GB2381280A

GB2381280A - Adjustable centraliser with separate control tool

Info

Publication number: GB2381280A
Application number: GB0125418A
Authority: GB
Inventors: Stephen Samuel Mckelvey
Original assignee: UWG Ltd
Current assignee: UWG Ltd
Priority date: 2001-10-23
Filing date: 2001-10-23
Publication date: 2003-04-30
Anticipated expiration: 2021-10-23
Also published as: GB2381280B; GB0125418D0

Abstract

An adjustable centraliser 100 is mounted on a tubular 200 and has radially projecting elements 120 to engage an outer casing. These elements are mounted on the body of the centraliser and are displaced radially therefrom by separation members. The projecting elements may engage with guide grooves 140 in supporting members 130, the grooves diverging from the longitudinal axis of the centraliser so that movement of the elements incorporates both axis parallel and radial components. A control tool engages the centraliser via rod 125 and moves the projecting elements outwards until they come into contact with the casing, when the separation members (shims) are inserted in between them and the body of the centraliser. The control tool may carry a variety of different thicknesses of shim so that clearance between the expanded centraliser and the casing can be minimised. The guide grooves also maintain the projecting elements parallel to the centraliser axis and may be engaged via pins 145.

Description

CENTRALISER This invention relates to the field of centralisers for use in maintaining two tubular members in a substantially co-axial arrangement. The invention is of particular importance to, but is not limited to, the extraction and production of petro-chemicals.

When one pipe is constrained within the diameter of a larger pipe, it is desirable to minimise the gap between the two pipes in order to reduce the mechanical damage that can be caused by the two pipes clashing. This is a particularly important consideration for pipelines used in oil and gas exploration and production.

For example, offshore oil production platforms have pipelines, which are referred to as conductors, that connect the platform to the oil or gas resource being extracted from underneath the sea bed. At a number of points between the platform and the sea the conductor will. pass through a number of guides, each of which is securely attached to the structural framework of the platform. It is clearly important for safety reasons, and to ensure that the conductors function for their designed lifetime, that the conductors are securely held concentrically within the guides, even under the influence of waves and scorms.

There are a number of products, commonly referred to as centralisers, that are available for this purpose.

Centralisers are clamped to the inner tubular member (the

conductor in the above example) and have a number of protrusions that extend between the inner tubular member and the outer tubular member (the guide string in the above example). They can either provide a constant radial extension (these centralisers are referred to as fixed centralisers) or the radial extension can be varied in order to provide a better fit (i. e. a smaller gap) between the inner and outer tubular elements (and these are referred to adjustable centralisers). GB-A-2 277 336 describes an example of an adjustable centraliser.

According to a first aspect of the invention there is provided a centraliser comprising a main body adapted to be mechanically coupled to a tubular member, a plurality of centralising elements, each centralising element being mounted on the main body and extending radially from the main body, one or more of the centralising elements being adjustable such that the radial extension between the main body and the adjustable centralising element can be varied, the variation being limited, in use, by one or more extension members that separate the body from the adjustable centralising element.

The centraliser according to the present invention has a number of advantages over known centralisers. For example, the simplified design of the centraliser reduces the manufacturing cost of the centraliser. This simplified design reduces the complexity of a centraliser installation and minimises the time and cost associated with the installation. Furthermore, the centraliser

according to the present invention is more suitable for installation into situations where there is a small annular gap between the two tubular members.

It is preferred that each adjustable centralising element is resiliently mounted on the main body. Each adjustable centralising element may further comprise engagement means for engaging with an installation tool. Additionally, each adjustable centralising element may further comprise an alignment means that, in use, maintains the centralising element in a substantially parallel alignment with the central axis of the main body. Furthermore, each adjustable centralising element may comprise alignment means that, in use, restrict the movement of the respective adjustable centralising element such that the centralising element has components of motion both parallel with and perpendicular to the central axis of the main body.

The invention will now be described, by way of example only, with reference to the following Figure in which : Figure 1 shows a schematic. depiction of a centraliser according to the present invention.

