EXPANDABLE FAIRING OF WEATHERVANING RISER JOINT

BACKGROUND

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

Advances in the petroleum industry have allowed access to oil and gas drilling locations and reservoirs that were previously inaccessible due to technological limitations. For example, technological advances have allowed drilling of offshore wells at increasing water depths and in increasingly harsh environments, permitting oil and gas resource owners to successfully drill for otherwise inaccessible energy resources. To drill for oil and gas offshore, it is desirable to have stable offshore platforms and/or floating vessels from which to drill and recover the energy resources. Techniques to stabilize the offshore platforms and floating vessels include, for example, the use of mooring systems and/or dynamic positioning systems.

However, these systems may not always adequately stabilize components descending from the offshore platforms and floating vessels to the seafloor wellhead.

For example, a riser string or riser (e.g., a pipe or series of pipes, such as riser joints, that connects the offshore platforms or floating vessels to the floor of the sea) may be used to transport drill pipe, casing, drilling mud, production materials or hydrocarbons between the offshore platform or floating vessel and a wellhead. The riser is suspended between the offshore platform or floating vessel and the wellhead, and may experience forces, such as underwater currents, that cause deflection (e.g., bending or movement) or vortex induced vibrations (VIV) in the riser. Acceptable deflection can be measured by the deflection along the riser, and also at, for example, select points along the riser. These points may be located, for example, at the offshore platform or floating vessel and at the wellhead. If the deflection resulting from underwater current is too great, drilling must cease and the drilling location or reservoir may not be accessible due to such technological constraints. If the vibrations due to the currents are too great, the riser and/or the wellhead may experience accelerated fatigue damage.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of an offshore platform with a riser.

FIG. 2 illustrates an example of the offshore platform of FIG. 1 with the riser experiencing deflection.

FIG. 3 illustrates a first embodiment of a system to mitigate the deflection of the riser of FIG. 2.

FIG. 4 illustrates an exploded view of an elongated riser joint to mitigate the deflection of the riser of FIG. 2;

FIG. 5 illustrates a top view of the elongated riser joint with an expandable fairing;

FIG. 6 illustrates a perspective view of an embodiment of the expandable fairing in an expanded position;

FIG. 7 illustrates a perspective view of an embodiment of the expandable fairing in a collapsed position;

FIG. 8 illustrates a perspective view of an embodiment of a set of plates of the expandable fairing that are movable between the collapsed position and the expanded position;

FIG. 9 illustrates an embodiment of a plate of the expandable fairing with a rail and a channel;

FIG. 10 illustrates a top view of an embodiment of a tail segment of an expandable fairing in the collapsed position; and

FIG. 11 illustrates an embodiment of a method illustrating operations of assembling the expandable fairing;

FIG. 12 illustrates an embodiment of a method illustrating operations of assembling a riser string with the expandable fairing;

FIG. 13 illustrates an embodiment of a method illustrating operations of utilizing the expandable fairing;

FIG. 14 illustrates a perspective view of a second embodiment of an expandable fairing in an expanded position;

FIG. 15 illustrates a perspective view of a second embodiment of the expandable fairing in a collapsed position;

FIG. 16 illustrates an embodiment of a method illustrating operations of assembling a riser string with the expandable fairing of FIGS. 14 and 15; and

FIG. 17 illustrates an embodiment of a method illustrating operations of utilizing the expandable fairing of FIGS. 14 and 15.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Systems and techniques for stabilizing a riser (e.g., a riser string made up of a series of riser joints coupled to one another) extending from offshore platform, such as a drillship, a semi-submersible platform, a floating production system, or the like, are set forth below. During offshore drilling operations, high current or high loop current is sometimes occurred, and it may cause large drag force and/or deflection on the riser (e.g., especially for buoyancy joints of the riser, which may have diameters up to 55″ or more) and vortex induced vibrations (VIV), which can cause riser failure and, thus, require cessation of drilling and/or production operations. In some embodiments, fairings and/or helical strakes may be used along the riser. However, these helical strakes tend to aid in VIV suppression but not necessarily in reducing the drag force. Additionally, installation and removal of fairings and/or helical strakes may be time consuming, thus slowing operations of the offshore platform.

Accordingly, additional embodiments herein may include specialty riser joints with weathervaning geometries (e.g., drilling and/or production specialty riser joints that may form a portion or all of the riser) that are designed to operate to greatly reduce the drag coefficient and drag force on the riser. By altering the shape of the specialty riser joints from a cylindrical or circular shape to that of an elongated shape (e.g., an elliptical or airfoil shape), the drag coefficient and drag force of the specialty riser joints can be greatly reduced. Also, the VIV may be greatly reduced and/or eliminated. Reduction and/or elimination of VIV, such as via elongated riser joints and/or riser joints with expandable fairings, may decrease fatigue of the riser. Moreover, buoyant materials may be incorporated into the specialty riser joints to decrease a load suspended from the offshore vessel and/or a load on the riser string.

In some embodiments, some specialty riser joints have fairings with expandable segments. The portions of the fairings may be collapsed or retracted while stored with the riser joint, and extended before or upon attachment to the riser string. In some embodiments, the fairing portions may be manually extended, such as from a collapsed or retracted position. That is, some fairings may include telescoping portions that may be collapsed during storage and/or transport, then extended for use with the riser string.

When in use, the specialty riser joints may be fixed with respect to an axial, radial, and circumferential directions. In other embodiments, the elongated shape of the specialty riser joints may allow for the specialty riser joints to be fixed with respect to an axial and a radial direction, while capable of rotation in a circumferential direction. This circumferential motion may be in response to, for example, forces imparted to the specialty riser joints by currents. Through rotation of the specialty riser joints, the drag coefficient and drag force of specialty riser joints resulting from the shape thereof may be preserved even as currents change in the field. That is, the elongated shape of the specialty riser joints may enable portions of the riser string to weathervane to reduce the drag forces by the current on the riser string.

With the foregoing in mind, FIG. 1 illustrates an offshore platform includes an offshore vessel 10. Although the presently illustrated embodiment of an offshore vessel 10 is a drillship (e.g., a ship equipped with a drill rig and engaged in offshore oil and gas exploration and/or well maintenance or completion work including, but not limited to, casing and tubing installation, subsea tree installations, and well capping), other offshore platforms such as a semi-submersible platform, a floating production system, or the like may be substituted for the drillship. Indeed, while the techniques and systems described below are described in conjunction with a drillship, the techniques and systems are intended to cover at least the additional offshore platforms described above.

As illustrated in FIG. 1, the offshore vessel 10, with a derrick 11 thereon, includes a riser 12 extending therefrom. The riser 12 may include a pipe or a series of pipes (e.g., riser joints) that connect the offshore vessel 10 to the seafloor 14 via, for example, blow out preventer (BOP) 16 that is coupled to a wellhead 18 on the seafloor 14. These riser joints may include one or more of, for example, drilling riser joints, slick joints, buoyancy joints, pup joints, telescopic joints, production joints, or other types of riser joints as part of the riser 12. In some embodiments, the riser 12 may transport produced hydrocarbons and/or production materials between the offshore vessel 10 and the wellhead 18, while the BOP 16 may include at least one valve with a sealing element to control wellbore fluid flows. In some embodiments, the riser 12 may pass through an opening (e.g., a moonpool) in the offshore vessel 10 and may be coupled to drilling equipment of the offshore vessel 10. As illustrated in FIG. 1, it may be desirable to have the riser 12 positioned in a vertical orientation between the wellhead 18 and the offshore vessel 10, for example, to allow a drill string made up of drill pipes 19 to pass from the offshore vessel 10 through the BOP 16 and the wellhead 18 and into a wellbore below the wellhead 18. However, external factors (e.g., environmental factors such as currents) may disturb the vertical orientation of the riser 12.

