CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is related to copending and commonly assigned patent application entitled "MARINE SUBSEA RISER SYSTEMS AND METHODS", Attorney Docket No. 500005, filed contemporaneously herewith and incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND

[0003] The present disclosure relates in general to systems and methods useful in marine hydrocarbon exploration, production, well drilling, well completion, well intervention, and containment and disposal fields. During offshore operations, a riser system couples the ship at the sea surface to the sea bed along with the subsea drilled earthen borehole for recovering hydrocarbons. Riser systems have been used during drilling, production/injection, completion/workover, and export operations. A drilling riser can be deployed below a drill ship, commonly known as a mobile offshore drilling unit (MODU). The drilling riser connects at the seabed to a wellhead, generally, and, more specifically, to a lower marine riser package (LMRP) and blow out preventer (BOP). For well control and intervention situations, and for wells completed with vertical subsea trees, a Completion Workover Riser (CWOR) system may be used. To produce and/or contain hydrocarbons from a well, a production riser system may be used, including quick-connect/disconnect systems.

[0004] In any of the various systems mentioned above, the riser connection between a subsea source and a surface vessel will be exposed to the forces of the surrounding sea. For example, sea currents may act directly upon the riser. Likewise, sea surface motion can cause the surface vessel to move relative to the stationary wellhead where the riser is connected subsea. The draft of the vessel will change as hydrocarbons are stored aboard the vessel, causing longitudinal motion of the riser. The movements and forces caused by these actions, such as buckling or torque, can create stresses in the riser.

[0005] Accordingly, there remains a need for a riser connector or sub that can accommodate the movements and forces acting upon the riser while preventing the stresses to the riser. More particularly, there remains a need for a riser connector or sub that can accommodate various directions or kinds of movements, such as longitudinal, or axial, and rotational, while maintaining a substantially stress-free connection between the subsea source and the surface vessel.

SUMMARY

[0006] A riser connector includes two bodies coupled such that the two bodies exhibit longitudinal, or axial, movement and rotational movement relative to each other. The connector may include a sub having a first tubular body telescopically received within a second tubular body. The tubular bodies are axially moveable relative to each other. The tubular bodies are rotationally moveable relative to each other. The coupling between the tubular bodies includes a series of chambers, bores, ports, flowpaths, and radial, cross-sectional areas that interact to provide axial and rotational movement within the sub while being connected into a riser system disposed in a subsea environment. In some embodiments, the coupling between the tubular bodies is not influenced by a pressure difference between a fluid internal to the sub and a fluid external to the sub.

[0007] In certain embodiments, a subsea riser connector includes a first body telescopically received within a second body, an inner flow bore through the first and second bodies, a chamber disposed between the first and second bodies, a sliding seal disposed in the chamber and slidingly engaged with the first and second bodies, and a cylindrical interface between the first body and the second body to enable relative axial movement and relative rotational movement between the first and second bodies. The sliding seal may separate the chamber into a first chamber portion and a second chamber portion. The first chamber portion may include a port in fluid communication with the inner flow bore. The second chamber portion may include a port in fluid communication with an exterior of the first and second bodies. An effective area Ai at an end of the first body disposed in a flow bore of the second body may receive a pressure Pi in the inner flow bore. An annular area AA in the first chamber portion may receive the pressure Pi from the inner flow bore. The effective area Ai may be substantially equal to the annular area AA. The annular area AA may be greater than the effective area Ai. The first chamber portion may include a stop. The second chamber portion may include a stop. The first chamber portion may include a biasing spring.

[0008] In some embodiments, the first chamber portion includes a port having a one-way valve disposed between the first chamber portion and an exterior of the first and second bodies. The second chamber portion may include a port in fluid communication with the exterior of the first and second bodies. An effective area Ai at an end of the first body disposed in a flow bore of the second body may receive a pressure Pi in the inner flow bore. The one-way valve may be configured to communicate a pressurized fluid to the first chamber portion and bias the connector.

