Patent ID: 12215586

DETAILED DESCRIPTION

In many horizontal directional drilling applications it is preferable to utilize a dual pipe system. Dual pipe systems are particularly useful for drilling through rock, as the rotation of the inner pipe and outer pipe may be used, independently of one another, to drive rotation of a drill bit and to change the orientation of a steering feature. An example of a dual pipe system is disclosed in U.S. Pat. No. 9,765,574, issued to Slaughter, Jr. et al (“Slaughter”), the contents of which are incorporated herein by reference.

With reference toFIG.8, a directional drilling machine10comprises a carriage12. The carriage12provides axial and rotational force and is configured to connect sections of drill pipe14end to end to form a drill string16. The drill string16comprises an outer and inner component. The inner pipe string is housed within the outer pipe string and may rotate independently of the outer pipe string.

The carriage12comprises a rotational drive system20and a linear drive system. The linear drive system moves the carriage along a rail to provide thrust and pull-back during a drilling operation. The rotational drive system20, such as the system shown inFIG.1, is configured to provide torque for adding and removing pipe sections14from the drill string16, and to provide the axial and rotational force used in drilling and backreaming procedures.

With reference toFIGS.1and2, the rotational drive system20, or gearbox, comprises an inner pipe motor22and an outer pipe motor24. The outer pipe motor24provides torque to the outer pipe string and the inner pipe motor22provides torque to the inner pipe string. Torque is transferred from the gearbox20to the drill string16through a spindle30. The spindle30has inner and outer components, as shown inFIGS.2-7, which are preferably substantially centered about a longitudinal axis31. The axis31is also an axis of rotation for the inner and outer components of the spindle30.

The gearbox20comprises an outer output gear26and an inner output gear28. The outer output gear26, driven by the outer motor24, transmits torque to an outer drive shaft32. Likewise, the inner output gear28, driven by the inner motor22, transmits torque to the inner drive shaft34. The inner drive shaft34and outer drive shaft32rotate independently of each other. The outer drive shaft32is supported by a plurality of outer drive shaft bearings36. Likewise, the inner drive shaft34is held in place by a plurality of inner drive shaft bearings37. The inner34and outer32drive shafts transmit torque to the drill string16through the spindle30.

With reference toFIGS.3-7, components of the spindle30are shown. The spindle30comprises an outer member40which is rotationally joined to the outer drive shaft32by a plurality of retainer socket screws42disposed in a flange44of the outer member40. The inner drive shaft34, or a stub joined thereto, is disposed within a cavity46formed in the outer member40. The outer member40has an end48which is configured for connection to an outer member of the drill string16. The outer member40may also have an opening for a connection to a wireline.

An inner drive rod apparatus50is disposed within the outer member40. The inner drive rod apparatus50comprises a collar52, a drive rod54, and a hollow sleeve56. The collar52is configured for connection to an inner member of a dual member drill string16. As shown, the collar52has a torque-transmitting inner profile for imparting rotation to the inner member of the drill string16. The hollow sleeve56may be formed integrally with the drive rod54or may be joined by a circumferential weld58.

The hollow sleeve56, as shown, has an internal profile60which conforms to an outer profile62of the drive shaft34. The profiles60,62, are configured for torque-transmitting connection during rotation of the drive shaft34. However, the profiles60,62are also configured to allow sliding relative movement between the drive shaft34and hollow sleeve56within a range of motion.

As best shown inFIG.6, the profiles60,62comprise complementary interlocking splines. However, other geometry may be utilized, including, but not limited to polygonal profiles, protrusions or depressions with torque-transmitting elements, and the like. Further, while the profile60of the sleeve56is shown on its inner surface and the profile62of the drive shaft34on its outer surface, other orientations which allow relative axial movement but allow torque transmission may be utilized.

A spring70is disposed between the drive shaft34and the drive rod54. The spring70biases the drive rod54to a forward position as shown inFIG.4, away from the gearbox20. As drilling operations continue, the drive rod54may be forced in a direction toward the gearbox20. As shown inFIG.5, as the spring70compresses, the inner drive rod54and sleeve56are forced axially towards the gearbox20.

