AU2014201774B1

AU2014201774B1 - Fluid drainage apparatus

Info

Publication number: AU2014201774B1
Application number: AU2014201774A
Authority: AU
Inventors: William Lee Gane
Original assignee: Hokins Belinda Candace
Current assignee: Hokins Belinda Candace
Priority date: 2013-12-20
Filing date: 2014-03-25
Publication date: 2014-11-27
Anticipated expiration: 2034-03-25
Also published as: AU2022209347A1; AU2022209342A1

Abstract

A fluid drainage assembly comprising a fluid drainage member adapted for at least partial insertion into a borehole, and an inflatable borehole plug assembly comprising an inflatable bag at least partially surrounding at least a portion of the fluid drainage member and inflation means to inflate the inflatable bag, wherein, upon inflation, the inflatable bag inflates to retain the fluid drainage assembly within the borehole.

Description

FLUID DRAINAGE ASSEMBLY TECHNICAL FIELD [0001] The present invention relates to a fluid drainage assembly. In particular, the present invention relates to a fluid drainage assembly for extracting fluid from a borehole. BACKGROUND ART [0002] Boreholes are drilled so that explosive charges may be placed in the borehole at a particular position. Sometimes, the borehole is entirely filled with explosive, but other times an explosive charge must be placed somewhere along the borehole length. For this type of use, a plug is lowered down the borehole to the desired area to form a support platform for the explosive. In a typical arrangement, an explosive charge (or base charge) is located at the bottom of a borehole, while a mid-level explosive charge is supported by the plug. [0003] There are some environments in which standard borehole plugs are not suitable. For instance, borehole plugs used in coal mining require the use of non-flammable and/or non combustible components (including the inflating substance). In addition, borehole plugs used in coal mining must effectively seal a borehole in order to prevent toxic and/or flammable gases (such as methane) from entering workspaces. [0004] In addition, there are situations in which it may be desirable to extract fluid (including gases such as methane) from a borehole. However, due to the flammable and explosive nature of methane, extraction of this gas from boreholes may be dangerous. [0005] In light of the foregoing, there would be an advantage if it were possible to provide a fluid drainage assembly that could be used to rapidly create a non-flammable and/or non combustible seal against the flow of flammable and/or toxic gases such as methane, as well as providing for the efficient extraction of flammable and/or toxic gases from a borehole. [0006] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country. SUMMARY OF INVENTION [0007] The present invention is directed to a fluid drainage assembly which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice. [0008] In one aspect, the invention resides broadly in a fluid drainage assembly comprising a fluid drainage member adapted for at least partial insertion into a borehole, and an inflatable borehole plug assembly comprising an inflatable bag at least partially surrounding at least a portion of the fluid drainage member and inflation means to inflate the inflatable bag, wherein, upon inflation, the inflatable bag inflates to retain the fluid drainage assembly within the borehole, and wherein a seal is created between a lower region of the fluid drainage member and the borehole and/or an upper region of the fluid drainage member and the borehole using a grout or a foam. [0009] The borehole may be drilled at any suitable angle into the earth. For instance, the borehole may be drilled substantially vertically, substantially horizontally, or at any suitable angle between vertical and horizontal. [0010] The fluid drainage member may be of any suitable size, shape or configuration. Preferably, however, the fluid drainage member comprises an elongate member adapted to be at least partially inserted into a borehole. Preferably, the fluid drainage member includes one or more passageways therethrough that allow fluid (such as gas) from within the borehole to pass along the one or more passageways in the fluid drainage member and exit the borehole. Fluid exiting the borehole through the fluid drainage member may be collected for use or conversion to a useful or saleable product, or may simply be vented to the atmosphere. [0011] Any suitable fluid may be drained from the borehole using the assembly of the present invention. However, in a preferred embodiment of the invention, the fluid comprises a gas or mixture of gases. In a particular embodiment of the invention, the gas comprises methane, or a mixture of gases in which methane is present. [0012] The one or more passageways may be of any suitable configuration. For instance, the one or more passageways may be tortuous or substantially straight. The passageways may be substantially clear of obstructions or may include one or more obstructions, such as one or more filters, baffles, fluid movement devices (such as pumps, fans and so on) or the like, or any suitable combination thereof. [0013] The flow of fluid through the one or more passageways may be enhanced by fluid movement devices (such as pumps, fans and so on). As previously stated, these fluid movement devices may be located within the one or more passageways. However, it is envisaged that the fluid movement devices may also be located externally to the one or more passageways and adapted to be located in communication therewith. In this manner, the fluid movement devices may either blow or suck the fluid through the one or more passageways.

