WO2019025936A1

WO2019025936A1 - Spread moored buoy and floating production system

Info

Publication number: WO2019025936A1
Application number: PCT/IB2018/055671
Authority: WO
Inventors: Hans Emil OPSAHL; Evert Olaus Grodal
Original assignee: NOV APL Limited
Priority date: 2017-07-31
Filing date: 2018-07-30
Publication date: 2019-02-07

Abstract

An offshore production and storage system includes a spread moored buoy assembly (230) including a riser buoy (234) coupled to a mooring buoy (244), the riser buoy configured to receive and couple to risers, wherein the spread moored buoy assembly is configured to be pre-installed offshore with the risers coupled thereto, and wherein the spread moored buoy assembly is configured to couple to a floating vessel (210) such that the risers fluidicly couple to the floating vessel via the riser buoy.

Description

SPREAD MOORED BUOY AND FLOATING PRODUCTION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[oooi] Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND

[0003] Offshore hydrocarbon drilling and production systems requi re a fluid connection between the subsea production system and the floating production storage and offloading vessel (FPSO) . Upon arrival at the offshore wellsite, the FPSO can be secured to the seabed or dynamically positioned using an onboa rd propulsion system. A mooring system is used to couple the FPSO to the seabed . A spread mooring of the FPSO can ensure position control and a fixed heading of the FPSO at the sea surface. Various mechanisms and apparatus are used to connect the subsea production or manifold system to the FPSO for transferring hydrocarbons. A spread mooring connection will physically connect to the FPSO. A riser connection or hook-up will fluidicly connect the subsea production system to the FPSO. For exa mple, the fluid connection between the subsea system and the FPSO can be used for hydrocarbon production, water injection, gas injection, chemical injection, control lines, and the like.

[0004] Typically, risers and spread mooring are located at the outside of the hull of the FPSO, such as at the port and/or starboard side, and are installed after the FPSO has arrived at the operation wellsite. The spread mooring system is typically installed in four mooring clusters from four locations on the vessel . The mooring lines can be made from chains and neutrally buoyant polyester rope. Pile or suction anchors can be used to fix the moori ng and is typically preinstalled before FPSO arrival . The connection of the mooring lines is done after FPSO arrival at the wellsite with the help of construction vessels and positioning tug boats. After the mooring lines are handed over to the FPSO they a re pre-tensioned using an onboa rd mooring tension system. [0005] A riser balcony at a side of the FPSO is configured to receive and connect to the risers. The risers may be free hanging . The riser balcony typically includes a lower riser balcony, an upper riser balcony, and a pull-in balcony. The lower riser balcony is used to fix the risers laterally to the vessel through a riser bend restrictor. The upper riser balcony is used to fix the risers vertically. The pull-in balcony often includes a skidding rail or similar structure to allow the pull-in device and/or sheave to travel longitudinally to pull in/out each riser. The risers a re pulled in individually with a handover from a flex lay vessel . The commissioning of the wells can start after the risers a re pulled in and connected. The pull-in of risers is performed after all mooring lines are installed .

[0006] Deep waters with large quantities of risers routed directly to the FPSO result in high loads on the side of the FPSO hull . Normally risers are routed to only one side of the hull to allow safe a pproach for supply vessels at the opposite side. In order to maintain stability and buoyancy, extra ballast tanks and/or buoyancy may be required . However, extra ballast or void tanks will reduce the available cargo capacity or increase the required steel material needed . Alternative ways to reduce riser loads include using separate buoyancy solutions to support the riser weights, or reducing the quantity of risers through subsea manifolding . However, both of these options are costly and reduce operational flexibility. In addition to the reduction of cargo capacity in the FPSO, having the risers suspended from the side of the vessel also has a negative impact on the riser fatigue life. The support structures from which the risers hang are away from the vessel center, thereby creating a lever arm on the vessel and amplifying the vessel motions in the risers. The FPSO is subjected to rolling motion from the sea water, and wave slamming motion at the FPSO hull side where the risers a re suspended . These two factors, vessel motion a nd wave slamming, introduce high load on the risers thereby decreasing riser fatigue life.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The subject disclosure is further described in the following detailed description, and the accompanying drawings and schematics of non-limiting embodiments of the subject disclosure. The features depicted in the figures a re not necessarily shown to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form, and some details of elements may not be shown in the interest of clarity and conciseness:

[0008] Fig . 1 is a perspective view of an offshore production and storage system including a spread moored FPSO with a fixed heading ; [0009] Fig. 2 is a top schematic view of the FPSO of Fig. 1, showing an external or side riser balcony for riser hang-off;

[0010] Fig. 3 is a top schematic view of an embodiment of a FPSO including a central or internal riser buoyancy and hang-off system in accordance with principles disclosed herein;

[0011] Fig. 4 is a side schematic view of the FPSO of Fig. 3 with hanging risers;

[0012] Fig. 5 is a bottom schematic view of the FPSO of Figures 3 and 4 showing the central or internal riser hang-off location;

[0013] Fig. 6 is a schematic side view of an embodiment of a pre-installed spread moored buoy assembly in accordance with principles disclosed herein;

[0014] Fig. 7 is a schematic side view of the spread moored buoy assembly of Fig. 6 coupled by ropes to the FPSO;

[0015] Fig. 8 is a schematic side view of the spread moored buoy assembly of Figures 6 and 7 secured in a bay of the FPSO;

[0016] Fig. 9 is a schematic perspective view of the FPSO and spread moored buoy assembly system of Fig. 8;

[0017] Fig. 10 is a top view of the FPSO and spread moored buoy assembly system of Fig. 9;

[0018] Fig. 11 is a cross-section view of the FPSO and spread moored buoy assembly system of Fig. 9;

