GB2044320A

GB2044320A - Device for Locating Control Elements in Well Bores

Info

Publication number: GB2044320A
Application number: GB8006907A
Authority: GB
Original assignee: LASALLE Manufacturing 15 Ltd
Current assignee: LASALLE Manufacturing 15 Ltd
Priority date: 1979-03-02
Filing date: 1980-02-29
Publication date: 1980-10-15
Also published as: GB2044320B

Abstract

A locating device 11 for use within a casing string in a well bore locates a heavy armoured coaxial cable relative to a flow pipe within the casing string and also acts as a pipe protector. The rubber body 12 is secured around the flow pipe, and has an outwardly extending side portion 23 having a recess 25 for the coaxial cable. The general outline of a cross- section of the body 12 taken perpendicular to the axis of the flow pipe is substantially egg-shaped, and a steel core embedded in the body 12 has a cross-sectional shape which is also egg-shaped and corresponds generally to the said outline. Where a series of asymmetrical locating devices are secured along a flow pipe in an inclined casing and are aligned in corresponding manner, the locating devices locate the coaxial cable on the upper side of the flow pipe. <IMAGE>

Description

SPECIFICATION Locating Device The present invention relates to a locating device for use within a tubular structure in a well bore and is concerned in particular but not exclusively with a locating device for locating a heavy armoured coaxial cable relative to a flow pipe within a casing string in a well bore.

In a well bore which is completed and in production, for example an oil or gas well, there is normally positioned within the well bore a casing string comprising a number of connected steel casing sections (known as casing joints), and within the casing string there is positioned a hollow cylindrical flow pipe through which the oil or other product is pumped. During the pumping operation, the casing and flow pipe are subjected to considerable vibration and lateral movement and it is well known to provide pipe protectors for locating the flow pipe within the casing and for protecting the flow pipe from damaging contact with the inner walls of the casing. These known pipe protectors (as described for example in U.K.

Patents Nos, 1,375,773; 1,209,001; and 1,173,202) commonly consist of a generally cylindrical sleeve of elastomeric material such as rubber, usually with a reinforcing framework or core embedded in the rubber. Usually these pipe protectors are split and are hinged or sprung to allow the protector to be opened and secured around the flow pipe. The protector is then secured in place, for example by a wedge shaped pin or tongue forced through inter-digiting apertured fingers.

It is also now standard practice to run down the space between the steel casing string and the inner flow pipe one or more control elements which may be hydraulic control lines and/or electrical cables. These control elements are used to monitor and control pumping and other equipment at the base of the well, and may monitor conditions in the well bore to detect and correct malfunction or damage. It is known (as disclosed for example in U.K. Patent No.

1 ,478,206) to arrange for the pipe protector to constitute also a locating device for locating the control element or elements relative to the flow pipe. This is achieved in Specification No.

1,478,206 by providing in the elastomeric body of the pipe protector one or more recesses opening to an external surface of the pipe protector and having a "key hole" shape which allows the control elements to be snapped into place by deforming the elastomeric material around the process. Such an arrangement has some advantage in ease of placement of the control element, but has disadvantages in that the cables are not usually securely held in the pipe protector since only the shape of the "key hole" recess maintains the grip on the control element.

Such an arrangement can be used in some circumstances for light hydraulic control lines of diameter small compared with the diameter of the flow pipe, but the arrangements referred to are not satisfactory for securing larger, heavier control elements such as an armoured coaxial cable.

All the arrangements shown in the previously mentioned Specification No. 1,478,206 provide a locating device which has a symmetrical crosssection relative to the general longitudinal axis of the assembly. To attempt to provide the required degree of protection for the control elements, the pipe protector is made excessively bulky, and considerable quantities of elastomeric material need to be utilised. Also, the symmetrical arrangements shown with a number of outwardly projecting portions provide a number of relatively sharp edges and cavities in the design.

In an alternative arrangement for locating control elements in the casing of a well bore, a pipe protector includes recesses for locating control elements, the recesses opening from an internal surface of the pipe protector which is adapted to be secured around and seat against a flow pipe. Where known means have been used to locate a relatively large diameter, heavy control element such as an armoured coaxial cable, the cable has been located on the pipe by a metal strap around the pipe and has in effect been clamped or strapped against the flow pipe. Such an arrangement has a number of disadvantages in that friction or contact between the cable and the flow pipe tends to produce wear, and also the immediate contact of dissimilar metals produces corrosion by electrolytic action.