As illustrated in FIG. 2, the riser 12 may experience deflection, for example, from currents 20. These currents 20 may apply forces on the riser 12, which causes deflection (e.g., motion, bending, or the like) in riser 12. Thus, when the offshore vessel 10 works under the existence of strong currents 20, the riser 12 will have significant horizontal deflection due to the drag loads applied along the riser 12. As a result, the angle 24 between the vertical axis 26 (e.g., an axis that is perpendicular to the seafloor 14 and extends vertically to the sea surface 28) and the bottom flex joint 30 may exceed tolerance levels for the performance of, for example, drilling operations.

This angle 24 may be modified through the dynamic positioning of the offshore vessel 10. That is, through the movement of the offshore vessel 10 in response to the currents 20, the angle 24 of the bottom flex joint 30 may be reduced and/or eliminated to meet any operational requirements associated with, for example, the BOP 16, the wellhead 18, and/or the riser 12. However, adjustment of the position of the offshore vessel 10 to reduce and/or eliminate the angle 24 of the bottom flex joint 30 may also increase the the angle 32 of top flex joint 34 beneath drill floor 36 with respect to the vertical axis 26. This may cause the portion of the riser 12 beneath the drill floor 36 as it passes through the moonpool 38 to interfere with the hull 39 of the offshore vessel 10. This interference between the riser 12 and the hull 39 is to be avoided.

Thus, force applied to the riser 12 from the currents 20 (or other environmental forces) may cause the riser 12 to stress the BOP 16 or cause key seating, as the angle 24 that the riser 12 contacts the BOP 16 may be affected via the deflection of the riser 12. Likewise, the currents 20 and/or efforts to mitigate the force of the currents 20 (e.g., dynamic positioning of the offshore vessel) may cause the riser 12 to contact the edge of the moonpool 38 of the offshore vessel 10. To reduce the deflection of the riser 12, and to reduce the chances of occurrence of the aforementioned problems caused by riser 12 deflection, additional systems and techniques may be employed.

FIG. 3 illustrates a system to mitigate the deflection of the riser 12. In some embodiments, reduction of the angle 32 and, indeed, deflection of the riser 12 as a whole may be accomplished through the use of one or more elongated riser joints 40 of the riser 12. These specialty riser joints (e.g., elongated riser joints 40) may be disposed along an entire length of the riser 12 or, for example, along one or more predetermined portions of the riser 12 that cumulatively result in a length of elongated riser joints 40 less than an entire length of the riser 12. In some embodiments, each elongated riser joint 40 may have a fixed geometry (e.g., a fixed shape and elongation). In other embodiments, at least one riser joint may be tapered such that the length of the elongation of the elongated riser joint 40 tapers along an axial distance of the elongated riser joint 40. Likewise, a series of elongated riser joints 40 may be utilized whereby each elongated riser joint 40 has a fixed elongation length, but the elongation lengths between elongated riser joints 40 differs (e.g., to allow for net tapering of the elongation of the elongated riser joints 40 when taken as a group). In some embodiments, the riser 12 includes elongated riser joints 40 along approximately 5 to 50 percent, 10 to 35 percent, 15 to 25 percent, or 20 percent of the distance (e.g., string length) from the offshore vessel 10 to the seafloor 14. One or more of the elongated riser joints 40 of the riser 12 is arranged proximate to the sea surface 28 and/or proximate to the depth of strong currents 20.

The elongated riser joints 40 may have an elongated shape such as an elliptical shape (which, may in some embodiments, include an offset of its center along a rotational axis, for example, axial direction 42), an airfoil shape (e.g., a fin, a blade, or a vane), a shape with a leading edge that tapers to a trailing edge (e.g., a teardrop), or the like. The elongated riser joints 40 have also have a non-circular shape as well as a non-cylindrical shape as the elongated shape. For example, the elongated riser joints may have one or more streamline bodies as the elongated non-circular and non-cylindrical shape. Indeed, while circular shaped riser joints may have a drag coefficient to approximately 1.2 for laminar flow, the elongated riser joints 40 may have a reduced drag coefficient of approximately 0.2˜0.6 along with reduced and/or eliminated VIV with respect to circular riser joints. An elongated riser joint 40 may be, for example, a buoyancy joint and the elongated riser joint 40 may have an elliptical cross section with a length to width ratio of approximately 2:1, which can reduce drag and drag coefficient to approximately 0.435 while also greatly reducing and/or eliminating VIV. As previously noted, the elliptical cross section of the elongated riser joints 40 may include a offset of their center to the rotation axis for example, axial direction 42, so as to create weathervane movement, rotation, or the like. In some embodiments, the amount of offset from the center of the elongated riser joints 40 may be chosen dependent on, for example, desired amount of rotation, the environment in which the elongated riser joints 40 will be utilized, or the like.

As illustrated in FIG. 3, and as will be discussed in greater detail below, the riser 12 with at least one elongated riser joint 40 may be disposed between the offshore vessel 10 and the seafloor 14, whereby the riser 12 includes at least one elongated riser joint 40 is disposed in an axial direction 42 (e.g., along a longitudinal axis). Also illustrated for reference is a radial direction 44, which may be used to describe, for example, a width of the elongated riser joint 40. Additionally, as will be discussed in greater detail below, at least one portion of the elongated riser joint 40 may rotate in a circumferential direction 46, for example, in response to currents 20, whereby the elongated riser joint 40 is elongated (e.g., may have an elongated shape) in the radial direction 44 (at a width of the elongated riser joint 40).

In some embodiments, the elongated riser joints 40 may be disposed along one or more predetermined portions of the riser 12 that cumulatively result in a length of elongated riser joints 40 less than an entire length of the riser 12. For example, determination of the location of the elongated riser joints 40 along the riser 12 may be determined based on the specific application in which the offshore vessel 10 is to be deployed. In some embodiments, charts may be developed based on measurements of the currents 20 at a particular drill site. Table 1 illustrates an example of such a chart:

TABLE 1

Depth (ft)
1 yr
10 yr

0
5.3
5.9

164
4.3
4.7

328
3.8
4.2

459
3.3
3.6

755
2.0
2.2

1115
1.6
2.1

1362
1.6
2.0

1788
1.2
1.3

2100
1.2
1.6

2461
1.5
2.3

3002
2.0
2.2

3412
2.0
2.9

4577
0.0
0.0

Table 1 describes the speed of currents 20 at particular depths over periods of time, for example, one year and ten years. Using this information, a determination of the location (e.g., depth) of an elongated riser joint 40, two or more consecutively disposed elongated riser joints 40 (e.g., two or more elongated riser joints 40 directly coupled to one another), and/or two or more non-consecutively disposed elongated riser joints 40 (e.g., two or more elongated riser joints 40 disposed along the riser 12 but not directly coupled with one another) can be made. Once this determination is made, disposing the elongated riser joint(s) 40 may occur. However, it may be appreciated that other information separate from or in addition to the information of Table 1 may be used in determining location(s) and/or numbers of elongated riser joints 40 disposed along the riser 12.

