Tuesday, September 17, 2013
The New York Times today reported potentially encouraging news from a collaborative study out of the University of Texas: methane leakage rates from hydraulically fractured shale gas wells might be lower than previously estimated EPA rates. The study emerged from a combined effort of gas companies, the Environmental Defense Fund, an independent Scientific Advisory Panel, and academics. It finds that methane emissions from the flowback process--when hydraulic fracturing fluid and some gas (methane) flows back out of the well--range from 0.1 Mg to 17 Mg (with a mean of 1.7 Mg of methane released and "75% confidence bounds of 0.67-3.3 Mg"), as compared to previous EPA estimates of an average of 81 Mg per flowback event. Emissions from pumps and other equipment at well sites, on the other hand, are "comparable to and higher than" EPA estimates. In total, methane emissions from activities at the wellhead might represent "0.42% of gross gas production." These findings are important because organizations like EDF believe that methane leakage rates from the rapidly-growing shale gas resource must be 3.2% or lower for gas to provide a climate advantage over new coal-fired power plants.
But we are not out of the weeds yet. This EDF, university, and industry-led study is only one of approximately 16 studies planned to be published in academic journals by 2014, and the study only addresses leakage at the wellhead. The amount of methane leakage through the entire natural gas system, from production to "gathering & processing, long distance transmission & storage, local distribution, and transportation," is still a murky number.
In addition to lacking definitive evidence that system-wide methane leakage is below 3.2%, we also must understand the limitations of the wellhead study. The study makes excellent progress within the methane leakage debate because it measures actual leakage rates from "150 production sites, 27 well completion flowbacks, 9 well unloadings, and 4 workovers," including 489 hydraulically fractured wells in several regions. But as with any study that must rely on industry cooperation to access data, there is a concern that the researchers measured industry best practices. It is possible, in other words, that the industry actors most willing to participate in the study were those that already used the best methane capture technology and practices and were least worried about the results. Indeed, the study notes that the "dataset is designed to be representative of the participating companies' activities and practices, but not necessarily all activities and practices."
It is not yet clear that the EPA-estimated 25,000 wells fractured or refractured each year use methane capture practices as beneficial as the 489 hydraulically fractured wells in the study. The authors of the Texas-led study indicate that "[m]ultiple methods were used to minimize the potential for bias in the sample set," and they provide a detailed appendix of the study scope and method. The appendix indicates that "[r]epresentative sampling was believed to be achieved by: [s]electing a large number of companies, [s]electing a range of geographic areas to sample," and "[s]electing [a] minimum number of sampling targets in each area." But the appendix shows that the nine mid-size and large companies that participated in the study "account for almost 12% of all U.S. gas wells," "16% of gross gas production," and "almost half of the new well completions." Although this represents a sizeable chunk of industry, it might also represent the most cooperative and progressive chunk. There is some indication that not all companies are amenable to the types of methane capture practices used by these companies. The American Petroleum Institute has complained about the costs of new EPA Clean Air Act rules that will require methane capture or flaring (burning off of gas) similar to the practices used at the 489 wells studied by the University of Texas team. It worries that the "reduced emissions completion" (REC) technologies necessary to achieve this capture rate will not be available in the numbers needed and will slow down drilling and fracturing.
We also need to think about the broader climate impacts of gas, as noted by Patrick Parenteau & Abigail Barnes and others. Although we know that the displacement of coal with gas has benefits far beyond (apparent) greenhouse gas reductions, there is the broader threat of what the Natural Resources Defense Council calls a "fossil fuel lock-in" (link is to video archives of a National Research Council presentation by Kate Sinding of NRDC). The existence of abundant, cheap natural gas threatens to distract us from implementing energy efficiency and renewable energy projects at a rapid rate. MIT researchers have noted that the focus on gas slows down and in some cases stops innovation in areas like carbon capture and sequestration, and the International Energy Agency reminds us that gas is not enough to meet climate goals like stabilizing global temperature rise to 2 degrees Celsius. To make real progress on climate issues, we must rapidly invest in fossil fuel alternatives while continuing to achieve systemwide reductions in methane leakage from gas operations.