Heave compensation system

A drilling system comprises a drilling vessel comprising a rig floor, a derrick extending from the rig floor of the drilling vessel along a longitudinal axis. The derrick comprises a first end disposed at the rig floor and a second end longitudinally spaced from the first end, and a heave compensation system disposed at the second end of the derrick. The heave compensation system comprises a support structure comprising a first laterally extending frame coupled to the second end of the derrick, and a second laterally extending frame spaced from the first frame, a crown block coupled to the support structure and a transport assembly coupled to the second frame of the support structure. The transport assembly comprises a first lifting lug and a cylinder assembly supported by the first frame, wherein the cylinder assembly is releasably coupled with the crown block and configured to longitudinally displace the crown block relative to the support structure in response to a heave movement of the vessel. The transport assembly is configured to releasably couple with the cylinder assembly via a cable extending through the first lifting lug, and to support the weight of the cylinder assembly in response to the cylinder assembly being lowered from the first lifting lug to the rig floor through an internal volume of the derrick.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

Not applicable.

BACKGROUND

Drilling systems are sometimes utilized for the extraction of hydrocarbons from a subterranean earthen formation via a drilling wellbore into the formation. In some applications, drilling systems are located offshore and include a floating vessel disposed at the waterline, with a drillstring extending from the vessel to the subterranean wellbore. The operations of many floating vessels, such as semi-submersible drilling rigs, drill ships, and pipe-laying ships, are impeded by sea swell. Particularly, sea waves impart an up-and-down motion to a vessel, commonly referred to as “heave,” with the period of the waves ranging anywhere from a few seconds up to about 30 seconds or so and the amplitude of the waves ranges from a few centimeters or inches up to about 15 meters (about 50 feet) or more. This up-and-down motion imparted to the vessel from the waves is then correspondingly imparted to any loads or structures attached to the vessel.

In particular, this heave motion of the loads or structures extending from the vessel is often highly undesirable, and even dangerous, to equipment and personnel. Heave compensation is directed to reducing the effect of this up-and-down motion on a load attached to the vessel. In particular, “passive” heave compensation systems are typically used by fixing the load to a point, such as the sea bed. Sea swell may then cause the vessel to move relative to the load, in which a passive compensator uses compressed air to provide a low frequency damping effect between the load and the vessel. Further, “active” heave compensation systems may be used that typically involve measuring the movement of the vessel using a measuring device, such as a motion reference unit (“MRU”), and using a signal from the MRU that represents the motion of the vessel to compensate for the motion.

SUMMARY

An embodiment of a drilling system comprises a drilling vessel comprising a rig floor, a derrick extending from the rig floor of the drilling vessel along a longitudinal axis, wherein the derrick comprises a first end disposed at the rig floor and a second end longitudinally spaced from the first end, a heave compensation system disposed at the second end of the derrick, the heave compensation system comprising: a support structure comprising a first laterally extending frame coupled to the second end of the derrick, and a second laterally extending frame spaced from the first frame, a crown block coupled to the support structure, a transport assembly coupled to the second frame of the support structure, wherein the transport assembly comprises a first lifting lug, and a cylinder assembly supported by the first frame, wherein the cylinder assembly is releasably coupled with the crown block and configured to longitudinally displace the crown block relative to the support structure in response to a heave movement of the vessel, wherein the transport assembly is configured to releasably couple with the cylinder assembly via a cable extending through the first lifting lug, and wherein the transport assembly is configured to support the weight of the cylinder assembly in response to the cylinder assembly being lowered from the first lifting lug to the rig floor through an internal volume of the derrick. In some embodiments, the transport assembly of the heave compensation system comprises a plurality of laterally spaced first support beams, wherein each first support beam extends longitudinally from the second frame of the support structure, and a laterally extending second support beam pivotably coupled to one of the plurality of laterally spaced first support beams, wherein the first lifting lug extends from the second support beam. In some embodiments, the laterally extending second support beam is configured to pivot to a position intersecting a longitudinal axis of the cylinder assembly. In some embodiments, the support structure comprises a longitudinal structure coupled to the first frame and the second frame. In certain embodiments, the longitudinal structure comprises a pair of angled support members coupled to the first frame and the second frame, and a cross-support member extending between the pair of angled support members, wherein the cross-support members is releasably coupled with the angled support members. In certain embodiments, the first frame of the support structure comprises a first open area configured to provide space for the cylinder assembly to be displaced therethrough in response to the cylinder assembly in response to the lowering of the cylinder assembly towards the rig floor. In some embodiments, the heave compensation system further comprises a pedestal member releasably coupled to both an end of the cylinder assembly and the first frame of the support structure, wherein the pedestal member is configured to be laterally displaced relative to the support structure in response to the cylinder assembly being lowered from the first lifting lug to the rig floor through the internal volume of the derrick. In some embodiments, the heave compensation system further comprises a vessel assembly supported by the first frame of the support structure, wherein the vessel assembly is configured to provide pressurized fluid to the cylinder assembly, wherein the transport assembly is configured to releasably couple with the vessel assembly via a cable extending through a second lifting lug of the transport assembly, and wherein the transport assembly is configured to support the weight of the vessel assembly in response to the vessel assembly being lowered from the second lifting lug to the rig floor through the internal volume of the derrick. In certain embodiments, the first frame of the support structure comprises a roller configured to guide the vessel assembly in response to the lowering of the vessel assembly towards the rig floor. In certain embodiments, the transport assembly of the heave compensation system comprises a plurality of laterally spaced first support beams, wherein each first support beam extends longitudinally from the second frame of the support structure, and a laterally extending third support beam disposed on the plurality of laterally spaced first support beams, wherein the second lifting lug extends from the third support beam. In some embodiments, the heave compensation system further comprises an active heave compensation actuator pivotably coupled to the crown block, wherein the actuator is configured to longitudinally displace the crown block relative to the support structure in response to a heave movement of the vessel, wherein the transport assembly is configured to releasably couple with the actuator via a cable extending through a third lifting lug of the transport assembly, and wherein the transport assembly is configured to support the weight of the cylinder assembly in response to the cylinder assembly being lowered from the third lifting lug to the rig floor through the internal volume of the derrick. In certain embodiments, the heave compensation system further comprises a pair of laterally spaced active heave support beams coupled to the second frame of the support structure, wherein each active heave support frame comprises a slot extending therein, and a guide plate coupled to the actuator, wherein, in response to the lowering of the actuator to the rig floor, the guide plate is configured to be displaced through the slots of the active heave support beams to guide the actuator towards the rig floor.

