AU763474B2 - Borehole plugs - Google Patents

Description

rW P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "BOREHOLE PLUGS" The following statement is a full description of this invention, including the best method of performing it known to us:

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2 THIS INVENTION relates to an inflatable device, and, in particular, to an inflatable borehole plug, with an inflation delay to permit activation of the inflatable device but with adequate time before too great an expansion so as to allow it to be placed in position, such as being lowered to a desired depth in a borehole in the case of a borehole plug, before expansion of the inflatable device has progressed to its desired final dimensions.

This invention also relates to the use of a particular expansive fluid composition in the induction of inflation of borehole plugs.

A form of inflatable device, a borehole plug in this case, is seen in the specification to prior Australian Patent No 656051 (AU- B-30436/92). Therein is set out an account of the prior art development of borehole plugs, up to its date, and an outline of those 15 general operations in mining and other enterprises, that use inflatable i devices such as in the setting of explosives in boreholes.

The inflatable borehole plug of Patent No 656051 uses a quantity of a non-expansive fluid, such as water, that is expelled first so as to effect a delay in the inflation of the plug by a subsequently delivered gas. The delay fluid is a source of problems, as is explained ooo: •below. The standard inflation gases pose a separate problem in the field, being flammable. There is a particular problem in the hotter environments where the plugs may be in use. At the temperatures 10/06 2003 09:16 FAX 61 7 3221 0597 FISHER ADAMS KELLY Q002 3 experienced in some locations, the usual gases employed for inflation may dissolve in the delay fluid to form undesirable mixtures which can cause problems, particularly to those who may have to remove a misapplied plug to enable a better setting in the borehole. Expansive gases, such as propane and methane, form explosive mixtures in air should they leak, as well as the aforementioned undesirable mixtures in water at higher temperatures.

It is an object of the invention to provide an inflatable device which improves on the above mentioned prior art, enabling more reliable inflation in a manner not dependent on the type of expansive fluid.

It also is an object of the invention to provide an improved expansive fluid that is able to be stored in a storage container over substantial periods in adverse conditions with improved storage properties and properties in use thereof.

Other objects and advantages will hereinafter become apparent.

A single phase can be bought into being by addition of alcohol and particularly ethanol at above 6% in all cases.

The expansive fluid is ideally initially stored in an aerosol can of the kind described in Patent No 656051, or similar kind of container allowing ready release in the field.

Ideally, the inflatable device according to the invention is a fluid tight bag with a construction that effects a delay, or employs such a 10/06 '03 TUE 09:10 [TX/RX NO 9423] 10/06 2003 09:17 FAX 61 7 3221 0597 FISHER ADAMS KELLY Q003 4 bag, in association, for example, with some protective outer sheet or bag in a suitable material (as will be explained herein below). A range of materials as referenced in Patent No 656051 might be used in the making of the fluid tight bag. Generally the inflatable device will be a multi-layered device with an inner fluid tight bag that is effective to contain the expansive fluid and an outer layer effective to engage with the walls of the borehole and protect the fluid tight bag from projections and the like in a borehole wall which might otherwise affect the integrity of the fluid tight bag, allowing escape of the gas, loss of pressure and a failure to maintain position in the borehole. The dual layer form enables selection of an inner material sufficient to contain an expansive fluid with adequate outward pressure, which otherwise might be holed on contact with the wall of a borehole, or be insufficient in frictional contact to hold at the selected height. The outer material can be chosen to effect protection from puncturing of the inner fluid tight bag and/or to provide good frictional contact with the borehole wall.

10/06 '03 TUE 09:10 [TX/RX NO 9423] 10/06 2003 09:17 FAX 61 7 3221 0597 FISHER ADAMS KELLY 004 Various of the alternate construction materials and choices outlined in Patent No 656051 may be applied herein as will be clear to those skilled in the art. In using the inflatable device of the present specification, the present inflatable device is envisaged as a better option than the prior art device and it can be similarly applied over the range of circumstances set out for the product in Patent No 656051.