[0019] Fig. 12 is a bottom perspective view of the FPSO and spread moored buoy assembly system of Fig. 9;

[0020] Figures 13 and 14 are schematic perspective views of the spread moored buoy assembly of Fig. 9 isolated from the FPSO;

[0021] Fig. 15 is a cross-section view of the FPSO and spread moored buoy assembly system of Fig. 11 with the spread moored buoy assembly in a pre-installed, lowered position below the FPSO as schematically shown in Fig. 7;

[0022] Fig. 16 is a cross-section view of the FPSO and spread moored buoy assembly system of Fig. 15 with the spread moored buoy assembly in a lifted or pulled-in and secured position in an internal position in the FPSO as schematically shown in Fig. 8;

[0023] Fig. 17 is a cross-section view of an alternative embodiment of a FPSO and spread moored buoy assembly system with an external spread moored buoy assembly;

[0024] Fig. 18 is a top perspective view of the FPSO and spread moored buoy assembly system of Fig. 17;

[0025] Figures 19 and 20 are schematic perspective views of the external spread moored buoy assembly of Figures 17 and 18 isolated from the FPSO; [0026] Fig. 21 is a cross-section view of the FPSO and spread moored buoy assembly system of Fig. 17 with the spread moored buoy assembly in a pre-installed, lowered position below the FPSO;

[0027] Fig. 22 is a cross-section view of the FPSO and spread moored buoy assembly system of Fig. 21 with the spread moored buoy assembly in a lifted or pulled-in and secured position in an external position adjacent the FPSO;

[0028] Fig. 23 is an enlarged view of a portion of Fig. 16 showing a detailed illustration of the mooring buoy interface in the hull of the FPSO along with the topside manifold system and the pull-in system;

[0029] Fig. 24 is a perspective view of a compensation arm of Fig. 23 showing a connection interface between the mooring buoy and the compensation arm with the mooring buoy, chain fairleads, and mooring lines removed;

[0030] Fig. 25 is an enlarged view of the connection interface shown in cross-section taken at section 25-25 of Fig. 23;

[0031] Fig. 26 is another cross-section view of the connection interface within the mooring buoy and taken at section 26-26 of Fig. 25;

[0032] Fig. 27 is a further cross-section view of the connection interface within the mooring buoy and taken at section 27-27 of Fig. 25;

[0033] Fig. 28 is a different cross-section view of the mooring buoy interface, the topside manifold system, and the pull-in system of Fig. 23;

[0034] Fig. 29 is an enlarged view of the topside manifold and pull-in systems portion of Fig. 28;

[0035] Fig. 30 is an enlarged view of the mooring buoy and pull-in system portion of Fig. 17;

[0036] Fig. 31 is a perspective view of the mooring buoy of Fig. 30;

[0037] Fig. 32 is a side view of the topside manifold system and pull-in system of Figures

15 and 16;

[0038] Fig. 33 is a top view of the topside manifold system and pull-in system of Fig. 32;

[0039] Figures 34 and 35 show another embodiment of a FPSO and spread moored buoy assembly system in similar views as for the FPSO and spread moored buoy assembly system of Figures 15 and 16;

[0040] Fig. 36 is an embodiment of a topside manifold and pull-in system in accordance with principles disclosed herein;

[0041] Fig. 37 is a control schematic of the system of Fig. 36; and

[0042] Fig. 38 is an embodiment of a mooring buoy mounting support system.

[0043] Fig. 39 shows, in an upside-down isometric view, an embodiment of a FPSO;

[0044] Fig. 40 shows, in a side-view; an embodiment of a spread-moored buoy; [0045] Fig. 41 shows, in a cross-sectional view, the spread-moored buoy from Fig. 40 as seen through section B-B;

[0046] Fig. 42 shows, in a cross-sectional view, the spread-moored buoy from Fig. 40 as seen through section C-C;

[0047] Fig. 43 shows, in a top view, the spread-moored buoy from Fig. 40;

[0048] Fig. 44 shows, in a side view, an embodiment of an FPSO assembly;

[0049] Fig. 45 shows, in a side view, an installation stage of the FPSO assembly;

[0050] Figs. 46-48 show, in different cross-sections, another installation stage of the

FPSO assembly;

[0051] Figs. 49-51a, b show, in different cross-sections, a further installation stage of the FPSO assembly;

[0052] Figs. 52-53a-c show, in different cross-sections, an even further installation stage of the FPSO assembly;

[0053] Figs. 54-57 show, in different cross-sections, the final installation stages of the FPSO assembly; and

[0054] Fig. 58 shows, in a longitudinal cross-section, an FPSO assembly with a FPSO according to a second embodiment.

DETAILED DESCRIPTION

[0055] In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals. The drawing figures are not necessarily to scale. Certain features of the disclosed embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present disclosure is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.

[0056] Unless otherwise specified, 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 Any use of any form of the terms "connect", "engage", "couple", "attach", or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.

[0057] Referring to Fig. 1, an offshore production and storage system 100 for producing a subsea well or wells is shown. A subsea production system 102 directs produced fluids, such as subterranean hydrocarbons, from seabed 106 to a series of conduits or risers 114. In other embodiments, the risers 114 can be used for gas injection, water injection, chemical injection, or service lines. In addition to the risers 114, umbilical control lines are commonly needed for control and monitoring of the subsea tree, valves, and flowlines. The risers 114 extend toward sea surface 108 and a storage system 104. The storage system 104 includes a floating vessel or FPSO 110 with a fixed heading. The risers 114 couple to connections 116 in the FPSO 110. The connections 116 are supported by a riser balcony 118 at a side or external portion 120 of the FPSO 110. The riser balcony 118 is the riser hang-off location on the FPSO 110 for the risers 114. The FPSO 110 can be position moored with a fixed heading by a series of mooring clusters 112. As shown in Fig. 2, the riser balcony 118 is located on a side of the FPSO 110 for an external hang-off location for the risers 114.