It is an object of the present invention to provide a locating device for use within a casing string in a well bore which is particularly, but not exclusively, applicable to locating relatively large diameter heavy control elements such as armoured coaxial cables, which device avoids or reduces the disadvantages set out above in relation to the known pipe protectors and locating devices.

According to the present invention there is provided a locating device for use within a tubular structure in a well bore, the device comprising a body adapted to be secured around a flow pipe with the pipe aligned along a longitudinal axis of the body, the body having an outwardly extending side portion which has a recess for housing a control element and for locating the control element relative to the flow pipe, the body having a shape such that the general outline of a crosssection of the body taken perpendicular to the said longitudinal axis is asymmetrical to the extent of having no more than one axis of symmetry in the plane of the cross-section.

In preferred arrangements the said body comprises a mass of elastomeric material such as rubber. Preferably the body has embedded therein a reinforcing core, for example of steel, the core being such that the shape of a cross-section of the core taken perpendicular to the said longitudinal axis corresponds substantially to the shape of the general cross-sectional outline of the body. Conveniently the body is in the form of a sleeve for encompassing a flow pipe, the sleeve being split and being openable at the split to be placed around the flow pipe and secured thereto.

The body may be hinged to open at the split or may be sprung to be opened by deforming the body, Correspondingly the reinforcing core may be hinged, or for example may comprise a spring member. Conveniently the locating device also serves the function of a pipe protector for locating a flow pipe relative to the tubular structure and for protecting the pipe from adverse contact with the inner surface of the tubular structure which may for example be a casing string.

The said body may have more than one outwardly extending side portion for example when more than one control element is to be located relative to the flow pipe, and in such an arrangement each side portion may have a recess for housing one or more control elements.

Similarly, the body may be adapted to be secured around more than one flow pipe within the casing string in a well bore. However the invention has particular application where the body is adapted to be secured around a single flow pipe, and has a single generally cylindrical major internal surface adapted to engage and seat against the said flow pipe. Also preferably the body has a single outwardly extending side portion. Such a single side portion may have more than one recess for housing control elements, and in a particularly preferred arrangement the side portion has one major recess for housing a control element of relatively large diameter (e.g. an armoured coaxial cable) and minor recesses for smaller elements (e.g. hydraulic control lines).

The said cross-section may be completely asymmetrical, for example by having a number of irregularly positioned side portions with recesses for housing control elements, but it is preferred that the body tubular structure has a single axis of symmetry. Where a number of side portions are provided, the said single axis of symmetry may pass between the side portions or through a side portion. However as has been mentioned, it is preferred that the body has a single side portion.

Thus in accordance with a preferred feature of the invention, the body has a single outwardly extending side portion and is adapted to be secured around a single flow pipe, the shape of the body being such that the general outline of the said cross-section has a single axis of symmetry passing through the said side portion of the body and through the said longitudinal axis of the body.

Most preferably in these circumstances the said cross-sectional outline of the body has a larger curved portion leading around the flow pipe in operation and a smaller curved portion leading around the said side portion. Conveniently the said cross-sectional outline is substantially eggshaped.

It is to be appreciated that the body may have minor projections or indentations, relating for example to a hinge and a split in the body, and then the term general outline refers to the overall envelope of the perimeter of the body. Preferably the said general outline is a smooth continuous outline. However the outline may include substantially straight portions, for example where the outline is said to be substantially egg-shaped, portions of the egg-shape may be flattened.

Preferably the body has an internal surface adapted to engage and seat against a flow pipe in operation, and in such an arrangement it is preferred that the said recess opens from the said internal surface. Preferably the said internally opening recess comprises a slot sufficiently deep, and appropriately shaped, to be such that when the locating device is secured about a flow tube, a control element located in the recess is gripped in a position such that the control element is spaced from the surface of the flow tube. Such an arrangement is advantageous in preventing or inhibiting contact of the control element with the flow tube thus preventing or reducing damage due to friction, impact, or corrosion by electrolytic action.

