When the world thought that we had hit the peak of oil and gas production in the 2000s and that we had to focus on developing alternative renewable energies, newly developed technology to extract unconventional reservoirs made the production of shale gas in the US jumped from 1% in 2000 to over 20% by 2010. (https://www.chathamhouse.org/publications/papers/view/185311) This rapid growth, predicted to by the US government’s Energy Information Administration, is going to continue that 46% of the US’ natural gas supply will be provided by shale gas. There is no doubt that the unconventional oil and gas exploration will continue to grow globally with the growing technology. Unconventional drilling produces hydrocarbons directly from source rock layers or tight rocks (poor quality rock layers that contain migrated oil and gas) through horizontal wells. Although there is still an on-going debate on the precise definition of unconventional oil, in this essay we use the definition made by the IEA World Energy Outlook (WEO) in its 2011 report: “[u]nconventional oil include[d] extra-heavy oil, natural bitumen (oil sands), kerogen oil, liquids and gases arising from chemical processing of natural gas (GTL), coal-to-liquids (CTL) and additives.(https://www.iea.org/publications/freepublications/publication/WEO2011_WEB.pdf) Unconventional oil and gas are harder and more expensive to exploit, however, due to the increasing demand of oil and the continuous shift from coal to natural gas in electricity production, companies and governments have invested heavily in developing unconventional drilling methods. The most typical unconventional drilling method is the implementation of horizontal wells. They are drilled vertically downwards until reaching the target source layer and curve into a horizontal direction which runs a long distance laterally to give the wellbores extended contact with the formation. The advantage of horizontal wells is the long and constant exposure to source rocks. For example, a vertical well p>