[0058] Referring next to Fig. 3, a top view of an embodiment of a storage system 200 is shown in accordance with certain principles disclosed herein. An FPSO 210 includes a riser buoyancy and connection, or hang-off, system 218 located centrally or internally of sides 220 of the FPSO 210. In some embodiments, the sides 220 include ballast or void tanks. As used herein, central or internal does not indicate a precisely central location of the FPSO 210, but rather a location moved inwardly from an outermost extent 220 of the FPSO 210 at a perimeter of the FPSO. In Fig. 4, the riser buoyancy and hang-off system 218 is a fluidic connection between the FPSO 210 and a series of subsea risers 214. As shown in Fig. 5, the riser hang-off location at the riser buoyancy and hang-off system 218 is located inwardly of the external perimeter 220 of the FPSO 210.

[0059] Referring now to Fig. 6, the riser buoyancy and hang-off system 218 includes a spread moored buoy (SMB) assembly 230 including a buoy portion 222 and a riser connection or hang-off portion 224, the details of which will be described in greater detail below. The buoy portion 222 may also be referred to as a mooring buoy or a spread moored buoy. Coupled to the buoy portion 222 are mooring lines or clusters 226 and risers 214. In some embodiments, the spread moored buoy assembly 230 can be pre- installed and pre-commissioned at the subsea production system 102 site prior to arrival of the FPSO 210. As shown in Fig. 7, upon arrival of the FPSO 210, the FPSO 210 can be coupled to the spread moored buoy assembly 230 using ropes 228. Referring to Fig. 8, the ropes 228 are used to pull the spread moored buoy assembly 230 into a void, cavity, or bay 232 (as shown in Figures 3 and 5) in the FPSO 210 where, as will be described in greater detail below, the spread moored buoy assembly 230 is secured and fluidicly connected for fluid transfer to the FPSO 210. Mooring clusters 226 couple to the spread moored buoy assembly 230 and are used for position mooring of the spread moored buoy assembly 230. In some embodiments, the mooring clusters 226 are used for position mooring the spread moored buoy assembly 230 and the FPSO 210 after the spread moored buoy assembly 230 is secured in the FPSO 210. In some embodiments, additional mooring clusters 212 can be used for further securing the position mooring of the FPSO 210.

[0060] Referring next to Fig. 9, a perspective view of the FPSO 210 shows the spread moored buoy assembly 230 secured in the FPSO 210 and by the mooring clusters 226. The FPSO 210 also supports a topside manifold system 250 and a lift or pull-in system 270 of the riser buoyancy and hang-off system 218, both of which will be described in greater detail below. A top view of the FPSO 210 in Fig. 10 shows the topside manifold system 250 positioned adjacent the lift or pull-in system 270 which is disposed above mooring buoys (not shown) of the spread moored buoy assembly 230.

[0061] Referring to Fig. 11, a cross-section of Fig. 9 illustrates additional details of the spread moored buoy assembly 230 received and secured in the bay 232. The spread moored buoy assembly 230 includes a riser buoy housing or hull 234, a riser tower 236, riser bend restrictors 238, and riser connectors or hang-off mechanism 240. Compensation arms 242 extend from the riser buoy 234 and support mooring buoys 244. Mooring lines 226 couple to the mooring buoys 244. Mooring buoy hull cavities 246 receive the mooring buoys 244. Referring next to Fig. 12, a bottom perspective view shows the riser buoy 234 captured within the bay 232 with riser bend restrictors 238 exposed. Compensation arms 242 support the mooring buoys 244 within the cavities 246. Referring to Figures 13 and 14, the riser tower 236 extends upward from the riser buoy 234 and terminates in the riser hang-off mechanism 240. Disposed adjacent the riser tower 236 atop the riser buoy 234 are hull fastening points or locks 248 that are part of a central hull locking system. Though two mooring buoys 244 are shown, alternative embodiments may include more than two mooring buoys 244, or a mooring buoy that is part of the riser buoy 234.

[0062] Referring to Fig. 15, the spread moored buoy assembly 230 is in a pre-installed, lower or submerged position secured below the sea surface and the FPSO bay 232 by the mooring lines 226 coupled to the mooring buoys 244. The mooring buoys 244 are supported by the compensation arms 242 and the riser buoy 234. The risers 214 are coupled to the riser bend restrictors 238 which are in turn coupled to the riser tower 236 in the riser buoy 234, terminating in the riser hang-off mechanism 240. Thus, the risers 214 are received by and coupled to the riser buoy 234. Riser sections 260 are disposed in the riser tower 236. In some embodiments, the riser sections 260 cause the risers 214 to be less stiff thereby allowing FPSO hull deformation with limited transfer of loads into the riser buoy 234. The topside manifold system 250 of the FPSO 210 includes a sheave trolley 252. The lift or pull-in system 270 includes pull or lift winches 254 and a spooling device 256. The winches 254 are disposed over the mooring buoy hull cavities 246 such that they can act on the ropes 228 that are coupled to the mooring buoys 244. The ropes 228 can be stored on winch drums for extension or retraction as needed. Disposed in the mooring buoy hull cavities 246 are locking jacks 258.

[0063] Referring to Fig. 16, the spread moored buoy assembly 230 is in a lifted or pulled-in position wherein the spread moored buoy assembly 230 is lifted into and secured in the FPSO bay 232. As will be described more fully below, the lift winches 254 are actuated to pull on the ropes 228 and thereby lift the mooring buoys 244 along with the remainder of the spread moored buoy assembly 230 toward the FPSO 210. A locking system including hull fastening points 248 and locking jacks 258 is used to secure the spread moored buoy assembly 230 in the FPSO bay 232 and the mooring buoy hull cavities 246 of the FPSO 210.

