Storage technology
The injection and withdrawal of gas determine the workflows at a storage facility.
Injection
- Every gas storage facility is connected to the mains network of a gas distribution company by means of an underground pipeline, through which the gas flows to and from the facility.
- Incoming gas flows first through a filter, which separates solid matter and liquids from the gas. Then the gas flows through a calibrated volume gauge.
- Before the gas can be injected into the storage facility, the pressure has to be increased by means of compressors driven by a gas motor or turbine.
- Gas coolers dissipate the heat generated by the compression process.
- Finally the gas is fed into the wells via high-pressure pipes and then injected into the storage formations.
Withdrawal
Gas is withdrawn from the reservoir through the same wells it was injected in through.
Gas absorbs water while in the reservoir. This water has to be removed to avoid any corrosion or blockage of the mains network through the formation of gas hydrates.
- In a first step, free droplets of water are separated from the gas and injected into a water disposal well.
- The gas is then preheated to ensure that no gas hydrates are formed in the processing plant after the pressure of the gas has been reduced to mains pressure.
- The gas is dehydrated in a glycol absorption plant. Thanks to its hydroscopic nature glycol absorbs the water vapour contained in the gas.
- Now the gas is now in the same state it was when delivered to the storage facility. After passing through a calibrated volume gauge, it is returned to the gas distribution company
The withdrawal process described above is dependent on the reservoir pressure being high enough for the gas to be forced into the mains network. If this is no longer case towards the end of the withdrawal process, compressors are again employed to raise the pressure.
The operating area
The underground storage of natural gas requires relatively little space for the installations on the surface. Each natural gas storage facility includes one or more collector locations for the wells, a compressor installation, systems for the measurement of gas quantity and quality and a continuously manned control centre, equipped to control and monitor the entire facility.
