For industry and government officials in North Dakota hungry for new ways to reduce the nearly 30% of the state’s associated natural gas that is flared, it is unclear if an innovative approach from a Louisiana-based oil/gas field services firm using converted military helicopter jet engines will prove to be a panacea anytime soon.
Company officials at Green Field Energy Services (GFES) told NGI’s Shale Daily Monday that they are just starting to use natural gas to power the converted helicopter engines for hydraulic fracturing (fracking). The bulk of the 70 engines now operating in various oil/gas fields are running on diesel and are located mostly in Texas, a company official said.
Fracking experts in North Dakota separately have said that for the associated gas in the Bakken a substantial treatment facility would have to be at the well site to allow the gas to be clean enough to be used in the fracking operations. Therefore, they see more applicability in dry gas fields.
The Niobrara formation in Colorado and other areas where they have dry gas, the emphasize is still on oil, so that would work against this natural gas-fired jet engine option, too, said a 30-year fracking veteran in fields from Colorado, Wyoming, Montana and North Dakota.
With $100 million in funding support from a unit of Royal Dutch Shell plc, privately held Lafayette, LA-based GFES confirmed earlier this month that it may have found a low-cost power source for fracking equipment in used military jet engines that can run on natural gas (see Shale Daily, April 5). GFES has 70 units in the field powering fracking pumps and plans to add more as the used engines come on the market.
It began this transformation with engineering help from units at General Electric about two years ago, and it is looking to add a lot more units, the Lafayette-based official said Monday.
“Jet engines generally are not very tolerant of large variations in gas quality [as found with most associated, wet gas],” said Monte Besler, a Williston, ND-based founder/consultant at Fracn8r (frack-en-ator). “So, if they are moving from job site to job site, they would have difficulty controlling the horsepower output and the pollution control in working with wet gases.
“You can send the gas at the well site through a separator, but if there are any butanes, propanes, or anything like that, the energy density of that gas is going to be a lot higher.”
What about the purported big cost-savings potential from these engines?
“Definitely, if you can use the gas at the wellhead. It would be wonderful if you could do it up here [North Dakota and Montana] because right now we flare a substantial amount of gas because we don’t have the capacity to have pipelined out yet.”
Besler said it also would make a difference whether the former helicopter engines were hooked directly to fracking pumps or used with the gas producing on-site electricity to run the pumps on electricity.
“One of the problems that gas turbines have is that while they deliver a lot of power they have a high optimum rpm [revolutions-per-minute] range and if you operated outside that range that can be tough, and they needed to be geared down to run fracking pumps,” said Besler. He said jet engines were applied to fracking as far back as the 1970s and early 80s, but abandoned because they had to operate at such a high, narrow rpm range.
In addition, back then the turbines were “incredibly loud” as well, he said. “Of course, those were not natural gas-fired.”
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