[0064] The spread moored buoy assembly 230 may also be referred to as an internal or hull internally mounted spread moored buoy assembly because it is secured in the bay 232 that is internal to the FPSO 210. Referring now to Figures 17 and 18, in some embodiments the spread moored buoy assembly is external or hull externally mounted, as illustrated by a storage system 300 including a spread moored buoy assembly 330 coupled to a FPSO 310 by a riser buoyancy and hang-off system 318. The assembly 330 may also be referred to as an amidship and center line mounted spread moored riser buoy. The riser buoyancy and hang-off system 318 includes a topside manifold system 350, a lift or pull-in system 370, and the spread moored buoy assembly 330. The spread moored buoy assembly 330 includes a riser buoy housing or hull 334, riser bend restrictors 338, mooring buoy support or compensation arms 342, and mooring buoys 344. The mooring lines 226 couple to the mooring buoys 344 as previously described. The FPSO 310 includes mooring buoy hull cavities 346 to receive the mooring buoys 344.

[0065] Referring to Figures 19 and 20, the spread moored buoy assembly 330 is shown isolated from the FPSO 310. The mooring buoy support arms 342 extend from the riser buoy 334. The riser buoy 334 is kept in place and supported by the mooring buoys 344 through the mooring buoy support arms 342. Disposed atop the riser buoy hull 334 are riser connectors or hang-off mechanism 340 and bumpers 336. The hang-off mechanism 340 is for vertical hang-off and support of risers and control lines. The bumpers 336 function to avoid sideways rotation of the riser buoy 334. After mating the spread moored buoy assembly 330 at the FPSO 310 hull, the risers need to be lifted into and hung off in the FPSO 310 hull. Loads will then be removed from the riser buoy 334, giving the riser buoy 334 positive buoyancy that pre-loads the bumpers 336 into defined locations underneath the FPSO 310 hull. Fine tuning of the preloading can be adjusted by ballasting or deballasting the riser buoy 334.

[0066] Referring to Fig. 21, the spread moored buoy assembly 330 is in a pre-installed, lower or submerged position secured below the sea surface until the FPSO 310 arrives. As shown, the FPSO 310 has arrived and the spread moored buoy assembly 330 is submerged by the mooring lines 226 coupled to the mooring buoys 344. The mooring buoys 344 are coupled to the arms 342 which are coupled to the riser buoy 334, such that the mooring buoys 344 and the arms 342 support the riser buoy 334. The risers 214 are coupled to the riser bend restrictors 338 (Fig. 17) which are in turn coupled to the riser hang-off mechanism 340. The topside manifold system 350 of the FPSO 310 includes sheave trolleys 352. The lift or pull-in system 370 includes pull or lift winches 354 and spooling devices 256. The winches 354 are disposed over the mooring buoy hull cavities 346 such that they can act on ropes 328 that are coupled to the mooring buoys 344.

[0067] Referring to Fig. 22, the spread moored buoy assembly 330 is in a lifted or pulled-in position wherein the spread moored buoy assembly 330 is lifted into a position adjacent an underside 315 of the FPSO 310. As will be described more fully below, the lift winches 354 are actuated to pull on the ropes 328 and thereby lift the mooring buoys 344 along with the remainder of the spread moored buoy assembly 330 toward the FPSO 310. A locking system similar to that previously described is used to secure the spread moored buoy assembly 330 at the underside 315 of the FPSO 310 through the mooring buoys 344. Fluidic connections are established between the FPSO 310 and the riser hang-off mechanism 340 while the bumpers 336 provide a contact buffer or guard between the riser buoy hull 334 and the underside 315 of the FPSO 310. In some embodiments, the risers 214 are lifted by the pull-in winches 354 and a pull-in tool through caissons in the FPSO 310 hull and hung off. Upon hang off of the risers 214, fluid connections can be made up.

[0068] Referring next to Fig. 23, an enlarged cross-section view of the noted portion of Fig. 16 is shown with the riser buoy 234 and the mooring buoy 244 lifted and secured in the bay 232 and the mooring buoy hull cavity 246, respectively. The lift winch 254 of the lift system 270 is coupled to the rope 228 which extends through a passage or channel 255 and is coupled to a coupling and lifting point 249 on the mooring buoy 244. The mooring buoy 244 also includes a locking extension 253 having a locking groove for receiving the locking jacks 258 and retaining a top portion of the mooring buoy 244 in the mooring buoy hull cavity 246. At a bottom portion of the mooring buoy 244 chain fair- leads 227 are mounted in a recess 257 for moveably receiving the mooring lines 226 and thereby securing the bottom portion of the mooring buoy 244. When the mooring buoy 244 is located and secured in the mooring buoy hull cavity 246, a tapered or generally cone-shaped outer surface of the mooring buoy 244 generally mirrors or mates with the tapered or generally cone-shaped inner surface of the mooring buoy hull cavity 246.

[0069] Referring now to Fig. 24, a perspective view of the compensation arm 242 is shown with the mooring buoy 244, the chain fairleads 227, and the mooring lines 226 removed for clarity. A connection interface 283 is disposed at the end of the compensation arm 242 for coupling to the mooring buoy 244. The connection interface 283 includes a mooring buoy mounting bolt 285, a mooring buoy upper guide 287, a mooring buoy lower guide 289, a guide bracket 291, and a lateral bumper or spring 293.

