CA1205740A - Marine riser tensioner - Google Patents
Marine riser tensionerInfo
- Publication number
- CA1205740A CA1205740A CA000422813A CA422813A CA1205740A CA 1205740 A CA1205740 A CA 1205740A CA 000422813 A CA000422813 A CA 000422813A CA 422813 A CA422813 A CA 422813A CA 1205740 A CA1205740 A CA 1205740A
- Authority
- CA
- Canada
- Prior art keywords
- fluid
- vessel
- pressure chamber
- pipe string
- hydraulic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/12—Underwater drilling
- E21B7/128—Underwater drilling from floating support with independent underwater anchored guide base
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B19/00—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
- E21B19/002—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling
- E21B19/004—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling supporting a riser from a drilling or production platform
- E21B19/006—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling supporting a riser from a drilling or production platform including heave compensators
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B19/00—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
- E21B19/08—Apparatus for feeding the rods or cables; Apparatus for increasing or decreasing the pressure on the drilling tool; Apparatus for counterbalancing the weight of the rods
- E21B19/09—Apparatus for feeding the rods or cables; Apparatus for increasing or decreasing the pressure on the drilling tool; Apparatus for counterbalancing the weight of the rods specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string
Abstract
ABSTRACT OF THE DISCLOSURE
Motion compensating apparatus for maintaining a tension load on a marine riser supported from a floating platform which is subject to movement by wave action and the like. Bending movements induced by the roll and pitch of the vessel are decoupled by a resilient bearing member having an annular section of a substantially spherical laminated body of superposed layers of an elastic material and a relatively inelastic material. A tension load is applied to the riser by a hydraulic actuator which is supported by the resilient bearing member. The actuator includes a displacement compensating cylinder having an adjustable volume of hydraulic fluid presented to a piston in the cylinder for supporting the upper end of the marine riser. The displacement of fluid in the cylinder varies in response to the heave of the vessel to maintain a positive lifting force on the marine riser. An accumulator is connected in fluid communication with the pressure chamber of the hydraulic actuator for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to changes in its volume. Hydraulic fluid leakage past the actuator seals is monitored through a fluid circuit including pressure switches and leakage flow indicators.
Motion compensating apparatus for maintaining a tension load on a marine riser supported from a floating platform which is subject to movement by wave action and the like. Bending movements induced by the roll and pitch of the vessel are decoupled by a resilient bearing member having an annular section of a substantially spherical laminated body of superposed layers of an elastic material and a relatively inelastic material. A tension load is applied to the riser by a hydraulic actuator which is supported by the resilient bearing member. The actuator includes a displacement compensating cylinder having an adjustable volume of hydraulic fluid presented to a piston in the cylinder for supporting the upper end of the marine riser. The displacement of fluid in the cylinder varies in response to the heave of the vessel to maintain a positive lifting force on the marine riser. An accumulator is connected in fluid communication with the pressure chamber of the hydraulic actuator for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to changes in its volume. Hydraulic fluid leakage past the actuator seals is monitored through a fluid circuit including pressure switches and leakage flow indicators.
Description
1,z~5r~
MARINE RISER TENSIC)NER
BACKG:P~OUNI) O~ THE INVENTION
Field of the Invention The present invention relates generally to offshore 5production equipment and in particular to motion compensating appar~tus -for use on a floating platform for supporting a marine riser extencling to the platform from the ocean floor.
Background Art In performing both driUing and production operations on an offshore well, it is necessary to provide a riser connection between the sea floor and a surface facility to provide a stable conduit through which a d~ll ~tring, production fluids and electrical power may be conveyed between the ocean floor and the surface ~acilityO
The surface facility may be a tanker, a drill ship, a barge, a ~loating platform or a pl~tform which is fixed to the ocean floor. The riser must be supported at or near the water surface to prevent collapse.
This is easily accomplished when the surface facility iæ a platform which is fixed to the ocean floor, but a more diIficult problem is presented when the water depth is so great that the surface facility must be floating and hence is not statio~ary~
In rega.rd to ri~ers which are connected to floating structures, substantial forces ACt on the riser which, if not properly compen~ated for, will result in its failure. Of particulnr concern is the excessive str~n which is applied to the riser ~s the result of
MARINE RISER TENSIC)NER
BACKG:P~OUNI) O~ THE INVENTION
Field of the Invention The present invention relates generally to offshore 5production equipment and in particular to motion compensating appar~tus -for use on a floating platform for supporting a marine riser extencling to the platform from the ocean floor.
Background Art In performing both driUing and production operations on an offshore well, it is necessary to provide a riser connection between the sea floor and a surface facility to provide a stable conduit through which a d~ll ~tring, production fluids and electrical power may be conveyed between the ocean floor and the surface ~acilityO
The surface facility may be a tanker, a drill ship, a barge, a ~loating platform or a pl~tform which is fixed to the ocean floor. The riser must be supported at or near the water surface to prevent collapse.
This is easily accomplished when the surface facility iæ a platform which is fixed to the ocean floor, but a more diIficult problem is presented when the water depth is so great that the surface facility must be floating and hence is not statio~ary~
In rega.rd to ri~ers which are connected to floating structures, substantial forces ACt on the riser which, if not properly compen~ated for, will result in its failure. Of particulnr concern is the excessive str~n which is applied to the riser ~s the result of
2 5 upward arld downward heave motions of the vessel in response to :
.
~2~
wave action. Additionallv, the riser i8 subjected to considerable stress inc~uced by water currents which pass around the rlser bul;
which have no particular detrin~ental eEfect on the platforrn. In this si tuation, the ri~er fitring tends to be distorted as it is displaced laterally in one or more directions in response to the underwal:er currents . A further problem associated wit h supporting a production riser ~rom a vessel such as a floatin~ platform or the like is the bending stress induced in the riser by the roll and pitch of the vessel. ~he cornbination of the induced bending stress and the compressive forces which are exerted by the support vessel in respc3nse to wave action will cause rapid destruction of the riser unless the destructive effects are compensated or offset in some way.
Riser tensioner systems have been developed for offshore drilling and production activities to compensate for the rise and fall of a floating platform. Such tensioner systems have commonly comprised hydraulic compensating cylinders connected by cables to the riser at symmet~ically arran~ed tie points. In the course of their travel from cylinders to a Iiser, the cables pass over one or more sheaves and hence are subject to wear. It thus becomes necessary to periodically acljust the cables so that unworn portions of the cable ar~
shifted to the sheave locations and from time to time the cables must be replaced, typically at thirty day illtervals. To make this cable replacement and cylinder repair possible, a duplicate ~iser tensioner system with independellt riser connections has norm~lly been installed 2 5 as a backup . Such an arrangement could be used on a floating production platform, but the cable wear problem is more pronounced because the productive life of the well is substantially longer than the typical d~ ing ti~De of the well. Therefore, it would be desirable to provide a riser tensioner system in which the cable replacement problem is eliminated.
