AU759084B2

AU759084B2 - Centraliser Segment

Info

Publication number: AU759084B2
Application number: AU43778/01A
Authority: AU
Inventors: Brian Robert Linaker
Original assignee: Kwik Zip Pty Ltd
Current assignee: Kwik Zip Pty Ltd
Priority date: 2000-05-08
Filing date: 2001-05-08
Publication date: 2003-04-03
Anticipated expiration: 2021-05-08
Also published as: AU4377801A

Description

P/00/009 28/5/91 Regulation 3.2

ORIGINAL

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION Invention Ttle. Bopoe'eeGaA Centraliser The invention is described in the following statement:

TITLE

Centraliser Segment FIELD OF THE INVENTION The present invention relates to a centraliser segment and a centraliser formed of one or more centraliser segments.

The centraliser may be used to centralise a borehole casing though need not be limited to such application. Such borehole casings may be used, for example, in water wells, oil wells and gas wells.

DISCLOSURE OF THE INVENTION In accordance with one aspect of the present invention, there is provided a centraliser segment comprising a plurality of substantially arcuate bows; each of said bows having a first collar portion being of substantially elongate configuration integrally connected to a first end of said bow; each of said bows having a second collar portion being of substantially elongate configuration integrally connected to a second end of said bow; each of said first collar portions being substantially parallel to said second collar portions; first connectors provided at a first end of each of said first collar portions and a first end of each of said second collar portions; second connectors provided at a second end of each of said first collar portions and a second end of each of said 20 second collar portions; wherein each of said first connectors engages one of said second connectors such that at least two of said centraliser segments are connectable.together to form a centraliser which can be located around a borehole casing.

Preferably, said collar portions are fixedly interconnected to the respective ends of the bows Rl 4 Preferably, said centraliser segment is made of a flexibly resilient, corrosion r rsistant material.

Preferably, said first and second connectors are are such that, when interconnected, said first and second connectors allow the relative longitudinal movement between the respective ends of the respective collar portions to reduce the diameter of the centraliser but will resist relative longitudinal movement between the respective ends of the respective collar portions to increase the diameter of the centraliser.

Preferably, said first connectors comprise a series of axially spaced teeth provided on said first and second collar portions on a first face of said centraliser segment and said second connectors comprise one or more axially spaced pawls provided on said first and second collar portions on a second face of said centraliser segment.

Preferably said second connectors further comprise guides for receiving the interengaged first and second collar portions.

Preferably, said first and second collar portions are provided with lug members S15 on a face of said centraliser segment that, in use, faces away from the borehole °el.o• casing.

The lug members can be used to tighten the centraliser segment around the borehole casing.

Preferably, each of said bows extends between said first and second collar 20 portions intermediate the locations of said first and second connectors.

Preferably, flow directing elements are provided on said centraliser segment to in the direction of the flow of grout injected into the region of a borehole accommodating the centraliser.

Preferably, said flow directing elements comprise rib members provided on said bows.

Preferably, said rib members are provided on a face of said centraliser segment t hat, in use, faces the borehole casing, said rib members being offset from the Saxis of the bows.

Preferably, at least one of said rib members is provided with at least one enlarged portion.

Preferably, each of said bows has a strap-like configuration between said first and second collar portions.

In accordance with a second aspect of the present invention, there is provided a centraliser comprising a centraliser segment having the ends of the respective collar portions interconnected via said first and second connectors.

In accordance with a third aspect of the present invention, there is provided a centraliser comprising at least two centraliser segments interconnected in end to end relationship by having the ends of the respective collar portions interconnected via said first and second connectors..

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 15 Figure 1 is a first perspective view of an embodiment of a centraliser segment in accordance with one aspect of the present invention; Figure 2 is a second perspective view of the centraliser segment shown in Figure i Figure 3 is a detailed view of a second connector of the centraliser segment 20 shown in Figure 2; o Figure 4 is a first plan view of the centraliser segment as shown in Figure 1; Figure 5 is an end view of the centraliser segment shown in Figure 4; Figure 6 is a second plan view of the centraliser segment as shown in Figure 2; Figure 7 is an end view of the centraliser segment shown in Figure 6; Figure 8 is a side view of the centraflser segment shown in Figure 6; Figure 9 is a perspective view of two centraliser segments joined together to form a centraliser around a borehole casing; and Figure 10 is a cross sectional view of a borehole having a borehole casing therein with a centraliser located thereon.

