Shale gas recovery progress part necessity, part innovation
Horizontal wells, slick-water hydraulic fracturing, longer lateral lengths and more contribute to the whirlwind of progress made in the North Texas gas play. A lot has happened in the Barnett Shale since the summer of 1982, and closing in on three decades later and 13,000 wells drilled, one thing is for certain: the learning never stops, all parties agree.
So what improvements has technology allowed?
“Every day we’re working on answering that question,” said Chesapeake Energy Corp.’s Steve Turk, vice president of operations–southern division. “We chart probably 15 different variables for each well and frac job we perform … and we look at all those variables and try to develop performance relationships for fluid volumes, sand volumes, lateral length, number of stages, rates, pressures and so on. All these things we constantly update our databases and sift through the data to find the keys to better performance on these wells.”
Looking back
“Ten years ago all we were drilling was vertical wells,” said Whitley, senior vice president–southwest at Range Resources, “then we were just beginning to make the big change that has driven not only this shale but other shales, and that is switching to slick-water fracing.”
Slick-water fracing – the addition of chemicals to, literally, make the frac fluid flow more easily – allows companies to pump fluid down the well-bore sometimes as fast as 100 barrels per minute to break up the porous shale. Before this technology, it would have been about 60 barrels per minute.
Then came horizontal drilling; while slick-water fracing had been used in 1960s East Texas, and horizontal drilling earlier in the Austin Chalk formation, it was their collective use in North Texas that made the Barnett Shale possible and economical.
Chesapeake Energy entered the Barnett Shale with its 2004 purchase of Hallwood Energy, acquiring assets in Johnson County.
“At the time, a typical well was probably somewhere – the true vertical depth was probably somewhere in the depth of 6,800 or 7,000 feet, and our lateral length, we probably averaged maybe 2,500, 2,700 or 2,800 feet,” Turk said. “In comparison, today our average lateral lengths are probably somewhere in the 3,100 to 3,500 (foot) lengths. We’ve actually drilled lengths into 10,000 feet.”
Longer laterals mean more of the Barnett Shale is exposed, and more gas recoverable. Reaching farther out, along with tighter well spacing and, now, the possibility of refracturing wells, sets the recovery bar a little higher, Whitley said.
“In the mid-’90s, we thought we’d be doing a good job if we could recover 10 percent of the gas. That’s a very low number when you’re talking about a gas reservoir, but this is an unusual reservoir. Well, it’s a source rock – we’ve turned a source rock into a reservoir,” Whitley said. Today’s goal is closer to 50 percent of gas recoverable.
Other improvements have been equally as dramatic. Whereas a frac job originally required 250,000 gallons of water and 250,000 pounds of sand, current frac jobs can use 4 million gallons of water and 4 million pounds of sand.
“What we’ve learned over time is more frac stages and a longer lateral treating more of the rock is better than fewer, bigger stages,” said Quicksilver Resources Inc. President and CEO Glenn Darden.
Across the board, more gas is being recovered more quickly and for cheaper.
Looking forward
Efficiency and progress are the natural evolution of a shale play.
“The more time you spend there, normally the better,” said Darden, whose company adheres to the attitude of ‘patience is a virtue.’
Quicksilver Resources still has about 60 percent of its overall acreage position left to be developed, providing more than a 10-year period of drilling projects at its current pace, company executives said.
“We’ll be able to truly capitalize on all the learning that has taken place over the last 20 years of companies working in the Barnett,” said Rick Buterbaugh, vice president for investor relations and corporate planning.
Whitley said the industry tends “to get a bit myopic” at times, concentrating primarily on the near-term with deferred thought for what technological advancements lurk beyond the horizon.
“Nanotechnology,” Whitley said, “which is not used in the industry to a large extent but it does have application particularly in materials.”
For example, in the future, drillers could send buckyballs – tiny molecules composed of carbon – down into the well-bore to collect and return information about what’s going on thousands of feet below ground. It’s a big step from 3D seismic technology, increasingly used today.
“Now that’s way out there, that’s like going from John Glenn flying around the Earth to astronauts on the moon,” he said, “(but) this industry is extremely good at developing new technology and applying it.”
