GB2302076A - Tube gripping and translating apparatus - Google Patents

Abstract

Apparatus for translating a tubular member, such as coil tubing 36, includes four clamp segments 34 for engaging radially respective circumferentially spaced areas of the outer surface of the tubing 36. Respective piston and cylinder arrangements 52,54 are provided for moving the clamp segments 34 and hence the tubing 36 engaged thereby longitudinally of the tubing.

Description

CONVEYING APPARATUS This invention relates to a conveying apparatus, and in particular to apparatus for conveying a tubular member, such as coil tubing.

In the oil and gas exploration and extraction industries various forms of tubes, such as coil tubing, and cables, such as wireline, are utilised for positioning tools, instruments, motors and the like within drilled bores. Coil tubing is small diameter (0.75 - 3.5 inches) tubing which is sufficiently flexible for the tubing to be coiled onto a drum to form a tube reel. Coil tubing is thus relatively easy to store and transport, and may be provided in long sections (typically 20,000 feet) such that the tubing may be deployed relatively quickly. The apparatus used in the deployment of coil tubing is generally referred to as a coil tubing unit, and comprises a tube reel, a power pack, an operator cabin, and an injector head. The power pack typically comprises a diesel motor which is used to operate a hydraulic pump.The motor, pump and other functions of the unit are controlled from the operator cabin. Conventional injector heads include a chain drive arrangement which acts as a tube conveyor. Two loops of chain are provided, the chains carrying semi-annular blocks which grip the tube walls.

The chains are mounted on sprockets driven by hydraulic motors, using fluid supplied from the power pack. Such coil tubing units have been in use for many years, however the applicant has identified a number of problems associated with the existing apparatus. The force which must be applied to the tubing by the injector head may be considerable, and this requires that the tubing is clamped tightly between the blocks carried by the driven chains.

This can result in deformation or ellipsing of the tubing.

In all but the most extreme cases the deformation will be elastic, such that the tubing returns to its original circular form on passing from the injector head, however the deformation is thought to shorten the useful life of the tubing such that it must be replaced relatively frequently, and at great expense. Further, the apparatus operates in difficult conditions, and the injector head is continually exposed to a variety of fluids carrying fine sand and grit which result in rapid wear of the drive chains, such that they require frequent replacement.

It is among the objects of the aspects of the present invention to obviate or mitigate these disadvantages.

According to the present invention there is provided apparatus for conveying a tubular member, the apparatus comprising: three or more clamping members for selectively engaging respective circumferentially spaced areas of the outer surface of a tubular member; and translation means for moving the clamping members and the tubular member engaged thereby.

The tubular member may be coil tubing or some other relatively thin walled tube, and the provision of three or more clamping members minimises the deformation of the tubing when gripped by the members and avoids the ellipsing of the tubing experience in conventional coil tubing injectors having opposing pairs of clamping blocks. It is thus possible to grip the tubing more tightly. The ability to engage the tubing with a greater force also reduces the length of the tubing which must be gripped, and allows use of shorter injectors. Preferably, four clamping members are provided.

Preferably also, the translation means is moveable in a reciprocal manner and include means for actuating the clamping members when moving in a tubular member feed direction and retracting the clamping members when moving in the other direction. Most preferably, the translation means is fluid actuated, and conveniently includes a piston and cylinder arrangement. Such an arrangement allows for accurate determination of the length of tubing deployed or taken in, simply by multiplying the number of strokes of the translation means by the length of the stroke.

Accordingly, the apparatus may include means for recording the number of strokes of the translation means and providing an indication of the length of tubing this represents.

Preferably also, the means for actuating the clamping members is fluid actuated, conveniently by a piston and cylinder arrangement. The clamping members may be in the form of segments linked by respective piston and cylinders which, when actuated, bring the clamping members together to grip the tubing. The segments may be loosely mounted on respective piston and cylinders for providing axial movement of the tubing, and in the preferred arrangement each segment is mounted on a respective cylinder.

Where a reciprocal translation means is provided, it is preferable that at least two sets of clamping members and associated translation means are provided, to permit continuous movement of the tubular member. Most preferably, the actuated phases of the two sets of clamping members overlap, such that the tubing is always gripped by at least one set of clamping members.

Preferably also, the apparatus includes a fluid pump, typically a hydraulic pump, for actuating the translation means. Most preferably, the pump is driven by an electric motor. In a coil tubing injector, or other application in which the apparatus operates in a potentially hazardous environment, this allows the motor to be located directly adjacent the wellhead where the injector is to be used.

The motor, pump, translation means and clamping members may thus be accommodated within a compact and easily transportable housing or frame. This contrasts with conventional diesel motor powered systems, in which the motor and the associated hydraulic pump must be spaced from the wellhead and a system of hydraulic hoses is required to link the pump to the translation means. Clearly, such hoses present a potential tripping hazard to workers in the area, decrease efficiency, increase costs and are vulnerable to damage.

According to a further aspect of the present invention there is provided apparatus for conveying a tubular member, the apparatus comprising a body member supporting: clamping members for selectively engaging the outer surface of a tubular member; fluid actuated translation means for moving the clamping members and the tubular member engaged thereby; a fluid pump; and an electric motor for driving the pump.