In accordance with a further aspect of the present invention there is provided a locating device for use within a tubular structure in a well bore, the device comprising a body adapted to be secured around a flow pipe with the pipe aligned along a longitudinal axis of the body, the body having an outwardly extending side portion which has a recess for housing a control element and for locating the control element relative to the flow pipe, the body having a shape such that the general outline of a cross-section of the body taken perpendicular to the said longitudinal axis is rendered asymmetrical by the said side portion of the body.

In accordance with another aspect of the present invention there is provided a locating device for use within a tubular structure in a well bore, the device comprising a body adapted to be secured around a single flow pipe of a well bore, the body having a single generally cylindrical major internal surface adapted to engage and seat against the flow pipe, the body having an outwardly extending side portion which has a recess for housing a control element and for locating the control element relative to the flow pipe, the body having a shape such that the general outline of a cross-section of the body taken perpendicular to the longitudinal axis of the said internal surface is asymmetrical about the said longitudinal axis.

In accordance with a yet further aspect of the invention, there is provided a locating device for use within a tubular structure in a well bore, the device comprising a body adapted to be secured around a flow pipe and having a generally cylindrical internal surface adapted to engage and seat against the flow pipe, the body having an outwardly extending side portion which has a recess opening from the said internal surface of the body for housing a control element and for locating the control element relative to the flow pipe, the body having a shape such that the general outline of a cross-section of the body taken perpendicular to the longitudinal axis of the said internal surface is asymmetrical about the said axis.

The feature of asymmetry of the locating device according to the invention results in a number of advantages of construction and operation of the locating device. For example with the feature of asymmetry set out above, it is possible to produce a locating device of improved strength relative to the amount of elastomeric material used in construction of the device. Also in embodiments where the cross-section is substantially egg-shaped, a smooth shape of cross-section can be obtained with consequent advantages in reduction of wear within the casing string of the well bore. In other preferred arrangements, where for example a heavy cable, and a pair of smaller hydraulic lines are to be located, these can be clustered together within a single body side portion, and the mass of elastomeric material forming the side portion can afford valuable protection to the group of control elements.Furthermore, it is possible to conventionally provide the required stand-off of the control elements from the flow pipe within the mass of elastomeric material providing the said side portion.

A further advantage of the asymmetrical arrangement described arises in operation of devices according to the invention, at least in accordance with preferred features thereof, in that where a series of asymmetrical locating devices are secured along a flow pipe in a casing, and are aligned in corresponding manner along the flow pipe, a bias is applied to the sense in which the cables and flow pipe arrange themselves in the casing. Where, as is common in wells such as North Sea oil wells, the bore or formation is not vertical, the use of asymmetrical locating devices can be arranged to locate the control elements on the upper side of the flow pipe within the casing. This has substantial advantages in that wear on the control elements is reduced, and twisting, whip and friction damage is reduced.This is particularly advantageous where steep angles of formation occur, for example upto 700 from the vertical.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figures 1 and 2 show perspective views of a locating device embodying the invention, the device being shown in open and closed positions respectively; Figure 3 is a diagrammatic plan view of the locating device shown in Figure 2; and Figures 4 and 5 show persepctive views of a steel core of the locating device shown in Figure 1.

In the Figures there is shown a locating device 11 embodying the invention which also serves the function of a pipe protector for a casing string in the bore of a well such as an oil well. As has been referred to hereinbefore, when a well bore is in production there is normally positioned within the well bore a casing string and within the casing string is positioned a hollow cylindrical flow pipe through which the oil or other product is pumped.

If the flow pipe were to remain free within the casing, the ensuing movement during pumping would cause severe wear of both the pipe and casing. It is therefore normal practice to provide pipe protectors secured around the flow pipe and made of rubber or other elastomeric material to protect the flow pipe from striking the side of the casing. It is also common practice to use such pipe protectors to locate within the space between the flow pipe and the casing control elements such as hydraulic control lines. In this embodiment of the invention there is provided a novel and advantageous construction of pipe protector which acts as a locating device. The protector will now be described in detail with reference to the drawings, but the general use of such protectors in well operations will not be described in detail, since such use is normal practice.