An embodiment of a method for removing a component of a heave compensation system comprises decoupling a cylinder assembly from a crown block, the cylinder assembly configured to displace the crown block in response to a heave motion of a drilling vessel supporting the heave compensation system, coupling the cylinder assembly to a support structure via a cable, and using the cable to lower the cylinder assembly through an internal volume of a derrick of the drilling vessel to a rig floor of the drilling vessel. In some embodiments the method further comprises displacing the cylinder assembly through an open area in a support frame of the support structure. In some embodiments the method further comprises engaging the cylinder assembly with a roller and a guide beam as the cylinder assembly is lowered to the rig floor. In certain embodiments the method further comprises decoupling a pedestal member from an end of the cylinder assembly and from a support frame of the support structure.

An embodiment of a method for removing a component of a heave compensation system comprises decoupling a cylinder of an active heave compensation actuator from a support structure, wherein the active heave compensation actuator is configured to displace a crown block relative to the support structure in response to a heave movement of a vessel supporting the heave compensation system, coupling a guide plate to the cylinder of the actuator, and displacing the guide plate through a slot extending into an actuator support beam of the support actuator to guide the displacement of the actuator through the support structure. In some embodiments the method further comprises coupling the actuator to the support structure via a cable, and using the cable to lower the actuator through an internal volume of a derrick of the drilling vessel to a rig floor of the drilling vessel. In some embodiments the method further comprises decoupling the actuator from a crown block. In certain embodiments the method further comprises decoupling a collar of the actuator from the actuator support beam.

DETAILED DESCRIPTION

In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals. The drawing figures are not necessarily to scale. Certain features of the disclosed embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present disclosure is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.

Unless otherwise specified, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Any use of any form of the terms “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.

Referring now toFIG. 1, a schematic view of an offshore drilling system10including a heave compensation system100is shown. Drilling system10has a central or longitudinal axis15and generally includes a floating vessel or semi-submersible drilling rig11including a rig floor12and a derrick or mast14. Although in this embodiment vessel11comprises a semi-submersible drilling rig, in other embodiments vessel11may comprise other types of vessels known in the art, including drilling ships and the like. In this embodiment, derrick14has a first or longitudinally (respective longitudinal axis15) lower end14adisposed at the rig floor12, and a second or longitudinally upper end14blongitudinally spaced from lower end14a. In this arrangement, heave compensation system100of drilling system10is disposed at the longitudinally upper end14bof derrick14. Additionally, derrick14comprises a four-sided structure (only a single side shown inFIG. 1), with each side extending between the upper and lower longitudinal ends14aand14b. The volume encompassed within or defined by the four sides of derrick14forms a derrick volume or space16.

Drilling system10additionally includes a string of drill pipes connected together by drill pipe joints or tubular members so as to form a drill string18extending subsea from platform11. Enclosed within the derrick volume16is a travelling block20coupled with a drive22(e.g., a top drive). As will be discussed further herein, travelling block20is supported by a plurality of drilling cables24suspended from a crown block of heave compensation system100, forming a block and tackle arrangement. Travelling block20and drive22are configured to longitudinally displace and apply torque, respectively, to a longitudinally upper end of drill string18. Connected to the lower end of the drill string18is a bottom hole assembly (BHA)17and a drill bit26. The bit26is rotated by rotating the drill string18via drive22and/or with a downhole motor (e.g., downhole mud motor) disposed in the BHA17.

Drilling fluid, also referred to as drilling “mud,” is pumped by mud recirculation equipment (e.g., mud pumps, shakers, etc.) (not shown) disposed on the rig floor12of vessel11. Particularly, the drilling mud is pumped at a relatively high pressure and volume through a drilling kelly coupled with drive22and down the drill string18to the drill bit26. The drilling mud exits the drill bit26through nozzles or jets in face of the drill bit26. The mud then returns to the vessel11at the sea surface21via an annulus28between the drill string18and the borehole23, through a blowout preventer (BOP)19at the sea floor25, and up an annulus27between the drill string18and a riser30extending through the sea29from the blowout preventer19to the vessel11. At the sea surface21, the drilling mud is cleaned and then recirculated by the recirculation equipment. In some applications, the drilling mud is used to cool the drill bit26, to carry cuttings from the base of the borehole to the vessel11, and to balance the hydrostatic pressure in the subterranean formation extending beneath sea floor25.

Referring toFIGS. 1, 2A, and 2B, an embodiment of the heave compensation system100ofFIG. 1is shown. Heave compensation system100has a longitudinal axis coaxial with longitudinal axis15and is disposed at the longitudinally upper end14bof derrick14. In the embodiment shown inFIGS. 2A and 2B, heave compensation system100generally includes a support structure or frame102, a crown block200, a pair of stabilization or rocker arm assemblies250, a pair of compensator cylinder assemblies300, an accumulator assembly400, a plurality of compensation vessel or cylinder assemblies500, and an active heave compensation assembly600. In this embodiment, frame102comprises a first or longitudinally lower support frame or water table104, a second or upper support frame or top frame150, and a longitudinally extending support structure140extending longitudinally between and coupling the lower frame102and the upper frame150. Lower support frame104is coupled to the longitudinally upper end14bof derrick14while upper support frame150is disposed at or defines a longitudinally upper end of vessel11.