BEST MODE(S) FOR CARRYING OUT THE INVENTION in a first embodiment of a centraliser according to the present invention, two or more centraliser segments are connected together to form the centraliser around a borehole casing. An embodiment of a centraliser segment that can be used to form such a centraliser and the centraliser formed thereby is described herein in further detail with reference to Figures 1-10 of the drawings.

In a second embodiment of a centraliser according to the present invention, a single centraliser segment is connected tpgether, i.e. connected to itself, to form the centraliser around a borehole casing.

15 The first embodiment of the centraliser is used with borehole casings having medium to large diameters, whilst the centraliser of the second embodiment is used with borehole casings having small diameters. The centraliser segment used to form a centraliser according to the second embodiment is similar to the centraliser segment used to form a centraliser according to the first embodiment 20 except that it is smaller in size since it is used with borehole casings having small diameters.

The present invention will now be further described with reference to Figures 1of the accompanying drawings.

In Figures 1-8, there is shown a centraliser segment 1 comprising a first collar portion 3, a second collar portion 5, bows 7 extending between the first and second collar portions 3 and 5, first connectors 9 and second connectors 11.

Two or more centraliser segments 1 may be connected together via the first and second connectors 9 and 11, as will be further described herein.

A first connector 9 is provided on the first collar portion 3 and on the second collar portion The first connectors 9 are provided on a first face 10 of the centraliser segment 1.

Each first connector 9 is provided as a series of teeth 13. The teeth 13 of the first connectors 9 extend on the first collar portions 3 and 5, respectively, from respective first ends 15 thereof. The series of teeth 13 terminate before the location at which a bow 7 extends between the first and second collar portions 3 and Each second connector 11 is provided as a guide 24 and a series of pawls 19 adjacent respective second ends 21 of the collar portions 3 and 5. Each guide 24 consists of a series of L-shaped lugs 24A extending on each side of the pawls 19 in an opposed manner.

The second connectors 11 are provided on a second face 17 of the centraliser segment 1.

The teeth 13 and pawls 19 of the first and second connectors 9 and 11, respectively, form a pawl and ratchet connection arrangement. This allows the 20 relative positional engagement between the first and second connectors 9 and 11 to be selected as will be further described later herein.

The first and second collar portions 3 and 5 are provided as strap-like members and are substantially parallel to one another.

The bows 7 extend between the first and second collar portions 3 and intermediate the locations of the first and second connectors 9 and 11 on the first and second collar portions 3 and The bows 7 have an inbuilt curvature in their longitudinal direction, in which they extend, between the first and second collar portions 3 and 5. This can be best seen in Figures 5 and 7.

The bows 7 are strap-like members.

The bows 7 are flexibly resilient.

The bows 7 are provided with rib members 22 on the first face 10 of the centraliser segment 1 that, in use, faces the borehole casing. The rib members 22 extend diagonally across the width of the bows 7 for substantially the length of the bows 7.

The rib members 22 are each provided with an enlarged portion 22a. The enlarged portion 22a is provided midway along the length of each rib member 22.

A pair of lugs 23 is provided on each of the first and second collar portions 3 and 5. The lugs 23 are provided on the second face 17 of the centraliser segment 1 that, in use, faces away from the borehole casing. One of the lugs 23 on each collar portion 3 and 5 is located adjacent the respective first ends 15 of the collar portions 3 and 5. The other lug 23 on each collar portion 3 and 5 is located approximately midway along the length of the respective collar portions 3 and Slots 25 are provided in the collars 3 and 5. The slots 3 and 5 increase the flexibility of the collars 3 and 5 and save on the raw material from which the 20 centraliser segment 1 is made. However, the slots 25 may, alternatively, be omitted.

The centraliser segment 1 is made of a corrosion resistant material.

The manner of operation and use of the centraliser segment 1 of the present invention will now be described.

Two or more centraliser segments 1 are able to be connected together via the first and second connectors 9 and 11 to form a centraliser 30 shown in Figures 9 and 10. In Figures 9 and 10, the centraliser 30 is formed of two centraliser segments la and 1b, respectively, connected together around a borehole casing 100. This is done by inserting the ends 15 of the first and second collar portions 3 and 5 of the first centraliser segment 1a beneath and between the opposed L-shaped lugs 24A of the guides 24 of the second connectors 11 of the second centraliser segment lb. This causes the teeth 13 of the first connectors 9 of the first centraliser segment la to engage with the pawls 19 of the second connectors 11 of the second centraliser segment lb. Similarly, the ends 15 of the first and second collar portions 3 and 5 of the second centraliser segment 1b are inserted beneath and between the opposed L-shaped lugs 24A of the guides 24 of the second connectors 11 of the first centraliser segment la. This causes the teeth 13 of the first connectors 9 of the second centraliser segment lb to engage with the pawls 19 of the second connectors 11 of the first centraliser segment la. The above described procedure is carried out with the centraliser segments la and 1b positioned around the borehole casing 100.

