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Depleted Oil and Gas Fields

Oil and gas fields that have already been more or less fully exploited are particularly suitable for the underground storage of natural gas. As these structures have successfully kept their hydrocarbon deposits trapped for millions of years, they have already demonstrated their geological suitability for storage purposes. No special exploration is required for this kind of storage and, as an additional advantage, any existing exploitation wells can potentially be re-used for gas injection and gas withdrawal.

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The gas stored in this type of facility is injected under a pressure that is higher than the actual reservoir pressure - so that, when there is an increase in demand for gas, it can be withdrawn by expansion.






The gas turnover rates that can be achieved from such reservoirs are dependent on the dimensions and design of the original exploitation wells and on the properties of the reservoir. To increase gas turnover rates, especially in thin rock layers, new wells are increasingly being drilled in such a way that the lower section of the well runs horizontally along the storage formation. This provides a considerably larger flow area for the gas along with significantly higher injection and withdrawal rates.

When depleted fields are used for natural gas storage, the possibility of any residual gases mixing with the injected gas cannot be excluded. Measures for avoiding quality problems (e.g. by increasing the cushion gas volume of storage gas) may have to be considered, depending on the differences in composition of any residual gas and the storage gas. This is also why gas processing plants are sometimes installed at the surface to guarantee that the gas re-injected into the pipeline has the same quality as the pipeline gas.

Depending on their storage characteristics, depleted fields work equally well for the seasonal balancing of natural gas supply and for peak shaving.

 
 
 
 
 
 
 


























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