The problem OI bending stresses induced by ro~l and pitch movements of the vessel have been minimized in -the past by designing special support vessels and platforms which do not react significantly to wlnd and wave action, and also by limiting the water depth in
.
~2~
wave action. Additionallv, the riser i8 subjected to considerable stress inc~uced by water currents which pass around the rlser bul;
which have no particular detrin~ental eEfect on the platforrn. In this si tuation, the ri~er fitring tends to be distorted as it is displaced laterally in one or more directions in response to the underwal:er currents . A further problem associated wit h supporting a production riser ~rom a vessel such as a floatin~ platform or the like is the bending stress induced in the riser by the roll and pitch of the vessel. ~he cornbination of the induced bending stress and the compressive forces which are exerted by the support vessel in respc3nse to wave action will cause rapid destruction of the riser unless the destructive effects are compensated or offset in some way.
Riser tensioner systems have been developed for offshore drilling and production activities to compensate for the rise and fall of a floating platform. Such tensioner systems have commonly comprised hydraulic compensating cylinders connected by cables to the riser at symmet~ically arran~ed tie points. In the course of their travel from cylinders to a Iiser, the cables pass over one or more sheaves and hence are subject to wear. It thus becomes necessary to periodically acljust the cables so that unworn portions of the cable ar~
shifted to the sheave locations and from time to time the cables must be replaced, typically at thirty day illtervals. To make this cable replacement and cylinder repair possible, a duplicate ~iser tensioner system with independellt riser connections has norm~lly been installed 2 5 as a backup . Such an arrangement could be used on a floating production platform, but the cable wear problem is more pronounced because the productive life of the well is substantially longer than the typical d~ ing ti~De of the well. Therefore, it would be desirable to provide a riser tensioner system in which the cable replacement problem is eliminated.
The problem OI bending stresses induced by ro~l and pitch movements of the vessel have been minimized in -the past by designing special support vessels and platforms which do not react significantly to wlnd and wave action, and also by limiting the water depth in
3 5 which these vessels operate . Other approaches have attempted to de~cc)uple detrimental ship motions b~ providing a reliable riser connection which will tend to minimize the rigidity of the riser ~57~
structural attachment to the surface vesseL. qlhe pitch and roll of tlle v~ssel, when added to the angle associated with maximum horizontal excursion of the production riser due to the ocean currents, result in excessively high bending stresses in the riser at the point of attachment unless these forces are decoupled in some way.
The most common solution to the elimination of excessively high bending stresses in ~he riser at the point of attachment is the provision of a riser pin connection with the surface vessel. Other arrangements have utilized a two axis gimbal connection. The use of pin and gi~bal connection arrangements has been limited generally to relatively short lengths of production risers operating in relatively calm waters. However, as the search for petroleum resources advances into deeper waters requiring increased length of production risers and where more severe wave action induces higher roll, pitch and heave reactions in the support vessel, it becomes imperative to provide improved connection means for minimizing the bending action induced in the production riser string, while also minimizing the axial stresses induced into the riser string by the upward and downward heave motions of the support vessel.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a marine riser tensioner system in which cables and sheaves are not utilized.
It is a further object of the present invention to provide a load supporting resilient bearing apparatus for minimizing the bending stresses induced into a pipe string by the pitching and rolling movements o~ a floating vessel from which the pipe string is supported.
In accordance with one aspect of the invention there is provided motion compensating apparatus for maintaining a tension load on a pipe string supported from a floating vessel subject to movement by wave action and the like, said apparatus comprising displaceable means engageable between said vessel and said pipe string and operable for varying khe distance between said vessel and said pipe string, said displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure ~hamber intermedia~e the housing and piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended;
means coupled to the actuator for supplying pressure fluid to the pressure chamber to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string; the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a fluid circuit including a reservoir, and indicator means in the circuit for : detecting excessive fluid leakage flow through the primary : seal means; and a bearing member disposed intermediate the vessel and the displaceable means, ~he bearing member having a resilient portion for reacting radial loads : coupled in supporting engagement with the displaceable means for permit~ing angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action~
In accordance with another aspect of the invention there is provided motion compensating apparatus for maintaining a tension load on a pipe string supported from a Floatin7 vessel subject to movement by wave action and the like, ~he apparatus comprising displaceable means engageable between the vessel and the pipe string and operable for varying the distance between the vessel and ~' 57~
the pipe string, the displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and deflning an annular fluid pressure chamber intermediate S the housing and the piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended; a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its vol~e to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative ~o the pipe string; the accumulator assembly being connected to the pressure chamber by conduit means including 10w rate limiting valve means operable to shut off fluid flow out of the pressure chamber and the acc~mulator assembly in response to a loss of fluid from the conduit means; and a bearing member disposed intermediate the vessel and the displaceable means, the bearing member having a resilient portion for reacting radial loads coupled in supporting engagement with the displaceable means for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
In accordance with another aspect of the invention there is provided motion compensating apparatus for maintaining a tension load on a pipe string supported from a floating vessel subject to movement by wave action and the like, said apparatus comprising a linear hydraulic actuator interconnecting the vessel and the pipe string and having a hollow housing and a hollow piston concen-trically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and the piston; conduit means coupled to the actuator for supplying pressure fluid to the pressure chamber to S7~
-5a-maintain a positive li~ting force on the pipe string as the vessel is displaced vertically relative to the pipe string; the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a 1uid circuit including indicator means in the circuit for detecting excessive fluid leakage flow through the primary seal means; and a bearing member disposed intermediate the vessel and the actuator for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
The foregoing as well as other objects, advantages and features of the invention will hereinafter become apparent to those skilled in the art~ and for purposes of illustration, but not of limitation, an exemplary embodiment of the invention is shown in the various views of the appended drawings, BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an elevation view of motion compensating apparatus embodying the present invention in association with a floating production platform;
Figure 2 is an enlarged front elevation view, with parts shown in longitudinal section, of the motion compensating apparatus of Figure l;
Figure 3 is a sectional view of a portion of the resilient bearing member of the motion compensating apparatus taken along the line 3-3 of Figure l; and Figure 4 is a graphical illustration of the relationship between the force exerted by the motion compensating apparatus with respect to the heave of the platform relative to a mean position.
~, 3~o2~t7g~
I)ESC~II'TION OF TIl~ PR~'EI~I~E13 E~BODIM~NT
ln ehe descript;on which follows, like parts are marl;ed throughout the specificution and drawin~ with the S~lMe reference numernls, ~espcetively.
Referring now to Fi~ure 1, the motion compensating apparatus of the present invention is indicated generally at 10 aIld is mounted on the deck 12 of a surfnce facility such as a floating oil well production platform indicated generally at 14. The surf~ce facility 14 has an oE)ening 16, extending through the deck 12, to pro~ride access to a production riser 18 extending thereto Erom the ocean floor 20. It will be apparent to those skilled in the art that the surface facility 14 is not limited to a floating platform but may be any such floating structure such as a drill ship, a tanker, or a barge. However, Ior purposes of illustration of the invention, the motion compensating apparatus will be described in connection with a floating platform. It should also be appreciated that the motion compensating apparatus 10 has utility ~or use in connection with d~lling, servicing or production operations in which a marine riser is employed .
