From fields to facilities
The former gas fields we turn into storage facilities originated about 22 million years ago, when organic matter in the primaeval ocean that occupied today’s Prealps was trapped by sandstone sediments. The gas migrated into the pores of the sandstone, forming gas reservoirs that can have an area of several square kilometres. Layers of clay, several hundred metres thick, above the gas reservoir, prevented any gas from escaping, as they still do today, making underground storage extremely safe. Nature itself has proved this, since the original gas reserves never posed a hazard although the reservoir pressure was much higher.
After the gas has been produced the reservoirs can be re-used as storage facilities. Natural gas is pumped into the depleted structures, taking care not to exceed the original reservoir pressure. The gas is injected and withdrawn via wells. Some surface installations are also required. These include compressors to inject and withdraw the gas under pressure, and equipment to dry and clean it before it is consumed.
All these process units have been tried and tested for many years, and similar systems are at work all over the world. Our storage expertise makes a major contribution to gas supply security in Austria and Central Europe as a whole.
How storage facilities work
When gas arrives at a storage facility via a pipeline network it first enters a metering station where it is filtered, and the quantity and quality are measured. Injection and withdrawal take place via a number of wells. Where necessary, compressors bring the incoming gas up to the right injection pressure. Since compression raises the temperature, the gas must then be cooled before being conveyed to the wellhead and injected into the natural rock formations. Care must be taken not to exceed the original reservoir pressure. The gas is withdrawn when it is needed, and processed for transportation. It must be dried as it will have absorbed moisture in the reservoir. Once it is on specification it enters the grid and is carried to the consumer.