GB2457399A

GB2457399A - Underground gas storage in flexible, inflatable containers

Info

Publication number: GB2457399A
Application number: GB0909515A
Authority: GB
Inventors: Victor Arthur Johnson; David Hamilton
Original assignee: CARLTON HOLDINGS Ltd
Current assignee: CARLTON HOLDINGS Ltd
Priority date: 2006-02-27
Filing date: 2009-06-03
Publication date: 2009-08-19
Anticipated expiration: 2026-02-27
Also published as: GB2457400B; GB0909515D0; GB2435505B; GB0603815D0; GB0909516D0; GB2435505A; GB2457399B; GB2457400A

Abstract

An underground gas storage apparatus and method feature the bulk storage of gas, such as methane, in an underground cavity, such as a disused mine, in flexible and gas inflatable containers. The containers may be placed underground by transporting them down a mineshaft in a deflated condition. The inflation of the containers may be controllable remotely at ground level, or underground using apparatus more proximate the containers depending underground safety conditions. The apparatus and method may find application in the long term storage of bulk quantities of methane or other similar fuel gas.

Description

IMPROVEMENTS IN OR RELATING TO UNDERGROUND GAS

STORAGE

Field of the Invention

The present invention relates to underground gas storage.

Background to the Invention

It is known to provide bulk storage of natural gas and/or methane gas for domestic and commercial energy requirements, in large underground cavities. In the case of natural gas, when a natural gas field has been discovered, the natural gas is extracted to provide for the energy needs of industry, and for domestic use. When a natural gas field is depleted, there remains a large underground cavity, into which, natural gas can be pumped into, for storage. A depleted gas field can become a bulk storage device into which surplus natural gas can be is stored underground.

Bulk natural gas storage presents several economic opportunities for gas industry operators. When the price of gas is low, operators can buy up gas and store it in large underground reservoirs. When the price of gas rises, the gas can *...20 be extracted and sold at a higher price. Significant arbitrage opportunities arise : for gas operators having bulk gas storage facilities. S...

It is also known to use other types of underground cavities for bulk storage of natural gas. Various examples known in the prior art disclose brick lined or concrete lined cavities having a gas impermeable membrane. The gas impermeable membrane may either be a plastics material such as bitumen, or tar, or may be a plastics or metal liner.

Other types of underground cavity require excavation of a void space, prior to brick or concrete lining, and fitment with an internal gas impermeable membrane. However, this type of underground gas storage facility is limited by P1 982 spec the requirement for land which to excavate, and the difficulties of making large excavations in the ground.

Known methods for converting an underground cavity or mine working for gas storage suffer from the problem that the surrounding rock may be permeable to gas, and therefore the cavity needs lining in order to prevent escape of gas into the surrounding rock strata. This is overcome by lining the cavities with an impermeable liner. However, in general, the cavities may have rough walls, roofs and floors, and therefore need to be stabilised before inserting a gas impermeable liner.

Lining an underground cavity generally involves having manual access to the cavity, and sufficient space to install a concrete liner, or to provide a block work lining, and a gas impermeable membrane.

Various systems for bulk storage of gas above underground are known. In these systems, a hemispherical dome shaped structure is used to contain gas.

An example is disclosed in EP 033698 B. However, such above ground gas storage facilities require a large area of land for their installation, planning :20 permission, and a high degree of maintenance, being exposed to the external atmosphere. Further, being above ground storage solutions, there is always the : ** inherent risk of a gas explosion above ground.

Summary of the Invention

:.: 25 According to a first aspect there is provided a method of storing natural gas underground comprising: installing one or a plurality of inflatable and deflatable gas storage devices in an underground cavity, each said gas storage device comprising a flexible gas impermeable membrane; and P1 982.spec inflating said one or plurality of gas storage devices with natural gas.

According to a second aspect there is provided a method of bulk gas storage for storing natural gas in an underground cavity, said underground cavity being connected with a terminal position via a passage, said terminal being s present at a first end of said passage and said cavity being present at a second end of said passage, said method comprising: inserting an inflatable and deflatable gas storage device in a deflated condition into said first end of said passageway; moving said gas storage device along said passage and into said underground cavity, such that said gas storage device, when in situ extends into said cavity and along said passage, and an inlet of said gas storage device being accessible at said first end of said passage; feeding said gas under pressure into said gas storage device inlet at said first end of said passage, such that said gas storage device expands into said *..* :20 cavity under pressure applied ata position at the first end of said passage way. S... * . **..

