Systems configured to moor a floating structure to a seabed and processes for using same

Abstract

Systems for mooring a floating structure to a seabed and processes for using same. The system can include a hybrid tether that includes a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement. The system can also include a first connector configured to connect a first end of the hybrid tether to an anchor secured to the seabed and a second connector configured to connect a second end of the hybrid tether to the floating structure. An axial stiffness of the stiff member can be greater than an axial stiffness of the compliant member. The first and second connectors can be configured to allow the first and second ends of the hybrid tether to pivot relative to the anchor and the floating structure. The hybrid tether can be substantially vertical when connected to the anchor and the floating structure.

Description

SYSTEMS CONFIGURED TO MOOR A FLOATING STRUCTURE TO A SEABED AND PROCESSES FOR USING SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 654,129, filed on May 31 , 2024, which is incorporated by reference herein.FIELD

[0002] Embodiments described generally relate to systems configured to moor a floating structure to a seabed and processes for using same. More particularly, such embodiments relate to systems that include one or more hybrid tethers configured to moor a floating structure to the seabed at an offshore location, e.g., at an offshore wind farm or drilling site.BACKGROUND

[0003] In the offshore renewable industry, e.g., the offshore floating wind industry, it is often necessary or desirable to moor a platform with a vertically arranged mooring system. Vertically arranged mooring systems generally have a smaller footprint than traditional spread mooring systems. Certain platform configurations, such as the Tension Leg Platform (TLP), are available and have been used in oil and gas applications. Such systems typically utilize vertically arranged tubular steel tendons as the mooring system to moor the platform to the seabed. Such systems are expensive and can be difficult to install.

[0004] There is a need, therefore, for improved systems configured to moor a floating structure to a seabed and processes for using same.SUMMARY

[0005] Systems configured to moor a floating structure to a seabed and processes for using same are provided. In some embodiments, the system can include a hybrid tether that can include a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement. The system can also include a first connector configured to connect a first end of the hybrid tether to an anchor secured to the seabed. The system can also include a second connector configured to connect a second end of the hybrid tether to the floating structure. The stiff elongated member can be formed from a metal or a metal alloy. The compliant elongated member can be formed from a synthetic polymer. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The first connector can be configured to allow the first end of the hybrid tether to pivot relative to the anchor. The second connector can be configured toallow the second end of the hybrid tether to pivot relative to the floating structure. The hybrid tether can be configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure.

[0006] In other embodiments, the system can include a hybrid tether that can include a stiff elongated member having a first end and a second end and a compliant elongated member having a first end and a second end. The system can also include a first connector and second connector. The first end of the stiff elongated member can be configured to be pivotally connected to an anchor secured to the seabed via the first connector. The second end of the stiff elongated member and the first end of the compliant elongated member can be configured to be connected to one another. The second end of the compliant elongated member can be configured to be pivotally connected to the floating structure via the second connector. The stiff elongated member can be formed from a metal or a metal alloy. The compliant elongated member can be formed from a synthetic polymer. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The hybrid tether can be configured to be substantially vertical when the first end of the stiff elongated member is connected to the anchor and the second end of the compliant elongated member is connected to the floating structure.

[0007] In other embodiments, the system can include a hybrid tether that can include a stiff elongated member having a first end and a second end and a compliant elongated member having a first end and a second end. The system can also include a first connector and a second connector. The first end of the compliant elongated member can be configured to be pivotally connected to an anchor secured to the seabed via the first connector. The second end of the compliant elongated member and the first end of the stiff elongated member can be configured to be connected to one another. The second end of the stiff elongated member can be configured to be pivotally connected to the floating structure via the second connector. The stiff elongated member can be formed from a metal or a metal alloy. The compliant elongated member can be formed from a synthetic polymer. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The hybrid tether can be configured to be substantially vertical when the first end of the compliant elongated member is connected to the anchor and the second end of the stiff elongated member is connected to the floating structure.

[0008] In some embodiments, a tension leg platform system can include a structure, an anchor, a hybrid tether, a first connector, and a second connector. The structure can be configured to float on a surface of a body of water. The anchor ca be configured to be secured to a seabed of the body of water. The hybrid tether can include a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement. The first connector can be configured to pivotally connect a first end of the hybrid tether to the anchor. The second connector can be configured to pivotally connect a second end of the hybrid tether to the floating structure. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The hybrid tether can be configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure.

[0009] In some embodiments, a process for installing a tension leg platform can include providing a tension leg platform system. The tension leg platform system can include a structure, an anchor, a hybrid tether, a first connector, and a second connector. The structure can be configured to float on a surface of a body of water. The anchor can be configured to be secured to a seabed of the body of water. The hybrid tether can include a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement. The first connector can be configured to pivotally connect a first end of the hybrid tether to the anchor. The second connector can be configured to pivotally connect a second end of the hybrid tether to the floating structure. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The hybrid tether can be configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure. The process can also include disposing the anchor on the seabed. The process can also include positioning the structure on the surface of the body of water. The process can also include connecting the stiff elongated member and the compliant elongated member to one another. The process can also include connecting the first end of the hybrid tether to the anchor. The process can also include connecting the second end of the hybrid tether to the tension leg platform.

[0010] In some embodiments, a system configured to moor a floating structure to a seabed can include a hybrid tether that can include a stiff elongated member and a compliant elongated member that can be configured to be connected to one another in a series arrangement, a first connector that can be configured to connect a first end of the hybrid tether to an anchor securedto the seabed, and a second connector that can be configured to connect a second end of the hybrid tether to the floating structure. The stiff elongated member can be formed from ultra- high-molecular-weight polyethylene. The compliant elongated member can be formed from polyester, nylon, or a combination thereof. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The first connector can be configured to allow the first end of the hybrid tether to pivot relative to the anchor. The second connector can be configured to allow the second end of the hybrid tether to pivot relative to the floating structure. The hybrid tether can be configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure.

