Abstract: A method of putting under gas a saline cavity 3 for storing a gaseous substance, the cavity being formed by being washed out in rock salt and being filled with brine 5 once the washing-out step has been completed, the cavity includes a bottom 31 and a roof 30, a well 1 drilled for washing-out purposes opening out in the roof and putting the saline cavity into communication with the surface, the well also serving as an injection well for inserting the gaseous substance to be stored. The method includes a step of drilling an associated dewatering well 4 from the surface in the proximity of the injection well, the dewatering well meeting the saline cavity close to the bottom thereof so as to dewater the brine from the cavity through said dewatering well as the gaseous substance is injected into the cavity via the injection well.

Abstract: In order to provide safety in a borehole communicating in particular with a cavity washed out from rock salt and containing gas under pressure, the prior art provides devices suffering from the drawback of reducing the flow sections through the tubes in the borehole. The present invention minimizes this section reduction by means of a hollow cylindrical sleeve closed inside by a plug and including ducts formed in its wall in such a manner as to cross over the flows of fluid taking place respectively in a central tube of the borehole and in the annular space between the central tube and a peripheral tube. In one embodiment of the present invention, the sleeve is sandwiched between portions of the central tube and of the peripheral tube, with safety valves advantageously being mounted on the portions of central tube above and below the sleeve.

Abstract: A storage device has an inner enclosure (6) and a leakproof and a rigid outer enclosure (5), which are mounted one inside the other and separated by an intermediate space (9) containing a fluid, continuous in phase at pressures other than that of the material stored, and pressure measurement equipment (16, 15) enabling the differences in the pressure of the fluid to be monitored. Advantageously, the device additionally features sampling equipment (18, 17) enabling the composition of the fluid to be monitored. The device may be buried, the outer enclosure being then placed against the cement walls (4) of a cavity, which may be a drilled well. The inner enclosure may feature a leakproof skin which is made rigid by the presence in the intermediate space of a porous and rigid filling material in which the fluid can circulate.

Abstract: A safety device for a tube (8) for inserting or removing a liquid substance for storage in a storage facility in a cavity in a water-impregnated rock mass, said liquid being the liquid phase of a substance which is a gas at ordinary temperature, which liquefies under pressure, which has a density which is less than the density of water and which is immiscible with water, said liquefied gas being stored in said cavity under the liquid-gas equilibrium pressure applicable to the ambient temperature in the cavity, the safety device being constituted by a can (9) which is open at the top and which is disposed around the bottom end (81) of the tube to which it is applicable such that the bottom opening of the tube (8) is located near to the bottom of the can, the volume of the can being greater than the volume of the tube up to a height corresponding to the head of water necessary for reaching an equilibrium pressure with the cavity.

Abstract: The imperviousness of an underground storage cavern for hydrocarbons in a water-impregnated rock formation is predicted and monitored by progressively increasing the pressure in the cavern and using pressure sensors placed around the cavern to monitor the gradient of the hydraulic pressure potential .phi. in the rock formation during the pressure rise in order to check that the gradient is not inverted.

Abstract: A draining well (2) extending downwardly from the bottom (3) of an underground cavity for storing liquefied gas under pressure has an upper portion (9) of large area and a lower portion (10) of smaller area. The volume of the upper portion is sufficient for filling a service tube (5) with water up to its hydrostatic equilibrium level. This enables the depth of the draining well to be reduced and thus makes such a storage facility cheaper to produce.

Abstract: When a product such as ammonia, which is liquefiable under pressure and which is miscible with water is stored underground the storage takes place at the liquefaction pressure of the product and inside a double skin which defines an intermediate space (10), with both skins being inserted in a cavity (1) formed in a water-impregnated formation. The depth of the storage is so chosen that the hydrostatic pressure of the water in the formation is greater than the greatest expected pressure of the stored product, with the intermediate space being filled with water and being maintained at a pressure which is lower than the lowest expected pressure of the stored product. If the inner skin is punctured, NH.sub.3 is recovered in the water in the shaft (2) and does not escape to contaminate the water in the surrounding formation.

Abstract: During the process of cooling, the stresses in the earth pass first through a maximum compression and then this gives place to traction up to the moment when fissures appear. The application of cooling is conducted so as to reduce the size of these fissures and to prevent their propagation through the compressed zone. They are plugged preferably by spraying water in the course of application of cooling.

Abstract: In order to form galleries or other subterranean cavities in the bed of a sheet of water, for example for the construction of a subterranean reservoir for storing petroleum, or for exploiting submarine deposits, a floating structure, comprising at least one and preferably two hollow shafts, is ballasted so that it rests upon the seabed or underwater surface, a bore is excavated in extension of each hollow shaft, down to the desired depth, a casing tube is inserted there, extending to above the sheet of water, and one of said casings is used as an access means for the excavation of the galleries or cavities, whilst the other if used to remove the spoil.