Integral Self-Contained Drillstring Compensator

Abstract

An integral self-contained drillstring compensator includes at least one high pressure air cylinder, an accumulator, and a compensating cylinder, which are fluidly coupled to one another. The high pressure air cylinders include a compressible gas that is communicable to the accumulator, which has fluid included therein. The compressible gas provides a pressure on the fluid, thereby allowing the fluid to communicable between the accumulator and the compensating cylinder. The fluid causes a cylinder rod within the compensating cylinder to extend and retract from the compensating cylinder, thereby providing compensation during heaves. The drillstring compensator optionally includes a low pressure air cylinder to store a low pressure compressible fluid that communicates with the compensating cylinder.

We claim: 
     
         1 . A method of installing an integral self-contained drillstring compensator on a floating vessel, comprising:
 placing an integral self-contained drillstring compensator adjacent a drill floor on a floating vessel;   charging a first portion of the integral self-contained drillstring compensator with a compressible gas; and   lifting the integral self-contained drillstring compensator, after charging the integral self-contained drillstring compensator, into a derrick, the derrick extending substantially vertically upward from the drill floor.   
     
     
         2 . The method of  claim 1 , further comprising charging a second portion of the integral self-contained drillstring compensator with a fluid prior to lifting the integral self-contained drillstring compensator. 
     
     
         3 . The method of  claim 2 , wherein the integral self-contained drillstring compensator comprises:
 at least one high pressure air cylinder;   an accumulator fluidly coupled to the at least one high pressure air cylinder; and   a compensating cylinder comprising a cylinder rod therein, the cylinder rod being capable of extending outwardly from the compensating cylinder and retracting inwardly into the compensating cylinder, the compensating cylinder being fluidly coupled to the accumulator,   wherein the first portion comprises the at least one high pressure air cylinder, and the second portion comprises the accumulator.   
     
     
         4 . The method of  claim 3 , further comprising charging a third portion of the integral self-contained drillstring compensator with a low pressure compressible gas prior to lifting the integral self-contained drillstring compensator. 
     
     
         5 . The method of  claim 4 , wherein the integral self-contained drillstring compensator further comprises:
 a low pressure air cylinder fluidly coupled to the compensating cylinder,   wherein the third portion comprises the low pressure air cylinder.   
     
     
         6 . A method of providing heave compensation using an integral self-contained drillstring compensator installed in a derrick of a floating vessel, comprising:
 providing an integral self-contained drillstring compensator in a derrick of a floating vessel, the integral self-contained drillstring compensator comprising:
 at least one high pressure air cylinder comprising compressible gas therein; 
 an accumulator fluidly coupled to the at least one high pressure air cylinder, the accumulator comprising a fluid therein; and 
 a compensating cylinder comprising a cylinder rod therein, the cylinder rod being capable of extending outwardly from the compensating cylinder and retracting inwardly into the compensating cylinder, the compensating cylinder being fluidly coupled to the accumulator, 
   receiving a heave load into the integral self-contained drillstring compensator;   allowing the compressible gas to fluidly move between the at least one high pressure air cylinder and the accumulator in response to the heave load;   allowing the fluid to fluidly move between the accumulator and the compensating cylinder based upon the direction of movement of the compressible gas;   providing compensation in response to the heave load by having the cylinder rod extend further outwardly of the compensating cylinder or retract further inwardly into the compensating cylinder based upon the direction of movement of the fluid between the accumulator and the compensating cylinder.   
     
     
         7 . The method of  claim 6 , wherein the integral self-contained drillstring compensator further comprises a shut-off control valve positioned along a fluid communication extending between the accumulator and the compensating cylinder, the shut-off control valve regulating the amount of fluid flowing in either direction. 
     
     
         8 . The method of  claim 6 , wherein the cylinder rod extends further outwardly of the compensating cylinder when at least a portion of the fluid moves from the compensating cylinder to the accumulator causing at least a portion of the compressible gas to move from the accumulator to the at least one high pressure air cylinders, and wherein the cylinder rod retracts further inwardly into the compensating cylinder when the compressible gas moves from the at least one high pressure air cylinders to the accumulator causing at least a portion of the fluid to move from the accumulator to the compensating cylinder. 
     