The locating device 11 comprises a body 1 2 comprising a mass of elastomeric material such as rubber in which is embedded a steel core shown at 13 in Figures 4 and 5. The body 12 is hinged about a hinge 14 and can be opened as shown in Figure 1 to allow the body 12 to be placed around a flow pipe (not shown). At the opening or split of the body 1 2 two sets of fingers 1 5 and 1 6 extend around the wall of the body, and when the body 12 is closed, the fingers 1 5 and 1 6 inter-digitate as shown in Figure 2. The fingers 1 5 and 16 are apertured at 17 to allow the body 12 to be tightened around a flow pipe by insertion of a wedge shaped pin 18 which is forced into position for example by striking with a hammer.As shown in Figures 4 and 5 the steel core 1 3 of the body 12 comprises an apertured framework which is hinged at 14 and which has securing loops 1 9 and 20 which are positioned around the apertures 1 7 in the fingers 1 5 and 1 6 in the completed product when the mass of elastomeric material is formed around the core 13.

When in the closed position shown in Figure 2, the body 12 forms an internal generally cylindrical surface 21 which is adapted to engage and seat around the flow pipe in operation. This generally cylindrical surface 21 defines a main longitudinal axis 22 of the body 12, as shown in Figure 3.

Figure 3 shows a cross-section of the body 12 perpendicular to the longitudinal axis 22, and as seen in the figures, the general outline of the cross-section shown in Figure 3 is rendered asymmetrical about the axis 22 by an outwardly extending side portion 23. The outline of the section shown in Figure 3 is asymmetrical to the extent of having only a single axis of symmetry, indicated at 24 in the plane of the section.

Positioned within the side portion 23 are three recesses 25, 26 and 27 each of which opens from the internal surface 21 of the body. The recesses 26 and 27 are of smaller cross-section than the recess 25, and the smaller recesses 26 and 27 are adapted to house and locate control elements such as hydraulic control lines indicated at 28 and 29 in Figure 1. The larger recess 25 is adapted to house and locate a control element of greater cross-section, such as an armoured coaxial cable (not shown).

Each of the smaller recesses 26 and 27 has a "key hole" cross-section such that the lines 28 and 29 can be snapped into the recesses 26 and 27 and be held in position by the resilience of the elastomeric material. The larger recess 25 has parallel sides leading to the internal surface 21, and in operation the coaxial cable (not shown) is slotted into position in the recess 25 but is not held there until the body 12 is tightened around the flow pipe by the tapered pin 18. During this tightening process the side walls 30 and 31 are squeezed inwardly and locate the cable in the recess 25 with a stand-off from the flow pipe.

As can be seen in Figure 3 the outline of the cross-section of the body 12 is generally egg shaped, and provides a smooth easily used shape providing minimum edges and recesses for causing wear. As shown the sides of the egg shape approaching the apex of the side portion 23 are flattened, as are the regions adjacent to the hinge 14 and fingers 1 5 and 16. However the overall outline is generally smooth and generally egg-shaped.

A first advantage which arises from the asymmetrical outline shown is that the control elements housed within the recesses 25, 26 and .27 are protected by a bulk of elastomeric material provided in the side portion 23 to give maximum strength with minimum bulk of the overall body 12. A second advantage that arises from the asymmetrical outline shown is that when a number of locating devices 11 are secured around a flow pipe with corresponding alignment, and the pipe is run in an inclined casing, for example inclined at 450 to the vertical, the pipe and control element assembly hangs with the control elements uppermost above the flow pipe. This arrangement minimises wear on the control elements, and can reduce vibratory and twisting movement of the assembly.

A further advantageous feature of the embodiment shown is that the internal surface 21 of the body 12, and the inner surface of the recess 25, include a number of slot-like recesses in the elastomeric material, aligned generally along the axis of the body. These slots 32 exert a gripping action on the flow pipe and on the coaxial cable in the recess 25, when the body 12 is tightened around the flow pipe.

By way of examples of dimensions which may be used for the locating device 11 shown in the Figures, the approximate diameter of the inner generally cylindrical surface 21 may be 5 2t1 when tightened into position on a flow pipe, and the thickness of the sleeve portion of the body 12 which encompasses the flow pipe, may be in the region of 3n. The overall depth of the body 1 2 taken at its widest point along the axis 24 may be in the region of 73411, and the thickness of the side portion wall 23 measured along the axis 24 may be in the region of -". The width of the larger recess 25 between its parallel walls 30 and 31 (before tightening on a flow pipe) may be 1" and the depth of the recess 25 may be slightly greater than 1". The diameter of the circular part of the smaller apertures 26 and 27 may be in the region of 111. The overall height of the body 12 along the direction of its longitudinal axis may be in the region of 6".

