GB2102860A

GB2102860A - Plug for injecting fluid into rock formations or the like structures

Info

Publication number: GB2102860A
Application number: GB08216833A
Authority: GB
Inventors: Ole Petter Michelsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-06-22
Filing date: 1982-06-10
Publication date: 1983-02-09
Also published as: DE3223040A1; FI821905A0; GB2102860B; SE8203321L; NO149642B; DK250382A; NO820236L; FI821905L; NO149642C

Abstract

A plug (4') for injecting fluid into rock formations or the like structures comprises a tubular body (1) with a one-way valve (3) in one end thereof and an annular sealing member (2) of flexible material, capable of limited axial movement, surrounding the tubular body (1). The sealing member (2) includes a lip or flange (6') for initial sealing and retention of the plug. When inserting the plug (4') into a borehole the flange (6') folds down and thus permits insertion of the plug. At the desired location for the plug. the tubular body (1) is pulled backwards somewhat and this causes the flange (6') to double back on itself so that the flange lies on the outside of the main body of the sealing member (2) and constitutes an initial sealing and retention of the plug (4'). Furthermore there is wedging engagement between the external surface of the tubular body (1) and the internal surface of the sealing member (2) causing radial expansion of the latter when the tubular body (1) is moved rearwardly. Upon introduction of an injection fluid through the plug and the valve (3), an over-pressure arises in the borehole and the tubular body moves further backwards and further increases the radial expansion of the sealing member (2) by said wedging engagement for final sealing and plugging of the injection hole. <IMAGE>

Description

SPECIFICATION Plug for injecting fluid into rock formations or the like structures This invention relates to a plug adapted to close or plug temporarily an injection hole or borehole to enable settable or hardenable fluent material to be injected under pressure through the plug into the injection hole or borehole. Such boreholes are typically provided in rock formations, strata, foundation walls, concrete structures or any other structures or formations where cracks or crevices may occur so that a fluent material in the form of a settable or hardenable fluent grouting, plugging, clogging, choking or sealing medium can be injected into the boreholes for stabilising the formation or structure in question.

It is already known from German DOS 1 634565 to provide a borehole closure device comprising coaxial inner and outer tubes, and a flexible collar arranged coaxially around the inner tube. The outer tube is movable relative to the inner tube to compress axially the flexible collar causing the latter to expand radially and seal against the walls of the borehole. Fluent, hardenable grouting material is then injected into the borehole to seal any cracks in the rock formation or the like structure. However with this known device two tubes are required to radially expand the collar and to inject the grouting material into the borehole. Furthermore the radial expansion of the collar to secure the closure device in the borehole prior to injecting the grouting material is a rather complicated operation.

It is also known from U.K. Patent Specification No. 1,537,386, for example, to introduce grouting material into a borehole via a borehole closure device, the device itself constituting a temporary plug while the grouting material hardens. However this known device requires an extra pipeline for supplying pressure fluid to move an annular, cylinder-iike actuator of the device to radially expand a flexible collar and thereby temporarily seal the closure device within the borehole prior to the injection of grouting material into the borehole. Since the grouting material first has to harden before the borehole closure device can be removed and the next injection can commence, this known device is extremely time-consuming in use and, as a result, makes the sealing with grouting material of a large area a comparatively expensive operation.

The present invention seeks to provide a plug which does not require additional tubing, other than that for supplying grouting material, to enable the plug to be sealed in an injection hole (e.g. a borehole). The invention also seeks to provide a plug which is comparatively simple to produce.

According to one aspect of the present invention there is provided a plug adapted to close or plug temporarily an injection hole to enable a fluent material to be injected through the plug into the injection hole, the plug comprising a tubular body having a one-way valve at its forward end, and an annular sealing member of flexible material which is provided with a flange or lip, surrounds at least part of the external surface of the tubular body and is mounted for limited axial movement relative to the latter, the plug being dimensioned so that, on forward movement of the plug into an injection hole, the said flange or lip is designed to engage the walls of the injection hole, and, on subsequent rearward movement of the tubular body relative to the sealing member, there is wedging engagement between the external surface of the tubular body and the internal surface of the sealing member to cause radial expansion of the latter to ensure plugging of the injection hole during injection of fluent material through the tubular body and said one-way valve into the injection hole.

A plug according to the invention is preferably made of materials which will not corrode after much use. Furthermore a plug according to the invention can be made much lighter than known plugs since only one tube is required. In addition a plug according to the invention is simpler to use than known plugs because of its comparatively light weight and because no screwing operation is required to cause the plug to be sealed in the injection hole.

Conveniently the tubular body is provided with connecting means at its rearward end for releasably connecting the tubular body to a tubular member for the supply of the fluent material to the plug and for injection hole insertion and withdrawal of the plug. Suitably the flange is at the rearward end of the annular sealing member. Conveniently the sealing member has a recessed seat at its forward end which, with a radial enlargement of said tubular body, provides said wedging engagement.

