WO2024186911A1

WO2024186911A1 - Floating platforms that include vertically arranged mooring systems

Info

Publication number: WO2024186911A1
Application number: PCT/US2024/018700
Authority: WO
Inventors: Qi Xu; Qi Ling; Andrew Costa KYRIAKIDES
Original assignee: Modec International Inc
Current assignee: Modec International Inc
Priority date: 2023-03-07
Filing date: 2024-03-06
Publication date: 2024-09-12
Anticipated expiration: 2025-09-07
Also published as: KR20250160349A

Abstract

Offshore floating platform systems and processes for mooring same, In some embodiments, the offshore floating platform system can include a hull structure configured to float on a surface of a body of water, one or more anchors configured to be secured to a seabed, and one or more mooring lines configured to be connected to the hull structure at a first end thereof and to the anchor at a second end thereof. When the one or more anchors are secured to the seabed and the one or more mooring lines are connected to the hull structure and a corresponding anchor, the mooring lines can be substantially vertical and a peak response period of the offshore floating platform system in a pitch or a roll direction can be greater than a peak spectral period of a wave spectrum on the surface of the body of water.

Description

FLOATING PLATFORMS THAT INCLUDE VERTICALLY ARRANGED MOORING SYSTEMS

FIELD

[0001] Embodiments described generally relate to offshore floating platform systems. More particularly, such embodiments relate to floating platforms moored at an offshore location, e.g., at an offshore wind farm or drilling site, that include vertically arranged mooring systems.

BACKGROUND

[0002] In the offshore renewable industry, for example 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.

[0003] There is a need, therefore, for improved vertically arranged mooring systems for floating platforms at offshore locations.

SUMMARY

[0004] Offshore floating platform systems and processes for mooring offshore platforms are provided. In some embodiments, the offshore floating platform system can include a hull structure configured to float on a surface of a body of water, an anchor configured to be secured to a seabed, and a mooring line configured to be connected to the hull structure at a first end thereof and to the anchor at a second end thereof. When the anchor is secured to the seabed and the mooring line is connected to the hull structure and the anchor, the mooring line can be substantially vertical and a peak response period of the offshore floating platform system in a pitch or roll direction can be greater than a peak spectral period of a wave spectrum on the surface of the body of water.

[0005] In some embodiments, a process for mooring an offshore platform can include providing an offshore floating platform that includes a hull structure configured to float on a surface of a body of water, an anchor configured to be secured to a seabed, and a mooring line configured to be connected to the hull structure and the anchor. The process can also include securing the anchor to the seabed. The process can also include connecting a first end of the mooring line to the hull structure and a second end of the mooring line to the anchor. When the anchor is secured to the seabed and the mooring line is connected to the hull structure and the anchor, the mooring line can be substantially vertical and a peak response period of the offshore floating platform system in a pitch or a roll direction can be greater than a peak spectral period of a wave spectrum on the surface of the body of water.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] 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.

[0007] Figure 1 depicts an elevation view of an illustrative offshore floating platform system that includes a hull structure and a vertically arranged mooring system, according to or more embodiments described.

[0008] Figure 2 depicts an elevation view of another illustrative offshore floating platform system that includes a triangular hull structure and a vertically arranged mooring system, according to one or more embodiments described.

[0009] Figure 3 depicts a plan view of the illustrative offshore floating platform system shown in Figure 2.

[0010] Figure 4 depicts an isometric view of the illustrative offshore floating platform system shown in Figures 2 and 3.

[0011] Figure 5 graphically depicts an illustrative set of curves that includes a response amplitude operator (RAO) in a heave direction and a RAO in a pitch or a roll direction of an offshore floating platform system and a wave spectrum on the surface of the body of water, according to one or more embodiments described.

[0012] Figure 6 graphically depicts another illustrative set of curves that includes a RAO in a heave direction and a RAO in a pitch or a roll direction of another offshore floating platform system and a wave spectrum on the surface of the body of water, according to one or more embodiments described.

[0013] Figure 7 depicts an isometric view of an illustrative offshore floating platform system similar to the one shown in Figures 2 to 4 that further includes an optional wind turbine generator system disposed on the hull structure, according to one or more embodiments described. DETAILED DESCRIPTION

[0014] 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 disclosure describes 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.

[0015] 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.” [0016] 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.

[0017] 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.

[0018] The terms “resonance” and “resonate” describe the phenomenon of increased amplitude that occurs when the period of an applied periodic force (or a Fourier component of it) is equal or close to a natural period of an offshore floating platform system on which it acts. When an oscillating force is applied at a resonant period of a dynamic offshore floating platform system, the system will oscillate at a higher amplitude than when the same force is applied at other, non-resonant periods of the dynamic offshore floating platform system. Periods at which the response amplitude operator is a maximum are also known as resonant periods or resonance periods of the offshore floating platform system. Small periodic forces that are near a resonant period of the offshore floating platform system can produce large amplitude oscillations in the system due to the storage of vibrational energy.

