How Would EPA Regulate Industry's Methane Emissions?

U.S. EPA yesterday released five white papers on methane emissions from the oil and gas industry that could serve as a basis for regulations in the future.

The white papers are the first step in a methane reduction strategy announced by the White House last month (EnergyWire, March 31). They will be followed by a report this fall on whether EPA has the legal underpinnings to regulate the industry under the Clean Air Act. If it decides it does, regulations would be in place by the end of 2016.

The oil and gas sector is the largest industrial emitter of methane in the United States, and recent studies have suggested that the production phase, when the fossil fuels are first extracted, could be especially leaky. Methane, the key constituent of natural gas, escapes from pumps, valves and compressors, and other instruments used in the process.

The EPA white papers focus on five distinct parts of the oil and gas sector overall and review the state of emissions knowledge available from these. They also identify methods and technologies to control the emissions.

Environmental groups welcomed the white papers, saying that regulations are likely to follow them.

"EPA's white papers, along with a growing mountain of scientific research on the magnitude of the problem, build the foundation for direct regulation of methane emissions from the oil and gas industry," said Conrad Schneider, advocacy director at the Clean Air Task Force. "When EPA has synthesized the information in these white papers, we are confident that the agency will conclude that direct regulation of methane from oil and gas is necessary to reduce harmful emissions from this sector."

Green groups such as Earthworks that have, on principle, rejected natural gas development welcomed the white papers but rejected the emphasis on "dirty" fossil fuel extraction.

"While we encourage the EPA to do everything within its power to stop methane emissions from oil and gas production, that is no substitute for dropping dirty fossil fuels [and] replacing them with truly clean alternatives like conservation and renewable energy," said Lauren Pagel, policy director for EarthWorks.

Pneumatic devices

One white paper focuses on pneumatic pumps and controllers, which are operated using natural gas as the fuel. Pneumatic controllers regulate temperature, pressure or other processes by the opening and closing of valves. Pneumatic pumps can be used to push gas along a pipeline or inject solutions such as corrosion inhibitors down wells.

Controllers account for 13 percent of the emissions from the oil and gas sector, while pumps account for 16 percent of the overall emissions from the natural gas and processing sector, EPA notes.

Some types of the devices are worse offenders than others. High-bleed pneumatics emit continually, EPA notes. Intermittent and low-bleed devices emit less, while pneumatics that do not rely on natural gas are non-emitting.

But swapping a high-bleed device for a lower-emitting device is not always feasible, EPA noted. When a swap is possible, a high-bleed device can be replaced with a low-bleed one for $165, the agency notes.

Liquids unloading

Older wells can accumulate liquids in the well bore that interfere with the production of the fossil fuel. In these cases, an operator would remove the fluids in a process called liquids unloading, releasing trapped methane and volatile organic compounds to the atmosphere. The unchecked release is called a "blowdown" and is the most common method, EPA notes.

Data on the process are sparse, but the existing EPA inventory suggests that liquids unloading emits 14 percent of the total methane emissions from the natural gas production sector.

EPA reviewed five reports on the process. One of them -- the agency's Greenhouse Gas Reporting Program -- found that 276,378 metric tons of methane was vented in 2012.

Smart plunger lifts that automatically bring liquids out of the well can help cut down releases by more than 90 percent, EPA writes.

Completions from oil wells

Some oil wells co-produce natural gas, but these emissions are unregulated by EPA.

EPA noted that limited information is available on how much methane is vented from oil wells. One study looked at oil-rich North Dakota and found that releases during completions from oil wells were highly variable in their composition. Some regions released volatile organic compounds in spurts rather than at a steady rate.

The agency noted that various studies have found oil wells emit between 44,306 and 247,000 tons per year.

Completions are regulated for gas wells using reduced emissions completions (REC), and these could be used for oil wells, as well. How well the process works would depend on the length of the completion, the composition of gas and the specific fracking techniques employed, EPA notes.

Some operators currently do perform RECs on oil wells, but most tend to flare or vent all excess gas.

Compressors

Reciprocating compressors are used during production on oil and gas fields, while centrifugal compressors are used during transmission, EPA notes.

Together, the devices emitted 2,071,633 metric tons in 2014 from the natural gas production, processing, transmission and storage phases.

Emissions from reciprocating compressors can be cut down by swapping a part in these machines called rod packers, EPA notes. And emissions from centrifugal compressors can be reduced by using wet seals rather than dry seals.

Leak detection

Devices in a state of disrepair on a well pad can unexpectedly leak their gaseous contents. Such leaks can disproportionately contribute to the emissions in a basin at a given time.

"One study found that the majority of leak emissions from these sites may be attributed to maintenance-related issues such as open thief hatches, failed pressure relief valves, or stuck dump valves," EPA notes.

Optical imaging cameras are often used to identify leaks, but operators of the devices need a certain level of skill to use them appropriately. The cameras do not quantify the leak.

Once a leak has been identified, it can be fixed rather cheaply, the agency notes.

Gayathri Vaidyanathan, E&E reporter

Republished from EnergyWire with permission. EnergyWire covers the politics and business of unconventional energy. Click here for a free trial

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