ABSTRACT:

Water curtains comprise an interesting method to enhance the storage capacity of compressed, unlined gas storage and have been used for more than 20 years for this purpose. At the Röda Sten Rock Laboratory (RSRL), operated by Chalmers University of Technology, tests were performed in a pilot-scale rock cavern, explicitly constructed for gas storage experiments. The tests showed that no gas leakage occurred, provided the water curtain pressure, at all points, was higher than the gas pressure. At gas pressures above 1.0 MPa, complete gas containment was not achieved due to hydromechanical breakdown of the rock mass caused by the water curtain pressure.

RÉSUMÉ:

Les rideaux d'eau representent une methode interessante pour augmenter la capacite d'emmagasinage des depots sans doublure de gaz sous pression. Au laboratoire des roches de Röda Sten, en activite à I'Ecole Polytechnique de Chalmers, des essais dans une caverne pilote à l'echelle, exclusivement construite pour I'emmagasinage des gaz, ont ete effectues. Ces essais montrent qu'aucu ne fuite de gaz n'a eut lieu aussi longtemps que la pression du rideau d'eau etait en tous point s superieure à celle du gaz. Pour des press ions de gaz superieures à 1.0 MPa, une retenu e complete du gaz ne fut pas realisable à cause de Ie rupture hydromecanique de la masse rocheuse, causee par le pression du rideau d'eau.

ZUSAMMENFASSUNG:

Wasservorhange umfassen eine interessante Methode zur Erhöhung der Lagerungskapazitat beim Lagern von Gas unter Druck, in Raumen ohne Verkleidung. Sie haben seit ueber 20 Jahren fuer diesen Zweck Verwendung gefunden. Im Felslabor Röda Sten Rock Laboratory (RSRL), betrieben durch die Techni sche Universitat Chalmers, wurde eine Modellversuchsanlage einer Felskaverne geprueft, die ausdruecklich fuer Versuche mit Lagern von Gas konstruiert worden war. Die Pruefungen zeig ten keine Gaslecks an, unter Voraussetzung daβ der Druck des Wasservorhangs, an allen Punkten, höher war als der des Gases. Bei Gasdruecken ueber 1,0 MPa wurde kein vollstandiger Gaseinschluβ erreicht wegen hydromechanischer Zerteilung der Felsmasse verursacht durch den Druck des Wasservorhangs.

1.
INTRODUCTION

Storage of gas underground dates back to the beginning of the century when depleted gas and oil fields in the USA were used for this purpose. Even today, aquifer storage is widely used where an appropriate geology can be found. Another method where the geological conditions are used as a natural seal to prevent the gas from escaping is storage in leached salt formations. However, nature has only formed such geological settings in certain areas. Storage in hard rock geologies must be based on man-made caverns to create the necessary volume. Storage of pressurized gas in such caverns can be divided in two categories; lined and unlined caverns, where the former has a gas-tight membrane of steel or plastic attached to the cavern walls. For any unlined storage, gas containment depends on the presence and pressure of water in the rock mass around the storage. The water pressure situation, and thus the gas containment capacity is combined effect of the natural ground water pressure and the influence from the storage. Control of the water pressure in the rock mass prevents leakage and increases the gas containment capacity; such control is possible by the use of a water curtain. The following paper summarizes the most important results of a series of tests performed in a pilot- scale cavern at the Röda Sten Rock Laboratory (RSRL), operated by Chalmers University of Technology, Sweden. The material was presented as a doctoral thesis by the senior author (Söder. 1994).

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