What the "frack" is going on with shale gas??

In the face of rising global energy demands and related greenhouse gas emissions, it is imperative of finding greener, alternative sources of energy that address these concerns. Natural gas, which burns more cleanly than other fossil fuels, emitting approximately half of the CO₂ levels compared with the burning of coal and 30% less than fuel oil, is growing as an alternative fuel source.

Figure 1. Underground sources of natural gas.

Certain underground rock formations have historically been viewed as "unconventional" gas resources because of the difficulty in accessing and extracting the gas they contain.  Examples of these formations include: coalbed methane, tight sand gas, and gas-rich shale (Figure 1).

                    

Figure 2. Black shale rocks.
Approximately 60% of  the U.S. onshore gas reserve
is trapped  in  rocks like this.

Organic-rich shale rocks are known to retain an immense volume of natural gas on the grains and within the extremely small pore spaces of its structure, much like a sponge holds water. 

Current technological advances in drilling and fracture stimulation technology (e.g. hydraulic fracturing) have successfully enhanced access to the trapped gas within the tight rocks, turning shale into a more economically viable energy source.Chesapeake Energy hydraulic fracturing method 

Figure 3. Diagram of shale gas extraction.

Figure 4. U.S. EIA (Energy Information Administration) Projections. 

Because of advances like these, by 2035, it is projected that shale gas will contribute to almost half of natural gas production in the U.S. (Figure 4.)

However, numerous questions and concerns are arising regarding the environmental effects of such practices, with particular concern of the hydraulic fracturing fluids used to extract the gas.  What are the chemicals in the “frack” fluids?  How do these fluids interact with the shale rock?  What will happen to the integrity of the shale reservoir and surrounding rocks over time?  Will residual fluids left underground become trapped within the fractures and pore spaces, ultimately inhibiting further natural gas generation or extraction over time?

My work ultimately aims to determine the chemical and physical interactions of different types of fracking fluids on shale rock formations and determine their impact on gas recovery efficiency.  A more complete and quantitative understanding of the impacts of hydraulic fracturing fluids in shale reservoirs is imperative if we are to continue to depend on natural gas as a major energy resource.

References:

http://www.ems.psu.edu/~pisupati/ACSOutreach/Petroleum_2.html (Figure 1 & 4)

http://geology.com/rocks/shale.shtml (Figure 2)
http://www.bbc.co.uk/news/uk-wales-14352989   (Figure 3)
http://www.eia.gov/naturalgas/
http://www.naturalgas.org/overview/unconvent_ng_resource.asp

U.S. Department of Energy (DOE), Office of Fossil Energy and National Energy Technology

Laboratory, 2009.  Modern Shale Gas Development in the United States: A Primer. 

DE-FG26-04NT15455.3-5.