[0011] In some embodiments, a system configured to moor a floating structure to a seabed can include a hybrid tether that can include a stiff elongated member having a first end and a second end and a compliant elongated member having a first end and a second end, a first connector, and a second connector. The first end of the stiff elongated member can be configured to be pivotally connected to an anchor secured to the seabed via the first connector. The second end of the stiff elongated member and the first end of the compliant elongated member can be configured to be connected to one another. The second end of the compliant elongated member can be configured to be pivotally connected to the floating structure via the second connector. The stiff elongated member can be formed from ultra-high-molecular-weight polyethylene. The compliant elongated member can be formed from polyester, nylon, or a combination thereof. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The hybrid tether can be configured to be substantially vertical when the first end of the stiff elongated member is connected to the anchor and the second end of the compliant elongated member is connected to the floating structure.

[0012] In some embodiments, a system configured to moor a floating structure to a seabed can include a hybrid tether that can include a stiff elongated member having a first end and a second end and a compliant elongated member having a first end and a second end, a first connector, and a second connector. The first end of the compliant elongated member can be configured to be pivotally connected to an anchor secured to the seabed via the first connector. The second end of the compliant elongated member and the first end of the stiff elongated member can be configured to be connected to one another. The second end of the stiff elongated member can be configured to be pivotally connected to the floating structure via the second connector. The stiff elongated member can be formed from ultra-high-molecular-weight polyethylene. Thecompliant elongated member can be formed from polyester, nylon, or a combination thereof. An axial stiffness of the stiff elongated member can be greater than an axial stiffness of the compliant elongated member. The hybrid tether can be configured to be substantially vertical when the first end of the compliant elongated member is connected to the anchor and the second end of the stiff elongated member is connected to the floating structure.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The various aspects and advantages of the preferred embodiment of the present invention will become apparent to those skilled in the art upon an understanding of the following detailed description of the invention, read in light of the accompanying drawings which are made a part of this specification.

[0014] Figure 1 depicts an illustrative system configured to moor a floating structure to a seabed that includes a hybrid tether, a first connector, and a second connector, according to one or more embodiments described.

[0015] Figure 2 depicts an isometric view of another illustrative system configured to moor a floating structure to a seabed that includes a hybrid tether, a first connector, and a second connector, according to one or more embodiments described.

[0016] Figure 3 depicts a close-up side view of the system shown in Figure 2.

[0017] Figure 4 depicts an elevation view of an illustrative system having a first configuration configured to moor a floating structure to a seabed, according to one or more embodiments described.

[0018] Figure 5 depicts an elevation view of an illustrative system having a second configuration configured to moor a floating structure to a seabed, according to or more embodiments described.

[0019] Figure 6 depicts an isometric view of a tension leg platform system that includes a triangular hull structure, an anchor, and a plurality of hybrid tethers, according to one or more embodiments described.DETAILED DESCRIPTION

[0020] A detailed description will now be provided. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references to the “invention”, in some cases, refer to certain specific or preferred embodiments only. In other cases, references to the “invention” refer to subject matter recited in one or more, but not necessarily all, of the claims. It is to be understood that the following disclosuredescribes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and / or letters in the various exemplary embodiments and across the figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and / or configurations discussed in the Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows includes embodiments in which the first and second features are formed in direct contact and also includes embodiments in which additional features are formed interposing the first and second features, such that the first and second features are not in direct contact. The exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure. The figures are not necessarily drawn to scale and certain features and certain views of the figures can be shown exaggerated in scale or in schematic for clarity and / or conciseness.

[0021] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Also, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Furthermore, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.”

[0022] All numerical values in this disclosure are exact or approximate values (“about”) unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope.

[0023] Further, the term “or” is intended to encompass both exclusive and inclusive cases, i.e., “A or B” is intended to be synonymous with “at least one of A and B,” unless otherwise expressly specified herein. The indefinite articles “a” and “an” refer to both singular forms (i.e., “one”) and plural referents (i.e., one or more) unless the context clearly dictates otherwise.The terms “up” and “down”; “upward” and “downward”; “upper” and “lower”; “upwardly” and “downwardly”; “above” and “below”; and other like terms used herein refer to relative positions to one another and are not intended to denote a particular spatial orientation since the apparatus and processes for using the same may be equally effective at various angles or orientations.

[0024] The term “substantially vertical”, when referring to a hybrid tether such as hybrid tethers 110 and 210 described below, means the hybrid tether can be oriented within 0.5 degrees, 1 degree, 3 degrees, 5 degrees, 7 degrees, 9 degrees, 11 degrees, 13 degrees, 15 degrees, 17 degrees, or 20 degrees of an axis that is vertical with respect the earth. In some embodiments, when one or more of the hybrid tethers is substantially vertical, the hybrid tether can be oriented within < 20 degrees, < 18 degrees, < 16 degrees, < 14 degrees, < 12 degrees, < 10 degrees, < 8 degrees, < 6 degrees, < 4 degrees, or < 2 degrees of the axis that is vertical with respect to the earth.

[0025] Figure 1 depicts an illustrative system 100 configured to moor a floating structure to a seabed that includes a hybrid tether 110, a first connector 140, and a second connector 150, according to one or more embodiments. The hybrid tether 110 can include a stiff elongated member 120 and a compliant elongated member 130 configured to be connected to one another in a series arrangement. The first connector 140 can be configured to connect a first end 111 of the hybrid tether 110 to an anchor disposed on or otherwise secured to the seabed. The second connector 150 can be configured to connect a second end 112 of the hybrid tether 110 to the floating structure.

[0026] In some embodiments, a first end 121 of the stiff elongated member 120 can be the first end of the 111 of the hybrid tether 110, as shown in Figure 1. A second end 122 of the stiff elongated member 120 can be connected to a first end 131 of the compliant elongated member 130. In some embodiments, a second end 132 of the compliant elongated member 130 can be the second end 112 of the hybrid tether 110, as shown in Figure 1. It should be understood that the hybrid tether 110 can be oriented in the opposite direction with respect to the orientation shown in Figure 1 such that the second end 132 of the compliant elongated member 130 can be configured to connect to the first connector 140 and the first end 121 of the stiff elongated member 120 can be configured to connect to the second connector 150. In such embodiments, the second end 132 of the compliant member 130 can be the first end 111 of the hybrid tether 110 and the first end 121 of the stiff elongated member 120 can be the second end 112 of the hybrid tether 110.

[0027] In some embodiments, the stiff elongated member 120 can have a greater length than the compliant elongated member 230. In other embodiments, the compliant elongated member 120 can have a greater length than the stiff elongated member 120. In still other embodiments, the stiff elongated member 120 and the compliant elongated member 130 can have the same or about the same length with respect to one another.