FIG. 4 illustrates an exploded view of the elongated riser joint 40. As illustrated, a buoyancy assembly 74 may include a metal frame inclusive of a band 70 as well as the one or more fasteners 56. The buoyancy assembly 74 may provide the elongated shape to the elongated riser joint 40, as the buoyancy assembly 74 may be the external portion (e.g., fairing) of the elongated riser joint 40 (e.g., via inclusion of buoyancy member 54, in which buoyancy foam may be selected and utilized as a portion of the buoyancy assembly 74). However, other non-foam buoyant materials may be used in place of buoyancy foam for the buoyancy member 54 as the outer portion of the buoyancy assembly 74. The buoyancy assembly 74 may have an elliptical shape, an airfoil shape (e.g., a fin, a blade, or a vane), a shape with a leading edge that tapers to a trailing edge (e.g., a teardrop), or the like so that the buoyancy assembly 74 (and, accordingly, the respective elongated riser joint 40), has an elongated non-circular shape as well as a non-cylindrical shape. As will be described in greater detail below, in some embodiments, the buoyancy assembly 74 may rotate in a circumferential direction 46 (i.e., weathervane) in response to external forces, such as currents 20.

The buoyancy assembly 74 may also include a bearing 76 that may be formed between the one or more fasteners 56 and may interconnect with (e.g., be rotatably coupled to) a clamp 72 to allow for rotation of fairings of the buoyancy assembly 74 and, thus, the buoyancy member 54, in a circumferential direction 46 about the main tube 58 to provide rotation of the buoyancy assembly 74 with respect to a flange 60. That is, the buoyancy assembly 74 (e.g., fairing) may be rotatably coupled to the main tube 58. The bearing 76 may interface with (e.g., be coupled to while still allowing for rotation about) a support 77 that surrounds the main tube 58 and the support 77 may itself be statically coupled to the main tube 58. Thus, the bearing 76 (and, accordingly, the buoyancy assembly 74) is rotatably coupled to (e.g., coupled to while still allowing for rotation about) the support 77 and may allow for rotation in a circumferential direction 46 about the support 77 (and, thus, the main tube 58). As illustrated, the support 77 may include one or more apertures to allow for passage of a choke line, a kill line, a hydraulic line, a booster line, or the like through the support along the main tube 58.

In some embodiments, the bearing 76 may be a plain bearing such as a bushing or a journal (e.g., radial or rotary) bearing. Likewise, the bearing 76 may be a rolling-element bearing (e.g., a rolling bearing) that carries the load of the buoyancy assembly 74 and/or the buoyancy member 54 via rolling elements (e.g., balls or rollers), while allowing for rotational motion (e.g., rotation of the buoyancy assembly 74 and, thus, the buoyancy member 54 coupled thereto in a circumferential direction 46 about the main tube 58). As illustrated, the buoyancy assembly 74 may additionally include support 78 in the region between the band 70 and the bearing 76. The material used for the support 78 may be identical to or different from the material of one or more of the buoyancy member 54 and a fixed buoyancy member 68 or, in some embodiments, the support 78 may be metal, such as a steel or other metallic plate, that may be utilized to hold one or more the buoyancy member 54 and the fixed buoyancy member 68 in place. Additionally, it should be noted that FIG. 5 illustrates a region 80 about the main tube 58 and the auxiliary lines (e.g., one or more of the choke and kill lines, the hydraulic line, and the booster line) that may be filled by the fixed buoyancy member 68 to form a circular rod with a circumference equal to or less than the radius of the clamp 72.

The elongated riser joint 40 may have one or more fairing segments 82 between bands 70 of the buoyancy assembly 74. While FIG. 5 illustrates the buoyancy assembly 74 of the elongated riser joint 40 with five sets of fairing segments 82, other embodiments of the buoyancy assembly 74 may have fewer fairing segments 82 (e.g., 1, 2, 3, 4) or more fairing segments 82. In some embodiments, each fairing segment 82 and band 70 may independently rotate about the main tube 58 in the circumferential direction 46.

FIG. 5 illustrates a top view 48 of the elongated riser joint 40. The elongated riser joint 40 may have a length 52 and a width equivalent to two times the length 52, such that the length to width ratio is 2:1. In some embodiments, the length 52 of the elongated riser joint 40 is between approximately 36 to 60 inches, 40 to 55 inches, or 50 inches. The length 52 of the elongated riser joint 40 is greater than or equal to a length across the main tube 58 of the elongated riser joint. As illustrated, the elongated riser joint 40 may include buoyancy member 54 that operates to provide buoyancy to the elongated riser joint 40 when submerged. The buoyancy member 54 may be a single enclosure that operates as an outer (exterior) portion, or a fairing, of the elongated riser joint 40. For example, the elongated riser joint 40 may have an elliptical shape, as illustrated with the phantom lines of FIG. 5. In some embodiments, the buoyancy member 54 may be two or more distinct enclosures (e.g., fairings) that may be affixed to one another via one or more fasteners 56 (e.g., screws, bolts, pins, locking mechanisms, or the like) or the two or more enclosures (e.g., fairings) may be permanently affixed (e.g., welded) to one another to combine to form an outer (exterior) portion of the elongated riser joint 40. As illustrated in FIG. 5, in some embodiments, the elongated riser joint 40 may be offset by a distance 55 away from its center 57 so that its rotational axis 59 is not along the center 57, but rather, adjusted by distance 55 away from the center 57, for example, to enhance the response of the elongated riser joint 40 with respect to changes to the directions of currents 20 (e.g., to aid in providing a weathervane effect).

As noted above, the one or more fairing segments 82 of the elongated riser joint 40 may be rotatable around the main tube 58. The main tube 58 may be configured for drill pipes 19 to pass through. As illustrated, the main tube 58 may be circular in shape and terminate in a flange 60 or a connector (e.g., a slick joint designed to prevent damage to the riser 12 and restrict lateral movement of one or more lines passing along the riser 12) with, for example, one or more apertures 62 through which choke and kill lines may pass, one or more apertures 64 through which a hydraulic line may pass, and one or more apertures 66 through which a booster line may pass. The flange 60 may allow for connection of the elongated riser joint 40 with another elongated riser joint 40 and/or a standard riser joint. The elongated riser joint 40 may also include fixed buoyancy member 68 that, for example, directly surrounds the main tube 58 and one or more of the choke and kill lines, the hydraulic line, and the booster line. The material used for the buoyancy member 54 and the fixed buoyancy member 68 of the fairing segments 82 may be identical or, for example, the material used for the buoyancy member 54 may be a non-absorbent (e.g., fluidly sealed) material while the material used for the fixed buoyancy member 68 may not necessarily be a non-absorbent (e.g., fluidly sealed) material.