[0019] The term “Response Amplitude Operator” or “RAO” is a parameter or set of parameters that are used to determine the motion behavior of the offshore floating platform system in a floating condition. RAOs are, therefore, transfer functions used to determine the effect that incident waves will have on the motion of the offshore floating platform system. In offshore engineering, RAOs can be represented in graphic form as the motion response of the offshore floating platform system for a particular degree of freedom plotted against the period of the incident waves. The highest value of the RAO of an oscillating offshore floating platform system can then be defined as the peak response period, which can also be referred to as the natural period of the system or as the resonant period of the system. [0020] The term “met-ocean conditions” refers to the conditions at the site at which the offshore floating platform system is located. Met-ocean conditions can include any combination of wind, waves, swells, currents, squalls, tropical storms, and storm surge conditions that can impart a force onto the offshore floating platform system.

[0021] The terms “peak spectral energy period” and “peak spectral period” refer to the wave period associated with the most energetic waves in a wave spectrum on the surface of the body of water.

[0022] The term “cancellation period” refers to the period at which a heave motion of an offshore floating platform system is minimized by balancing the wave forces acting on a pontoon of the offshore floating platform system and the wave forces acting on a column of the offshore floating platform system. The wave forces acting on the pontoon(s) of the offshore floating platform system can be substantially caused by the water particle acceleration and can, therefore, be in an opposite phase of the incident waves, while the wave forces acting on the column(s) of the offshore floating platform system can be substantially caused by the wave pressure (Froude-Krylov force) and can, therefore, be substantially in phase with the incident waves. For this reason, the heave motion of the offshore floating platform system can be minimized at the cancellation period.

[0023] Figure 1 depicts an elevation view of an illustrative offshore floating platform system 100 that includes ahull structure 110 and a vertically arranged mooring system 120, according to or more embodiments. In some embodiments the hull structure 110 can be configured to float on a surface 103 of a body of water 101 and can be subjected to met-ocean conditions such as wind, current, and waves that can cause the floating platform system 100 to move in response thereto. In some embodiments, the hull structure 110 can be any type of structure including a semisubmersible shaped hull, a barge shaped hull, a spar shaped hull, a ship shaped hull, or any other type of hull configuration. In some embodiments, the hull structure can be a concrete structure, a fabricated metal, e.g., steel, structure, or a combination thereof. In some embodiments, the hull structure 110 can include at least one column (two are shown/visible in Figure 1) 111, 112, at least one pontoon (one is shown/visible in Figure 1) 114, and a deck structure 115 that can be supported by the column(s) 111, 112. In some embodiments, the hull structure 110 can include three columns and three pontoons. In some embodiments, the hull structure 110 can include four columns and four pontoons. In some embodiments, the hull structure 110 can include four or more columns and four or more pontoons. [0024] In some embodiments, the vertically arranged mooring system 120 can be configured to maintain the hull structure 110 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 100 is subjected to met-ocean conditions. In some embodiments, the vertically arranged mooring system 120 can include one or more mooring lines 131 and one or more anchors 121. A first end of the mooring line 131 can be configured to be connected to the hull structure 110 and a second end of the mooring line 131 can be configured to be connected to the anchor 121. In some embodiments, the vertically arranged mooring system 120 can include a plurality of mooring lines 131, e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or more.

[0025] In some embodiments the vertically arranged mooring system 120 be configured such that the mooring line(s) 131 can be vertical or substantially vertical when the floating platform system 100 is in a neutral state or position. The neutral state or position refers to the position of the floating platform system 100 when the floating platform system 100 is not subjected to any met-ocean conditions. The term “substantially vertical” means the mooring line(s) 131 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 the mooring line(s) is substantially vertical, the mooring line(s) 131 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.

[0026] In some embodiments the mooring line(s) 131 can be formed from a synthetic rope. In some embodiments, the synthetic rope can be a synthetic polymer rope. In some embodiments, the synthetic polymer making up the synthetic polymer rope can be or can include, but is not limited to, polyester, nylon, ultra-high-molecular-weight polyethylene (UHMWPE), or any combination thereof. In other embodiments, at least a portion of the mooring line(s) 131 can be formed from a synthetic rope and at least a portion of the mooring line(s) 131 can be formed from a wire rope and/or a chain and/or other elongated members. In some embodiments, the mooring line 131 can be configured with one or more segments of polyester rope, such as DEEPROPE® polyester rope marketed by Bexco, or MOORLINE® polyester rope marketed by Bridon, or CABRAL 512® polyester rope marketed by Lankhorst, or DYNEEMA® UHMWPE rope marketed by DSM, or any other synthetic rope that has suitable properties.

[0027] The one or more anchors 121 can be configured to be secured to a seabed 105. In some embodiments, the anchor 121 can be configured to transfer an uplift force, a lateral force, or a combination thereof from the mooring line 131 to the seabed 105. In some embodiments the anchor 121 can be a suction pile, a driven pile, a gravity anchor, or a combination thereof. The particular configuration of the anchor 121 can be based, at least in part, on the type of seabed 105, e.g., soil conditions, at the site and the loading expected to be applied on the anchor 121 when connected to the hull structure 110 via the mooring line 131.

