When designing a rock cavern for gas storage, the major issue is the storage ca- pacity, which is controlled by the maximum gas pressure. A storage with a water curtain will have a limitation of pressure of 150–200% of the natural groundwater pressure due to jacking effects in the rockmass. Numerical experiments of the geohydrological situation around a storage with an increasing degree of variance in the hydraulic conductivity imply that a design based on a homogeneous conductivity is conservative.
Dans la construction d"une cavite rocheuse pour l"emmagasinage du gaz le but principal est la capacite qui est dependante de la pression maximum du gaze Un emmagasinage avec rideau aquatique aura une pression limite correspondant de 150 à 200% de la pression intersticielle cela du à l"expansion des fissures du massif rocheux. Des etudes numeriques de la situation geohydrologique autour d"un magasin avec une augmentation du degre de variation de la conductivite hydraulique mont rent qu"une construction basee sur une conductivite homogène est conservatrice.
Beim Projektieren einer Felskaverne fuer Gaslagerung ist die Lagerungskapazitat der Hauptzweck. Sie ist abhangig von dem maximalen Gasdruck. Das Lagern mittels eines Wasservorhangs wird den Druck auf 150 bis 200% des natuerlichen Grundwasserdrucks begrenzen infolge der Durchlassigkeit im Fels. Numerische Experimente mit der geohydrologischen situation um einen Lagerraum mit zunehmend veranderlicher hydraulischer Konduktivitat deuten auf eine schutzende Wirkung hin beim Projektieren auf Basis einer homogenen Konduktivitat.
The gas pressure and, consequently, the mass of gas, that can be stored in an unlined cavern depends on the groundwater pressure acting in the surrounding rock fractures and pores. By increasing the pressure in a water curtain beyond the actual ground water pressure in the rock mass it will thus be possible to increase the storage capacity.
Since the amount of gas stored will vary with time, one advantage with an over pressurized concept is that the maximum pressure of the stored gas is not directly determined by the hydrostatic pressure. Instead, the volume of the storage can be reduced and the exceeding gas volume be compensated for by increasing the curtain pressure.
In order to assure gas tightness at pressures above hydrostatic, the curtain pressure must continuously be monitored and varied in order to keep a reasonable safety margin against gas leakage at all times. The principle for this is shown in figure 1.
The gas pressure in the storage is limited by the water pressure in the curtain. This water pressure is, in turn, limited by the risk of hydraulic jacking of the rock mass. A water curtain will encircle a relatively large volume of rock; jacking means opening of existing fractures by decrease of the effective stresses across the fracture plane until shearing of the
(Figure in full paper)
Figure 1. Required water pressure in the curtain to maintain gas tightness for a storage with an overpressurized curtain.