[0014] The one or more passageways may be of constant width, or the width of the passageways may vary along their length. For instance, the passageways may be provided with one or more narrowed portions adapted to increase the velocity of the fluid passing through the passageway. [0015] In a preferred embodiment of the invention, the fluid drainage member comprises one or more lengths of pipe adapted to be at least partially inserted into the borehole. The length of the pipe is not critical to the invention, nor is the diameter of the pipe, although it will be understood that the outside diameter of the pipe must be less than the diameter of the borehole. Further, the pipe may be of any suitable shape in cross-section. The pipe may be fabricated from any suitable material, or combination of materials. For instance, the pipe may be fabricated from metal (such as steel, aluminium, copper or the like) or plastic (such as PVC, polyurethane or the like). [0016] The pipe may be of any suitable dimensions. For instance, the pipe may be between about 10mm and 150mm in diameter, and between about 350mm and about 4m in length. [0017] In embodiments of the invention in which the fluid drainage member comprises a length of pipe, it is envisaged that a single passageway will be present. Preferably, the single passageway may extend substantially parallel to the longitudinal axis of the fluid drainage member. In a preferred embodiment of the invention, the passageway may comprise an internal bore extending along the length of the pipe. Preferably, the diameter of the passageway is defined by the internal diameter of the pipe. [0018] Preferably, the pipe is provided with at least one at least partially open end. In this embodiment of the invention, at least the lower end of the pipe (i.e. the end of the pipe that is first inserted into the borehole) is at least partially open so that fluid may enter the fluid drainage member through the open end. [0019] In some embodiments, the upper end of the pipe (i.e. the end of the pipe that is closest to the mouth of the borehole) may also be at least partially open so that fluid entering the lower end of the pipe may be vented through the upper end of the pipe. Alternatively, the upper end of the pipe may be connected to one or more fittings adapted to extract and/or divert the fluid leaving the borehole, for instance into a storage vessel or the like. The one or more fittings may be of any suitable form, such as one or more additional pipes, hoses or the like. Extraction means (such as one or more fans or the like) may also be connected to, or associated with, the upper end of the pipe. These extraction means may assist in sucking or siphoning fluid out of the pipe. [0020] In embodiments of the invention in which the upper end of the pipe is connected to other fittings, the upper end of the pipe may be provided may be provided with attachment means, such as a screw thread (internal or external) or the like. Alternatively, attachment means may be fitted to the end of the pipe, allowing the attachment means to be connected to other fittings. For instance, a cap having an external screw thread may be provided at the end of the pipe, and other fittings may be connected to the cap. [0021] In some embodiments of the invention, the upper end of the pipe may be provided with one or more flow control members adapted to prevent fluid from exiting the pipe and/or to control the rate of flow of fluid through the pipe. Any suitable flow control members may be provided, such as one or more valves. Any suitable valves may be provided, such as ball valves, pinch valves, butterfly valves and the like, or any suitable combination thereof. Preferably, however, the valves are operable between an open condition in which the flow of fluid through the valve is unrestricted and a closed condition in which the flow of fluid through the valve is substantially precluded. Preferably, the valve may comprise any suitable number of partially open conditions between the open condition and the closed condition. [0022] In some embodiments of the invention, the flow control members may be adapted to alter the direction of flow of the fluid from the borehole. For instance, the flow control members may be adapted to direct the flow of fluid in two or more directions. In a specific embodiment of the invention, the flow control members may be associated with a T-piece such that the flow of fluid may be directed in different directions depending on operational requirements. The T-piece may be manufactured from any suitable material, such as metal or plastic. In this embodiment, the flow control members may be adapted to direct a flow of fluid through one of the two outlets of the T-piece. Alternatively, the flow control members may be adapted to direct a flow of fluid through one of the two outlets of the T-piece and to preclude fluid from exiting the borehole. One or both of the outlets of the T-piece may be provided with a screw-threaded portion to allow for connection to another fitting. Alternatively, one or both outlets may be provided with any other suitable portion to allow the outlets to be attached to a fitting, hose or the like. [0023] In this embodiment, the flow control members may effectively provide an isolation point. To achieve this, a first valve may be associated with the portion of the T-piece through which fluid exits the borehole, while a second valve may be associated with at least one of the outlets of the T-piece. Alternatively, the T-piece may be provided with a three-way valve.