[0028] In some embodiments, when the hull structure 110 and the one or more anchors 121 are connected to one another via the one or more mooring lines 131. The mooring line(s) 131 can include a pretension such that the mooring line(s) 131 can always be in tension as the hull structure 110 moves when the system 100 is subjected to the met-ocean conditions. In some embodiments, the pretension can be selected to avoid snap loading on the mooring line(s) 131. In some embodiments, the pretension can be about 50 tonnes, about 100 tonnes, about 150 tonnes, about 200 tonnes, about 225 tonnes, about 250 tonnes, about 300 tonnes, about 350 tonnes, or about 400 tonnes to about 450 tonnes, about 500 tonnes, about 550 tonnes, or more. In some embodiments, the pretension can be about 225 tonnes to about 300 tonnes, about 300 tonnes to about 450 tonnes, or about 450 tonnes to about 550 tonnes. The selection of the pretension of the mooring line(s) 131 can be based, at least in part, on the met-ocean conditions expected at the site, the water depth, the properties of the mooring line(s) 131, the dimensions of the hull structure 110, or any combination thereof.

[0029] In some embodiments, a length of the mooring line(s) 131 can be determined such that upon connection to the hull structure 110 and the anchor 121 the desired pretension can be provided. In other embodiments, a segment of wire rope or chain can be used to connect the first end of the mooring line 131 to the hull structure 110 and/or the second end of the mooring line 131 to the anchor 121. In such embodiments, the segment of wire rope or chain can be used to apply the pretension in the mooring line 131. In such embodiments, the segment of wire rope or chain can also be used to adjust the pretension in the mooring line 131. For example, over time the pretension can reduce due to elongation of the synthetic rope and after a certain period of time the length of the wire rope and/or chain between the synthetic rope and the anchor 121 and/or the synthetic rope and the hull structure 110 can be reduced to increase the pretension. In other embodiments, the mooring line(s) 131 can be connected to the anchor 121 and/or the hull structure 110 via a length adjustment connector.

[0030] In some embodiments, a vertical distance between the surface 103 of the body of water 101 and the seabed 105 can be referred to as a water depth. In some embodiments, the water depth can be 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 200 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.

[0031] Figures 2, 3, and 4 depict an elevation view, a plan view, and an isometric view, respectively, of an illustrative offshore floating platform system 200 that includes a semisubmersible, triangular shaped hull structure 210 and a vertically arranged mooring system 220, according to one or more embodiments. In some embodiments the hull structure 210 can be floating on a surface 203 of a body of water 201 and can be subjected to met-ocean conditions that can impart forces onto the floating platform system 200. In some embodiments, the hull structure 210 can include a first column 211, a second column 212, and a third column 213. In some embodiments, the first, second, and third columns 211, 212, 213 can be fabricated steel structures, steel reinforced concrete structures, or a combination thereof. In some embodiments, the first column 211, the second column 212, and the third column 213 can be configured in a triangular arrangement when viewed in a plan view.

[0032] In some embodiments, the hull structure 210 can include a first pontoon 214, a second pontoon 215, and a third pontoon 216. In some embodiments, the first column 211 can be connected to the second column 212 via the first pontoon 214, the second column 212 can be connected to the third column 213 via the second pontoon 215, and the third column 213 can be connected to the first column 211 via the third pontoon 216. The first, second, and third pontoons 214, 215, 216 can be connected toward or at a first or lower end of the columns 211, 212, 213. In some embodiments, the first pontoon 214, the second pontoon 215, and the third pontoon 216 can be at least partially disposed below the surface of the body of water 201. In some embodiments, the first, second, and third pontoons 214, 215, 216 can be fabricated steel structures, steel reinforced concrete structures, or a combination thereof.

[0033] In some embodiments, the first column 211, the second column 212, and the third column 213 can be rigidly or fixedly connected to one another via a structural frame 217. The structural frame 217 can be connected toward or at a second or upper end of the columns 211, 212, 213. In some embodiments, the structural frame 217 can be disposed above the surface 203 of the body of water 201. In some embodiments, the structural frame 217 can be a fabricated steel structure, steel reinforced concrete structure, or a combination thereof.

[0034] The hull structure 210 can be configured to be connected to the vertical mooring system 220. In some embodiments, the first column 211, the second column 212, and the third column 213 can each be configured to connect to one or more corresponding mooring lines. In other embodiments, the first pontoon 214, the second pontoon 215, and the third pontoon 216 can each be configured to connect to one or more corresponding mooring lines. In some embodiments, the first column 211, the second column 212, and the third column 213 can each be configured to connect to one corresponding mooring line, two corresponding mooring lines, three corresponding mooring lines, or more. In other embodiments, the first pontoon 214, the second pontoon 215, and the third pontoon 216 can each be configured to connect to one corresponding mooring line, two corresponding mooring lines, three corresponding mooring lines, or more. The vertically arranged mooring system 220 can be configured to maintain the hull structure 210 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 200 is subjected to met- ocean conditions.