As discussed above, the elongated riser joint 40 and fairing segments 82 thereof may have alternative shapes, such as an airfoil shape or a teardrop shape 84. The teardrop shape 84 may be formed from one or more fairing segments 82 around the main tube 58. As discussed in detail below, embodiments of the elongated riser joint 40 with the teardrop shape 84 may have a circular fairing segment 86 around a first portion of the main tube 58, and a tail fairing segment 88 around a second portion of the main tube 58. The tail fairing segment 88 may be at least partially collapsible, thereby enabling sections of the buoyancy assembly 74 (e.g., fairing) to be stored and/or stacked more efficiently than sections of the buoyancy assembly 74 with elliptical shapes and/or non-collapsible shapes. In some embodiments, a width 87 of the teardrop shape 84 along an expansion direction is between approximately 1.5 to 3.0 times the length 52 across the elongated riser joint 40. For example, the width 87 may be between approximately 80 to 120 inches, 90 to 100 inches, or approximately 92 inches. As discussed in detail below, an expandable fairing and/or buoyancy assembly 74 may be configurable in an expanded position and a collapsed position. In some embodiments, the expanded position may have an elongated shape, such as the teardrop shape 84 or an elliptical shape. In some embodiments, an expandable fairing may expand in one direction to have the teardrop shape 84. In some embodiments, an expandable fairing may expand in multiple directions, such as opposite directions. For example, an expandable fairing may have a generally circular shape in the collapsed position, and the expandable fairing may have an elliptical shape in the expanded position due to the extension of segments (e.g., nose segment, tail segment) of the expandable fairing in a first direction and a second direction. An expandable fairing with multiple segments configured may be configured to expand into multiple shapes. For example, an expandable fairing with a nose segment and a tail segment may be configured to expand into a teardrop shape with the tail segment extended in a first direction, an elliptical or airfoil shape with a nose segment extended in a second direction and the tail segment extended in the first direction, or a teardrop shape with the nose segment extended in the second direction.

In some embodiments, the collapsed position of the expandable fairing may have a generally circular shape that is narrower than the elongated shape. The collapsed position of the expandable fairing may have a width 89 that is between approximately 1.0 to 1.5 times the length 52 across the elongated riser joint. For example, the collapsed position of the expandable fairing may be between approximately 55 to 75 inches, 60 to 70 inches, or 65 inches. In some embodiments, the width 87 of the expandable fairing in the expanded position is between approximately 20 to 200 percent, 25 to 150 percent, or 40 to 100 percent greater than the width 89 of the expandable fairing in the collapsed position.

FIG. 6 illustrates a perspective view of an embodiment of an expandable fairing 90 that may form a portion of the elongated riser joint 40 of the riser 12 (e.g., as the fairing segment 82 of the elongated riser joint 40). The expandable fairing 90 may be an embodiment of a buoyancy assembly 74 that is neutrally buoyant, or that is buoyant. In some embodiments, the expandable fairing 90 may have the teardrop shape 84, where the tail fairing segment 88 of the teardrop shape 84 has two or more plates 92. For example, FIG. 6 illustrates the tail fairing segment 88 with a first set 94 of five plates 92 and a second set 96 of five plates 92. The plates 92 of each set may be coupled together to enable movement of the plates 92 relative to one another, thereby enabling the expandable fairing 90 to expand and contract. In some embodiments, an end plate 102 of the first set 94 of plates 92 is configured to couple to a respective end plate 102 of the second set 96 of plates 92. The plates 92 may include rails 98 and channels 100 to facilitate telescoping movement of the plates 92 relative to one another, thereby enabling the expandable fairing 90 to be expanded or collapsed. The expandable fairing 90 is illustrated in an expanded position 104 in FIG. 6, and is illustrated in a collapsed position 105 in FIG. 7. Additionally, or in the alternative, the plates 92 may be coupled to one another via hinges or folding members, thereby enabling the expandable fairing 90 to be expanded or collapsed. As discussed above, the expandable fairing 90 in the expanded position 104 may have a length 52 to width 87 ratio between approximately 1:1.5 to 1:3, and the expandable fairing in the collapsed position 105 may have a length 52 to width 89 ratio between approximately 1:1 to 1:1.5.

The expandable fairing 90 may have one or more fairing segments 82 that at least partially enclose the main tube 58 of the elongated riser joint 40 in the circumferential direction 46. For example, the expandable fairing 90 may have a body 106 that at least partially encloses the main tube 58. An axial gap 108 of the body 106 may facilitate installation of the body 106 around the main tube 58 of the riser 12 and/or may facilitate the routing of one or more hoses or cables (e.g., mux cables, a hot line hose, etc.) along the main tube 58. In some embodiments, the body 106 has two fairing segments 82 coupled at a location 110, such as via a hinge. In some embodiments, the body 106 has a circular fairing segment 86 coupled to tail fairing segments 88 at locations 114. Some embodiments of the expandable fairing 90 may have multiple fairing segments that may be extended, such as a tail fairing segment 88 to extend in a first direction and a nose segment to extend in a second direction, such as a direction opposite to the first direction. The fairing segments that may be extended may have an angular (e.g., pointed) shape, such as the tip of the teardrop shape 84, or a rounded shape.

A base plate 116 of each set of plates 92 of the expandable fairing 90 may be coupled to an extension 118 of the body 106 via a rigid or flexible connection (e.g., rails and channels, hinge). In the collapsed position 105 shown in FIG. 7, the one or more plates 92 of each set may be at least partially stored within a recess 120 between the extension 118 and a sleeve 122 of the body 106. In some embodiments, a storage feature 124 (e.g., lash, clasp) coupled to the extension 118 and/or the sleeve 122 may be configured to secure the set of plates 92 in the collapsed position 105. For example, the storage feature 124 may be coupled to the end plate 102 and the sleeve 122. Additionally, or in the alternative, the plates 92 may be secured in the collapsed position 105 without lashes or clasps, such as based at least in part on the weight of the plates 92, friction between the plates 92, the connection of the rails 98 and channels 100 of the plates 92, or any combination thereof. Prior to insertion of the elongated riser joint 40 with the expandable fairing 90 into the sea as a part of the riser string, a technician may manually adjust the plates 92 between the collapsed position 105 shown in FIG. 7 and the expanded position 104 shown in FIG. 6. For example, a technician may expand the plates 92 of the expandable fairing 90 prior to coupling the expandable fairing 90 to the elongated riser joint 40, or the technician may expand the plates 92 of the expandable fairing 90 while the elongated riser joint 40 is coupled to the riser string and the expandable fairing 90 is in the moon pool prior to insertion under the sea surface 28.

FIG. 8 illustrates a perspective view of an embodiment of the tail fairing segment 88 of the expandable fairing 90. The rails 98 and channels 100 of the plates 92 enable movement between the plates 92, thereby enabling the plates 92 to move between the expanded position 104 of FIG. 6 and the collapsed position of FIG. 7. One or more rails 98 arranged along a movement axis 130 of a set of plates 92 of the expandable fairing 90 are inserted into one or more respective channels 100 of an adjacent plate that are also arranged along the movement axis 130 of the set of plates 92. As discussed below, the shape of the rails 98 may interface with a mating surface of respective channels 100 to restrict movement of the plates 92 in the axial direction 42 and in a direction 136 away from a sliding face 131 of the plates 92, while the rails 98 and the respective channels 100 facilitate movement of the adjacent plates 92 along the movement axis 130 relative to one another.