According to another aspect of the present invention there is provided apparatus for conveying a tubular member, the apparatus comprising: clamping members for selectively engaging the outer surface of a tubular member; and fluid actuated translation means for moving the clamping members and the tubular member engaged thereby, the translation means including a piston and cylinder arrangement.

These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a coil tubing unit including apparatus for conveying a tubular member in accordance with a preferred embodiment of the present invention; Figure 2 is a plan view of the coil tubing unit of Figure 1; Figure 3 is a sectional view on line 3 - 3 of Figure 1 showing the clamping member of the injector head; Figure 4 is a side view of the clamping member of Figure 3; Figure 5 is an enlarged sectional view on line 5-5 of Figure 3, of the area 5 of Figure 4; and Figure 6 is a series of views showing the operation of the injector head of the unit of Figure 1.

Reference is first made to Figures 1 and 2 of the drawings, which illustrate a coil tubing unit including apparatus for conveying a tubular member, in the form of an injector head, in accordance with a preferred embodiment of the present invention. The coil tubing unit is shown on the surface above a land-based well, the top of the well bore being fitted with a blow-out preventer stack 10.

Mounted over the stack 10 is a telescopic leg frame 12 which provides mounting for a coil tubing injector head 14 and an electro-hydraulic power unit 16. The injector head 14 is mounted on the frame via a sub fame as is known in the art, such that the pulling force or weight applied to or by the coil tubing may be determined by measurement of the reaction forces between the head 14 and frame 12. The frame 12 also provides mounting for various auxiliary equipment, including a hydraulic fluid tank 18, a hydraulic fluid cooler 20, and a control box 22. Mounted on the upper portion of the frame 12 is a goose neck 24 which guides coil tubing between the injector head 14 and a coil tubing reel 26 provided with an appropriate spooling device 28.

Operation of the injector head 14 is controlled from a cabin 30 for accommodating the coil tubing operator.

The power unit 16 includes an electric motor and a hydraulic pump, such that the only external connections from the power unit 16 are the electrical supply lines and lines for carrying control signals to and from the cabin 30. As will be described, the injector head 14 is hydraulically powered, and only short lengths of hydraulic hose have to be provided between the power unit 16 and the injector head 14. This contrasts sharply with conventional coil tubing units which utilise diesel power packs and for safety reasons must be located remotely from the wellhead, such that it is necessary to provide hydraulic hoses for extending across the work site between the power pack and the injector head.

The injector head 14 comprises two sets of four hydraulic cylinders 32, 33 each of which carries a clamp comprising four clamp segments 34, 35, the upper set of segments 34a-d being shown in Figures 3 and 4 of the drawings. The clamp segments 34 are arranged to grip a section of coil tubing 36 and are actuated to grip the tubing 36 by hydraulic fluid pressure, as will be described. Each clamp segment 34 is triangular and carries a tube gripping portion 40 of a suitable hardwearing material. Each clamp segment 34 is connected to an adjacent segment by five pins 42, each pin forming the piston rod of a hydraulic piston and cylinder arrangement 44. One end of each pin 42 is fixed in a clamp segment 34a while the other end carrying the piston 46 is movable in a cylinder 48 defined by the adjacent clamp segment 34b.

Actuation of the arrangement 44, by introduction of pressurised hydraulic fluid, brings the clamp segments 34a,b closer together, thus gripping the coil tubing 36.

On release of the hydraulic fluid pressure, a spring 50 within each cylinder 48 moves the clamp segments apart, releasing the tubing 36.

The clamp segments 34 are hollowed to accommodate a respective hydraulic cylinder 52, forming part of the set of cylinders 32 for producing longitudinal or axial movement of the tubing 36. Each cylinder 52 is mounted on a respective piston rod 54 which extends from the segment 34.

As described above, the clamp segments 34 move relative to one another as the tubing is gripped and released. This requires that the clamp segments 34 are laterally or transversely movable relative to the cylinders 52, and this is achieved by locating the cylinders 52 in segment bores 56 which are of larger diameter than the cylinders 52. Relative axial movement is prevented by providing a flange 58 on each cylinder (see Figure 5) and retaining the flange 58 in a slot 60 defined in the lower face of the clamp segment using a threaded ring 62.

The two sets of hydraulic cylinders 32, 33 and the respective clamps 34, 35 operate in conjunction to move the tubing 36 smoothly through the injector head 14, as will now be described with reference to Figure 4 of the drawings.

Figure 4 illustrates a sequence in which the coil tubing 36 is being pulled upwardly from the bore.

