In the debate over hydraulic fracturing for natural gas, two facts are beyond dispute: huge amounts of water are used to break up gas-bearing rock deep underground and huge amounts of polluted water are returned to the surface after the process is complete.
Tainted with chemicals, salts and even mild radioactivity, such water, when mishandled, has damaged the environment and threatened drinking water, helping fuel heated debate over whether gas drilling is worth its risk to drinking water, rivers and streams.
Now, an emerging technology developed in Canada does away with the need for water. Instead, it relies on a thick gel made from propane, a widely available gas used by anyone who has fired up a backyard barbecue.
Called liquefied propane gas (LPG) fracturing, or simply ”gas fracking”, the waterless method was developed by a small Canadian energy company, GasFrac.
Still awaiting a patent in the US, the technique has been used about 1000 times since 2008, mainly in gas wells in the Canadian provinces of Alberta, British Columbia and New Brunswick and a smaller handful of test wells in Texas, Pennsylvania, Colorado, Oklahoma and New Mexico, according to GasFrac chief technology officer Robert Lestz.
Like water, propane gel is pumped into deep shale formations 1600 metres or more underground, creating immense pressure that cracks rocks to free trapped natural gas bubbles.
Like water, the gel also carries small particles of sand or man-made material – known as proppant – that are forced into cracks to hold them open so the gas can flow out.
Unlike water, the gel does a kind of disappearing act underground. It reverts to vapour due to pressure and heat, then returns to the surface – along with the natural gas – for collection, possible reuse and ultimate resale. And also unlike water, propane does not carry back to the surface drilling chemicals, ancient seabed salts and underground radioactivity. ”We leave the nasties in the ground, where they belong,” Mr Lestz said.
David Burnett, a professor of petroleum engineering at Texas A&M University, said fracking with propane made sense. ”From a reservoir engineering perspective, there is no reason this would not be effective,” he said.
Burnett said using gas instead of water can serve two ends—protecting the environment and reducing costs to the drilling industry of handling and disposing of tainted water.
But he said propane fracturing is “not a game changer,” at least not yet.
“This is a very conservative industry,” Burnett said. “Engineers want to see what someone else did first, and they want the data.” Most companies that have tried the GasFrac technique have not published data publicly, he said, possibly out of fear of tipping off potential competitors to its benefits.