[0024] In one embodiment of the invention, a first outlet of the T-piece is oriented so as to direct a flow of fluid exiting the borehole in a substantially upward direction. It will be understood that the term "upward direction" in this context is not intended to be limited to the meaning "vertical" but is rather intended to encompass within its scope any direction in which the fluid would flow against the effect of gravity. [0025] In this embodiment, it is envisaged that a second outlet of the T-piece is oriented so as to direct a flow of fluid in a substantially downward direction. It will be understood that the term "downward direction" in this context is not intended to be limited to the meaning "vertical" but is rather intended to encompass within its scope any direction in which the fluid would flow under the effect of gravity. [0026] It is envisaged that, when the flow control members are actuated to prevent the flow of fluid out of the borehole, any water or other liquids in the lines attached to the first and/or second outlets may be drained. This prevents build-up in and blockages of the fluid lines. The second outlet may also be used as a sampling point at which a sample of the fluid may be collected. [0027] In some embodiments of the invention, one or more gauges may be provided on the fluid lines so as to measure one or more parameters. Preferably, the one or more gauges include at least one pressure gauge to monitor the pressure in the fluid lines (and particularly the line through which fluid drained from the borehole is extracted to the surface or to storage). In this way, the pressure in the line may be monitored and any blockages cleared before the high pressure in the line caused by the blockage leads to failure of the line or a potentially hazardous outburst of fluid (such as methane gas). [0028] In some embodiments of the invention, the T-piece may be connected to earth so as to prevent the build-up of static. Any suitable technique for earthing the T-piece can be used, and it will be understood that the actual technique used to earth the T-piece is not critical to the working of the invention. [0029] The inflatable bag may be fabricated from any suitable material. For instance, the inflatable bag may comprise multi-layer plastic bags which are gas tight. These bags may be formed from suitable material such as plastics, such as, but not limited to, polyethylene (including high density polythethylene (HDPE) and low density polyethylene (LDPE)), polyvinyl chloride (PVC), polyurethane, polypropylene, polystyrene, polycarbonate, silicone, polyester or the like or any suitable combination thereof. The size and volume of the bag can also vary depending on the borehole size and the like. [0030] In a preferred embodiment of the invention, at least a portion of a surface (and preferably an outer surface) of the inflatable bag includes a non-combustible or fire retardant material. In some embodiments of the invention, at least a portion of the outer surface of the inflatable bag may be coated with a non-combustible or fire retardant material. For instance, a non-combustible or fire retardant material may be sprayed, painted, powder coated or otherwise applied to a surface of the inflatable bag. Alternatively, a non-combustible or fire retardant material may be impregnated (using any suitable technique) into the material of the surface of the inflatable bag. Any suitable non-combustible, non-hazardous or fire retardant material may be used, such as, but not limited to, fire-fighting foams or liquids (such as, but not limited to potassium acetate, carbonate, or citrate, fluoroproteins, fluoro tensides and the like, or any suitable combination thereof), dry chemical powders (such as, but not limited to, monoammonium phosphate, sodium bicarbonate, potassium bicarbonate, potassium chloride and the like, or any suitable combination thereof), organobromides, organobromines or the like, or a combination thereof. [0031] In an alternative embodiment, the inflatable bag may be at least partially fabricated from a non-combustible or fire retardant fabric. Any suitable fabric may be used, such as, but not limited to, certain non-combustible polyesters. [0032] In a preferred embodiment of the invention, at least a portion of a surface of the inflatable bag further includes an antistatic material. In some embodiments of the invention, at least a portion of the outer surface of the inflatable bag may be coated with antistatic material. For instance, an antistatic material may be sprayed, painted, powder coated or otherwise applied to a surface of the inflatable bag. Alternatively, an antistatic material may be impregnated (using any suitable technique) into the material of the surface of the bag. Any suitable antistatic material may be used, such as, but not limited to, aliphatic amines (especially long-chained aliphatic amines, and optionally ethoxylated aliphatic amines) and/or amides, quaternary ammonium salts (e.g., behentrimonium chloride or cocamidopropyl betaine), esters of phosphoric acid, polyethylene glycol esters, polyols, or compounds such as indium tin oxide, or a combination thereof. [0033] In an alternative embodiment, the bag may be at least partially fabricated from an antistatic fabric. Any suitable fabric may be used. For instance, the gas bag may be provided with one or more electrically conductive threads (such as metallic threads, including threads of silver, copper, gold, aluminium, zinc, nickel, brass, bronze, iron or platinum or the like, or any suitable combination thereof) on the surface of the gas bag, or formed with the gas bag. In order to function as an antistatic device, the gas bag may also be connected to earth using any suitable technique. Thus, in this embodiment of the invention, the gas bag may function in a similar manner to a Faraday cage. [0034] It is envisaged that, in a preferred embodiment of the invention, the assembly may comply with one or more applicable national Standards. In particular, it is envisaged that the assembly may comply with applicable national FRAS (Fire Retardant Anti Static) Standards. [0035] In some embodiments of the invention, the upper and/or lower ends of the inflatable bag may be provided with sealing members adapted to enhance the seal between the inflatable bag and the inner surface of the borehole. Any suitable sealing member may be provided, such as one of more gaskets or the like. Alternatively, the upper and/or lower ends of the inflatable bag may be provided with sealing members in the form of a cover portion that is located over the upper and/or lower ends of the inflatable bag. Upon inflation of the inflatable bag, the cover abuts the inner surface of the borehole, thereby creating a seal between the surface of the borehole and the inflatable bag. The cover portions may be fabricated from any suitable material, although in some embodiments of the invention the cover portions may be fabricated from a material that is capable of forming an effective seal against the inner surface of the borehole. For instance, the cover portion may be fabricated from an at least partially deformable material such as rubber or plastic such that the cover portion deforms to substantially conform to the shape of the borehole surface, thereby creating an effective seal. [0036] The inflatable bag may at least partially surround a portion of the circumference of the fluid drainage member. Alternatively, the inflatable bag may at least partially surround at least a portion of the length of the fluid drainage member. In a preferred embodiment of the invention, the inflatable bag surrounds the entire circumference of the fluid drainage member. More preferably, the inflatable bag surrounds the entire circumference of the fluid drainage member and a portion of the length of the fluid drainage member. [0037] The inflatable bag may surround any suitable portion of the length of the fluid drainage member. Preferably, however the inflatable bag surrounds a central portion of the fluid drainage member. In this embodiment of the invention, it is envisaged that a portion of the fluid drainage member at or adjacent opposed ends of the fluid drainage member will not be surrounded by the inflatable bag. [0038] The inflatable bag may be of any suitable shape. For instance, the