Drilling Expansion Joint Apparatus

Abstract

In accordance with an illustrative embodiment of the present invention, a slip or expansion joint for use in a drill string includes a mandrel telescopically disposed within a housing with splines to prevent relative rotation. The housing includes a bottom sub having attached thereto a tube extending upwardly in spaced relation to the adjacent housing section to provide an annular cavity that is placed in communication with the well annulus by ports. A seal assembly is mounted on the upper end of the tube and seals against the lower portion of said mandrel which is slidably received in said tube.

Description

This invention relates generally to well tools and more particularly to an expansion joint used in the drill string when drilling offshore wells from a floating drilling vessel.

While drilling a well, it is highly desirable to maintain a substantially constant weight on the bit to control bit wear and hole direction. For land based wells the control of weight on the bit is fairly straightforward, however the drilling of offshore wells from a floating vessel encounters special problems due to the fact that the vessel, and consequently the derrick and draw works, is constantly moving vertically with respect to the bottom of the hole. Accordingly it has become a typical practice to include a slip or expansion joint in the drill string usually between the drill pipe and the drill collars, and to close the joint to a partially contracted position so that it may telescope freely as the vessel and drill pipe move vertically. This leaves the weight of the drill collars at all times on the bit.

Prior art expansion joints have not been satisfactory due primarily to their inability to withstand wear on the seal surfaces and seal elements caused during constant relative motion between the expansion joint members within the drilling fluids which contain sand particles, cuttings and other debris. This problem is particularly acute in some prior devices that are so constructed and arranged that debris can settle out within the parts in contact with wear surfaces.

Yet another problem with prior devices is the relative inconvenience encountered in servicing the equipment to replace worn seals or other parts, the designs being such that the expansion joint must be taken out of the drill string and laid down on the rig floor for repair. This causes considerable delay in drilling operations and is, of course, undesirable.

The principal object of this invention is to provide a new and improved drilling expansion joint that is highly wear resistant and can be serviced without removal from the drill string.

This and other objects are attained in accordance with the concepts of this invention by a drilling expansion joint apparatus comprising an inner member that is telescopically disposed within an outer member with a slidable spline connection to prevent relative rotation. The lower end portion of the inner member is sealingly slidable within a seal tube having its lower end attached to the outer member and with a seal assembly mounted on its upper end. The seal tube is sized and arranged to provide an annular cavity between its outer periphery and the inner periphery of the outer member, and a plurality of ports communicate the lower end of the cavity with the well annulus.

Debris laden well fluids that enter the cavity during telescoping motion of the members can only contact the seal tube which isolates the wear surfaces on the inner member, and the location of the ports insures that such materials are flushed from the cavity and cannot settle out therein to any appreciable extent. The outer member is formed in parts that can be readily separated near the lower end of the seal tube without disconnecting the joint from the pipe string, thereby exposing the seal tube and seal assembly for maintenance or replacement of parts.

The present invention has other features and advantages which will become more fully apparent in connection with the following detailed description of a preferred embodiment, taken in conjunction with the drawings, in which:

FIG. 1 is a schematic view of a well drilling operation from a floating vessel;

FIGS. 2A and 2B are longitudinal sectional views, with portions in side elevation, of the drilling expansion joint, FIG. 2B forming a lower continuation of FIG. 2A;

FIGS. 3 and 4 are cross-sectional views taken on lines 3--3 and 4--4 of FIG. 2A; and

FIG. 5 is an enlarged sectional view of the seal assembly.

Referring initially to FIG. 1, there is shown schematically a floating drilling rig 10 subject to vertical movement due to wave and tide action and positioned over an offshore well bore 11. A drill bit 12 is connected to the lower end of a series of drill collars 13 which provide the necessary weight on the bit, and a string of drill pipe 14 extends upwardly for suspension from the derrick 15. Coupled between the drill pipe 14 and the drill collars 13 is a slip or expansion joint 16 constructed in accordance with the principles of this invention. The expansion joint 16 provides the capability for longitudinal relative movement between the drill pipe 14 and the drill collars 13 while transmitting torque typical of a rotary drilling operation. The rig operator lowers the drill pipe 13 to place the expansion joint 16 in an intermediate or partially closed condition so that the vessel 10 and the drill pipe can oscillate vertically as previously described without causing any corresponding movement of the drill collars 13, thereby enabling the application of a constant weight on the bit 12. By observing the rig weight indicator, the operator can tell when the bit 12 has proceeded sufficiently that he should lower the drill pipe 14 somewhat to maintain the free telescoping action of the expansion joint 16.