With reference again toFIG.8, during makeup of a pipe section14to the drill string16, inner and outer pipe connections are made up simultaneously. There is, however, the potential for misalignment between the ends of the inner pipe sections while adjacent outer pipe sections are threadedly connected. This scenario can cause the inner pipe section which is attached to the inner drive rod54to be unintentionally forced axially toward the gearbox20. If the inner drive rod54is forced into the gearbox20, the axial force may be transferred to one or more of the plurality of inner drive shaft34or gearbox bearings37. The force exerted on the bearings37may cause considerable damage to the gearbox20.

The present invention solves this problem by transferring the axial load of the inner drive rod54to the outer member40, and therefore to the outer drive shaft32. The outer gearbox bearings36are much larger than the inner gearbox bearings37and may withstand the axial loads which may be exerted by the inner drive rod.

The spindle30comprises a stop member80defining a limit of the axial movement of the sleeve56in a direction toward the gearbox20. The stop member80is preferably transverse to the longitudinal axis31of the spindle30. The sleeve56terminates in a shoulder57. This shoulder57, at its limit of axial movement, contacts the stop member80.

The stop member80is disposed through the outer member40. As a result, axial force transmitted through the drill rod54and sleeve56will transfer to the outer member40(and thus components of the outer member's rotational drive) rather than the inner drive shaft34. The stop member80is positioned, as best shown inFIG.6, such that it reduces the effective inner diameter of the cavity46such that it is less than an outer diameter of the sleeve56, but greater than the outer diameter of the drive shaft34.

As shown, the stop member80comprises two spaced-apart dowel pins82. Each dowel pin82is trapped within a pair of transfer bolts84. Through-holes86are provided in the flange44of the outer member40. The through-holes86are spaced such that the pins82sit parallel to each other, with one pin situated on each side of the inner drive shaft34. The distance between the parallel pins82is greater than the diameter of the inner drive shaft34, but less than the diameter of the sleeve56. This allows the inner drive shaft34to rotate independently of the outer member40without interference from the dowel pins82, but does allow engagement between the shoulder of the sleeve56and the dowel pins82. The transfer bolts84are preferably sealing bolts to prevent leakage of drilling fluid.

Upon engagement of the sleeve56with the dowel pins82, the axial force that would have been transmitted to the inner drive shaft34is now transmitted to the outer member40, and subsequently to the outer drive shaft32. As stated above, the outer drive shaft32is designed to regularly withstand high axial loads.

To assemble the spindle30, the outer member40is placed over the assembled inner drive components, including the drive rod54, sleeve56and inner drive shaft34. The outer member40is then attached to the gearbox20with the retainer socket screws42. Finally, the dowel pins82are inserted into the through holes86in the flange44and held in place by the installation of the transfer bolts84.

As shown, the spindle30is configured to run drill pipe14in the “pin-up” configuration. Each outer pipe section comprises a pin end and a box end. The outer member40comprises a box end90that may threadedly engage with the pin end of an outer pipe section. The inner drive rod54is attached to the collar52, which may likewise provide a hexagonal box end92for connection to an inner pipe section. Other geometric shapes, such as is provided for in Slaughter, may also be used.

Each inner pipe section comprises a pin end with a complementary outwardly facing geometric shape that is slideably receivable within the collar52. Each inner pipe section comprises a box end and a pin end. This configuration provides transmission of torque between the inner drive rod and an adjacent inner pipe section and between adjacent inner pipe sections. The inner drive shaft34and drive rod52may comprise an internally-disposed fluid passage95centered upon the longitudinal axis31of the spindle30. The passage95may be used for the transmission of drilling fluid downhole.

The various features and alternative details of construction of the apparatuses described herein for the practice of the present technology will readily occur to the skilled artisan in view of the foregoing discussion, and it is to be understood that even though numerous characteristics and advantages of various embodiments of the present technology have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the technology, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present technology to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.