges for meeting America’s energy needs.

Editor’s Note – Read Noel Atzmiller’s article about the gun perforator, “Shooting through Steel and Rock,” in the August 2007 Hart’s E&P magazine.

To learn more about the evolution of technologies for increasing oil and natural gas production, also see “Shooters — A ‘Fracking’ History.”

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