[0070] Referring next to Fig. 25, an enlarged view of the connection interface 283 is shown in cross-section within the mooring buoy 244 and taken at section 25-25 of Fig. 23. A centralizing spacer 279 is disposed adjacent the mooring buoy mounting bolt 285. Also disposed about the mooring buoy mounting bolt 285 is a gelenk bearing 297, with the compensation arm 242 disposed on the opposite side of the gelenk bearing from the mooring buoy mounting bolt 285. Disposed between the mooring buoy upper guide 287 and the guide bracket 291 is a guide bracket glide pad 295. Disposed between the mooring buoy lower guide 289 and the guide bracket 291 is another guide bracket glide pad 295.

[0071] Referring to Fig. 26, another cross-section view is shown of the connection interface 283 within the mooring buoy 244 and taken at section 26-26 of Fig. 25. The mooring buoy mounting bolt 285 is shown within the guide bracket 291. The mooring buoy upper guide 287 and the mooring buoy lower guide 289 bound the guide bracket 291 above and below the guide bracket 291, respectively. Lateral bumpers or springs 293 are disposed on the sides of the guide bracket 291.

[0072] Referring to Fig. 27, a further cross-section view is shown of the connection interface 283 within the mooring buoy 244 and taken at section 27-27 of Fig. 25. The mooring buoy mounting bolt 285 along with the other structures just described with reference to Figures 24-26 provide a rotation point 277 for the mooring buoy 244 with respect to the compensation arm 242. Disposed on each side of the compensation arm 242 below the mooring buoy mounting bolt 285 are rotation limiters 299.

[0073] Referring now to Figures 28 and 29, a different cross-section view from that of Fig. 23 illustrates further details of the components described with respect to Figures 15 and 16. More particularly, the sheave trolley 252, the spooling device 256, and the topside manifold system 250 are shown disposed above the lift winch 254. The lift winch 254 is operably coupled to the rope 228 that extends through the passage 255 to the lift point 249. The locking jacks 258 couple into the locking groove of the locking extension 253. The mooring lines 226 are guided over the chain fairleads 227 and into channels 229 in the mooring buoy 244. The compensation arm 242 is coupled to the mooring buoy 244 so that the mooring buoy 244 can support the riser buoy 234. As shown in Fig. 29, the topside manifold system 250 includes a pig launcher and receiver deck 272, topside piping 274 to be coupled to the risers, a process deck elevation 276 to support the spooling device 256 and the sheave trolley 252, and a skidding rail 282. Just below the lift winch 254 is a main deck elevation 278 and a FPSO recessed deck 280 where risers are presented after the spread moored buoy assembly 230 is lifted into and docked in the FPSO bay 232.

[0074] Referring to Fig. 30, an enlarged view of a portion of Fig. 17 that includes the mooring buoy 344 and the lift system 370 is shown. Many features shown in Fig. 30 are similar to those shown in Figures 23-29, with similar reference numerals used. However, a passage 355 includes a guide roller 365 to receive and guide the rope 328 extending between the mooring lines 226 and the lift winch 354. Further, position mooring lines can be pulled in or out for replacement or re-tensioning. Referring to Fig. 31, the mooring buoy 344 includes an upper tapered or cone-shaped portion 341 including a lift point 349, an intermediate ledge or ridge portion 343, and a lower or recessed tapered or cone-shaped portion 347 for supporting chain fairleads 327.

[0075] Referring to Fig. 28, a side view of the topside manifold system 250 and the lift system 270 is shown. The sheave trolleys 252 are moveably coupled to the skidding rail 282 inside a framework 251, as is also shown in the top view of Fig. 29. The spooling devices 256 sit atop the process deck elevation 276 and the lift winches 254 are disposed just below. The FPSO recessed deck 280 is disposed for riser presentation. In some embodiments, the lift winches 254 can be re-routed to the sheave trolleys 252 that are moveable on the skidding rail 282 and used for riser 214 pull in or out. In some embodiments, two lift systems 270 serve two individual parallel rows of risers 214. In certain embodiments, the lift systems 270 and lift winches 254 can be re-routed to selectively engage and pull in or out the risers or engage and pull in or out the spread moored buoy assembly.

[0076] Referring to Figures 30 and 31, views of an offshore production and storage system 400 are shown that are similar to those of Figures 15 and 16 for system 200. Like components are labeled with like reference numerals and are not discussed in detail here for brevity. However, unlike the spread moored buoy assembly 230, a spread moored buoy assembly 430 does not include mooring buoys 244 and compensation arms 242, or includes separate mooring. Instead, mooring lines 426 and chain fairleads 427 are coupled directly to a riser buoy hull 434, and the system may further include mooring lines 412 coupled to a FPSO 410 (as shown in Fig. 35).

[0077] Referring to Fig. 36, an embodiment of a topside manifold system 650 and a lift system 670 is shown. The lift system 670 includes a lift winch 654. The topside manifold system 650 includes turn down sheave 652, a production header 658, a service header 660, a test header 662, chokes 664, a pig launcher and receiver 666, and a space 656 for topside piping. Referring to Fig. 37, a schematic is shown illustrating an embodiment of pipe routing and pull-in and pull-out procedures for the risers using the same winches as used for lift or pull-in of the riser buoy assemblies as described above.

[0078] Referring to Fig. 38, an embodiment of a mounting support system 700 is shown. Mounting support assemblies 760 are coupled between a FPSO 710 and a riser buoy hull 743. In some embodiments, mounting support assemblies 790 include rollers 794 moveably or rotatably coupled between a roller mount 792 and a roller platform 796. In some embodiments, the connection between compensation arms 742, which are coupled to the riser boy hull 734, and mooring buoys 744 includes a moveable mounting support assembly 770. The moveable mounting support assembly 770 includes a hinged connection 772, a roller assembly 780 having rollers 774, a roller platform 778, and force or biasing members 776 operably coupled to the roller platform.

