Underground Gas Storage Plant (Cavern Storage)
Contrary to popular belief, gas is not extracted, treated and distributed directly to your home. Gas storage plays a critical role in gas distribution and ensures a reliable supply of gas is available for consumers when needed.
There are two main types of underground gas storage; these are the gas cavern type, and the pore storage type. Pore storage allows gas to be stored in porous rock deep underground, whilst cavern storage allows gas to be stored in large underground caverns. Although caverns have a lower storage capacity than pore storage, they can be discharged at a much faster rate.
Gas caverns are often created by injecting water into a salt deposit deep underground. The water slowly dissolves the salt in a process known as leaching. As the salt is dissolved, the volumetric space available for storage within the cavern is increased. Leaching of the cavern usually takes several years, but a long cylindrical cavern is the desired end product.
A typical underground gas storage facility will contain millions of cubic metres of gas maintained at an average pressure of 200 bar. The high pressure allows a larger amount of gas to be stored within the same volumetric space, thus the total amount of gas stored by the cavern can be increased at higher pressures.
Injecting and discharging underground storage facilities is often assumed to be a simple process, but there are numerous machines required and some are large (particularly the compressors). The general process is to inject gas into the caverns using large compressors, then discharge the gas into the national grid. Due to the large pressure changes, significant temperature changes also occur and this adds a layer of complexity to the process.
This 3D model shows all major components associated with a typical gas cavern storage plant, these include:
- Measuring Room
- Water Heater
- Expansion Valve
- Well Head Valve
- Cooling Cell
- Drying Column