In Coal Bed Methane (CBM) wells, the wellbore initially produces high volumes of water, often for significant periods of time. However, once the target reservoir has been depressurized by removing the water, the average production curve is relatively steady.
In tight gas and shale gas wells, the production curve is slightly different. In these instances, the natural gas is found both as free gas around the rock structure and within the rocks themselves. Once the wellbore reaches the target zone and hydraulic fracturing has been successful, the free gas flows quickly, causing an initial spike in production. Production then plateaus as the natural gas absorbed in the rock itself is removed. Thus for a typical shale gas well, production declines between 70-90 per cent in the first year, with an overall average well life of 20-30 years.
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, like for example 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.