[0009] In some embodiments, the cylindrical interface may include a first cylindrical surface at an end of the first body mating with a second cylindrical surface in a flow bore of the second body. A sliding seal may be disposed between the first and second cylindrical surfaces. The first cylindrical surface may be axially moveable and rotatable relative to the mating second cylindrical surface. The cylindrical interface may include a third cylindrical surface on the first body opposite the chamber from the first cylindrical surface, with the third cylindrical surface mating with a fourth cylindrical surface in the second body opposite the chamber from the second cylindrical surface. The third cylindrical surface may be axially moveable and rotatable relative to the mating fourth cylindrical surface.

[0010] In some embodiments, a subsea riser system includes a first body telescopically received within a second body, a riser coupled to the first and second bodies, an inner flow bore through the first and second bodies, the inner flow bore in fluid communication with an inner flow bore of the riser, a chamber disposed between the first and second bodies, a sliding seal disposed in the chamber and slidingly engaged with the first and second bodies, and a cylindrical interface between the first body and the second body to enable relative axial movement and relative rotational movement between the first and second bodies. A biasing force may be included in the chamber to put the riser in tension. The cylindrical interface may include a plurality of mating cylindrical surfaces between the first and second bodies wherein each mating cylindrical surface is axially moveable and rotatable relative to an opposing mating cylindrical surface.

[0011] A method of connecting to a subsea riser includes telescopically receiving a first body within a second body, coupling the first and second bodies to a subsea riser, axially moving the first and second bodies relative to each other at a cylindrical interface disposed between the first and second bodies in response to a tension or compression force on the riser, and rotationally moving the first and second bodies relative to each other at the cylindrical interface in response to a torque on the riser. The method may further include communicating a fluid through an inner flow bore of the first and second bodies. The method may further include communicating the fluid to a first chamber portion of a chamber between the first and second bodies. The method may include pressure balancing the first and second bodies in response to communicating the fluid to the first chamber portion. The method may include communicating an exterior fluid to a second chamber portion of the chamber. The cylindrical interface may include multiple sets of mating surfaces, and the method may further include axially moving and rotationally moving each set of mating surfaces. The method may include biasing the first and second bodies toward each other to place the subsea riser in tension.

[0012] Thus, embodiments described herein include a combination of features and advantages intended to address various shortcomings associated with certain prior devices, systems, and methods. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which:

[0014] Figure 1 is a schematic view of an embodiment of an offshore drilling or production riser system;

[0015] Figure 2 is a longitudinal cross-section view of a subsea telescoping and rotatable sub that can be coupled into the riser of Figure 1 , in accordance with the principles disclosed herein;

[0016] Figure 3 is an elevational view of an inner mandrel of the sub of Figure 2;

[0017] Figure 4 is a perspective view of the sub of Figure 2;

[0018] Figure 5 is a partial cross-section view of another embodiment of the subsea telescoping and rotatable sub of Figure 2;

[0019] Figure 6 is a partial cross-section view of yet another embodiment of the subsea telescoping and rotatable sub of Figure 2;

[0020] Figure 7 is a partial cross-section view of a further embodiment of the subsea telescoping and rotatable sub of Figure 2; and

[0021] Figure 8 is a partial cross-section view of a dual or hybrid chamber embodiment of the subsea telescoping and rotatable sub of Figure 2.

DETAILED DESCRIPTION

[0022] In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals, respectively. Certain terms are used throughout the description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components 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 invention 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 invention, and is not intended to limit the invention 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.

[0023] The terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to... ." Unless otherwise specified, any use of any form of the terms "couple", "attach", "connect" 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. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms "axial" and "axially" generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms "radial" and "radially" generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis. A "subsea source" includes any subsea location where hydrocarbons are produced, communicated, or contained.

[0024] Referring initially to Figure 1, an embodiment is illustrated schematically of an offshore system 100 for deepwater subsea containment, disposal, production, and well intervention. While many of the apparatus, systems, and methods described herein were developed and used in the context of containment and disposal, it is explicitly noted that the apparatus, systems, and methods described herein are not restricted to containment and disposal operations, but may be used in drilling or in conjunction with any subsea source.

