Apache Corp., Houston, said it has partnered with Halliburton and Schlumberger to find ways to use natural gas to power hydraulic fracturing, one of the most energy-intensive processes employed by the industry.
Only 1% of drilling rigs and zero full frac spreads are powered by gas, Apache said. In 2012, the industry will have used more than 700 million gal of diesel to pump sand and water during fracture stimulation. That’s $2.38 billion spent on diesel at a recent average of $3.40/gal.
Converting the process to using field gas would reduce fuel costs by 70%, said Mike Bahorich, Apache’s executive vice-president of technology.
“When I approached Halliburton and told them Apache wanted to do this, they told me that the reason that frac spreads that moved every week did not run on natural gas was due to the complexity of the natural gas supply and support infrastructure,” Bahorich said. “I also contacted Schlumberger. It didn’t take long for both companies to call back and tell me it could be done.”
Halliburton told Bahorich it invented a system for Apache that quickly connects gas to pumping engines, making gas a viable fuel to rapidly and routinely move from job to job. It is comprised of a simple gas line that connects from the natural gas source to an engine using a quick-connect jumper to link the gas line between trucks.
Bahorich decided to put out a bid to both Halliburton and Schlumberger. Each came back and said separately they would do a trial with Apache at zero cost.
“That’s almost unheard of, and it shows you how much they wanted to do this,” Bahorich said. “By using field gas, the US would import 17 million fewer barrels of oil each year to make the diesel to fuel these fracs,” Bahorich said.
Schlumberger is testing a system using compressed natural gas, while Halliburton is using liquefied natural gas. Both companies have the goal of using field gas to power the massive engines used to pump sand and water into the ground in hydraulic fracturing, which is credited with having led to massive increases in US oil and gas production.
One of the biggest challenges the companies faced was finding a way to get the powerful engines to run on gas as a fuel. The engines currently run on diesel, which uses the heat of compression to ignite the fuel to burn, while gas, like gasoline, relies on spark plugs to ignite an air-fuel mixture.
The team was faced with the challenge of using gas only when the engines were running at high RPMs and not when idling. The companies turned to US engine manufacturer Caterpillar Inc. to solve that problem.
“Caterpillar was able to develop dual-fuel kits that would allow the engines to run on diesel while idling and natural gas when they are throttled up for pumping,” said Brian Erickson, Apache senior production engineer, E&P Technology. Erickson, along with Sam Goswick, a drilling engineer with the Central Region, is leading the field trials. “This has been a key factor that is allowing us to move forward to make this a reality.”
Apache, Halliburton, and Schlumberger have had several successful tests in Oklahoma in the Granite Wash using as many as eight engines running on the dual-fuel kits. A full complement of 12 engines was scheduled to be used on Dec. 10, 2012, at a frac near Elk City, Okla.
Potential cost savings by using dual-fuel in a hydraulic fracturing operation are great, Apache said.
For example, a single frac in the Granite Wash at Stiles Ranch field in the Texas Panhandle would typically use 36,290 gal of diesel. Using a mid-December 2012 price of $3.40/gal for diesel, the total fuel bill would be $123,386. At current gas prices, including transportation, the total fuel cost using dual-fuel engines with gas drops to $74,473.
Bahorich said, “This is a real trend and it’s happening now. We’re witnessing a sea change in the industry that will have a great impact not only on how much less oil is imported but also will help keep our air clean.”