[0028] In some embodiments, the stiff elongated member 120 can be formed from a metal, a metal alloy, carbon fiber, or a combination thereof. Suitable metals and metal alloys can be or can include, but are not limited to steel, carbon steel, steel alloys, stainless steel, stainless steel alloys, aluminum, aluminum alloys, nickel, nickel based alloys, bronze, brass, non-ferrous metals, non-ferrous metal alloys, or combinations thereof. In some embodiments, the stiff elongated member 120 can be in the form of a hollow bar, a solid bar, a chain, or a combination thereof. In some embodiments, when the stiff elongated member 120 is in the form of a hollow bar or solid bar, the bar can have any desired cross-sectional shape. For example, the cross- sectional shape of the bar can be triangular, rectangular, pentagonal, hexagonal, any other polygonal shape, elliptical, e.g., circular, or any combination of shapes along the length of the stiff elongated member 120. In some embodiments, the stiff elongated member can be in the form of a pipe, a solid rod, or a combination thereof. In still other embodiments, the stiff elongated member can be in the form of a carbon fiber cable, wire, rod, or the other carbon fiber structure.

[0029] In some embodiments, the compliant elongated member 130 can be formed from a synthetic polymer. In some embodiments, the compliant elongated member 130 can be in the form of a rope. In some embodiments, the synthetic polymer can be or can include, but is not limited to, polyester, nylon, ultra-high-molecular-weight polyethylene (UHMWPE), or any combination thereof. In some embodiments, the compliant elongated member 130 can include one or more segments of synthetic polymer rope, such as DEEPROPE® polyester rope available from Bexco, or MOORLINE® polyester rope available from Bridon, or CABRAL 512® polyester rope available from Lankhorst, or DYNEEMA® UHMWPE fiber rope, e.g., DM20 fiber rope, available from DSM, or any other synthetic rope that has similar properties.

[0030] In still other embodiments, the stiff elongated member 120 can be formed from ultra- high-molecular- weight polyethylene (UHMWPE) and the compliant elongated member 130 can be formed from polyester, nylon, or a combination thereof. As such, in some embodiments, the stiff elongated member 120 can include or more segments of synthetic polymer rope, such as DYNEEMA® UHMWPE fiber rope available from DSM, and the compliant elongatedmember can include one or more segments of synthetic polymer rope, such as DEEPROPE® polyester rope available from Bexco, or MOORLINE® polyester rope available from Bridon, or CABRAL 512® polyester rope available from Lankhorst.

[0031] The stiff elongated member 120 can have an axial stiffness that can be greater than an axial stiffness of the compliant elongated member 130. The axial stiffness of the stiff elongated member 120 and the compliant elongated member 130 can be determined via the equation: k = AE / L, where A is the cross-sectional area of the stiff elongated member 120 or the compliant elongated member 130, E is the elastic modulus of the stiff elongated member 120 or the compliant elongated member 130, and L is the length of the stiff elongated member 120 or the compliant elongated member 130. In some embodiments, a ratio of the axial stiffness of the stiff elongated member 120 to the axial stiffness of the compliant elongated member 130 can be in a range from about 2:1, about 2.5:1, about 3: 1, about 3.5:1, about 4:1, or about 6:1 to about 8:1, about 10:1, about 13:1, about 15: 1, about 20:1, about 25:1, about 30:1, about 35:1, about 40:1, about 45:1, or about 50:1.

[0032] The first connector 140 can include a first part 141 that can be configured to be attached to, connected to, secured to, or otherwise disposed on the hybrid tether 110 at or toward the first end 111 thereof and a second part 142 that can be configured to be attached to, connected to, secured to, or otherwise disposed on the anchor. The first part 141 of the first connector 140 and the second part 142 of the first connector 140 can be or can be configured to connect to one another. As such, in some embodiments, during connection of the hybrid tether 110 to the anchor via the first connector 140, the first part 141 can be connected to the hybrid tether 110, the second part 142 can be secured to the anchor, and the first part 141 and the second part 142 can be connected to one another to connect the first end 111 of the hybrid tether 110 to the anchor.

[0033] The second connector 150 can include a first part 151 that can be configured to be attached to, connected to, secured to, or otherwise disposed on the hybrid tether 110 at or toward the second end 112 thereof and a second part 152 that can be configured to be attached to, connected to, secured to, or otherwise disposed on the floating structure. The first part 151 of the second connector 150 and the second part 152 of the second connector 150 can be or can be configured to connect to one another. As such, in some embodiments, during connection of the hybrid tether 110 to the floating structure via the second connector 150, the first part 151 can be connected to the hybrid tether 110, the second part 152 can be secured to the floatingstructure, and the first part 151 and the second part 152 can be connected to one another to connect the second end 112 of the hybrid tether 110 to the floating structure.

[0034] The first connector 140 can be configured to allow the first end 111 of the hybrid tether 110 to pivot relative to the anchor. The second connector 150 can be configured to allow the second end 112 of the hybrid tether 110 to pivot relative to the floating structure. In some embodiments the first connector 140 and / or the second connector 150 can independently be configured to provide or otherwise allow the first end 111 and the second end 112, respectively, of the hybrid tether 110 to pivot about one, two, or three axes of rotation with respect to the anchor and the floating structure, respectively. In some embodiments, the first connector 140 and the second connector 150 can be the same type of connector or different types of connectors.

[0035] In some embodiments, the second end 122 of the stiff elongated member 120 can be connected to the first end 131 of the compliant elongated member 130 via a third connector 160. In some embodiments, the third connector 160 can permit the stiff elongated member 120 and the compliant elongated member 130 to pivot with respect to one another. In some embodiments, the first, second, and third connectors 140, 150, 160, respectively, can be or can include, but are not limited to, an H-link connector, a twisted H-link connector, a dual axis joint, a pad-eye connector, a clevis connector, a plate link connector, a length adjustment connector, a segment of wire rope, a segment of chain, or any combination thereof. In some embodiments, the first connector 140 and / or the second connector 150 can be or can include a ball and socket connector. In some embodiments, the second connector 150 can be or can include a swivel connector. In some embodiments, the compliant elongated member 130 can have a first end 131 and a second end 132. In some embodiments, the first end 131 and / or the second end 132 of the compliant elongated member 130 can have or configured to terminate in an eye splice to facilitate the connection of the compliant elongated member to another member. In some embodiments, the first end 131 and / or the second end 132 can each include a thimble within the eye splice.