inflatable bag may 0 be substantially annular or toroidal. In this embodiment of the invention, the fluid drainage member may pass through the central passageway of the annular or toroidal inflatable bag. Alternatively, the inflatable bag may be substantially cylindrical, with the fluid drainage member housed within the inflatable bag along at least a portion of the length of the fluid drainage member. In this embodiment of the invention, it is envisaged that the inflatable bag may be connected to the fluid drainage member at the upper and lower ends thereof The inflatable bag may be connected to the fluid drainage member using any suitable technique, however it is envisaged that the inflatable bag will be connected to the fluid drainage member at the upper and lower ends thereof in a leak-proof connection. This ensures that no unwanted deflation of the inflatable bag is experienced. [0039] In this embodiment of the invention, it is envisaged that the fluid drainage member may be provided with one or more locating members adapted to locate and/or retain the inflatable bag in position relative to the fluid drainage member. Any suitable locating members may be present. For instance, in some embodiments of the invention, the locating members may comprise attachment portions to which the inflatable bag is attached. Alternatively, the locating members may comprise stop members (such as one or more flanges extending outwardly from the outer surface of the fluid drainage member) that define the limit of movement of the inflatable bag relative to the fluid drainage member. [0040] In a specific embodiment of the invention in which the locating members comprise stop members, it is envisaged that a stop member may be located on the fluid drainage member adjacent each end of the inflatable bag. In this way, the inflatable bag may be retained between the stop members. If desired, the stop members may be located so as to abut opposed ends of the inflatable bag such that movement of the bag relative to the fluid drainage member is substantially precluded. [0041] In an alternative embodiment of the invention, the inflatable bag may only surround a portion of the circumference and a portion of the length of the fluid drainage member. In this embodiment of the invention, it is envisaged that the fluid drainage member may be located against the inner surface of the borehole, and the inflatable bag may, once inflated, expand to surround a portion of the circumference of the fluid drainage member and retain the fluid drainage member in place against the inner surface of the borehole. Thus, in this embodiment of the invention, the fluid drainage member is located between the inner surface of the borehole and the outer surface of the inflatable bag. [0042] In embodiments of the invention in which the fluid drainage member is located externally to the inflatable bag, the inflatable bag may be of any suitable shape. For instance, the inflatable bag may be substantially cylindrical. [0043] It is envisaged that, once inflated, the inflatable bag will expand to the point that the outer surface of the inflatable bag abuts the inner surface of the borehole. Preferably, the degree of expansion of the inflatable bag is such that the assembly is retained in the desired position within the borehole by the abutment between the inflatable bag and the inner surface of the borehole. Thus, it is envisaged that the pressure within the inflatable bag must, once inflated, be sufficient to prevent movement of the assembly relative to the borehole. In this embodiment of the invention, it is envisaged that the surface of the inflatable bag may be at least partially fabricated from an abrasion resistant material in order to prevent damage to the inflatable bag from the inner surface of the borehole. [0044] The inflation means may be of any suitable form. However, in a preferred embodiment of the invention, the inflation means comprises one or more pressurised containers. Preferably, the pressurised container will contain an inflating substance, such that actuation of the pressurised can will result in the inflating substance being dispensed from the pressurised container. In a particularly preferred embodiment of the invention, the pressurised container comprises an aerosol can, although it will be understood that any suitable pressurised container could be provided. [0045] The inflating substance may be dispensed from the pressurised container in any suitable manner. Preferably, however, the inflating substance is dispensed through one or more valves, once the one or more valves have been actuated. [0046] The one or more valves may typically be such that once opened, the valve stays open which means that the contents of the container will be totally released without interruption until the pressure in the container and the pressure in the bag equalises. [0047] The pressurised container may be fabricated from any suitable material, such as plastic, steel, tin plate or aluminium. It is envisaged that the use of aluminium cans may allow the container to be rated to a higher pressure than cans fabricated from other materials. In a preferred embodiment of the invention, the container has a pressure rating of greater than 12 bar. In a more preferred embodiment of the invention, the container has a pressure rating of between about 12 bar and 25 bar. In a most preferred embodiment of the invention, the container has a pressure rating of about 20 bar. However, in some situations (such as when the inflatable borehole plug is used in underground mines, and more particularly underground coal mines) I 1J safety regulations and/or concerns may dictate the use of pressurised containers fabricated from other materials. In these situations, pressurised containers made from plastic, steel or tin plate may be preferred. [0048] The inflating substance can vary to suit. The inflating substance is typically in the form of a volatile liquid which will expand and volatise once in the inflatable bag. Alternatively, the pressurised can may contain compressed gas. [0049] Preferably, the inflating substance is substantially non-flammable and/or substantially non-toxic during normal use. Any suitable substance may be used, although in a preferred embodiment of the invention, the inflating substance may include 1,1,1,2 tetrafluoroethane (also known as R-134a). [0050] In some embodiments of the invention, the inflating means may be provided loose within the inflatable bag. More preferably, however, the inflating means may be secured within the inflatable bag. Not only does this prevent accidental actuation of the inflating means, but it also makes it easier for a user to locate the inflating means within the inflatable bag (for instance, to actuate the inflating means). By securing each inflating means in the same or similar location within the inflatable bag, a user may quickly and easily locate the inflating means when it is desired to actuate the inflating means. [0051] The inflating means may be secured within the inflatable bag using any suitable technique. For instance, the inflating means may be secured to a surface of the fluid drainage member, or to an inner surface of the inflatable bag. The inflating means may be secured using one or more fasteners, adhesives or the like, or a combination thereof [0052] Alternatively, the fluid drainage member may be provided with one or more recesses in which the inflating means may be located. Any suitable recess may be provided, however, it is envisaged that the fluid drainage member may be provided with a region of reduced diameter that results in the formation of a recess in the outer surface of the fluid drainage member in which the inflating means may be located. The region of reduced diameter may be formed using any suitable technique. For instance, the fluid drainage member may comprise a pipe of constant diameter that is subjected to a deformation process so as to produce the region of reduced diameter. Alternatively, the fluid drainage member may be formed with the region of reduced diameter. The region of reduced diameter may extend along any suitable portion of the length of the fluid drainage member. The inflating means may be secured fixedly within the recess, or may be free to move within the confines of the recess.

