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Pennsylvania Oil and Gas Methane Emissions: Uncovering the Whole Picture

In mid-February, the Environmental Defense Fund (EDF) released a study estimating that methane emissions from active Pennsylvania oil and gas wells were five times higher than previously estimated. This estimate came from analyzing the results of 16 peer-reviewed studies. About half of the estimated methane emissions came from conventional gas wells, which leak about 23% of their volume. While unconventional (fracked) gas wells leak a smaller percentage of their gas (about 3%), their higher overall gas volume makes the amount of gas released by each type of well roughly equal. EDF’s data included integral infrastructure such as compressors, produced water tanks, and flares. While the Pennsylvania DEP has released emissions regulations for new unconventional wells and related infrastructure, promised regulations for existing oil and gas infrastructure have not been released.

A well pad under construction in northeast Pennsylvania. Photo by Coryn Wolk

EDF and other organizations advocate for tighter emissions regulations that would force adoption of better leak-prevention methods and technologies. EDF’s analysis shows that leak prevention technology would greatly reduce emissions from natural gas wells and their associated infrastructure. However, existing maintenance and regulatory problems in Pennsylvania prompt some questions about this solution.

As EDF’s data shows, conventional gas wells are a massive contributor to methane emissions in Pennsylvania. This is in part because many have been abandoned and left uncapped. With little documentation of responsibility, limited regulatory capacity, and abysmal record-keeping, this problem has been slow to improve. As unconventional gas wells date from a much more recent time span (2009 at the oldest), current records and ownership are more accessible. However, beyond the roughly 5% of unconventional gas well casings that fail immediately, the majority are predicted to fail over a 100-year timespan. For reasons including the volatility of natural gas prices and failed small-scale speculator companies, many unconventional wells have already undergone changes of ownership that led to issues with responsibility and liability. Will the technological fixes that EDF advocates endure over decades and potential future site abandonment?

Given the years-long struggle to codify even government-sanctioned state and federal methane regulations, these questions may seem premature. However, the Pennsylvania government’s refusal to consider or plan for the long-term issues likely to arise from fossil fuel infrastructure has led to our current collection of crumbling and/or polluting infrastructure largely left in the lap of state and local governments and residents.

PSR Philadelphia also attended a presentation by Peter DeCarlo, PhD, an associate professor who studies atmospheric chemistry in Drexel’s College of Arts and Sciences and College of Engineering, about his 2012 and 2015 research to measure emissions from Marcellus Shale fracked gas infrastructure. Drexel’s measurements included all stages of unconventional wells, from drilling to completion, as well as production and distribution infrastructure such as compressor stations and pipelines. Measurements were taken in northeastern Pennsylvania, where mainly dry gas (methane) is produced, and in several southwestern Pennsylvania counties, where a mixture of dry gas and wet gas (natural gas liquids such as ethane and propane) is produced. Because wet gas is usually extracted as a mixture of several different natural gas liquids, it requires more infrastructure to separate into is component gases, creating more emissions. In addition to methane, the Drexel-led team measured pollutants including particulate matter (PM), nitrogen oxides (NOx), carbon monoxide, and carbon dioxide. In their 2012 measurements, “Compressor stations and transient sites (e.g., drill site and completion) were observed to be the largest emitters of most of the measured species (i.e., CH4, CO, NOx, CO2), followed by producing well sites.” In general, comparisons with the state’s emission inventory show that the measured emission rates for methane were much higher (1.5-10 times) than the state estimates. The team also found that the emissions rates from compressor stations had little relationship to the compressor station’s size or horsepower, raising questions for future research.

Halliburton cement trucks (for fracked well casings) in northeastern Pennsylvania. Photo by Coryn Wolk

Upon returning to the same regions in 2015, part of the team’s goals was to test the state’s claim that methane emissions had dropped between 2012 and 2015. Because of abandoned coal mines in the region, there were higher background levels of methane in southwest Pennsylvania than northeast. However, DeCarlo noted that no one had been willing to fund Pennsylvania baseline methane measurements before fracking began in 2009. Over the past three years, the number of new wells drilled each year had dropped while the annual amount of natural gas produced from the Marcellus Shale rose. Contrary to the state’s estimates, the team’s measurements showed a clear increase in methane emissions. The data indicated that methane emissions in 2015 were approximately 3 times higher than emissions in 2012. This indicates that most methane emissions don’t come from new wells being drilled, but the later stages of the fracking process, such as production, pushing the natural gas through pipelines, and processing it. The team also did some preliminary measurements of methane emissions from Pennsylvania’s tens of thousands of miles of natural gas pipelines, which aren’t included in Pennsylvania’s emissions inventory or the latest EDF Pennsylvania-focused research. Their findings indicated significant fugitive emissions from natural gas pipelines.

Propane storage tanks at a terminal in Philadelphia. Photo by Erik McGregor

Pennsylvania cannot go back in time and tighten construction standards for conventional gas wells or measure baseline methane levels. However, EDF and DeCarlo’s research show that there are still plenty of important opportunities for research and action. If emissions inventories are based on the optimistic guesses of natural gas industry operators, Pennsylvania needs to find a more accurate foundation for its air pollution policies. Given the magnitude of the problem, the methane regulations EDF and partner organizations are advocating should be an easy first step, not the final goal. Even as more wells are drilled, the Pennsylvania fracking industry has been moving into a second stage involving a massive pipeline build-out and petrochemical processing and export infrastructure. If pipelines and later-stage infrastructure are as major a source of methane emissions as DeCarlo’s team finds they may be, this will cause Pennsylvania methane emissions to rise even faster. Pennsylvania has the chance to avoid repeating, yet again, its past negligence by researching and acting to prevent emissions from proposed infrastructure. Will it?


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