[0036] In some embodiments, the first, second, and third connectors 140, 150, 160 can be fabricated or otherwise made from any suitable material or combination of materials. In some embodiments, one or more of the components of the first, second, and third connectors 140, 150, 160 can be made via any suitable manufacturing process such as forging, casting, molding, milling, machining, or other process. In some embodiments, suitable materials can be or can include, but are not limited to, metal, metal alloys, non-metallic materials, or any other materialthat is appropriate for the loading, service, and environment that the first, second, and third connectors 140, 150, 160 may be subjected to during use thereof. Suitable metals and metal alloys can be or can include, but are not limited to, steel, carbon steel, stainless steel, aluminum, nickel, bronze, brass, titanium, or any combination thereof.

[0037] In some embodiments, the first, second and third connectors 140, 150, 160 can be a dual axis joint connector. Illustrative dual axis joint connectors can include those described in U.S. Patent Application Publication No. 2023 / 0151846. In some embodiments, the first, second, and / or third connectors 130, 140, 150, respectively, can be the length adjustment connector described in WO Publication No. 2022 / 050935. In some embodiments, a suitable length adjustment connector can be or can include a segment of wire rope or chain of which a length of the wire rope or chain can be adjusted. For example, if the length adjustment connector includes a segment of chain, the length of the hybrid tether 110 can be adjusted by changing the particular link of the chain to which the hybrid tether can be connected to the anchor, the floating structure, and / or the stiff elongated member 120 and the compliant elongated member 130 can be connected to one another. Illustrative ball and socket connectors can include the ball and socket connectors described in U.S. Patent Application Publication No. 2024 / 0011524.

[0038] Figure 2 depicts an isometric view of another illustrative system 200 configured to moor a floating structure to a seabed that includes a hybrid tether 210, a first connector 240, and a second connector 250, according to one or more embodiments. Figure 3 depicts a closeup side view of the system 200 shown in Figure 2. Continuing with reference to Figures 2 and 3, the hybrid tether 210 can include a stiff elongated member 220 and a compliant elongated member 230 configured to be connected to one another in a series arrangement. The first connector 240 can be configured to connect a first end 211 of the hybrid tether 210 to an anchor disposed on or otherwise secured to the seabed. The second connector 250 can be configured to connect a second end 112 of the hybrid tether 110 to the floating structure. As shown, the first and second connectors 240, 250 can be dual axis joints. In other embodiments, however, the first and second connectors 240, 250 can independently be any other type of connector as described above with reference to the first and second connectors 140 and 150.

[0039] In some embodiments, a first end 221 of the stiff elongated member 220 can be the first end of the 211 of the hybrid tether 210, as shown in Figure 2. A second end 222 of the stiff elongated member 220 can be connected to a first end 231 of the compliant elongated member 230. In some embodiments, a second end 232 of the compliant elongated member 230 can bethe second end 212 of the hybrid tether 210, as described above with reference to Figure 1. In some embodiments, the connector 250 can be configured as a multi-axis joint that can include a rigid lever arm 270 that the second end 212 of the hybrid tether 210 can be configured to be connected to.

[0040] It should be understood that the hybrid tether 210 can be oriented in the opposite direction with respect to the orientation shown in Figure 2 such that the stiff elongated member 270 can be configured to connect to the first connector 240 and the first end 221 of the stiff elongated member 220 can be configured to connect to the second connector 250. In such embodiments, an end of the stiff elongated member 270 can be the first end 211 of the hybrid tether 210 and the first end 221 of the stiff elongated member 220 can be the second end 212 of the hybrid tether 210.

[0041] In some embodiments, the stiff elongated member 220 can include a plurality of stiff elongated members connected to one another in a series arrangement. For example, as shown in Figure 2, the stiff elongated member 220 can include a first stiff elongated member 223, a second stiff elongated member 224, and a third stiff elongated member 225 connected to one another in a series arrangement. In some embodiments, the stiff elongated member 220 can include one, two, three, four, five, six, seven, eight, nine, ten, or more stiff elongated members connected to one another in a series arrangement. The first, second, and third stiff elongated members 223, 224, 225 can have any desired length. In some embodiments, the length of the first, second, and third stiff elongated members 223, 224, 225 can be the same or different with respect to one another.

[0042] In some embodiments, when the hybrid tether 210 includes the plurality of stiff elongated members 223, 224, and 225, as shown, adjacent stiff elongated members can be rotatable with respect to one another. In some embodiments, adjacent stiff elongated members, e.g., the stiff elongated members 223 and 224 and the stiff elongated members 224 and 225, can be connected to one another via single axis joints, e.g., a first single axis joint 226 and a second single axis joint 227, respectively. In some embodiments, an axis of rotation of the first single axis joint 226 and an axis of rotation of the second single axis joint 227 can be skewed with respect to one another. Said another way, an orientation of the single axis joints 226 and 227 can be configured such that the axis of rotation of the first single axis joint 226 can be nonparallel or “twisted” with respect to the axis of rotation of the second single axis joint 227 to allow the adjacent stiff elongated members, i.e., the stiff elongated members 223 and 224 andthe stiff elongated members 224 and 225, to rotate in different directions with respect to one another.

[0043] As shown in Figure 2, the stiff elongated member 220 and the compliant elongated member 230 can be coupled or otherwise connected to one another via a third connector 260. In some embodiments, the third connector 260 can include an H-link connector, a twisted fllink connector, a dual axis joint, a pad-eye connector, a clevis connector, a plate link connector, a length adjustment connector, a segment of wire rope, a segment of chain, or any combination thereof. As shown in Figures 2 and 3, in some embodiments, the third connector 260 can include a first twisted H-link connector 261 coupled or otherwise connected to the second end 222 of the stiff elongated member 220, a second twisted H-link connector 262 coupled or otherwise connected to the first end 231 of the compliant elongated member 230, and the first and second twisted H-link connectors 261, 262 can be coupled or otherwise connected to opposing sides of a length adjustment connector 263. The length adjustment connector can utilize one or more link plates 264, 265, or 266 that have different lengths with respect to one another to allow for an adjustment in the overall length of the hybrid tether 210. As shown, the shortest link plate 264 connects the first and second twisted H-links 261, 262 together. If it is desired to increase the length of the hybrid tether 210, the link plate 265 or the link plate 266, which each have an increased length as compared to the link plate 264, can be used to connect the first and second twisted H-links 261, 262 together. In some embodiments, the length adjustment connector 263 can be the length adjustment connector described in WO Publication No. WO 2022 / 050935. In other embodiments, the third connector 260 can include any other type of connector or combination of connectors.

