<p>In recent years, the energy potential of unconventional gas reservoirs and especially shale gas has prompted strong interest from governments, business, and research sectors, leading to growing investments in exploration and development. In light of the projected growth in energy demand, natural gas is also often portrayed as a cleaner alternative to oil and coal (in terms of CO<sub>2</sub> emission per unit of energy) as well as a suitable back-up capacity for renewable energy. The current shale gas boom in the USA has spurred interest in other regions of the world.</p>