Crown block200of heave compensation system100is disposed within support frame102and is permitted to travel or be displaced longitudinally relative support frame102, derrick14, and rig floor12to compensate for longitudinal movement or heave of vessel11. Crown block200is coupled with travelling block20shown inFIG. 1via drilling cables24(not shown inFIGS. 2A, 2B) in a block and tackle arrangement such that travelling block20is suspended from crown block200. In this arrangement, heave compensation provided to crown block200via relative longitudinal movement between crown block200and support frame102is also provided to travelling block20and the drill string18coupled thereto.

Stabilization assemblies250of heave compensation system100are each configured to reduce weight-on-bit (e.g., weight on drill bit26ofFIG. 1) caused by compression and decompression of fluid of heave compensation system100as crown block200moves longitudinally relative support frame102. In the embodiment shown inFIGS. 2A, 2B, each stabilization assembly250comprises a first rocker arm252, and a second rocker arm254comprising a pair of sheaves256. Further, in this embodiment stabilization assemblies engage a shared stabilization cable258that engages the sheaves256of each assembly250. A first end of the first arm252is pivotably coupled to the lower frame104of support frame102while a second end of first arm252is pivotably coupled to second arm254. Each end of second arm254is coupled to a sheave256, where sheaves256are permitted to rotate relative second arm254. In addition, one end of second arm254is pivotably coupled to crown block200, thereby forming an articulated or pivotable connection between crown block200and support frame102.

The stabilization cable258shared by stabilization assemblies250may be connected to a drawworks (not shown) at a first end, and fixed at another end to the rig floor12of vessel11at a second end. Stabilization cable passes around and engages the sheaves256of a first stabilization assembly250, passes between the crown block200and the traveling block20, and passes through the second stabilization assembly250. In this configuration, stabilization cable258may be adjusted as desired to control the movement of the crown block200with respect to the traveling block20utilizing the pair of stabilization assemblies250of the motion compensation system100. Although in the embodiment shown inFIGS. 2A, 2Bheave compensation system100comprises the pair of stabilization assemblies250, in other embodiments system100may not include stabilization assemblies250, and instead, may include other mechanisms for stabilizing the displacement of crown block200.

As will be discussed further herein, cylinder assemblies300, accumulator assembly400, and the plurality of vessel assemblies500are configured to provide passive heave compensation functionality to the crown block200and the components coupled thereto, such as travelling block20, drive22, and drill string18. In the embodiment shown inFIGS. 2A, 2B, cylinder assemblies300, accumulator400, and vessel assemblies500are each physically supported by and extend longitudinally from the lower frame104of support frame102. In other embodiments, vessel assemblies500may be disposed and physically supported in alternative ways. For instance, in some embodiments vessel assemblies500may be supported by support members extending from support structure140. In still other embodiments, vessel assemblies500may be mounted on the rig floor (e.g., rig floor12shown inFIG. 1). In the embodiment shown inFIGS. 2A and 2B, each vessel assembly500is filled with a pressurized gas or compressible fluid (e.g., air, etc.) and is fluidically coupled with accumulator400via a gas valve assembly460disposed at a first or longitudinally upper end of accumulator400. Gas valve assembly460comprises one or more actuatable valves and fluid conduits for providing selective fluid communication between vessel assemblies500and accumulator400. In addition, accumulator400is fluidically coupled with each cylinder assembly300via a liquid valve assembly470. Particularly, accumulator400is at least partially filled with a liquid or incompressible fluid (e.g., water, etc.) with liquid valve assembly470comprising one or more actuatable valves and fluid conduits for providing selective fluid communication between liquid disposed in accumulator400and each cylinder assembly300.

Crown block200of heave compensation system100is physically supported and suspended from each cylinder assembly300. In the embodiment shown inFIGS. 2A, 2B, each cylinder assembly300comprises a cylinder head pendulum340pivotably coupled to a first or upper end320aof a piston320extending longitudinally from a cylinder302in which the piston320is reciprocally disposed. In turn, the pendulum340of each cylinder assembly300is pivotably coupled with a pair of tie rods342that extend longitudinally from pendulum340to crown block200. In other words, the tie rods342of each cylinder assembly300comprise a first or upper end pivotably coupled with pendulum340and a second or lower end pivotably coupled with crown block200. In addition, a longitudinally lower end of the cylinder302of each cylinder assembly300is releasably coupled to the lower frame104of support frame102, restricting relative longitudinal movement between cylinder302and support frame102. In this arrangement, vertical or longitudinal displacement of the piston320of each cylinder assembly300respective its corresponding cylinder302causes corresponding longitudinal displacement of crown block200relative support frame102.

Active heave compensation assembly600of heave compensation system100is configured to provide active heave compensation functionality to the crown block200and the components coupled thereto, such as travelling block20, drive22, and the drill string18(each shown inFIG. 1). In the embodiment shown inFIGS. 2A, 2B, active heave compensation assembly600generally includes an actuator assembly602generally including an outer cylinder or barrel603and a retractable piston610reciprocally disposed in cylinder603. Actuator602extends longitudinally from the upper frame150of support frame102, and a lower longitudinal end610bof piston610pivotably couples to an upper surface of crown block200at a hinged connection200H. In this arrangement, the longitudinal position of crown block200may be controlled via the selective displacement of piston610of actuator602within cylinder603.

In this embodiment, active heave compensation assembly600further includes a plurality of pressure vessels620for providing pressurized fluid to cylinder603and a controller or motion reference unit (MRU)630(shown schematically inFIG. 1) for controlling the actuation of active heave compensation assembly600. In certain embodiments, MRU630comprises one or more sensors for measuring the heave motion of vessel11(shown inFIG. 1) for actively compensating against such measured motion via the controlled displacement of piston610. Although in the embodiment shown inFIGS. 2A, 2Bheave compensation system100is shown as comprising active heave compensation assembly600, in other embodiments, heave compensation system100may not include active heave compensation assembly600, and instead, may comprise a passive heave compensation assembly alone.