Initially, as illustrated in Figure 4a, the clamp segments 34, 35 carried by the upper and lower sets of cylinders 32, 33 are moved together to grip the tube by supplying pressurised fluid to the cylinders 48. However, as the lower set of cylinders 33 reach the upper limit of their travel the bottom set of clamp segments 35 are released, while the upper set of segments 34 remain engaged with the tubing and are carried upwards by the upper set of hydraulic cylinders 32 (Figure 4b). As the upper set of cylinders 32 reaches the upper limit of their travel (Figure 4c) the lower set of cylinders 33 have returned the segments 35 to the lower limit of travel, where the segments 35 are actuated to grip the tubing. Thus, for a short time the tubing is again gripped by both clamps 34, 35 (Figure 4d).The upper clamps 34 then release the tubing and are moved downwardly over the tubing, while the lower set of clamps 35 moves upwardly in engagement with the tubing 36 (Figure 4c). The tubing 36 is then "passed" from the lower clamps 35 to the upper clamps 34, and the cycle repeated. Thus, by appropriate control of the supply of hydraulic fluid to the sets of cylinders 32, 34 and the clamp cylinders 48 it is possible to move the coil tubing 36 smoothly and securely through the injector head 14 at constant speed even when the pulling force or weight on the tubing varies.

The injector head 14 as described above offers a number of advantages over existing injector head arrangements, the use of a reciprocating stroke type injector allowing the length of tubing 36 which has been taken in or deployed to be measured accurately simply by a stroke count. The speed of tubing deployment or take in may also be accurately controlled, typically at between 0.1 and 50 metres per minute. Further, the pulling force applied to the tubing may be easily and automatically controlled by adjustment of the hydraulic fluid pressure supplied to the cylinder sets 32, 34. In addition, the pressures of the respective hydraulic fluid supplies to the clamp segment cylinders 48 and the hydraulic cylinder sets 32, 34 are linked such that a higher pulling force is provided in combination with a higher clamping force. This permits the clamping force to be varied as necessary rather than remain constant, and relatively high, as in existing arrangements, with the result that the average clamping force applied to the tubing is reduced, thus further extending the working life of the tubing. The provision of four clamp segments 34, 35 in each cylinder set 32, 34, ensures that the tubing 36 is securely gripped without ellipsing of the tubing. Further, the cylinders 32, 33 may be readily sealed against ingress of contaminants, such that maintenance is minimal compared to conventional chain driven injectors.

It will be clear to those of skill in the art that the above-described embodiment is merely exemplary of the present invention, and that various modifications and improvements may be made thereto without departing from the scope of the invention.

Claims (20)

1. Apparatus for conveying a tubular member, the apparatus comprising: three or more clamping members for selectively engaging respective circumferentially spaced areas of the outer surface of a tubular member; and translation means for moving the clamping members and the tubular member engaged thereby.

2. The apparatus of claim 1, wherein four clamping members are provided.

3. The apparatus of claim 1 or 2, wherein the translation means is moveable in a reciprocal manner and includes means for actuating the clamping members when moving in a tubular member feed direction and for retracting the clamping members when moving in the other direction.

4. The apparatus of any of the preceding claims wherein the translation means is fluid actuated.

5. The apparatus of claim 4, wherein the translation means includes a piston and cylinder arrangement.

6. The apparatus of claim 5 including means for recording the number of strokes of the translation means and providing an indication of the length of tubing this represents.

7. The apparatus of any of the preceding claim including means for actuating the clamping members, said means being fluid actuated.

8. The apparatus of claim 7, wherein said clamping member actuating means includes a piston and cylinder arrangement.

9. The apparatus of claim 8, wherein the clamping members are in the form of segments linked by respective piston and cylinders which, when actuated, bring the clamping members together to grip the tubing.

10. The apparatus of any of the preceding claims, wherein the clamping members are loosely mounted on respective axially arranged piston and cylinders for providing axial movement of the tubing.

11. The apparatus of claim 10, wherein each segment is mounted on a respective axial cylinder.

12. The apparatus of any of the preceding claims wherein at least two sets of clamping members and associated reciprocal translation means are provided, to permit continuous movement of the tubular member.

13. The apparatus of claim 12, wherein the actuated phases of the two sets of clamping members overlap, such that the tubing is always gripped by at least one set of clamping members.

14. The apparatus of any of the preceding claims, wherein the apparatus includes a fluid pump for actuating the translation means.

15. The apparatus of claim 14, wherein the pump is driven by an electric motor.

16. The apparatus of claim 15, wherein the motor1 pump, translation means and clamping members are accommodated within a transportable housing or frame.

17. Apparatus for conveying a tubular member, the apparatus comprising a body member supporting: clamping members for selectively engaging the outer surface of a tubular member; fluid actuated translation means for moving the clamping members and the tubular member engaged thereby; a fluid pump operatively associated with the translation means; and an electric motor for driving the pump.

18. Apparatus for conveying a tubular member, the apparatus comprising: clamping members for selectively engaging the outer surface of a tubular member; and fluid actuated translation means for moving the clamping members and the tubular member engaged thereby, the translation means including a piston and cylinder arrangement.

19. A method of conveying coil tubing, the method comprising the steps: gripping respective areas of the outer surface of a length of coil tubing with three or more circumferentially spaced clamping members; and moving the clamping members and the coil tubing engaged thereby to advance the coil tubing.

20. The apparatus for conveying a tubular member substantially as described herein and as illustrated in the accompanying drawings.