The deck 12 is supported above the surface 22 of the ocean by means of a plurality of downwardly e~ctending controllably buoyant members or legs 24 ~vhich maintain the deck 12 at a desired elevation above the ocean surface 22. The buoyant members 24 have sufficiellt tank capacity that the deck 12 can be raised or lowered as desired by 2 5 use of a suitable control system for transporting the structure at minimum draft while in transit or for positioning it at a working draft over a production site. While not shown in detELil, the respective buoyant members 24 are further provided with an interconnecting truss structure 2S and other nccessary understructure for stabilizing the pl~tform. To further stabilize the floating platform 1~, a plurality of mooring lines and anchors (llOt shown~ may be provided for holding the platform over a production site 28. An example of such an urrangement is illustrated in U.S. Patent 3~983,706.
Basic wellheucl equlpment 30 is shown imbedded in the ocean floor 20 bencl~th the plutform 14. The production Iiser 18 extcnds irom the wellhead e~uiI)ment 30 to n conventional murine riser connector 32 which is provided with flex joints and integral choke and kill lines 34, 36. The usual Christlrlas tree arrangement and control member, àlthough not shown, may al80 be included in the wellhead equipnlent 30 to control the prvduction operation insofnr as production fluid flow is concerned. The lower end of the riser 18 is preferably pivotally comlected at the wellhead 30 to ~llow for a limited amount of' relative movement as the plat~orm 14 is subjes~ted to some lateral displacement frvm it,s desired location above the production site 28.
The production riser 18 typically compri~ses a number of elongated tubular members conneclted end to end and having sufficient diameter to enclose drill tubing and to conduct drilling mud. A
typical cross-sectional dimension of the riser is sixteen inches O . D .
with one-half inch w~ll thickness. For production operations it is used for conveying crude oil or gas from the wellhead equipment 30 to the platform 14 where it is discharged into a reservoir car~iecl by the platform or into a tanker (not shown) lying alongside.
As discussed above, prior art marine riser structures are subject to buckling forces induced by the heaving action of the floating platform 14 and are also subject to hending momellts induced by the roll and pitch movements of the platform. The harmful effects of the bending moment and buckling forces are intensified when the platform 14 is laterally displaced excessively, and subjected to extreme vertical movement due to severe weather conditions on the water surface, for example. These problems are overcome in the 2 5 present invention by the provision of the motion compensating apparatus 10 which includes a resilient bearing member 38 which reacts both radial and axial loads and decouples the roll and pitch movements of the floating vessel with respect to the production riser 18, and by the provision of a linear hydraulic actuator assembly 40 which is connected to a pneumo-hydraulic accllmulator for maintaining hydraulic working fluid under pressure in the actuator assembly as the platform heaves and falls in response to wave movements of the sea. According to this arrangement, the production riser 18 is supported by a column of pressurized hydraulic fluid whose volume varies in proportion to the displacement ot` the Eloating plntform 1 relative to the end of the production riser t8.
The construction detuils of the motion compensating apparatus 10 are illustrated in E~i~;~re 2 of the drawing. The linear hydraulic acLuator aseembly 40 includes a c:ylinder member comprising a housing 44 having a first open end portion 46 suitably connected to an annular collar 48. The collar 48 includes a cylindrical mounting flange portion which is bolted to a moUnting weldment or ~ng 50 oL
the resilient bearing melllber 38. The actuator assembly 40 includes a cylindrical annular piston member 52 which is concentric ally disposed for extension and retraction witllin the housing 44. The piston member 52 has a tubular piston rod portion 63 OI relatively smaller diameter than the bore 54 of housing 44, thereby defining an annular pressure chamber 55 which changes in volume aB the piston is displaced along the longitudinal a~is of the hou~ing~. The piston 52 includes a head 58 formed as a separate part which is threadedly connected to the upper end of the rod 53. The piston head 58 includes primary seals or packings 56 and secondary packings 60 which are disposeci in annular grooves ~ormed in the head for sliding eTlgagement with the cylinder bore 54. A circumferential fluid 1eakage flow groove 57 is forrrlecl in the head 58 between the pacldngs 56 and 60 and is in communication with an elongated passages 61 formed in the rod portion 53. The passage 61 muy be ~ormed as a groove in the rod portion 53 which is closed by a sleeve 63 disposed over the outer diameter of the rod portion as shown. The passage 61 is in communication with a flexible leakage flow return line 65 by way of a suitable ~itting, as shown.
The piston rod portiorl 53 extends through an end cap 6~
threadedly secured to the lower encl 64 of the housing 44 and is in fluid sealing engagement with primary seals or packings 67 and secondary packings 66. An annular groove 69 is formed iII the inner bore wall of the cap 62 for conducting primary packing leakage ~luid to a flexible return line 84. The cylinder end cap 62 is threadedly connected to the lower end 64 of the housing 44 in sealing engagement therewith.
The piston 52 is displaceable along the longitudinal axis of 3 5 the housing 44 and is slidable with respect to an elongated tubular sleeve 68 which is concentrically disposed within the piston and suitably secured to the anmAlar collar 48. Also secured to the collar 48 is a connector portion 70 for engaging a corresponding cormector of a conventional diverter assembly (not shown). Connection to the opposite end o~ the motion compensating apparatus is pro~rided b~ a connector portion 72 threadedly secured to the lower end of the piston rod 53. The connector 72 i5 adapted to be connected to the marine riser connector 32. The piston 52 and sleeve 68 cooperate to form an elongated ccntral passage 41 extending through the apparatus 10 from the connector 70 to the connector 72.
The linear hydraulic actuator assembly 40 is supported f~om the deck 12 of the floating platform 14 by the resilient bearing member 38 which is disposed in load supporting~ relation intermediate ~he deck 12 and the annular collar assembly 48. The bearing member 38 is an annular section of a substantially spherical laminated body of superposed layers of an elastic material 74 and of a relatively inelastic material 76 as can best be seen in Figure 3 of the drawing. The laminated body is interposed between the mounting ring 50 and a supporting base member 51 disposed on the deck 12. A central, somewhat conical shaped passage 75 is formed a2~ially through the bearing member 3û for receivin~ the collar 48 whereby the actuator 40 extends downwardly through the bearing member and the deck la.