10/06 '03 TUE 09:10 [TX/RX NO 9423] 10/06 2003 09:17 FAX 61 7 3221 0597 FISHER ADAMS KELLY Q005 6 The invention will now be described with reference to various embodiments that are illustrated in the accompanying drawings, in which: FIG. 1 is an embodiment of an inflatable device using a gathered structure to effect delay of expansion on triggering the device; FIG. 2 is an alternate embodiment using a weak heat seal to control expansion; FIG. 3 is a still further embodiment, using a chambered structure to effect control of expansion of the inflatable device of the first invention; and FIGS. 4-6 show a preferred form of the invention using windings or bands to maintain a cylindrical shape.

In FIG. 1 is seen an inflatable device, in this embodiment in the form of an inflatable borehole plug 10, optionally formed with an outer protective sheet material 11 suited to engagement with the walls of a borehole, as protection for the inflatable device, particularly as it is lowered into place in a borehole, and an inner inflatable fluid tight bag 12 to be inflated by an expansive fluid delivered thereto from a storage container 13 holding a quantity of expansive fluid in a compressed state.

The outer protective sheet material 11 might 10/06 '03 TUE 09:10 [TX/RX NO 9423] simply be a facing sheet or sheets. Ideally the outer protective sheet material 11 is formed as an enclosing bag to protect the inner fluid tight bag 12. The inner fluid tight bag 12 may be selectively inflated by activation of a suitable mechanism by which a pressurised or compressed expansive fluid, such as is described below, in a suitable storage container 13, is delivered to the fluid tight bag 12. The storage container 13 is typically of the type that is known in the art of pressure cans or sprays that are commonly used to deliver materials by action of a propellant expanding through a nozzle.

Typically an activator such as a press button is provided by which the storage container 13 is able to be triggered or released in the field, to deliver or feed its expansive fluid into the fluid tight bag 12 and inflate it. A variety of mechanisms might be used to seal or hold the expansive fluid in storage container 13 until its release into the fluid 15 tight bag 12 is to be effected. Release might be effected by a twist action seal, by the breaking of an elongate seal, by the depression of a valve activator, as will be known to those skilled in the art of storing gases under pressure in pressure cans and the like. Preferably release is by activation of a one shot trigger. A one shot trigger is e readily arranged by fitting a latch to the activation mechanism, operative to hold the activation means in an activated state once it has been activated. This might be effected by a push button or lever that depresses the usual aerosol can valved outlet, the push button or 8 lever being fitted with a locking lip, hook, latch or the like as will be familiar to mechanical engineers. The fluid tight bag 12 of this embodiment may be dimensioned similarly to the outer protective material 11 and disposed with its end 14 folded and held along line 15 by a suitable means such as a tape. Alternatively it might be rolled, or gathered into a generally cylindrical formation as will be described below and it can be held by an elastic or rubber band or filament wrapped around or holding the roll closed as a roll until the inflation pressure overcomes the affect of the band or filament about or around the roll, allowing it to continue inflation. Thus, the process might be for the expansive fluid in storage container 13 to first inflate the volume 16 at the head of the rolled fluid tight bag 12, there being a delay in time until pressure builds in the head volume 16 to a point at which the band or filament lets go and the larger volume of the roll comes into play. Thus, the inflatable device can have a fixed smaller dimension, set by the head volume 16 for a period set by the qualities of the means by which end 14 is held, the pressure of the expansive fluid and/or the size of the initial volume 16. The time delay may be varied by selection amongst the above listed set of parameters, depending on the depth to which the inflatable device, in the case of an inflatable borehole plug, is to be fed before expansion causes it to bind to the walls of the borehole In FIG. 2 is seen an inflatable device 17, again with an optional outer protective sheet 18 or sheets or bag as described 9 above with regard to FIG. 1, an inner fluid tight bag 19 and a storage container 20 of expansive fluid. The fluid tight bag 19 in this embodiment may be formed in plastic based material of the kind which is able to heat sealed, provided in this case with one or more lines of heat style sealing there across, and two in this particular embodiment, as illustrated, being lines 21, 22. A plastic based fluid.

