GB2274321A - Reaming tool for cleaning pipes - Google Patents

Abstract

A tubing and profile reaming tool has a plurality of dogs (10). These are movable between a retracted and an extended position. Movement is caused by a sliding member (8, 24) within the tool provided with cam surfaces 32 which upon axial displacement push the dogs outwards against springs 36. Movement of the sliding member is controlled by differential pressure as a result of fluid flow through the axial passage 9. It is returned to its original position in which the dogs are retracted when the pressure differential is removed. The tool is intended for use in conjunction with a fluid turbine motor in an oil production facility. <IMAGE>

Description

TUBING AND PROFILE REAMING TOOL This invention relates to a tubing and profile reaming tool of the type used to clean scale build up in pipes and flexible tubes in, for example, oil production facilities.

In oil production facilities production materials such as barium sulphate and strontium sulphate can become baked onto the inside of pipes and tubing. This happens particularly under severe operating conditions such as high pressures and temperatures. The build up of materials on the inside of pipes and tubings can reduce their total inside diameters by up to 25%. This is equivalent to a 50% reduction in cross-sectional area and consequently results in a severe reduction in the throughput for that piece of pipe or tubing.

Tubing and profile reaming tools are known which comprise a cylinder with a smaller diameter than the tube which it is desired to ream. The cylinder is provided with a plurality of cutting teeth or "dogs" on its outer surface. The tool is fed into a pipe or piece of tubing on coiled tubing using a downhole motor capable of rotating the tool remotely from the surface. When the tool is rotated the dogs cut into the scale which has built up on the inside of the tubing and thus clean the pipe.

The use of such a tool with fixed dogs is somewhat limited in that a different tool is needed for each diameter of tubing which it is desired to ream. Furthermore, it is not possible for the tool to pass through constrictions in the tubing of the type which are caused by ball valves and the like and thus in some cases it is necessary to disassemble the pipework to be cleaned prior to using the tool.

In accordance with the present invention there is provided a tubing and profile reaming tool having retractable dogs.

This and other aspects of the invention are defined in the appended claims to which reference should now be made.

A preferred embodiment of the invention will now be described in detail by way of example with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a tubing and profile reaming tool embodying the invention; Figure 2 shows a cross section through the tool of figure 1 with the dogs in the retracted position; and Figure 3 shows the cross-section of figure 2 with the dogs in the extended position.

The tubing and profile reaming tool shown in figure 1 comprises a cylinder formed from upper and lower sections 2 and 4. The section 4 has a tapered end section 6 secured to it at the end of the tool remote from any connection to a motor for driving the tool. Such a connection is made to section 2.

The tool is preferably designed for use with a fluid turbine type motor to rotate the tool in a tube. Such a motor would be fixed to the end of the tube section 2 and to a coiled tube leading to the surface. Fluid is then pumped in to the coiled tube. The fluid passes through the motor and turns the turbine thus causing the tool to rotate.

Emerging from the tapered section 6 of the tool is a further cylindrical section 8 which extends through the tool along the length of section 4 and partially into section 2. This section 8 slides axially within the cylinder under hydraulic pressure to extend and retract dogs 10 of which three are arranged around the tool. In figure 1 the dogs are shown in their extended positions.

The dogs are formed from hardened metal and each has two cuttings surfaces 12 and 14 for reaming deposits on the inside of pipes and tubing. They are arranged to have the same diameter as the internal diameter of the tube to be reamed.

Internal detail of the tool of figure 1 is shown in figures 2 and 3. In figure 2 the dogs 10 are in their retracted positions.

The lower section 4 of the tool in figure 2 has a reduced diameter portion 16 over which the upper section 2 fits. This reduced diameter portion 16 is terminated by a flat annular surface 18.

The sliding section 8 is retained and slides within the internal diameter of the reduced diameter section 16 and is a close fit therein. The upper end of the sliding section 8 is terminated by a threaded portion 20 to which a cap 22 is attached. The sliding section 8 and cap 22 form a slidable mandrel within the tool. The cap has an end portion 24 of which the outer diameter corresponds to the internal diameter of the upper section 2 and slides therein.

This section 24 is terminated by a flat annular surface 26 which faces the flat annular surface 18 of the reduced diameter section 16 of the lower portion 4. These flat annular surfaces form a stop to limit the downward movement of the sliding section 8.

Below the reduced diameter section 16 of the lower section 4 slots 28 are provided through which dogs 10 may be extended and retracted. In this particular example there are three dogs spaced equiangularly around the tool of which one can be seen in the cross-section. Each dog is provided with two internal camming surfaces 30 which, with the sliding section 8 in the position shown in figure 2, lie against corresponding camming surfaces 32 formed by bulges 34 in the sliding section 8. The camming surfaces 30 of the dogs are urged towards the surfaces 32 by a pair of clip or garter springs 36 which are linked around the ends of the dogs.

Thus when the sliding section 8 is in the position of figure 2 the dogs are retracted by the springs 36.