1 1 [0053] In embodiments of the invention in which the inflatable bag surrounds a central portion of the length of the fluid drainage member, it may be desired to create a seal between the inner surface of the borehole and the upper and lower regions of the fluid drainage member. Any suitable seal may be formed, although in a preferred embodiment of the invention, the seal may be a gas and/or water impermeable seal. [0054] In a preferred embodiment of the invention, a seal may be created between a lower region of the fluid drainage member and the inner surface of the borehole and/or an upper region of the fluid drainage member and the inner surface of the borehole using a grout or a foam, and in particular an expandable form. Preferably, the grout or expandable foam hardens when set so as to form a seal between the fluid drainage member and the inner surface of the borehole. Any suitable foam may be used, although in a preferred embodiment of the invention, the foam may be a non-flammable or fire retardant foam. [0055] In order to define the area in the upper and/or lower regions of the fluid drainage member in which the seal is to be formed, one or more boundary members may be provided on the outer surface of the fluid drainage member. The one or more boundary members may be of any suitable size, shape or configuration, although in a preferred embodiment of the invention, the one or more boundary members may extend outwardly from the outer surface of the fluid drainage member. Any suitable number of boundary members may be provided, although in a preferred embodiment of the invention, the fluid drainage member may be provided with an upper boundary member and a lower boundary member for whichever of the upper and/or lower regions of the fluid drainage member a seal is to be formed. [0056] In a preferred embodiment of the invention, the one or more boundary members may comprise one or more flanges extending from the surface of the fluid drainage member. [0057] In one embodiment of the invention, the upper boundary member of the upper region of the fluid drainage member may be located approximately level with ground level (i.e. approximately level with the mouth of the borehole). [0058] It is envisaged that, as the expanding foam is inserted into the region in which the seal is to be formed, the upper and lower boundary members contain the foam within the desired area. Not only does this ensure that foam does not penetrate into regions of the borehole where it is not required or desired, but it also assists in predicting the volume of expanding foam that is required to be inserted into the region in which the seal is to be formed in order to create the seal. [0059] In embodiments of the invention in which grout is used to form a seal against the I / inner surface of the borehole, the assembly may be provided with an additional container into which grout may flow. It is envisaged that this additional container may comprise a flexible container (such as a bag) into which the grout flows. As the grout flow into the container, it is envisaged that the container will expand until it abuts the inner surface of the borehole. Preferably, the container is fabricated from a porous material or membrane so that at least a portion of the grout may pass through the container and adhere to the inner surface of the borehole. In this way, an effective seal between the borehole and the grout may be achieved. [0060] The container may be fabricated from any suitable porous material, such as woven fabrics (e.g. cotton, hessian etc.) or plastics (e.g. nylon, polyester etc.). Alternatively, the container may be fabricated from a polymeric membrane material. [0061] When the assembly is inserted into the borehole and the inflatable bag has been inflated so as to abut the inner surface of the borehole, it may no longer be possible to access the lower end of the fluid drainage member to form the seal. Thus, in a preferred embodiment of the invention, the assembly may be provided with one or more transfer conduits through which foam or grout may pass in order to reach the region of the fluid drainage member in which the seal is to be formed. The transfer conduits may be of any suitable form, although in a preferred embodiment of the invention, the transfer conduits comprise one or more pipes that extend parallel to the fluid drainage member. The transfer conduits may be located at any suitable location, such as on the outer surface of the fluid drainage member, on the outer surface of the inflatable bag and so on. Preferably, the transfer conduits terminate between the upper and lower boundary members in the lower region of the fluid drainage member. It is envisaged that expandable foam will be passed through the transfer conduits and into the region between the boundary members in which the seal is to be formed. [0062] A further transfer conduit may be provided for the region in which the seal is to be formed at or adjacent the upper end of the fluid drainage member. Alternatively, the region in which the seal is to be formed at or adjacent the upper end of the fluid drainage member may be accessible from outside the borehole and a further transfer conduit may not be required. [0063] In some embodiments of the invention, the assembly may comprise a temporary inflatable bag used to seal the borehole to prevent the escape of fluid from the borehole. The temporary inflatable bag may be provided so as to form a temporary seal in the borehole prior to inflation of the inflatable bag. Thus, the temporary inflatable bag may be inserted into the borehole and actuated prior to the insertion of the fluid drainage member into the borehole. Once the fluid drainage member is inserted into the borehole, and the inflatable bag is actuated, the temporary inflatable bag may be deflated or otherwise removed. [0064] In another embodiment of the invention, the temporary inflatable bag may be used prior to the insertion of the assembly into a borehole. For instance, if a road is driven through a block of coal in an underground mine, the road may intersect boreholes drilled through the coal. Thus, gases (such as methane) are able to enter the roadway through the intersected borehole. In these situations, a temporary inflatable bag may be inserted into the borehole and inflated to prevent gas from exiting the borehole. Once a fluid drainage assembly is ready to be inserted into the borehole and inflated, the temporary inflatable bag may be deflated and removed to allow for the insertion of the fluid drainage assembly. [0065] The temporary inflatable bag may be connected to the assembly or may be used separately to the assembly. [0066] In some embodiments of the invention, the assembly may comprise a pair of inflatable bags. In this embodiment of the invention an upper inflatable bag may be located at or adjacent the mouth of the borehole, while a lower inflatable bag may be located at a point within the borehole below the upper inflatable bag. Preferably, the upper and lower inflatable bags are spaced apart from one another such that a void is formed in the borehole between the inflatable bags. [0067] In this embodiment of the invention, a fluid drainage member may be positioned within the borehole such that the inlet of the fluid drainage member (i.e. the lower end of the fluid drainage member) is located further into the borehole than the lower end of the lower inflatable bag, while the upper end of the fluid drainage member extends to a point substantially level with or above the upper end of the upper inflatable bag. In order to seal the borehole against the unwanted flow of fluid (such as gases like methane) out of the borehole, a sealant may be