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Natural gas drilling is typically a diesel-intensive process, but Cabot Oil & Gas just announced the latest in a series of innovations designed to utilize more equity natural gas production in Cabot’s own operations. The company is now using a field gas/diesel mixture to hydraulically fracture Marcellus Shale wells in Pennsylvania.

The process is touted as a “triple threat” that decreases air emissions, reduces truck traffic – also cutting down on diesel emissions – and cuts costs. Cabot teamed up with Caterpillar for the engine technology and well completion service provider FTS International on the well performance side.

Cabot’s Susquehanna County, Pennsylvania, acreage is situated within the sweetest dry gas portion of the Marcellus, External Communications Director George Stark told Breaking Energy, which makes it easy to get the gas from a nearby well or a gathering line to a completion job without extensive processing. Sweet gas is low in sulfur.

In this instance, Cabot sourced gas from a gathering line “that’s essentially on location,” sent it through a series of regulators, stepped down the pressure, ran it through a dehydration unit and then brought it to an engine. The process replaces 70% of the diesel fuel that would otherwise be used to power the well completion equipment. “These steps are all done at the well pad,” said Stark.

Typically, 100 – 150 gallons of diesel fuel are used per frack stage, but fuel use varies depending on location/equipment and each well usually has a different number of frack stages, he said.

Cabot had been looking for opportunities to utilize more equity gas in its Marcellus operations, said Stark, and first constructed a compressed natural gas station – completed late last year – and they now have 60 vehicles running on CNG. Next they retrofitted a drilling rig to run on CNG, and now the company has demonstrated their ability to run completion equipment on field gas.

“CNG must be stored to be delivered, the difference with field gas is you are not storing it, you are drawing it straight from a well or a gathering line,” Stark said.