[0044] Figure 4 depicts an elevation view of an illustrative offshore floating platform system 400 that includes a hull structure 405 and a vertically arranged mooring system 415 having a first configuration, according to or more embodiments. Figure 5 depicts an elevation view of another illustrative offshore floating platform system 500 that includes the hull structure 405 and a vertically arranged mooring system 515 having a second configuration, according to or more embodiments. As shown in Figures 4 and 5, the vertically arranged mooring systems 415 and 515 can include the system 100 that includes the hybrid tether 110, the first connector 140, and the second connector 150, as described above with reference to Figure 1. The difference between the vertically arranged mooring systems 415 and 515 is that the hybrid tether 110 in the vertically arranged mooring system 415 has the stiff elongated member 120 connected to the first connector 140 and the compliant elongated member 130 connected to thesecond connector 150, whereas the vertically arranged mooring system 515 has the compliant elongated member 130 connected to the first connector 140 and the stiff elongated member 120 connected to the second connector 150. In some embodiments, the vertically arranged mooring systems 415, 515 can include the system 200 that includes the hybrid tether 210, the first connector 240, and the second connector 250, as described above with reference to Figures 2 and 3.

[0045] In some embodiments the hull structure 405 can be configured to float on a surface 403 of a body of water 401 and can be subjected to met-ocean conditions such as wind, current, and waves that can impart a motion to the floating platform system 400. In some embodiments, the hull structure 405 can be any type of structure including a semisubmersible shaped hull, a barge shaped hull, a spar shaped hull, a ship shaped hull, a platform, or any other type of hull configuration. In some embodiments, the hull structure 405 can be a concrete structure, a fabricated steel structure, or a combination thereof. In some embodiments, the hull structure 405 can include at least one column (two are shown / visible in Figure 4) 406, 407, at least one pontoon 408, and a deck structure 409 that can be supported by the column(s) 406, 407. In some embodiments, the hull structure 405 can include three columns and three pontoons. In some embodiments, the hull structure 405 can include four columns and at four pontoons. In some embodiments, the hull structure 405 can include four or more columns and four or more pontoons. In some embodiments, the hull structure 405 can be a platform and the offshore floating platform system 400 can be a tension leg platform (TLP).

[0046] In some embodiments, the vertically arranged mooring systems 415 and 515 can be configured to maintain the hull structure 405 within a specified tolerance in a lateral direction, i.e., in a surge and / or in a sway and / or in a yaw direction, when the offshore floating platform system 400 is subjected to met-ocean conditions. In some embodiments, the vertically arranged mooring systems 415 and 515 can include one or more hybrid tethers. As shown, the vertically arranged mooring systems 415 and 515 can include one or more of the hybrid tethers 110 described above with reference to Figure 1 (two are shown). The hybrid tether(s) 110 can secure the hull structure 405 to a seabed 404 via one or more anchors 435 (two are shown). In some embodiments, the vertically arranged mooring systems 415 and 515 can include I, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or more of the hybrid tethers 110. In some embodiments, the vertically arranged mooring systems 415 and 515 can be configured such that the hybrid tether(s) 110 can be substantially vertical.

[0047] The first end 111 of the hybrid tether(s) 110 can be configured to be connected to a corresponding anchor 435 via the first connectors 140 and the second end 112 of the hybrid tethers can be configured to be connected to the hull structure 405 via the second connectors 150. In some embodiments, the anchors 435 can be configured to react an uplift force, a lateral force, or a combination thereof. In some embodiments the anchors 435 can be a suction pile, a driven pile, a gravity anchor, or a combination thereof. The particular configuration of the anchors 435 can be based, at least in part, on the type of seabed 404, e.g., soil conditions, at the site and the loading expected to be applied on the anchors 435 when connected to the hull structure 405 via the hybrid tethers 110.

[0048] In some embodiments, when the hull structure 405 and the anchors 435 are connected via the hybrid tethers 110, the hybrid tethers 110 can include a pretension such that the hybrid tethers 110 can always be in tension as the hull structure 405 moves when the systems 400, 500 are subjected to the met-ocean conditions. In some embodiments, the pretension can be selected to avoid snap loading on the hybrid tethers 110. In some embodiments, the pretension can be about 250 tons, about 300 tons, about 350 tons, or about 400 tons to about 450 tons, about 500 tons, about 550 tons, or more. In some embodiments, the pretension can be about 250 tons to about 300 tons, about 300 tons to about 450 tons, or about 450 tons to about 550 tons. The selection of the pretension of the hybrid tethers 110 can be based, at least in part, on the met-ocean conditions expected at the site, the water depth, the properties of the hybrid tethers 110, the dimensions of the hull structure 405, or any combination thereof.

[0049] In some embodiments, a length of the hybrid tethers 110 can be determined such that upon connection to the hull structure 405 and the anchor 435 the desired pretension can be provided. In some embodiments, the length of the hybrid tethers 110 can be adjusted via the optional length adjustment connector 263, as described above with reference to Figures 2 and 3. In other embodiments, the length of the hybrid tethers 110 can be adjusted via the second connectors 150, when the second connectors 150 are length adjustment connectors. In other embodiments, the length of the hybrid tethers 110 can be adjusted via the optional length adjustment connector 263 and / or via the second connectors 150, when the second connectors 150 are length adjustment connectors. For example, the second connectors 150 can include the length adjustment connectors described in WO Publication No. 2022 / 050935. In other embodiments, a segment of wire rope or chain can be used to connect the second ends 112 of the hybrid tethers 110 to the hull structure 110 and / or the first ends 111 of the hybrid tethers 110 to the anchors 435. In such embodiments, the segment of wire rope or chain can be usedto apply the pretension in the hybrid tethers 110. In such embodiments, the segment of wire rope or chain can also be used to adjust the pretension in the hybrid tethers 110. For example, over time the pretension can reduce due to elongation of the compliant elongated members 130 and, after a certain period of time, the length of the wire rope and / or chain between the hybrid tethers 110 and the anchors 435 and / or the hybrid tethers 110 and the hull structure 405 can be reduced to increase the pretension.

