While the practice of hydraulic fracturing has been a prime target for environmentalists over the past few years, proponents of fracking are convinced the advantages outweigh the risks. Fracking will provide nations like the United States, Canada, and Australia with easy, cheap, domestic natural gas. Natural gas will revolutionize the world energy economy. Natural gas will decrease foreign oil dependence, energy prices, and carbon emissions. When it comes to fracking for natural gas, industry can certainly preach the benefits. However, it is only recently that industry players are putting these principles into practice by experimenting with natural gas engines.
Although hydraulic fracturing has the potential to produce enormous amounts of energy, it is also an extremely energy intensive process. Hydraulic fracturing involves the pumping of large amounts of fluid underground at extreme speeds and pressures. In the early 2000s, the average frac pump could produce between 1,300 and 2,000 billion horsepower (bph)—and energy requirements have only increased from there6. As horizontal drilling in tight shales has become more prevalent, frac pumps rated at over 2,000 bph are becoming more and more common6. So where is all this energy coming from? Prior to 2013, the answer was diesel.
For an industry known for touting the cost and environmental benefits of natural gas over crude oil products, this seems like an odd discrepancy. Indeed, the lag between natural gas production and natural gas use in the fracking industry has more to do with established infrastructure than with any conscious resistance to change. Historically, diesel has always been the fuel of choice for high power operations like industrial transportation and pumping. This has to do with fundamental design differences between diesel engines and gasoline or natural gas engines. While both gasoline and natural gas engines use spark plugs to ignite a mixture of air and fuel, diesel engines ignite fuel directly through compression. For this among other reasons, diesel engines are simply more efficient, producing greater power per volume of fuel6. At the same time, diesel is significantly more expensive than natural gas and also produces higher levels of harmful emissions. As natural gas prices drop and emissions regulations are tightened, these disadvantages have turned industry attention towards natural gas engines in the past year.
From natural gas engines to dual fuels
‘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,’ said Mike Bahorich, Apache’s executive vice president of Technology.1
However, Halliburton quickly remedied the problem by developing a system to quickly connect natural gas supply to mobile pumping engines. The system involved the use of a single connecting line with a quick-connect jumper to link between natural gas supply and engines1.
Following this solution, both Halliburton and Schlumberger offered their services to do a trial with Apache at zero cost1.
‘That’s almost unheard of, and it shows you how much they wanted to do this,’ Bahorich said.1
Halliburton is now working on developing a pump system using liquefied natural gas (LNG) while Schlumberger is investigating compressed natural gas (CNG). Both companies hope to develop an efficient system for using natural gas produced in the same field.
Another challenge faced by the Apache project was meeting the high power requirements for frac pumps using natural gas engines. Engine manufacturer Caterpillar Inc. stepped into the existing partnership to provide a solution to this problem. The resulting product is a dual fuel engine that runs on diesel when idling and switches to natural gas for high powered pumping1.
‘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, ‘This has been a key factor that is allowing us to move forward to make this a reality.’1
These dual fuel kits allowed Apache to run several successful tests before completing two wells in Oklahoma using a 12 engine unit. The Oklahoma wells made up the first full frack spread operating off natural gas in the field1.
Advantages of ditching the diesel
Although diesel engines have traditionally been considered more efficient for handling large workloads, in the current energy climate, natural gas engines may prove to have a significant cost advantage. According to 2012 Energy Information Administration reports, diesel4 was priced at around $3.97 while wellhead natural gas3 cost only around $.02 for the same amount. In fact, Apache has said it expects a 60% reduction in fuel costs with the implementation of dual-fuel systems.
And part of this reduction in cost comes from the reduction in fuel transportation. Diesel fuel is a crude oil product and is thereby often imported overseas from oil rich regions like the Middle East. Energy security implications aside, import distance contributes greatly to price. On the other hand, the hope for natural gas is that it could power engines in the same field it is being extracted from, incurring virtually no transportation fees.
Finally, less fuel transportation cuts down on total truck trips in and out of a drilling site, reducing harmful emissions associated with the drilling process. Transportation trucks also run on diesel fuel engines which produce smog containing nitrogen oxides and soot not found in natural gas emissions. In fact, the US EPA has identified pollution from diesel engines as “one of the country’s most important air quality challenges”2. Natural gas also produces lower carbon emissions than diesel fuel. While the difference is not as pronounced as that between natural gas and coal, the sheer volume of diesel fuel currently used in fracking may make it significant. Apache estimates that the US fracking industry alone uses about 700 million gallons of diesel annually to fuel frac pumps2.
Natural gas engines: the future of fracking?
As an industry, oil and gas production tends to be heavily defined by established infrastructure and proven technologies. So do natural gas engines have a future in fracking? The heavy cost benefits and successful tests say yes.
‘You’re going to see this spreading quite rapidly across the industry,’ said Douglas E. Kuntz, president and CEO of Pennsylvania General Energy Co (PGE). ‘As the technology evolves, you’ll see more companies across the country doing more natural gas fueling of this equipment.’2
And indeed, PGE is bringing natural gas power to fracking in Pennsylvania, converting a 16 engine frack spread in Meadville just this spring. The system uses a dual-fuel blend and is expected to cost 75% less than it’s diesel counterpart2.
Cabot Oil and Gas is also picking up on the trend. Cabot is a leading shale gas producer in the Marcellus Shale and recently announced plans to use natural gas from the formation to power its frac pumps5. The company plans to use a dual-fuel blending kit made by Caterpillar that substitutes diesel with natural gas during high pressure pumping. The system is compatible with field gas, CNG, and LNG5.
‘This is a real trend and it’s happening now,’ said Bahorich of Apache Corp. ‘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.’1
1) Apache Corp. (2013, January 1). Apache leads way to new natural gas trend.
2) Associated Press. (2013, January 21). Fracking industry switching from diesel to natural gas. Pittsburgh Post-Gazette
3) Energy Information Administration, Independent Statistics and Analysis. (2012). Natural gas prices
4) Energy Information Administration, Independent Statistics and Analysis. (2012). Weekly retail gasoline and diesel prices
5) Sreekumar, A. (2013, May 25). How this company is using natural gas in fracking. The Motley Fool,
6) Treida, M. & Poole, C. (n.d.). The evolution of hydraulic fracturing and its effect on frac pump technology. Weir SPM,