Different Types of Reserves: Tight Gas and Shale Gas
With the focused expansion of domestic production, alongside “conventional” reserves, the so-called “unconventional” reserves are increasingly falling under the spotlight for we need to increase the production of these unconventional reserves to partially compensate for the falling domestic production of natural gas.
“Unconventional natural gas deposits” can be described as deposits that are difficult to access, in which the natural gas has to be mobilized using special technology before it can be extracted. Furthermore, a distinction is made between the different types of unconventional deposits – based on where the gas is and how tightly it is embedded. There are two main types of unconventional deposits in Germany: tight gas and shale gas deposits.
“Unconventional natural gas deposits” can be described as deposits that are difficult to access, in which the natural gas has to be mobilized using special technology before it can be extracted. Furthermore, a distinction is made between the different types of unconventional deposits – based on where the gas is and how tightly it is embedded. There are two main types of unconventional deposits in Germany: tight gas and shale gas deposits.
Tight gas is natural gas that has gathered in small, poorly connected cavities between the rocks (mostly sandstone). Because this rock is not very porous the natural gas cannot flow freely to the well. The production of tight gas has been part of our energy supply for a long time. The technology for producing tight gas, called hydraulic fracturing, has been in use worldwide for 50 years. The extraction of tight gas from sandstone layers in Germany, such as in Lower Saxony, has also been tried and tested very successfully. Wintershall itself has been producing natural gas from unconventional reserves for many years – in the Netherlands, Russia, Argentina and Germany, where Wintershall has participated in a total of 117 production operations for tight gas since 1978.
With shale gas the gas has remained in the rock where it formed, the bedrock, and has not migrated to more permeable rock. The gas here is largely trapped in the surfaces of the rock particles. The production process for shale gas is much more complicated than for tight gas. More procedures are necessary to create the channels for the gas to flow through (so-called “fractures”), and a much higher volume of fluids is required than with the production from “tight gas” deposits – since sandstone (tight gas) is naturally more porous and permeable than shale rock (shale gas).
With shale gas the gas has remained in the rock where it formed, the bedrock, and has not migrated to more permeable rock. The gas here is largely trapped in the surfaces of the rock particles. The production process for shale gas is much more complicated than for tight gas. More procedures are necessary to create the channels for the gas to flow through (so-called “fractures”), and a much higher volume of fluids is required than with the production from “tight gas” deposits – since sandstone (tight gas) is naturally more porous and permeable than shale rock (shale gas).