[0025] The system 100 includes a lower riser assembly or LRA 4 including a wellhead housing 2. In some embodiments, the wellhead housing 2 is a substantially cylindrical member. In certain embodiments, the wellhead housing 2 may be configured for or include components for other operations as noted above. The wellhead housing 2 may include or be coupled to a BOP for drilling operations. The wellhead housing 2 includes one or more male/female subsea connectors 26 used for coupling to various subsea equipment related to the riser systems and other operational systems noted herein. On some embodiments, the wellhead 2 and the connectors 26 may be part of a Christmas tree arrangement as is known in the industry. The wellhead 2 is affixed to a bottom plate 96, for example, by welding or bolting. The bottom plate 96 is in turn attached by welding, bolting, or some other mechanism to a seabed foundation 54, which may be any solid foundation. The seabed foundation may surround or otherwise be adjacent an earthen drilled borehole 8 for producing hydrocarbons.

[0026] The wellhead housing 2 fluidly and mechanically couples to a lower riser portion or tubular string 6 of a riser 10. The riser 10 may include a series of connected tubulars, such as drill pipe sections or joints. The riser may also include other subsea tubulars for coupling the subsea source to a surface vessel 28. In certain system embodiments the riser joints may be constructed using high strength steel tubulars using threaded coupled connectors. The riser 10 includes an upper riser portion 24 to fluidly and mechanically couple with the vessel 28 in a known fashion. During installation from the surface vessel 28 at sea surface 50, certain known apparatus may be used to help guide the riser 10 and the lower riser portion 6 into a connection with the wellhead 2. Once connected, the riser 10 may experience stresses due the movements and forces of the sea imposed upon the system 100 as previously described. In certain embodiments, a telescoping and rotatable connector or sub 20 is coupled into the riser 10 to accommodate these imposed movements and forces and to reduce the stresses in the riser 10.

[0027] For ease of description, the telescoping and rotatable connector or sub 20 may also be referred to simply as connector 20 or sub 20. The sub 20 generally includes a head or first tubular body 22 including a telescoping section or inner mandrel 21 received within a housing or second tubular body 60. The head 22 is rotatable relative to the housing 60 and may swivel in response to rotation of the surface vessel 28. The head 22 is also axially (i.e., the direction of the longitudinal axis of the riser 10 between the wellhead 2 and the vessel 28) moveable relative to the housing 60 such that the sub 20 is expandable and contractible. The connection or coupling between the inner mandrel 21 and the housing 60 is configured to absorb these movements, as will be described in greater detail below.

[0028] Referring now to Figure 2, a longitudinal cross-section view of the sub 20 illustrates further details of the telescoping and rotatable aspects of the sub 20. For simplicity and ease of description, certain details of the sub 20 are not shown. For example, connections required for assembly and disassembly of the sub 20 are not shown. The sub 20 includes the first tubular body 22, or the head, received within the second tubular body 60, or the housing. The coupled first body 22 and the housing 60 include a shared longitudinal axis 25. The first body 22 includes an end 30 having an outer surface 35 with an outer diameter 34. At a shoulder 32, the first body 22 is reduced in diameter to an outer surface 40 of the inner mandrel 21. At an intermediate location on the inner mandrel 21, the outer surface 40 transitions to an increased diameter portion 42 and then to a reduced outer diameter surface 46 that terminates at an end 48 of the inner mandrel 21. The reduced outer surface 46 includes a diameter 49. The inner mandrel 21 includes an inner bore 36 having an inner surface diameter 38.

[0029] The housing 60 includes a first end 62, a second end 64, and an outer surface 65 having the outer diameter 34 extending between the ends 62, 64. An inner surface 66 at the second end 64 contacts and slidingly engages the mandrel surface 40 as shown and together define an interface therebetween. Accordingly, the inner surface 66 is substantially the same diameter 67 as the surface 40. The inner surface 66 transitions to an increased diameter surface 74 at a shoulder 68. The surface 74 extends to another shoulder 76 to form a chamber 70 with the outer surfaces 40, 42, 46 of the inner mandrel 21. A seal 44, such as an o-ring shaped sliding seal, for example, is disposed about the increased diameter portion 42 and slidingly engaged with the inner housing surface 74. Thus, the increased diameter portion 42 (along with the remainder of the first body 22) and the inner housing surface (along with the remainder of the housing 60) are axially moveable along and rotatable about the axis 25 relative to each other. In some embodiments, the sliding seal 44 is substantially stationary on the increased diameter portion 42, and thus is slidable along the inner housing surface 74 and rotatable on the inner housing surface 74. In some embodiments, the first body 22 moves axially and/or rotates relative to the substantially stationary housing 60. In other embodiments, the housing 60 moves axially and/or rotates relative to the substantially stationary first body 22. In still other embodiments, there is combined axial and/or rotational movement of both the first body 22 and the housing 60.