[0079] It is understood that certain embodiments as disclosed above can be used regardless of the location of the riser connections into the FPSO.

[0080] In operation, and referring to Figures 6 through 8, the spread moored buoy (SMB) assembly 230 is pre-installed and pre-commissioned at the site 102 prior to arrival of and docking or connecting to the FPSO 210. Since the SMB assembly 230 has a shorter lead time than the FPSO 210, the SMB assembly 230 is floated out and pre- installed at the site 102. The SMB assembly 230 is submerged below the sea surface 108 with sufficient clearance to the above, later-arriving FPSO 210. The SMB assembly 230 supports all of the risers 214. The SMB assembly 230 includes an adjustable ballast system which provides flexibility to support a variable number of risers 214. In some embodiments, the number of risers 214 will vary because the subsea and riser installation may not be completed until later in the life of the well. The SMB assembly 230 is ballasted or weighted to a steady state below the sea surface 108 to minimize riser and mooring fatigue. The mooring lines 226 couple to the SMB assembly 230 and are used for position mooring of the SMB assembly 230, to keep the SMB assembly 230 and the risers 214 in place before the FPSO 210 arrives. Consequently, in some embodiments, a complete system including the FPSO, the mooring, and the risers are split into two primary assemblies: the SMB assembly 230 and the FPSO. The FPSO 210 is steered to a position at the sea surface 108 above the submerged SMB assembly 230 as shown in Figures 7 and 15. It is noted that Figures 21 and 34 also show submerged, pre-installed positions of alternative embodiments of the SMB assembly. For ease of description, primary operation will be described with reference to system 200 while many of the same principles apply also to systems 300, 400 except where explicitly noted or where differences are described in detail.

[0081] The pull-in winches 254 are located on the main deck 278 above each of the mooring buoy hull cavities 246 to be used to pull in and dock the SMB assembly 230 into the FPSO 210 hull cavity 232. As shown in Figures 7 and 15, the pull-in ropes 228 are routed through the mooring buoy hull cavities 246 and coupled to the mooring buoys 244 using pennants. Referring to Figures 8 and 16, the pull-in winches 254 are activated to pull or lift on the ropes 228, thus pulling or lifting the mooring buoys 244 and the SMB assembly 230 toward and into the FPSO 210. In this lifted or engaged position of the SMB assembly 230, the riser buoy 234 positioned inside the hull cavity 232 and the mooring buoys 244 are positioned inside the mooring buoy hull cavities 246. The distance traveled by the SMB assembly 230 from the submerged and unin- stalled position shown in Fig. 15 to the lifted or engaged position shown in Fig. 16 may be referred to as an installation or docking stroke.

[0082] The riser buoy 234 can be fastened into the hull cavity 232 using a plurality of hull fastening points or locks 248. In some embodiments, six or more locks are used. The locks 248 can be located adjacent the middle of the FPSO vessel vertical beam as the deflections and stress at such a location normally are less or minimized. When lifted into the hull cavity 232 the riser buoy 234 will be guided by the central locking system including the locks 248. Toward a latter or end portion of the installation or docking stroke, the central locking system and locks 248 will align the riser buoy 234 and riser connectors 240 with the topside piping 274 (Fig. 29). In some embodiments, the central locking system and locks 248 fix or stabilize the SMB assembly 230 in all directions except rotation around the transverse axel. The forward and aft locks can be free to move in horizontal directions to allow alignment before completing the docking stroke, and can be locked in place when the SMB assembly 230 docking stroke is completed, thereby only allowing rotation around the transverse axis. Alternatively, the forward and aft locks can be allowed translation in the longitudinal direction in addition to rotation around the transverse axle if vessel deflections are large. In some embodiments, the central locking system and locks 248 are adjusted in vertical directions using shims or similar devices. In some embodiments, the risers 214 are connected to the riser head arrangement similar to a conventional riser balcony. In further embodiments, the pull-in winches 254 can be re-routed and used for pulling in or out individual risers at a later time. [0083] In the installed position, the SMB assembly 230 positions the risers 214 generally mid-ship and spread out longitudinally, as shown in Figures 3-5, in order to minimize riser motions. Each riser 214 is equipped with the bend restrictor 238 mounted to the underside of the SMB assembly 230 in order to protect each riser 214 from damage due to lateral forces induced by the FPSO vessel's roll and pitch. Thus, the SMB assembly 230 is fixed or installed into the FPSO hull cavity 232 in such a manner that the vessel deflection is not constrained or prohibited by the SMB assembly 230, thereby minimizing stress, weight, and fatigue on the SMB assembly 230. The mooring buoys 244 are located at a distance from each other to ensure proper spread mooring stability of the FPSO 210 when the SMB assembly 230 is installed and fixed in the FPSO 210 hull, and to ensure sufficient spacing for routing of the risers 214.

[0084] Due to the FPSO vessel motions and loading conditions, building tolerances, and temperature deviations the SMB assembly 230, in the installed position of Figures 8, 9, 11, 12, and 16, is allowed certain freedom of motion relative to the FPSO 210 to avoid hull deflections from the FPSO 210 being transferred to the SMB assembly 230. For example, Fig. 38 illustrates the moveable connection principles between mooring buoys 744, a riser buoy 734, and a FPSO 710 hull. The connection of the riser buoy 734 into the mooring buoys 744 allows a limited rotation around the transverse axis at the hinged connection 772 and a limited translation along the longitudinal axis with moveable mounting support assembly 770 to avoid additional stress in a SMB assembly 730 due to vessel deflection in these directions. The limit of rotation and longitudinal translation between the mooring buoy 744 and the riser buoy 734 is achieved by use of bumper or spring arrangements, also referred to as the force or biasing members 776. Vertical translation between the riser buoy 734 and the mooring buoy 744 is fixed as the riser buoy 734 will need to follow the mooring buoy 744 when lifted into the FPSO hull cavity 232.