[0035] In some embodiments, the vertically arranged mooring system 220 can include a first anchor 221 , a second anchor 222, and a third anchor 223. In some embodiments the first anchor 221, the second anchor 222, and the third anchor 223 can each be a suction pile, a driven pile, a gravity anchor, or a combination thereof. In some embodiments, the first anchor 221, the second anchor 222, and the third anchor 223 can each be configured to be secured to a seabed 205 and can be configured to connect to or receive one or more mooring lines. In other embodiments, the first anchor 221, the second anchor 222, and the third anchor 223 can each be configured to connect to or receive two mooring lines, three mooring lines, or more. In some embodiments, the first anchor 221, the second anchor 222, and the third anchor 223 can each be designed to transfer an uplift force or a lateral force or a combination thereof from the corresponding mooring line 231, 232, 233 to the seabed 205. The particular configuration of the anchors 221, 222, 223 can be based, at least in part, on the type of seabed 205, e.g., soil conditions, at the site and the loading expected to be applied on the anchors 221, 222, 223 when connected to the hull structure 210 via the mooring lines.

[0036] In some embodiments, the vertically arranged mooring system 220 can include a first mooring line 231, a second mooring line 232, and a third mooring line 233. In some embodiments, the first mooring line 231 can be configured to be connected to the first column 211 at a first end thereof and to the first anchor 221 at a second end thereof, the second mooring line 232 can be configured to be connected to the second column 212 at a first end thereof and to the second anchor 222 at a second end thereof, and the third mooring line 233 can be configured to be connected to the third column 213 at a first end thereof and to the third anchor 223 at a second end thereof.

[0037] In some embodiments the first mooring line 231, the second mooring line 232 and the third mooring line 233 can each be formed from a synthetic rope. In other embodiments, at least a portion of the first, second, and third mooring lines 231, 232, and 233 can be formed from a synthetic rope and at least a portion of the first, second, and third mooring lines 231, 232, 233 can be formed from a wire rope and/or a chain and/or other elongated members. In some embodiments, the synthetic rope can be a formed from or otherwise include a synthetic polymer. 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 synthetic polymer rope can be or can include a 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 rope available from DSM, or any other synthetic polymer rope that has suitable properties.

[0038] In some embodiments, the first mooring line 231 , the second mooring line 232, and the third mooring line 233 can each be configured to have a pretension such that the first mooring line 231, the second mooring line 232, and the third mooring line 233 are always in tension as the hull structure 210 moves when the offshore floating platform system 200 is subjected to the met-ocean conditions. In some embodiments the pretension can be selected to avoid snap or shock loading on the first mooring line 231, the second mooring line 232, and/or the third mooring line 233. In some embodiments, the pretension can be about 50 tonnes, about 100 tonnes, about 150 tonnes, about 200 tonnes, about 225 tonnes, about 250 tonnes, about 300 tonnes, about 350 tonnes, or about 400 tonnes to about 450 tonnes, about 500 tonnes, about 550 tonnes, or more. In some embodiments, the pretension can be about 225 tonnes to about 300 tonnes, about 300 tonnes to about 450 tonnes, or about 450 tonnes to about 550 tonnes or more. The selection of the pretension of the first mooring line 221, the second mooring line 222, and the third mooring line 223 can be based, at least in part, on the met-ocean conditions expected at the site, the water depth, the properties of the mooring lines 231, 232, 233, the dimensions of the hull structure 210, or any combination thereof.

[0039] In some embodiments, the first anchor 221, the second anchor 222, and the third anchor 223 can be positioned on or secured to the seabed 205 such that the first mooring line 231 , the second mooring line 232, and the third mooring line 233 can each be oriented vertically or substantially vertical with respect to the earth. As such, the first mooring line 231, the second mooring line 232, and the third mooring line 233 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.

[0040] In some embodiments, the vertically arranged mooring system 220 can be configured such that a mean or average tension in the first mooring line 231, a mean or average tension in the second mooring line 232, and a mean or average tension in the third mooring line 233 can remain substantially equivalent to one another as the hull structure 210 of the offshore floating platform system 200 moves in a lateral, i.e., in a surge and/or in a sway and/or yaw direction, when the offshore floating platform system 200 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 first mooring line 231, the mean or average tension in the second mooring line 232, and the mean or average tension in the third mooring line 233 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 210 moves in the lateral direction.

[0041] In some embodiments, the vertically arranged mooring system 220 can further include a fourth mooring line 234, a fifth mooring line 235, and a sixth mooring line 236. The fourth mooring line 234 can be connected to the first column 211 at a first end thereof and to the first anchor 221 at a second end thereof, the fifth mooring line 235 can be connected to the second column 212 at a first end thereof and to the second anchor 222 at a second end thereof, and the sixth mooring line 236 can be connected to the third column 213 at a first end thereof and to the third anchor 223 at a second end thereof. In some embodiments the fourth mooring line 234, the fifth mooring line 235, and the sixth mooring line 236 can each be formed from a synthetic rope. In other embodiments, at least a portion of the fourth, fifth, and/or sixth mooring lines 234, 235, and 236 can be formed from a synthetic rope and at least a portion of the first, second, and/or third mooring lines 234, 235, 236 can be formed from a wire rope and/or a chain and/or other elongated members.

