Hydraulic motion compensating apparatus

Abstract

A compensating apparatus is suspended from a divided crown block mounted on a derrick of a floating drilling barge, the compensating apparatus including a single cylinder extending vertically between and carrying divided travelling block sheaves on opposite sides thereof, with drawwork lines passing over the divided crown block sheaves and divided travelling block sheaves, and with the upper portion of the cylinder extending between such lines and adapted to move upwardly between the crown block sheaves without interference. A piston structure, forming part of the compensating apparatus, is slidable in the cylinder, being connected to a hook, or the like, from which a running string, such as a drilling string, is suspended extends into an underlying well bore, liquid under pressure in the cylinder acting on the piston structure to support part or all of the weight of the running string. The piston structure and cylinder can be locked together mechanically when in a fully contracted condition to render the compensating apparatus ineffective.

We claim: 
     
       1. An apparatus for maintaining a predetermined stress in a running string disposed in a well bore and which is supported by a rig, including a derrick and a suspension mechanism supported from the upper portion of the derrick: comprising a travelling block structure adapted to form part of the suspension mechanism; a hook structure adapted to support the running string therebelow; a motion compensating apparatus disposed between and connected to said block structure and hook structure; said motion compensating apparatus comprising cylinder means coaxial of said hook structure; piston means slidable in said cylinder means and connected to said hook structure; said travelling block structure being split and fixedly mounted to said cylinder means on opposite sides of said cylinder means substantially below the upper end of said cylinder means and with said cylinder means disposed between said split block structure; and means for maintaining a fluid medium under pressure in said cylinder means for exerting an upward force on said piston means as said piston means and cylinder means move longitudinally relative to one another in both longitudinal directions. 
     
     
       2. An apparatus as defined in claim 1; said block structure comprising one or more sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof. 
     
     
       3. An apparatus as defined in claim 1; said block structure comprising one or more sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof; said cylinder means projecting upwardly beyond said sheaves. 
     
     
       4. An apparatus as defined in claim 1; and means for releasably locking said piston means and cylinder means to each other when said piston means is substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means. 
     
     
       5. An apparatus as defined in claim 1; collet means for releasably locking said piston means and cylinder means to each other when said piston means is substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means; and means movable longitudinally along one of said cylinder means and piston means for selectively shifting said collet means to locking or unlocking position. 
     
     
       6. An apparatus as defined in claim 1; collet means for releasably locking said piston means and cylinder means to each other when said piston means is substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means; and hydraulically operable means movable longitudinally along said cylinder means for selectively shifting said collet means to locking or unlocking position. 
     
     
       7. An apparatus as defined in claim 1; said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable; said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member; said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealed relation to said outer and inner members; and means for directing said fluid medium under pressure into the space between said piston rod and inner wall of said outer member for action upon said piston; said piston rod being laterally spaced from said inner member to provide a second annular space therebetween; and means for directing said fluid medium under pressure into said second annular space for action upon said piston. 
     
     
       8. An apparatus as defined in claim 1; said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable; said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member; said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealed relation to said outer and inner members; and means for directing said fluid medium under pressure into the space between said piston rod and inner wall of said outer member for action upon said piston; and means for releasably locking said piston rod and outer member to each other when said piston and piston rod are substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means. 
     
     
       9. An apparatus as defined in claim 1; said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable; said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member; said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealed relation to said outer and inner members; and means for directing said fluid medium under pressure into the space between said piston rod and inner wall of said outer member for action upon said piston; collet means for releasably locking said piston rod and outer member to each other when said piston means is substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means; and means movable longitudinally along said outer member for selectively shifting said collet means to locking or unlocking position. 
     
     
       10. An apparatus for maintaining a predetermined stress in a running string disposed in a well bore and which is supported by a rig, including a derrick: comprising a suspension mechanism including a split crown block structure adapted to be supported from the upper portion of the derrick; a travelling block structure below said crown block structure and suspended therefrom by lines passing around both structures; a hook structure adapted to support the running string therebelow; a motion compensating apparatus disposed between and connected to said travelling block structure and hook structure; said motion compensating apparatus comprising cylinder means coaxial of said hook structure; piston means slidable in said cylinder means and connected to said hook structure; said travelling block structure being split and fixedly mounted to said cylinder means on opposite sides of said cylinder means substantially below the upper end of said cylinder means and with said cylinder means disposed between said split block structure; and means for maintaining a fluid medium under pressure in said cylinder means for exerting an upward force on said piston means as said piston means and cylinder means move longitudinally relative to one another in both longitudinal directions. 
     
     
       11. An apparatus as defined in claim 10, said crown block structure comprising sets of sheaves laterally spaced from each other; said travelling block structure comprising one or more sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof. 
     
     
       12. An apparatus as defined in claim 10; said crown block structure comprising sets of sheaves laterally spaced from each other; said travelling block structure comprising one or more sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof; said cylinder means projecting upwardly beyond, said travelling block sheaves and adapted to extend between said sets of sheaves of said crown block structure. 
     
     
       13. An apparatus as defined in claim 10; said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable; said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member; said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealing relation to said outer and inner members; and means for directing said fluid medium under pressure into the space between said piston rod and inner wall of said outer member for action upon said piston. 
     
     
       14. An apparatus as defined in claim 10; said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable; said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member; said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealing relation to said outer and inner members; and means for directing said fluid medium under pressure into the space between said piston rod and inner wall of said outer member for action upon said piston; and means for releasably locking said piston rod and outer member to each other when said piston means is substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means. 
     