The purpose of the resilient bearing member 38 is to permit angular displacement of the floating platform 14 with respect to the hydraulic actuator assembly 40 and the ~iser 18 and, in particular, to decouple the bending moment forces which would ~therwise be 2 5 imparted to the riser 18 as the platform 14 rolls and pitches in response to wave movements of the sea. The elastic layer 74 is preferably ~ormed of an elastomer material such as Pubber and the relatively inelastic la~er 76 is preferably forrned of a metal such as steel which in combinativn are capable of supporting a working compressive load in excess OI the production riser weight. The resilient bearing member 38 can react axial as well as radial loads, thereby cooperating with the linear actuator assembly 40 to relieve stresses incluced by heaving and lateral displacement of the platform 14. In a preferred embodiment, the resilient bearing member 38 is clesigned to support fln axially applied loacl of 350 ,000 pounds and is able to withstand a full plus or minus seven degree rotation about a radial axis ~or a minimum of 1~ 5 milllon cycles. The spring constnnt 79~
of the resilient bearing member 38 can be vaI~ied somewhat by increasing or decreasiIIg the amount of resilient material in the layer q4 .
Accord~ing to a preferred embodiment of the linear hyciraulic actuator assembly 40, it is designed to exert a force Oe 350,OûO
pounds at a hydraulic fluid pressure of 2, 200 psi. The maximum recommended operating pressure is 2 ,650 psi. The cylindYical housing member 44 and piston 52 are preferably constructed Erom a low carbon steel which is suitable for low temperature service. The piston 52 preferably has a maximum stroke ~f 18 feet and is adapted to be driven at a rate of 0.6 feet per second. The force, stroke and displacement rate may, of course, vary according to the requirements OI a particular applica$ion.
The aImular fluid pressure chamber 55 is supplied with hydraulic fluid by a pump 92 and an accumulator assem~ly 42 through a llexible supply line or hose 80. High pressure working fluid is preferably con~reyed through multiple runs cf hydraulic hoses 80 to provide redundancy, although only one hose is shown in the drawing figures. The hoses 80 are preferably provided with back to back flow rate limiting or velocity fuse type check valves 78 and 79 as shown schematically in Figure 2. The valves 78 and 7'~ are operable to close in response to a break in the line 80 to prevent fluid from escaping from the chamber 55 or from being totally discharged from the supply circuit including the pump 92 and accumul~tor assembly 42. A manually operable valve 81 is connected across check valve 78 f~r repressurizing a repaired or replaced hose so that the valve 78 may be reopened without depressurizing the fluid supply circuit.
~igh pressure hydraulic fluid is conducted through the line 80 into an inlet passage 82 in end cap 62 which leads to the annular fluid pressure chamber 55 by way of an annular chamber 83 and fluid passages 85.
According to operution of the hydraulic actuator assembly 40, t~e accumulator assembly 42 is suitably charged to place the rlser 18 under a predetermined level of tension. The pneumo-hydraulic 3 5 accumulator assembly 42 includes a plurality of hydraulic presstlre tanks 88 which are adapted to receive a variable volume of hydraulic working fluid and to be charged with air or an inert gas from a 57~3~
suitable source SllCh as an a:ir pump 90. The air or gas pressure is reg~llated to a substantially constant valve and may al90 be provided hy a series of compressed air or gas b~ttles (not shown).
In opera~ion, the linear hydraulic actuator assembly 4U is charged with hydraulic :fluid to place a predetermined level of tension, for example 350 kips, on the riser 18. As the floating plntform falls in elevation with respect to the production riser 18 in response to wave movement or tidal action, the housing 44 is displflced downwardly with respect to the piston 52. The volume of the pressure chamber 55 increases proport:ionately and the pressure o:f the working fluid contuined therein tends to diminish but the check valves 78 and 79, which are suitably biased to be normall~ open~
admit high pressure hydraulic working fluid from the accumulator assembly 42 into the inlet passage 82 by way of line 80. By this operation, the pressure chamber 55 is maintained filled with high pressure hydraulic working fluid at a substantially constant pressure whereby the piston 52 and production riser 18 are supported by a column of hydraulic f1uid which increases and decreases in its lon~itudinal extent ~:tS the housing member 44 is displaced by the 2 0 heaving action of the floating platform . When the platPor!n is being displaced in an upward direction relative to the riser striIlg, the working fluid contained within the pressure chamber 55 is discharged back through the line 80 by way of the normally open valves 78 and 79 into the accumulator tanks 88.
2 5 The hydraulic ~luid supply circuit further includes a reservoir 86 connected to the inlet port of the pump 9~ ~r supplying makeup fluid through a check valve 94 to the systen~ including the accumulator tanks 88. The reser-~oir 86 includes a Qoat switch assembly 96 connected to a source o:~ pressure air for operating the 3 0 pump ~2 when a float 99 senses a predetermined level in the reqervoir.
The leakage ~ow return lines 85 ancl 84 are connected to the reservoir by WQy of the inlet line or pump 92, as shown. The leakage flow return lines 65 and 84 are also connected to respective pressure switches 95 and 97 which, in turn, are opernble to energi~e respective indicators 103 and 101 if the fluid flow through the lines 65 andlor 84 should exceed a predetermined rate. Accordin~ly, ~2~
imminent fl~iluIe of the primary packings 56 and 67 may be detected and corrective action taken before the actuator assembly 40 sufers a total loss oi fluid frolrl the charnber 55.
Dynamic opera~ion of the hydraulic actuator assembly 40 i6 illuætrated in Figure 4 of the drawing, where the force variation exerted by the actuator is shown graphically as a function of the ship position with respect to an arbitrury reference level which corresponds to a predetermined tension level. The force variation exerted by the actuator 40 for a 92 cubic foot accumulator is shown by the graph 100 and the corresponding force variation for a 183 cubic feet accumulal;or is shown by the graph 102. These graphs indicate that as the capacity of the accumulator system increases, proportionately less cylinder force variation is experienced for a given chan~e in platform position.
The present invention provides a versatile alld robust motion cornpensating apparatus for maintaining a substantially constant tension load on a production riser while substantially reducing the bending stresses induced in the riser hy the roll and pitch of the plateorm to which it is attached. Theæe advantages are mnd~s possible by the resilient bea~ing arrangement in combination with the linear hydraulic actuator assembly. This moffon compsnsating arrangement therefore permits various activities to be carried out at greater ocean depths and in heavier seas than has been possible with conventional motion compensating arrangements.
The particular details of construction disclosed herein are, of course, only illustrative and other equivalent structures may be utilized without departing from the scope of the invention as defined by the appended claims.
What is claimed is:
structural attachment to the surface vesseL. qlhe pitch and roll of tlle v~ssel, when added to the angle associated with maximum horizontal excursion of the production riser due to the ocean currents, result in excessively high bending stresses in the riser at the point of attachment unless these forces are decoupled in some way.
The most common solution to the elimination of excessively high bending stresses in ~he riser at the point of attachment is the provision of a riser pin connection with the surface vessel. Other arrangements have utilized a two axis gimbal connection. The use of pin and gi~bal connection arrangements has been limited generally to relatively short lengths of production risers operating in relatively calm waters. However, as the search for petroleum resources advances into deeper waters requiring increased length of production risers and where more severe wave action induces higher roll, pitch and heave reactions in the support vessel, it becomes imperative to provide improved connection means for minimizing the bending action induced in the production riser string, while also minimizing the axial stresses induced into the riser string by the upward and downward heave motions of the support vessel.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a marine riser tensioner system in which cables and sheaves are not utilized.
