Thermische Einflüsse auf das Salzgebirge während der Kavernenherstellung am Beispiel einer Erdgasspeicherkaverne in Bremen

The thermal equilibrium of salt formations is permanently disrupted through the solution mining process during the construction of a natural gas storage cavern. The main reason for this is the customary use of cold surface or well water as well as the solution enthalpy of the rock salt itself. Heat is drawn out of the formation and a temperature sink is formed in the cavern area. The geothermal gradient, which has an average value of 2,5 K/100 m in Middle European salt domes, becomes zero or even negative. This has a great influence on the gas temperature later in the storage operation. Thus, for example, gas in the lower part of the cavern is significantly colder than in the upper part and so it is not at all subject to thermal convection. This has a positive effect on the distribution of the water vapor in the gas. In the course of the history of the operation of natural gas storage cavern, it is true that the salt formation is warmed up again by virtue of its own heat supply, however the disruption still remains in the immediate cavern area. On the basis of temperature measurements taken during the solution mining process of a cavern in Bremen, Germany, belonging to Mobil Erdgas-Erdol GmbH, the expanse of the temperature sink in the salt formation was calculated. The results serve as input data for the prediction of the gas temperature during gas withdrawal.