[0085] The compensation arms 242 connect the riser buoy 234 and the mooring buoys 244 before and after the SMB assembly 230 is installed in the FPSO hull cavity 232. The FPSO 210 will have large displacement due to hogging and sagging when loading and offloading hydrocarbons. The overall displacement of the FPSO 210 hull will create relative displacement between the mooring buoys 244 and the riser buoy 234. The compensation arms 242 and the structural mounting of the compensation arms 242 in the mooring buoys 244 are crucial to avoid high stress in this area. Because of building tolerances and thermal expansion of the FPSO 210 and the SMB assembly 230, flexibility is needed to provide a good fit for the SMB assembly 230 in the FPSO hull cavity 232. [0086] The compensation arm 242 is designed to reduce the vertical loads to be transmitted between the riser buoy 234 and the mooring buoy 244 due to vessel hog and sag deflection. The compensation arm 242 also allows the mooring buoy hull cavity 246 and structural support thereof to be continuous around the mooring buoys 244 to ensure proper load transfer and fit. In some embodiments, the mooring buoys 244 have a fine tolerance fit into the two hull cavities 246 and are preloaded in place with use of the locking jacks 258 in Fig. 23. Such an arrangement will allow the load transfer of the mooring loads to go through a force couple in the upper and lower parts of the mooring buoy cone, such as cone portion 341 in Fig. 31, and into the FPSO hull cavity 232.

[0087] In certain embodiments, additional mechanisms can be incorporated and used in the compensation arms 242. Referring to Figures 24-27, an alternative mounting mechanism allows for lateral movement tolerance between the riser buoy 234 and the mooring buoy 244 to allow for temperature and building tolerances of the SMB assembly 230 and the FPSO 210. The mechanism also reduces the stress transferred to the SMB assembly 230 from deflection (hogging and sagging) of the FPSO 210, as a limited lateral movement and rotation is allowed. The rotation is limited by the rotation limiter 299 shown in Fig. 27. The connection mechanism is shown in isolation in Fig. 24 where the mooring buoy 244 structure, the chain fairleads 227, and the lines or chains 226 have been removed for clarity. Fig. 25 shows a transverse vertical section view of the connection mechanism. Each compensation arm 242 includes a gelenk bearing 297 and is mounted to the two guide brackets 291 on each side of the compensation arm 242 through the mooring buoy mounting bolt 285. The gelenk bearing 297 ensures better load distribution between the two guide brackets 291. The centralizing spacer 279 ensures the correct alignment of the gelenk bearing 297 and the guide brackets 291. Each guide bracket 291 has four guide bracket glide pads 295, where two of the glide pads 295 run in a crevice in the mooring buoy upper guide 287 and the other two guide pads 295 run in a crevice in the mooring buoy lower guide 289. The glide pads 295 allow for the limited longitudinal translation between the mooring buoy 244 and the riser buoy 234. Fig. 26 shows the same connection mechanism from a side section view. The lateral bumper or spring 293 restricts the longitudinal translation of the mooring buoy 244 and the connection mechanism as they interact with the guide bracket 291 on each side. In certain embodiments, the nominal tolerance is illustrated between the guide bracket 291 and the lateral bumper or spring 293 on each side. Fig. 27 shows a different side section view of the connection mechanism. The rotation limiters 299 are illustrated at each side of the compensation arm 242 to limit the rotation of the mooring buoy 244 around the rotation point 277. [0088] In alternative embodiments, the mounting of the compensation arms can be slightly different. For example, the compensation arms 342 on the externally mounted SMB assembly 330 of Figures 17-22 can include a laterally fixed mounting in one of the compensation arm connections to the mooring buoy 344, as a fixation of the riser buoy 334 into the hull. The second or other compensation arm 342 can be arranged and coupled as previously described.

[0089] Referring to Figures 28-31, details of the mooring buoys 244, 344 are shown. For ease of description, details of both the mooring buoy 244 of Figures 28 and 29 and the mooring buoy 344 of Figures 30 and 31 will be referenced interchangeably since they share many of the same components. Differences will be noted. The mooring buoy 244 includes the chain fairleads 227, the mooring lines 226, the lifting point 249, the locking extension or groove 253, and the two hinged or rotatable connections 283 (Fig. 24), 772 (Fig. 38) to the riser buoy 234. The mooring buoy 344 has a circular, cone shaped portion 341 to allow proper guiding and fit into the FPSO hull cavity 246. When performing the landing or docking stroke of the SMB assembly 230 into the FPSO 210 hull, the mooring buoy cone 341 will matingly interface with the FPSO hull cavity 246 leaving clearance between the riser buoy 234 and the FPSO hull cavity 246. The locking groove 253 allows fixation of the mooring buoy 244 to the FPSO hull cavity 246 through the locking jacks 258. In some embodiments, both mooring buoys 244 include anti-rotation keys in the top to ensure correct orientation during installation and prevent rotation due to mooring loads relative to the FPSO 210. The chain fairleads 227 is hinged parallel, or close to concentric to the penetrations 229 for the mooring lines 226 going through the mooring buoys 244. The number and size of the mooring lines 226 is governed by the mooring loads on the vessel. The mooring line 226 can be locked after exiting the fairlead 227 in a chain stopper or be suspended in chain flapper locks on top of the mooring buoy 244, 344.