It is a further object of the present invention to provide a load supporting resilient bearing apparatus for minimizing the bending stresses induced into a pipe string by the pitching and rolling movements o~ a floating vessel from which the pipe string is supported.
In accordance with one aspect of the invention there is provided motion compensating apparatus for maintaining a tension load on a pipe string supported from a floating vessel subject to movement by wave action and the like, said apparatus comprising displaceable means engageable between said vessel and said pipe string and operable for varying khe distance between said vessel and said pipe string, said displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure ~hamber intermedia~e the housing and piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended;
means coupled to the actuator for supplying pressure fluid to the pressure chamber to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string; the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a fluid circuit including a reservoir, and indicator means in the circuit for : detecting excessive fluid leakage flow through the primary : seal means; and a bearing member disposed intermediate the vessel and the displaceable means, ~he bearing member having a resilient portion for reacting radial loads : coupled in supporting engagement with the displaceable means for permit~ing angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action~
In accordance with another aspect of the invention there is provided motion compensating apparatus for maintaining a tension load on a pipe string supported from a Floatin7 vessel subject to movement by wave action and the like, ~he apparatus comprising displaceable means engageable between the vessel and the pipe string and operable for varying the distance between the vessel and ~' 57~
the pipe string, the displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and deflning an annular fluid pressure chamber intermediate S the housing and the piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended; a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its vol~e to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative ~o the pipe string; the accumulator assembly being connected to the pressure chamber by conduit means including 10w rate limiting valve means operable to shut off fluid flow out of the pressure chamber and the acc~mulator assembly in response to a loss of fluid from the conduit means; and a bearing member disposed intermediate the vessel and the displaceable means, the bearing member having a resilient portion for reacting radial loads coupled in supporting engagement with the displaceable means for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
In accordance with another aspect of the invention there is provided motion compensating apparatus for maintaining a tension load on a pipe string supported from a floating vessel subject to movement by wave action and the like, said apparatus comprising a linear hydraulic actuator interconnecting the vessel and the pipe string and having a hollow housing and a hollow piston concen-trically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and the piston; conduit means coupled to the actuator for supplying pressure fluid to the pressure chamber to S7~
-5a-maintain a positive li~ting force on the pipe string as the vessel is displaced vertically relative to the pipe string; the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a 1uid circuit including indicator means in the circuit for detecting excessive fluid leakage flow through the primary seal means; and a bearing member disposed intermediate the vessel and the actuator for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
The foregoing as well as other objects, advantages and features of the invention will hereinafter become apparent to those skilled in the art~ and for purposes of illustration, but not of limitation, an exemplary embodiment of the invention is shown in the various views of the appended drawings, BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an elevation view of motion compensating apparatus embodying the present invention in association with a floating production platform;
Figure 2 is an enlarged front elevation view, with parts shown in longitudinal section, of the motion compensating apparatus of Figure l;
Figure 3 is a sectional view of a portion of the resilient bearing member of the motion compensating apparatus taken along the line 3-3 of Figure l; and Figure 4 is a graphical illustration of the relationship between the force exerted by the motion compensating apparatus with respect to the heave of the platform relative to a mean position.
~, 3~o2~t7g~
I)ESC~II'TION OF TIl~ PR~'EI~I~E13 E~BODIM~NT
ln ehe descript;on which follows, like parts are marl;ed throughout the specificution and drawin~ with the S~lMe reference numernls, ~espcetively.
Referring now to Fi~ure 1, the motion compensating apparatus of the present invention is indicated generally at 10 aIld is mounted on the deck 12 of a surfnce facility such as a floating oil well production platform indicated generally at 14. The surf~ce facility 14 has an oE)ening 16, extending through the deck 12, to pro~ride access to a production riser 18 extending thereto Erom the ocean floor 20. It will be apparent to those skilled in the art that the surface facility 14 is not limited to a floating platform but may be any such floating structure such as a drill ship, a tanker, or a barge. However, Ior purposes of illustration of the invention, the motion compensating apparatus will be described in connection with a floating platform. It should also be appreciated that the motion compensating apparatus 10 has utility ~or use in connection with d~lling, servicing or production operations in which a marine riser is employed .
The deck 12 is supported above the surface 22 of the ocean by means of a plurality of downwardly e~ctending controllably buoyant members or legs 24 ~vhich maintain the deck 12 at a desired elevation above the ocean surface 22. The buoyant members 24 have sufficiellt tank capacity that the deck 12 can be raised or lowered as desired by 2 5 use of a suitable control system for transporting the structure at minimum draft while in transit or for positioning it at a working draft over a production site. While not shown in detELil, the respective buoyant members 24 are further provided with an interconnecting truss structure 2S and other nccessary understructure for stabilizing the pl~tform. To further stabilize the floating platform 1~, a plurality of mooring lines and anchors (llOt shown~ may be provided for holding the platform over a production site 28. An example of such an urrangement is illustrated in U.S. Patent 3~983,706.
Basic wellheucl equlpment 30 is shown imbedded in the ocean floor 20 bencl~th the plutform 14. The production Iiser 18 extcnds irom the wellhead e~uiI)ment 30 to n conventional murine riser connector 32 which is provided with flex joints and integral choke and kill lines 34, 36. The usual Christlrlas tree arrangement and control member, àlthough not shown, may al80 be included in the wellhead equipnlent 30 to control the prvduction operation insofnr as production fluid flow is concerned. The lower end of the riser 18 is preferably pivotally comlected at the wellhead 30 to ~llow for a limited amount of' relative movement as the plat~orm 14 is subjes~ted to some lateral displacement frvm it,s desired location above the production site 28.
The production riser 18 typically compri~ses a number of elongated tubular members conneclted end to end and having sufficient diameter to enclose drill tubing and to conduct drilling mud. A
typical cross-sectional dimension of the riser is sixteen inches O . D .
with one-half inch w~ll thickness. For production operations it is used for conveying crude oil or gas from the wellhead equipment 30 to the platform 14 where it is discharged into a reservoir car~iecl by the platform or into a tanker (not shown) lying alongside.
As discussed above, prior art marine riser structures are subject to buckling forces induced by the heaving action of the floating platform 14 and are also subject to hending momellts induced by the roll and pitch movements of the platform. The harmful effects of the bending moment and buckling forces are intensified when the platform 14 is laterally displaced excessively, and subjected to extreme vertical movement due to severe weather conditions on the water surface, for example. These problems are overcome in the 2 5 present invention by the provision of the motion compensating apparatus 10 which includes a resilient bearing member 38 which reacts both radial and axial loads and decouples the roll and pitch movements of the floating vessel with respect to the production riser 18, and by the provision of a linear hydraulic actuator assembly 40 which is connected to a pneumo-hydraulic accllmulator for maintaining hydraulic working fluid under pressure in the actuator assembly as the platform heaves and falls in response to wave movements of the sea. According to this arrangement, the production riser 18 is supported by a column of pressurized hydraulic fluid whose volume varies in proportion to the displacement ot` the Eloating plntform 1 relative to the end of the production riser t8.
