ANDY PUBLES, Caterpillar Inc.
Fig. 1. Once drilling has been completed at sites like this one in the Permian basin, multi-well pad completions are now routine, delivering tremendous output but also consuming vast energy.
Hydraulic fracturing has revolutionized oil and gas production over the past decade. By unlocking previously uneconomical shale reserves, the United States became a net exporter of natural gas in 2020.i Now, multi-well pad completions are routine, delivering tremendous output but also consuming vast energy—which contributes to higher operating costs, Fig. 1.
Economic pressures, coupled with climate-related goals, are driving continuous evolution in frac pad operations. As industry demands evolve, it’s a priority to make hydraulic fracturing more efficient and cost-effective without sacrificing performance. Each generation of frac technology—from traditional diesel pumps to today’s emerging solutions—brings improvements. Now, a new generation of completions technology is on the horizon, poised to reshape frac operations with a focus on 100% natural gas power that delivers greater efficiency while lowering greenhouse gas (GHG) emissions.
LOOKING BACK: DIESEL FRAC FLEETS AND EARLY ALTERNATIVES
Approximately a decade ago, diesel-powered frac fleets dominated well completions. A typical fleet consisted of 18 to 20 diesel pumping units, 2,500 hp each, plus several diesel-fueled support trucks. These high-powered diesel engines provided exceptional power density and compactness. A relatively small 2,500-hp trailer-mounted engine could deliver over 2,000 hydraulic horsepower (HHP) at the output of the pump, and scaling up was as simple as adding more pumping trucks. This modular, proven approach energized the shale boom, supplying the enormous hydraulic horsepower needed to fracture long horizontal wells.
However, diesel fuel represented a significant operating expense and logistical burden. At the peak of activity, a single large frac fleet could consume as much as seven to 10 million gals of diesel per year,ii emitting roughly 154 million lbs of CO₂ annually.iii Using this fuel meant constant tanker deliveries and onsite storage.
To tackle fuel costs and GHG emissions, the industry began experimenting with alternative power systems, such as dual-fuel engines. The Cat® 3512E Dynamic Gas Blending™ engine uniquely enables up to 70% diesel displacement with field gas, on average, and achieves up to 85% peak displacement in certain conditions.iv These units also provide the flexibility to run on 100% diesel, if the gas supply falters to ensure uninterrupted operations. With dual-fuel engines, oilfield companies can lower fuel costs while utilizing existing diesel engine platforms.
While dual-fuel approaches marked an important advancement, oilfield companies were unable to power operations with 100% gas, as the engines still required a small amount of diesel to operate. Without optimized engineering, the addition of natural gas couldn’t guarantee a reduction in GHG emissions.
Electric frac fleetsv (e-frac) emerged as an alternative option to allow frac operations to burn 100% natural gas. On an e-frac site, electric motors drive the pumping units instead of direct-drive engines, and a central source supplies power. This approach provides several advantages: lower fuel costs through leveraging field gas and reduced GHG emissions at the pump. While e-frac can enable 100% natural gas usage, completely displacing diesel, it requires high upfront costs that include purchasing or renting turbine generator packages or large gas gensets, power distribution systems and entirely new pumping units. The cost required could be prohibitive in certain instances.
E-frac also adds operational complexity, as it significantly changes pad design with the addition of new equipment. Crews must possess electrical expertise and follow robust safety protocols for high-voltage components. As e-frac configurations can vary site to site, crews’ technical knowledge must expand to encompass everything from gas turbines to reciprocating gas generators and even grid connections in some applications.
Following a decade of innovation, a simple, efficient way to run hydraulic fracturing operations on 100% natural gas remains elusive. The industry needs a solution that combines the cost and GHG emissions reduction advantages of natural gas with the operational simplicity of legacy diesel mechanics.
ENABLING 100% NATURAL GAS-POWERED OPERATIONS IN THE OIL FIELD
Today, the push for a completion technology that can run entirely on natural gas has reached a new peak. This shift is driven by E&P companies scrutinizing operational efficiencies and climate-related objectives closer than ever.
Fig. 2. The Caterpillar Gas Mechanical System’s streamlined design eliminates the need for additional equipment onsite.
Field gas costs a fraction of the price of diesel on an energy-equivalent basis. Utilizing natural gas to fuel completion operations turns what was previously viewed as a waste product into a crucial lever to decrease costs. Every gallon of unburned diesel generates savings—and reduces GHG emissions. With evolving industry requirements, many E&Ps have established commitments to decrease carbon-dioxide equivalent (CO₂e) emissions per barrel. The ability to power operations with 100% natural gas satisfies both cost- and climate-related objectives.
For oilfield service providers, this changing landscape represents a challenge and an opportunity. Frac fleets must meet E&Ps’ demands for fully gas-powered completions or risk losing jobs to competitors that offer this capability. However, any additional equipment must easily integrate into existing frac site layouts and workflows to ensure access to personnel that are technically equipped to perform critical maintenance to maximize up-time.
THE EMERGENCE OF FRAC 3.0
This is the context in which “Frac 3.0” is emerging—the next generation of completion technology that enables 100% natural-gas powered operations with a familiar, traditional frac pad layout. The Caterpillar® Gas Mechanical System (GMS) embodies this new approach, meeting the needs of E&Ps and oilfield service companies, alike, Fig. 2. Unlike e-frac fleets that convert gas to electricity, the GMS is a mechanical drive system that preserves the straightforward, proven layout of engine, transmission and pump—and it’s engineered from the ground up to operate on a wide range of gas quality.
Fig. 3. The Cat GMS is engineered for high-pressure frac operations and can withstand extreme conditions in the field.