[0050] In some embodiments, a vertical distance between the surface 403 of the body of water 401 and the seabed 404 can be referred to as a water depth. In some embodiments, the water depth can be about 60 meters, about 75 meters, about 100 meters, about 200 meters, about 300 meters, about 400 meters, or about 500 meters to about 600 meters, about 700 meters, about 800 meters, about 900 meters, about 1,000 meters, about 1,200 meters, about 1,400 meters or more. In some embodiments, the water depth can be about 60 meters to about 300 meters, about 300 meters to about 500 meters, or about 500 meters to about 1,000 meters, or greater than 1,000 meters. In some embodiments, the length of the compliant elongated members 130 can be about 70 meters or less, about 60 meters or less, about 55 meters or less, about 50 meters or less, about 45 meters or less, about 40 meters or less, or about 35 meters or less.

[0051] Figure 6 depicts an isometric view of another illustrative offshore floating platform system 600 that can include a semisubmersible, triangular hull structure 605 and a vertically arranged mooring system 607, according to one or more embodiments. The hull structure 605 can be floating on the surface 403 of the body of water 401 and can be subjected to met-ocean conditions that can impart forces onto the floating platform system 600. In some embodiments, the hull structure 605 can include a first column 611, a second column 612, and a third column 613. In some embodiments, the first, second, and third columns 611, 612, 613 can be fabricated steel structures, steel reinforced concrete structures, or a combination thereof. In some embodiments, the first column 611, the second column 612, and the third column 613 can be configured in a triangular arrangement when viewed in a plan view.

[0052] In some embodiments, the hull structure 605 can include a first pontoon 614, a second pontoon 615, and a third pontoon 616. In some embodiments, the first column 611 can be connected to the second column 612 via the first pontoon 614, the second column 612 can be connected to the third column 613 via the second pontoon 615, and the third column 613 can be connected to the first column 611 via the third pontoon 616. The first, second, and third pontoons 614, 615, 616 can be connected toward or at a first or lower end of the columns 611, 612, 613. In some embodiments, the first pontoon 614, the second pontoon 615, and the thirdpontoon 616 can be at least partially disposed below the surface of the body of water 601. In some embodiments, the first, second, and third pontoons 614, 615, 616 can be fabricated steel structures, steel reinforced concrete structures, or a combination thereof.

[0053] In some embodiments, the first column 611, the second column 612, and the third column 613 can be rigidly or fixedly connected to one another via a structural frame 617. The structural frame 617 can be connected toward or at a second or upper end of the columns 611, 612, 613. In some embodiments, the structural frame 617 can be disposed above the surface 403 of the body of water 401. In some embodiments, the structural frame 617 can be a fabricated steel structure, steel reinforced concrete structure, or a combination thereof.

[0054] The hull structure 605 can be configured to be connected to the vertical mooring system 607. In some embodiments, the first column 611, the second column 612, and the third column 613 can each be configured to connect to one or more of the hybrid tethers 110. For example, as shown in Figure 6, each of the first, second, and third columns 611, 612, and 613 can be connected to two hybrid tethers via a second connector 150. In other embodiments, the first, second, and third pontoons 614, 616, and 616 can each be configured to connect to one or more of the hybrid tethers 110. In some embodiments, the first, second, and third columns 611, 612, 613 and / or the first, second, and third pontoons 614, 615, and 616 can be configured to connect to 1, 2, 3, 4, 5, 6, 7, 8, or more of the hybrid tethers 110. In some embodiments, the number of hybrid tethers 110 each column 611, 612, 613 can be connected to can be the same or different with respect to one another. In some embodiments, two of the columns, e.g., 611, 612, can be connected to the same number of hybrid tethers 110, e.g. two, and the other column 613 can be connected to a different number of hybrid tethers 110, e.g., three.

[0055] In some embodiments, the vertically arranged mooring system 607 can include a corresponding anchor 435 for each hybrid tether 110, as shown. In other embodiments, when two or more hybrid tethers 110 are connected to the same column (as shown) and / or the same pontoon, a single anchor 435 can be used to moor the first ends 111 of the two or more hybrid tethers 110 to the seabed 404. In still other embodiments, a single anchor having a sufficient size, e.g., a footprint of sufficient size, can be used to connect all the hybrid tethers 110 thereto, e.g., all the hybrid tethers 110 shown in Figure 6 could be connected to a single anchor 435 having sufficient size and sufficiently secured to the seabed 404. In some embodiments, the anchors 435 can independently be a suction pile, a driven pile, a gravity anchor, or a combination thereof. The anchors 435 can each be designed to react an uplift force or a lateral force or a combination thereof. The particular configuration of the anchors 435 can be based,at least in part, on the type of seabed 404, e.g., soil conditions, at the site and the loading expected to be applied on the anchors 435 when connected to the hull structure 410 via the hybrid tethers 110.

[0056] The vertically arranged mooring system 607 can be configured to maintain the hull structure 605 within a specified tolerance in a lateral direction, i.e., in a surge and / or in a sway and / or yaw direction, when the offshore floating platform system 600 is subjected to the met- ocean conditions. In some embodiments, the hybrid tethers 110 can each be configured to have a pretension such that the hybrid tethers 110 are always in tension as the hull structure 605 moves when the offshore floating platform system 600 is subjected to the met-ocean conditions, as described above with reference to the offshore floating platform systems 400 and 500.

[0057] In some embodiments, the anchors 435 can be positioned on or secured to the seabed 404 such that the hybrid tethers 110 can each be oriented vertically or substantially vertically with respect to the earth when the offshore floating platform systems 400, 500, and 600 are in a neutral horizontal position.

