AU4245499A

AU4245499A - Plug assembly for borehole

Info

Publication number: AU4245499A
Application number: AU42454/99A
Authority: AU
Original assignee: JADEFOIL INVEST Pty Ltd
Current assignee: JADEFOIL INVESTMENTS Pty Ltd
Priority date: 1998-08-06
Filing date: 1999-08-03
Publication date: 2000-03-02

Description

Our Ref: 741745 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT r Applicant(s): Address for Service: Invention Title: Jadefoil Investments Pty Ltd PO Box Scone New South Wales 1337

AUSTRALIA

DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Plug assembly for borehole The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 _I i_ l I P:\WPDOCS\DYS\SPECI1\69325 I SPE 3/8/99 -1- PLUG ASSEMBLY FOR BOREHOLE This invention relates generally to plug assemblies and more particularly, though not inclusively, to plug assemblies for boreholes.

Boreholes are drilled for the purpose of delivering an explosive charge to a selected location in for example, an underground earth structure. The setting of the explosive charge often requires the borehole to be blocked so that the charge can be set at a desired level.

Boreholes often tend to at least partially fill with water and the presence of the water can prevent successful detonation of the explosive. In attempts to overcome this problem water proof explosives have been used however such explosives are expensive in comparison to other explosives.

Furthermore, it is often the case that more than one explosive charge needs to be used with the explosives being positioned at spaced intervals along the borehole. This requires that the borehole plugs or other decking be placed at the selected depths along the borehole.

The types of decking which have been used in the past include the application of a column of concrete or the like to a section of the borehole to as to space the explosive charges.

Another system employs wooden, concrete or other types of disks with similar cross-sectional dimensions to the borehole which are lowered into the borehole so that they float on the surface of water within the borehole. It is also been proposed to use floatable polyester resins which float on the water and subsequently solidify. A further device which has been used comprises an inflatable plug with a time delay mechanism to allow inflation of the plug at a selected depth to thereby plug the borehole. More recently a gel or slurry explosive has been used to replace the typical decking. Each 'of the above techniques suffers from certain disadvantages. Timber or concrete decking are generally not sufficiently reliable, polyester resins are difficult and slow to place. Internally inflated borehole plugs of the type described in Australian Patent Specification No. 656051 wherein a time delay mechanism permits the inflating plug to be lowered before inflation occurs are somewhat unreliable and slow the installation of the plugs. Where the time delay mechanism comprises a liquid such as water, l___~ljli_ i I P:\WPDOCS\DYS\SPECIE\69325 I.SPE 3/8/99 -2this often freezes and prevents inflation of the plug.

It is an object of the present invention according to one aspect to provide a plug assembly suitable for use in the plugging of boreholes which alleviates one or more of the aforementioned disadvantages.

It is a further object according to another aspect of the present invention to provide an improved method of plugging the borehole.

According to one aspect of the present invention there is provided a plug assembly which is suitable for use in the plugging of boreholes, the assembly including an at least partially expandable main body having an internal chamber therein, and a pressurised container operatively mounted to the main body. The pressurised container includes a discharge outlet and an actuator which is operable to cause the discharge outlet to adopt an open position, the discharge outlet being in fluid communication with the internal chamber of the main body. The pressurised container contains an expandable working fluid therein which is pressurised so that the working fluid within the container includes a liquid "component which partially fills the container. The plug assembly is capable of adopting a -plurality of working modes including one working mode the liquid component of the working fluid within the pressurised container is adjacent the discharge outlet and in another working S.mode the liquid component of the working within the pressurised container is spaced from the discharge outlet.

The arrangement is such that upon operation of the actuator to cause the discharge outlet to adopt its open position, the working fluid is permitted to pass into the internal •"chamber of the main body and is caused to expand so as to thereby cause expansion of the main body.

According to another aspect of the present invention there is provided a method of plugging a borehole using a plug assembly as described above, the method including the steps P:\WPDOCS\DYS\SPECIE69325 I.SPE 3/8199 -3of selecting a working mode for the plug assembly and orienting the pressurised container appropriately, operating the actuator to cause the discharge outlet to adopt its open position and passing the plug assembly along the borehole where it is positioned as a result of the expansion of the main body.

It will be appreciated that the time taken to expand the main body will vary depending on the working mode selected. If the working mode selected is where the liquid component of the working fluid is adjacent the discharge outlet the expandable working fluid will expand relatively quickly when the discharge outlet is opened thereby causing a relatively quick expansion of the main body assembly. In this arrangement the liquid component of the working fluid expands to a gaseous form at the discharge outlet. If on the other hand the working mode selected is that where the liquid component of the working fluid is spaced from the discharge outlet then the rate of expansion will be slower and as such the rate of expansion of the main body of the assembly will be slower. In this arrangement the liquid component of the working fluid will become a gas inside the vessel prior to passing through the outlet. Discharge will continue until the pressure in the pressurised container and ~internal chamber of the main body are about the same.

The pressurised container may be in the form of a vessel which has the discharge outlet at one end thereof. The discharge outlet may include a restricted orifice through which the working fluid can be discharged from the container. The container may be in the form of a generally elongated cylindrical vessel with the discharge outlet at one end.

Preferably, the container is secured to the main body of the plug in a substantially fixed position relatively thereto. Preferably, the container is secured to the internal wall of the internal chamber. The vessel can be upright or inverted in its operating modes. In the upright position the liquid component of the working fluid will be spaced from the discharge outlet and in the inverted position it will be adjacent the discharge outlet. The container can be formed from any suitable material such as metal or plastics and can be pressurised to any desired pressure such as, for example, from about 150Kpa to 600Kpa.

I-I~ -~IC ~I P:\WPDOCS\DYS\SPECIE69325 I.SPE 3/8199 -4- The pressurised container may include a restricting orifice at the discharge outlet and the actuator may comprise a valve for closing the orifice and a trigger for causing the valve to be opened.

The working fluid can be any suitable compressible fluid which is preferably in liquid form when compressed in the pressure vessel. The working fluid may be in the form of a non-flammable compressed gas such as hydrocarbons or other compressed gases or mixture of gases. One example of a suitable gas is R134a refrigerant gas which is almost totally tetrafluoroethane.

The main body of the plug may be in the form of an inflatable flexible bag like member which is gas tight and preferably designed so as to be able to maintain sufficient internal pressure for a period up to four months so as to enable the inflatable container to be maintained securely against the sides of the borehole without damage to the container.

•.The inflatable container may include of one or more layers of material and may be fabricated from materials such as rubber, elastomers, nylon/surlyn coextrusions, polyester, •polythene, polypropylene or polyethylene/nylon extrusions, or metallised plastics film having S"suitable strength and low gas permeability. The container preferably has sufficient strength to prevent the inflatable container from being damaged during lowering into the borehole and may have a texture which provides sufficient frictional grip to hold the main body against the sides of the borehole when inflated. Typically the container is be able to withstand and maintain an internal pressure of from 10 to 350Kpa.

Preferred embodiments of the invention will be hereinbefore described with reference to the accompanying drawings.

Figure 1 is a schematic side elevation of a plug assembly according to the invention in one more of operation; P:\WPDOCS\DYS\SPECIE\69325 I.SPE 318/99 Figure 2 is a detail of the pressurised container shown in Figure 1; Figure 3 is a side elevation of plug assembly shown in Figure 1 in another operating mode; and Figure 4 is a detail of the pressurised container shown in the operating mode as in Figure 3.

Referring to the drawings there is shown an assembly generally indicated at 1 comprising a main body 10 in the form of a generally square or rectangular inflatable flexible bag 11 having a top side 12 and a bottom side 13 with an internal chamber 15 therein. The bag 11 comprises two rectangular or square panels which are sealed together around their peripheral edges 19.

The assembly further includes a pressurised container 20 in the form of an elongated cylinder 21 with an internal chamber 22 and a discharge outlet 23 at one end thereof. The discharge outlet 23 includes a restricting orifice 24 and an actuator 26 which comprises a valve (not shown) which can close the outlet 23 and a trigger 28 for opening the valve.

.i oo The pressurised container 20 has therein a working fluid 30 which is under pressure so that it comprises a liquid component 31.