The construction detuils of the motion compensating apparatus 10 are illustrated in E~i~;~re 2 of the drawing. The linear hydraulic acLuator aseembly 40 includes a c:ylinder member comprising a housing 44 having a first open end portion 46 suitably connected to an annular collar 48. The collar 48 includes a cylindrical mounting flange portion which is bolted to a moUnting weldment or ~ng 50 oL
the resilient bearing melllber 38. The actuator assembly 40 includes a cylindrical annular piston member 52 which is concentric ally disposed for extension and retraction witllin the housing 44. The piston member 52 has a tubular piston rod portion 63 OI relatively smaller diameter than the bore 54 of housing 44, thereby defining an annular pressure chamber 55 which changes in volume aB the piston is displaced along the longitudinal a~is of the hou~ing~. The piston 52 includes a head 58 formed as a separate part which is threadedly connected to the upper end of the rod 53. The piston head 58 includes primary seals or packings 56 and secondary packings 60 which are disposeci in annular grooves ~ormed in the head for sliding eTlgagement with the cylinder bore 54. A circumferential fluid 1eakage flow groove 57 is forrrlecl in the head 58 between the pacldngs 56 and 60 and is in communication with an elongated passages 61 formed in the rod portion 53. The passage 61 muy be ~ormed as a groove in the rod portion 53 which is closed by a sleeve 63 disposed over the outer diameter of the rod portion as shown. The passage 61 is in communication with a flexible leakage flow return line 65 by way of a suitable ~itting, as shown.
The piston rod portiorl 53 extends through an end cap 6~
threadedly secured to the lower encl 64 of the housing 44 and is in fluid sealing engagement with primary seals or packings 67 and secondary packings 66. An annular groove 69 is formed iII the inner bore wall of the cap 62 for conducting primary packing leakage ~luid to a flexible return line 84. The cylinder end cap 62 is threadedly connected to the lower end 64 of the housing 44 in sealing engagement therewith.
The piston 52 is displaceable along the longitudinal axis of 3 5 the housing 44 and is slidable with respect to an elongated tubular sleeve 68 which is concentrically disposed within the piston and suitably secured to the anmAlar collar 48. Also secured to the collar 48 is a connector portion 70 for engaging a corresponding cormector of a conventional diverter assembly (not shown). Connection to the opposite end o~ the motion compensating apparatus is pro~rided b~ a connector portion 72 threadedly secured to the lower end of the piston rod 53. The connector 72 i5 adapted to be connected to the marine riser connector 32. The piston 52 and sleeve 68 cooperate to form an elongated ccntral passage 41 extending through the apparatus 10 from the connector 70 to the connector 72.
The linear hydraulic actuator assembly 40 is supported f~om the deck 12 of the floating platform 14 by the resilient bearing member 38 which is disposed in load supporting~ relation intermediate ~he deck 12 and the annular collar assembly 48. The bearing member 38 is an annular section of a substantially spherical laminated body of superposed layers of an elastic material 74 and of a relatively inelastic material 76 as can best be seen in Figure 3 of the drawing. The laminated body is interposed between the mounting ring 50 and a supporting base member 51 disposed on the deck 12. A central, somewhat conical shaped passage 75 is formed a2~ially through the bearing member 3û for receivin~ the collar 48 whereby the actuator 40 extends downwardly through the bearing member and the deck la.
The purpose of the resilient bearing member 38 is to permit angular displacement of the floating platform 14 with respect to the hydraulic actuator assembly 40 and the ~iser 18 and, in particular, to decouple the bending moment forces which would ~therwise be 2 5 imparted to the riser 18 as the platform 14 rolls and pitches in response to wave movements of the sea. The elastic layer 74 is preferably ~ormed of an elastomer material such as Pubber and the relatively inelastic la~er 76 is preferably forrned of a metal such as steel which in combinativn are capable of supporting a working compressive load in excess OI the production riser weight. The resilient bearing member 38 can react axial as well as radial loads, thereby cooperating with the linear actuator assembly 40 to relieve stresses incluced by heaving and lateral displacement of the platform 14. In a preferred embodiment, the resilient bearing member 38 is clesigned to support fln axially applied loacl of 350 ,000 pounds and is able to withstand a full plus or minus seven degree rotation about a radial axis ~or a minimum of 1~ 5 milllon cycles. The spring constnnt 79~
of the resilient bearing member 38 can be vaI~ied somewhat by increasing or decreasiIIg the amount of resilient material in the layer q4 .
Accord~ing to a preferred embodiment of the linear hyciraulic actuator assembly 40, it is designed to exert a force Oe 350,OûO
pounds at a hydraulic fluid pressure of 2, 200 psi. The maximum recommended operating pressure is 2 ,650 psi. The cylindYical housing member 44 and piston 52 are preferably constructed Erom a low carbon steel which is suitable for low temperature service. The piston 52 preferably has a maximum stroke ~f 18 feet and is adapted to be driven at a rate of 0.6 feet per second. The force, stroke and displacement rate may, of course, vary according to the requirements OI a particular applica$ion.
The aImular fluid pressure chamber 55 is supplied with hydraulic fluid by a pump 92 and an accumulator assem~ly 42 through a llexible supply line or hose 80. High pressure working fluid is preferably con~reyed through multiple runs cf hydraulic hoses 80 to provide redundancy, although only one hose is shown in the drawing figures. The hoses 80 are preferably provided with back to back flow rate limiting or velocity fuse type check valves 78 and 79 as shown schematically in Figure 2. The valves 78 and 7'~ are operable to close in response to a break in the line 80 to prevent fluid from escaping from the chamber 55 or from being totally discharged from the supply circuit including the pump 92 and accumul~tor assembly 42. A manually operable valve 81 is connected across check valve 78 f~r repressurizing a repaired or replaced hose so that the valve 78 may be reopened without depressurizing the fluid supply circuit.
~igh pressure hydraulic fluid is conducted through the line 80 into an inlet passage 82 in end cap 62 which leads to the annular fluid pressure chamber 55 by way of an annular chamber 83 and fluid passages 85.
According to operution of the hydraulic actuator assembly 40, t~e accumulator assembly 42 is suitably charged to place the rlser 18 under a predetermined level of tension. The pneumo-hydraulic 3 5 accumulator assembly 42 includes a plurality of hydraulic presstlre tanks 88 which are adapted to receive a variable volume of hydraulic working fluid and to be charged with air or an inert gas from a 57~3~
suitable source SllCh as an a:ir pump 90. The air or gas pressure is reg~llated to a substantially constant valve and may al90 be provided hy a series of compressed air or gas b~ttles (not shown).