[0042] In some embodiments, the synthetic rope can be formed from or otherwise include a synthetic polymer. 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 synthetic polymer rope can be or can include a 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 rope available from DSM, or any other synthetic polymer rope that has suitable properties.

[0043] In some embodiments, the fourth mooring line 234, the fifth mooring line 235, and the sixth mooring line 236 can each be configured to have a pretension such that the fourth mooring line 234, the fifth mooring line 235, and the sixth mooring line 236 are always in tension as the hull structure 210 moves when the system 200 is subjected to the met-ocean conditions. In some embodiments the pretension can be selected to avoid snap or shock loading on the fourth mooring line 234, the fifth mooring line 235, and/or the sixth mooring line 236. In some embodiments, the pretension can be about 50 tonnes, about 100 tonnes, about 150 tonnes, about 200 tonnes, about 225 tonnes, about 250 tonnes, about 300 tonnes, about 350 tonnes, or about 400 tonnes to about 450 tonnes, about 500 tonnes, about 550 tonnes, or more. In some embodiments, the pretension can be about 225 tonnes to about 300 tonnes, about 300 tonnes to about 450 tonnes, or about 450 tonnes to about 550 tonnes or more. The selection of the pretension of the fourth mooring line 234, the fifth mooring line 235, and the sixth mooring line 236 can be based, at least in part, on the met-ocean conditions expected at the site, the water depth, the properties of the mooring lines 234, 235, 236, the dimensions of the hull structure 210, or any combination thereof.

[0044] In some embodiments, the vertically arranged mooring system 220 can include a fourth anchor 224, a fifth anchor 225, and a sixth anchor 226 that the fourth, fifth, and sixth mooring lines 234, 235, 236, respectively, can be connected, as shown. In such embodiments, the fourth mooring line 234 can be connected to the first column 211 at a first end thereof and to the fourth anchor 224 at a second end thereof, the fifth mooring line 235 can be connected to the second column 212 at a first end thereof and to the fifth anchor 225 at a second end thereof, and the sixth mooring line 236 can be connected to the third column 213 at a first end thereof and to the sixth anchor 223 at a second end thereof. In other embodiments, the fourth, fifth, and sixth mooring lines 234, 235, and 236 can be connected to the hull structure 210 at a first end thereof and to the first, second, and third anchors 221, 222, 223, respectively (not shown). [0045] In some embodiments, the fourth anchor 224, the fifth anchor 225, and the sixth anchor 226 can each be designed to transfer an uplift force, a lateral force, or a combination thereof from the corresponding mooring line 234, 245, 236 to the seabed 205. In some embodiments the fourth anchor 224, the fifth anchor 225, and the sixth anchor 226 can each be configured as a suction pile, a driven pile, or a gravity anchor. The particular configuration of the anchors 224, 225, 226 can be based, at least in part, on the type of seabed 205, e.g., soil conditions, at the site and the loading expected to be applied on the anchors 224, 225, 226 when connected to the hull structure 210 via the mooring lines.

[0046] In some embodiments, the fourth anchor 224, the fifth anchor 225, and the sixth anchor 226 can be positioned such that the fourth mooring line 234, the fifth mooring line, 235 and the sixth mooring line 236 can each be oriented vertically or substantially vertically with respect to the earth. In other embodiments the fourth anchor 224, the fifth anchor 225 and the sixth anchor 226 can be positioned on or secured to the seabed 205 such that the fourth mooring line 231 , the fifth mooring line 232 and the sixth mooring line can each be substantially vertical. [0047] In some embodiments, the vertically arranged mooring system 220 can be configured such that a mean or average tension in the first mooring line 231, a mean or average tension in the second mooring line 232, a mean or average tension in the third mooring line 233, and, if present, a mean or average tension in the fourth mooring line 234, a mean or average tension in the fifth mooring line 235, and/or a mean or average tension in the sixth mooring line 236 can remain substantially equivalent to one another as the hull structure 210 of the offshore floating platform system 200 moves in a lateral or surge or sway direction when the offshore floating platform system 200 is subjected to met-ocean conditions. In some embodiments substantially equivalent to one another means that the mean or average tension in the first mooring line 231, the mean or average tension in the second mooring line 232, the mean or average tension in the third mooring line 233, and, if present, the mean or average tension in the fourth mooring line 234, the mean or average tension in the fifth mooring line 235, and/or the mean or average tension in the sixth mooring line 235 are all within 20% of one another, or are all within 15% of one another, or are all within 10% of one another, or are all within 5% of one another as the hull structure 210 moves in the lateral or surge or sway direction.

[0048] It should be understood, in some embodiments, the mooring system 220 can include three anchors and three mooring lines, with each mooring line configured to connect to the hull structure 210 and a corresponding anchor. In other words, in some embodiments, the vertically arranged mooring system 220 can include the first anchor 221, the second anchor 222, and the third anchor 223 and the first mooring line 231, the second mooring line 232, and the third mooring line 233.