Figure 1 shows a schematic depiction of a centraliser according to the present invention, in which a centraliser 100 is shown mechanically coupled to conductor 200. The centraliser 100 has a split can configuration and comprises a plurality of centralising elements 110

arranged around the perimeter of the centraliser 100. Each centralising element 110 is arranged substantially parallel to the central axis of the conductor 200. The arrangement shown in Figure 1 has four centralising elements (only three of which are shown in the isometric perspective) which are arranged equidistantly around the perimeter of the centraliser. It will be understood readily that the invention could also be implemented using a greater or lesser number of centralising elements or that the centralising elements could be arranged at unequal intervals around the centraliser 100. Additionally, a number of non-adjustable centralising elements could be used in conjunction with a number of adjustable centralising elements according to the present invention.

The centraliser is secured to the conductor by the action of clamp 160, which is secured using a plurality of nuts and bolts 165 (the exact nature of the fastening of the centraliser is not relevant to the present invention as long as a secure mechanical coupling can be established).

Each coupling element 110 comprises a blade 120 which is held between two supporting elements 130. The supporting elements are mounted to the centraliser such that the blade may be extended away from the centraliser. Preferably the elements comprise a plurality of angled grooves 140a, 140b, within which a respective pin 145a, 145b, is located. These arrangements ensure that the blades always remain substantially parallel to the central

axis of the conductor and that any movement of the blade parallel to the central axis of the conductor will cause the blade to move in a direction that has components of motion both parallel and perpendicular to the central axis of the conductor (and also any movement of the blade perpendicular to the central axis of the conductor will cause the blade to move in a direction that has components of motion both parallel and perpendicular to the central axis of the conductor). Each blade additionally comprises an engagement member 125, which in a preferred embodiment comprises a bar that passes through the blade and has a perpendicular alignment to the blade.

In operation a centraliser will be clamped to a conductor, near to the open end of a guide. An installation tool is attached to the engagement member 125 of one of the centralising elements and is used to move the blade of that centralising element away from the surface of the centraliser until the blade makes contact with the inner surface of the guide. The separation between the supporting element 120 and the centraliser is measured and an appropriate spacing element is formed from one or more shims; this spacing element is substantially the thickness of the measured gap and is inserted so as to separate the blade and the supporting elements from the centraliser.

The angled grooves and pins act to urge the blade towards the centraliser, holding the spacing element in place. The separation between the blade and the guide has been reduced, thus reducing the potential travel of the

conductor within the guide.

Each of the centralising elements is in turn adjusted and fixed in position, as described above, so that all of the blades 120 are located as near as possible to the inside of the guide. The installation tool is supplied with a number of shims having a variety of thicknesses. Through selection of a suitable combination of shims to build up a spacing element it should be possible to control the separation between the blade and the guide to be less than the thickness of the thinnest shim. A typical radial gap between a conductor and a guide used in a petro-chemical application is 10 cm or larger, and a range of shims with thicknesses of typically 1 cm or greater will be supplied.

A centraliser as described above is suitable for use in the oil and gas exploration and extraction industries (although it can also be used in other technical applications in which pipes and tubular elements in general need to be held concentrically) and can be installed in situ on a platform connector or on shore before a connector is installed. It will be clear from the above discussion that. it is necessary for the engagement member of the centralising elements to be accessible in order for the installation tool to engage the member.

Claims

CLAIMS 1. A centraliser comprising a main body adapted to be mechanically coupled to a tubular member, a plurality of centralising elements, each centralising element being mounted on the main body and extending radially from the main body, one or more of the centralising elements being adjustable such that the radial extension between the main body and the adjustable centralising element can be varied, the variation being limited, in use, by one or more extension members that separate the body from the adjustable centralising element.
2. A centraliser according to claim 1, in which each adjustable centralising element further comprises engagement means for engaging with an installation tool.
3. A centraliser according to any preceding claim in which each adjustable centralising element further comprises an alignment means that, in use, maintains the centralising element in a substantially parallel alignment with the central axis of the main body.
4. A centraliser according to any preceding claim in which each adjustable centralising element further comprises alignment means that, in use, restrict the movement of the respective adjustable centralising element such that the centralising element has components of motion both parallel with and perpendicular to the central axis of the main body.

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5. A centraliser substantially as hereinbefore described, with reference to and as described in Figure 1.