Referring now to FIGS. 2A and 2B, the drilling expansion joint 16 is shown as including an upper, inner member or mandrel 20 telescopically disposed within a lower, outer member or housing 21. The upper end of the inner member has an internally threaded box 22 and the lower end of the outer member has an externally threaded pin 23 for connecting the members in the pipe string. The inner member 20 has upper and lower sections 24 and 25 coupled together by a collar 26, whereas the outer member has threadedly connected sections 27 and 28 with the upper section being attached to an upper sub 29 and the lower section attached to a lower sub 30. The inner member 20 has outwardly projecting splines 31 that mesh with spline keys 32 which are fixed within longitudinally extending grooves 33 provided in an inwardly thickened portion 34 of the upper section 27 as shown in FIG. 3. The upper end of each spline key 32 engages a downwardly facing shoulder 35 on the upper sub 29 and the lower end thereof engages an upwardly facing shoulder 36 provided by the lower end of each groove 33. The spline keys 32 function to prevent relative rotation between the inner and outer members 20 and 21 so that drilling torque can be transmitted through the expansion joint 16. The keys 32 are preferably made of a soft metal relative to the material of the inner member 20, such as ductile iron, so that the keys will take the wear. When excessively worn, they can be readily replaced by unthreading the upper sub 29 with the expansion joint extended. Wear on the keys 32 and on the splines 31 is minimized through the provision of a spline wiper ring 37 that is fitted within an internal recess 38 in a keeper sleeve 39 that is connected to the top of the upper sub 29. The wiper ring 37 is provided with an internal configuration corresponding to the cross-section outline of the splines 31 as shown in FIG. 4 so that the ring has inwardly extending portions 40 received between the splines. The wiper ring 37 functions to prevent particulate matter or other debris in the well fluids from entering at the top between the inner and outer member 20 and 21 during telescoping movement thereof.

A jar collar 42 having a stepped outer diameter is threadedly fixed to the upper section 24 of the inner member 20 at the lower end portion thereof and is sized such that the upper part 43 has a relatively close sliding fit with the inner wall 44 of the upper section 27. The collar 42 has an upwardly facing surface that can be engaged with a companion surface at the lower end of the housing section 34 below the keys 32 to impart an upward bumping or jarring blow upon complete extension of the members 20 and 21. A downward jarring action can be effected by engagement of the lower face of the box 22 with the upper end of the retainer sleeve 39. A plurality of grooves 45 are formed in the upper part 43 to enable free fluid passage during telescoping movement. To provide stability for the lower section 25 of the inner member 20, a ring 46 is suitably fixed within the lower section 28 of the outer member 21 and has a bore sized for a close sliding fit with the outer surface 47 of the lower section. The maintenance of the concentric relation of the members provides a further feature in minimizing seal wear and the like.

A seal assembly designated generally at 50 is provided between the members 20 and 21 to prevent fluid leakage. In accordance with one of the principal features of the present invention, the seal assembly 50 is mounted at the upper end of an upwardly extending seal tube 51 which is rigidly fixed to the bottom sub 30 by threads 52. The outer wall surface 53 of the seal tube 51 is spaced laterally inwardly with respect to the inner wall surface 54 of the outer member 21 to provide a substantial "dead" space or chamber 55 which is in communication with the well annulus by a plurality of ports 56 extending through the wall of the outer member 21 at the lower end of the chamber. The provision of the dead space with bottom ports yields a number of significant advantages over the prior art, in the particulate matter and debris in the well fluids entering the chamber during telescoping motion of the members are confined to the chamber and cannot contact the outer seal surface 57 of the inner member 20. Moreover, debris in the well fluids is flushed from the chamber 55 by telescoping movement of the members and cannot settle out against the inner member 20.

Turning now to the details of the seal assembly 50 shown in FIG. 5, a seal retainer sleeve 60 is fixed by threads 61 to the upper end of the seal tube 51 and is provided with a typical wiper ring 62 at its upper end. The retainer sleeve 60 has an internal annular recess 63 that receives a seal sleeve 64 with spaced packing elements 65 and 66 in sealing engagement with the inner member 20. External sealing rings 67 and 68 prevent fluid leakage between the seal and retainer sleeves 64 and 60. A grease port 69 is provided in the retainer sleeve 60 so that grease can be injected through a port 70 in the seal sleeve 64 above a lower packing element 71, the composite seal assembly providing a long lasting and relatively wear proof structure.