: ** According to a third aspect there is provided an underground gas storage *.* facility comprising: a mine working having at least one void cavity; one or a plurality of gas storage devices, each said gas storage device comprising a gas impermeable flexible membrane, which is inflatable into a said void cavity under pressure of said gas contained therein, and which is deflatable when said gas is extracted from said membrane.

P1982.spec According to a fourth aspect there is provided an underground gas storage device comprising: a flexible gas impermeable hollow membrane which is inflatable and deflatable for containing gas.

Other aspects are as recited in the claims herein.

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: Figure 1 illustrates schematically in cut away view from the side, an example of a dis-used mine working adapted for storage of bulk gas using a plurality of gas storage devices according to a first specific embodiment; Figure 2 illustrates schematically in plan view the deployment of Fig. I of a *.S.

. :20 plurality of gas storage devices, inflated with gas underground in a disused mine **..

working, where the mine working has a cavity in the form of an extended layer, : ** extending laterally below ground; Figure 3 illustrates schematically a gas storage balloon device according to a second specific embodiment; Figure 4 illustrates schematically an elongate substantially cylindrical gas storage balloon according to a third specific embodiment; P1982.spec Figure 5 herein illustrates schematically in plan view from above, an underground deployment of a plurality of elongate tubular balloons as shown in Fig. 4, in an underground mine working; Figure 6 illustrates schematically the deployment of Fig. 5, in cut away end view; Figure 7 illustrates schematically an underground mine working having an extensive gas storage facility comprising a plurality of groups of individual gas storage devices according to a fourth specific embodiment; and Figure 8 illustrates schematically an underground deployment in a large underground cavity, accessible by a vertical mine shaft according to a fifth specific embodiment.

Detailed Description

There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific :20 details are set forth in order to provide a thorough understanding. It will be *...

S..... apparent however, to one skilled in the art, that the present invention may be * *. practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to

unnecessarily obscure the description.

Specific embodiments described herein address a problem of bulk underground gas storage, and of utilisation of disused mine workings for bulk gas storage.

Dis-used mines may become hostile environments due to the build up of poisonous and/or explosive gases underground, making it difficult or impossible P1 982.spec for personnel to enter underground cavities without risk of explosion, suffocation or poisoning. For example, mine shafts having a methane gas component in the range 15 to 30% by volume, become potentially explosive.

In various embodiments herein, two modes of deployment are addressed as follows: * Firstly, in environments where a disused mine working is too dangerous for occupancy by human personnel, a method and apparatus for underground gas storage which can be operated from above ground is disclosed; Secondly, in disused mine workings where human personnel can operate underground, specific methods of gas storage and specific embodiments of gas storage installations are disclosed which may be situated at positions remote from an access shaft to an above ground position. * ***

: 20 Referring to Fig. 1 herein, there is illustrated schematically in cut away view **** from one side an underground mine working adapted for underground gas : ** storage according to a first specific embodiment. ****

A mine working comprises an access shaft 100, leading from a surface above ground, to an underground mine working and which may be vertical, inclined or horizontal depending upon the mine working, and one or more underground chambers 101, 102. Depending upon the individual mine working, underground chambers 101, 102 may be in the form of a substantially horizontal or inclined layer, dug out from the surrounding rock, for example where a strata of mineral has been removed. The cavities may comprise large open caverns where mineral has been removed. The underground dimensions of the cavities may P1982 spec extend for distances up to miles in the horizontal directions, and may extend in the vertical direction from one or two meters in height, up to 100 or more meters high. In dis-used or abandoned mines, void spaces in the cavities may have volumes of up to one million cubic meters or more.

In use, an underground gas storage device 103 in the form of a gas impermeable inflateable and deflateable balloon having an elongate supply pipe 104 used for pumping gas into and out of the balloon, is lowered down the mine shaft 100 to the floor of the mine 105. A plurality of gas storage devices may be lowered down the mine shaft with a maximum number of devices being limited by the space of the mine shaft, and the amount of space in the immediate vacinity of the mine shaft within the mine working, and also limited by the size of the balloons 103 of the gas storage devices.

Natural gas or other gas to be stored is pumped down the supply tube 104 to inflate the flexible balloon 103 which inflates along the mine working to occupy the void within the mine working. Similarly, each other gas storage device which has been lowered down the mine shaft may be inflated or deflated simultaneously, so that when all gas storage devices are inflated, the area of the I...

.. :20 mine working in the immediate vacinity of the bottom end of the mine shaft is fully ** occupied by gas storage balloons inflated with natural gas. The gas storage * ** balloons may be inflated under enough pressure so as to fully inflate the gas balloons, but without over pressurising the gas balloons to the extent that punctures or leaks would be encountered. * S. * S * *

The type of gas stored in the underground gas storage devices may comprise natural gas, sometimes called native gas, which comprises a mixture of saturated hydrocarbons, or may comprise other commercially saleable gases such as propane, or methane.

P1 982.spec The primary component of natural gas is methane (CH4), the shortest and lightest hydrocarbon molecule. It may also contain heavier gaseous hydrocarbons such as ethane, (C2H6), propane (C3H8) and Butane (C4H10), as well as other sulphur containing gases, in varying amounts. Organosulfur compounds and hydrogen suiphide (H2S) are common contaminants, which must be removed prior to most uses. Gas with a significant amount of sulphur impurities is termed "sours'. Natural gas is tasteless and odourless. However, before gas is distributed to end-users, it may be odorized by adding thiols, to assist in leak detection. Natural gas is, in itself, harmless to the human body, unless it burns, and is not poison. Natural gas can kill, however if it is present in large concentrations because it reduces the amount of oxygen available in the air, such that the amount of oxygen remaining is insufficient to sustain life.

Natural gas can also kill through an explosion. Natural gas is lighter than air, and so tends to dissipate. But when natural gas is contained, such as within a house or in a tent, perhaps put over a house for fumigation, gas concentrations can reach explosive proportions and trigger very powerful blasts that can level houses, and even neighbourhoods. Methane has a lower explosive limit of 5% in *:.::2o air, and an upper explosive limit of 15%. * * ..

Natural gas may comprise up to 98% methane, whereas mine gas, that is gas naturally occurring in underground mines may contain in the region of 50% to 93% methane. * S. * S S 555 5

Referring to Fig. 2 herein, there is illustrated schematically in plan view an arrangement of a plurality of underground gas storage devices 200 -205 in plan view from above.

In plan view, each storage balloon comprises a substantially triangular segment shape, extending radially from a central vertical mine shaft 206. The P1982.spec size of each underground balloon is restricted by the available space in a lateral or horizontal direction, and by the size of the mine shaft 206. In the installation shown, there are six underground balloons 200 -205 arranged such that each balloon occupies a segment extending over approximately 60 degrees segment of a circle, when viewed from above. Each balloon comprises a substantially triangular shaped body 207, and a central filling point 208 in the form of a supply tube, where the supply tube has length sufficient to extend from an above ground access point of a mine shaft to a point where the mine shaft enters an underground cavity into which the one or a plurality of underground balloons are deployed.

Referring to Fig. 3 herein, there is illustrated schematically in partially inflated view, a gas storage balloon in side view, according to a third specific embodiment. The gas storage balloon comprises a tubular inlet/outlet 300 and a hollow expandable and contractible balloon 301. The expandable and contractible balloon 301 is formed one or more sheets of a gas impermeable membrane, which is flexible enough such that under normal gravitation, without any gas therein, the balloon may collapse. The gas impermeable membrane is made of a material such as a fabric or plastic sheet, which may be compressed in *:::: 20 order to save space. In a compressed mode, the balloon may be slid through a relatively small cross sectional aperture, e.g. through a pipe or tube, so that in * one mode of deployment, the compressed balloon may be fed down a lined tube into a position underground.

: *** 25 The material may be gas impermeable and strong enough, such that **. S pressurised gas may be entered into the balloon material, and the material may be durable enough such that when in contact with a mine roof or sharp abutting items of mineral or other objects in the mine, the balloon does not easily puncture.

Balloon Materials P1982.spec -10-The following materials may be applicable to all specific embodiments disclosed herein. The balloons may be fabricated from a range of flexible gas impermeable membrane materials. Examples of materials include: * Woven nylon fabric having a close weave. The nylon fabric may be coated with a plastics material to one or other side, in order to make the nylon fabric gas impermeable.

* A rubberised fabrics material. A flexible woven fabric material having a rubberised finish on one or either side may be used.

* Polythene sheeting. Large squares of polythene sheet may be heat welded together to provide a flexible gas impermeable membrane.

In various embodiments, the membranes of the balloon gas storage devices, and the inlet and outlet tubes and pipe work may be formed form a material which is flexible enough to be dragged over a mineral surface, be resilient to tearing when in contact with an exposed mineral surface, be resistant s to puncture when in contact with an exposed mineral surface, be resistant to S...

the build up of static electricity when in frictional contact with exposed mineral surface, and thereby reducing the risk of underground explosions, and have a low : enough coefficient of friction that it allows the membrane to slide over an exposed mineral surface when in deflated or inflated modes without snagging.

Installation The following installation methods may be variously used in different embodiments disclosed herein. There are several constraints on the installation of a gas storage balloon into an underground mine working. In most cases, the is underground mine working will be hostile to human presence, and may be filled with a combination of explosives and/or poisonous gases. In addition to the risk P1982.spec -Il -of explosion, poisoning or suffocation, there may be a present risk of rock fall of a mine roof or cavity roof.

In one mode of installation, a deflated balloon may be lowered down a vertical mine shaft from a pit head. Due to the weight of the balloon, the balloon may be provided with one or more sewn in or otherwise formed anchor points, designed to support the entire weight of the balloon, and the balloon may be installed into a vertical mine shaft from the surface. On reaching the bottom of the mine shaft, where the vertical mine shaft meets an underground cavity, the balloon may be slowly inflated, the shaped balloon spreading outwardly laterally to occupy the available void space. In such a deployment, where several balloons are deployed down a substantially vertical mine shaft, similarly as shown in Fig. 2, the limitations on the gas storage capacity of the balloon system may be limited by the size and dimensions of the balloons in deflated condition, which can be lowered down the mine shaft. A relatively wide mine shaft may have dimensions sufficient to fit a plurality of balloons down the same mine shaft in deflated mode, either one at a time, or several together, prior to inflation, and have enough room such that the inlet and outlet tubes can be arranged in the mine shaft without snagging each other or twisting. Each supply tube may be *:::: 20 capable of used for inlet or outlet of gas from its respective balloon, as the ". balloon inflates or deflates. *IS

Referring to Fig. 4 herein, there is illustrated schematically a third embodiment gas storage balloon for underground use. The fourth embodiment : ,** 25 comprises a tubular flexible member 400 closed off at a first end 401 and a second end 402, such that when in an inflated condition as shown, the balloon forms a substantially cylindrical or "sausage" shape. At the first end of the balloon is provided an inlet/outlet tube 403, though which gas may be introduced under pressure, in order to inflate the balloon. Also at the first end of the tube may be provided with a lifting point 404, to which a chain, cable or rope can be attached for supporting the weight of the balloon in deflated mode as it is lowered P1982.spec -12-down a mine shaft. In situ, the balloon may remain attached to a cable, rope or chain, such that the balloon can be removed from the mine shaft in the event that the balloon becomes punctured or non operational by drawing the chain or rope.

The third embodiment shown in figure 4 may be suitable for installation in an elongate tunnel shaped mine working. The outer dimensions of the substantially cylindrical shaped tube may be in the range 2 meters diameter to 15 meters diameter. The length of the tube may be in the range 50 meters, upwards with the maximum length of the tube being limited by the available mine shaft space, down which the tube needs to be passed in order to be installed.

Referring to Figs. 5 and 6herein, there is illustrated schematically a deployment of a plurality of elongate tubular substantially cylindrical gas storage balloons as shown in Fig. 4, in plan view from above, and as shown in Fig. 6, in side view, in a dis-used underground mine working.

The deployment shown in figures 5 and 6 herein requires human access to an underground mine working, in order to deploy a plurality of balloons in the lay out shown. Typically, where a mine working has come to the end of its economic life for mining, the heavy mining machinery such as mineral face roof supports are removed. In some cases, other mine roof supports, such as pit props may also be removed in order to recover these from underground provided it is safe to do so. At this time, during de-commissioning of a mine working, ventilation systems may also still be in place, and therefore access to an underground mine ::::. working may still be available, including vehicular access. Under these circumstances, as parts of a mine working are de-commissioned, an installation of gas storage devices as shown may be made by underground personnel and the available space for gas storage balloons is not limited by the proximity of an P1982.spec access shaft to the same extent as compared to the situation where no underground access is available to personnel.

A plurality of balloon gas storage devices 500 are arranged in parallel side by side. In an extended mine working where a layer of mineral has been removed, the underground cavity may consist of an elongate substantially flat layer having a mine floor under mine roof, and extending laterally in two directions, but with limited vertical height. A roof of the mine working 600 may be supported by a plurality of pit props 501 which prevent localised areas of the roof from collapsing. The pit props may be arranged in rows in a grid, and elongate tubular gas storage balloons may be deployed along rows between the lines of upright pit props as shown in figures 5 and 6.

Each gas balloon comprises a corresponding respective inlet and outlet pipe 502. In the deployment shown in Figs 5 and 6, each of the individual inlet/outlet pipes 502 are shown running in parallel to each other towards an access shaft (not shown in Fig. 5). However in other deployments, the inlet/outlet tubes may be exited from opposite ends of balloons on alternate balloons so as to optimise the use of underground space, and to mitigate the risks of underground rock falls in damaging large number of inlet and outlet pipes at one time.

In the event of a mine roof falling in at a localised position, because the gas ::.:25 storage facility comprises a plurality of independently fillable gas storage balloons, a rock fall in one section of the mine working may damage one or more ::. gas storage balloons locally at that position, but other gas storage balloons within the mine working would be unaffected by the rock fall. Therefore, the damage * caused by a localised rock fall within the mine may be limited to one or two :.: ** 30 individual balloons, leaving the remaining balloons operational and unaffected.

P1 982.spec -14-Referring to Fig. 7 herein, there is illustrated schematically a further example of an underground bulk gas storage deployment comprising a plurality of elongate tubular balloon shaped gas storage devices.

In the installation shown in Fig. 7, a plurality of gas storage devices are deployed in an underground mine working having a large extended mined out layer, for example as may be left after a long wall mining operation, where a seam of mineral has been mined from an underground rock formation leaving a substantially flat elongate void. A plurality of access tunnels may be used to reach the underground cavity from a remote vertical or inclined mine shaft which may be up to one or two miles away from the mine work-face.

A plurality of gas storage devices are arranged into a plurality of groups, where a group is supplied by a common inlet and/or outlet pipe, each group may be provided with a single pipe for both inlet and outlet of gas, or maybe supplied with one or more inlet pipes and one or more outlet pipes, so that gas input into the devices passes through a different pipe or set of pipes compared to gas extracted from the gas storage devices. In order to optimise utilisation of available space underground and in order to minimise the effect of failures of gas storage devices due, for example to rock fall of the mine roof, the inlet and outlet pipes may be arranged optimally, according to geological conditions and risk of rock fall, to pass out of one or more access tunnels in a manner which gives the economic deployment of gas storage devices and inlet and outlet pipes and which may minimise the potential effects of closure of parts of the mine working. :25

In the example shown in Fig. 7, the plurality of gas storage devices are ::::. arranged into groups, where each group shares a common inlet and outlet pipe.

A first group A comprises a first plurality 700 of gas storage devices, commonly connected by a single input and output supply line 701. A second group B comprises a second plurality of gas storage devices 703 commonly supplied by a second inlet and outlet pipe 704.

P1 982.spec At a position remote from the first and second groups, the first and second supply lines 701, 704 may be connected to a junction point 705, which may be positioned in an access tunnel 706 to the underground mine cavity 707, thereby joining the first and second groups, at a common position, remote from the underground cavity.

A third group C comprises a third plurality of gas storage devices 708, and a fourth group D comprises a fourth plurality of gas storage devices 709. In the example shown, the third and fourth groups of gas storage devices are arranged in an interleaving finger pattern, selected from a row of gas storage devices.

Each of the third and fourth groups of gas storage device has its own single inlet and outlet supply pipe 710, 711 respectively, and exits the underground cavity via a second access shaft 712.

A fifth group E comprises a fifth plurality of gas storage devices 730, all commonly connected by a common inletloutlet supply pipe 714 which exits the underground cavity via the first access shaft 706.

A sixth group of gas storage devices F comprises a sixth plurality of gas storage devices 715, the fifth plurality of gas storage devices commonly connected by a common input/output pipe 716 which exits the underground cavity via the second access shaft 712. In the deployment shown in Fig. 7, each gas storage balloon may have dimensions of the order radius up to 3 metros and length 50 to 300 meters, giving a gas storage volume when fully inflated of the order of 1400 m3 to 8400 m3. Of course, smaller dimensioned or larger ::. dimensioned gas balloons may be constructed in other specific embodiments.

* In the specific embodiments shown around 38 balloons may give a total :.: 30 combined gas storage capacity of around 0.2 million m3.

P1 982.spec -16 -Referring to Fig. 8 herein, there is illustrated schematically in cut away side view, an underground cavity 800 accessible via a vertical shaft 801, and occupied by a single underground gas storage balloon 802 which is manufactured to a shape which fits closely the shape of the underground cavity 800.

The underground gas storage balloon is shown in a deployed mode, fully inflated.

Installation of the balloon underground is by lowering the balloon in deflated mode, down the shaft 801, using lifting gear 803. The balloon comprises a moulded in or formed in attachment point which is securely fixed into the outer member of the balloon 802, and capable of supporting the whole weight of the balloon fabric, when in deflated mode. When lowered down the mine shaft, the balloon may be compressed by a series of rings or bindings, which are strong enough to maintain the balloon fabric in deflated mode, but as soon as the balloon fabric is placed under pressure from insertion of gas, the bindings may be designed to break under tension once a pre-determined amount of tension has been reached, due to inflation of the balloon, thereby allowing the balloon to be compacted to a minimum size for insertion down the shaft into the cavity. Once in the cavity, and once inflation under pressure begins, the balloon may be allowed to expand, breaking the bindings which experience a tension above their pre-determined break tension so that the balloon can then expand into the void space. * * .

::.:25 In the example shown, since the balloon is shaped to fit the void, in this ::::. case, the balloon is asymmetrically shaped. Therefore the balloon needs to be lowered down in an attitude whereby expansion of a longer portion of the balloon * 804 proceeds in a direction of maximum space of the cavity, whereas expansion :.: 30 of a relatively shorter part of the balloon 805 expands in a direction of the relatively smaller end of the underground void. The balloon may be fitted with a P1982.spec plurality of suspension points, allowing the balloon to be rotated when hung vertically down the mine shaft 801 so that the balloon can be placed in a position prior to inflation, whereby the longer end of the balloon 804 is aligned with the larger area of void, so that it can expand into the main larger area of the cavity.

Once lowered down the shaft by lifting gear 803, the balloon may be inflated by an above ground pump and valve mechanism 806, which fills the balloon with pressurised gas from a gas supply 807. *S.. * * S ** * S... * S S... * S. * . S * .. * S * S.. *

P1 982.spec

Claims

Claims: 1. A method of storing natural gas underground comprising: installing one or a plurality of inflateable and deflateable gas storage devices in an underground cavity, each said gas storage device comprising a flexible gas impermeable membrane; and inflating said one or plurality of gas storage devices with natural gas.
2. The method as claimed in claim 1, wherein said gas is pressurised at a position outside of and away from said cavity.
3. The method as claimed in claim 1, wherein said gas is pressurised is at a position above ground.
4. The method as claimed in claim 1, wherein said gas comprises native hydrocarbons.
5. The method as claimed in claim 1, wherein said gas comprises natural gas.
6. The method as claimed in claim 1, wherein said gas comprises town gas. *25 * ***
7. The method as claimed in claim 1, wherein said gas comprises : *. north sea gas.

:
8. The method as claimed in claim 1, wherein said gas comprises * 30 methane.

P1 982.spec
9. The method as claimed in claim 1, wherein said underground cavity comprises a mine working.
10. The method as claimed in claim 1, wherein said underground cavity comprises a coal mine.
11. A method of bulk gas storage for storing natural gas in a underground cavity, said underground cavity being connected with a terminal position via a passage, said terminal being present as a first end of said passage and said cavity being present at a second end of said passage, said method comprising: inserting an inflatable and deflatable gas storage device in a deflated condition into said first end of said passageway: moving said gas storage device along said passage and into said underground cavity, such that said gas storage device, when in situ extends into said cavity and along said passage, and an inlet of said gas storage device being accessible at said first end of said passage; feeing said gas under pressure into said gas storage device inlet at said first end of said passage, such that said gas storage device expands into said cavity under pressure applied at a position at the first end of said passage way. IS:25
12. The method as claimed in claim 11, wherein said passage : .. comprises a substantially vertical shaft. S...
13. The method as claimed in claim 11, wherein said passage :.:. 30 comprises a bore hole.