In some embodiments, one or more of the rails 98 of a plate may have features (e.g., backstops 138, heads 142) that are configured to limit the extent of movement of an adjacent plate 92 engaged with the respective one or more rails 98. For example, the backstop 138 on the rail 98 may be configured to interface with a rear surface 140 of the adjacent plate 92 engaged with the rail 98 to limit the extent to which the adjacent plate 92 may be collapsed or retracted into the recess 120. Moreover, the head 142 on the rail 98 of a penultimate plate 144 of the first set 94 may be configured to limit the extension of the end plate 102 along the movement axis 130. In some embodiments, one or more rails 98 on each plate 92 have respective backstops 138 configured to limit the retraction of the adjacent plate 92 that interfaces with the one or more rails 98. In some embodiments, one or more rails 98 on each plate 92 have respective heads 142 configured to limit the extension of the adjacent plate 92 that interfaces with the one or more rails 98. Although the above discussed features are disposed on the rails 98, other features (e.g., narrowed channels, channel stops) of the channels 100 may also be configured to limit the extent of movement of adjacent plates 92.

One or more of the plates 92 of a set (e.g., first set 94, second set 96) may be modular plates 146. In some embodiments, the one or more modular plates 146 of a set may be assembled in any order and coupled to the body 106 of the expandable fairing 90. In some embodiments, the one or more rails 98 are arranged on an interior surface 132 of the modular plates 146, and one or more channels 100 are arranged on an exterior surface 134 of the modular plates 146. The modular plates 146 may have multiple sets of rails 98 and channels 100, such as 2, 3, 4, or 5 or more sets of rails 98 and channels 100. The rails 98 and channels 100 of each set may be spaced a modular distance 148 apart from each other, such as approximately 3, 6, 10, 12, 15, or 18 inches apart. In some embodiments, the channels 100 extend along a width 150 of the modular plates 146. The rails 98 may extend along all or a portion of the width 150, such as approximately 60 to 100 percent, 75 to 98 percent, or 80 to 95 percent of the width 150. In some embodiments, the width 150 of the modular plates 146 may be between 5 to 15 inches, 6 to 12 inches, or approximately 10 inches. In some embodiments, one or more plates 92 of a set may have a different arrangement and/or spacing's of rails 98 and channels 100, such as channels on the interior surface 132 and rails on the exterior surface 134, channels on both surfaces 132 and 134, rails on both surfaces 132 and 134, or any combination thereof.

The plates 92 of the expandable fairing 90 may be formed of a metal, a natural material, or a plastic material, such as polyurethane. In some embodiments, the plates 92 may be formed of a neutrally buoyant material. In some embodiments, the one or more rails 98 and/or one or more channels 100 are formed with a plate body 152, thereby reducing or eliminating subsequent tooling of the plates 92. For example, the one or more rails 98 and one or more channels 100 may be extruded or molded with the plate body 152. In some embodiments, the rails 98 and/or the channels 100 may be formed apart from the plate body 152, and coupled to the plate body 152, such as via fasteners, adhesives, or fusion with the plate body 152. In some embodiments, the rails 98 or the channels 100 may be formed via a tooling process of the plate body 152.

An embodiment of the rails 98 and channels 100 discussed above is illustrated in FIG. 9. Each rail 98 is configured to interlock with a respective channel 100 of the adjacent plate 92, thereby enabling movement of the plates 92 along the movement axis 130 while restricting movement in an axial direction 42. As illustrated in FIG. 9, a central element 160 of the rail 98 supports flanges 162 of the rail 98, and the flanges 162 are configured to slide within passages 164 of the channel 100. In some embodiments, the rails 98 and channels 100 may have wedge and/or dovetail relationships rather than the flanges 162 and passages 164 of FIG. 9. It is appreciated that alignment of the rails 98 with the channels 100 on opposite surfaces of the plate 92 with the modular distance enables the plate to be one of the modular plates 146 described above.

The plates 92 may be coupled to one another via insertion a tail end 166 of the rails 98 of one plate 92 into the channels 100 on the rear surface 140 of the adjacent plate 92. As discussed above, a backstop 138 on one or more of the rails 98 may be configured to interface with the rear surface 140 of an adjacent plate 92 to limit the movement along the movement axis 130. The backstop 138 is wider than the flange 162 and may be larger than the passages 164 of the channel 100, thereby enabling the backstop 138 to interface with the rear surface 140 of the adjacent plate 92. In some embodiments, the plates 92 may be coupled to one another via insertion of the rails 98 of one plate 92 into the channels 100 of the adjacent plates in the direction 136. A flexibility of the rails 98 and/or the channels 100 may facilitate this insertion.

FIG. 10 illustrates an embodiment of the end plates 102 of the expandable fairing 90 in the expanded position 104. The first set 94 of plates 92 is extended along a first movement axis 130′, and the second set 96 of plates 92 is extended along a second movement axis 130″. Together, both sets 94, 96 of plates 92 are extended in the expansion direction 170 away from the main tube 58 of the riser 12. In some embodiments, each set of plates 92 may be independently retained in the expanded position 104. Retaining features 172 such as via latches, notches, stops, or detents may retain one or more plates 92 in the expanded position 104. For example, a latch 174 may interface with a pin 176 to retain adjacent plates 92 in the expanded position. A technician extending the one or more plates 92 of the set to the expanded position 104 may manually engage the retaining features 172. In some embodiments, the one or more plates 92 may have auditory and/or visual features that indicate, to a technician extending the plates, when the plates 92 of a set are extended to the expanded position 104.

In some embodiments, the end plates 102 of each set of plates 92 interface at a tip 178. Retaining features 172 such as via latches, fasteners, or mating geometries may couple the end plates 102 together. For example, one or more fasteners 180 may extend at least partially across an interface 182 between the end plates 102. Additionally, or in the alternative, retaining features 172 on an interior surface 184 of the end plates 102 may retain the end plates 102 in the expanded position 104. Moreover, coupling the end plates 102 together at the tip 178 may cooperatively retain the first set 94 of plates 92 and the second set 96 of plates 92 in the expanded position 104. In some embodiments, coupling the end plates 102 together at the tip 178 may enable the omission of retaining features 172 to independently retain other plates 92 of the expandable fairing 90 in the expanded position 104.

It should be appreciated that alternate techniques to extend the plates 92 can be implemented. For example, the plates 92, in place of sliding out to expanded position 104, could rotate outwards, for example, by 180 degrees. The plates 92 would rotate about a rotation point (e.g., a pin or the like) point near the end of the preceding plate. The rotation pin or shaft could have physical limits put on its rotation, for example, via a mechanical or physical hard stop. Accordingly, the first rotation plate would rotate, for example, with the other plates 92 connected to it, 180 degrees or another value and stop. Then the next plate would rotate and so forth until all of the plates 92 have rotated outwards (e.g., each at 180 degrees or another value) creating a similar extension to that illustrated in FIG. 6. Moreover, alternate techniques could be employed to deploy the plates 92.

FIG. 11 illustrates an embodiment of a method (block 202) of assembling the expandable fairing 90. As discussed in detail below, elements of the expandable fairing 90 may be assembled (block 202) prior to or after assembly (block 204) of a riser joint with the riser string. For example, the plates 92 of the expandable fairing 90 are coupled (block 206) together to form a set of plates 92, such as via the rails 98 and channels 100 described above. As discussed above, two or more plates 92 may be coupled together to form a set of plates 92. Two sets of plates 92 of the expandable fairing 90 may be extended to form a tail portion of the expandable fairing 90 with the teardrop shape 84. In some embodiments, one or more backstops 138 are installed (block 208) on rails 98 to facilitate maintenance of the assembled plates 92 together in the collapsed position 105. The one or more sets of plates 92 are coupled (block 210) to the expandable fairing 90. In some embodiments, the one or more sets of plates 92 are coupled (block 210) to the extension of the tail fairing segment 88 of the expandable fairing 90, such as via the rails 98 and channels 100 described above. The one or more sets of plates 92 are collapsed (block 212) into the collapsed position 105, such as into the recess of the tail fairing segment 88 of the expandable fairing 90. As discussed above, the expandable fairing 90 in the collapsed position 105 may have a smaller footprint and may be more stackable than the expandable fairing 90 in the expanded position 104. In some embodiments, the tail fairing segment 88 is coupled (block 214) to other segments (e.g., circular fairing segments 86) of the expandable fairing 90.