15 The teeth 13 of the first connectors 9 of the first centraliser segment la engage with pawls 19 of the second connectors 11 of the second centraliser segment 1 b.

This can be seen in Figure 9. Similarly, the teeth 13 of the first connectors 9 of the second centraliser segment lb engage with pawls 19 of the second connectors 11 of the first segment la. This, however, is obscured in Figure 9 by the borehole casing 100.

The connections between the first and second centraliser segments la and lb can be adjusted by using a tool, such as a pair of pliers, to grip the lugs 23a adjacent the ends 15 of the first centraliser segment la and the lugs 23b located midway along the length of the collar portions 3 and 5 of the second centraliser segment lb to thereby pull the collar portions 3a and 5a of the first centraliser segment la further through the guides 24b of the collar portions 3b and 5b of the second centraliser segment lb. In this way, the first and second centraliser segments la and 1b, that form the centraliser 30, can be tightened around the borehole casing 100.

The ability to pull the collar portions 3 and 5 of one centraliser segment 1 through the guides 24 of another centraliser segment 1 until the centraliser 30 is tightly affixed around the borehole casing 100 means that the relative positional engagement between the first and second connectors 9 and 11 can be selected to achieve the required tightness. Additionally, it means that a centraliser, whether made up of one or more centraliser segments according to the present invention, can be adjusted to fit a range of borehole casings 100 of differing diameters.

If the borehole casing 100 is of a large diameter such that it cannot be surrounded by a pair of centraliser segments 1, then three or more centraliser segments may be connected together via the first and second connectors 9 and 11 around the borehole casing 100.

A centraliser 30 is fixed around a borehole casing 100 prior to the borehole casing 100 being inserted into a borehole 102. A borehole casing 100 is generally made by connecting casing lengths together as the borehole casing 100 is inserted deeper into the borehole 100. Typically, these casing lengths .oo.

may be six or nine metres in length. A centraliser 30 may be provided every few metres along the length of the borehole casing 100.

The amount of curvature in the bows 7 of the centraliser segmentsl forming a °i centraliser 30 can be varied to accommodate the clearance in the borehole 102 into which the borehole casing 100 is being inserted. This is done by first affixing one collar of the centraliser 30 around the borehole casing 100. Using the centraliser 30 in Figure 9 as an example, the collar portions 5a and 5b of the first and second centraliser segments la and lb may first be tightly affixed together around the borehole casing 100 to form a first collar of the centraliser 30. If an increased curvature in the bows 7 is required, then the collar portions 3a and 3b are pushed downwardly along the borehole casing 100, in the direction of arrow A, before they are firmly affixed around the borehole casing 100. Pushing the collar portions 3a and 3b in the direction of arrow A, towards the collar portions and 5b, will increase the curvature of the bows 7. Pulling the collar portions 3a and 3b upwardly, in the direction of arrow B will lessen the curvature of the bows 7.

Figure 10 shows a borehole casing 100 in position in a borehole 102 with a centraliser 30 affixed around the borehole casing 100. The bows 7 of the centraliser segments 1 which form the centraliser 30 contact the wall 104 of the borehole 102.

Due to the bows 7 being flexibly resilient, as the borehole casing 100 is pushed into the borehole 102, the bows 7 deform if they encounter any obstruction in the wall 104 of the borehole 102. Furthermore, once the bows 7 pass over the obstruction, they will return to their normal undeformed position to maintain contact with the wall 104 of the casing 100.

Maintaining the bows 7 in contact with the wall 104 of the borehole 102 ensures that the borehole casing 100 remains centralised as it is pushed further down into the borehole 102.

The enlarged portions 22a of the rib members 22 ensure that, in the event of a collapse of the wall 104, a minimum clearance is retained between the bows 7 and the borehole casing 100. This minimum clearance is determined by the thickness of the enlarged portions 22a.

Once the borehole casing 100 is in position in the borehole 102, a grout discharge pipe can be lowered down the borehole casing 100. Grout is then discharged from the opening of the grout discharge pipe so that it flows into the annular space between the borehole pipe 100 and the wall 104 of the borehole 102. The grout then flows upwardly in the annular space and fills the annular space with grout as shown by reference numeral 106.

The ribs 22 of the centraliser segments 1 aid in the direction of the flow of the grout as it flows upwardly in the annular space around the centralisers 30. This assists in achieving an even grout filling of the annular space without channels and cavities.