At the lower end of the tool the tapered section 6 is coupled into the lower section 4 by threaded portions 38 and 39. The sliding section 8 passes through a close fitting sleeve portion 40 of the end of the tapered section 6. An annular gap 42 is formed between the internal diameter of the threaded section 38 and the sliding section 8 and this retains a coil spring 44 which at one end bears against an annular surface 46 in the lower section 6 and at the other end against a flange 48 provided on the sliding section 8.

Thus the spring 44 acts to urge the sliding section 8 to the position shown in figure 2 and thus enables the springs 36 to act against the dogs and to retract them.

Further upward movement of the sliding section 8 is prevented by the upper surface of flange 48 abutting against a ring 50 which is fitted on a shoulder 52 at the end of the threaded hole 39 in the lower section 4. Thus there are stops to limit upward and downward movement of the sliding section 8.

The sliding section 8 and cap 22 have an axial passage 9 open at both ends. The upper section 2 also has an axial passage 11 which is in communication with the passage 9 end opens at the upper end of the tool. Thus there is an axial passage through the tool.

In use, when the tool is connected below a fluid turbine, fluid emerging from the turbine flows into the passage 11 and then into the passage 9 and emerges through the lower end of section 8. The motor and tool assembly are usually positioned at the end of a work string and fluid is pumped down the tube in which they are positioned. This fluid flow causes the motor and tool to rotate.

A fluid flow of 120 gallons pers minute is typical but this will vary according to tool size and desired cutting speed.

The cap section 22 of the mandrel comprises a series of restrictions 50 in the passage 9. Thus fluid flowing down the tool passes from passage 11 into passage 9 and into a restricted cross-sectional area. The effect of this is to accelerate the fluid flow in passage 9 in comparison to the flow rate in passage 11. This results in a lower pressure acting upwards on the sliding section 8 of the tool than is acting downwards on the cap 22, i.e.

a pressure differential is established across the mandrel. This causes the mandrel to slide downwards in the tool to the position shown in Figure 3 in which the dogs have been extended from the tool In Figure 3 the differential pressure applied across mandrel has caused downward movement until the annular surface 26 provided on the cap 22 abuts the annular surface 18 provided on the reduced diameter portion 16 of the lower section 4. Thus no further downward movement of the sliding section 8 is possible.

The effect of this downward movement is to move the bulges 34 downward in the tool and thus forcing the camming surfaces 32 to work against the camming surfaces 30 on the dogs. Thus the dogs 10 are forced, by the camming action, to move outwardly through the slots 28 in which they are retained and to act against the springs 36 clipped around their ends.

When the reaming operation has been performed the pumping of the fluid into the tube stops. This removes the differential pressure across the mandrel and enables the compression spring 44 to force it upwards to the position shown in figure 2. As it slides upwards the springs 36 act on the dogs and retract them so that the tool can be removed from the tube it has reamed.

The retractable dogs enable the tool to be moved easily through a tube to the portion to be reamed. The tool may pass through constrictions such as ball valves with the dogs retracted.

The dogs are interchangeable and by substituting alternative dogs operations such as internal tube polishing and internal tube cutting may be performed.

The pressure differential can be maintained across the mandrel for lower fluid flow rates by fitting an orifice plate into the bottom of the sliding section 8. This section 8 is internally threaded to facilitate this. Different sizes of orifice are selected for different flow rates.

Claims (12)

1. A tubing and profile reaming tool comprising a plurality of dogs movable between a retracted first position and an extended second position.

2. A tubing and profile reaming tool according to claim 1 comprising means for moving the dogs from the first to the second position in response to fluid flowing through a passage leading from one end of the tool to the other.

3. A tubing and profile reaming tool according to claim 2 in which the moving means comprises a mandrel slidable within the tool between first and second positions and through which the passage passes, the mandrel carrying camming means which act upon the dogs as the mandrel moves from the first to the second position thereby moving the dogs from the retracted to the extended position.

4. A tubing and profile reaming tool according to claim 3 in which the mandrel includes a restriction in the passage cross-sectional area.

5. A tubing and profile reaming tool according to claim 4 in which the restriction comprises a series of steps whereby the passage is reduced in cross-sectional area towards the bottom of the tool.

6. A tubing and profile reaming tool according to claim 4 in which the restriction comprises an orifice plate fitted into the passage passing through the mandrel.

7. A tubing and profile reaming tool according to claim 3, 4, 5 or 6 including means for urging the mandrel towards the first position.

8. A tubing and profile reaming tool according to claim 7 in which the urging means comprise a coil spring acting on the mandrel.

9. A tubing and profile reaming tool according to any preceding claim including means for urging the dogs towards the retracted position.

10. A tubing and profile reaming tool according to claim 9 in which the urging means comprise circular springs positioned around ends of the dogs.

11. A tubing and profile reaming tool according to any preceding claim in which the dogs are interchangeable.

12. A tubing and profile reaming tool substantially as herein described with reference to the accompanying drawings.