Integral Self-Contained Drillstring Compensator
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.
This patent application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62/141,067 titled “Integral Self-Contained Drillstring Compensator” filed on Mar. 31, 2015, the entire content of which is hereby incorporated by reference herein.
TECHNICAL FIELDThe present disclosure relates to an inline self-contained compensator apparatus and method for use and installation on floating drilling rigs and workover or production vessels. In particular, the present disclosure relates to an inline self-contained compensator apparatus that functions as a back-up system for the primary or main heave compensation system of a floating drilling rig or vessel in the event the primary heave compensation system becomes disabled or inoperative.
BACKGROUND OF THE INVENTIONDrilling for oil and gas off-shore is completed from one of two types of drilling rigs: rigs that are supported by the sea floor (such as fixed drilling rigs or jack-up drilling rigs) or rigs that float on the surface of the water (such as drill ships or semi-submersible drilling rigs). Although drilling operations conducted from these two types of drilling rigs are similar, at least one major difference exists: drill ships or semi-submersible drilling rigs move with the waves of the sea, while fixed or jack-up drilling rigs remain fixed to the sea floor.
The movement of drill ships or semi-submersible drilling rigs with the waves of the sea presents a unique problem in drilling with these types of rigs. First, in any drilling operation conducted from floating rigs, compensation for the rig's tendency to heave, that is move up and down with the waves, must be accounted for. In particular, as the floating rig moves up and down, the drill string and drill bit extending below the rig will also move up and down. For a drill bit to perform as efficiently as possible, the desired or optimum weight on the drill bit, i.e., the downward force applied to the bit, must be kept as constant as possible. Heave, however, removes weight from the drill bit as the ship or rig rides to the crest of a wave, and puts weight back on the drill bit as the ship or rig rides down into the trough between waves. This fluctuation in the force applied on the drill bit severely hinders an operator's ability to drill the well bore. Although heave presents a problem in drilling with these types of rigs, heave presents similar problems with other drilling activities, such as well completions, well testing, well interventions, well production, and other operations.
Perhaps more importantly, heave creates the potential for blowouts due to a potential fracturing or breaking of the production tubing during testing, workover, or completion operations. Specifically, once the well bore has been drilled, the oil and gas reserves are brought up to the floating rig through production tubing that runs from the rig to the producing zones of the well bore, typically thousands of feet below the sea floor. The string of production tubing consists of dozens, if not hundreds, of joints of tubing connected together. The production tubing is supported by and is kept in tension by the drill hook and drawworks on the drilling rig to keep the string from buckling.
The production tubing is typically held in place within the well bore by one or more production packers. Because the production tubing is held in place within the well bore, any rise of the floating drilling rig due to heave will increase the tension on the production tubing string and could cause the string to fracture or break. A fracturing or breaking of the production tubing string would allow the oil or gas within the tubing to leak, creating the potential for a blowout.
To account for the problems associated with heave, floating drilling rigs are equipped with a heave compensation system. The heave compensation system is typically in the form of an active heave drawworks system or a system that is an integral part of the drilling derrick or mounted directly on an extension of the traveling block. When functioning properly, these primary heave compensation systems are capable of protecting against the effects of heave. However, many prior art floating drilling rigs are generally not equipped with a back-up, or secondary, heave compensation system that operates in the event the primary heave compensation system is not functioning properly or becomes inoperative. In such a situation, the floating drilling rig will have no way to compensate for heave. Some prior art floating drilling rigs are equipped with a back-up, or secondary, heave compensation system that operates in the event the primary heave compensation system fails, but these systems are very large and require much floor space on the rigs for air compression systems and hoses extending from the air compression systems to the secondary heave compensation system.
Since drill ships or semi-submersible drilling rigs have limited space available on the derrick, what is needed is a heave compensation system that acts as a back-up system to the primary heave compensation system and that is compact and self-contained such that the limited space available on a floating drilling rig is affected in a lesser manner.
The foregoing and other features and aspects of the invention are best understood with reference to the following description of certain exemplary embodiments, when read in conjunction with the accompanying drawings, wherein:
The drawings illustrate only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the exemplary embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTSThe exemplary embodiments disclosed herein are directed to systems, methods, and devices for providing an integral self-contained drillstring compensator that includes a cylinder assembly, an accumulator, and at least one air pressure cylinder and will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The invention is better understood by reading the following description of non-limiting, exemplary embodiments with reference to the attached drawings, wherein like parts of each of the figures are identified by like reference characters, and which are briefly described as follows.
The floating vessel 100 includes the drill floor 120, the derrick 110, and the catwalk 130. The drill floor 120 is disposed substantially in a horizontal direction that is above and substantially parallel to the surface of the water level (not shown). The drill floor 120 is the area on the floating vessel 100 where the tools are located to make the connections of the drill pipe, bottom hole assembly, tools and bit. The drill floor 120 is considered the main area where work is performed.