     
         9 . The method of  claim 8 , wherein the integral self-contained drillstring compensator further comprises a low pressure air cylinder fluidly coupled to the compensating cylinder, the low pressure air cylinder comprising a low pressure compressible gas,
 wherein when the cylinder rod extends further outwardly of the compensating cylinder, at least a portion of the low pressure compressible gas moves from the low pressure air cylinder into the compensating cylinder, and   wherein when the cylinder rod retracts further inwardly into the compensating cylinder, at least a portion of the low pressure compressible gas moves from the compensating cylinder into the low pressure air cylinder.   
     
     
         10 . The method of  claim 9 , wherein the compressible gas comprises at least one of nitrogen and air and the low pressure compressible gas comprises at least one of nitrogen and air. 
     
     
         11 . The method of  claim 9 , wherein the accumulator comprises an accumulator cap positioned therein, the accumulator cap axially movable along the inner portion of the accumulator and separates the compressible gas from the fluid, and wherein the compensating cylinder comprises a cylinder cap positioned therein and from which the cylinder rod extends therefrom, the cylinder cap axially movable along the inner portion of the compensating cylinder and separates the fluid from the low pressure compressible gas. 
     
     
         12 . The method of  claim 6 , wherein the fluid comprises at least one of ethylene glycol, CTF, and water. 
     
     
         13 . An integral self-contained drillstring compensator, comprising:
 at least one high pressure air cylinder comprising compressible gas therein;   an accumulator fluidly coupled to the at least one high pressure air cylinder, the accumulator comprising a fluid therein; and   a compensating cylinder comprising a cylinder rod therein, the cylinder rod being capable of extending outwardly from the compensating cylinder and retracting inwardly into the compensating cylinder, the compensating cylinder being fluidly coupled to the accumulator,   wherein the compressible gas moves between the at least one high pressure air cylinder and the accumulator,   wherein the fluid moves between the accumulator and the compensating cylinder, and   wherein each of the at least one high pressure air cylinder and the accumulator are fastenedly coupled to the compensating cylinder.   
     
     
         14 . The integral self-contained drillstring compensator of  claim 13 , further comprising a shut-off control valve positioned along a fluid communication extending between the accumulator and the compensating cylinder, the shut-off control valve regulating the amount of fluid flowing in either direction. 
     
     
         15 . The integral self-contained drillstring compensator of  claim 13 , wherein the cylinder rod extends further outwardly of the compensating cylinder when at least a portion of the fluid moves from the compensating cylinder to the accumulator causing at least a portion of the compressible gas to move from the accumulator to the at least one high pressure air cylinders, and wherein the cylinder rod retracts further inwardly into the compensating cylinder when the compressible gas moves from the at least one high pressure air cylinders to the accumulator causing at least a portion of the fluid to move from the accumulator to the compensating cylinder. 
     
     
         16 . The integral self-contained drillstring compensator of  claim 15 , further comprising a low pressure air cylinder fluidly coupled to the compensating cylinder, the low pressure air cylinder comprising a low pressure compressible gas,
 wherein when the cylinder rod extends further outwardly of the compensating cylinder, at least a portion of the low pressure compressible gas moves from the low pressure air cylinder into the compensating cylinder, and   wherein when the cylinder rod retracts further inwardly into the compensating cylinder, at least a portion of the low pressure compressible gas moves from the compensating cylinder into the low pressure air cylinder.   
     
     
         17 . The integral self-contained drillstring compensator of  claim 16 , wherein the compressible gas comprises at least one of nitrogen and air and the low pressure compressible gas comprises at least one of nitrogen and air. 
     
     
         18 . The integral self-contained drillstring compensator of  claim 16 , wherein the accumulator comprises an accumulator cap positioned therein, the accumulator cap axially movable along the inner portion of the accumulator and separates the compressible gas from the fluid, and wherein the compensating cylinder comprises a cylinder cap positioned therein and from which the cylinder rod extends therefrom, the cylinder cap axially movable along the inner portion of the compensating cylinder and separates the fluid from the low pressure compressible gas. 
     
     
         19 . The integral self-contained drillstring compensator of  claim 13 , wherein the fluid comprises at least one of ethylene glycol, CTF, and water.