tight bag might be formed with its opposite walls having either inadequately formed heat seals which leak there across under pressure, or heat seals with breaks or discontinuities there along, styled to achieve a similar effect, a controlled feeding of expansive fluid to the other volumes in the fluid tight bag. In use, in this embodiment, fluid from storage container 20 will first fill the head volume 23 until pressure therein is sufficient to start significant leakage into volume 24, and finally into volume 25. The rate of 15 leakage will depend on the pressure in the upstream volume and the degree of effectiveness of the heat seal and/or the size of any discontinuities or breaks effected therein, and this will set the degree of time delay which is gained. It will be clear to those skilled in the gooD art that the delay is established by the combined effect of pressure, o*oo geometry and/or the degree of sealing between the respective volumes.

In FIG. 3 is seen an inflatable device 26, again having an optional outer protective sheet 27 or sheets or bag as described above with regard to the embodiment of FIG. 1, and an inner fluid tight bag 28 with a storage container 29 holding a quantity of an expansive fluid under pressure. The inner fluid tight bag 28 is formed in this embodiment with seals between opposite sides formed in a pattern of lines such as 30 to 32, to split the internal volume of the fluid tight bag into three segments 33 to 35. The serpentine flow of gas expansion of this embodiment slows the rate of inflation of the downstream volumes, causing expansion outwardly in a progressive manner. The lines 30,31 establish a gap for the flow of fluid and the width will determine the rate of flow. The line 32 may be formed across the bag with a gap or gap at each end to establish a flow path. Either or both of these two forms may be used singly or together.

In FIG. 4 is seen a preferred embodiment of the invention in which an outer bag 36 is provided, typically formed from a woven polypropylene material. Inside outer bag 36 is an inflatable fluid tight bag .:i 37 that is inflated, in use, in similar manner to that which is described .:oooi above with regard to FIGS. 1 to 3. The fluid tight bag 37 is inflated by an expansive fluid held in storage container 38. Storage container 38 go••• may be in a form as described above. The fluid tight bag 37 might be disposed inside a second fluid tight bag 39 as an option by which greater reliability might be achieved. A tag 40 might be fitted to the outer

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00 protective bag 36, adapted with an eyelet or the like means by which the 0 •inflatable device might be engaged during lowering into boreholes and the 0 0 like.

1. o o S S 11 In FIG. 5 is seen the inflatable device of FIG. 4 rolled or gathered into the roll or pack seen in end view in FIG. 6. The generally cylindrical shape of the inflatable device is maintained by application of a 'rubber' band or its equivalent, like a winding of resilient material, these being placed as shown in FIG. 5, numbered 41 and 42. The positioning of the bands, or the like, 41 and 42 relative to each other, to the ends of the pack, and the storage container 38 will be chosen in use to effect a delay in expansion sufficient to allow the inflatable device to be positioned as desired before too great an expansion has occurred. The bands 41 and 42, or windings, are to be such as to release the inflatable device after a degree of pressure has built up in the inner fluid tight bag 37. The round profile seen in FIG. 6 is preferable for better lowering performance particularly down angled bore holes. The bands or windings are preferable to adhesive tapes and their like because unlike these others the bands or windings do not weaken or release as does the adhesive of tapes and their like when the temperature rises. The performance of clio• bands or windings is more stable than of an adhesive.

Another aspect of the invention is the use of an expansive fluid composition that includes, in single phase, dimethyl ether and water.

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S. *o 12 The ratio of dimethyl ether to water might be in the range 10:1 to 1:10. A single phase can be bought into being by addition of ethanol at above 6% in all cases. The propellant dimethyl ether is only soluble in water in a 50/50 mix when more than six percent ethanol is present. A preferred, miscible, clear, single phase is achieved by adding 13.7% alcohol to 84.5% water with 1.6% anti-corrosives to an equal weight of dimethyl ether. Anti-corrosive additives, as will be known to chemical engineers, might be added to the composition to improve long term integrity of the storage container and the expansive fluid.

