By Ingrid Lobet
The use of one precious fluid — water — to recover another — oil — chafes in dry country. Rivers and groundwater are receding in Texas for lack of rain and over-pumping just when the demand for water in new oil and gas fields is growing.
Now one exploration and production company in San Antonio is fracturing its wells mostly without water, using gas liquids instead, in a practice that’s beginning to spread.
Fracturing, or fracking, refers to using fluid under pressure to create fissures held open by sand. Oil or gas flow back through these channels and up through a well.
BlackBrush Oil & Gas LP is using a butane-rich mix for fracking after being confounded by many of the same obstacles other energy companies face in buying, moving and disposing of large amounts of water.
“Ranchers don’t want to give up their water,” said Jasen Walshak, production manager at BlackBrush.
The term gas liquids refers here to three fluids – propane, butane and pentane – that occur together with natural gas. They’re extracted from natural gas and sold, mostly as fuels.
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Switching to gas liquids also seems to reduce controversy for BlackBrush.
“People don’t see water transfer lines all over the place,” Walshak said, referring to the yards and miles of pipe that move water from rural wells to oilfield tanks and rig trucks.
In the U.S., oil and gas fracturing is done almost entirely with water-based fluids. Fewer than 5 percent of jobs were done with other fluids in 2012, said Mukul Sharma, a professor of petroleum engineering at the University of Texas Center for Petroleum and Geosystems Engineering.
Overall much less water is drawn for oil and gas than for agriculture or residential use, but the amounts are still significant, and they often come from places where every drop of water was spoken for before the current energy boom began.
It takes about 6 million gallons of water to fracture a well in the Eagle Ford shale, about 2.6 million gallons in the Barnett shale, and less still in some other Texas fields.
Less damage to well
BlackBrush contracts with the Canadian company that developed the method, GasFrac Energy Services. GasFrac is expanding in South Texas and now has offices in Houston and outside San Antonio.
Early in their South Texas plays, BlackBrush and GasFrac used propane purchased on the retail market. That was expensive, but they saw immediate advantages, nearly doubling initial production. They were able to use less propane, by volume, than they had water. And fracturing the formation with propane didn’t damage the formation the way water did, Walshak told a recent forum in Katy.
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On the negative side, gas liquids are less forgiving than water, and can be more expensive. Any problem that occurs during fracking requires the site to shut down.
Walshak said the company has done 20 jobs so far with the liquids. Anticipating concern over the idea of using flammable compounds to recover other flammable compounds, he said, “It is safe.” No volatile hydrocarbons are exposed to the atmosphere. A truck on site holds nitrogen to clean gas lines and send the fluids to a flare where they are burned off.
One employee is detailed full time to a thermal camera, checking for leaks. Sensitive monitors are set at strategic potential leak points. If they sense gas, “they hit a global kill,” said Dave Nicholas, frac operations manager for GasFrac, and the site is evacuated. Valves automatically open and the flare is lit. But Nicholas says that has never happened in his year and a half on the job.
The companies have experimented with a range of mixes. They tried a 50-50 mix of butane and pentane. Managers now prefer a hybrid, 60-70 percent butane and 30-40 percent “frac oil.” Frac oil can refer to a controversial oil that contains compounds harmful to people, including benzene and toluene. The frac oil they are using is green, Nicholas said, and contains none of these.
Sold after use
Forcing fuel downwell could revive the controversy over diesel fuel. Energy companies have denied using diesel as a frac fluid, but a congressional investigation found they used 10 million gallons of straight diesel between 2005 and 2009, nowhere more than in Texas.
BlackBrush and GasFrac recover their oil-butane mix when they’re done and sell it as oil. Instead paying to dispose of polluted water, they have an end product they can sell.
From a climate change perspective, fracking with butane instead of water will not have significant impact, said Barry Lefer, an atmospheric scientist at the University of Houston.
“Propane, butane, and pentane are not greenhouse gases and have relatively short atmospheric lifetimes,” he said.
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