9 – Testing for Information

In 1947, Robert McLemore, an engineer at Well Explosives, Inc., faced a challenge. His company was one of many that offered shaped charge perforation services for the oil field. In such a competitive market, McLemore needed information for designing devices that would outperform the competition.

The basic problem for McLemore, and other oilfield services companies, was that shaped charges were a new and unfamiliar technology. Designing, testing, and manufacturing these devices presented significant challenges. It was common knowledge that data from many years of designing and testing shaped charges devices existed, but it was out of reach.

The E. I. DuPont de Nemours Company (DuPont) possessed vast amounts of shaped charge data. As a key supplier for the U.S. military during World War II, DuPont invested heavily in time and resources to design and test these devices. Knowledge from this effort resulted in the production of powerful shaped charges that were installed in bazooka rockets, anti-tank grenades, and other weapons (Figure 1).

After the war ended, shaped charge technology was still in use by the U.S. military. Consequently, DuPont was forced to withhold their design and test data because it was classified as Top Secret.

Many oilfield services companies, though, still benefited from purchases of DuPont’s “Standard Charge” that contained the explosive material, the liner, and the case. However, some companies saw the need to eliminate their dependency on DuPont. To achieve this, much more information was needed about shaped charge performance, and thorough testing was the way to get it.

No Testing Standards

Testing shaped charges was a challenge because no established standardized techniques existed. Consequently, oilfield services companies developed their own test procedures and the methods to interpret the test results.

Initially, most testing focused on understanding the factors that affected the jet penetration depth and hole diameter. To obtain this information, companies used several test setups. One setup placed a shaped charge on a single or multiple steel plates (Figure 2). After detonating the charge, careful measurements of the holes in the plates revealed how effectively the shaped charge jet penetrated the metal.

Another test setup placed a shaped charge inside one or more strings of casing that were embedded in cement within a steel barrel (Figure 3). This approach enabled evaluation of jet penetration on the surrounding concrete as well as the casing.

The setup for testing multiple charges was more complicated. This setup attached several test plates to a charge carrier (Figure 4). To dissipate the force of multiple charge detonations, the test apparatus was lowered into a large, water filled barrel or vat. Alternatively, the apparatus could also be submerged in water in a specially made trench.

McLemore’s tests at Well Explosives, Inc. included shaped charges of various sizes and liner materials. In an article he wrote for the December 1946 issue of The Oil and Gas Journal, he noted that charges with steel liners achieved the best penetration.¹

The reason for this, in his opinion, was that steel liners were more uniform in composition and wall thickness than softer metal liners like copper, zinc, and lead. In addition, he also noted that hard liners produced slugs. Soft liners usually did not.

Casing and Cement Damage?

As testing by oilfield services companies continued, significant concern and disagreement arose about shaped charge jets splitting casing and cracking the surrounding cement. Because companies used their own test methods, results varied greatly. Strong opinions quickly arose about the extent of the damage.

In a 1947 technical paper that McLemore submitted to the American Petroleum Institute Annual Meeting, he announced that his tests showed the charges did not split casing or shatter the cement.² Several responses were appended to the paper, including one from Norm Dorn, Chief Engineer for the Lane-Wells Company. Dorn strongly disagreed with McLemore’s assessment, claiming that his testing showed damage to the casing and cracked cement. Dorn added to the discussion by stating that wellbore fluid between the casing and the shaped charge carrier affected penetration—a fact that McLemore did not mention.

References

1. McLemore, Robert H., “Casing Perforating with Shaped Explosive Charges,” The Oil and Gas Journal, December 1946. p. 269.↑
2. McLemore Robert H., Application of the Shaped Charge Process to Petroleum Production, 27th Annual Meeting of the American Petroleum Institute, November 1947. p. 129.↑

Join the Discussion!

• Do you know of any early testing methods for shaped charges that were different from those described in the text? If so, could you share what you know?
• How do you think the introduction of shaped charges affected oilfield operations at the time?
• What challenges or advantages do you think that companies faced when adopting this technology?