US Shale Sector Embraces Rise of the ‘G-Fleet’

_ The oil and gas industry is undergoing a revolution—an electric revolution. Driven by efficiency gains, cost savings, and reduced emissions, one area in which the transformation is clearly evident is the US onshore fracturing sector. Interestingly enough, the fuel supporting this transition has been right under the industry’s nose all along: natural gas. “Right now, about 70% of the pressure pumping fleet out there can use natural gas in one form or another, whether that’s Tier II [diesel-gas blend (DGB)], Tier IV DGBs, electric, or direct-drive turbines,” said Mark Chapman, senior vice president of oilfield service intelligence at Enverus. Chapman added, “A new trend we’re starting to hear more about is using 100% Tier IV reciprocating engines—but burning 100% natural gas. This allows them to get the same benefits as electric, except without the need for whole power generation systems.” Electric fleets, or e-fleets, have become popular in recent years among US shale producers, but the term is somewhat misleading, as they are actually gas fleets, explained Roy Aune, vice president of advanced equipment technologies for pressure pumping provider Liberty Energy. “People talk about ‘e-fleets,’ but we should call them ‘g-fleets.’ Virtually all electric frac pumps are driven by a gas engine on-site. It’s either gas converted to electricity, which is then converted to mechanical and hydraulic energy, or something similar. I’m not aware of a single instance where an entire frac fleet is running off the public grid,” he said. Clear Advantages The shift away from diesel and toward natural gas is gaining momentum thanks to several advantages: natural gas is three to five times cheaper than diesel on a per unit of energy basis; modern natural gas engines consume less fuel compared with Tier II and Tier IV diesel engines; and overall emissions are significantly lower. Three of the most common pressure pumps today are dual-fuel, natural gas direct-drive, and electric. Dual-fuel technology allows equipment to use a blend of natural gas and diesel or 100% diesel if there is a shortage of gas for power generation or heating. Direct drive means the engine is directly connected to the pump through a transmission. This contrasts with electric fracturing where a gas turbine or reciprocating engine drive a generator, which then powers electric motors that are coupled to the pumps. A paper published by Liberty at the recent SPE Hydraulic Fracturing Technology Conference and Exhibition, SPE 223527, provides a detailed comparison of the available options and found that electric gas reciprocating engines and direct-drive gas reciprocating engines produce significantly fewer emissions than Tier II diesel and Tier IV dual-fuel engines. Tier II diesel engines posted the highest CO2e emissions at 865.6 g/kWh, while Tier IV dual-fuel engines followed closely at 836.4 g/kWh. In comparison, gas reciprocating engines used for electric fleets cut emissions by 22% relative to Tier II diesel, producing 678.6 g/kWh.