[0049] In some embodiments, the vertical distance between the surface 203 of the body of water 201 and the seabed 205 can be referred to as the water depth. In some embodiments, the water depth can be 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 200 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.

[0050] Prophetic examples are carried out via a computer simulation of two offshore floating platform systems that include a hull structure moored to a seabed via a vertically arranged mooring system. The hull structure includes three columns and three pontoons connecting the columns to one another in a triangular configuration. The vertically arranged mooring system includes six mooring lines to moor the hull structure to the seabed. Each mooring line includes a 190 mm diameter polyester rope that has a minimum break load of 1,208 tonnes. Each mooring line includes a short length of chain (about 20 meters) located between a corresponding anchor and the polyester rope. A first end of each mooring line is secured to a corresponding column via a corresponding uni-joint. A second end of each mooring line, i.e., the short length of chain, is connected to a corresponding anchor via a uni-joint. A pretension of 400 tonnes is applied to each mooring line. The water depth is 1,000 meters. In the first prophetic example, the hull structure is configured with the following parameters shown in the Table below.

[0051] Figure 5 graphically depicts an illustrative set of curves for the hull structure moored to the seabed when configured according to the Table above that includes a response amplitude operator (RAO) 510 in a heave direction of the offshore floating platform system, a RAO 520 in a pitch and/or roll direction of the offshore floating platform system, and a wave spectrum 530 on the surface of the body of water, according to one or more embodiments. The wave spectrum 530 on the surface of the body of water can have a peak spectral period 531. The RAO 510 in the heave direction of the offshore floating platform system can have a peak response period 511 and a cancellation period 512. The RAO 520 in the pitch and/or roll direction of the offshore floating platform system can have a peak response period 521. In some embodiments, the peak response period 511 in the heave direction of the offshore floating platform system can be less than the peak spectral period 531 of the wave spectrum 530, and the peak response period 521 in the pitch and/or roll direction of the offshore floating platform system can be greater than the peak spectral period 531 of the wave spectrum 530 on the surface of the body of water.

10052] In some embodiments, the dimensions of the hull structure, the mass properties of the hull structure, e.g., mass and radii of gyration, an axial stiffness of the mooring line(s), and/or a pre-tension of the vertical mooring system can be selected such that the motions of the offshore floating platform system in the heave direction and in the pitch and/or roll direction are such that the resonance in the heave direction and/or the resonance in the pitch and/or roll direction can be reduced or eliminated.

[0053] In some embodiments, the cancellation period 512 can be substantially similar to the peak spectral period 531. In some embodiments, substantially similar, when comparing the cancellation period 512 and the peak spectral period 531, means the cancellation period 512 can be within +/- 2.5 seconds, within +/- 2 seconds, within +/- 1.5 seconds, within +/- 1 second, within +/- 0.5 seconds, or within 0.25 seconds of the peak spectral period 531. In some embodiments, the dimensions of the hull structure (including the dimensions of the first column, the second column, the third column, the first pontoon, the second pontoon, and the third pontoon) can be selected such that the cancellation period 512 is substantially similar to the peak spectral period 531. In some embodiments, the dimensions of the hull structure, the axial stiffness of the mooring line(s), and/or the pre-tension of the vertical mooring system can be selected such that the cancellation period 512 is substantially similar to the peak spectral period 531 of the floating offshore platform system.

[0054] As shown in Figure 5, in some embodiments, the RAO 510 in the heave direction of the offshore floating platform system can have a peak response period 511 of about 12 seconds and a cancellation period 512 of about 14 seconds, and the peak spectral period 531 of the wave spectrum 530 on the surface of the body of water can be about 14 seconds. In some embodiments, the peak response period 521 of the RAO 520 in the pitch and/or roll direction of the offshore floating platform system can be about 21 seconds and the peak spectral period 531 of the wave spectrum 530 on the surface of the body of water can be about 14 seconds. [0055] In some embodiments, the offshore floating platform system can be configured to support equipment, for example an offshore wind turbine on the hull structure. In such embodiments, the dimensions of the hull structure, mass properties of the hull structure, e.g., mass and radii of gyration, the axial stiffness of the mooring lines, and/or the pre-tension of the mooring lines in the vertical mooring system can be selected such that the motions of the offshore floating platform are compatible with the allowable design parameters of the equipment.

[0056] Figure 6 graphically depicts an illustrative set of curves in a second prophetic example for another offshore floating platform system that includes another hull structure moored to the seabed via the vertical mooring system that includes a RAO 610 in a heave direction of the offshore floating platform system, a RAO 620 in a pitch and/or roll direction of the offshore floating platform system, and a wave spectrum 630 on the surface of the body of water, according to one or more embodiments. The hull structure includes three columns and three pontoons connecting the columns to one another in a triangular configuration, but the parameters of the hull structure are different than the hull structure in the first prophetic example. The vertical mooring system is the same as the vertical mooring system in the first prophetic example. The wave spectrum 630 on the surface of the body of water can have a peak spectral period 631. The RAO 610 of the offshore floating platform system in the heave direction can have a peak response period 611 and a cancellation period 612. The RAO 620 of the offshore floating platform system in the pitch and/or roll direction can have a peak response period 621. In some embodiments, the peak response period 611 of the offshore floating system in the heave direction and the peak response period 621 of the offshore floating system in the pitch and/or roll direction can each be greater than the peak spectral period 631 of the wave spectrum 630 on the surface of the body of water.