The derrick 110 extends vertically upward from the drill floor 120. The derrick 110 is the support structure for the equipment used to lower and raise the drill string and/or other equipment into and out of the wellbore (not shown). The derrick 110 includes a crown block 112, a travelling block 114, a top drive 116, and an elevator 118. The crown block 112 is positioned at the top of the derrick 110 and is the stationary section of a block and tackle that contains a set of pulleys or sheaves through which the drill line (wire rope) is threaded or reeved and is opposite and above the traveling block 114. The traveling block 114 is the freely moving section of the block and tackle and is opposite and under the crown block 112. The combination of the traveling block 114, the crown block 112 and wire rope drill line gives the ability to lift weights in the hundreds of thousands of pounds. The crown block 112 is coupled to the travelling block 114 via wires or cables. The top drive 116 is a mechanical device on a floating vessel 100 that provides clockwise torque to the drill string to facilitate the process of drilling a borehole or to provide torque on other equipment to facilitate in the production of oil and gas. The top drive 116 is an alternative to rotary table and is located at the swivel place and allows a vertical movement up and down the derrick 110. The top drive 116 is coupled adjacent to the travelling block 114. The top drive 116 is coupled to the elevator 118 via a plurality of bails (not shown). The elevator 118 is a hinged device that is used to latch to the drill pipe or casing to facilitate the lowering or lifting (of pipe or casing) into or out of the wellbore. The elevator 118 may also be used to latch to other equipment to be place along the drillstring line or production line.
The catwalk 130 is located adjacent the drill floor 120 and includes a riser skate 135 for rolling drill pipe, casing, production tubing and tools onto the drill floor 120. The travelling block 114 travels downward to allow the elevator 118 to couple with the drill pipe, casing, production tubing, tool, or other piece of equipment and raise it into the derrick 110 by retracting upwards.
According to
While on the riser skate 135, the integral self-contained drillstring compensator 150 is rolled along the riser skate 135 to the edge of the riser skate 135 near the drill floor 120. The travelling block 114 is moved axially downward away from the crown block 112 toward the drill floor 120. Once the elevator 118 is adjacent the integral self-contained drillstring compensator 150, the elevator 118 is coupled to a lift sub 152 of the integral self-contained drillstring compensator 150. The lift sub 152 is located at one end of the integral self-contained drillstring compensator 150. It is at this time or prior to this time that the fluid 430 (
As previously mentioned, the integral self-contained drillstring compensator 150 includes the compensating cylinder 260 (
At the end of the cylinder rod 154, which is away from the compensating cylinder 260 (
The at least one high pressure air cylinder 210 includes a first high pressure air cylinder 212 and a second high pressure air cylinder 314 according to certain exemplary embodiments; however, there may be additional or fewer high pressure air cylinders in other exemplary embodiments. Each of the high pressure air cylinders 212, 314 is fabricated from AISI860 material and has a capacity of 700 gallons each. However, in other exemplary embodiments, one or more of the high pressure air cylinders 212, 314 may be constructed using a different suitable material or a different capacity based upon the skill and knowledge of a person having ordinary skill in the art and having the benefit of the present disclosure. The capacity of the high pressure air cylinders 212, 314 may be based upon the amount of weight to be lifted, the compensation to be provided, and/or the space requirements of the floating vessel 100. Further, the first and second high pressure air cylinders 212, 314 are designed to operate under a minimum operating pressure of 350 pounds per square inch (psi) and a maximum operating pressure of 3000 psi. As will be described later with respect to
The first and second high pressure air cylinders 212, 314 are filled with the compressible gas 420 (
The accumulator 240 also is fabricated from AISI860 material and has a capacity of 500 gallons. However, in other exemplary embodiments, the accumulator 240 may be constructed using a different suitable material or a different capacity based upon the skill and knowledge of a person having ordinary skill in the art and having the benefit of the present disclosure. The capacity of the accumulator 240 may be based upon the amount of weight to be lifted, the compensation to be provided, and/or the space requirements of the floating vessel 100. Further, the accumulator 240 is designed to operate under a minimum operating pressure of 350 psi and a maximum operating pressure of 3000 psi.
The accumulator 240 is filled with a fluid 430 (
The compensating cylinder 260 also is fabricated from AISI860 material and includes the cylinder rod 154 therein. However, in other exemplary embodiments, the compensating cylinder 260 may be constructed using a different suitable material based upon the skill and knowledge of a person having ordinary skill in the art and having the benefit of the present disclosure. The compensating cylinder 260 is designed to operate under a minimum operating pressure of 350 psi and a maximum operating pressure of 3000 psi.
The compensating cylinder 260 has a twenty-three inch bore according to some exemplary embodiments; however, the size of the bore may be different according to other exemplary embodiments. The cylinder rod 154 is 8.4 inches in diameter and is fabricated using 17-4 PH H1150 material; however, the cylinder rod 154 may be constructed using a different suitable material based upon the skill and knowledge of a person having ordinary skill in the art and having the benefit of the present disclosure. The cylinder rod 154 has a 240 inch stroke, or 20 feet stroke, and is designed to extend outwardly from the compensating cylinder 240 by its entire stroke length. As previously mentioned, although the stroke length is twenty feet, the cylinder rod 154 is positioned normally extended to ten feet, such that there is ten feet of compensation available in both directions during operation. The compensating cylinder 260 includes the lift sub 152 at one end and is positioned closer to the crown block 112 during installation and operation on the floating vessel 100. The compensating cylinder 260 also includes the lower sub 156 at its opposing end opposite the end where the lift sub 152 is positioned. This lower sub 156 is used to couple with other pipes, casings, tubings, and other equipment that may be used during testing, intervention, drilling, or production.