The preferred composition is: dimethyl ether 50 'parts by weight.

water 42.3 parts by weight.

ethanol 6.9 parts by weight.

15 anti-corrosives 0.8 parts by weight.

O*es: In use of the above inflatable devices, the essentially flat 0S@0*e constructions may be gathered, collected, rolled, or otherwise bundled into a cylindrical formation, for lowering into a borehole and 0000 o•0 the like, the manner of formation into a pack for loading being ••oo preferably effective to work with and/or maximise the delay effect of oo o °the particular embodiment. It will be clear to those in the art that a combination of two or more of the above illustrated embodiments that show a variety of ways by which to effect a delay in the flow of 13 expansive fluid through the volume of the fluid type bag might be used to create a desired effect.

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Claims (19)

1. An inflatable borehole plug including: an sealed inflatable inner container of flexible material located in a sealed inflatable outer container of flexible material; and, a pressure vessel located within said inner chamber, said pressure vessel including a pressurized fluid and a latchable valve actuator actuable externally of said outer container, said pressurized fluid comprising a single phase solution of an expansive fluid solute in a substantially non-expansive carrier liquid solvent, said solution, in use, permitting a controlled rate of expansion of said inner chamber by expansion of said expansive fluid when said solution is released into said inner chamber from said pressure vessel.

2. An inflatable borehole plug as claimed in claim 1 including one or more sealed inflatable intermediate containers of flexible material disposed between said inner container and said outer container.

S3. An inflatable borehole plug as claimed in claim 1 or claim 2 ***including an apertured suspension tag extending from an upper region of said outer container.

4. An inflatable borehole plug as claimed in any preceding claim wherein said plug, in an inflated state, is formed as a rolled cylindrical structure secured adjacent opposite ends thereof by releasable bands.

An inflatable borehole plug as claimed in any preceding claim wherein said carrier liquid is water.

6. An inflatable borehole plug as claimed in any preceding claim wherein said expansive fluid is dimethyl ether.

7. An inflatable borehole plug as claimed in claim 6 wherein said solution comprises dimethyl ether and water in a ratio of from 10:1 to 1:10 by weight.

8. An inflatable borehole plug as claimed in claim 7 wherein said solution includes an alcohol.

9. An inflatable borehole plug as claimed in claim 8 wherein said alcohol is ethanol present in an amount greater than 6% by weight.

10. An inflatable borehole plug as claimed in claim 9 wherein said solution comprises: dimethyl ether 50 parts by weight; water 42.3 parts by weight; ethanol 6.9 parts by weight; and anti-corrosives 0.8 parts by weight.

11. A pressurizable fluid for controlled expansion of borehole plugs, iii said fluid comprising a single phase solution of:- a substantially non-expansive carrier liquid solvent; and, an expansive fluid solute, said expansive fluid solute, in use, undergoing expansion when said solution is released from a pressurized container.

12. A fluid as claimed in claim 11 wherein said solvent is water. 12. A fluid as claimed in claim 11 or claim 12 wherein said solutevent is water.

13. A fluid as claimed in claim 11 or claim 12 wherein said solute isether. •ooo• dimethyl ether. .l 16

14. A fluid as claimed in claim 13 wherein said solution comprises dimethyl ether and water in a ratio of from 10:1 to 1:10 by weight.

A fluid as claimed in claim 14 wherein said solution comprises an alcohol.

16. A fluid as claimed in claim 15 wherein said alcohol is ethanol present in an amount greater than 6% by weight.

17. A fluid as claimed in claim 16 wherein said solution comprises:- dimethyl ether 50 parts by weight, water 42.3 parts by weight, ethanol 6.9 parts by weight, and anti-corrosives 0.8 parts by weight.

18. An inflatable borehole plug substantially as hereinbefore described with reference to the accompanying drawings.

19. A pressurizable fluid for controlled expansion of borehole plugs substantially as hereinbefore described with reference to the preferred embodiments. DATED this Twenty-second day of May 2003. TROUPERDALE PTY LTD By their Patent Attorneys FISHER ADAMS KELLY 0 0 0 0 0 OO** oo e*