[0030] The increased diameter portion 42 and the seal 44 separate the chamber 70 into a first chamber portion 70a and a second chamber portion 70b. The inner mandrel 21 includes a first port 72 extending between the inner flow bore 36 and the outer surface 40 such that the first chamber portion 70a is able to fluidly communicate with the inner flow bore 36. In some embodiments, the inner mandrel 21 includes additional ports 72 between the inner flow bore 36 and the first chamber portion 70a. The housing 60 includes a second port 78 and a third port 79 extending between the surfaces 74, 65 such that the second chamber portion 70b is able to fluidly communicate with the exterior of the sub 20, or the surrounding sea water 29 at a pressure P _s . In some embodiments, the housing includes more or less than the two ports 78, 79.

[0031] Still referring to Figure 2, the mandrel end 48 is disposed in a bore 84 in the housing 60. The bore 84 includes an inner surface 80 that shares substantially the same diameter 49 as the outer mandrel surface 46 such that inner surface 80 contacts and slidingly engages the outer mandrel surface 46 as shown and defines an interface therebetween. The bore 84 transitions to a reduced diameter bore 86 at a tapered surface 82. The reduced bore 86 includes the diameter 38 also shared with the inner flow bore 36 of the first body 22.

[0032] In some embodiments, in addition to the axially slidable and rotatable sliding seal 44, other sliding seals 88, 90 may be provided at the surface interfaces 40, 66 and 46, 80 such that these interfaces are sealed while also promoting relative axial and rotational movement between the first body 22 and the housing 60. However, in some embodiments, other types of seals are located at 88, 90, or no seals are provided though the relative axial and rotational movement at the interfaces 40, 66 and 46, 80 remain to promote the movements in the sub 20 as just described.

[0033] In operation, the sub 20 is coupled into a riser 10 of a subsea system 100 as shown in Figure 1. In some embodiments, the first body end 30 is coupled to the upper riser portion 24 and the housing end 62 is coupled to the lower riser portion 6 using known means. In such an embodiment, the sub 20 is coupled into an intermediate location of the riser 10 between upper 24 and lower 6 portions of the riser 10. In other embodiments, the sub 20 may be coupled into a lower portion 6 of the riser 10, such that the first body end 30 is coupled to the riser 10 and the housing end 62 is coupled to the wellhead 2, an attachment on the wellhead 2, or another component associated with the wellhead 2 or other equipment at the subsea source. In some embodiments, the housing end 62 is coupled to the upper riser portion 24 or the riser 10, and the first body end 30 is coupled to the lower riser portion 6 or the wellhead associated equipment.

[0034] While coupled to the riser 10, a flow in either direction in the riser 10 is received by a flow path 92 including the inner flow bores 36, 84, 86. The fluid flow path 92 may direct hydrocarbon production from the borehole 8 and the subsea source to the surface vessel 28, or it may direct an injection fluid flowing in the opposite direction. Other types of flows are also contemplated according to the other systems described herein. The fluid flow along the path 92 can include a pressure Pi that is communicated to and acts upon an effective area A; at the radial terminal end 48 of the inner mandrel 21. Referring to Figure 3, the effective area A; is shown extended across the radial plane of the end 48 and the inner flow bore 26, and includes the diameter 49. The pressure Pi is also communicated to the first chamber portion 70a via the port 72, and acts upon an annular area AA that includes the radial or diameter difference between the mandrel surfaces 40 and the inner housing surface 74. The opposing chamber portion 70b is at seawater or ambient pressure P _S via the ports 78, 79, thus the pressure Pi at AA is opposed mainly by the pressure Pi at the effective area A;. In some embodiments, Ρ;Α; is substantially equal to P A such that the sub 20 is pressure balanced across the increased diameter portion 42, meaning there is substantially no biasing force acting on the first body 22 and the housing 60 to push these bodies toward or away from each other. In this manner, the increased diameter portion 42 also acts as a piston and may be referred to as the piston 42 herein. In such embodiments, the effective internal area A; is substantially equal to the annular chamber area AA. Accordingly, the first body 22 and the housing 60 can move axially, or telescope, relative to each other without being impeded by axial biasing forces caused by the pressure Pi which would otherwise act to push the piston 42 against the shoulder 68.