In opera~ion, the linear hydraulic actuator assembly 4U is charged with hydraulic :fluid to place a predetermined level of tension, for example 350 kips, on the riser 18. As the floating plntform falls in elevation with respect to the production riser 18 in response to wave movement or tidal action, the housing 44 is displflced downwardly with respect to the piston 52. The volume of the pressure chamber 55 increases proport:ionately and the pressure o:f the working fluid contuined therein tends to diminish but the check valves 78 and 79, which are suitably biased to be normall~ open~
admit high pressure hydraulic working fluid from the accumulator assembly 42 into the inlet passage 82 by way of line 80. By this operation, the pressure chamber 55 is maintained filled with high pressure hydraulic working fluid at a substantially constant pressure whereby the piston 52 and production riser 18 are supported by a column of hydraulic f1uid which increases and decreases in its lon~itudinal extent ~:tS the housing member 44 is displaced by the 2 0 heaving action of the floating platform . When the platPor!n is being displaced in an upward direction relative to the riser striIlg, the working fluid contained within the pressure chamber 55 is discharged back through the line 80 by way of the normally open valves 78 and 79 into the accumulator tanks 88.
2 5 The hydraulic ~luid supply circuit further includes a reservoir 86 connected to the inlet port of the pump 9~ ~r supplying makeup fluid through a check valve 94 to the systen~ including the accumulator tanks 88. The reser-~oir 86 includes a Qoat switch assembly 96 connected to a source o:~ pressure air for operating the 3 0 pump ~2 when a float 99 senses a predetermined level in the reqervoir.
The leakage ~ow return lines 85 ancl 84 are connected to the reservoir by WQy of the inlet line or pump 92, as shown. The leakage flow return lines 65 and 84 are also connected to respective pressure switches 95 and 97 which, in turn, are opernble to energi~e respective indicators 103 and 101 if the fluid flow through the lines 65 andlor 84 should exceed a predetermined rate. Accordin~ly, ~2~
imminent fl~iluIe of the primary packings 56 and 67 may be detected and corrective action taken before the actuator assembly 40 sufers a total loss oi fluid frolrl the charnber 55.
Dynamic opera~ion of the hydraulic actuator assembly 40 i6 illuætrated in Figure 4 of the drawing, where the force variation exerted by the actuator is shown graphically as a function of the ship position with respect to an arbitrury reference level which corresponds to a predetermined tension level. The force variation exerted by the actuator 40 for a 92 cubic foot accumulator is shown by the graph 100 and the corresponding force variation for a 183 cubic feet accumulal;or is shown by the graph 102. These graphs indicate that as the capacity of the accumulator system increases, proportionately less cylinder force variation is experienced for a given chan~e in platform position.
The present invention provides a versatile alld robust motion cornpensating apparatus for maintaining a substantially constant tension load on a production riser while substantially reducing the bending stresses induced in the riser hy the roll and pitch of the plateorm to which it is attached. Theæe advantages are mnd~s possible by the resilient bea~ing arrangement in combination with the linear hydraulic actuator assembly. This moffon compsnsating arrangement therefore permits various activities to be carried out at greater ocean depths and in heavier seas than has been possible with conventional motion compensating arrangements.
The particular details of construction disclosed herein are, of course, only illustrative and other equivalent structures may be utilized without departing from the scope of the invention as defined by the appended claims.
What is claimed is:
Claims (10)
1. Motion compensating apparatus for maintaining a tension load on a pipe string supported from a floating vessel subject to movement by wave action and the like, said apparatus comprising:
displaceable means engageable between said vessel and said pipe string and operable for varying the distance between said vessel and said pipe string, said displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended;
means coupled to the actuator for supplying pressure fluid to the pressure chamber to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a fluid circuit including a reservoir, and indicator means in the circuit for detecting excessive fluid leakage flow through the primary seal means; and a bearing member disposed intermediate the vessel and the displaceable means, the bearing member having a resilient portion for reacting radial loads coupled in supporting engagement with the displaceable means for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
displaceable means engageable between said vessel and said pipe string and operable for varying the distance between said vessel and said pipe string, said displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended;
means coupled to the actuator for supplying pressure fluid to the pressure chamber to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a fluid circuit including a reservoir, and indicator means in the circuit for detecting excessive fluid leakage flow through the primary seal means; and a bearing member disposed intermediate the vessel and the displaceable means, the bearing member having a resilient portion for reacting radial loads coupled in supporting engagement with the displaceable means for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
2. Motion compensating apparatus for maintaining a tension load on a pipe string supported from a floating vessel subject to movement by wave action and the like, the apparatus comprising:
displaceable means engageable between the vessel and the pipe string and operable for varying the distance between the vessel and the pipe string, the displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and the piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended;
a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its volume to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the accumulator assembly being connected to the pressure chamber by conduit means including flow rate limiting valve means operable to shut off fluid flow out of the pressure chamber and the accumulator assembly in response to a loss of fluid from the conduit means; and a bearing member disposed intermediate the vessel and the displaceable means, the bearing member having a resilient portion for reacting radial loads coupled in supporting engagement with the displaceable means for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
displaceable means engageable between the vessel and the pipe string and operable for varying the distance between the vessel and the pipe string, the displaceable means comprising a linear hydraulic actuator having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and the piston, the space enclosed within the interior of the piston defining a central passageway through which well production equipment may be extended;
a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its volume to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the accumulator assembly being connected to the pressure chamber by conduit means including flow rate limiting valve means operable to shut off fluid flow out of the pressure chamber and the accumulator assembly in response to a loss of fluid from the conduit means; and a bearing member disposed intermediate the vessel and the displaceable means, the bearing member having a resilient portion for reacting radial loads coupled in supporting engagement with the displaceable means for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
3. The motion compensating apparatus as defined in claim 1 wherein:
the bearing member comprises an annular section of a substantially spherical laminated body of superposed layers of an elastic material and of a relatively inelastic material, the annular section defining a central passageway through which the production equipment may be extended.
the bearing member comprises an annular section of a substantially spherical laminated body of superposed layers of an elastic material and of a relatively inelastic material, the annular section defining a central passageway through which the production equipment may be extended.
4. The motion compensating apparatus as defined in claim 1 wherein:
the means for supplying pressure fluid to the pressure chamber comprises a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its volume.
the means for supplying pressure fluid to the pressure chamber comprises a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its volume.
5. The motion compensating apparatus as defined in claim 4 wherein:
the hydraulic accumulator assembly includes fluid accumulator means for storing pressurized hydraulic working fluid and a source of compressed gas connected in fluid communication with said accumulator means for providing a predetermined fluid pressure of the hydraulic working fluid in the cylinder.
the hydraulic accumulator assembly includes fluid accumulator means for storing pressurized hydraulic working fluid and a source of compressed gas connected in fluid communication with said accumulator means for providing a predetermined fluid pressure of the hydraulic working fluid in the cylinder.