     
       15. An apparatus as defined in claim 10, said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable; said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member; said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealing relation to said outer and inner members; and means for directing said fluid medium under pressure into the space between said piston rod and inner wall of said outer member for action upon said piston; collet means for releasably locking said piston rod and outer member to each other when said piston means is substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means; and means movable longitudinally along said outer member for selectively shifting said collet means to locking or unlocking position. .Iadd. 16. An apparatus useful for maintaining a predetermined stress in a running string positioned in well bore and supported by a rig including suspension mechanism for which the running string is suspended, said apparatus including a travelling block structure adapted to form part of the suspension mechanism, a support structure adapted to support the running string therebelow, a motion compensating apparatus disposed between and connected to said travelling block structure and support structure, said motion compensating apparatus comprising cylinder means coaxial of said support structure, piston means slidable in said cylinder means and connected to said support structure, said travelling block structure being split and fixedly mounted to said cylinder means on opposite sides of said cylinder means substantially below the upper end of said cylinder means and with said cylinder means disposed between said split travelling block structure, and means on said cylinder means for connection to a source of fluid pressure for maintaining a fluid medium under pressure in said cylinder means for exerting an upward force on said piston means as said piston means and cylinder means move longitudinally relative to one another in both longitudinal directions. .Iaddend..Iadd. 17. An apparatus as defined in claim 16; said travelling block structure comprising one or more sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof. .Iaddend. .Iadd. 18. An apparatus as defined in claim 16; said travelling block structure comprising one or more sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof, said cylinder means projecting upwardly beyond said sheaves..Iaddend. .Iadd. 19. An apparatus as defined in claim 16; and means for releasably locking said piston means and cylinder means to each other when said piston means is substantially fully telescoped within said cylinder means to prevent relative longitudinal movement between said piston means and cylinder means..Iaddend. .Iadd. 20. An apparatus as defined in claim 16; said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable, said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member, said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealed relation to said outer and inner members, means for directing a fluid medium under pressure into the space between said piston rod and inner wall of said outer member for acting upon said piston, said piston rod being laterally spaced from said inner member to provide a second annular space therebetween, and means for directing said fluid medium under pressure into said second annular space for action upon said piston. .Iaddend. .Iadd. 21. An apparatus useful for maintaining a predetermined stress in a running string disposed in a well bore and which is supported by a rig which includes a derrick; said apparatus including a suspension mechanism including a split crown block structure adapted to be supported from the upper portion of the derrick, a travelling block structure below said crown block structure and suspended therefrom by lines passing around both structures, a support structure adapted to support the running string therebelow, a motion compensating apparatus disposed between and connected to said travelling block structure and support structure, said motion compensating apparatus comprising cylinder means coaxial of said support structure, piston means slidable in said cylinder means and connected to said support structure, said travelling block structure being split and fixedly mounted to said cylinder means on opposite sides of said cylinder means substantially below the upper end of said cylinder means and with said cylinder means disposed between said split block structure, and means for directing a fluid medium under pressure into said cylinder means for exerting an upward force on said piston means as said piston means and cylinder means move longitudinally relative to one another in both longitudinal directions..Iaddend. .Iadd. 22. An apparatus as defined in claim 21; said crown block structure comprising sets of sheaves laterally spaced from each other, said travelling block structure comprising one or moe sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof..Iaddend. .Iadd. 23. An apparatus as defined in claim 21; said crown block structure comprising sets of sheaves laterally spaced from each other, said travelling block structure comprising one or more sheaves rotatably mounted on said cylinder means at one side thereof and one or more sheaves rotatably mounted on said cylinder means at the opposite side thereof, said cylinder means projecting upwardly beyond said travelling block sheaves and adapted to extend between said sets of sheaves of said crown block structure..Iaddend. .Iadd. 24. An apparatus as defined in claim 21; said cylinder means comprising an outer member and an inner member therewithin and secured to said outer member, said inner and outer members being laterally spaced from each other to provide an annular space therebetween in which said piston means is movable, said piston means comprising a piston in said annular space slidably sealing against the inner wall of said outer member and the outer wall of said inner member, said piston means further comprising a piston rod secured to said piston and laterally spaced from said inner wall of said outer member and in slidable sealing relation to said outer and inner members, means for directing said fluid medium under pressure into the annular space between said piston rod and inner wall of said outer member for action upon said piston, said piston rod being laterally spaced from said inner member to provide a second annular space therebetween, and means for directing said fluid medium under pressure into said second annular space for action upon said piston. .Iaddend. .Iadd. 25. On a floating drilling platform of the type having a derrick, an upper crown block assembly having a plurality of sheaves mounted on the derrick, a lower travelling block assembly having a plurality of sheaves, powered cable means interconnecting the travelling block assembly and the crown block assembly, a rotary carrier for supporting the drill string below the travelling block, and a hydraulic heave compensator between the travelling block assembly and the rotary carrier; said crown block being formed with a vertical opening passing between said sheaves and said heave compensator comprising a central cylinder mounted on the travelling block assembly and arranged to pass through said vertical opening while the travelling block is selectively raised by the cable means, a piston in said cylinder having a rod projecting downwardly to said carrier, and coupling means for selectively coupling said carrier to the travelling block assembly when the piston is raised in the cylinder. .Iaddend.