FIG. 12 illustrates an embodiment of a method (block 204) of assembling a riser string (e.g., a riser 12) with one or more riser joints having the expandable fairing 90 (e.g., elongated riser joints 40). Segments of the expandable fairing 90 may be installed (block 216) on the riser joint prior to or after the plates 92 of the expandable fairing 90 are assembled (block 202). For example, one or more circular fairing segments 86 and the tail fairing segment 99 without plates 92 may be installed (block 210) on the riser joint, then the sets of plates 92 are coupled (block 210) to the tail fairing segment 88 of the expandable fairing 90. The riser joint with the expandable fairing 90 is coupled (block 218) to the riser string prior to or after the plates 92 of the expandable fairing 90 are assembled (block 202). For example, multiple riser joints of a stand may be coupled to the riser string, and the expandable fairing 90 for each riser joint may be installed (block 216) on each riser joint of the stand when the respective riser joint is at the drill floor 36 or at the moon pool of the offshore vessel. However, it may be appreciated that installation of the expandable fairing 90 (block 216) on the riser joint prior to coupling a stand of riser joints to the riser string may speed the assembly of the riser string with the weathervaning riser joints having the expandable fairing 90.

FIG. 13 illustrates an embodiment of a method (block 205) of utilizing the expandable fairing 90. After the expandable fairing 90 is coupled (block 216) to the riser joint, the one or more sets of plates 92 of the expandable fairing 90 are extended (block 220). In some embodiments, a technician on the drill floor 36 may manually extend the one or more sets of plates 92 from the collapsed position 105 to the expanded position 104. The expanded position 104 of the one or more sets of plates 92 may form the elongated shape (e.g., teardrop shape 84) for the expandable fairing 90. The technician may extend the one or more sets of plates 92 to the expanded position 104 after the expandable fairing 90 on the riser joint has passed through narrow components of the offshore vessel 10, such as the drill floor 36 (or a rotary table therein), diverter housing, or tension ring, among others. Extending the one or more sets of plates 92 (block 220) may include releasing lashes or clasps retaining the one or more sets of plates in the collapsed position 105. In some embodiments, the one or more sets of plates 92 may be locked (block 222) in the expanded position 104. For example, one or more retaining features of each set of plates may be configured to independently retain the respective sets of plates in the expanded position 104. Additionally, or in the alternative, one or more retaining features of the end plates may be configured to collectively retain the sets of plates in the expanded position 104. The one or more sets of plates of the expandable fairing and any retaining features may be manually operable by a technician in a rapid manner to reduce or eliminate any delay in the assembly of the elongated riser joint with the riser string. For example, a technician may manually extend the one or more sets of plates of the expandable fairing from the collapsed position 105 to the expanded position 104 in 300, 250, 100, 60, or 30 seconds or less.

The riser joints with the expandable fairings 90 in the expanded position 104 are inserted (e.g., submerged) (block 224) under the sea surface 28. In some embodiments, the riser joints with the expandable fairings 90 may be approximately 5 to 50, 10 to 40, 15 to 25, or 20 percent of the length of the riser string between the offshore vessel 10 and the seafloor 14. For example, the riser joints with the expandable fairing 90 may be assembled to form a majority of the riser joints in the third of the riser string nearest to the sea surface 28. As discussed above, the expandable fairings 90 in the expanded position 104 may rotate in the circumferential direction 46 around the main tube 58 of the riser string. The tail fairing segment 88 of the expandable fairing 90 may weathervane (block 226) to generally align with a direction of the current 20 across the riser string at the expandable fairing 90. The elongated shape (e.g., teardrop shape 84) of the expandable fairing 90 may reduce forces (e.g., drag) on the riser string from the current 20, thereby enabling the angle 32 between the vertical axis 26 and the top flex joint 34 beneath the drill floor 36 of the offshore vessel 10 to be maintained below a desired surface threshold angle, and enabling the angle 24 between the vertical axis 26 and the bottom flex joint 30 to be maintained below a desired subsea angle.

After a time under the sea surface 28, riser joints with the expandable fairing 90 may be raised (block 228). The expandable fairing 90 is collapsed (block 212) from the expanded position 104 to the collapsed position 105 after the riser joint is raised to the offshore vessel 10. A technician may lash or clasp the one or more plates 92 of the expandable fairing 90 to retain the one or more plates 92 in the collapsed position 105 for movement and/or storage of the expandable fairing 90. In some embodiments, the riser joint is removed (block 232) from the riser string prior to collapsing (block 212) the expandable fairing 90. In some embodiments, the expandable fairing 90 is collapsed (block 212) and removed from the riser joint prior to removal (block 232) of the riser joint from the riser string. The expandable fairing 90 in the collapsed position 105 may be stored (block 234) separate from or with the riser joint. It is appreciated that the expandable fairing 90 in the collapsed position 105 has a smaller footprint than the expandable fairing 90 in the expanded position 104.

It is also appreciated that FIGS. 11-13 illustrate embodiments of methods for assembling and utilizing the expandable fairing 90 described above with riser joints of a riser string. While the methods described in blocks 202, 204, and 205 are illustrated and described separately, it may be appreciated that many of the steps of the method may be performed at different times and in different orders. For example, the expandable fairing 90 may be assembled (block 202) and transported to the offshore vessel 10 separate from the riser joint that later is coupled (block 216) to the expandable fairing 90. On the offshore vessel 10, the expandable fairing 90 may be coupled (block 216) to the riser joint before or after the riser joint is coupled (block 218) to the riser string. Additionally, or in the alternative, the plates 92 of the expandable fairing 90 may be extended to the expanded position 104 before or after the riser joint is coupled (block 218) to the riser string. It may be appreciated that some steps of the methods described in blocks 202, 204, and 205 may be omitted or reordered.

As previously discussed, the expandable fairing 90 may expand to have an elongated shape, such as the teardrop shape 84. However, other types of expandable fairings may alternatively be utilized to expand to have an elongated shape, such as the teardrop shape 84. For example, FIG. 14 illustrates a perspective view of second embodiment of an expandable fairing 236 that may form a portion of the elongated riser joint 40 of the riser 12 (e.g., as the fairing segment 82 of the elongated riser joint 40). The expandable fairing 236 may be an embodiment of a buoyancy assembly 74 that is neutrally buoyant, or that is buoyant, as will be discussed in greater detail below. In some embodiments, the expandable fairing 236 may have the teardrop shape 84, where the tail fairing segment 88 of the teardrop shape 84 is formed by inflating a bladder 238. Use of the bladder 238 allows for the expandable fairing 236 to be expanded or collapsed. The expandable fairing 236, as illustrated in FIG. 14, is in an expanded position in which the expandable fairing may have a length 52 to width 87 ratio between approximately 1:1.5 to 1:3, whereas the expandable fairing 236 in a collapsed position (as illustrated in FIG. 15) may have a length 52 to width 89 ratio between approximately 1:1 to 1:1.5.

