INFLATABLE BOREHOLE PLUG

Abstract

An inflatable borehole plug assembly comprising two or more inflatable bags operatively associated with one another, wherein inflation of the inflatable bags results in the formation of the plug.

Description

TECHNICAL FIELD

The present invention relates to an inflatable borehole plug. In particular, the present invention relates to an inflatable borehole plug comprising two or more inflatable bags.

BACKGROUND ART

Bore holes 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.

Inflatable borehole plug assemblies are well known. The assemblies comprise an inflatable bag which can be inflated to form the borehole plug. Inside the bag is a pressurised can which contains the inflating substance. The can is provided with a valve which can be opened to expel the inflating substance into the bag to inflate the bag. The pressurised can has a one-way valve which can be locked into the open position to expel the inflating substance (typically hydrocarbons). The plug assembly is attached to a measured length of rope and is lowered down the hole to be supported by the rope until the plug inflates to be jammed against the wall of the borehole.

In some geographic locations, excessive groundwater levels (caused by, for instance, a high water table or high precipitation levels) create a need to dewater boreholes, typically by pumping water out of the boreholes. However, if excessive groundwater enters a borehole, the pressure of the water may exceed that of a typical inflatable bag, causing it to shrink. In this situation, the explosive charge being supported by the gas bag may fall to the bottom of the borehole with the base charge, and the inflatable bag will rise in the borehole until the pressure of the water in the borehole equalises.

As the base charge and the mid-level charge are now both located at the bottom of the borehole, the firing of the charges can cause large amounts of damage to the base of the wall in which the borehole is located, leading to geological ground damage. When the blasted material is removed, the wall may begin to collapse, creating a significant risk of equipment damage and injury (or even death) to workers.

To prevent the wall from collapsing, actions such as re-drilling and blasting the failing wall are required. These actions increase costs, as well as reducing the productivity of the mine.

Some attempts have been made to overcome these problems. For instance, some efforts have been made to increase the pressure within an inflatable bag in order to resist the pressures to which they are subjected by the influx of groundwater into a borehole. However, these inflatable bags have the serious drawback that the increased pressure increases the risk of the bags exploding. This can cause damage to equipment or injury to workers handling the bags.

In light of the foregoing, there would be an advantage if it were possible to provide an inflatable borehole plug that could be used in areas with high groundwater but that did not present a safety risk to workers handling the plugs.

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

It is an object of the present invention to provide an inflatable borehole plug that overcomes at least one of the advantages of the prior art, or that provides a useful or commercial choice.

With the foregoing in view, the present invention in one form, resides broadly in an inflatable borehole plug assembly comprising two or more inflatable bags operatively associated with one another, wherein inflation of the inflatable bags results in the formation of the plug.

In some embodiments of the invention, each of the two or more inflatable bags includes a pressurised can located therein. Preferably, the pressurised can contains an inflating substance to inflate the inflatable bag.

Preferably, each pressurised can comprises a valve that can be actuated to release the inflating substance to inflate the inflatable bag.

Inflatable bags are already known in the art and it is envisaged that the inflatable bag of the invention can be similar to bags already known. Typically, the inflatable bag comprises multi-layer plastic bags which are gas tight. These bags can be formed from suitable material such as plastics, such as, but not limited to, high density polythethylene (HDPE). As mentioned above, such bags are known in the art. The size and volume of the bag can also vary depending on the borehole size, the weight of explosives to be supported by the plug and the like, and it is considered that this information is already public knowledge.

The pressurised can may be of a type already known in the art and already known to inflate borehole plug bags. The valve is typically such that once opened, the valve stays open which means that the contents of the can will be totally released without interruption until the pressure in the can and the pressure in the bag equalises.

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, although a volatisable liquid is preferred as it will allow greater expansion of the bags.

Typical inflating substances may include, but need not be limited to hydrocarbons such as propane and butane, halohydrocarbons, low boiling point ethers; compressed gases such as nitrogen, carbon dioxide, mixtures thereof.

In some embodiments of the invention, the inflating substance may comprise a hydrocarbon gas or hydrocarbon gas blend, a carrier and an emulsifier.