According to another aspect of the present invention there is provided a plug for injecting fluent material into a rock formation or the like structure, the plug comprising a tubular body with a one-way valve at one end thereof and connecting means at the other end thereof for releasably connecting a tubular member adapted to operate both as a fluent material injection tube and a plug insertion tube, and a collar of flexible material surrounding the tubular body and capable of limited axial movement relative to the latter, the collar at or adjacent its rearward end being provided with a flange or lip for initial sealing and retention of the plug and at its forward end being formed with a recessed seat which forms a wedge engagement with a radial enlargement of the tubular body for radial expansion of the collar at the final sealing and plugging of an injection hole.

Typically the connecting means comprises a screw connection, a bayonet connection, or a quick-disconnect coupling. All of these connecting means ensure a quick and rapid connection/disconnection of the tubular member to/from the plug.

So that the main sealing surface between the collar and the injection hole or borehole will not be located at the very front end of the forward edge of the collar, the recessed seat of the collar may be formed with a surface which has a greater inclination than the radial enlargement of the tubular body. This means that the inside edge of the collar will first come into contact with the radial enlargement when the tubular body has been pulled back in a rearward direction relative to the collar so that the collar will expand radially a distance rearwardly of the forward edge of the collar and will thus form the sealing surface with the borehole at this position. This provides a larger and more uniform sealing surface than if, e.g., the outermost and forwardmost edge of the collar were to come first into wedge engagement with the radial enlargement of the tubular body.

The recessed seat of the collar may be frusto-conical.

To prevent drilling cuttings which collect between the tubular body and the collar from obstructing a uniform expansion of the collar, the recessed seat of the collar may be formed as a part of a spherical surface so that any cuttings can be collected here without having a direct effect on the radial expansion of the collar.

To obtain a uniform expansion of the collar, the radial enlargement of the tubular body may be given a frusto-conical configuration.

However, the radial enlargement of the tubular body could of course have other forms, such as a spherical shape, for example. The important factor as regards the shape is that it forms a wedge engagement with the recessed seat and that a radial expansion of the collar is thereby produced.

So that the flange or lip will be easily flexible in relation to the remainder of the collar in the region of the flange, the base of the flange is conveniently made thinner than the rest of the flange and collar at the point where it adjoins the casing, for example by means of indentations at the transition between the collar and the flange.

The valve suitably comprises a flexible body with a slot. This configuration means that little pressure is required to open the valve for introduction of a fluid into the borehole.

The tubular body can be made of aluminum and the casing of rubber. Such a plug embodiment will enable one to drill in it without damaging a drill bit.

The invention will now be described, by way of example, with particular reference to the accompanying drawing, in which: Figure 1 shows a schematic, partly sectioned side view of one embodiment of a plug in accordance with the present invention, Figure 2 shows a schematic, partly sectioned side view of a second embodiment of a plug according to the invention, Figure 3 shows the plug shown in Figure 1 after being pushed into a borehole, Figure 4 shows the plug shown in Figure 1 after having been inserted into a borehole and then withdrawn slightly to adopt a fluid-injection location ready for injection of fluid, and Figure 5 shows the position of the plug shown in Figure 1 upon injection of fluid into the borehole.

Figure 1 shows a plug, generally designated 4, having a tubular or hollow plug body 1 with a oneway valve 3 in the forward end thereof. The rear part of the plug can be provided with internal threads 14 to enable it to be screwed onto a rigid tubular member 9 having corresponding external threads. Other means of connection for connecting the rear end of the plug body 1 to the tubular member 9 could have been utilized instead, such as, for example, a bayonet connection, or a quick-disconnect coupling which may be released/secured, respectively, by pulling/pushing the tubular member relative to the plug body. (These embodiments of the connector means are not illustrated in the drawing.) The plug body 1 is surrounded by a collar or annular casing 2 of flexible material, capable of restricted axial movement relative to the plug body 1.The forward movement of the casing 2 is limited by an annular radial enlargement or expansion 8 at the forward end of the plug body 1 and the rearward movement of the casing 2 is limited by a radial off-set 1 5 at the rearward end of the plug body, both the radial expansion 8 and the radial off-set 1 5 having larger diameters than the internal diameter of the casing.

At the rearward end of the casing 2, a lip or flange 6 is provided for initial sealing and retention of the plug in a borehole. The flange 6 is integral with the casing 2 and is made to be flexible in relation to the casing 2 by an annular groove 12 formed in the outer surface of the casing and an annular indentation 13 opening into the rear end of the casing. At the forward end, the casing 2 is formed with an annular, recessed, internal seat 7 which forms a wedge engagement with the radial expansion 8 of the plug body 1. The recessed seat 7 may be frusto-conical, as shown in Figure 1. The radial expansion 8 of the plug body in the embodiment illustrated in Figure 1 is also given a frusto-conical configuration, but the angle of incline to the surface of the casing 2 is greater than the angle of incline to the surface of the plug body 1.This difference in the angle of incline means that when the plug body is placed in position at the injection location in a borehole and the tubular member 9 is retracted slightly, the innermost edge 1 6 at the forward end of the casing will first come into contact with the frustoconical surface of the radial expansion 8 of the plug body causing the casing 2 to radially expand and sealingly engage with the borehole at the region 10 as may be seen in Figure 4.

A plug 4 in accordance with the invention may have other configurations, and one of these other possible configurations is shown in Figure 2. For like components, the same reference numerals as in Figure 1 are used, but wherever there are substantial differences between the two embodiments, a superscript prime is added to the numeral in Figure 2.

In the embodiment illustrated in Figure 2, the forward, annular, recessed seat 7' is formed as a portion of a spherical surface so that any drill cuttings which might collect between the radial expansion 8 and the casing 2 can be collected between the casing 2 and the plug body without directly affecting the expansion per se of the casing 2. Moreover, the rear flange 6' is provided with deeper indentations 12', 13', rendering the flange 6' more flexible, so that when the plug is being inserted the flange will more readily lie back so as not to obstruct the insertion of the plug.

When the plug is pulled back to effect the initial sealing and retention of the plug 4, 4', the flange will more readily double-back on itself to produce the initial sealing and retention, as shown in Figure 4.

When fluid, e.g. in the form of a sealant mass, is introduced into the borehole, the valve 3, which can be a flexible body with a slot 11, will open as the slot assumes a position as shown in Figure 5.

When fluid is introduced through the tubular member 9, the hollow plug 1 and the valve 3, an over-pressure will occur in the borehole in front of the plug, which will cause the plug body 1 to be pressed backwards; and owing to the wedge engagement between the casing 2 and the plug at the recessed seat 7, 7' of the casing and the radial expansion 8 of the plug body 1, this will cause further radial expansion of the casing 2, thus effecting a further sealing and retention at the surface 10 of the casing. After the desired quantity of fluid has been injected, the valve 3 will close as soon as injection ceases, and the tubular member 9 can immediately thereafter be removed for subsequent use in an injection into the next borehole.

Claims

1. A plug adapted to close or plug temporarily an injection hole to enable a fluent material to be injected through the plug into the injection hole, the plug comprising a tubular body having a oneway valve at its forward end, and an annular sealing member of flexible material which is provided with a flange or lip, surrounds at least part of the external surface of the tubular body and is mounted for limited axial movement relative to the latter, the plug being dimensioned so that, on forward movement of the plug into an injection hole, the said flange or lip is designed to engage the walls of the injection hole, and, on subsequent rearward movement of the tubular body relative to the sealing member, there is wedging engagement between the external surface of the tubular body and the internal surface of the sealing member to cause radial expansion of the latter to ensure plugging of the injection hole during injection of fluent material through the tubular body and said one-way valve into the injection hole.

2. A plug according to claim 1, in which the tubular body is provided with connecting means at its rearward end for the releasable connection thereto of a tubular member for the supply of said fluent material and for injection hole insertion and withdrawal of the plug.

3. A plug according to claim 2, in which said connecting means is a screw connection.

4. A plug according to claim 2, in which said connecting means is a bayonet connection.

5. A plug according to claim 2, in which said connecting means is a quick-disconnect coupling, which is released/secured, respectively, by pulling/pushing the tubular member relative to the tubular body.

6. A plug according to any of the preceding claims, in which said flange or lip is at the rearward end of the annular sealing member.

7. A plug according to any of the preceding claims, in which the sealing member has an annular recessed seat at its forward end which provides said wedging engagement with an annular radial enlargement of said tubular body.

8. A plug according to claim 7, in which said recessed seat has a surface having greater inclination than the inclination of the radial enlargement of the tubular body.

9. A plug according to claim 7 or 8, in which said recessed seat is frusto-conical.

10. A plug according to claim 7 or 8, in which said recessed seat is a part of a spherical surface.

11. A plug according to any of claims 7 to 10, in which the said radial enlargement is frustoconical.

12. A plug according to any of the preceding claims, in which groove means is formed in the annular sealing member in the region of the base of the flange or lip to improve the flexibility of the flange or lip, in the region of its base, relative to the remainder of the sealing member.

13. A plug according to claim 12, in which said groove means comprises a first annular groove formed in the external circumferential surface of the sealing member and a second annular groove formed in an end face of the sealing member.

14. A plug according to any of the preceding claims, in which said one-way valve comprises a flexible body having a slot therein.

1 5. A plug for enabling fluent material to be injected into an injection hole constructed and arranged substantially as herein described with reference to, and as illustrated in, Figures 1, 3, 4 and 5 or Figure 2 of the accompanying drawings.

1 6. A plug for injecting fluent material into a rock formation or the like structure comprising a tubular body with a one-way valve at one end thereof and connecting means at the other end thereof for releasably connecting a tubular member adapted to operate both as a fluent material injection tube and a plug insertion tube, and a collar of flexible material surrounding the tubular body and capable of limited axial movement relative to the latter, the collar at or adjacent its rearward end being provided with a flange or lip for initial sealing and retention of the plug and at its forward end being formed with a recessed seat which forms a wedge engagement with a radial enlargement of the tubular body for radial expansion of the collar at the final sealing and plugging of an injection hole.