The GMS integrates the next-generation Cat G3520 engine, a 20-cylinder gas engine capable of producing 3,600 hp, and the Cat TH55G-E90 transmission, a heavy-duty gear and torque converter system with a long pedigree in oilfield applications, Fig. 3. The holistic system is rooted in proven technologies with millions of accumulated field hours. By pairing a high-performance gas engine with a time-tested drivetrain, the GMS delivers maximum power density and durability in a package optimized for 100% natural gas fuel. It’s also engineered for high-pressure frac operations and can withstand the extreme operating conditions encountered in the field.
Importantly, the GMS is specifically built to be operated and maintained by crews with existing technical skill sets. Unlike e-frac, the GMS uses conventional engine mechanics. The control system automates many aspects of engine management, making day-to-day operations similar to current fracing equipment while minimizing potential failure points and simplifying rig-up and rig-down. By keeping the technology approachable, the GMS helps lower total cost of ownership through reduced maintenance costs. When maintenance is required, spare parts are readily available, which helps promote greater uptime.
The GMS’ scalable design delivers more horsepower per trailer, potentially reducing the total number of trailers and related logistics needed on a large frac spread. Fewer trailers equate to fewer engines to service, fewer transmissions and pumps to maintain, and simplified manifold arrangements. As time is money in the oil patch, these efficiencies can produce improved operational efficiency.
The system features purpose-built hardware and integrated control logic that streamline operations and enable the GMS to easily pair with any standard high-pressure frac pump, including SPM™ WS 335 and QEM options. This seamless compatibility enables the GMS to be integrated into an existing fleet without requiring a complete redesign of the surface equipment layout. Oilfield service companies can retain familiar pump hardware and simply change the power source to GMS, easing the adoption curve.
Current field testing in the Permian basin proves that the GMS can operate for as many hours as a job requires. It’s achieved up to 13 barrels per minute (bpm) while sustaining a rate of over 20 hrs of pumping per day. This supports extended operation intervals, and it validates that 100% natural gas-fueled equipment can handle the throughput of modern multi-stage fracturing.
Crucially, the GMS runs on a wide range of gas compositions—from pipeline-grade natural gas to field gas that may contain heavier hydrocarbons—and offers 100% load to 70MN (3,000 HHP) and 25% de-rate at 57MN (2277 HHP) capacity. Such fuel flexibility is essential in remote plays, where raw gas is the most accessible source. This flexibility also eliminates the need to enhance fuel quality onsite, further reducing expenses.
Operating on 100% natural or field gas not only reduces fuel spend but also GHG emissions. Decreasing diesel use sitewide supports climate-related initiatives, as well as operational goals. Importantly, this can be achieved without fundamentally changing how a frac job is run.
WHAT’S NEXT FOR COMPLETION TECHNOLOGY
As pad operations continue to intensify with trends like simul-fracturing multiple wells at once and employing longer-duration pump schedules, it’s critical to utilize ultra-reliable high-horsepower units. The GMS’ ability to sustain more than 20 hours of pumping time per day indicates that greater efficiencies can be unlocked as oilfield companies extend operating cycles.
This also provides valuable flexibility when configuring a frac pad, affording more options to customize a site, based on unique operating parameters, budget, crew and climate-related targets. Such a range of choices is vital given that E&Ps and oilfield service companies continue to navigate the dual challenges of meeting global energy demand while lowering GHG emissions. Innovations that enable 100% natural gas-powered completions balance these priorities and position hydraulic fracturing to evolve and thrive.
ANDY PUBLES is the Drilling and Completion Product Manager for Caterpillar Inc. Andy has worked at Caterpillar for over 16 years and has extensive experience in multiple engineering functions, product strategy and development, with a focus on integrated systems. In his current role, he provides leadership for product strategy and development, as well as application and installation engineering for products used in Drilling and Well Services. Andy holds a B.S. in Electrical Engineering (Power Systems) from Michigan Technological University and an M.S. in Electrical Engineering (Controls and Integrated Systems) from Bradley University.
REFERENCES
Energy and Power Engineering. Analysis of Emissions Profiles of Hydraulic Fracturing Engine Technologies. 2023. https://www.bjenergy.com/Portals/0/Documents/epe_2023010915323656.pdf?ver=cwCFIKNG38h3AedmBjipGQ%3D%3D#:~:text=Hydraulic%20fracturing%20has%20been%20practiced,diesel%20reciprocating%20engines%20to%20drive.
National Fuel. The Results: Putting Emissions Data to Work in Operations. https://www.nationalfuel.com/wp-content/uploads/documents/DUG-East-2021_Presentation.pdf
Energy and Power Engineering. Analysis of Emissions Profiles of Hydraulic Fracturing Engine Technologies. 2023. https://www.bjenergy.com/Portals/0/Documents/epe_2023010915323656.pdf?ver=cwCFIKNG38h3AedmBjipGQ%3D%3D#:~:text=equipment%20%28see%20Figure%201%29,were%20over%20500%20frac%20fleets.
com. Introducing a Game-Changer for the Well Service Industry. https://www.cat.com/en_US/by-industry/oil-and-gas/dynamic-gas-blending-engines/3512E-dgb-engine.html.
American Oil & Gas Reporter. Electric Frac Spreads Gradually Pick Up Speed in Highly Disciplined Market. August 2023. https://www.aogr.com/magazine/markets-analytics/electric-frac-spreads-gradually-pick-up-speed-in-highly-disciplined-market#:~:text=Electrically,emphasis%20on%20sustainability%20and%20efficiency.
Related Articles
FROM THE ARCHIVE