Any suitable hydrocarbon gas or hydrocarbon gas blend may be used. For instance, the hydrocarbon gas may comprise butane or propane. In some embodiments of the invention, a blend of butane and propane (such as Liquid Petroleum Gas or LPG) may be used. A skilled addressee will understand that the relative proportions of butane and propane in the hydrocarbon gas blend are not critical and may vary as necessary.

The carrier may be of any suitable form. However, in a preferred embodiment of the invention, the carrier is suitable for the hydrocarbon gas or hydrocarbon blend to be dissolved or dispersed in the carrier. Thus, in a preferred embodiment of the invention, the carrier comprises water or a suitable dilute aqueous solution.

Any suitable type of emulsifier may be used in the inflating substance of the present invention. The precise nature of the emulsifier used in the inflating substance is not critical provided at the emulsifier assists in ensuring the inflating substance is a substantially homogeneous mixture. In some embodiments, the emulsifier may have surfactant properties. Alternatively, it is envisaged that, if required, a surfactant may also be added to the inflating substance. A skilled addressee will understand that any suitable surfactant may be used.

The inflating substance may comprise any suitable ratio of components. For instance, the hydrocarbon gas or hydrocarbon gas blend and carrier may together comprise up to about 99.9% of the inflating substance, while it is envisaged that the emulsifier may be present in quantities of up to about 10% of the inflating substance.

The ratio of hydrocarbon gas or hydrocarbon gas blend to carrier in the inflating substance is not critical and may vary depending on the type of hydrocarbon gas or hydrocarbon gas blend and carrier used in the inflating substance. However, it will be understood that the inflating substance must comprise a sufficient quantity of each component in order for the inflating substance to form a substantially homogeneous mixture.

In some embodiments of the present invention, the inflating substance may further comprise alcohol. Alcohol may be present in the inflating substance for a number of reasons, including reducing pressure in the container in which the inflating substance is stored and transported. Any suitable alcohol (or blend of alcohols) may be present. In a preferred embodiment of the invention, the alcohol may be ethanol.

In embodiments of the invention in which alcohol is present, the alcohol may assist in dissolving the hydrocarbon gas or hydrocarbon gas blend in the carrier. In addition, the presence of alcohol in the inflating substance may assist in the creation of a foam when the inflating substance is dispensed from a dispenser. Still further, the addition of alcohol may assist in reducing the flammability of the inflating substance.

When present, it is preferred that the alcohol comprises no more than about 10% of the inflating substance.

In some embodiments of the invention, alternative substances to alcohol may be used. For instance, in one embodiment, acetone may be used instead of alcohol.

In a preferred embodiment of the invention, the inflating substance is substantially non-flammable.

In embodiments of the invention in which the carrier is a dilute aqueous solution, the dilute aqueous solution may contain any suitable material. For instance, the aqueous solution my contain one or more compounds or the like. For instance, in a preferred embodiment of the invention, the aqueous solution may one or more carbomers. Any suitable carbomer may be used. In a particular embodiment of the invention, the carbomer may include a cross-linked polyacrylic acid polymer such as Ultrez 10 manufactured by the Lubrizol Corporation.

The carbomer may be present in any suitable quantity in the aqueous solution. In some embodiments, the carbomer may be present in an amount of no more than 10%. More preferably, the carbomer may be present in an amount of no more than 5%. Still more preferably, the carbomer may be present in an amount of no more than 1%. In one particular embodiment, the carbomer is present in an amount of about 0.5% of the aqueous solution.

In some embodiments of the invention, the aqueous solution may include further compounds in addition to, or instead of, the carbomer. Such compounds may include coco betaine (such as that manufactured under the trade name Empigen BB) or coconut diethanolamide (such as that manufactured under the trade name Empilan FD). In some embodiments of the invention, the coco betaine or coconut diethanolamide is present in an amount of less than 50% of the aqueous solution. More preferably, the coco betaine or coconut diethanolamide is present in an amount of less than 25% of the aqueous solution. Most preferably, the coco betaine or coconut diethanolamide is present in an amount of about 10% of the aqueous solution.

In one embodiment, the aqueous solution may include about 0.5% carbomer and about 10% coconut diethanolamide. The advantages of this combination of components includes the production of a relatively long-lasting foam and a significant reduction in flammability. Specifically, the use of these components produces a slow burning inflating substance, but one which does not burn explosively.