By way of example of materials which may be used, the elastomeric material may comprise rubber formed around the core 13 by being pumped into a mould and being cured under a pressure of 400 tons per square inch, the rubber being heated to 3500 over a period of about 12 minutes. Such a process produces a hardened rubber protector capable of protecting the control elements and the pipe, whilst allowing a degree of movement of the larger control element constituted by a coaxial control cable.

It is a preferred feature of a locating device embodying the invention that where a device includes an internal metal core such as the core 13 shown in Figures 4 and 5, the core shall have a cross-sectional shape which corresponds to the general asymmetrical outline of the body 12 in which the core is embedded. For example the core in Figure 5 preferably has an egg-shaped cross-section corresponding to the outline of the locating device, the lesser curved portion of the egg-shape being on the left in Figure 5 and the major curved portion of the egg-shape being on the right.

It will be appreciated that other outlines may be provided for the cross-section of the locating device body in accordance with the invention. For example the body 12 may be arranged to encompass two spaced apart flow pipes, so as to have two internal surfaces of the kind shown at 21 in Figure 2, whilst still having a single side portion of the kind shown at 23 resulting in the required asymmetrical outline.

Claims

1. A locating device for use within a tubular structure in a well bore, the device comprising a body adapted to be secured around a flow pipe with the pipe aligned along a longitudinal axis of the body, the body having an outwardly extending side portion which has a recess for housing a control element and for locating the control element relative to the flow pipe, the body having a shape such that the general outline of a crosssection of the body taken perpendicular to the said longitudinal axis is asymmetrical to the extent of having no more than one axis of symmetry in the plane of the cross-section.

2. A locating device according to Claim 1 in which the said body is adapted to be secured around a single flow pipe of a well bore, the body having a single generally cylindrical major internal surface adapted to engage and seat against the said flow pipe.

3. A locating device for use within a tubular structure in a well bore, the device comprising a body adapted to be secured around a single flow pipe of a well bore, the body having a single generally cylindrical major internal surface adapted to engage and seat against the said flow pipe, the body having an outwardly extending side portion which has a recess for housing a control element and for locating the control element relative to the flow pipe, the body having a shape such that the general outline of a cross-section of the body taken perpendicular to the longitudinal axis of the said internal surface is asymmetrical about the said longitudinal axis.

4. A locating device according to any preceding claim in which the body has a single outwardly extending side portion.

5. A locating device according to any preceding claim in which the shape of the body is such that said general outline of the said cross-section has a single axis of symmetry passing through the said side portion of the body and through the said longitudinal axis.

6. A locating device according to any preceding claim in which the said cross-sectional outline of the body has a larger curved portion leading around the flow pipe, in operation, and a smaller curved portion leading around the said side portion of the body.

7. A locating device according to any preceding claim in which the said cross-sectional outline is substantially egg-shaped.

8. A locating device according to claim 7 in which portions of the said egg-shape are flattened so that the outline includes substantially straight side portions.

9. A locating device according to any preceding claim in which the said body comprises a mass of elastomeric material.

10. A locating device according to any preceding claim in which the said body includes a reinforcing core embedded in the body, the core being such that the shape of a cross-section of the core taken perpendicular to the said longitudinal axis corresponds substantially to the shape of the said general cross-sectional outline of the body.

11. A locating device according to any preceding claim in which the body has an internal surface adapted to engage and seat against the flow pipe in operation, and in which the said recess opens from the said internal surface.

12. A locating device according to any preceding claim in which the said recess is such that a control element located in the recess in operation is gripped in a position such that the control element is spaced from the surface of the flow tube.

13. A locating device according to any preceding claim in which the said side portion has one major recess for housing a control element of relatively large diameter consisting of an armoured coaxial cable, and at least one minor recess for housing a control element of relatively small diameter consisting of a hydraulic control line.

14. A flow pipe located in a tubular structure in an inclined well bore by a plurality of locating devices each as claimed in any preceding claim, the locating devices being secured along the flow pipe with the asymmetrical outlines of the locating devices aligned in corresponding manner atong the flow pipe, the locating devices being such as to locate the said control element or elements on the upper side of the flow pipe within the tubular structure.

1 5. A locating device for use within a tubular structure in a well bore substantially as hereinbefore described with reference to the accompanying drawings.