Low Methane Leakage from Shale Gas Wells Verified
Critics of shale gas development have frequently charged that methane leaks and emissions from shale gas operations are high enough to present no real advantage over other fossil fuels from a greenhouse gas standpoint. However, recent study conducted by the University of Texas and the Environmental Defense Fund (yes, you read that correctly) concluded that emissions from shale gas operations were not only much lower than expected but were on the order of 50 times lower than previous estimates by the US Environmental Protection Agency. These numbers confirm that shale gas, when displacing coal and oil as a fossil fuel for power generation, will result in significant climate change benefits.
The issue of methane emissions from shale gas operations has been the subject of debate for several years. Methane is a potent greenhouse gas, over 20 times more potent than CO2. The data that could accurately establish the level of methane emissions would be important in the continuing debate over fossil fuels and their role in climate change. A 2011 study by Cornell University showed shale gas methane emissions in the range of eight percent – in other words eight percent of the gas produced by a well was leaking into the atmosphere. This amount of leakage would clearly reduce any claims of climate change benefits associated with increasing shale gas use. While critics of the study claimed it was flawed, Cornell found some researchers at the National Oceanic and Atmospheric Administration who supported the study; consequently, the debate raged on.
Several subsequent studies including those by the University of Maryland, the US Department of Energy and the Sierra Club (yes, you read that correctly also) all pointed to much lower emission rates from shale gas development than the eight percent cited by the Cornell study. These studies generally put the leakage rate at below two percent. The first phase of the UT-EDF study, being the latest and perhaps the most comprehensive, put the leakage emission rate at or below 1.5 percent. Previously, several climate change related studies had suggested that shale gas related leakage rates had to be at or below 2 percent to show a net positive gain on greenhouse gas emission rates. Unfortunately, it appears that no final conclusions can be drawn from these first phase results. While well completions, especially those utilizing “green” completion techniques, scored below EPA estimates, some specific phases of shale gas production operations were either higher or lower than EPA estimates. Pneumatic devices, in particular, showed considerable regional variation. These devices, and liquids unloading operations, will be the focus of the second phase of the study.