transferred into the borehole to form a seal between the lower end of the upper inflatable bag and the upper end of the lower inflatable bag. Thus, in a preferred embodiment of the invention, the assembly may be provided with one or more transfer conduits through which sealant (such as grout or foam, including expandable foam) may pass in order to reach the void between the inflatable bags in which the seal is to be formed. The transfer conduits may be of any suitable form, although in a preferred embodiment of the invention, the transfer conduits comprise one or more pipes that extend parallel to the fluid drainage member. The transfer conduits may be associated with the fluid drainage member, connected to the outer surface of the inflatable bag, or may located against the inner surface of the borehole and retained in position by the inflated upper inflatable bag. Preferably, the transfer conduits terminate between the 14 upper and lower inflatable bags. It is envisaged that sealant may be passed through the transfer conduits and into the void between the inflatable bags in which the seal is to be formed. The lower end of the transfer conduits may be provided with a nozzle, spray head or similar distribution device to assist in the even distribution of the sealant within the void. [0068] In some embodiments of the invention, the assembly may further comprise an exit conduit for excess sealant (foam or grout). The exit conduit may be of any suitable form (such as a pipe, hose or the like) and may be positioned so as to extend between the void formed between the upper and lower inflatable bags and at least the mouth of the borehole (and may extend outwardly from the borehole if desired). Preferably, the lower end of the exit conduit is located at or adjacent the lower end of the upper inflatable bag. [0069] It is envisaged that, in use, sealant may be transferred to the void between the upper and lower inflatable bags via the transfer conduits. Once the void is full of sealant, excess sealant will flow through the exit conduit. Thus, a user on the surface will be able to determine when sufficient sealant has been used to fill the void between the upper and lower inflatable bags when excess sealant exits the exit conduit. [0070] The exit conduit may be of any suitable form, although in a preferred embodiment of the invention, the exit conduit comprises one or more pipes that extend parallel to the fluid drainage member. The exit conduit may be associated with the fluid drainage member, connected to the outer surface of the inflatable bag, associated with the transfer conduits or may located against the inner surface of the borehole and retained in position by the inflated upper inflatable bag. [0071] In another aspect, the invention resides broadly in a method of installing a fluid drainage assembly comprising a fluid drainage member and an inflatable borehole plug assembly including an inflatable bag in a borehole, the method comprising the steps of: locating the fluid drainage assembly at a desired location within the borehole; actuating inflation means to inflate the inflatable bag such that, when inflated, the inflatable bag at least partially surrounds at least a portion of the fluid drainage member; and creating a seal between a lower region of the fluid drainage member and the borehole and/or an upper region of the fluid drainage member and the borehole using a grout or a foam. [0072] In a preferred embodiment of the invention, the fluid drainage assembly may be located a suitable distance into the borehole using a tamping device. In some embodiments of the invention, the method may further comprise the step of forming a l mI"t seal between a lower region of the fluid drainage member and the inner surface of the borehole and/or an upper region of the fluid drainage member and the inner surface of the borehole. [0074] In a preferred embodiment, the method further comprises the step of forming a temporary seal in the borehole using a temporary inflatable bag prior to the insertion of the fluid drainage member into the borehole. [0075] In some embodiments of the invention, the temporary inflatable bag may be removed prior to the fluid drainage member being inserted into the borehole and the inflatable bag being actuated. Thus, the method may further comprise the step of deflating and/or removing the temporary inflatable bag from the borehole prior to the inflation of the inflatable bag. [0076] The temporary bag may be removed using any suitable technique. However, in a preferred embodiment of the invention, the temporary bag is deflated prior to removal. Deflation of the temporary bag may be achieved using any suitable technique. However, in a preferred embodiment of the invention, the tamping device may include a deflating portion adapted to be used to deflate the temporary bag. Any suitable deflating portion may be provided, although in a preferred embodiment of the invention the deflating portion comprises puncturing means (such as one or more barbs, points, knives, teeth, hooks or the like, or a combination thereof) adapted to puncture the temporary bag so as to result in its deflation. It is envisaged that providing the tamping device with a deflating portion will ensure that the deflating portion is always at hand and that the user can reach the temporary bag once it has been inserted into the borehole. [0077] The deflated temporary bag may be removed from the borehole using any suitable technique. For instance, the deflated temporary bag may be removed by using the puncturing means to "hook" the temporary bag and withdraw it from the borehole. Alternatively, the puncturing means and the temporary bag may be provided with magnetic and/or ferromagnetic portions such that the temporary bag may be removed under the magnetic attraction between the magnetic and/or ferromagnetic portions of the puncturing means and the temporary bag. [0078] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention. [0079] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge. BRIEF DESCRIPTION OF DRAWINGS I %J [0080] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: [0081] Figure 1 illustrates a side view of a fluid drainage assembly according to an embodiment of the invention. [0082] Figure 2 illustrates a cross-sectional view of a fluid drainage assembly according to an embodiment of the present invention. [0083] Figure 3 illustrates a cross-sectional view of a fluid drainage assembly according to an embodiment of the present invention. [0084] Figure 4 illustrates a cross-sectional view of a fluid drainage assembly according to an embodiment of the present invention. [0085] Figure 5 illustrates a cross-sectional view of a fluid drainage assembly according to an embodiment of the present invention. [0086] Figure 6 illustrates a fluid drainage member according to an embodiment of the present invention. [0087] Figure 7 illustrates a portion of a fluid drainage member according to an embodiment of the present invention. DESCRIPTION OF EMBODIMENTS [0088] In Figure 1 there is illustrated a fluid drainage assembly 10 according to an embodiment of the present invention. The fluid drainage assembly comprises a fluid drainage member in the form of a pipe 11 that is inserted into a borehole 12. The pipe has an open lower end 13 through which fluids (including gases such as methane) may enter the pipe 11 and be removed from the borehole 12. [0089] The upper end 14 of the pipe 11 is also open. However, the upper end 14 is provided with a cap 15 having an external screw thread that allows the cap 15 to be connected to further fittings (such as pipes, elbows or the like) to redirect and capture the fluid leaving the borehole 12.