The expandable fairing 236 may have one or more fairing segments 82 that at least partially enclose the main tube 58 of the elongated riser joint 40 in the circumferential direction 46. For example, the expandable fairing 236 may have a body 106 that at least partially encloses the main tube 58, as previously discussed in conjunction with FIGS. 6 and 7. As previously discussed, an axial gap 108 of the body 106 may facilitate installation of the body 106 around the main tube 58 of the riser 12 and/or may facilitate the routing of one or more hoses or cables (e.g., mux cables, a hot line hose, etc.) along the main tube 58. In some embodiments, the bladder 238 may include an aperture disposed adjacent to the axial gap 108, whereby the aperture runs the length of the bladder 238 along length 52. This aperture may further allow for the placement and/or the routing of the one or more hoses or cables along the main tube 58. Furthermore, as previously discussed, the body 106 can include two fairing segments 82 coupled at location 110, such as via a hinge, to allow the expandable fairing 236 to be attached to and removed from the elongated riser joint 40.

Thus, as illustrated in FIGS. 14 and 15, the expandable fairing 236 includes the body 106 and the bladder 238. The bladder 238 can be a separate component relative to the body 106, such that the bladder 238 may be partially separable and/or fully separable from the body. For example, the bladder 238 may be coupled to the body 106 via a strap or other affixing means that couples the bladder 238 to the body 106. Additionally and/or alternatively, the bladder 238 and body 106 may be coupled connection via an appendage and slot connection that may include a locking mechanism as well as a release. For example, one or more an appendages may extend from the bladder 238 and may fit into a slot in the body 106. The bladder 238 may be moved along length 52 and into a locked position in which a locking mechanism secures the appendage from movement in the slot. A release (e.g., a button or similar mechanism) may be actuated to release the locking mechanism to allow for the bladder 238 to be moved relative to the body 106. It should be appreciated that alternative devices may be employed to removably affix the bladder 238 to the body 106.

In other embodiments, in place of or in addition to the bladder 238 being completely removable/detachable from the body 106, a hinge or other mechanism may be utilized in conjunction with a releasable locking mechanism to allow for partial detachment of the bladder 238 from the body 106. For example, a hinge or other connector that allows for movement of the bladder 238 with respect to the body may be disposed on the side 240 of the bladder 238 to movably connect the bladder 238 to the body 106. A release (e.g., a button or similar mechanism) may be actuated to release a locking mechanism that is disposed on the side of the bladder 238 opposite to side 240. This may allow the bladder 238 to partially swing away from the body 106, for example, to allow for the ease of placement and/or the routing of the one or more hoses or cables (e.g., mux cables, a hot line hose, etc.) along the main tube 58. The bladder 238 may be reconnected to the body 106 by repositioning the bladder 238 adjacent to the body 106 to actuate the locking mechanism that is disposed on the side of the bladder 238 opposite to side 240. It is envisioned that during normal operations, the bladder 238 is be fully attached to the body 106 and while techniques and components to attach the bladder 238 to the body 106 are described above, the bladder 238 may attach to the body 106 using various methods and components.

The bladder 238 may be made of a flexible material, such that the bladder 238 may be inflatable to expand into an expanded position (illustrated in FIG. 14), as well as deflatable to collapse into a collapsed position (illustrated in FIG. 15). The flexible material of the bladder 238 may be, for example, a synthetic material (e.g., a polymer) and may be selected as having adequate strength and elastic properties, along with any other synthetic reinforcement material. The bladder 238 may include an outer protective layer, which may be fabricated with the bladder 238 or as a separate component and attached thereto. As illustrated, the bladder 238 includes a coupling 242 that operates in conjunction with a constraint element (e.g., a valve) to allow for fluids to be transmitted into and retained in the bladder 238, as well as removed from the bladder 238. This transmission and removal of fluids into and from the bladder 238 may be accomplished via use of a pump or similar device coupled to the coupling 242. Choices in fluids used to inflate the bladder may be based, for example, on desired buoyancy characteristics of the expanded bladder 238. For example, water may be used as the fluid to expand the bladder 238 when neutral buoyancy is desired. Likewise air or another gas may be utilized as the fluid to expand the bladder 238 when positive buoyancy is desired.

Additionally, the bladder 238 as illustrated includes a fluid release mechanism 244. The fluid release mechanism may be, for example, an over pressure relief valve that automatically vents the bladder 238 if a pressure within the bladder 238 exceeds a threshold amount. The automatic venting of the fluid may be accomplished by the pressure in the bladder causing movement of the fluid release mechanism 244 away from the bladder 238, thus venting some of the fluid and reducing the pressure of the remaining fluid in the bladder 238. The fluid release mechanism may also reset itself once the bladder pressure drops below the threshold amount.

When the expandable fairing 236 is pressurized and/or otherwise fully inflated to the expanded positon in FIG. 14, the riser/fairing assembly footprint increases, This creates a nearly rigid-like airfoil (e.g., teardrop shape 84). When the bladder 238 is depressurized and collapsed (e.g., into the collapsed position illustrated in FIG. 15), the footprint of the riser 12 in conjunction with the expandable fairing 236 is reduced significantly. The expansion and collapse of the bladder 238 are described in greater detail below.

FIG. 16 illustrates an embodiment of a method (block 246) of assembling a riser string (e.g., a riser 12) with one or more riser joints having the expandable fairing 236 (e.g., elongated riser joints 40). Segments of the expandable fairing 236 may be installed on the riser joint. The riser joint with the expandable fairing 236 is coupled (block 250) to the riser. For example, multiple riser joints of a stand may be coupled to the riser string, and the expandable fairing 236 for each riser joint may be installed (block 248) on each riser joint of the stand when the respective riser joint is at the drill floor 36 or at the moon pool of the offshore vessel. However, it may be appreciated that installation of the expandable fairing 236 (block 248) on the riser joint prior to coupling a stand of riser joints to the riser string may speed the assembly of the riser string with the weathervaning riser joints having the expandable fairing 236. Furthermore, the expandable fairing 236 may be installed (block 248) in the collapsed position 105 because the expandable fairing 236 in the collapsed position 105 has a smaller footprint than the expandable fairing 236 in the expanded position 104.

Installation of the expandable fairing 236 (block 248) can include coupling the body 106 of the expandable fairing 236 to the riser joint. For example, as previously discussed, the body 106 can include two fairing segments 82 coupled at location 110, such as via a hinge, to allow the expandable fairing 236 (i.e., the body 106) to be attached to riser joint (e.g., the elongated riser joint 40). Additionally, an axial gap 108 of the body 106 may facilitate the routing of one or more hoses or cables (e.g., mux cables, a hot line hose, etc.) along the main tube 58, which may be undertaken when installing the expandable fairing 236 on the riser joint (block 248) when coupling the riser joint to the riser string (block 250) or at a time thereafter (e.g., in conjunction with inflation of the bladder 238). Furthermore, as previously noted, the bladder 238 can be a separate component relative to the body 106, such that the bladder 238 may be partially separable and/or fully separable from the body. For example, the bladder 238 may be coupled to the body 106 via a strap or other affixing means that couples the bladder 238 to the body 106. Additionally and/or alternatively, the bladder 238 and body 106 may be coupled connection via an appendage and slot connection that may include a locking mechanism as well as a release. For example, one or more appendages may extend from the bladder 238 and may fit into a slot in the body 106. The bladder 238 may be moved along length 52 and into a locked position in which a locking mechanism secures the appendage from movement in the slot. A release (e.g., a button or similar mechanism) may be actuated to release the locking mechanism to allow for the bladder 238 to be moved relative to the body 106. It should be appreciated that alternative devices may be employed to removably affix the bladder 238 to the body 106 and affixing the bladder 238 to the body can be undertaken during installation of the expandable fairing 236 (block 248)

