by Emil Morhardt
How long will shale gas be available until it plays out? The Bureau of Economic Geology (BEG) at the University of Texas at Austin is making a concerted effort to find out for the four largest shale plays currently in development in the US. The first they reported on was the Barnett Shale in Texas. The topic of this post is their second study, conducted on the Fayetteville (Arkansas) Shale by John Browning and eleven colleagues at the BEG. The overall answer is a long time—but well short of a century—with production peaking soon and falling to between half and a third of the current levels by 2030 and continuing to decline thereafter; they ran their model through 2050 and estimate the technically recoverable gas resources if economics were not an issue (38 trillion cubic feet), and the amount likely to be recovered eventually given economic reality, about half that.
The article. Published in the Oil & Gas Journal (Browning et al. 2014) gives insight into the complex modeling required to come up with a credible answer. The authors looked at the gas production history of every (3,689) well drilled in the basin up to 2011, mapped their estimated 30–year productivity in a fine grid across the 2,737 square mile study area, extrapolated that productivity to nearby areas, and concluded that only about a third of the economically feasible wells have yet been drilled. As one would expect, all of their estimates are highly dependent on assumptions entered into the model, perhaps the most uncertain of which is the price of natural gas—if it is high, many more wells will be drilled than if it is low, but the model can accommodate just about any likely variation, so as more information appears over time, it will be a snap to rerun it.
I recommend this paper for its clear treatment of a difficult subject. For an example of a much more technically challenging description, try reading Patzek et al. (2013) by three of these same authors (which I discussed here on December 22).
Browning, J., Tinker, S.W., Ikonnikova, S., Gülen, G., Potter, E., Fu, Q., Smye, K., Horvath, S., Patzek, T., Male, F., 2014. Study develops Fayetteville Shale reserves, production forecast. OIL & GAS JOURNAL 112, 64-+. http://www.beg.utexas.edu/info/docs/Fayetteville%20Shale%20OGJ%20article.pdf
Patzek, T.W., Male, F., Marder, M., 2013. Gas production in the Barnett Shale obeys a simple scaling theory. Proceedings of the National Academy of Sciences 110, 19731-19736.