Horizontal drilling and hydraulic fracturing often are credited with sparking the country's ongoing shale revolution, but that brief description doesn't tell the whole story.
Until the past decade, most oil wells have been drilled vertically, targeting a patch of sandstone or some other soft rock that acts like a sponge and absorbs oil and natural gas.
With horizontal drilling, operators punch a traditional vertical hole up to a mile or two deep before angling the pipe so that it creates a horizontal section that can stretch up to another couple miles.
Horizontal and angled drilling have been used in various forms for at least half a century.
Hydraulic fracturing — or fracking — is the process of cracking a rock layer deep below ground to allow the oil and natural gas to flow into a well more easily.
While fracking has received much attention lately, the process is not new. Operators have been fracking wells throughout Oklahoma for decades.
So what's different?
What has unlocked the shale oil and natural gas boom is multistage fracking along horizontal well segments, Tulsa oilman George Kaiser said this week at the University of Oklahoma Energy Symposium.
“In the past, you put pipe in the hole, shoved hydraulic treatment in it and hoped it went in the right space. You typically got one or two of your segments treated,” said Kaiser, chairman of Kaiser-Francis Oil Co.
“Now we're drilling 12 to 48 segments. You can separate the segments with cement or a plugger and treat each separate section and in effect have 12 to 48 well bores.”
As a result, producers can recover far more oil and natural gas than previously possible at a relatively low cost.
“At three times the cost, you can drill the equivalent of 12 to 48 wells,” Kaiser said.
Along with better drilling techniques, technology also has helped producers more accurately find the oil in the ground.
“Real-time geophysics is what has really changed the game,” said Mark Mills, CEO at Digital Power and a senior fellow at the Manhattan Institute. “You couldn't do that before.”
Three-dimensional seismic data — and the enormous amount of computer power needed to map it — have allowed producers to target their drilling and fracking efforts better.
Operators are using the process to target the dense shale, limestone and other source rocks that underlie the softer layers they used to aim for.
The improvements have allowed the industry to reverse a 40-year decline in domestic oil production.
“The geology is exactly the same as it was 50 years ago. The world is awash with hydrocarbons,” Mills said. “The only question is whether you're allowed to get to them and whether you have the technology to do it.”