FIG. 17 illustrates an embodiment of a method (block 252) of utilizing the expandable fairing 236. In some embodiments, a technician may inflate (block 254) the bladder 238 from the collapsed position 105 to the expanded position 104. Alternatively, this inflation (block 254) may be automatically accomplished via, for example, a pump internal to the bladder 238. The expanded position 104 may form the elongated shape (e.g., teardrop shape 84) for the expandable fairing 236. Inflation of the bladder 238 (block 254) may occur after the expandable fairing 236 on the riser joint has passed through narrow components of the offshore vessel 10, such as the drill floor 36 (or a rotary table therein), diverter housing, or tension ring, among others. Inflating the bladder 238 may include releasing lashes or clasps retaining the bladder 238 in the collapsed position 105. In some embodiments, bladder 238 may be locked in the expanded position 104. Inflation of the expandable fairing from the collapsed position 105 to the expanded position 104 in 300, 250, 100, 60, or 30 seconds or less.

In some embodiments, the inflation of the bladder 238 (block 254) involves coupling a pump (external to the expandable fairing 236) to the coupling 242 that operates in conjunction with a constraint element (e.g., a valve) to allow for fluids to be transmitted into and retained in the bladder 238, as well as removed from the bladder 238, although, as previously, noted, a pump internal to the bladder 238 may instead be utilized. Choices in fluids used to inflate the bladder may be based, for example, on desired buoyancy characteristics of the expanded bladder 238 and/or other requirements (e.g., cost, rate of inflation/deflation, etc.).

Moreover, in conjunction with the inflation of the bladder (block 254), i.e., either during, before, or after inflation, installation and/or routing of one or more hoses or cables (e.g., mux cables, a hot line hose, etc.) may be undertaken. For example, an aperture that runs the length of the bladder 238 along length 52 may allow for the placement and/or the routing of the one or more hoses or cables. In other embodiments, in place of or in addition to the bladder 238 being completely removable/detachable from the body 106, a hinge or other mechanism may be utilized in conjunction with a releasable locking mechanism to allow for partial detachment of the bladder 238 from the body 106 for example, to allow for the placement and/or the routing of the one or more hoses or cables along the main tube 58. For example, a release (e.g., a button or similar mechanism) may be actuated to release a locking mechanism that is disposed on the side of the bladder 238 opposite to side 240 to allow the bladder 238 to partially swing away from the body 106, for example, to allow for the ease of placement and/or the routing of the one or more hoses or cables along the main tube 58. The bladder 238 may be reconnected to the body 106 by repositioning the bladder 238 adjacent to the body 106 to actuate the locking mechanism that is disposed on the side of the bladder 238 opposite to side 240 in conjunction with, prior to, or subsequent to inflation of the bladder 238 (block 254).

The riser joints with the expandable fairings 236 in the expanded position 104 are inserted (e.g., submerged) (block 256) under the sea surface 28. In some embodiments, the riser joints with the expandable fairings 236 may be approximately 5 to 50, 10 to 40, 15 to 25, or 20 percent of the length of the riser string between the offshore vessel 10 and the seafloor 14. For example, the riser joints with the expandable fairing 236 may be assembled to form a majority of the riser joints in the third of the riser string nearest to the sea surface 28. As discussed above, the expandable fairings 236 in the expanded position 104 may rotate in the circumferential direction 46 around the main tube 58 of the riser string. The tail fairing segment 88 of the expandable fairing 236 may weathervane (block 258) to generally align with a direction of the current 20 across the riser string at the expandable fairing 236. The elongated shape (e.g., teardrop shape 84) of the expandable fairing 236 may reduce forces (e.g., drag) on the riser string from the current 20, thereby enabling the angle 32 between the vertical axis 26 and the top flex joint 34 beneath the drill floor 36 of the offshore vessel 10 to be maintained below a desired surface threshold angle, and enabling the angle 24 between the vertical axis 26 and the bottom flex joint 30 to be maintained below a desired subsea angle.

After a time under the sea surface 28, riser joints with the expandable fairing 236 may be raised (block 260). The expandable fairing 236 is deflated (block 262) from the expanded position 104 to the collapsed position 105 after the riser joint is raised to the offshore vessel 10 either automatically or via a user in a manner opposite to that described above with respect to the inflation of the bladder 238 (block 254). Likewise, the one or more hoses or cables (e.g., mux cables, a hot line hose, etc.) may be removed from along the main tube 58 in a manner opposite to the routing procedure described above. The expandable fairing 236 may be strapped, locked, or otherwise restrained to insure that the bladder 238 remains deflated and the expandable fairing 236 remains in the collapsed position 105 for movement and/or storage of the expandable fairing 236. In some embodiments, the riser joint is removed (block 264) from the riser string prior to collapsing (i.e., deflating) the expandable fairing 236. In some embodiments, the expandable fairing 236 is deflated (block 262) and removed from the riser joint prior to removal (block 264) of the riser joint from the riser string. Alternatively, the expandable fairing 236 can be deflated into the collapsed position 105 and stored in conjunction with the riser joint once the riser joint is removed (block 264) from the riser string. In this manner, the expandable fairing 236 in the collapsed position 105 may be stored (block 266) separate from or with (i.e., coupled to) the riser joint. It is appreciated that the expandable fairing 236 in the collapsed position 105 has a smaller footprint than the expandable fairing 236 in the expanded position 104.

It is also appreciated that FIGS. 16 and 17 illustrate embodiments of methods for assembling and utilizing the expandable fairing 236 described above with riser joints of a riser string. While the methods in blocks 246 and 252 are illustrated and described separately, it may be appreciated that many of the steps of the method may be performed at different times and in different orders. For example, the expandable fairing 236 may be assembled and transported to the offshore vessel 10 separate from the riser joint to which it is later is coupled (block 248). On the offshore vessel 10, the expandable fairing 236 may be coupled (block 248) to the riser joint before or after the riser joint is coupled (block 234) to the riser string. Additionally, or in the alternative, the bladder 238 of the expandable fairing 236 may be extended to the expanded position 104 before or after the riser joint is coupled (block 234) to the riser string. It may be appreciated that some steps of the methods of blocks 246 and 252 may be omitted or reordered and that in some embodiments, the expandable fairing 236 is collapsed and stored with (i.e., coupled to) a riser joint.

This written description uses examples to disclose the above description, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Additionally, the usage herein of the term approximately with given values includes values within 10 percent of the given values. Accordingly, while the above disclosed embodiments may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the embodiments are not intended to be limited to the particular forms disclosed. Rather, the disclosed embodiment are to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the embodiments as defined by the following appended claims.

	Number	Date	Country
Parent	16661814	Oct 2019	US
Child	16661833		US

EXPANDABLE FAIRING OF WEATHERVANING RISER JOINT

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CPC

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Abstract

Description

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CROSS REFERENCE TO RELATED APPLICATIONS

Provisional Applications (1)

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