Connecting the Dots Between Methane and Gas Leaks

The spotlight is certainly on hydraulic fracking to expand production of petroleum and natural gas (NG). Reporting in Nature (vol. 493; Jan. 3, 2013; p. 12), Jeff Tollefson describes how leaks from new natural gas fields may be as large as 9% of production. Having worked in oilfields as a roustabout, I relate to the ubiquitous nature of gas leaks. Seals and pipe joints leak; pipes corrode from inside and outside…and fail. But leaks may not be the only source. Methane can leak from natural seeps, especially along fault lines. Methane is produced from composting municipal and agricultural waste, including cow burps from feed lots and dairies. Mitigation of methane emission must be tied to the source.

Jeff Tollefson discusses recent reports relating atmospheric methane to leaks. However, connecting the dots from atmospheric methane value to leak rate is not a settled science. The estimates of leak rate, using the same data, vary by as much as 2, with the highest being 9% of production. Despite the uncertainty in the estimates, some will probably select one of the estimates to support their particular agenda.

Since methane is 30 times more potent than CO2 as a greenhouse gas, even a small leak can be significant. Tollefson cites an estimate by Alvarez et al. (Proc. Natl. Acad. Sci. USA 2012, 109, 6435–40) that the equivalence point is 3.2% of production. Above this value, methane emissions contribute more to global warming than the CO2 from combustion of the NG. However, NG wells can produce millions of cubic feet per day, so even a 2% loss is still a large number.

A paper by Gupta and Leen (http://www.americanlaboratory.com/913-Technical-Articles/129080-Field-Portable-Analyzers-Based-on-Cavity-Enhanced-Laser-Absorption-Spectrometry/) shows that atmospheric methane can be measured from aircraft using cavity-enhanced laser absorption spectrometry. One application shows elevated methane concentration along a track of a major NG pipeline in California. This reminds me of the pipeline disaster in San Bruno on September 10, 2010.

Quo vadis? Since natural gas is difficult to contain and ship, it may be better to convert it to electricity near the wellhead. As I’ve advocated earlier, the CO2 from the combustion could be recycled to the producing formation, which should aid in secondary recovery.

I’m intrigued with the rapid development of science relating to fracking. I intend to report in as news appears. We welcome your comments.

Robert L. Stevenson, Ph.D., is a Consultant and Editor of Separation Science for American Laboratory/Labcompare; e-mail: rlsteven@yahoo.com.

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