WO2000004272A1

WO2000004272A1 - Drill string retrieving apparatus

Info

Publication number: WO2000004272A1
Application number: PCT/GB1999/002231
Authority: WO
Inventors: Robert Patrick Appleton
Original assignee: Appleton Robert P
Priority date: 1998-07-14
Filing date: 1999-07-12
Publication date: 2000-01-27
Also published as: GB2356656A; GB0100996D0; CA2342112A1; AU4919799A; GB9815131D0

Abstract

A tool (10) is provided for use in retrieving a drill string from a bore. The tool includes a body (12) which, in use, is suspended from a travelling block. A fluid inlet (16) communicates via a passage (18) with an outlet (20) in communication with a drill string (11). A coupling (22) is provided for selectively engaging the drill string (11). A one-way valve (26) is located in the passage (18) in order to regulate fluid flow through the passage (18). When fluid flow is interrupted, the normally closed valve (26) maintains fluid pressure on the coupling (22), so retaining the coupling (22) on the drill string (11).

Description

DRILL STRING RETRIEVING APPARATUS

This invention relates to a tool for use in tripping out drill string, and in particular to a tool for use in pumping-out drill string.

The drilling of a bore to, for example, access sub- surface hydrocarbon-bearing formations, is typically achieved using a drill bit mounted on the lower end of a hollow rotating drill string formed of drill pipe sections . During a drilling operation, drilling fluid, or "mud", is pumped from the surface through the drill string to lubricate and cool the bit and to carry cuttings out of the bore. The drill string may be rotated from the surface by a driven rotary table coupled to the string by a kelly. The rotary table defines a square or hexagonal central opening and the kelly, which extends through the opening, is of corresponding cross-section. The lower end of the kelly is connected to the upper end of the drill string and thus as the rotary table is driven its rotation is transferred via the kelly to the string. The upper end of the kelly, which is typically around 55 feet long, is suspended from a swivel having a bail supported on a hook on a travelling block. A fluid circulating hose carries mud from pumps to the upper end of the swivel, which comprises appropriate seals and bearings to allow mud to be pumped into the upper end of the rotating kelly, and then through the kelly into the drill string. During a drilling operation, sections of drill pipe, which are approximately 9 metres (30 feet) long, are added to the upper end of the drill string as the drill bit advances and the depth of the bore increases. Similarly, when retrieving the drill string, or "tripping out", drill pipe sections are removed from the upper end of the drill string as the string is lifted out of the bore.

Tripping out may simply consist of lifting the drill string and removing the uppermost length of drill pipe. However, in certain situations it is necessary or desirable to pump-out the drill string, that is to continue to pump drilling mud into the bore as the string is withdrawn. Most commonly, this is necessary to provide a positive pressure within the bore to prevent the bore wall from collapsing.

In a kelly-driven rig, as described above, mud is pumped through the kelly and into the drill string while the kelly is lifted using the block, until the lower end of the drill pipe length connected to the kelly is lifted through the rotating table and above the drilling floor. The upper end of the next section of drill pipe is secured at the rotary table using slips, to support the drill string. The mud pumps are then shut down and the drill pipe connection above the rotary table broken out, leaving a length of drill pipe suspended from the kelly. The kelly is then lowered to position the attached drill pipe section in a "mouse-hole" adjacent the rotary table, before being uncoupled from the drill pipe section and made-up to the next drill pipe section in the string, which now forms the upper end of the drill string. The mud pumps are then started again and the drill string lifted another 9 metres (30 feet) before repeating this process. Clearly, this is time-consuming, and pumping-out a drill string of any length will take a considerable time.

Savings in time may be achieved by using a top drive assembly to drive and support the drill string, rather than a kelly and rotary table, as this allows the drill string to be lengthened and shortened in 27 metre (90 feet) intervals equating to a drill stand made up of three drill pipe sections. However, many rigs are not equipped with top drives or may not be capable of accommodating a top drive, and there are a number of situations where it is necessary or desirable to utilise a kelly-driven rig.

It is among the objectives of embodiments of the present invention to provide a tool which facilitates the pumping-out of a drill string in a kelly-driven rig.

