1. Amer A, Chinellato F, Collins S, Denichou JM, Dubourg I, Griffiths R, Koepsell R, Lyngra S, Marza P, Roberts IB (2013) Structural steering—a path to productivity. Oilfield Rev 25(1):14–31
2. API (American Petroleum Institute) (2009a) Environmental protection for onshore oil and gas production operations and leases. API recommended practice 51R, 1st edn. American Petroleum Institute, Washington, DC. http://www.api.org/~/media/files/policy/exploration/api_rp_51r.pdf . Accessed 22 Feb 2015
3. API (American Petroleum Institute) (2009b) Hydraulic fracturing operations—well construction and integrity guidelines. API guidance document HF1. American Petroleum Institute, Washington, DC
4. Arthur JD, Bohm B, Coughlin BJ, Layne M (2008) Evaluating the environmental implications of hydraulic fracturing in shale gas reservoirs. ALL consulting. http://www.all-llc.com/publicdownloads/ArthurHydrFracPaperFINAL.pdf . Accessed 22 Feb 2015
5. Barker JF, Fritz P (1981) Carbon isotope fractionation during microbial methane oxidation. Nature 293:289–291