Referring toFIG. 3, a schematic drawing of a portion of the heave compensation system100is shown for illustrating at least some of the functionality provided by system100. As discussed above, in certain embodiments heave compensation system100comprises crown block200, compensator cylinder assemblies300, accumulator assembly400, and vessel assemblies500. In some embodiments, crown block200is coupled to the drill string18, such as by having the crown block200coupled to the drill string18through the traveling block20and the drive22, as shown in the embodiment illustrated inFIG. 1, and/or may include one or more other connection devices coupled therebetween.

In the arrangement shown inFIG. 3, the piston320of each cylinder assembly300includes a longitudinally lower end320bdisposed within and in sealing engagement with the corresponding cylinder302, dividing cylinder302into a first side or chamber304extending between a first or longitudinally upper end302aof cylinder302and the lower end320bof piston320, and a second side or chamber306extending between the lower end320bof piston320and a longitudinally lower end302bof cylinder302. In some embodiments, cylinder assemblies300comprise plunger-type cylinder assemblies where fluid communication is provided between chambers304and306of each cylinder302. In the embodiment shown inFIG. 3, the lower end302bof each cylinder302is in fluid communication with accumulator400via liquid valve assembly470. In addition, accumulator400includes a first or longitudinally upper end400a, a second or longitudinally lower end400b, and a floating piston402disposed within and sealingly engaging an inner surface of accumulator400. Piston402divides accumulator400into a first side or chamber404extending between upper end400aof accumulator400and piston402, and a second side or chamber406extending between piston402and the lower end400bof accumulator400.

In the embodiment shown inFIG. 3, first chamber404of accumulator is filled with a compressible fluid, such as a gas, while second chamber406is filled with a noncompressible fluid, such as a liquid. In this configuration, liquid valve assembly470extends between the lower end400bof accumulator400and the lower end302bof each cylinder302, providing selective fluid communication of a liquid between second chamber406of accumulator400and the second chamber306of each cylinder302. In addition, gas valve assembly460extends between vessel assemblies500and the upper end400aof accumulator400, providing for selective fluid communication of a gas between vessel assemblies500and the first chamber404of accumulator400.

In the arrangement described above, movement of crown block200in a longitudinally downwards direction (i.e., towards rig floor12of vessel11shown inFIG. 11) causes pistons320to be displaced towards the lower end302bof their respective cylinders302, decreasing the volume of the second chamber306of each cylinder302. In response to the decrease in volume of second chambers306, liquid disposed in second chambers306is displaced through liquid valve assembly470and into the second chamber406of accumulator400. In response to the influx of liquid into the second chamber406of accumulator400, piston402of accumulator400is displaced towards longitudinally upper end400a, thereby increasing fluid pressure within first chamber404by compressing the gas disposed therein. In this manner, the compression of gas disposed in the first chamber404of accumulator400provides a low frequency damping effect on the longitudinal movement or displacement of crown block200.

Referring toFIGS. 4A-5, an embodiment of the support frame102of heave compensation system100is shown. Support frame comprises a first pair of lateral sides102aand a second pair of lateral sides102b, where sides102aand102beach intersect at edges extending therebetween. In this embodiment, lower frame104of support frame102comprises a rectangular support frame106extending along lateral sides102aand102b, and a pair of laterally spaced support members108that extend between the second lateral sides102bof rectangular frame106. In addition, lower frame104comprises a pair of sheave support members110, each supporting a sheave256of a stabilization assembly250. Particularly, each sheave support member110extends laterally from a lateral support member108to a first side102aof rectangular frame104.

In this arrangement, a first or central open area112extends between the pair of lateral support members108, a pair of second open areas114extend between a lateral side102bof rectangular frame106and a sheave support member110, and a pair of third open areas116extend between an opposing lateral side102bof rectangular frame106and a sheave support member110, as shown particularly inFIG. 5. In the embodiment shown inFIGS. 4A-5, one of the second open areas114includes a roller118that extends diagonally between a lateral side102bof rectangular frame106and a lateral support member108. Similarly, one of the third open areas116includes a roller118extending diagonally between a lateral side102bof rectangular frame106and a lateral support member108. Additionally, the second open area114and the third open area116that include a roller118also includes a longitudinally extending guide rail120. In some embodiments, guide rail120comprises a guide rail for a dolly of a top drive (e.g., drive22shown inFIG. 1) of drilling system10. In this embodiment, guide rail120is positioned to allow the traversal of components of heave compensation system100through open areas of lower frame104. As will be discussed further herein, rollers118facilitate the removal and installation of components of heave compensation system100from support frame102, such vessel assemblies500.

In the embodiment shown inFIGS. 4A and 4B, upper frame150of support frame102generally includes a first or inner rectangular support frame152and a second or outer rectangular support frame180, where inner rectangular frame152is disposed within outer rectangular frame180. The inner rectangular frame152includes an upper surface154and a plurality of lifting lugs156extending therefrom, where each lifting lug156is disposed at a corner of inner rectangular frame152. Inner rectangular frame152also includes a pair of laterally spaced arched or C-shaped members or frames158coupled to upper surface154and extending between the first sides102aof inner rectangular frame152. In this embodiment, each C-frame158includes a pair of longitudinally spaced slots159for allowing the removal of actuator602, as will be discussed further herein. Additionally, upper frame150includes a plurality of laterally spaced support members170extending between the first sides102aof inner rectangular frame152and the first sides102aof outer rectangular frame180. The arrangement of rectangular frames152,180, and lateral support members170forms a plurality of open areas in upper frame150of support frame102. Particularly, a pair of first open areas171extend between the second sides102bof inner frame152and the second sides102bof outer frame180; a pair of second open areas173extend between a first pair of adjacent lateral support members170, and a pair of third open areas175extend between a second pair of adjacent lateral support members170.