It is envisaged that the use of these components will result in a inflating substance that requires mechanical agitation. For instance, the container or vessel in which the inflating substance is provided may require agitation (such as by shaking the container) after the container is gassed and/or prior to dispensing the contents of the container.

Although it has been stated that either coco betaine or coconut diethanolamide could be used in the inflating substance, it is preferred that coconut diethanolamide is used in preference to coco betaine. This is because it has been found that inflating substances using coco betaine produce a relatively short-lasting foam and a fast burning (but not explosive) foam. On the other hand, the inflating substance using coco betaine does not require any mechanical agitation.

While some specific emulsifiers have been described above (carbomer, coconut diethanolamide and coco betaine), it is envisaged that any suitable type of emulsifier may be used in the inflating substance of the present invention. The precise nature of the emulsifier used in the inflating substance is not critical provided at the emulsifier assists in ensuring the inflating substance is a substantially homogeneous mixture. In some embodiments, the emulsifier may have surfactant properties. Alternatively, it is envisaged that, if required, a surfactant may also be added to the inflating substance. A skilled addressee will understand that any suitable surfactant may be used.

The inflating substance may comprise any suitable ratio of components. For instance, the hydrocarbon gas or hydrocarbon gas blend and carrier may together comprise up to about 99.9% of the inflating substance, while it is envisaged that the emulsifier may be present in quantities of up to about 25% of the inflating substance, and preferably up to about 10.5% of the inflating substance.

The pressure in the can is typically between 150 to 1000 kPa and is usually within the range of about 150 to 500 kPa.

The two or more inflatable bags may be operatively associated with one another using any suitable technique. For instance, the two or more inflatable bags may be operatively associated such that the inflation of the inflatable bags actuates at the same time.

In a preferred embodiment of the invention, the two or more inflatable bags may be physically associated with one another. For instance, the two or more inflatable bags may be retained in proximity to one another by one or more retaining devices. In this way, it may be ensured that the two or more inflatable bags are positioned and retained at the same position within the borehole. In addition, there is no requirement to overinflate each of the inflatable bags (as the combination of the pressure in the two or more inflatable bags is sufficient to maintain the position of the assembly at the desired position in the borehole), and the integrity of each bag may be maintained if the water level in the borehole rises above the location of the inflatable bags.

Furthermore, as each of the inflatable bags is not overinflated or overpressurised, if the inflatable bags leak or are actuated prior to being inserted into a borehole, the likelihood of equipment damage or injury to workers is minimised.

The one or more retaining devices may be of any suitable form. In some embodiments of the invention, the one or more retaining devices may permanently connect the two or more inflatable bags to one another. Alternatively, the one or more retaining devices may temporarily connect the two or more inflatable bags to one another. In some embodiments of the invention, the one or more retaining devices may include rubber bands, adhesive tape, string, rope, sleeves, pouches, tubes or the like, or any suitable combination thereof.

Preferably, at least one of the two or more inflatable bags may be provided with one or more attachment portions adapted to facilitate the lowering of the assembly into a borehole. The one or more attachment portions may be of any suitable form, although it is envisaged that the one or more attachment portions will be adapted to allow the attachment of a lowering device (such as a elongate member including rope, strong, chain, a pole, a rod or the like, or a combination thereof) that allows a user to lower the assembly a suitable distance into the borehole. The one or more attachment portions may be of any suitable form, such as a tag, hook, loop, eyelet, Velcro patch, or the like, or any suitable combination thereof. In a preferred embodiment of the invention, the one or more attachment portions may comprise a tag having an aperture (such as an eye) therein allowing the lowering device to be temporarily attached thereto to lower the assembly into the borehole. In some embodiments, each of the two or inflatable bags may be provided with one or more attachment portions.

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.

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

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:

FIG. 1 illustrates an inflatable borehole plug assembly according to an embodiment of the present invention;

FIG. 2 illustrates an inflatable borehole plug assembly according to an embodiment of the present invention;

FIG. 3 illustrates an inflatable borehole plug assembly according to an embodiment of the present invention;

FIG. 4 illustrates an inflatable borehole plug assembly according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates an inflatable borehole plug assembly 10 according to an embodiment of the present invention. The assembly 10 comprises a pair of inflatable bags 11, each of which contains a pressurised can (obscured) containing an inflating substance.

