The diesel engines that have provided the power for oil and gas drilling operations for years are giving way to natural gas systems that run more efficiently with fewer emissions.

“About 10 years ago, most of the well services or hydraulic fracturing operations were running on 2,500-hp diesel engines,” said Andy Publes, drilling and completion product manager for Caterpillar Oil & Gas Solutions.

Engines then began using dual-fuel technology, eventually achieving 85% diesel displacement, and the race was on.

“The market focus on burning low-cost natural gas continued to become more and more intense,” Publes said. “That’s where the e-frac became such an important part of the technology for well service application, just because it allowed people to connect 100% natural gas genset to create electricity and power the rest of the electrical components to create hydraulic horsepower.”

Caterpillar’s entry in the competition is the Gas Mechanical System, an integrated power solution designed to simplify frac operations that uses 100% natural gas. Natural gas systems have been redesigned to overcome the limitations that previously made them a poor choice for drillers, Publes said.

“This system has been engineered from the ground up specifically for pressure pumping operations,” he said. “It is using two components that our customers are very familiar with”—the G-3520 engine with 3,600 hp, and the TH55G-E90 transmission, which have both logged millions of hours in the field.

“We built a G-3520 specifically for this application, the direct drive,” he said. “And then we leveraged the TH55 transmission and made modifications in the hardware and the software.”

The system designers focused on three goals, Publes said.

  • Mechanical efficiency: “The amount of fuel that is needed to create hydraulic horsepower is streamlined and optimized, so you’re spending less fuel to produce horsepower.”
  • Power density: “We’re producing 3,600 hp from a single trailer, which allows the customer to have a smaller site footprint.”
  • Reliability: “We focus a lot on [that] and reducing the number of components that the customer has on site. Just having a traditional engine transmission and pump reduces the number of failure points.”

Caterpillar started with a technology demonstrator model. “Basically build something quick and take it to the field and fail fast and see where the weakest links are,” Publes said. In this case, the model ran for 1,000 hours without any major issues. The product is still in development but customers have been pleased, he said.

Current field testing in the Permian Basin has shown the GMS delivering up to 13 bbl/minute, while sustaining over 20 pumping hours per day. The GMS will continue to be tested across major North American basins.

Operators now insist on using natural gas to power more sophisticated drilling—simul-fracs and trimul-fracs.

“When you look at a site running for a full year, those are millions of dollars of savings,” Publes said. “The secondary reason to move toward 100% natural gas is the ability to reduce your GHG emission impact. And power density is key to being able to keep your pad size as low as possible.”

Publes has seen the business of well services shift from “growth mode” to “industrialization mode” in his time with Caterpillar.

“We’re now trying to see how we can optimize the operations and leverage the resources that are around us,” he said. “We have those transformations in different industries like mining and construction, and we’re excited to be part of the transformation within oil and gas.”

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