[0057] In some embodiments, the RAO 610 in the heave direction of the offshore floating platform system can have a peak response period 611 of about 18 seconds and the peak spectral period 631 of the wave spectrum 630 can be about 14 seconds. In some embodiments, the cancellation period 612 can be greater than the peak spectral period 631 of the wave spectrum 630. In some embodiments, the dimensions of the hull structure (including the dimensions of the first column, the second column, the third column, the first pontoon, the second pontoon, and the third pontoon), the axial stiffness of the mooring lines, and/or the pretension of the vertically arranged mooring system can be selected such that the cancellation period 612 is greater than to the peak spectral period 631 of the wave spectrum 630 on the surface of the body of water. In some embodiments, the dimensions of the hull structure, the axial stiffness of the mooring lines, and/or the pre-tension of the vertical mooring system can be selected such that the cancellation period 612 and the peak response period 611 in the heave direction can be greater than the peak spectral period 631 of the wave spectrum 630 on the surface of the body of water. In some embodiments, the RAO 620 in the pitch or roll direction of the offshore floating platform system can have a peak response period 621 of about 24 seconds and the peak spectral period 631 of the wave spectrum 630 on the surface of the body of water can be about 14 seconds.

[0058] In some embodiments, the dimensions of the hull structure, the mass properties of the hull structure, e.g., mass and radii of gyration, an axial stiffness of the mooring lines, and/or a pretension of the vertical mooring system can be selected such that the motions of the offshore floating platform system in the heave direction and/or in the pitch and/or roll direction can be such that the resonance in the heave direction, the resonance in the pitch direction, and/or the resonance in the roll direction can be reduced or eliminated. In some embodiments, the offshore floating platform system can be configured to support equipment, e.g., an offshore wind turbine, on the hull structure. In such embodiments, the dimensions of the hull structure, mass properties of the hull structure, the axial stiffness of the mooring lines, and/or the pretension of the mooring lines in the vertical mooring system can be selected such that the motions of the offshore floating platform are compatible with the allowable design parameters of the equipment.

[0059] Figure 7 depicts an isometric view of an illustrative offshore floating platform system 200 similar to the one shown in Figures 2-4 that includes an optional wind turbine generator system 710 disposed on the hull structure 210. In addition to the wind turbine generator system 710, the vertical mooring system 220 the two mooring legs connected to each column being connected to a corresponding anchor 221, 222, or 223 instead of both mooring lines being connected to separate anchors. The wind turbine generator system 710 can include a mast 720 attached or otherwise disposed on the hull structure 210 that can be configured to support a wind turbine generator 730. The wind turbine generator system 710 can also include a plurality of blades 740, three are shown, that react with an incident or oncoming wind to rotate the generator to produce electricity.

[0060] 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 are contemplated 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.

[0061] Various terms have been defined above. To the extent a term used in a claim can be 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 can be not inconsistent with this application and for all jurisdictions in which such incorporation can be permitted.

[0062] 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. An offshore floating platform system, comprising: a hull structure configured to float on a surface of a body of water; an anchor configured to be secured to a seabed; and a mooring line configured to be connected to the hull structure at a first end thereof and to the anchor at a second end thereof, wherein: when the anchor is secured to the seabed and the mooring line is connected to the hull structure and the anchor, the mooring line is substantially vertical and a peak response period of the offshore floating platform system in a pitch or a roll direction is greater than a peak spectral period of a wave spectrum on the surface of the body of water.

2. The system of claim 1, wherein a cancellation period of the offshore floating platform system in a heave direction is substantially equal to the peak spectral period of the wave spectrum on the surface of the body of water.

3. The system of claim 1 or claim 2, wherein a peak response period of the offshore floating platform system in a heave direction is less than the peak spectral period of the wave spectrum on the surface of the body of water.

4. The system of claim 1 or claim 2, wherein a peak response period of the offshore floating platform system in a heave direction is greater than the peak spectral period of the wave spectrum on the surface of the body of water.

5. The system of any one of claims 1 to 4, wherein the peak response period of the offshore floating platform system in the pitch direction and in the roll direction is greater than the peak spectral period of the wave spectrum on the surface of the body of water.

6. The system of any one of claims 1 to 5, wherein the offshore floating platform system further comprises a wind turbine generator system supported by the hull structure, wherein a mass of the hull structure, a geometry of the hull structure, and an axial stiffness of the mooring line are selected such that a motion of the offshore floating platform system in the heave direction, in the roll direction, and in the pitch direction is compatible with the wind turbine generator.

