Toward a better understanding and quantification of methane emissions from shale gas development by Dana R. Caultona, Paul B. Shepsona, Renee L. Santoroc, Jed P. Sparksd, Robert W. Howarthd, Anthony R. Ingraffea, Maria O. L. Cambalizaa, Colm Sweeney, Anna Karion, Kenneth J. Davish, Brian H. Stirmi, Stephen A. Montzkaf, and Ben R. Millerf, Edited by Barbara J. Finlayson-Pitts, University of California, Irvine, Irvine, CA, and approved March 12, 2014 (received for review September 4, 2013), Proceedings of the National Academy of Sciences of the United States of America
Significance
We identified a significant regional flux of methane over a large area of shale gas wells in southwestern Pennsylvania in the Marcellus formation and further identified several pads with high methane emissions. These shale gas pads were identified as in the drilling process, a preproduction stage not previously associated with high methane emissions. This work emphasizes the need for top-down identification and component level and event driven measurements of methane leaks to properly inventory the combined methane emissions of natural gas extraction and combustion to better define the impacts of our nation’s increasing reliance on natural gas to meet our energy needs.
Abstract
The identification and quantification of methane emissions from natural gas production has become increasingly important owing to the increase in the natural gas component of the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern PA in June 2012. A large regional flux, 2.0–14 g CH4 s−1 km−2, was quantified for a ∼2,800-km2 area, which did not differ statistically from a bottom-up inventory, 2.3–4.6 g CH4 s−1 km−2. Large emissions averaging 34 g CH4/s per well were observed from seven well pads determined to be in the drilling phase, 2 to 3 orders of magnitude greater than US Environmental Protection Agency estimates for this operational phase. The emissions from these well pads, representing ∼1% of the total number of wells, account for 4–30% of the observed regional flux. More work is needed to determine all of the sources of methane emissions from natural gas production, to ascertain why these emissions occur and to evaluate their climate and atmospheric chemistry impacts.
Up To 1,000 Times More Methane Released At Gas Wells Than EPA Estimates, Study Finds by Ari Phillips, April 15, 2014, Think Progress
The study, published Monday in the Proceedings of the National Academy of Sciences, found that drilling operations at seven well pads emitted 34 grams of methane per second, on average, much higher than the EPA-estimated 0.04 grams to 0.30 grams of methane per second. The researchers, who were attempting to understand whether airborne measurements of methane aligned with estimates taken at ground level — the method commonly used by the EPA and state regulators — flew a plane over the region of the Marcellus Shale for two days in June 2012.
“The researchers determined that the wells leaking the most methane were in the drilling phase, a period that has not been known for high emissions,” reported the Los Angeles Times. “Experts had thought that methane was more likely to be released during subsequent phases of production, including hydraulic fracturing, well completion or transport through pipelines.” …
Paul Shepson, an atmospheric chemist at Purdue University who worked on the study, toldthe Los Angeles Times that while more research is needed to determine whether the extremely high measurements are typical, the vast disparity between the readings illustrates the limitations of the current methods. “The EPA’s approach puts regulators at the mercy of energy companies, which control access to the wells, pipelines, processing plants and compressor stations where methane measurements should be made, ” he continued.
… A recent comprehensive Stanford study reviewed over 200 earlier studies to find that “U.S. emissions of methane are considerably higher than official estimates,” and that “leaks from the nation’s natural gas system are an important part of the problem.” …
Leaking natural gas infrastructure can result in deadly explosions. In 2012, 244 “significant” pipeline incidents, happened in the U.S., leading to 10 fatalities and 55 injuries according to the Pipeline and Hazardous Materials Safety Administration.
Unexpected loose gas from fracking by Patterson Clark, April 14, 2014, Washington Post
A survey of hydraulic fracturing sites in Pennsylvania revealed drilling operations releasing plumes of methane 100 to 1,000 times the rate the EPA expects from that stage of drilling, according to a study published Monday in the Proceedings of the National Academy of Sciences. … Methane plumes might be the result of drilling through coal beds, which are known to release large amounts of methane when mined. [Emphasis added]
EPA drastically underestimates methane released at drilling sites by Neela Banerjee, April 14, 2014, LA Times
Drilling operations at several natural gas wells in southwestern Pennsylvania released methane into the atmosphere at rates that were 100 to 1,000 times greater than federal regulators had estimated, new research shows. Using a plane that was specially equipped to measure greenhouse gas emissions in the air, scientists found that drilling activities at seven well pads in the booming Marcellus shale formation emitted 34 grams of methane per second, on average. The Environmental Protection Agency has estimated that such drilling releases between 0.04 grams and 0.30 grams of methane per second.
The study, published Monday in the Proceedings of the National Academy of Sciences, adds to a growing body of research that suggests the EPA is gravely underestimating methane emissions from oil and gas operations. The agency is expected to issue its own analysis of methane emissions from the oil and gas sector as early as Tuesday, which will give outside experts a chance to assess how well regulators understand the problem.
Carbon dioxide released by the combustion of fossil fuels is the biggest contributor to climate change, but methane — the chief component of natural gas — is about 20 to 30 times more potent when it comes to trapping heat in the atmosphere. Methane emissions make up 9% of the country’s greenhouse gas emissions and are on track to increase, according to the White House. The Pennsylvania study was launched in an effort to understand whether the measurements of airborne methane matched up with emissions estimates based on readings taken at ground level, the approach the EPA and state regulators have historically used.
Researchers flew their plane about a kilometer above a 2,800 square kilometer area in southwestern Pennsylvania that included several active natural gas wells. Over a two-day period in June 2012, they detected 2 grams to 14 grams of methane per second per square kilometer over the entire area. The EPA’s estimate for the area is 2.3 grams to 4.6 grams of methane per second per square kilometer. Since their upper-end measurements were so much higher than the EPA’s estimates, the researchers attempted to follow the methane plumes back to their sources, said Paul Shepson, an atmospheric chemist at Purdue University who helped lead the study. In some cases, they were able to quantify emissions from individual wells.
The researchers determined that the wells leaking the most methane were in the drilling phase, a period that has not been known for high emissions. Experts had thought that methane was more likely to be released during subsequent phases of production, including hydraulic fracturing, well completion or transport through pipelines. The airborne readings were a snapshot over two days, Shepson cautioned, and further research over a longer period and at other sites are needed to know whether the Pennsylvania measurements are typical.
Much of the natural gas drilling in southwestern Pennsylvania goes through coal beds, which contain methane that might be leaking out, according to the study. The researchers speculated that underbalanced drilling methods — in which the pressure in the well-bore is lower than the surrounding geology — allows fluids and gases to enter the well-bore and travel to the surface. Energy producers use underbalanced drilling because it allows them to capture valuable supplies of ethane and butane, Shepson said.
…
Last year, researchers from Stanford, Harvard and elsewhere reported in PNAS that methane emissions in the continental U.S. might be 50% greater than the EPA’s official estimates. Another study by Stanford researchers, published in February in the journal Science, also concluded that the EPA underestimates methane leakage from the natural gas industry and other sources. The new study comes two weeks after the White House ordered the EPA to identify ways to cut methane from oil and gas production. If the agency decides to issue new rules, they must be in place by the end of 2016.
In February, Colorado became the first state to regulate methane emissions from the oil and gas sector, requiring the industry to detect and fix leaks and install equipment to capture 95% of methane emissions. Last week, Ohio adopted rules to get companies to reduce methane leakage from above-ground equipment used in natural gas development, like valves and pipelines. Those rules do not appear to address leaks during drilling. [Emphasis added]