[0058] In some embodiments, the vertically arranged mooring system 607 can be configured such that a mean or average tension in the hybrid tethers 110 can remain substantially equivalent to one another as the hull structure 605 of the offshore floating platform system 600 moves in a lateral, i.e., in a surge and / or in a sway and / or yaw direction, when the offshore floating platform system 600 is subjected to met-ocean conditions. The term “substantially equivalent” with respect to the mean or average tension means that the mean or average tension in the hybrid tethers 110 are all within + / - 20% of one another, within + / - 15% of one another, within + / - 10% of one another, or within + / - 5% of one another as the hull structure 605 moves in the lateral direction.

[0059] In some embodiments, the vertical distance between the surface 403 of the body of water 401 and the seabed 404 can be referred to as a water depth. In some embodiments, the water depth can be about 50 meters, about 75 meters, about 100 meters, about 200 meters, about 300 meters, about 400 meters, or about 500 meters to about 600 meters, about 700 meters, about 800 meters, about 900 meters, about 1,000 meters, about 1,200 meters, about 1,400 meters, or more.Prophetic Example

[0060] A simulation was carried out to determine a suitable configuration for hybrid tethers that can be used to moor a hull structure to a seabed at two different water depths. The hullstructure includes three columns, three pontoons that connect the columns to one another toward a first or bottom end that is below the surface of the water, and a structural frame that connects the columns to one another toward a second or top end that is above the surface of the water. The hull structure is secured to the seabed via a plurality of hybrid tethers secured to the seabed at a first end thereof and to the hull structure at a second end thereof.

[0061] In Example 1, the water depth is 72 meters. In Example 2, the water depth is 100 meters. The length of the hybrid tethers in Example 1 is 46 meters and the length of the hybrid tethers in Example 2 is 74 meters, with the length measured from the point of connection at the first and second ends of the hybrid tethers to the anchors and the hull structure. The properties and physical parameters of the hybrid tethers for Examples 1 and 2 are shown in the Table below.

[0062] The present disclosure further relates to any one or more of the following embodiments:

[0063] Al. A process for installing a tension leg platform system, comprising: providing a tension leg platform system comprising: a structure configured to float on a surface of a body of water; an anchor configured to be secured to a seabed of the body of water; a hybrid tether comprising a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement; a first connector configured to pivotally connect a first end of the hybrid tether to the anchor; and a second connector configured to pivotally connect a second end of the hybrid tether to the floating structure, wherein: an axial stiffness of the stiff elongated member is greater than an axial stiffness of the compliantelongated member, and the hybrid tether is configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure; securing the anchor to the seabed; positioning the structure on the surface of the body of water; connecting the stiff elongated member and the compliant elongated member to one another; connecting the first end of the hybrid tether to the anchor; and connecting the second end of the hybrid tether to the tension leg platform.

[0064] A2. The process of paragraph Al, wherein the stiff elongated member is composed of a metal, a metal alloy, carbon fiber, or a combination thereof, and wherein the compliant elongated member is composed of a synthetic polymer.

[0065] A3. The process of paragraph Al, wherein the stiff elongated member is composed of ultra-high-molecular-weight polyethylene, and wherein the compliant elongated member is composed of polyester, nylon, or a combination thereof.

[0066] A4. The process of any one of paragraphs Al to A3, wherein: the stiff elongated member is a hollow bar, a solid bar, a rope, a chain, or a combination thereof, the compliant elongated member is a rope, and the synthetic polymer comprises polyester, nylon, ultra-high- molecular-weight polyethylene, or a combination thereof.

[0067] A5. The process of any one of paragraphs Al to A3, wherein the stiff elongated member is composed of ultra-high-molecular- weight polyethylene, and wherein the compliant elongated member is composed of polyester, nylon, or a combination thereof.

[0068] A6.The process of any one of paragraphs Al to A5, wherein, an end of the stiff elongated member is the first end of the hybrid tether, and wherein an end of the compliant elongated member is the second end of the hybrid tether.

[0069] A7. The process of any one of paragraphs Al to A5, wherein an end of the compliant elongated member is the first end of the hybrid tether, and wherein an end of the stiff elongated member is the second end of the hybrid tether.

[0070] A8. The process of any one of paragraphs Al to A7, wherein the first connector comprises a first part disposed on the hybrid tether at or toward the first end thereof and a second part disposed on the anchor, and wherein the first part of the first connector and the second part of the first connector are configured to connect to one another.

[0071] A9. The process of any one of paragraphs Al to A8, wherein the second connector comprises a first part disposed on the hybrid tether at or toward the second end thereof and a second part configured to be disposed on the floating hull structure, and wherein the first partof the second connector and the second part of the second connector are configured to connect to one another.

[0072] A10. The process of any one of paragraphs At to A9, wherein the stiff elongated member comprises a plurality of elongated members configured to be connected to one another in a series arrangement.

[0073] Al l. The process of paragraph 10, wherein adjacent elongated members are rotatable with respect to one another.

[0074] A12. The system of paragraph A10 or paragraph Al l, wherein: each elongated member of the plurality of elongated members comprises a first single axis joint at a first end thereof and a second single axis joint at a second end thereof.

[0075] A13. The process of paragraph A12, wherein an axis of rotation of the first single axis joint and an axis of rotation of the second single axis joint of each elongated member of the plurality of elongated members are skewed with respect to one another.

[0076] A14. The process of any one of paragraphs Al to A13, wherein the stiff elongated member and the compliant elongated member are configured to be connected to one another via a length adjustment connector.

[0077] A15. The process of paragraph A14, further comprising increasing or decreasing a length of the hybrid tether by adjusting a length of the length adjustment connector.

[0078] A16. The process of any one of paragraphs Al to A15, wherein the second connector is a length adjustment connector.

[0079] A17. The process of paragraph A16, further comprising increasing or decreasing a pretension applied to the structure on the surface of the body of water by adjusting a length of the length adjustment connector.

[0080] Al 8. The process of any one of paragraphs Al to A17, wherein a ratio of the axial stiffness of the stiff elongated member to the compliant elongated member is in a range from about 2:1 to about 50:1.

[0081] A19. The process of any one of paragraphs Al to Al 8, wherein a ratio of the axial stiffness of the stiff elongated member to the compliant elongated member is in a range from about 2:1 to about 4: 1.

[0082] Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges including the combination of any two values, e.g., the combination of any lower value with any upper value, the combination of any two lower values, and / or the combination of any two upper values arecontemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are "about" or "approximately" the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

[0083] Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation can be permitted.

