Flaring is a natural byproduct of hydraulic fracturing, but it comes with a price — an economic one and an environmental one. Balancing the two can be tricky

The cheapest solution, flaring all the associated gas generated when you frac a well, may look good on your bottom line, but it doesn’t look good to investors and other stakeholders who are keeping a closer eye than ever on greenhouse gas (GHG) emissions. Reducing methane and CO₂, the two primary emissions created by flaring, top many corporations’ sustainability goals.

But the other option, treating flare gas — which generally has very high energy content — to use on site or send through a pipeline, generally comes with significant expenses. No one’s interested in seeing those costs eat into your profits, either.

So what’s the answer?

At Caterpillar, we’re always on the lookout for solutions that help you strike the right balance between sustainability and profitability. For the frac industry, that means products that help you flare less but don’t cost a fortune to implement. And we landed on a winner in our new 3512E U.S. EPA Tier 4 Final Dynamic Gas Blending™ (DGB) Engine.

Use flare, don’t waste it

Built on the 3512E Tier 4 Final diesel engine, the DGB model delivers the same power, performance and reliability but in a “dual fuel” platform. Because its fuel tolerance range is so wide — extending from 850 to 1250 LHV (lower heating value) — it can run on flare gas with no or minimal treatment, keeping processing costs to a minimum.

Even better, the DGB engine automatically adjusts to changing ambient and fuel quality conditions. That means no input or gas analysis is required for operation and no recalibration is needed when equipment is moved or gas supply changes. And when flare or other gases (CNG, LNG or pipeline gas) aren’t available, the engine automatically switches over to 100% diesel operation, so you’re never out of operation based on fuel supply.

Reduce flare, reduce GHG

The 3512E DGB emits the same or fewer GHG emissions as the diesel model, with air-fuel ratio control and port gas injection minimizing or eliminating methane slip. Using flare gas reduces your overall GHG footprint by decreasing diesel fuel consumption, including the impact of transportation and delivery. It also greatly limits system methane losses from normal gas transportation, processing and handling.

Another, less obvious benefit is the reduced need to apply for flaring permits. They may not be a big cost driver, but the ability to claim “no new permits in 2020” in your sustainability or ESG report holds appeal for many stakeholders.  

Save diesel, save money

The benefits aren’t just environmental, though. The 3512E DGB cuts diesel fuel consumption — and therefore fuel costs — significantly thanks to a maximum diesel displacement rate of 85%. What’s that mean exactly? Basically, if your DGB engine burns 100 gallons of diesel when operating in 100% diesel mode, then it could burn as little as 15 gallons per hour in dual-fuel mode. The other 85 gallons of flare gas cost you little to nothing, depending on how much treatment is required.

The 3512E DGB is also the only engine on the market available with automatic start-stop. Engine Idle Reduction System (EIRS) technology stops the engine automatically when it’s not working and when all the systems it’s monitoring (engine, transmission and pump) are in a healthy temperature range. Then, when needed, EIRS automatically restarts the engine — no operator intervention required, no negative impact on the work cycle and no adverse effects on engine or component health. The result: up to 60% less nonproductive idle time and another 3-5% potential reduction in fuel consumption.

What about e-frac?

Some frac operations are turning to gas turbines, like those produced by Caterpillar subsidiary Solar Turbines, to power their trailers because they can burn flare gas with the highest energy content without any treatment required. If your main objective is to eliminate flaring for environmental reasons, and you’re not interested in distributing the gas for use at other sites, turbines may be a smart choice. They’ll consume more flare gas than a DGB engine, which at a minimum still uses 15% diesel.

But for a more traditional frac operation that’s concerned about capital costs, the DGB engine delivers almost the same environmental benefits for a much lower initial investment — about one third that of an e-frac, or gas turbine-powered, fleet. Again, it’s all about balancing the profitability and sustainability benefits you and your stakeholders care about.