The bags 11 are operatively associated with one another in that they are adapted to be retained at the same desired depth in the borehole as one another. Furthermore, the bags 11 are operatively associated with one another in that they are adapted to be inflated at the same time.

To ensure that the bags 11 are maintained at the same desired depth in the borehole as one another, the assembly 10 further comprises retaining devices in the form of rubber bands 12 that retain the bags 11 in close proximity to one another.

At least one of the bags (although in the embodiment illustrated in the Figure, each of the bags) 11 is provided with an attachment portion in the form of a tag 13. The tags 13 are provided with an aperture 14 therein that allow an elongate member (such as a rope, string, chain etc) to be attached thereto to enable the bags 11 (or the assembly 10) to be lowered into a borehole.

In FIG. 2, the assembly 10 of FIG. 1 is shown. The assembly 10 has been partially inserted into a metal tube 15 that is of a similar diameter to a typical borehole. In this way, the metal tube 15 is used to simulate the positioning of the assembly 10 in a borehole.

In this Figure, it may be seen that the assembly 10 will be lowered into a borehole (represented by metal tube 15). While this can be performed manually, it is more typical (given the depth of boreholes) that a length of rope or line will be attached to the tag 13 to allow the assembly 10 to be lowered to the desired depth in a borehole.

In FIG. 3, the assembly 10 shown in FIG. 2 is shown. In this Figure, the assembly's position in the metal tube 15 simulates the lowering of the assembly to the desired depth in a borehole. Once the assembly 10 has been lowered to the desired position within the borehole, the inflation of the bags 11 may be actuated.

In FIG. 4, the assembly 10 of FIG. 3 is shown after inflation of the bags 11 has been actuated. It may be seen that the bags have expanded to substantially fill the cross-sectional area of the metal tube 15 simulating a borehole. In this way, the mid-level charge (not shown) that the assembly is adapted to support will not be able to fall to the bottom of the borehole.

In addition, if the water level in the borehole rises, the presence of two bags 11 in the assembly 10 will resist the pressure of the water and the assembly 10 will maintain its integrity. If only one bag was in use, the pressure of rising groundwater in the borehole would be likely to be higher than that in the bag, meaning that the bag would shrink and the explosive charge supported by the bag would fall to the bottom of the borehole. Further, the presence of two bags 11 means that neither bag 11 needs to be overpressurised. This minimises the risk of the bags 11 bursting or leaking either in situ or prior to insertion into the borehole.

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.

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.

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. An inflatable borehole plug assembly comprising two or more inflatable bags operatively associated with one another, each of the two or more inflatable bags including a pressurized can located therein, wherein the pressurized can contains an inflating substance to inflate the inflatable bag, and wherein inflation of the inflatable bags results in the formation of the plug.

2. An inflatable borehole plug assembly according to claim 1 wherein each pressurized can includes a valve that is actuated to release the inflating substance.

3. An inflatable borehole plug assembly according to claim 1 wherein the inflating substance is a volatisable liquid.

4. An inflatable borehole plug assembly according to claim 1 wherein the inflating substance comprises a hydrocarbon gas or hydrocarbon gas blend, a carrier and an emulsifier.

5. An inflatable borehole plug assembly according to claim 1 wherein the pressure in the pressurized can is between 150 and 1000 kPa.

6. An inflatable borehole plug assembly according to claim 1 wherein the two or more inflatable bags are operatively associated with one another such that the inflation of the inflatable bags actuates at the same time.

7. An inflatable borehole plug assembly according to claim 1 wherein the two or more inflatable bags are operatively associated with one another such that the two or more inflatable bags are retained at the same depth in a borehole as one another

8. An inflatable borehole plug assembly according to claim 1 wherein the two or more inflatable bags are retained in physical proximity to one another by retaining devices.

9. An inflatable borehole plug assembly according to claim 8 wherein the one or more retaining devices include one or more rubber bands, adhesive taps, string, rope, sleeves, pouches, tubes or a combination thereof.

10. An inflatable borehole plug assembly according to claim 1 wherein at least one of the two or more inflatable bags is provided with one or more attachment portions adapted to facilitate the lowering of the assembly into a borehole.