6. The motion compensating apparatus as defined in claim 2 wherein:
said piston is sealingly engaged with said housing to form the pressure chamber by respective sets of primary and secondary seal means, each of said sets of seal means including passage means interposed between said primary seal means and said secondary seal means for conducting fluid leakage flow from said actuator to a fluid circuit including a reservoir, and indicator means in said circuit for detecting excessive fluid leakage flow though said primary seal means.
said piston is sealingly engaged with said housing to form the pressure chamber by respective sets of primary and secondary seal means, each of said sets of seal means including passage means interposed between said primary seal means and said secondary seal means for conducting fluid leakage flow from said actuator to a fluid circuit including a reservoir, and indicator means in said circuit for detecting excessive fluid leakage flow though said primary seal means.
7. The motion compensating apparatus as defined in claim 5 wherein:
a hydraulic pump is provided for charging a portion of the fluid circuit, the pump being connected to a reservoir, and the reservoir includes a float switch connected to a source of power for energizing the pump to recharge the portion of the fluid circuit including the pressure chamber when the fluid in the reservoir reaches a predetermined level.
a hydraulic pump is provided for charging a portion of the fluid circuit, the pump being connected to a reservoir, and the reservoir includes a float switch connected to a source of power for energizing the pump to recharge the portion of the fluid circuit including the pressure chamber when the fluid in the reservoir reaches a predetermined level.
8. The motion compensating apparatus as defined in claim 4 wherein:
said accumulator assembly is connected to said pressure chamber by conduit means including flow rate limiting valve means operable to shut off fluid flow out of said pressure chamber and said accumulator assembly in response to a loss of fluid from said conduit means.
said accumulator assembly is connected to said pressure chamber by conduit means including flow rate limiting valve means operable to shut off fluid flow out of said pressure chamber and said accumulator assembly in response to a loss of fluid from said conduit means.
9. Motion compensating apparatus for maintaining a tension load on a pipe string supported from a floating vessel subject to movement by wave action and the like, said apparatus comprising:
a linear hydraulic actuator interconnecting the vessel and the pipe string and having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and the piston;
conduit means coupled to the actuator for supplying pressure fluid to the pressure chamber to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a fluid circuit including indicator means in the circuit for detecting excessive fluid leakage flow through the primary seal means; and a bearing member disposed intermediate the vessel and the actuator for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
a linear hydraulic actuator interconnecting the vessel and the pipe string and having a hollow housing and a hollow piston concentrically disposed within the housing and defining an annular fluid pressure chamber intermediate the housing and the piston;
conduit means coupled to the actuator for supplying pressure fluid to the pressure chamber to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the piston is sealingly engaged with the housing to form the pressure chamber by respective sets of primary and secondary seal means, each of the sets of seal means including passage means interposed between the primary seal means and the secondary seal means for conducting fluid leakage flow from the actuator to a fluid circuit including indicator means in the circuit for detecting excessive fluid leakage flow through the primary seal means; and a bearing member disposed intermediate the vessel and the actuator for permitting angular displacement of the vessel relative to the pipe string in response to roll and pitch movements imparted to the vessel by wave action.
10. The apparatus set forth in claim 9 including:
a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its volume to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the accumulator assembly being connected to the pressure chamber by the conduit means including flow rate limiting valve means operable to shut off fluid flow out of the pressure chamber and the accumulator assembly in response to a loss of fluid from the conduit means.
a hydraulic accumulator assembly connected in fluid communication with the pressure chamber for supplying hydraulic fluid to and for receiving hydraulic fluid from the pressure chamber in response to a change in its volume to maintain a positive lifting force on the pipe string as the vessel is displaced vertically relative to the pipe string;
the accumulator assembly being connected to the pressure chamber by the conduit means including flow rate limiting valve means operable to shut off fluid flow out of the pressure chamber and the accumulator assembly in response to a loss of fluid from the conduit means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US35492382A | 1982-03-05 | 1982-03-05 | |
| US354,923 | 1982-03-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1205740A true CA1205740A (en) | 1986-06-10 |
Family
ID=23395470
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000422813A Expired CA1205740A (en) | 1982-03-05 | 1983-03-03 | Marine riser tensioner |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0088608A3 (en) |
| JP (1) | JPS58173289A (en) |
| CA (1) | CA1205740A (en) |
| DK (1) | DK109383A (en) |
| FI (1) | FI830746L (en) |
| NO (1) | NO830764L (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4712620A (en) * | 1985-01-31 | 1987-12-15 | Vetco Gray Inc. | Upper marine riser package |
| SG144822A1 (en) | 2007-01-08 | 2008-08-28 | Vetco Gray Inc | Ram style tensioner with fixed conductor and floating frame |
| NO329804B1 (en) * | 2009-02-09 | 2010-12-20 | Fmc Kongsberg Subsea As | Link for use in a riser, riser with such a link and method for increasing the operating window of a riser |
| US8496409B2 (en) | 2011-02-11 | 2013-07-30 | Vetco Gray Inc. | Marine riser tensioner |
| GB2533783B (en) * | 2014-12-29 | 2019-06-05 | Cameron Tech Ltd | Subsea support |
| US10174566B2 (en) | 2016-03-02 | 2019-01-08 | Vetco Gray, LLC | Inverted pull-up riser tensioner |
| WO2019141322A1 (en) * | 2018-01-17 | 2019-07-25 | Maersk Drilling A/S | Offshore drilling rig assembly and method |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3643751A (en) * | 1969-12-15 | 1972-02-22 | Charles D Crickmer | Hydrostatic riser pipe tensioner |
| US3739844A (en) * | 1971-04-28 | 1973-06-19 | Shell Oil Co | Apparatus for carrying out underwater wellhead operations |
| US4004532A (en) * | 1975-05-05 | 1977-01-25 | Western Gear Corporation | Riser tension system for floating platform |
| US4200054A (en) * | 1976-12-10 | 1980-04-29 | Elliston Thomas L | Stabilized hoist rig for deep ocean mining vessel |
| US4359095A (en) * | 1980-08-04 | 1982-11-16 | Conoco Inc. | Well support system |
| US4367981A (en) * | 1981-06-29 | 1983-01-11 | Combustion Engineering, Inc. | Fluid pressure-tensioned slip joint for drilling riser |
-
1983
- 1983-03-03 CA CA000422813A patent/CA1205740A/en not_active Expired
- 1983-03-04 FI FI830746A patent/FI830746L/en not_active Application Discontinuation
- 1983-03-04 EP EP83301178A patent/EP0088608A3/en not_active Withdrawn
- 1983-03-04 NO NO830764A patent/NO830764L/en unknown
- 1983-03-04 DK DK109383A patent/DK109383A/en not_active Application Discontinuation
- 1983-03-05 JP JP3653083A patent/JPS58173289A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DK109383D0 (en) | 1983-03-04 |
| FI830746L (en) | 1983-09-06 |
| EP0088608A3 (en) | 1984-07-11 |
| DK109383A (en) | 1983-09-06 |
| EP0088608A2 (en) | 1983-09-14 |
| JPS58173289A (en) | 1983-10-12 |
| FI830746A0 (en) | 1983-03-04 |
| NO830764L (en) | 1983-09-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |