While conventional gas resources can be developed and produced without any special well completions, most unconventional gas production requires the rock to be hydraulically fractured (“fracked”) or stimulated to allow natural gas to escape from the low-permeability rock and flow through the wellbore to the surface. These special well completions made drilling for unconventional gas uneconomical for many years.
Of note, on this website we adhere to the international classification of tight gas within the group of unconventional gas, followed by e.g. the International Energy Agency (IEA). In some countries, such as Germany, tight gas has been produced successfully for many years since the 1990s. Given the long experience with these reservoirs, many experts no longer categorize tight gas as unconventional gas.
While the potential of unconventional gas has been known for centuries, it was only towards the end of the 20th century that the combination of two existing technologies - horizontal drilling and hydraulic fracturing - made extracting unconventional resources an economically viable option.
Currently, there are approximately 60 years of proven reserves of natural gas at current demand levels, but according to the IEA, this rises to more than 250 years if the unconventional gas potential is added. Globally, the IEA estimates there to be 781 trillion cubic meters (tcm) of total technically recoverable natural gas resources and 344 tcm of technically recoverable unconventional gas resources globally, 19 tcm of which are located in Europe.