3 – How Do These Things Work?

In 1946, Robert McLemore was a determined man. His experience in the U.S. Army during World War II included seeing a bazooka in action and the penetrating power of the rocket’s shaped charge. This experience convinced him that shaped charges would provide a valuable (and profitable) service to the oil and gas industry. Many wells had steel casing that was cemented in the wellbore. Accessing hydrocarbon-producing layers required a device that could be lowered into the well, placed at the correct depth, and then detonated to penetrate the casing, cement, and then the formation. McLemore knew that shaped charges had the potential to achieve this.

Top Secret Technology

However, the U.S. military had classified many details about this technology as “Top Secret.” McLemore, a petroleum engineer at Well Explosives, Inc., knew that any company offering oilfield shaped charges must perform experiments and conduct firing tests to collect performance data for these devices and to safely use them. Only then could a company design and manufacture a shaped charge that worked reliably in the oil field.

Limited information about shaped charges was available to the public. Popular Science printed an article called “The Bazooka’s Grandfather” in their February 1945 issue.¹ The article provided a summary of shaped charge history and use in World War II, but it did not provide details that oilfield services companies needed to produce the devices.

Before design work could begin, some pre-conceived ideas about shaped charges needed verification. For example, many people thought shaped charges burned their way through obstacles (testing showed this was not correct).²

Several opinions existed about the effect of wellbore fluid and temperature on shaped charge penetration into the formation. Ideas about the best manufacturing methods also varied.

Added to all this was the uncertainty about events during the shaped charge detonation. The explanations of how the shaped charge liner transformed from a solid into a stream of particles were diverse and hotly debated.

Some Details Were Known

A basic shaped charge (Figure 2A) is a cylinder or cone of high explosives encased in a steel shell. One end has a conical cavity covered by a thin metal cone or “liner,” usually copper or steel. The opposite end has a detonator embedded in the explosive or attached to a booster charge.

When the detonator explodes, it discharges the booster and then the high explosives surrounding the conical liner. The explosion generates a shock wave that speeds down the cylinder at 25,000 feet per second (ft/sec), toward the cone liner. When the wave strikes the apex of the conical liner, the tremendous pressure of the wave collapses it on its axis (Figure 2B).

Because the wave pressure is approximately 15 million pounds per square inch (psi), the metal liner behaves like a fluid. The inner surface of the liner forms a narrow, high-velocity jet that shoots out of the collapsing cone at almost 30,000 ft/sec. The outer surface of the liner forms a slug or “carrot” that follows the jet.³

When the jet contacts a target (like a steel plate), the impact produces a pressure of approximately 15 million psi, exceeding the ability of the metal to hold together. The jet pushes aside the steel, forming a hole. The jet does not melt the metal.

A New Business Arrangement

Several oilfield services companies, including Well Explosives, Inc., where McLemore worked, participated in a project with the E. I. DuPont de Nemours Company (DuPont). DuPont had worked with the U.S. Army during World War II, developing explosives for shaped charges. DuPont’s expertise and the services companies’ oilfield knowledge resulted in the production of oilfield shaped charges.

A business contract for this project specified that the services companies would purchase the charges from DuPont. Designing and testing the charge carriers and producing the operation procedures were the responsibility of the services companies.⁴ This arrangement enabled McLemore’s company, and others, to offer oilfield shaped charge perforation services in 1946.

McLemore then realized his next challenge was how to announce that his company had these services and how they could increase the amount of hydrocarbons retrieved from wells.

References

1. Terry, Volta, “The Bazooka’s Grandfather,” Popular Science, February 1945. p. 65.↑
2. Robinson, Reginald L., Temperature Effect on Formation During Jet Perforating, Technical Paper submitted to the 1956 SPE Petroleum Branch Fall Meeting. p. 13.↑
3. Birkhoff, G., MacDougall, E., Pugh, E., Tayler, G., “Explosives With Lined Cavities,” Journal of Applied Physics, Vol. 19 June 1948. p. 563.↑
4. Forsyth, Val L., “Koneshot Perforating”, Tomorrow’s Tools Today, 2Q 1949. p. 33.↑

Join the Discussion!

• Do you have any information on other companies or individuals who played a key role in adapting military shaped charge technology for oil and gas applications?
• What part of the story about Robert McLemore and the development of oilfield shaped charges did you find most interesting or surprising?
• Can you share any insights on how the early testing and development of shaped charges were conducted, especially any challenges engineers faced?

I’d love to hear your perspective. Share your thoughts or answer a question in the comments below!