[0035] In some embodiments, the sub 20 may include additional "stages" to provide additional areas for pressure balancing. For example, additional pistons 42 with seals 44 can be disposed along the inner mandrel 21 to provide further annular chamber area AA. In further embodiments, the sub 20 may include further effective areas for receiving the pressure Pi.

[0036] In still further embodiments, the annular area AA can be larger than the effective internal area A;. Assuming the pressure Pi continues to act on the areas at AA, A; as described above, then PJAA is greater than Pi . Consequently, a biasing force is provided in the first chamber portion 70a that contracts the sub 20 and enables a tensioning force relative to the riser 10 into which the sub 20 is coupled. Such a biasing or tensioning force in the sub 20 can counteract weights or forces of structures coupled below the sub 20.

[0037] While being pressure balanced as described, the sub 20 is able to expand and contract by virtue of axially slidable interfaces 46, 80 and 40, 66, along with the sliding seal 44. The surfaces 46, 80, 40, 66, 74 are mating circular or cylindrical surfaces that are free to slide relative to each other, thus allowing relative axial movement between the first body 22 and the housing 60. Further, the cylindrical interface 46, 80, the cylindrical interface 40, 66, and the cylindrical interface between the sliding seal 44 and the surface 74 enable the contacting surfaces to rotate relative to each other. Accordingly, the first body 22 and the housing 60 are free to rotate relative to each other, or swivel. Each cylindrical interface between the inner mandrel 21 and the housing 60 are configured for both axial and rotational movement, such that there are no impedances to expansion/contraction and swiveling of the sub 20.

[0038] Referring now to Figure 4, a perspective view of the sub 20 illustrates the movements of the sub 20 from an exterior view. As previously described, the first body 22 is telescopically disposed in the housing 60. One or more cylindrical surface interfaces are configured for dual axial and rotational movement between the first body 22 and the housing 60 of the sub 20. A cylindrical sealing interface provided between the chamber seal 44 and the housing surface 74 enables a dual axial and rotational movement 110 between the first body 22 and the housing 60. A first cylindrical interface provided at surfaces 46, 80 enables another dual axial and rotational movement 1 12. A second cylindrical interface provided at surfaces 40, 66 enables yet another dual axial and rotational movement 108. Together, these interfaces provide a combined cylindrical interface that aggregates the movements 108, 1 10, 1 12, resulting in axial movement or expansion/contraction of the sub 20 at 102 and rotational movement or swiveling of the sub 20 at 104, 106.

[0039] Referring now to Figure 5, a partial cross-section view of an alternative embodiment of the sub 20 is shown. Many of the features shown in Figure 5 are similar to features shown in Figure 2 for the sub 20. Consequently, common features between Figures 2 and 5 may not be described in detail in the following discussion, though similarity between reference numerals is maintained for ease of reference. The longitudinal cross-section view of Figure 5 depicts a sub

220 similar to the sub 20 of Figure 2, but also different in certain respects. It is noted that only one half of the sub 220 is shown, as taken about an axis 225.

[0040] The sub 220 includes a first body 222 with an inner mandrel 221 received within a housing 260. In some embodiments, the first body 222 includes a connector or thread 223 and the housing 260 includes a connector or thread 261. The first body 222 includes a shoulder surface 232 facing a shoulder surface 264 of the housing 260. The shoulder surfaces 232, 264 are separated by a gap or space 235. An increased diameter portion 242 of the inner mandrel

221 separates a first chamber portion 270a from a second chamber portion 270b, and is slidable along a surface 274 via a sliding seal 244. The first chamber portion 270a is exposed to an internal pressure Pi via a port 272 and the second chamber portion 270b is exposed to an exterior or sea water pressure P _s via a port 279. A shoulder 268 adjacent the first chamber portion 270a is provided with a step or stop 275. The stop 275 includes a first surface 273 and a second surface 277. The increased diameter portion 242 includes a step or stop 245 extending into the second chamber portion 270b. The stop 245 includes a first surface 243 and a second surface 247.

