Some natural gas wells, compressor stations and processing plants in the Barnett shale in North Texas are leaking far more methane (CH4) than previously thought, potentially offsetting the climate benefits of natural gas, according to a recent study from the University of Houston (UH). The study is one of 11 papers published in the July 7 edition of Environmental Science & Technology, which all examined fugitive CH4 emissions from the Barnett play. Previous study into methane emissions in the Barnett shale area only examined a few aspects of the play, Robert Talbot, professor atmospheric chemistry at UH, told Rigzone in an email statement. The UH study was led by a comprehensive team of experts, and was a bottoms-up and top-down study of emissions.
Natural gas burns more clearly than other fossil fuels, producing more energy per carbon dioxide molecule than oil or coal. But Talbot noted in a statement that CH4, the primarily component of gas, is a potent greenhouse gas. According to the UH paper, CH4 has a global warming potential over a 100-year time frame as high as 34 times than that of carbon dioxide. “In the past decade, the horizontal drilling and hydraulic fracturing techniques have led to a boom in natural gas production,” said Talbot and co-authors Xin Lan and Azucena Torres, graduate students in Talbot’s UH lab at the time of the study, and Patrick Laine, a former post-doctoral research associate.
The researchers conducted their study in a mobile laboratory over a 15-day period in October 2013, testing 152 facilities and driving approximately 2,300 miles. They tested 125 well pads, 13 compressor stations, two gas processing plants, and 12 landfills. The team also measured emissions from a dozen landfills and roads next to natural gas well pads.
Additionally, the research team measured emissions in downward plumes and used two different dispersion models to estimate the emissions rates. The UH team found that well compressor stations and gas processing plants emitted significantly higher rates of methane versus emissions from well pads.
A few individual sites had very high methane loss rates that would make natural gas from these sites worse for the climate than coal in the short-term outlook. “That finding drives interest in determining the prevalence of high-emission sites,” according to the study. Releases at specific installations ranged from .01 percent to 47.8 percent; the median was 2.1 percent. The nine landfills that the team measured also were found to be significant sources of methane emissions. Some of the emissions can be attributed to human error, compounded by the fact that the sites are often left unattended for long periods of time, said Talbot in a statement.
“A lot of them are a broken valve, or someone leaves a hatch open. It’s human error. And nobody goes back to the site for a month or so.” Talbot said the compressor stations and gas processing plants can largely be classified as super-emitters. As more of these are built, these will add to the emissions. In Talbot’s opinion, the high rates of fugitive emissions found in the study indicate that the oil and gas industry is not doing enough to tackle CH4 emissions. “Presumably, the methane emissions rates were low before natural gas fracking began,” said Talbot. “This is all anthropogenic activities that have contributed to the methane emissions. So it likely went from near zero to levels of today.” The Environmental Defense Fund coordinated the studies, with funding from the Alfred P. Sloane Foundation.
Talbot added that he hopes that more U.S. states would follow Colorado in Colorado’s approach to reducing methane emissions. In February 2014, Colorado became the first U.S. state to restrict methane emissions from hydraulic fracturing, Bloomberg reported. Some have said that Colorado’s approach to reducing methane emissions could serve as a model for the entire United States. In January of this year, the U.S. Environmental Protection Agency unveiled plans to regulate oil and gas methane emissions, with the goal of reducing methane emissions oil and gas production by up to 45 percent from 2012 levels by 2025.
The regulations – a move to address environmentalists’ criticism over the Obama administration’s focus on future methane emission versus existing sources – would apply to new drilling equipment and from old and new production facilities on public lands. Methane is the second most prevalent greenhouse gas emitted from human-related activities in the United States, according to the U.S. EPA website. In 2013, methane accounted for around 10 percent of all U.S. greenhouse gas emissions. Some in the oil and gas industry have said that the debate over hydraulic fracturing – including methane emissions – should be based on sound science.
Exploration of the Barnett shale play kicked off the unconventional oil and gas boom in the United States. According to the Railroad Commission of Texas (RCC) website, the Barnett shale stretches from west and south from Dallas, and covers 5,000 square miles and at least 18 counties. The Barnett shale had served as an important source and sealing cap rock for conventional oil and gas reservoirs in the area. But it wasn’t until advances made by Mitchell Energy in hydraulic fracturing and horizontal drilling in the 1980s that the play’s potential was realized. Significant drilling began in the late 1990s when natural gas prices increased.
From January to April of this year, the Barnett shale produced 4.48 billion cubic feet per day of gas, 1,759 barrels per day (bpd) of oil, and 10,717 bpd of condensate, according to the RCC.