The first of 16 methane emissions studies focusing on unconventional natural gas production and organized by the Environmental Defense Fund (EDF) has been published and says that industry efforts to control emissions at well sites are having a significant impact.
Emissions from hydraulically fractured well completions are “significantly lower than estimates used by the EPA [Environmental Protection Agency] in the national emissions inventory,” according to Southwestern Energy Co., one of the industry partners in the research. “This study shows that the amount of methane emissions from the natural gas production sector can be effectively minimized by applying reasonable emission capture and control practices,” said Mark Boling, Southwestern general counsel.
The majority of hydraulically fractured well completions that were sampled during the study had equipment in place that reduces potential methane emissions by 99%. While pneumatic controllers account for 25% of the overall methane emissions from natural gas production, measured methane emissions from certain types of these controllers are higher than current EPA estimates. Additional study is required to more accurately quantify emissions associated with well liquids unloading and pneumatic controllers, Southwestern said.
The research involved more than 90 partners, including universities, scientists, research facilities, and oil and gas companies. The paper, “Measurements of methane emissions at natural gas production sites in the United States,” was published Monday in the Proceedings of the National Academy of Sciences (PNAS).
Led by David Allen at The University of Texas at Austin (UT), the study took direct measurements of methane emissions associated with unconventional natural gas production, specifically shale gas wells that use hydraulic fracturing.
The UT study, which only deals with the extraction phase of the natural gas supply chain, is the opening chapter in a broader effort to advance understanding of the climate implications of methane emissions resulting from the U.S. natural gas boom.
The nation’s largest single source of methane emissions is the vast network of infrastructure, including wells, pipelines and storage facilities, that supplies U.S. natural gas, UT said. “Experts agree that methane leaked or vented from natural gas operations is a real concern, yet estimated emission rates vary greatly, from 1-8% of total production,” EDF said.
“We know that immediate methane reductions are critical to slow climate change,” said EDF president Fred Krupp. “But we don’t yet have a handle on how much is being emitted. We need better data, and that’s what this series of studies will deliver. As we understand the scope of what’s happening across the natural gas system, we will be able to address it.”
Launched last year, the research is designed to collect methane emissions data associated with gas production, gathering lines and processing facilities, long-distance pipelines and storage, local distribution, and commercial trucks and refueling stations.
“The scientific talent leading these studies, the partnership with industry and access to their facilities, and the diverse research methods used, gives us the confidence that when the project concludes in late 2014, we’ll be able to greatly increase our understanding of the climate impacts of switching to natural gas from other fossil fuels, through this unprecedented collective research effort,” said EDF Chief Scientist Steve Hamburg.
UT’s peer-reviewed study reports data from emission sources from gas production. Study results show that total emissions are in line with EPA estimates from the production of natural gas, yet the distribution of those emissions among activities differ. Methane emissions are lower than estimated by EPA for well completions and higher for valves and equipment used to control routine operations at the well site.
According to Hamburg, UT’s low well emissions finding indicates an early phase-in of EPA’s New Source Performance Standards (NSPS), which requires all new fractured natural gas wells to either burn-off or use “green completions” (an emissions control method that routes excess gas to sales), is working. Results also suggest that these new regulations, which will be fully implemented in 2015, are having the desired effects. No national survey of how many operators currently use green completions is available, but the data suggest that once this practice is required, emissions from this phase of the production process will decline.
Hamburg said the higher-than-estimated emissions from valve controllers (also known as pneumatics) and equipment leaks show important opportunities for reducing emissions in the future. Considerable opportunities exist under the Clean Air Act to strengthen NSPS, including requiring emissions controls for equipment routinely found at oil and natural gas production sites, such as valves or connectors at the well pad or pressure relief valves on storage tanks, and controls for nearly half a million existing pneumatics at natural gas wells and for the thousands of existing compressors that move gas from the well through the system to the end user.
The NSPS do not contain requirements to reduce well completion emissions from hybrid wells that produce both oil and natural gas, which are more common as the price of oil remains high.
“The way in which wells are drilled and brought into production has been evolving,” said Allen, professor of chemical engineering at UT’s Cockrell School of Engineering. “The overall goal was to measure methane emissions during production at a large number of recently developed sites, and to assess the national implications for methane emissions. The team performed the first-ever direct measurements of methane emissions from some of these sources.”
The UT-led field study was a cooperative effort involving experts from EDF; Anadarko Petroleum Corp.; BG Group plc; Chevron Corp.; Encana Oil & Gas (USA) Inc.; Pioneer Natural Resources Co.; SWEPI LP (Shell); Southwestern; Talisman Energy USA; and ExxonMobil Corp.’s XTO Energy.
“This study tackles one of the most hotly debated issues in environmental science and policy today,” said Mark Brownstein, associate vice president and chief counsel of EDF’s US Climate and Energy Program. “It shows that when producers use practices to capture or control emissions, such as green completions, methane can be dramatically reduced. The study also demonstrated, however, that certain methane emissions are larger than previously thought, indicating that there are many further opportunities to reduce emissions.”
During the yearlong study, the UT-led team selected times and general locations for sampling activities, and companies provided access to completions that occurred during those periods. Sampling was designed to be representative of company operations in the Gulf Coast, Midcontinent, Rocky Mountain and Appalachian regions. Measurements of active equipment at 150 production sites with 489 wells, 27 well completion flowbacks, nine well unloadings and four well workovers were included in the study. The types of sources measured account for two-thirds of methane emissions that occur during natural gas production, as estimated in the most recent national greenhouse gas inventory.
Measured emissions from completion flowbacks were much lower than previously estimated. Two-thirds of the well completion flowbacks measured in the study either captured or combusted emissions, resulting in emissions measurements that were 99% lower than would have occurred in the absence of capture and combustion. The remaining one-third of completion flowbacks vented methane, but these were low-emitting wells, so in total, the emissions from completion flowbacks were 97% lower than current EPA estimates, researchers found.
“The net emissions for completion flowbacks is significantly lower than previous estimates, indicating the type of emission control activities observed during these events are very effective,” Allen said.
Full details on the UT study findings, access to the dataset and an overview of the second phase of data collection, already under way, are provided on UT’s methane website.
“While we are still reviewing the study, we welcome the finding that overall methane emissions from the production of natural gas are lower than the most recent EPA estimates,” said America’s Natural Gas Alliance’s Erica Bowman, vice president of research and policy analysis.
“The study provides further support for the findings of other credible researchers: that greater use of natural gas can substantially reduce greenhouse gas emissions. We are continually putting into operation equipment and practices that demonstrate our commitment to lower emissions in the production process.”
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