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| Fig. 1: Schematic showing process involved in fracking. (Source: Wikimedia Commons. Courtesy of the EPA) |
Fracking, also known as hydraulic fracturing, is the process of mainly extracting natural gas from shale deposits through drilling and applying pressure through a mixture of water, sand and chemicals. In this process, the pumped water, chemicals and sand causes formation of cracks (fractures) in the rock, unlocking the hydrocarbons trapped in shale and allowing natural gas extraction (see Fig. 1). [1] The process uses granular solid size sand particles, called propane, that wedges open the expanding cracks. These proppants keep the cracks open, allowing hydrocarbons to flow more easily to the surface. [2] Although fracking can also be used to extract oil, it uses in extraction of gas is particularly significant economically. Gas production has been rising over years as a result. Moreover, the Energy Information Administration (EIA) projects that the natural gas production through fracking will rise from about 26 Trillion cubic feet (Tcf) in 2019 to about 40 Tcf in 2050 (see Fig. 2). [3] However, this bullish prediction is based on on coarse-grained studies of major shale formations, or plays. There are physical models that describe how the gas production depletes over time; typically the gas production rate follows inverse square root of time relation at the beginning and after some time, called interference time, it starts to follow exponential decay in time. [4] Thus, projection based simple power-law extrapolations can lead to overly optimistic projections in the long run. At the end of the day, realistic forecasts might lead to a better understanding of the economic importance of fracking, and how much can US rely on it for its natural gas demand.
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| Fig. 2: EIA assessment of market natural gas production in the US from both fracking and non-fracking sources - reference case. [3] (Courtesy of the EIA) |
Because of the use of chemically mixed water, fracking has unintended consequence of groundwater contamination. Hydraulic fracking fluid may potentially be chemically hazardous, and therefore its ground leakage could contaminate surrounding areas. Moreover, fracking has large amount of chemically mixed wastewater as byproduct, which require treatment, and the sheer amount of quantity involved makes the treatment a challenging issue both technologically and environmentally. Moreover, the treated waters are often disposed through injection well, but such disposal method has been shown to cause small earthquakes. Several cases have been reported in which earthquakes large enough to be felt but too small to cause structural damage were associated directly with fracking. [5]
Although fracking is an important source of natural gas, it is highly controversial, and oftentimes dominates the political discourse. Its proponents often highlight the jobs it has created whereas its opponent say it is a distraction for energy firms and governments from investing in renewable energy, thus encouraging continued reliance on fossil fuels.
© Dinesh Kandel. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] R. K. Craig, "Hydraulic Fracturing (Fracking), Federalism, and the Water-Energy Nexus," Idaho L. Rev. 49, 241 (2013).
[2] A. Vaughan, "Fracking - The Reality, The Risks and What The Future Holds," The Guardian, 26 Feb 18.
[3] "Annual Energy Outlook 2020", U.S. Energy Information Administration, 29 Jan 20.
[4] T. W. Patzek, F. Male, and M. Marder, "Gas Production in the Barnett Shale Obeys a Simple Scaling Theory," Poc. Natl. Acad. Sci. (USA) 110, 19731 (2013).
[5] W. L. Ellsworth, "Injection-Induced Earthquakes," Science 341, 1225942 (2013).