According to the present invention there is provided a tool for use in retrieving a tubular drill string from a bore, the tool comprising: a body for suspending from a support; a fluid inlet for communication with a fluid source; a fluid outlet for communication with a drill string bore; and a coupling which may be selectively actuated to engage a drill string.

The present invention also relates to a method of using such a tool.

In use, the tool and an elevator may be suspended in a rig from a travelling block, with the drill string suspended from the elevator and the tool connected to the tool joint above the elevator. Fluid is supplied to the tool and flows through the tool into the string and bore. The block is raised to lift a portion of the drill pipe string above the drill floor. The supply of fluid is interrupted and the string broken at an appropriate point above the drill floor, leaving one or more drill pipe lengths suspended from the elevator. The tool coupling is then disconnected from the drill pipe lengths. The tool may then be positioned and the coupling actuated to engage the upper end of the drill string. The supply of fluid through the tool and into the drill string then recommences, and the next section of string is lifted from the bore by the drill pipe elevator and block.

Preferably, the coupling is fluid actuated. Thus, the coupling may be actuated by the fluid being supplied via the tool to the drill string, such that no separate supply of power for the coupling is required. Most preferably, means is provided for maintaining the coupling in actuated configuration, and in engagement with the string, after the supply of fluid has been interrupted prior to breaking the string. Conveniently, said means is in the form of a one-way valve, which valve is preferably operator releasable to allow disengagement of the coupling. Preferably also, a valve is provided in the body for restricting or preventing passage of fluid to the fluid outlet until the supply fluid pressure has reached a predetermined level equal to or in excess of the pressure required to actuate the coupling. Accordingly, in use, fluid will not flow through the tool and into the drill string until the coupling has engaged the drill string. This feature simplifies the coupling operation, as an operator is only required to carry out the single task of turning on the mud pumps to achieve both the actuation of the coupling and the initiation of flow into the string. Of course this arrangement also simplifies the construction of the tool .

Preferably also, the coupling includes a fluid actuated sealing arrangement, for selectively providing a seal between the fluid outlet and the drill string.

Preferably also, the coupling includes a radially expandable segmented male portion, typically in the form of a threaded pin connection, for selective engagement with a corresponding female portion of a drill string. The male portion may be mounted on a resilient body itself mounted on a rigid support, and introduction of actuating fluid into a volume between the resilient body and the support causes radial expansion of the resilient body and corresponding radial expansion of the segmented male portion. The resilient body may extend beyond an end of the male portion so that the body may be expanded into sealing contact with the drill string female portion.

Preferably also, a pressure transmitting medium is provided between the fluid inlet and the coupling, most preferably the medium comprising a fluid, such as oil, isolated from the drilling fluid in the body, preferably by a piston. The piston may be biassed to release the coupling.

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 plan view of a pump-out tool in accordance with a preferred embodiment of the present invention;

Figure 2 is a sectional view on line A-A of Figure 1, the tool being illustrated in a first configuration; and

Figure 3 is a sectional view corresponding to Figure 2 and illustrating the tool in a second configuration.

The drawings illustrate a pump-out tool 10 in accordance with a preferred embodiment of the present invention. The tool is utilised in pumping-out a drill string, the upper end of which is indicated at 11; that is when a drill string 11 is tripped out of a bore while drilling fluid is being pumped into the bore to, for example, prevent collapse of the bore casing.

The tool 10 comprises a generally cylindrical body 12 which, in use, is suspended from a travelling block (not shown) . A circulating hose 14 is coupled to a fluid inlet 16 of a passage 18 extending through the body 12 to an outlet 20 in communication with the upper end a drill pipe section forming the upper end of a drill string 11. A threaded pin coupling 22 is provided on the lower end of the body 12 for selectively engaging a corresponding box coupling 24 as provided on the drill pipe section, as will be described. Located in the passage 18 is a normally-closed valve