In the embodiment shown inFIGS. 4A and 4B, upper frame150of support frame102includes a pair of component transport assemblies172configured to facilitate the removal and installation of components of heave compensation system100from support frame102. Particularly, each transport assembly172includes a plurality of laterally spaced L-shaped support frames or brackets174, each comprising a longitudinally extending support member and a laterally extending member coupled to an upper longitudinal end of the longitudinally extending member. In this embodiment, each transport assembly172includes three laterally spaced L-frame174, with a central L-frame174extending longitudinally from the upper surface154of the inner rectangular frame154, and the pair of laterally outer L-frames174extending longitudinally from a pair of lateral support members170.

In addition, each transport assembly172includes a first or inner laterally extending support beam176and a second or outer laterally extending support beam178. Specifically, the inner support beam176of each assembly172extends between a laterally outer L-frame174to the centrally disposed L-frame174of the assembly172, with inner support beam176disposed at the laterally inner end (i.e., the end closest the longitudinal axis15) of the L-frames174. In addition, the inner support beam176of each assembly172is pivotably coupled to the central L-frame174at a hinged connection176H, providing for relative rotation between inner support beam176and the L-frame174. Conversely, the outer support beam178of each assembly172extends between the pair of laterally outer L-frames174of the assembly172, and is disposed on the laterally outer end of the L-frames174. Additionally, a longitudinally lower surface of the inner support beam176of each transport assembly172includes a pair of lifting lugs177extending therefrom. In other embodiments, the inner support beam176of each transport assembly172may include varying numbers of lifting lugs177.

Support structure140of frame102extends longitudinally between lower frame104and upper frame150, thereby providing structural support to upper frame150. In the embodiment shown inFIGS. 4A and 4B, support structure140includes a pair of first angled supports142extending longitudinally first sides102aof frame102, and a pair of second angled supports144extending longitudinally along second sides102bof frame102. Additionally, each pair of second angled supports144includes a lateral cross-support member146extending laterally therebetween to couple together the each pair of second angled supports144. As will be discussed further herein, the cross-support146of each pair of second angled supports144is releasably coupled with its corresponding pair of second angled supports144, allowing cross-support146to be removed therefrom.

Referring toFIGS. 6-11, a method of removing the vessel assemblies500from heave compensation system100of drilling system10is shown. For the sake of clarity, some components of heave compensation system100are hidden inFIGS. 6-10B. Additionally, also for the sake of clarity, the vessel assemblies500shown in6and8-10B are labeled separately as vessel assemblies500a,500b,500c, and500d. During operation of drilling system10, it may become necessary to remove and/or replace components of heave compensation system100, such as in the event of a failure or other issue involving one of the components of system100. In the embodiment shown inFIGS. 6-10B, heave compensation system100is configured to facilitate the removal and/or replacement of components of system100in-situ. In other words, system100is configured to provide for the removal and/or replacement of components of system100(including cylinders300, vessels500, assembly600, etc.) while vessel10is deployed at sea. In this manner, components of heave compensation system100may be replaced without bringing vessel11to shore, significantly reducing the costs incurred in replacing components of system100.

FIGS. 6-11particularly illustrate, as an example of the functionality provided by heave compensation system100, the removal of a vessel assembly500from the support frame102of heave compensation system100. As shown particularly inFIGS. 7A and 7B, in this embodiment each vessel assembly500includes a cylindrical body or cylinder502including first or upper longitudinal end502a(shown inFIGS. 7A and 7B), a second or lower longitudinal end502b. Each cylinder assembly500additionally includes a fluid coupler502disposed at upper end502a, a lower bracket mount506disposed at lower end502b, and an upper bracket mount508disposed at upper end502a. Fluid coupler504of each vessel assembly500is configured to provide fluid communication between the vessel500and gas valve assembly460. Lower bracket mount506of each vessel500releasably couples with a vessel assembly mount510(shown inFIG. 6) of the lower frame104of support frame102to physically support vessels500. Further, upper bracket assembly508is configured to support the upper end500aof each vessel500and releasably couple the vessel500with upper frame150of support frame102. In this embodiment, the upper bracket assembly508of each vessel assembly500includes a plurality of apertures509disposed therein.

As shown particularly inFIG. 11, each transport assembly172of heave compensation system100includes additional lifting lugs or members for providing physical support for components of system100as they are installed or uninstalled from system100and drilling system10. In the embodiment shown inFIG. 11, the outer support beam178of each transport assembly172includes a pair of longitudinally spaced upper lifting lugs183aand183bthat extend from a lower surface of the outer support beam178. In other embodiments, the outer support beam178of each transport assembly172may include a plurality of lifting lugs disposed at the location of upper lifting lug183b. Additionally, each L-frame174of each transport assembly172includes at least one upper lifting lug185(labeled as185a,185b, and185cinFIG. 11) extending from a lower surface thereof. In this configuration, upper lifting lugs183a,183b,185b, and185care each positioned such that they substantially align with a longitudinal axis of a corresponding vessel assembly500. In this manner, upper lifting lugs183a,183b,185b, and185cmay be used to lift and lower their corresponding vessel assembly500vertically without needing to pivot the upper end of each vessel assembly500towards its respective lifting lug.

As shown particularly inFIG. 6, in this embodiment, prior to removal each vessel assembly500of heave compensation system100is releasably coupled to the lower frame104and upper frame150of support frame102. In the arrangement shown inFIG. 6, vessel500ais disposed proximal the second open area114of lower frame104that includes roller118(shown inFIGS. 9B and 10B), while vessel500dis disposed distal the second open area114that includes roller118. To remove the vessel assembly500afrom support frame102, the fluid coupler of vessel500ais decoupled from gas valve assembly460and the lower bracket506is decoupled from the mount510of lower frame104. In certain embodiments, the lower bracket506of each vessel assembly500(shown as assemblies500a-500dinFIG. 6) is decoupled from mount510. In this embodiment, mount510of lower frame104may additionally be disassembled. Further, the cross-support146of the pair of second angled supports144disposed proximal vessel assemblies500a-500dis removed from support structure140to provide additional space for manipulating vessel assembly500a.