In operation, the parts are assembled as shown in the drawings and coupled into the drill string for drilling operations such as those conducted from a floating drilling vessel that moves vertically under the influence of wave and tide action. The splines 31 and keys 32 transmit torque through the expansion joint 16, and the relative longitudinal movement afforded by the joint accomodates the vertical vessel motion and permits a constant weight to be applied on the bit. The seal assembly 50 prevents fluid leakage of the drilling mud to the well annulus. The pumping action that occurs upon extension and contraction of the expansion joint 16 draws in and expells drilling fluids from the chamber 55, however debris such as cuttings and sand particles and the like are confined to the chamber and do not contact the outer seal surface of the inner member 20. The location of the ports 56 at the lower end of the chamber 55 ensures that such materials are flushed therefrom during closing movement of the joint and cannot settle out within the tool to any appreciable extent.

When it is desired to remove the seal assembly 50 for routine maintenance, this can be accomplished in a simple and expedient manner and without the necessity for disconnecting the expansion joint 16 from the drill string. The lower sub 30 is set in the surface slips at the rotary and the thread 72 is disconnected through the use of conventional power tongs or the like. The inner and outer members 20 and 21 are then fixed together by advancing a threaded plug 73 inwardly into an external groove 74 on the inner member 20, whereupon the members are jointly elevated to expose the seal tube 51 and the seal assembly 50. The packing can be easily redressed or the necessary substitutions made, and of course it is possible to replace either the seal tube 51 or the seal assembly 50 or both with new parts.

Although the present invention has been described in connection with offshore drilling operations, it will be apparent to those skilled in the art that the equipment has other uses where a slip joint coupling is desirable. Since certain changes or modifications may be made in the disclosed embodiment without departing from the inventive concepts involved, it is the aim of the appended claims to cover all such changes and modifications falling within the true spirit and scope of the present invention.

Claims

I claim:

1. Apparatus for use in a well bore, comprising: an inner member telescopically disposed within an outer member; means for preventing relative rotation of said members; a tube connected to a lower section of said outer member and extending upwardly inside said outer member, a portion of said inner member being slidably received within said tube; said tube and outer member being laterally spaced to define an annular chamber; means for communicating the lower end portion of said chamber with the well bore externally of said outer member; and coengageable means on said inner member portion and said tube for preventing fluid leakage.

2. The apparatus of claim 1 wherein said coengageable means includes a seal assembly mounted to the upper end of said tube and having seal elements in sealing contact with the outer periphery of said inner member portion.

3. The apparatus of claim 1 wherein said outer member is formed in parts that can be separated at a location adjacent the lower end of said tube, said lower end of said tube being releasably attached to the lowermost one of the separable parts.

4. The apparatus of claim 3 further including means for fixing said inner and outer members together for joint movement with respect to said tube and said lowermost part.

5. The apparatus of claim 1 further including stabilizing means between said inner and outer members located above said seal means for maintaining said members in concentric disposition during telescoping movement thereof.

6. An expansion or slip joint apparatus for use in a drill string disposed in a well bore, comprising: an upper inner member telescopically disposed within a lower outer member and coupled for limited longitudinal movement; spline means for preventing relative rotation of said members; said outer member constituted by threadedly coupled sections including a bottom sub; a tube located inside said outer member and having its lower end attached to said bottom sub and extending upwardly therefrom in laterally spaced relation to the adjacent section of said outer member, said spaced relation providing an annular chamber, the lower portion of said inner member being slidably received within the bore of said tube; port means for providing fluid communication between said chamber and the well bore externally of said outer member; and seal means on said tube and lower portion for preventing fluid leakage.

7. The apparatus of claim 6 wherein said port means extends through the wall of said outer member near the lower end of said chamber.

8. The apparatus of claim 6 wherein said seal means is mounted at the upper end of said tube and includes seal elements in sliding contact with said lower portion.

9. The apparatus of claim 8 including means operable from the exterior of said outer member for locking said members together, whereby release of the threaded connection for said bottom sub enables said members to move jointly upwardly with respect to said bottom sub and said tube to expose said tube and said seal assembly for maintenance procedures.

10. The apparatus of claim 6 further including wiper means mounted between said members above said spline means, said wiper means including portions projecting between the splines of said spline means.

11. The apparatus of claim 6 further including stabilizing means between said inner and outer members above the upper end of said tube to maintain a concentric disposition of said member during telescoping motion.