Once the grout 106 has set, the borehole casing 100 remains centralised in the borehole 102 and can be used for its intended purpose.

The centraliser according to the second embodiment of the present invention is used in a similar manner to the centraliser according to the first embodiment of the present invention, except that the centraliser of the second embodiment is used with borehole casings having a relatively small diameter such that only a single centraliser segment is used to form the centraliser around the borehole casing. Accordingly, in the second embodiment of the centraliser, the centraliser segment used has its first connector 9 on the first collar portion 3 connected to the second connector 11 on the first collar portion 3 and the first connector 9 on the second collar portion 5 is connected to the second connector 11 on the second collar portion In addition, if required, two or more centraliser segments that are used to form a centraliser according to the second embodiment may be connected together around a borehole casing to form a centraliser in similar manner to the centraliser segment 1 that is used to form a centraliser according to the first embodiment of the present invention. However, the centraliser segment 1 intended to form a centraliser for medium to large diameter borehole casings, S 15 would usually be too large to be used to form a centraliser formed of only a single centraliser segment on a small diameter borehole casing .ooo S•Modifications and variations such as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

*°oo.

Claims

1. A centraliser segment comprising: a plurality of substantially arcuate bows; each of said bows having a first collar portion being of substantially elongate configuration integrally connected to a first end of said bow; each of said bows having a second collar portion being of substantially elongate configuration integrally connected to a second end of said bow; each of said first collar portions being substantially parallel to said second collar portions; first connectors provided at a first end of each of said first collar portions and a first end of each of said second collar portions; e.o. second connectors provided at a second end of each of said first collar portions and a second end of each of said second collar portions; wherein each of said first connectors engages one of said second connectors such that at least two of said centraliser segments are connectable together to form a centraliser which can be located around a borehole casing.

2. A centraliser segment according to claim 1, wherein said first and second connectors are such that, when interconnected, said first and second 20 connectors allow the relative longitudinal movement between the respective ends of the respective collar portions to reduce the diameter of the centraliser but will resist relative longitudinal movement between the respective ends of the respective collar portions to increase the diameter of the centraliser.

3. A centraliser segment according to claim 1 or claim 2, wherein said first 1 connectors comprise a series of axially spaced teeth provided on said first and second collar portions on a first face of said centraliser segment and said second connectors comprise one or more axially spaced pawls provided on said first and second collar portions on a second face of said centraliser segment.

4. A centraliser segment according to any one of the preceding claims, wherein said second connectors further comprise guides for receiving the interengaged first and second collar portions. A centraliser segment according to any one of the preceding claims, wherein said first and second collar portions are provided with lug members on a face of said centraliser segment that, in use, faces away from the borehole casing.

6. A centraliser segment according to any one of the preceding claims, wherein each of said bows extends between said first and second collar portions intermediate the locations of said first and second connectors.

7. A centraliser segment according to any one of the preceding claims, wherein flow directing elements are provided on said centraliser segment to aid in the direction of the flow of grout injected into the region of a borehole accommodating the centraliser.

8. A centraliser segment according to claim 7, wherein said flow directing 20 elements comprise rib members provided on said bows.

9. A centraliser segment according to claim 8, wherein said rib members are provided on a face of said centraliser segment that, in use, faces the borehole casing, said rib members being offset from the axis of the bows. centraliser segment according to claim 8 or claim 9, wherein at least one of said rib members is provided with at least one enlarged portion.

11.A centraliser segment according to any one of the preceding claims, wherein at least one of said bows has a strap-like configuration between Ssaid first and second collar portions.

12.A centraliser comprising a centraliser segment according to any one of the preceding claims, having the ends of the respective collar portions interconnected via said first and second connectors.

13.A centraliser comprising at least two centraliser segments according to any one of claims 1 to 11, interconnected in end to end relationship by having the ends of the respective collar portions interconnected via said first and second connectors.

14.A centraliser segment according to any one of claims 1 to 11, wherein said centraliser segment is made of a flexibly resilient corrosion resistant material. centraliser segment according to any one of claims 1 to 11, wherein said collar portions are fixedly interconnected to the respective ends of the bows.

16.A centraliser according to claim 12 and substantially as herein described. S 15 17.A centraliser segment substantially as herein described with reference to the accompanying drawings.

18.A centraliser substantially as herein described with reference to the accompanying drawings. 20 Dated this TWENTY THIRD day of JANUARY, 2003 KWIK-ZIP PTY LTD Applicant Wray Associates Perth, Western Australia Patent Attorneys for the Applicant(s)