The compensating cylinder 260 is fluidly coupled to the accumulator 240 using an accumulator/compensating cylinder connector 262. The accumulator/compensating cylinder connector 262 fluidly couples one end of the accumulator to one end or adjacent to one end of the compensating cylinder 260 at the end closer to the lift sub 152. Although the accumulator/compensating cylinder connector 262 is located at or near the end closer to the lift sub 152 according to some exemplary embodiments, the accumulator/compensating cylinder connector 262 may be coupling the accumulator 240 and the compensating cylinder 260 in a different manner in other exemplary embodiments.
A control valve 264 is placed along the air accumulator/compensating cylinder connector 262 so that the fluid 430 (
According to an exemplary embodiment, the components of the integral self-contained drillstring compensator 150 are arranged into a triangular-shaped cross-section. The first high pressure air cylinder 212, the second high pressure air cylinder 314, and the accumulator 240 are positioned at the apexes of an isosceles triangle. The maximum distance between the outer walls of the high pressure air cylinders 212, 314 is about 108 inches, while the maximum distance between the outer wall of the accumulator 240 and outer walls of each of the first and second high pressure air cylinders 212, 314 is about 115 inches. The compensating cylinder 260 is positioned substantially in the center of the triangular cross-section with each of the accumulator 240 and the first and second high pressure air cylinders 212, 314 being coupled to the compensating cylinder 260 with one or more coupling brackets 290.
According to some exemplary embodiments, as previously mentioned, the integral self-contained drillstring compensator 150 includes the optional low pressure air cylinder 380. The low pressure air cylinder 380 also is fabricated from AISI860 material and has a capacity of 100 gallons. However, in other exemplary embodiments, the low pressure air cylinder 380 may be constructed using a different suitable material or a different capacity based upon the skill and knowledge of a person having ordinary skill in the art and having the benefit of the present disclosure. The capacity of the low pressure air cylinder 380 may be based upon the amount of weight to be lifted, the compensation to be provided, and/or the space requirements of the floating vessel 100. Further, the low pressure air cylinder 380 is charged with a low pressure compressible gas 440 (
The low pressure air cylinder 380 is filled with a low pressure compressible gas 440 (
Compressed gas 420 is filled into the high pressure air cylinders 212, 314 as previously mentioned. Also, fluid 430 is filled into the accumulator 240 as previously mentioned. When causing the cylinder rod 154 to retract into the integral self-contained drillstring compensator 150 as seen in
When causing the cylinder rod 154 to extend out of the integral self-contained drillstring compensator 150 as seen in
Hence, as described above, as the cylinder rod 154 of the compensating cylinder 260 strokes in (retracts) and out (extends), the compressible gas 410 that resides within the high pressure air cylinders 212, 314 compresses and decompresses. It is the pressure from this compressible gas 410 that creates tension that the integral self-contained drillstring compensator 150 then exerts on the drillstring or landing string.
The integral self-contained drillstring compensator 150 (
Referring to
According to some exemplary embodiments, the integral self-contained drillstring compensator 150 is designed to have a 750 ton locked capacity and a 500 ton compensating capacity. The total stroke of the cylinder rod 154 is twenty feet, but is design to be at the ten feet midpoint, thereby allowing up to ten feet of compensation in either direction. The dry weight of the integral self-contained drillstring compensator 150 is about 128,000 pounds. The test pressure is 4500 psi, while the maximum operating pressure is 3000 psi and the minimum operating pressure is 350 psi. The service temperature is designed to be a maximum of 120° F. and a minimum of −4° F. As previously mentioned, the fluid 430 is HoughtoSafe or equivalent and the compressible gas 410, 430 is dry nitrogen. Although these are the design parameters of the integral self-contained drillstring compensator 150 according to some exemplary embodiments, other exemplary embodiments may have different design parameters and would not depart from the scope and spirit of the present disclosure.
Although the inventions are described with reference to exemplary embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. From the foregoing, it will be appreciated that an embodiment of the present invention overcomes the limitations of the prior art. Those skilled in the art will appreciate that the present invention is not limited to any specifically discussed application and that the exemplary embodiments described herein are illustrative and not restrictive. From the description of the exemplary embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments of the present invention will suggest themselves to practitioners of the art. Therefore, the scope of the present invention is not limited herein.
Claims
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.
Type: Application
Filed: Mar 31, 2016
Publication Date: Oct 6, 2016
Inventors: Frederick George Holman (Richmond, TX), Richard Hancock (Katy, TX)
Application Number: 15/087,128