Using clean-burning natural gas to power hydraulic fracturing

Apache has long been a proponent of expanding America’s use of natural gas, perhaps most publicly by supporting compressed natural gas (CNG) vehicles.

The same driving forces that have pushed Apache to lead the way to increase the use of natural gas – which is cheap, clean and abundant – on the nation’s roads have driven the company to kick-start a new trend in the field that has the potential to save the United States millions of barrels of imported oil, significantly cut fuel costs and protect the environment.
 
Apache has partnered with Halliburton and Schlumberger to become the first producing company to have full-time fracture-stimulation spreads use natural gas to power hydraulic fracturing, which is one of the most effective but energy-intensive processes employed by the industry. Hydraulic fracturing is a process in which water, sand and small amounts of chemicals are injected underground at high pressure to release hydrocarbons locked in tight shale formations.
 
In the spring of 2013, Apache utilized two full-time spreads powered by natural gas in Oklahoma’s Granite Wash – one with Halliburton and the other with Schlumberger. Apache also planned to use field gas on its Yeso horizontal fracture-stimulation program in the Permian Basin, with six wells off the same pad using a dual-fuel system recently developed by Baker-Hughes.

Halliburton invented a system for Apache that quickly connects natural gas to pumping engines, making natural 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 natural gas line between trucks.
Besides cutting emissions, shifting to natural gas to power hydraulic fracturing operations makes good economic sense. The equivalent cost of natural gas was running about $1.50 to $2 less per gallon of diesel in summer 2013.

In 2012, the industry used more than 700 million gallons of diesel to pump sand and water during fracture stimulation. By converting the process to field gas, fuel costs would be reduced by about 70 percent and the United States would import 17 million fewer barrels of oil each year.

Schlumberger is testing a system using CNG while Halliburton is using liquefied natural gas (LNG). Both companies have the goal of using field gas to power the massive engines used to pump sand and water into the ground to fracture the formation and release the hydrocarbons.

One of the biggest challenges the companies faced was finding a way to get the powerful engines to run on natural gas as a fuel. The engines currently run on diesel, which uses the heat of compression to ignite the fuel to burn, while natural gas, like gasoline, relies on spark plugs to ignite an air-fuel mixture.
The two companies were tasked with finding a way of using natural gas only when the engines were running at high RPMs and not when idling.

The companies turned to U.S. engine manufacturer Caterpillar Inc. to solve the 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.

Apache also is working with Green Field Energy Services to test engines that would run on 100 percent natural gas.
 
Apache believes the new trend of using natural gas to power hydraulic fracturing will have a huge positive impact on the industry. It will cut down on the amount of imported oil, reduce energy costs and keep the air cleaner.