[0041] During operation of the sub 220, if the first body 222 and the housing 260 are being forced away from each other such that the gap 235 is increasing, the stop 275 may act as a stop against the increased diameter portion 242, or piston 242, before the piston 242 reaches the shoulder 268. If the piston 242 contacts the first surface 273 of the stop 275, a sub-chamber defined piston 242, the shoulder 268, and the second stop surface 277 remains to receive the pressure Pi and maintain the pressure balancing effect as previously described. If the piston 242 is allowed to fully contact and engage the shoulder 268, the port 272 may be completely sealed off from the first chamber portion 270a at a surface 266 and the pressure balancing effect may be lost. The stop 275 prevents full contact between the piston 242 and the shoulder 268. [0042] Similarly, the stop 245 may engage a shoulder 276 of the second chamber portion 270b. When the first body 222 and the housing 260 are moving toward each other such that the gap 235 is decreasing, the first surface 243 of the stop 245 can engage the shoulder 276 so that the piston 242 is prevented from contacting the shoulder 276. Consequently, a sub-chamber defined by the piston 242, the shoulder 276, and the second stop surface 247 remains to receive the pressure P _s and maintain the pressure balancing effect as previously described. If the piston 242 is allowed to fully contact and engage the shoulder 276, the port 279 may be completely sealed off from the second chamber portion 270b by the piston 242 and the pressure balancing effect may be lost. The stop 245 prevents full contact between the piston 242 and the shoulder 276. The cylindrical interfaces, as previously described with respect to the sub 20 and which are included in the sub 220, continue to enable the sub 220 to both telescope axially and rotate in response to riser forces.

[0043] Referring now to Figure 6, a partial cross-section view of another embodiment of the subs 20, 220 is shown. As stated previously, common features with previous embodiments may not be shown or described in the interest of clarity and simplicity. Instead, the following discussion focuses on different features of a sub 320 while attempting to maintain similarity between reference numerals used. The longitudinal cross-section view of Figure 6 depicts the sub 320 similar to the subs 20, 220, but also different in certain respects. It is noted that only one half of the sub 320 is shown, as taken about an axis 325.

[0044] The sub 320 includes a first body 322 with an inner mandrel 321 received within a housing 360. In some embodiments, the first body 322 includes a connector or thread 323 and the housing 360 includes a connector or thread 361. The first body 322 includes a shoulder surface 332 facing a shoulder surface 364 of the housing 360. The shoulder surfaces 332, 364 are separated by a gap or space 335. An increased diameter portion 342 of the inner mandrel 321 separates a first chamber portion 370a from a second chamber portion 370b, and is slidable along a surface 374 via a sliding seal 344. The first chamber portion 370a is exposed to an internal pressure Pi via a port 372 and the second chamber portion 370b is exposed to an exterior or sea water pressure P _s via a port 379. A shoulder 368 adjacent the first chamber portion 370a is opposed to the increased diameter portion 342 to axially contain a biasing spring 395 in the first chamber portion 370a.

[0045] During use of the sub 320, the biasing spring 395 provides an axial biasing force in the first chamber portion 370a that acts on the shoulder 368 and the increased diameter portion 342, or piston 342, to push the first body 322 and the housing 360 toward each other. Consequently, the gap 335 tends to decrease and the sub 320 tends to contract if the biasing force is unopposed by other forces. During use in the riser 10, the biasing spring 395 enables a tensioning force relative to the riser 10 into which the sub 320 is coupled. Such a biasing or tensioning force in the sub 320 can counteract weights or forces of structures coupled below the sub 320. A series of sliding seals 344, 388, 390 and the associated, respective cylindrical surfaces as described herein enable the spring-biased sub 320 to both telescope and rotate in response to forces applied to the sub 320.