As shown particularly inFIG. 8, following the decoupling of vessel assembly500afrom gas valve assembly460and the decoupling of vessel500afrom mount510, vessel assembly500amay be coupled to either upper lifting lug183a(as shown inFIG. 8) or one of the upper lifting lugs185disposed proximal vessel assemblies500a-500dvia a chain hoist or cable514releasably coupled to upper bracket508via holes509. In this configuration, upper lifting lug183ais disposed near the longitudinal end of support beam178proximal vessel assembly500a. With vessel500acoupled to upper lifting lug183a, the weight of vessel500amay be supported by outer support beam178and the L-supports174of the transport assembly172disposed proximal vessel assemblies500a-500d. In this position, the upper mount506of vessel assembly500ais decoupled or released from the upper frame104, allowing vessel assembly500ato move or be displaced relative support frame102.

With vessel assembly500ahanging from the hoist514coupled to upper lifting lug183a, the lower end502of the cylinder502of vessel assembly500ais pivoted towards the second open area114that includes roller118, as indicated by arrow516inFIG. 8. In some embodiments, soft slings or other tools or mechanisms are used to pivot or rotate the lower end502bof the cylinder502of vessel assembly500a. As shown particularly inFIGS. 9A and 9B, once the lower end502bof vessel assembly500ahas been pivoted in the direction of second open area114, vessel assembly500ais lowered a first longitudinal distance towards lower frame104and second open area114. Additionally, as vessel assembly500ais lowered from upper frame150, the cylinder502of vessel500is physically engaged and guided by roller118of lower frame104. Following the lowering of vessel assembly500aby the first longitudinal distance, the hoist514is coupled to a lower lifting lug181disposed directly beneath upper frame150, where lower lug181is positioned over the second open area114that includes roller118.

Once hoist514is coupled to lower lifting lug181, the weight of vessel assembly500ais transferred from upper lifting lug183aof outer support beam178to lower lifting lug181, thereby allowing the remaining end of hoist514coupled to upper lifting lug183ato be disconnected therefrom and coupled with lower lifting lug181, as shown particularly inFIGS. 10A and 10B. As the hoist514is transferred from upper lifting lug183ato lower lifting lug181, vessel assembly500ais displaced longitudinally until it is substantially aligned with the second open area114of the lower frame104that includes rollers118. In this position, vessel assembly500ais further lowered longitudinally downwards through second open area114of lower frame104until vessel assembly500ais disposed at the rig floor12of vessel11(shown inFIG. 1), where vessel assembly500amay be stored or refurbished for future installation in heave support system100. Particularly, to reinstall vessel assembly500ain system100, the method described above is performed in substantially reverse order, with vessel500raised via lower lug181and hoist514, transferred to upper lifting lug183aand then recoupled with mount510and gas valve assembly460.

Once vessel assembly500ahas been removed from heave compensation system100as described above, remaining vessel assemblies500b-500dmay be displaced in the direction of position previously occupied by assembly500autilizing upper lifting lugs183a,183b,185b, and185c, indicated generally by arrow518inFIG. 11. For instance, upper lifting lugs185band183amay be utilized for manipulating cylinder assembly500b, and upper lifting lugs183b,185b, and183amay be utilized for manipulating cylinder assembly500c. Thus, following the removal of vessel assembly500a, vessel500bmay be shifted into the position previously occupied by vessel500a, vessel500cmay be shifted to the position previously occupied by vessel500b, and vessel500dmay be shifted to the position previously occupied by vessel500c. Following this procedure, vessel assembly500bmay be lowered to the rig floor12in a manner similar to the method described above with respect to vessel assembly500a.

Referring toFIGS. 12A-15B, a method for removing cylinder assemblies300from heave compensation system100is shown. Particularly, the method illustrated inFIGS. 12A-15Bprovides for the removal and/or installation of cylinder assemblies300from heave compensation system100in-situ, such that vessel11does not need to be brought to shore in order to replace cylinder assemblies300. For the sake of clarity, some components of heave compensation system100are hidden inFIGS. 12A-15B. In this embodiment, each cylinder assembly300includes a guide rail310extending along the longitudinal length of the cylinder302of each cylinder assembly300, where guide rail310is configured to guide or direct the longitudinal displacement of cylinder assemblies300during their removal, as will be discussed further herein. Additionally, each cylinder assembly300includes a support member or pedestal312releasably coupled to the lower end302bof the cylinder302. Each pedestal312is in turn releasably coupled with the lower frame104of support frame102to couple each cylinder assembly300to support frame102. Particularly, each pedestal312is positioned such that it extends laterally across the central open area112(shown particularly inFIG. 4A) of lower frame104such that each lateral end is supported on and releasably coupled with a lateral support member108. Guide rails310extend longitudinally past the lower end302bof cylinders302and along pedestals312, and thus, are greater in longitudinal length than cylinders302.

As shown particularly inFIGS. 12A and 12B, to remove cylinder assemblies300from heave compensation system100, the inner support beam176of each transport assembly172is rotated about its respective hinged connection176H until it aligns with or intersects the longitudinal axis of a corresponding cylinder assembly300of system100(indicated by arrows318inFIG. 12B). In this position, the lifting lugs177of each inner support beam176are disposed longitudinally above a corresponding cylinder assembly300. Following the rotation of the inner beam176of each transport assembly172shown inFIGS. 12A and 12B, the tie rods342of each cylinder assembly300are decoupled from their respective pendulum340and pivoted laterally about their lower ends towards a support surface of upper frame150(indicated generally by arrows380inFIG. 13) for securement thereto. In certain embodiments, decoupling tie rods342from their respective pendulum340comprises removing each pendulum340from the upper end320aof the piston320its respective cylinder assembly300, as shown generally by arrows382inFIG. 13. In some embodiments, this process comprises disassembling pins releasably coupling tie rods342with pendulum340and pendulum340with the upper end320aof piston320. In some embodiments, a chain hoist or other mechanism supported by lifting lugs177may be used to support pendulum340and tie rods342during their removal and/or decoupling.

Once the upper end of each tie rod342has been decoupled from its respective pendulum340, and the pendulum340has been removed from its corresponding cylinder assembly300, a chain hoist or cable360is coupled between the longitudinal upper end302aof each cylinder302and the lifting lug177of a corresponding inner support beam176, as shown inFIG. 14. In this arrangement, the weight of each cylinder assembly300is supported by the upper frame150via the corresponding inner support beam176and L-frame174coupled therewith. In this configuration, pedestals312are no longer required to support the weight of cylinder assemblies300. Thus, following the coupling of each hoist360to its respective cylinder assembly300, each pedestal312is removed from heave compensation system100via decoupling the pedestal312from the lower end302bof its respective cylinder302and from the lower frame104of support frame102, as indicated generally by arrow384inFIG. 14. In this embodiment, pedestals312are removed by displacing them laterally until they are disposed directly adjacent a second side102bof lower frame104. In this position, each pedestal312no longer extends across central open area112of lower frame104, providing space or access for the displacement of cylinders302therethrough.

In some embodiments, decoupling pedestals312from cylinders302and lower frame104comprises unbolting (e.g., removing threaded fasteners) pedestals312from both the lower end302bof its corresponding cylinder302and from the lower frame104of support frame102. In some embodiments, pedestals312may be laterally displaced (as indicated by arrows384) from cylinder assemblies300using a chain block, hydraulic tool, or other such mechanism or tool. In some embodiments, this process further comprises disassembling piston lugs disposed at the upper end302aof each cylinder302.

Following the decoupling and subsequent displacement of pedestals312to the second sides102bof lower frame104, each cylinder302(including its respective piston320) is lowered through the vacated central open area112of lower frame104via hoists360suspended from the lifting lugs177of inner support beams176, as indicated by arrows386ofFIG. 15Aand shown inFIGS. 15A and 15B. As cylinders302are lowered through lower frame104, guide rails310are used to guide and prevent damage from occurring to their respective cylinder302through the central open area112of lower frame104. Once cylinders302are displaced below the lower fame104of support frame102, they are further lowered vertically until they reach the rig floor12of vessel11. Cylinders302may then be refurbished or replacement cylinders302(including pistons320) may be displaced to support frame102for coupling with heave compensation system100. In this process, the new cylinders302may be displaced and assembled with heave compensation system100in a procedure similar to, but reversed from, the method described above for decoupling and removing cylinders302and their respective pistons320from heave compensation system100. This process may be accomplished in-situ without displacing vessel11to the shore.

Thus, an embodiment of a method for removing a component of a heave compensation system (e.g., system100) comprises decoupling a cylinder assembly (e.g., cylinder assembly300) from a crown block (e.g., crown block200), the cylinder assembly configured to displace the crown block in response to a heave motion of a drilling vessel (e.g., vessel11) supporting the heave compensation system, coupling the cylinder assembly to a support structure (e.g., support frame102) via a cable (e.g., cable360); and using the cable to lower the cylinder assembly through an internal volume (e.g., internal volume16) of a derrick (e.g., derrick14) of the drilling vessel to a rig floor (e.g., rig floor12) of the drilling vessel.

Referring toFIGS. 16-25, a method for removing active heave compensation assembly600from heave compensation system100is shown. Particularly, the method illustrated inFIGS. 16-25provides for the removal and/or installation of actuator602from heave compensation system100in-situ such that vessel11does not need to be brought to shore in order to replace actuator602. For the sake of clarity, some components of heave compensation system100are hidden inFIGS. 16-25. In the embodiment shown inFIGS. 16-25, active heave compensation assembly600includes a support structure640extending longitudinally from the upper frame150of support frame102, where support structure640includes a plurality of ladders642for providing access to actuator602of assembly600. In this embodiment, ladders642are mounted to actuator602via a plurality of longitudinally spaced brackets614disposed on an outer surface of actuator602. Additionally, assembly600includes a plurality of support cables644coupled between cylinder603of actuator assembly602and the upper frame150for securing actuator602into a substantially longitudinal position with actuator602extending along longitudinal axis15. Further, cylinder603of actuator602includes a first or longitudinally upper end603a, a second or longitudinally lower end603b, and a radially outwards extending collar604disposed at lower end603b. Cylinder603is releasably coupled to active heave compensation actuator support beams or C-frames158of upper frame150via collar604and a plurality of releasably coupled brackets606(shown particularly inFIG. 18B). In this arrangement, brackets606are releasably coupled to both C-frames158and the collar604of cylinder603, thereby releasably coupling collar604and cylinder603of actuator602to C-frames158and upper frame150of support frame102, restricting relative longitudinal movement between cylinder602and upper frame150.

As shown inFIG. 16, to remove actuator602from heave compensation system100the crown block200is initially displaced into a longitudinally upper position, as indicated generally by arrows680. In certain embodiments, crown block200is displaced into the longitudinally upper position by retracting piston610longitudinally upwards into cylinder603, where the longitudinally lower end610bof piston610is releasably coupled with the upper end of crown block200at hinged connection200H. In some embodiments, crown block200is displaced into the longitudinally upper position by extending compensator cylinder assemblies300. Following the displacement of crown block200into the longitudinally upper position shown inFIG. 16, ladders642of support structure640are removed to provide additional access to actuator602, as indicated generally by arrows682inFIG. 17. In some embodiments, ladders642are unbolted from structure640and removed using soft slings or other mechanisms, and stored on upper frame150of support frame102. While in this embodiment a method for removing actuator602includes removing ladders642, in other embodiments, actuator602may be removed without removing ladders642. In other embodiments, active heave compensation assembly600may not include ladders642.

Once ladders642have been removed from structure640, actuator602is decoupled from the upper frame150of support frame102to permit relative longitudinal movement between actuator602and support frame102. In this embodiment, brackets606are decoupled from collar604of cylinder603and from C-frames158of upper frame150, thereby decoupling actuator602from support frame102, and removed from C-frames158, as indicated generally by arrows684inFIGS. 18A and 18B. In certain embodiments, brackets606are unbolted from collar604and C-frames158. Once brackets606are decoupled from collar604and C-frames158, collar604and cylinder603are permitted to travel between the lateral open area or space extending between the pair of C-frames158. In this configuration, the tension provided against actuator602by support cables644maintains actuator602in a substantially longitudinal position aligned with longitudinal axis15.

Following the decoupling and removal of brackets606from the collar604of cylinder603, a first or lower pair of circumferentially spaced and longitudinally extending guide plates612is releasably coupled with the cylinder603to facilitate guiding cylinder603through C-frames158of upper frame150. In this embodiment, each pair of guide plates612are clamped to cylinder603of actuator602, and thus, do not rely on mounts or brackets disposed on actuator603for coupling with cylinder603. In this manner, guide plates612may be flexibly positioned along the longitudinal length of actuator602. In this embodiment, the lower pair of guide plates612extend longitudinally upwards from a lower end at the lower end603bof cylinder603at collar604to an upper end disposed between the upper and lower ends603aand603b, respectively, of cylinder603.

As shown particularly inFIG. 20, once the lower pair of guide plates612have been coupled with cylinder603, crown block200and actuator602are lowered from the longitudinally upper position (indicated generally by arrow686) towards the rig floor12(shown inFIG. 1) to provide access to the upper end603aof cylinder603from structure640to complete the assembly or coupling of guide plates612to cylinder603of actuator602. Additionally, support cables644are decoupled or released from the cylinder603of actuator602as indicated generally by arrows688. With support cables644released from cylinder603, actuator602is held or retained in the longitudinally extending position (aligned with longitudinal axis15) via engagement between guide plates612and C-frames158. As shown particularly inFIG. 21B, guide plates612are received within the slots159of each C-frame158, restricting actuator602from pivoting about hinged connection200H out of axial alignment with longitudinal axis15.

As shown particularly inFIGS. 21A and 21B, with support cables644released from cylinder603and the lower pair of guide plates612coupled to cylinder603, the crown block200and actuator602are further lowered until the upper longitudinal end of the lower pair of guide plates612is disposed adjacent the upper end of C-frames158. In this position, an upper longitudinal pair of additional guide plates612is releasably coupled to the cylinder603of actuator602. In this embodiment, the upper pair of guide plates612extend from a lower end disposed directly adjacent the upper end of the lower pair of guide plates612to an upper end disposed proximal the upper end603aof cylinder603. As discussed above, both the upper and lower pairs of guide plates612are clamped to the outer surface of cylinder603. In some embodiments, guide plates612are clamped to cylinder603using a two half-moon clamp system. In some embodiments, the lower end of each guide plate612of the upper pair of guide plates612is first coupled with cylinder603, and the crown block200and actuator602are additionally lowered towards lower frame104in order to couple the upper end of each guide plate612of the upper pair of guide plates612to the upper end603aof cylinder603.

Once the upper and lower pairs of guide plates612are fully coupled with the cylinder603of actuator602, the crown block200and actuator602are additionally lowered until the upper end603aof cylinder603is disposed proximal the upper end of C-frames158, as shown particularly inFIG. 22. In this position, one or more chain hoists or cables670are releasably coupled between a bracket614of cylinder603and a pair of lifting lugs161of C-frames158. In this embodiment, lifting lugs161are positioned substantially equidistant between the lateral ends of C-frames158that couple with the upper surface156of inner rectangular frame152of the upper frame150. Further, hoists670are coupled to a bracket614longitudinally spaced from both the upper end603aand lower end603bof cylinder603. In this arrangement, actuator602is physically supported by or suspended from C-frames158. Thus, in this arrangement the weight of actuator602is supported by upper frame150of support frame102via hoists670. Following the coupling of hoists670with C-frames158and the cylinder603of actuator602, the lower end610bof piston610is disconnected from crown block200at hinged connection200H, and the crown block200is further lowered into a longitudinally lower or rest position at the lower frame104of support frame102, as shown particularly inFIG. 23. In this position, the upper end of crown block200is longitudinally spaced from the lower end610bof piston610.

As shown particularly inFIG. 24, with actuator602disconnected from crown block200, hoist670is coupled to a bracket614of cylinder603disposed at the upper end603aof cylinder603, and a second chain hoist or cable672is coupled between the lower lug181of upper frame150and a bracket614of cylinder603disposed at collar604proximal the lower longitudinal end603b. In this arrangement, the longitudinally lower end of actuator602(i.e., the lower end610bof piston610) is pivoted (indicated generally by arrow690) towards the second open area114of lower frame104that includes roller118. The lower end of actuator602may be pivoted via a soft sling or other mechanism. Actuator602is then lowered through the second open area114(indicated generally by arrow692inFIGS. 24 and 25) via displacement of hoists670and672with roller118assisting in guiding actuator602therethrough, as shown inFIGS. 24 and 25. Actuator602is then lowered to the rig floor12of vessel11for refurbishment or replacement without needing to bring vessel11to shore. In some embodiments, actuator602may be subsequently replaced and assembled to form active heave compensation assembly60of heave compensation system100in a manner similar to, but reversed from the method described above for removing actuator602from system100.

Thus, an embodiment of a method for removing a component of a heave compensation system comprises decoupling a cylinder (e.g., cylinder603) of an active heave compensation actuator (e.g., actuator602) from a support structure (e.g., support frame102), wherein the active heave compensation actuator is configured to displace the crown block (e.g., crown block200) relative to the support structure in response to a heave movement of the vessel (e.g., vessel11), coupling a guide plate (e.g., guide plates612) to a cylinder of the actuator, and displacing the guide plate through a slot (e.g., slot159) extending into an actuator support beam (e.g., C-frame158) of the support structure to guide the displacement of the actuator through the support structure.

The above discussion is meant to be illustrative of the principles and various embodiments of the present disclosure. While certain embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the disclosure. The embodiments described herein are exemplary only, and are not limiting. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.