26 which is spring-biassed to prevent flow through the passage 18. The valve 26 comprises a two-part sleeve 28, the lower end of the sleeve being cut-away to define flow passages 30. Mounted to the lower end of the sleeve 28 is a valve closure 32 accommodating a one-way valve 34, which permits restricted upward flow. The closure 32 comprises a central part 36 accommodating the valve 34 and having a rounded upper face and an annular outer part 38 defining a ledge 40. With the valve 26 in the closed position, as illustrated in Figure 3, the ledge 40 engages a corresponding face 42 defined by a seat 44 mounted on the wall of the passage 18. The seat 44 sits on a ledge 46 and has an upper face 48 supporting a coil spring 50, the upper end of which engages an opposing face 52 defined by the upper part: of the sleeve 28. Normally, the spring 50 extends to lift the sleeve 28 upwardly in the passage 18 such that the closure 32 engages the seat 44. However, the spring racing is selected such that a pressure differential of 10,000 psi across the closure 32 provides sufficient force to compresses the spring 50 and open the valve 26.

The upper end of the body accommodates two cylinders 54, 55 accommodating respective pistons 56, 57. The upper ends of the cylinders 54, 55 are closed by threaded plugs 58, 59 each defining a port 61 in communication with a respective fluid line (not shown) leading to a one-way valve 60 which is located in a V-shaped cut-out 63 in the upper end of the body 12. The valve 60 permits flow of fluid from the upper part of the passage 18, through fluid port 62, to the cylinders 54, 55, and prevents flow in the opposite direction. However, the valve 60 may be released by an operator to permit flow from the cylinders 54, 55 into the passage 18. The pistons 56, 57 are biassed upwardly by respective coil springs 64, 65 and serve to contain a hydraulic oil reservoir utilised in actuating the coupling 22, as will be described. Oil flow channels 66, 67 lead from the lower end of each cylinder 54, 55 to the lower end of the passage 18. The channels 66, 67 open into the passage 18 at an annular oil relief groove 68 defined in an outer face of a wash-pipe 70 forming part of the coupling 22.

The wash pipe 70 defines a central through bore 72 having a flared upper end which opens into a part-spherical intermediate portion of the passage 18. The larger diameter upper end of the wash-pipe 70 is threaded and engages a corresponding thread provided in the passage wall. Mounted on the wash pipe 70 is a sectioned pin connection 74 defining an external thread. The pin connection is divided axially into four parts and is coupled to the wash pipe 70 by a rubber sleeve 76 which extends above and below the connection 74. The wash pipe 70, connection 74 and sleeve 76 are formed as an integral unit, by moulding the rubber sleeve 76 between the pipe 70 and connection 74. Prior to introducing of the flowable moulding material, a release material is applied to a portion of the surface of the wash pipe 78 such that the rubber will not bond to the surface 78. Accordingly, fluid may be pushed, through oil flow channel 80 leading from the relief groove 68, into a volume 82 between the wash pipe 70 and sleeve 76, to "inflate" the sleeve 76, and radially extend the connection 74, as illustrated in Figure 2. The wash pipe assembly is locked to the body 12 by a threaded collar 84 defining a ledge for supporting a flange 86 on the upper end of the connection 74.

In use, the body will be suspended from a travelling block with the circulating hose 14 connected to the fluid inlet 12. The coupling 22 is positioned in the box connection 24 of the upper end of a drill string 11 supported in the drilling floor by appropriate slips. The rig mud pumps are turned on and drilling mud flows into the upper end of the passage 18, which is initially closed by the valve 26. The mud flows, via the port 62 and the oneway valve 60, into the cylinders 54, 55 and, as the mud pressure rises, the pistons 56, 57 are pushed downwardly in the cylinders 54, 55, displacing the oil below the pistons 56, 57 through the oil flow channels 66, 67, 80 into the volume 82 between the wash pipe 70 and the rubber sleeve 76. The expanding volume 82 pushes the segments of the connection 74 radially outwardly and into engagement with the box connection 24. As the mud pressure rises further, the valve 26 is opened and permits mud to flow through the body passage 18 and down through the drill string. The slips are then released and the tool 10 is raised by the block and drill string elevator, to lift the drill string and draw a section of drill pipe through the drill floor. The slips are then set again, to support the drill string from the drill floor. The mud pumps are shut down and the string broken adjacent the drill floor; any excess pressure in the string bore is relieved through the valve 34 in the valve closure 32. One or more drill pipe lengths are then left suspended from the drill pipe elevator, at this stage the one-way valve 60 preventing release of the fluid pressure- actuated coupling 22 providing the fluid tight connection between the tool 10 and the string. The block and elevator are then lowered to locate the drill pipe lengths in the mouse hole in the drill floor. To disconnect the drill pipe 11 from the coupling 22, the one-way valve 60 is released by an operator, allowing the springs 64, 65 to lift the pistons 56, 57 and displace the drilling fluid from the cylinders 54, 55. The upward movement of the pistons 56, 57 draws the oil from the volume 82, "deflating" the rubber sleeve 76 and retracting the segments of the connection 74. Once the elevator is uncoupled from the drill pipe, the tool 10 is lifted clear of the drill pipe and the connection 74 positioned in the box of the drill pipe length forming the upper part of the drill string, and the process repeated. The invention is particularly suited for use in kelly- driven rigs, and the relative ease of making-up and breaking connections between the tool and the drill pipe, and the ability to omit the kelly, allow a drill string to be pumped-out of a bore relatively quickly and easily.

