New Perforation Gun Design Tests the Value of Simplicity

Image courtesy of Hunting Energy Services.
Hunting’s new perforation gun system is controlled by the initiation cartridge (4). That unit is screwed into a baffle (2)at the end of the carrier tube (1), positioning it to detonate explosives in the charge tube (3). The cable around the tube acts as the fuse.

Price competition among makers of perforating guns has gotten brutal, even by the rough standards of unconventional oil business where depressed oil prices have led to deep budget cuts.

One sign of the times is the sharp decline in the average amount paid to run a group of perforating guns into a well to blast open the rock for a single fracturing stage.

“The rate paid has dropped 60% over the past 18 months,” said James Cole, product line manager at Hunting Titan, one of the largest makers of the downhole systems used to perforate the reservoir before fracturing. “They are not making much profit.”

For Hunting, the rate drop adds to the challenge of launching a total redesign of its perforating gun system, which was conceived when the economics of the business looked brighter.

The finished gun and detonation unit, called the ControlFire system, is billed by the company as its biggest design change in decades. From the outside, it does not look so different. Some of the biggest changes are that components have been removed.

Shaped charges are still inset in sockets in a steel pipe—the charge tube—housed in a carrier. What is missing in the new design is the connector sub—a short section of pipe connecting the guns that holds the detonator and control switch.

The new design squeezes those parts into a compact, sealed unit—the initiation cartridge—which is installed by screwing it into a baffle at the end of the carrier. Eliminating the connector results in a small reduction in the length of the tool string. The design reduces costs by:

  • Eliminating the time spent cleaning and preparing connectors between uses.
  • Reducing the risk of a misfire, because the preassembled component limits the risk of a gun failing to detonate. When a gun fails to fire, it requires hours to pull it out and fix the problem.

Those savings are due to the biggest change in the design—no wiring is required in the field. The only remaining wires are in the sealed initiation cartridge.

This cartridge, which is destroyed when the charges go off, costs somewhat more than a reusable connector sub. Cole said the company’s customers have long asked for a one-time use unit because of the expenses and problems associated with reuse.

After each job, carbon residue must be removed with solvents, such as diesel. That task requires about 9 minutes per connector, but with fracturing jobs often requiring 150 subs, the total hours add up, said Josh Howk, North America technical manager at Hunting Titan, who has played a key role in the development team.

Each time a sub is used, wiring connections must be made to put in a new detonator, and the technician must ensure that the other connections are good. Based on customer feedback, the company estimates that more than 85% of the time lost during perforating is caused by a wiring malfunction, which is often a result of human error.

As a result, Rick Bradley, president of Hunting Titan, asked for ways to get rid of the wires. An outpouring of ideas from a handful of employees in the technical services group led to the creation of a small team that redesigned the system.

Rather than using wires to connect the perforating guns to the fire control panel, they used the metal charge tube to conduct electrical signals from gun to gun.

Eliminating the connectors required tapering the ends of the casing so they could connect with other industry-standard-size guns. The ­method used to do that came from Bradley, who used his knowledge of metal working to help in its manufacture.

But, the patented design also limits its compatibility. The cartridge can only be used in Hunting’s new H1 gun system, Cole said.

The company is working on resolving some final issues and hopes to field test it later this year.

New Perforation Gun Design Tests the Value of Simplicity

Stephen Rassenfoss, JPT Emerging Technology Senior Editor

01 July 2015

Volume: 67 | Issue: 7