The container 20 is fixedly secured to the internal wall of the chamber 15 of main *•body 10. The container 20 can therefore be disposed in an inverted position as shown in Figures 1 and 2 or an upright position as shown in Figures 3 and 4. In the inverted position -the liquid component 31 of the working fluid is adjacent the discharge outlet 23 and in the upright position it is spaced therefrom.

To operate the apparatus the working mode is first selected. If the working mode selected is where the liquid component 31 of the working fluid 30 is adjacent the discharge P:\WPDOCS\DYS\SPECIE\693251.SPE 3/8/99 -6outlet 23, as shown in Figures 1 and 2, the expandable working fluid will expand relatively quickly when the discharge outlet is opened thereby causing a relatively quick expansion of the main body assembly. In this arrangement the liquid component of the working fluid expands to a gaseous form at the discharge outlet. The working mode selected is that where the liquid component 31 of the working fluid 30 is spaced from the discharge outlet 23 as shown in Figures 3 and 4 then the rate of expansion will be slower and as such the rate of expansion of the main body of the assembly will be slower. In this arrangement the liquid component of the working fluid will become a gas inside the vessel prior to passing through the outlet. Discharge will continue until the pressure in the pressurised container and internal chamber of the main body are about the same.

It has been found that depending upon the mode of operation selected rates of inflation of the main body can be varied from about one minute to five minutes. Further variations may be effected by selection of orifice size and working fluid.

Finally, it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.

S.

a *ooo

Claims

1. A plug assembly which is suitable for use in the plugging of boreholes, the assembly including an at least partially expandable main body having an internal chamber therein, and a pressurised container operatively mounted to the main body, said pressurised container including a discharge outlet and an actuator which is operable to cause the discharge outlet to adopt an open position, the discharge outlet being in fluid communication with the internal chamber of the main body, said pressurised container containing an expandable working fluid therein which is pressurised so that the working fluid within the container includes a liquid component which partially fills the container, the plug assembly being capable of adopting a plurality of working modes including one working mode in which the liquid component of the working fluid within the pressurised container is adjacent the discharge outlet and in another working mode the liquid component of the working fluid within the pressurised container is spaced from the discharge outlet, the arrangement being such that upon operation of the actuator to cause the discharge outlet to adopt its open position, the working fluid is permitted to pass into the internal chamber of the main body and is caused to expand so as oo *'to thereby cause expansion of the main body.

2. A plug assembly according to claim 1 wherein said pressurised container includes a vessel which has the discharge outlet at one end thereof, the discharge outlet including a restricted orifice through which the working fluid can be discharged from the container.

3. A plug assembly according to claim 2 wherein said container includes a generally D elongated cylindrical vessel with the discharge outlet at one end. &se

4. A plug assembly according to any preceding claim, the container is secured to the main body of the plug in a substantially fixed position relatively thereto.

A plug assembly according to claim 4, wherein the container is secured to the internal wall of the internal chamber. _i _l P:\WPDOCS\DYS\SPECIE\693251.SPE 3/8/99 -8-

6. A plug assembly according to claim 5 wherein the vessel is upright or inverted in its operating modes such that in the upright position the liquid component of the working fluid will be spaced from the discharge outlet and in the inverted position it will be adjacent the discharge outlet.

7. A plug assembly according to any preceding claim wherein the pressurised container includes a restricting orifice at the discharge outlet and the actuator includes a valve for closing the orifice and a trigger for causing the valve to be opened.

8. A plug assembly according to any preceding claim wherein the working fluid is in liquid form when compressed in the pressure vessel.

9. A plug assembly according to any preceding claim wherein the main body of the plug includes an inflatable flexible bag like member which is gas tight.

A plug assembly according to any preceding claim wherein the inflatable container includes of one or more layers of material.

11. A method of plugging a borehole using a plug assembly according to any preceding 20 claim, the method including the steps of selecting a working mode for the plug assembly and orienting the pressurised container appropriately, operating the actuator to cause the discharge Soutlet to adopt its open position and passing the plug assembly along the borehole where it is positioned as a result of the expansion of the main body. S Dated this 3rd day of August, 1999 JADEFOIL INVESTMENTS PTY LTD By Its Patent Attorneys DAVIES COLLISON CAVE