[0046] In a further embodiment, and referring to Figure 7, a sub 420 replaces the biasing spring 395 with a gas spring or gas chamber 489 in a first chamber portion 470a. A valve 487 is coupled into a port 485 that is in fluid communication with the first chamber portion 470a. A port in an inner mandrel 421, such as the ports 72, 272, 372, is no longer needed. In some embodiments, any one of the ports 72, 272, 372 is plugged. In some embodiments, the valve 487 may be a one-way valve. In certain embodiments, the valve 487 may be a one-way valve stem, or a tire valve stem. In other embodiments, the valve 487 is a hand-operated valve, or other known two-way valves. The valve 487 may receive a pressurized gas or fluid and communicate the pressurized gas to the spring or chamber 489 while also preventing the pressurized gas from escaping. Consequently, a biasing force is provided in the first chamber portion 470a similar to the biasing force provided by the biasing spring 395. In some embodiments, a second chamber portion 470b is in fluid communication with the exterior sea water and a pressure P _s via a port 479. In other embodiments, the port 479 is plugged or closed, or is eliminated, and the second chamber portion 470b includes or is maintained at atmospheric pressure. Such an atmospheric pressure chamber portion can also be seen in Figure 8 and discussed below.

[0047] Referring now to Figure 8, an alternative embodiment sub 520 includes a hybrid or stacked arrangement of multiple pressurized chambers, each pressurized chamber similar to ones included with other embodiments described herein. The sub 520 includes a first set of chamber portions 570a, 570b similar to the chamber portions 470a, 470b of the sub 420 of Figure 7. The chamber portions 570a, 570b include related structures and features similar to the chamber portions 470a, 470b of the sub 420, wherein similar reference numerals are used to denote similar features. For example, the piston 442 in Figure 7 is the same as a piston 542 of the sub 520 in Figure 8. Thus, particular reference can be made to Figure 7 and associated text for additional details of the sub 520, including for a first body 522 and a housing 560. However, one feature is different. Instead of having the port 479, the housing 560 of the sub 520 does not include the port 479 and instead the chamber portion 570b is an atmospheric chamber as discussed above with respect to the additional embodiments for the sub 420 of Figure 7.

[0048] The sub 520 also includes a second pressurized chamber disposed axially adjacent the first set of chamber portions 570a, 570b. A second set of chamber portions 670a, 670b similar to the chamber portions 270a, 270b of the sub 220 of Figure 5 are coupled or attached to a shoulder area 568 and what was the surface 464 in Figure 7. The chamber portions 670a, 670b include related structures and features similar to the chamber portions 270a, 270b of the sub 220, wherein similar reference numerals are used to denote similar features. For example, the piston 242 in Figure 5 is the same as a piston 642 of the sub 520 in Figure 8. Thus, particular reference can be made to Figure 5 and associated text for additional details of the chamber portions 670a, 670b of the sub 520. Consequently, the housing 560 includes dual, or stacked, pressurized chambers in the form of chamber portions 570a, 570b and chamber portions 670a, 670b. Further, the sub 520 includes the first piston 542 and the second piston 642.

[0049] During use, the chamber portions 670a, 670b enable the pressure balancing function as described for the sub 220 of Figure 5. Further, the chamber portions 570a, 570b enable the pressurized gas biasing function as described for the sub 420 of Figure 7. In alternative embodiments, the chamber portions 570a, 570b can be replaced with the chamber portions 370a, 370b and the biasing spring 395 of Figure 6 to enable a spring-based biasing force in the sub 520. In this manner, a single sub 520 can be equipped with stacked chambers that enable the pressure balancing function of the sub 220 of Figure 5 and the biasing force function of any one of the subs 220, 320, 420 of Figures 5, 6, and 7, respectively.

[0050] Described herein are riser systems connecting a subsea source to a surface vessel, which may be a drill ship such as a MODU or other vessel including a drilling rig. Certain embodiments include a near-vertical riser having a lower end and an upper end, the upper end of the riser mechanically and fluidly connected to the surface vessel. Certain embodiments described herein include a telescopically rotatable connector or sub disposed in an intermediate portion of the riser between the lower and upper ends, or at a lower end of the riser and connectable to wellhead equipment. The telescopically rotatable sub includes an inner cylindrical interface that facilitates both relative axial movement and relative rotational movement between two telescopically received tubular bodies of the sub. The inner cylindrical interface may include multiple sets of mating seals and surfaces or mating surfaces, all of which are configured for axial relative movement and rotational relative movement. The two bodies may include a chamber between them, with a sliding seal disposed therein and engaging both of the bodies. The divided chamber can be pressurized so as to pressure balance the two tubular bodies of the sub. Consequently, the axial and rotational movements of the sub in response to subsea forces are unimpeded by pressure biasing forces in the sub.

[0051] While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments as described are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.