I / [0090] An inflatable bag 16 surrounds the pipe 11 along a portion of the length of the pipe 11. In the uninflated condition shown in Figure 1 the inflatable bag 16 is capable of being inserted into the borehole 12 with the rest of the assembly 10. However, once inflated, the inflatable bag 16 will expand to abut the inner surface of the borehole 12, thereby holding the assembly 10 in place within the borehole 12. [0091] The assembly 10 further comprises a first pair of boundary members in the form of flanges 17 at the lower end of the pipe 11, and a second pair of boundary members in the form of flanges 18 at the upper end of the pipe 11. Each pair of flanges 17, 18 define a void therebetween (19, 20 respectively) in which expanding foam (not shown) is positioned following inflation of the inflatable bag 16. The expanding foam (not shown) not only assists in retaining the assembly 10 in place within the borehole 12, but also prevents toxic or flammable gases from escaping from the borehole 12. [0092] The expanding foam (not shown) is transferred to the lower void 19 through a transfer conduit in the form of a pipe or hose 21 that extends into the borehole 12 parallel to the pipe 11. Expanding foam (not shown) is transferred through the pipe or hose 21 to the lower void 19 where it may expand and harden. [0093] Figure 2 illustrates a fluid drainage assembly 10 according to an embodiment of the present invention. Figure 2 is a cross-sectional view of the fluid drainage assembly 10 of Figure 1 viewed through section C-C of Figure 1. [0094] In this Figure the interior of the inflatable bag 16 may be seen. A pressurised can 22 containing an inflating substance is located within the inflatable bag 16. Actuation of the valve 23 of the pressurised can 22 dispenses the inflating substance within the inflatable bag 16, thereby causing the inflatable bag 16 to inflate until it abuts the inner surface of the borehole 12. A seal is formed between the inflatable bag 16 and the pipe 11 at the upper and lower ends of the inflatable bag 16 so as to prevent the inflating substance escaping from the inflatable bag 16, leading to the deflation of the inflatable bag 16. [0095] The pressurised can 22 is housed within a recess 24 formed by deforming a section of the pipe 11. In this way the assembly 10 may be kept relatively compact so as to be able to fit into a borehole 12. In addition, by housing the pressurised can 22 within the recess means that a user will be able to easily locate the pressurised can 22 from outside the inflatable bag 16 when wishing to actuate the valve 23 and inflate the inflatable bag 16. [0096] The lower end of the transfer conduit 21 may also be seen. The end of the transfer conduit 21 is located within the void 19 such that expanding foam will be delivered to the desired location through the transfer conduit. Once the expanding foam enters the void 19, it will expand to fill the void, but will be prevented from expanding beyond the void 19 by the flanges 17. [0097] Figure 3 illustrates a fluid drainage assembly 10 according to an embodiment of the present invention. Figure 3 is a cross-sectional view of the fluid drainage assembly 10 of Figure 1 viewed through section D-D of Figure 1. [0098] In this Figure it may be seen that the assembly 10 fits relatively snugly within the borehole 12, with the flanges 18 extending outwardly from the pipe 11 to adjacent the inner surface of the borehole 12. [0099] The pressurised can 22 may be clearly seen within the recess 24 formed by the deformation of a section of the pipe 11. In addition, it may be seen that the inflatable bag 16 entirely surrounds the pipe 11 and the pressurised can 22. [00100] In this Figure, the transfer conduit 21 through which expanding foam may be transferred to a lower void (not shown) may be seen. [00101] In Figure 4 there is illustrated a fluid drainage assembly 10 according to an alternative embodiment of the present invention. In this Figure, the assembly 10 comprises an upper inflatable bag 30 and a lower inflatable bag 31 positioned in the borehole 12 such that a void 32 is formed between the upper inflatable bag 30 and the lower inflatable bag 31. Each inflatable bag 30, 31 includes pressurised can 22 that dispenses an inflating substance into the inflatable bags 30, 31 to inflate the inflatable bags 30, 31 so that they expand and are retained in place against the inner surface of the borehole 12. [00102] The assembly 10 includes a fluid drainage member in the form of a pipe 11 that extends to below the lower inflatable bag 31, such that fluid (particularly gases such as methane) may be extracted from the borehole 12. The assembly 10 further comprises a transfer conduit 21 that terminates in the void 32 between the upper inflatable bag 30 and the lower inflatable bag 31. A sealant (such as grout or foam) is transferred into the void 32 through the transfer conduit 21 to fill the void 32 and create a seal to prevent fluid exiting the borehole 12 except through the pipe 11. [00103] The assembly 10 is further provided with an exit conduit 33 through which excess sealant flows when the void 32 is full of sealant. Excess sealant enters the lower end of the exit conduit 33 and exits the exit conduit 33 through the upper end thereof (above surface level) providing the user with a visual indication of when sufficient sealant to fill the void 32 has been transferred through the transfer conduit 21. [00104] In Figure 5 a cross-sectional view through section E-E of the fluid drainage assembly 10 of Figure 4 is illustrated. It may be seen in this Figure that the pipe 11, transfer conduit 21 and exit conduit 33 are located externally to the upper inflatable bag 30. In this embodiment, inflation of the upper inflatable bag 30 results in the pipe 11, transfer conduit 21 and exit conduit 33 being retained in place between the outer surface of the upper inflatable bag 30 and the borehole 12. [00105] In Figure 6 there is illustrated a fluid drainage member in the form of a pipe 11 according to an embodiment of the present invention. The pipe 11 is formed in three sections (an upper section lla, a middle section 1 lb and a lower section 1 Ic) that, in use, are joined together to create a single fluid drainage member. [00106] The upper section 11a of the pipe is provided with a valve 40 that is used to control the flow of fluid out of the borehole (not shown). The upper section 11 a also includes a transfer conduit 21 attached thereto, the transfer conduit 21 adapted to allow grout or expanding foam to be inserted into the borehole. The transfer conduit 21 is also provided with a valve 41 that is used to control the flow of grout or expanding foam into the borehole, and also to prevent the flow of fluid out of the borehole when not in use. [00107] The middle section 1 lb of the pipe is provided with a pair of stop members in the form of flanges 42. In use, an inflatable bag (not shown) will be positioned between the flanges 42, such that the flanges define the limit of movement of the inflatable bag relative to the pipe 11. [00108] Figure 7 illustrates a portion of a fluid drainage assembly according to an embodiment of the present invention. In this Figure, a temporary bag 43 may be seen inserted into a tube 44 representing a borehole. The temporary bag 43 is uninflated, although in use the temporary bag 43 would be inflated so as to form a seal against the inner surface of the borehole. [00109] Once the fluid drainage apparatus has been inserted and the inflatable bag has been inflated, the temporary bag 43 may be removed from the borehole. This is achieved by making use of the deflating portion 45 of a tamping device 46 used to insert the temporary bag 43 to a desired depth within the borehole.

[00110] As can be seen the deflating portion 45 comprises three barbs 47 that are used to puncture and thereby deflate the temporary bag 43. The barbs 47 are fabricated at least partially from a magnetic material that forms a magnetic attraction with a metal washer 48 attached to the temporary bag 43. Withdrawing the tamping device 46 from the borehole therefore also withdraws the deflated temporary bag 43 through the magnetic attraction between the barbs 47 and the washer 48. [00111] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers. [00112] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations. [00113] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

1. A fluid drainage assembly comprising a fluid drainage member adapted for at least partial insertion into a borehole, and an inflatable borehole plug assembly comprising an inflatable bag at least partially surrounding at least a portion of the fluid drainage member and inflation means to inflate the inflatable bag, wherein, upon inflation, the inflatable bag inflates to retain the fluid drainage assembly within the borehole, and wherein a seal is created between a lower region of the fluid drainage member and the borehole and/or an upper region of the fluid drainage member and the borehole using a grout or a foam.

2. A fluid drainage assembly according to claim 1 wherein the fluid drainage member comprises one or more passageways therethrough through which fluid from the borehole passes and exits the borehole.

3. A fluid drainage assembly according to claim 2 wherein the fluid comprises methane or a mixture of gases in which methane is present.

4. A fluid drainage assembly according to any one of the preceding claims wherein the fluid drainage member comprises one or more lengths of pipe.

5. A fluid drainage assembly according to any one of the preceding claims wherein at least a portion of a surface of the inflatable bag includes a non-combustible or fire retardant material.

6. A fluid drainage assembly according to any one of the preceding claims wherein the inflatable bag at least partially surrounds a portion of the circumference of the fluid drainage member.

7. A fluid drainage assembly according to claim 6 wherein the inflatable bag is substantially annular or toroidal and the fluid drainage member passes through a central passageway of the annular or toroidal inflatable bag.

8. A fluid drainage assembly according to claim 6 wherein the fluid drainage member is located against an inner surface of the borehole such that, once inflated, the inflatable bag surrounds a portion of the circumference of the fluid drainage member and retains the fluid drainage member in place against the inner surface of the borehole.

9. A fluid drainage assembly according to any one of the preceding claims wherein the 22 fluid drainage member includes one or more locating members adapted to located and/or retain the inflatable bag in position relative to the fluid drainage member.

10. A fluid drainage assembly according to any one of the preceding claims wherein the inflation means comprises one or more pressurized containers containing an inflating substance.

11. A fluid drainage assembly according to claim 10 wherein the pressurized container is an aerosol can.

12. A fluid drainage assembly according to claim 10 or claim 11 wherein the inflating substance comprises 1,1,1,2-tetrafluoroethane.

13. A fluid drainage assembly according to any one of the preceding claims wherein an upper and/or lower end of the inflatable bag is provided with sealing members adapted to enhance sealing between the inflatable bag and an inner surface of the borehole when the inflatable bag is inflated.

14. A fluid drainage assembly according to any one of the preceding claims wherein the assembly further comprises one or more transfer conduits through which the foam or grout passes.

15. A fluid drainage assembly according to any one of the preceding claims wherein the assembly further comprises an exit conduit through which excess grout or foam flows.

16. A fluid drainage assembly according to any one of the preceding claims wherein the assembly comprises a pair of inflatable bags.

17. A fluid drainage assembly according to claim 16 wherein sealant is transferred to a void between the pair of inflatable bags.

18. A method of installing a fluid drainage assembly comprising a fluid drainage member and an inflatable borehole plug assembly including an inflatable bag in a borehole, the method comprising the steps of: locating the fluid drainage assembly at a desired location within the borehole; actuating inflation means to inflate the inflatable bag such that, when inflated, the inflatable bag at least partially surrounds at least a portion of the fluid drainage member; and 23 creating a seal between a lower region of the fluid drainage member and the borehole and/or an upper region of the fluid drainage member and the borehole using a grout or a foam.