Well head of a gas well
Natural gas
Austria covers around 20 percent of its domestic gas demand from fields north of Vienna, western Upper Austria and Salzburg.
Since 1960 RAG has produced natural gas from reservoirs in concession fields situated in Upper and Lower Austria and Salzburg and operates 117 gas wells with an annual natural gas production of 640 mill. Nm³ (2008).
Scheme of a gas prodction well
Natural gas - production method
Production tubings are installed in the cased and cemented production well reaching from the surface to the lowest point of the newly developed reservoir.
In order to ensure that the gas can flow into the well, casings, cementation and formation is opened by perforations.
On the surface, a so-called christmas tree is installed which allows to shut in the well at any time.
An underground safety valve in the production tubing avoids any uncontrolled gas escape.
Natural gas reaches the surface with a pressure of up to several 100 bars. From the wellhead, it flows into a high-pressure pipeline to the gas treatment facility where it is dehydrated for transport in the distribution pipelines.
Depending on the type of reservoir and depletion, up to 99% of the existing natural gas in place can be produced. When reservoir pressure drops production rates also decrease. This is why additional wells, so-called production wells, are drilled during the production period which help to keep the total rate on a certain level.
Scheme surface - subsurface
Natural gas - treatment
Before natural gas can be delivered to the supply network it must be processed.
The natural gas produced from the reservoir is first dried in dehydration facilities which separate associate reservoir water, liquid hydrocarbons, and solids.
The remaining vapour is extracted from the gas by using glycol.
When the gas leaves the treatment facilities it is ready for use.