The description above refers to drilling fluid and drilling mud, and those of skill in the art will understand that these terms are not intended to limit the fluids which may be utilised in the operation of the tool 10. Also, it will be apparent from an examination of the accompanying drawings that, in the interests of brevity, the provision and location of various seals and other minor parts of the tool 10 have not been described in detail, on the basis that these features will be readily apparent to the person of skill in the art.

It will also 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 present invention.

Claims

1. A tool for use in retrieving a tubular drill string from a bore, the tool comprising: a body for suspending from a support; a fluid inlet for communication with a fluid source; a fluid outlet for communication with a drill string bore ; and a coupling which may be selectively actuated to engage a drill string.

2. The tool of claim 1 wherein said coupling is fluid actuated.

3. The tool of claim 2 further comprising means for maintaining said coupling in an actuated configuration when no supply of fluid is provided.

4. The total of claim 3 wherein said maintaining means comprises a one-way valve.

5. The tool of either of claims 3 or 4 wherein said maintaining means is releasable.

6. The tool of any one of claims 2 to 5 wherein a valve is provided in said body for restricting or preventing passage of fluid to said fluid outlet until the supply fluid pressure has reached a predetermined level equal to or in excess of the pressure required to actuate said coupling .

7. The tool of any preceding claim wherein said coupling includes a fluid actuated sealing arrangement for selectively providing a seal between said fluid outlet and the drill string.

8. The tool of any preceding claim wherein said coupling includes a radially expandable segmented male portion for selective engagement with a corresponding female portion of a drill string.

9. The tool of claim 8 wherein said male portion comprises a threaded pin connection.

10. The tool of either of claims 8 or 9 wherein said male portion is mounted on a resilient body mounted on a rigid support .

11. The tool of claim 10 wherein a volume is defined between the resilient body and the rigid support and introduction of actuating fluid into said volume causes radial expansion of the resilient body and corresponding radial expansion of the segmented male portion.

12. The tool of either of claims 10 or 11 wherein said resilient body extends beyond an end of the male portion so that the body may be expanded into sealing contact with the drill string female portion.

13. The tool of any preceding claim wherein a pressure transmitting medium is provided between the fluid inlet and the coupling.

14. The tool of claim 13 wherein said medium comprises a fluid isolated from the drilling fluid in the body.

15. The tool of claim 14 wherein said fluid is oil.

16. The tool of either of claims 14 or 15 wherein said fluid is isolated from the drilling fluid in the body by a piston.

17. The tool of claim 16 wherein said piston is biassed to release the coupling.

18. A method of retrieving a tubular drill string from a bore, the method comprising the steps of: suspending a tool according to any of claims 1 to 17 and an elevator in a rig from a travelling block, with a drill string suspended from the elevator; supplying fluid to the tool; raising the block to lift a portion of the drill pipe string above the drill floor; interrupting the supply of fluid; breaking the string; disconnecting the tool coupling from the drill pipe; repositioning the tool; and actuating the coupling to engage the upper end of the drill string.