7. The system of any one of claims 1 to 6, wherein a depth of the body of water is greater than 200 meters.

8. The system of any one of claims 1 to 7, wherein the anchor is a first anchor, the mooring line is a first mooring line, and the hull structure comprises a first column, a second column, and a third column, the system further comprising: a second anchor configured to be secured to the seabed; a third anchor configured to be secured to the seabed; a second mooring line; and a third mooring line, wherein: the first mooring line is configured to be connected to the first column at a first end thereof and to the first anchor at a second end thereof, the second mooring line is configured to be connected to the second column at a first end thereof and to the second anchor at a second end thereof, the third mooring line is configured to be connected to the third column at a first end thereof and to the third anchor at a second end thereof, and when the first, the second, and the third anchors are secured to the seabed and the first, the second, and the third mooring lines are connected to the first, the second, and the third columns and the first, the second, and the third anchors, respectively, the first, the second, and the third mooring lines are each substantially vertical.

9. The system of claim 8, wherein the first, the second, and the third columns are configured in a triangular arrangement with respect to one another when viewed in a plan view, and wherein the first, the second, and the third columns are connected to one another via a structural frame.

10. The system of claim 8 or claim 9, wherein the first mooring line, the second mooring line, and the third mooring line are each formed from a synthetic rope and optionally a segment of a wire rope and/or a segment of a chain.

11. The system of claim 10, wherein the synthetic rope is a polyester rope, and wherein the first mooring line, the second mooring line, and the third mooring line are each oriented within 20 degrees of an axis that is vertical with respect the earth.

12. The system of claim 11, wherein a mean or average tension in the first mooring line, a mean or average tension in the second mooring line, and a mean or average tension in the third mooring line all remain substantially equivalent to one another as the hull structure moves in a lateral direction, a surge direction, or a sway direction.

13. The system of any one of claims 8 to 12, further comprising: a fourth mooring line; a fifth mooring line; and a sixth mooring line, wherein: the fourth mooring line is configured to be connected to the first column at a first end thereof and to the first anchor at a second end thereof, the fifth mooring line is configured to be connected to the second column at a first end thereof and to the second anchor at a second end thereof, the sixth mooring line is configured to be connected to the third column at a first end thereof and to the third anchor at a second end thereof, and when the first, the second, and the third anchors are secured to the seabed and the fourth, the fifth, and the sixth mooring lines are connected to the first, the second, and the third columns and the first, the second, and the third anchors, respectively, the first, the second, the third, the fourth, the fifth, and the sixth mooring lines are each substantially vertical.

14. The system of any one of claims 8 to 12, further comprising: a fourth mooring line; a fifth mooring line; a sixth mooring line; a fourth anchor configured be secured to the seabed; a fifth anchor configured to be secured to the seabed; and a sixth anchor configured be to be secured to the seabed, wherein: the fourth mooring line is configured to be connected to the first column at a first end thereof and to the fourth anchor at a second end thereof, the fifth mooring line is configured to be connected to the second column at a first end thereof and to the fifth anchor at a second end thereof, the sixth mooring line is configured to be connected to the third column a first end thereof and to the sixth anchor at a second end thereof, and when the fourth mooring line is connected to the first column and the fourth anchor, the fifth mooring line is connected to the second column and the fifth anchor, and the sixth mooring line is connected to the third column and the sixth anchor, the fourth mooring line, the fifth mooring line and the sixth mooring line are each substantially vertical.

15. The system of claim 13 or claim 14, wherein the fourth mooring line, the fifth mooring line, and the sixth mooring line are each formed from a synthetic rope and optionally a segment of a wire rope and/or a segment of a chain.

16. The system of claim 15, wherein the synthetic rope is a polyester rope, and wherein the first mooring line, the second mooring line, the third mooring line, the fourth mooring line, the fifth mooring line, and the sixth mooring line are each oriented to be within about 20 degrees of an axis that is vertical with respect the earth.

17. The system of any one of claims 13 to 16, wherein a mean or average tension in the fourth mooring line, a mean or average tension in the fifth mooring line, and a mean or average tension in the sixth mooring line all remain substantially equivalent to one another as the hull structure moves in a lateral direction, a surge direction, or a sway direction.

18. A process for mooring an offshore platform, comprising: providing an offshore floating platform system comprising a hull structure configured to float on a surface of a body of water, an anchor configured to be secured to a seabed, and a mooring line configured to be connected to the hull structure and the anchor; securing the anchor to the seabed; and connecting a first end of the mooring line to the hull structure and a second end of the mooring line to the anchor, wherein: when the anchor is secured to the seabed and the mooring line is connected to the hull structure and the anchor, the mooring line is substantially vertical and a peak response period of the offshore floating platform system in a pitch or a roll direction is greater than a peak spectral period of a wave spectrum on the surface of the body of water.

19. The process of claim 18, wherein a peak response period of the offshore floating platform system in a heave direction is less than the peak spectral period of the wave spectrum on the surface of the body of water.

20. The process of claim 18 or claim 19, wherein a cancellation period of the offshore floating platform system is substantially similar to the peak spectral period of the wave spectrum on the surface of the body of water.