[0084] While certain preferred embodiments of the present invention have been illustrated and described in detail above, it can be apparent that modifications and adaptations thereof will occur to those having ordinary skill in the art. It should be, therefore, expressly understood that such modifications and adaptations may be devised without departing from the basic scope thereof, and the scope thereof can be determined by the claims that follow.

Claims

Claims:What is claimed is:

1. A system configured to moor a floating structure to a seabed, comprising: a hybrid tether comprising a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement; a first connector configured to connect a first end of the hybrid tether to an anchor secured to the seabed; and a second connector configured to connect a second end of the hybrid tether to the floating structure, wherein: the stiff elongated member is formed from a metal, a metal alloy, carbon fiber, or a combination thereof, the compliant elongated member is formed from a synthetic polymer, an axial stiffness of the stiff elongated member is greater than an axial stiffness of the compliant elongated member, the first connector is configured to allow the first end of the hybrid tether to pivot relative to the anchor, the second connector is configured to allow the second end of the hybrid tether to pivot relative to the floating structure, and the hybrid tether is configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure.

2. The system of claim 1, wherein: the stiff elongated member is a hollow bar, a solid bar, a rope, a chain, or a combination thereof, the compliant elongated member is a rope, and the synthetic polymer comprises polyester, nylon, ultra-high-molecular-weight polyethylene, or a combination thereof.

3. The system of claim 1, wherein the stiff elongated member is composed of ultra-high- molecular-weight polyethylene, and wherein the compliant elongated member is composed of polyester, nylon, or a combination thereof.

4. The system of any one of claims 1 to 3, wherein, an end of the stiff elongated member is the first end of the hybrid tether, and wherein an end of the compliant elongated member is the second end of the hybrid tether.

5. The system of any one of claims 1 to 3, wherein an end of the compliant elongated member is the first end of the hybrid tether, and wherein an end of the stiff elongated member is the second end of the hybrid tether.

6. The system of any one of claims 1 to 5, wherein the first connector comprises a first part disposed on the hybrid tether at or toward the first end thereof and a second part disposed on the anchor, and wherein the first part of the first connector and the second part of the first connector are configured to connect to one another.

7. The system of any one of claims 1 to 6, wherein the second connector comprises a first part disposed on the hybrid tether at or toward the second end thereof and a second part configured to be disposed on the floating hull structure, and wherein the first part of the second connector and the second part of the second connector are configured to connect to one another.

8. The system of any one of claims 1 to 7, wherein the stiff elongated member comprises a plurality of elongated members configured to be connected to one another in a series arrangement.

9. The system of claim 8, wherein adjacent elongated members are rotatable with respect to one another.

10. The system of claim 8 or claim 9, wherein: each elongated member of the plurality of elongated members comprises a first single axis joint at a first end thereof and a second single axis joint at a second end thereof, and an axis of rotation of the first single axis joint and an axis of rotation of the second single axis joint of each elongated member of the plurality of elongated members are skewed with respect to one another.

11. The system of any one of claims 1 to 10, wherein the stiff elongated member and the compliant elongated member are configured to be connected to one another via a length adjustment connector.

12. The system of any one of claims 1 to 11, wherein the second connector is a length adjustment connector.

13. The system of any one of claims 1 to 12, wherein a ratio of the axial stiffness of the stiff elongated member to the compliant elongated member is in a range from about 2: 1 to about 50:1.

14. A tension leg platform system, comprising: a structure configured to float on a surface of a body of water; an anchor configured to be secured to a seabed of the body of water; a hybrid tether comprising a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement; a first connector configured to pivotally connect a first end of the hybrid tether to the anchor; and a second connector configured to pivotally connect a second end of the hybrid tether to the floating structure, wherein: an axial stiffness of the stiff elongated member is greater than an axial stiffness of the compliant elongated member, and the hybrid tether is configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure.

15. The tension leg platform system of claim 14, wherein: the stiff elongated member is a hollow bar, a solid bar, a rope, a chain, or a combination thereof, the compliant elongated member is a rope, and the synthetic polymer comprises polyester, nylon, ultra-high-molecular-weight polyethylene, or a combination thereof.

16. The tension leg platform system of claim 14, wherein the stiff elongated member is composed of ultra-high-molecular-weight polyethylene, and wherein the compliant elongated member is composed of polyester, nylon, or a combination thereof.

17. The tension leg platform system of any one of claims 13 to 15, wherein: the stiff elongated member comprises a plurality of elongated members configured to be connected to one another in a series arrangement, each elongated member in the plurality of elongated members is independently a hollow bar or a solid bar, and adjacent elongated members in the plurality of elongated members are rotatable with respect to one another.

18. The tension leg platform system of claim 17, wherein: each elongated member in the plurality of elongated members comprises a first single axis joint at a first end thereof and a second single axis joint at a second end thereof, and an axis of rotation of the first single axis joint and an axis of rotation of the second single axis joint of each elongated member in the plurality of elongated members are skewed with respect to one another.

19. The tension leg platform system of any one of claims 13 to 17, wherein: a first end of the stiff elongated member is the first end of the hybrid tether, a second end of the compliant elongated member is the second end of the hybrid tether, and a second end of the stiff elongated member and a first end of the compliant elongated member are configured to be connected to one another.

20. A process for installing a tension leg platform system, comprising: providing a tension leg platform system comprising: a structure configured to float on a surface of a body of water; an anchor configured to be secured to a seabed of the body of water; a hybrid tether comprising a stiff elongated member and a compliant elongated member configured to be connected to one another in a series arrangement;a first connector configured to pivotally connect a first end of the hybrid tether to the anchor; and a second connector configured to pivotally connect a second end of the hybrid tether to the floating structure, wherein: an axial stiffness of the stiff elongated member is greater than an axial stiffness of the compliant elongated member, and the hybrid tether is configured to be substantially vertical when the first end of the hybrid tether is connected to the anchor and the second end of the hybrid tether is connected to the floating structure; securing the anchor to the seabed; positioning the structure on the surface of the body of water; connecting the stiff elongated member and the compliant elongated member to one another; connecting the first end of the hybrid tether to the anchor; and connecting the second end of the hybrid tether to the tension leg platform.

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