Slip spool assembly and method of using same
View Patent ↗A slip spool includes radially disposed actuators for radially moving slip blocks between a loose encirclement position in which they surround the tubing string and a cached position in which the slip blocks clear an axial passage of the slip spool. The slip spool further includes axially disposed actuators for axially displacing the slip blocks between the loose encirclement position and an engagement position in which the slip blocks are seated within a slip bowl of the slip spool so that a weight of the suspended tubing string causes the slip blocks to tightly grip the tubing string. The slip spool facilitates positioning and repositioning of the tubing string in the wellbore and can be used for supporting or snubbing a tubing string in a live well bore.
1. A slip spool for selectively supporting or snubbing a tubing string suspended in a wellbore under pressure, the slip spool comprising:
a slip spool body adapted to be mounted to a wellhead, the slip spool body having an axial passage that is aligned with the wellbore for permitting the tubing string to extend therethrough, at least two opposed radial passages extending through a side wall of the slip spool and communicating with the axial passage, and a slip bowl formed in a bottom of the axial passage;
at least two opposed slip block assemblies slidably supported within the respective opposed radial passages and movable from a cached position in which the slip block assemblies clear the axial passage and an engaged position in which the slip block assemblies are seated in the slip bowl; and
mechanisms that displace the respective slip block assemblies from the cached position to the engaged position, and from the engaged position to the cached position.
2. The slip spool as claimed in claim 1 wherein the mechanisms that displace the respective slip block assemblies comprise:
mechanisms that radially displace the respective slip block assemblies between the cached position and a loose encirclement position in which the slip block assemblies surround the tubing string; and
mechanisms that axially displace the slip block assemblies from the loose encirclement position to the engaged position in which the slip block assemblies are seated within the slip bowl.
3. The slip spool as claimed in claim 2 wherein the mechanisms that radially displace the at least two slip block assemblies comprise at least two horizontally disposed hydraulic actuators mounted to the slip spool body and connected to the respective slip block assemblies.
4. The slip spool as claimed in claim 3 wherein the mechanisms that axially displace the slip block assemblies comprise at least two vertically disposed hydraulic actuators mounted to the slip spool and connected to the respective slip block assemblies.
5. The slip spool as claimed in claim 4 wherein the slip block assemblies further comprise a pair of slotted actuating arms, each slotted actuating arm interconnecting a respective hydraulic actuator and a slip block assembly, the slotted actuating arm including a vertical slot to permit the arm to move vertically relative to the horizontally disposed actuator and a longitudinal slot to permit the arm to move horizontally relative to the vertically disposed actuator.
6. The slip spool as claimed in claim 5 wherein the vertical slot is a T-slot permitting the arm to slide vertically relative to a plate connected to a piston rod of each horizontally disposed actuator and wherein the longitudinal slot permits horizontal displacement of the arm relative to the vertically disposed actuator, which extends through the longitudinal slot.
7. The slip spool as claimed in claim 3 wherein the mechanism that axially displaces the slip block assemblies further comprises an axial displacement indicator.
8. The slip spool as claimed in claim 3 further comprising a fluid communications path for communicating well fluid to opposite sides of the hydraulic actuators that radially displace the respective slip block assemblies.
9. The slip spool as claimed 8 wherein the fluid communications path comprises a hollow hydraulic cylinder rod connected to a hydraulic piston having a hollow inner end, and a port through the hydraulic piston that provides fluid communication between the hollow inner end of the hydraulic piston and an annular gap located between an outer end of the hydraulic piston and a protective shroud that surrounds the outer end of the hydraulic piston.
10. The slip spool as claimed in claim 2 wherein each slip block assembly comprises a pipe guide extending peripherally from a face of a slip block assembly and having an angled surface for directing the tubing string toward a center of the axial passage as the slip block assemblies converge to the loose encirclement position.
11. The slip spool as claimed in claim 10 wherein each slip block assembly comprises a slot that receives the pipe guide when the slip block assemblies converge to the loose encirclement position.
12. The slip spool as claimed in claim 2 wherein the mechanism that radially displaces the slip block assemblies further comprises a radial displacement indicator.
13. The slip spool as claimed in claim 1 wherein each of the at least two slip block assemblies comprises a plurality of segmented, interconnected slip blocks and the at least two slip block assemblies together fully encircle the tubing string.
14. The slip spool as claimed in claim 1 wherein each of the at least two slip block assemblies comprises three loosely interconnected wedge-shaped slip blocks that collectively form a frusta-conical assembly having a central passageway dimensioned to grip the tubing string when seated in the slip bowl.
15. The slip spool as claimed in claim 1 wherein each of the at least two slip block assemblies comprises a wedge-shaped center slip and a pair of wedged-shaped side slips loosely connected to the center slip.
16. The slip spool as claimed in claim 15 wherein the side slips are loosely connected to the center slip by interlock bars loosely fitted within slots in the slips.
17. The slip spool as claimed in claim 16 further comprising retainer plates connected to the slips for retaining the interlock bars within the slots in the slips.
18. A method for selectively supporting a tubing string suspended in a well bore of a well during a live well operation, the method comprising:
mounting a slip spool to a wellhead of the well by aligning an axial passage of the slip spool with the well bore;
displacing slip blocks within radial passages of the slip spool using a radial actuation mechanism having a radial range of movement sufficient to displace the slip blocks between a cached position in which the slip blocks clear the axial passage of the slip spool and a loose encirclement position in which the slip blocks loosely surround the tubing string; and
axially displacing the slip blocks within the axial passage of the slip spool using an axial actuation mechanism having an axial range of movement sufficient to displace the slip blocks between the loose encirclement position and an engaged position in which the slip blocks are seated within a slip bowl of the slip spool.
19. The method as claimed in claim 18 wherein radially and axially displacing the slip blocks are performed by operating independently operable radially disposed hydraulic actuators and axially disposed hydraulic actuators.
20. The method as claimed in claim 18 comprising mounting the slip spool in a first orientation for supporting the tubing string, and mounting the slip spool in an opposite orientation for snubbing the tubing string.