P1982.spec -20 -
14. An underground gas storage facility comprising: a mine working having at least one void cavity; one or a plurality of gas storage devices, each said gas storage device comprising a gas impermeable flexible membrane, which is inflatable into a said void cavity under pressure of said gas contained therein, and which is deflatable when said gas is extracted from said membrane.
15. The underground gas storage facility as claimed in claimi 4, further comprising: one or a plurality of supply pipe lines for supplying gas to said one or plurality of gas storage devices, from a position above ground.
16. The gas storage installation as claimed in claim 14 or 15, further comprising: an above ground pumping station for pumping pressurised gas into said one or plurality of gas storage devices.
17. An underground gas storage device comprising: a flexible gas impermeable hollow membrane which is inflatable and deflatable for containing gas. * .* * * * S. S.
18. The underground gas storage device as claimed in claim 17, further comprising: * .* * S * * 30 P1982 spec -21 -an elongate tube for introduction of said natural gas into and out of said membrane, said tube having first and second ends, said second end being attached to said hollow gas impermeable membrane said tube.
19. The gas storage device as claimed in claim 17 or 18, further comprising: a lifting point capable of supporting the whole weight of said gas membrane, for raising or lowering said gas membrane down an upright shaft ma deflated mode.
20. The gas storage device as claimed in any one of claims 17 to 19, for of a static resistant fabric.
21. The gas storage device as claimed in any one of claims 17 to 19, formed of a fabric which is resistant to puncture when in contact with an exposed mineral surface.
22. The gas storage device as claimed in any one of claims 17 to 21, wherein said membrane is formed of a material which has a low enough coefficient of friction to allow said membrane to slide over an exposed mineral surface without significant snagging. :25 S... * S *5SS * .. * . * *.*. * *. * * * **. SP1 982.spec Amendment to the claims have been filed as follows Claims: 1. A method of storing natural gas in an underground cavity, said underground cavity being connected with a terminal position via a passage, said terminal being present at a first end of said passage and said cavity being present at a second end of said passage, said method comprising: inserting an inflatable and deflatable gas storage device in a deflated condition into said first end of said passage; moving said gas storage device along said passage and into said underground cavity, such that said gas storage device, when in situ, extends into said cavity and along said passage, and an inlet of said gas storage device being accessible at said first end of said passage; feeding said gas under pressure into said gas storage device inlet at said first end of said passage, such that said gas storage device expands into said cavity under pressure applied at a position at the first end of said passage way, wherein installation of said gas storage device is performed from a position above ground.2. The method as claimed in claim 1, wherein said gas storage device comprises; S... * *SS * S..one or a plurality of sewn in, moulded in or otherwise formed anchor point capable of supporting the whole weight of said gas membrane for raising or towering said gas membrane down said passage in deflated mode.3. The method as claimed in claim I or 2, wherein said gas storage *: 30 device comprises: one or a plurality of compression rings or bindings in order to maintain the shape of the said storage device in the compressed mode; said rings or bindings are designed to break under tension, once predetermined pressure is exerted on said rings or binding, due to filling of said storage device with said natural gas 4. The method as claimed in any one of the preceding claims, wherein said passage comprises a substantially vertical shaft.5. The method as claimed in any one of claims I to 3, wherein said passage comprises a bore hole.6. The method as claimed in any one of the preceding claims, wherein said gas storage device is formed of a fabric which is resistant to puncture when in contact with an exposed mineral surface.7. The method as claimed in any one of the preceding claims wherein said gas storage device is formed of a material which has a low enough coefficient of friction to allow said membrane to slide over an exposed mineral surface without significant snagging.8. The method as claimed in any one of the preceding claims, wherein S...said gas comprises native hydrocarbons. *... * S*s.. 25 9. The method as claimed in any one of the preceding claims, wherein said gas comprises methane.10. The method as described in any one of the preceding claims, 4. 30 wherein said gas impermeable membrane comprises a material selected from the set a woven nylon fabric having a close weave; a woven nylon fabric having a close weave and coated with a plastics material; a rubbensed fabrics material; polythene sheeting. * ** ** * **** * * * *** ** * S.. * .* ** S S... *5*