[0090] In some embodiments, the mooring lines 226 are installed before the risers 214 are pulled into the SMB assembly 230 with help of a construction vessel or similar. The SMB assembly 230 and the mooring buoys 244 can, in this embodiment, be above the sea surface 108 to allow easy access at vessel light ballast draft. The mooring buoys 244 have lift points 249 on top to allow connection to the pull in/out winches 254. The mooring buoys 244 have approximately negative buoyancy in seawater to ensure good stability of the SMB assembly 230 before the risers 214 and the mooring lines 226 are installed. To ensure the correct buoyancy of the mooring buoys 244, the buoyancy compartments can be filled with a buoyancy material. Other buoyancy compartments may be open to the environment to obtain a variable buoyancy, which increases with decreasing depth, or may contain compressed air cylinders, for example. The top of the mooring buoy 244 hull compartment can be flooded or dry depending on vessel draft.

[0091] The riser buoy 234 may also include buoyancy compartments to carry the weight of the SMB assembly 230, the risers 214, and the mooring lines 226. Void spaces or buoyancy material can be used to carry the weight of the SMB assembly 230 without the risers 214 and the mooring lines 226. The buoyancy compartments may be split into several compartments to allow adjustment and stabilization of the SMB assembly 230 to accommodate for the different number and layout of the risers 214 and the mooring lines 226. Adjustment of buoyancy can be accomplished through lines and valves in the top of the riser tower 236 or through separate side mounted WROV panels on the riser tower 236. The buoyancy compartments can be embedded in the FPSO hull when installed to minimize additional drag forces. The buoyancy compartments may be open to the environment to obtain a variable buoyancy, which increases with decreasing depth, or may contain compressed air cylinders, for example.

[0092] Referring to Figures 13-16, the top of the riser tower 236 is used as a hang off structure for the risers 214 so that the risers 214 can be presented for connection to the topside above the water line. The risers 214 are supported on a vertically adjustable riser hang-off mechanism 240 on top of a caisson stretching through the SMB assembly 230 where the bend restrictors 238 are mounted. The riser tower 236 will be above water when the SMB assembly 230 completes docking into the FPSO 210 hull. The additional weight of the structure and the risers 214 above water is carried by the pull in/out winches 254 in some embodiments, or by increasing the SMB assembly 230 buoyancy in other embodiments. The riser tower 236 is sectioned with riser sections 260 to minimize the stress build up in the structure of the SMB assembly 230 due to the FPSO 210 deflections.

[0093] In some embodiments, the buoy locking system 248 is a structural part of the riser tower 236 to support the variable dynamic loads from the risers 214 and vessel deflection, and to minimize the movement of the riser connections relative to the topside. The buoy locking system 248 may also be needed to support the lateral loads from the risers 214. Such lateral loads may also be transferred through the bend restrictors 238 due to vessel roll and pitch and SMB assembly 230 dynamic loads. Alternatively, the SMB assembly 230 can be partly deballasted after installation ensuring that the vertical load in the locking system 248 will be larger than the uplift force created through the lateral forces from the risers 214 and the SMB assembly 230 dynamic loads.

[0094] Referring to Figures 28, 29, 32, and 33, the process deck 276 may be, for example, located five meters above the main deck 278, and access to process topside is needed from the process deck 276. Above the process deck 276, space is needed for piping and headers between topside modules and riser/umbilical connections. The pig launcher and receiver deck 272 is located at the top deck as a larger width is normally required in this area for pig handling and launcher/receiver systems. Two pull in/out winches 254 on the main deck 278 can be rerouted through a removable spooling device 256 and a sheave trolley 252 on the process deck 276 elevation to able pull in/out individual risers after the SMB assembly 230 docking is completed.

[0095] The pull in system can be arranged in two parallel systems to allow pull in of risers in two rows. Two longitudinal rows of the risers 214 can be pulled in utilizing the forward and aft pull in/out winches 254, respectively. The sheave trolleys 252 can be moved along the skidding rail 282 using winches or tractor systems. The sheave trolleys 252 can be mechanically locked into the skidding rails 282 prior to pull in/out. The pull in/out winch 254 can also be rerouted to the mooring buoy hull cavity 246 to allow pull in/out of the mooring lines 226 in single fall. Tensioning of the mooring lines 226 can also be done using the pull in/out winch 254, or in some embodiments, with a separate linear jacking or wildcat system.

[0096] After docking of the SMB assembly 230, the risers 214 are presented above water in the FPSO 210 full loaded draft, but below the main deck 278 to minimize the weight lifted out of water and to provide space to ease the topside piping 274, valve placement, and riser lifting arrangement. Hook up of the risers 214 and the topside piping 274 is done with help of the spool piece or similar equipment after the SMB assembly 230 docking is complete. Fine adjustment of the riser 214 elevation before fitting the topside piping spool can be done using the hang-off mechanism 240. The topside piping 274, which is to be coupled with the risers 214, can be routed outside the process deck 276 to allow access in the center and minimize the width requirements of the process deck 276 and allow more space for topside modules.

[0097] In some embodiments, a different mounting location of the SMB assembly 230 (or other SMB assemblies as described above) in the FPSO 210 hull would still allow the benefit of pre-installing the SMB assembly 230 at the operation site (field), thus reducing the overall schedule. A different mounting location could be applicable for an FPSO where riser fatigue is not an issue due to, for example, less vessel motions, shorter operational life, or allowing the FPSO to disconnect from field at certain weather conditions.

[0098] In some embodiments, a different shape of the SMB assembly 230 could also be beneficial in certain operational scenarios or projects. Referring to Figures 21 and 22, the SMB assembly 330 includes riser buoyancy kept below the FPSO 310 after the SMB assembly 330 is docked. Such an arrangement can be beneficial as less cut-out or hull cavity in the FPSO hull is required than in the FPSO 210 as described above, thus improving the structural integrity of the FPSO. The SMB assembly 330 can be pre- installed at operational field as previously described. The riser buoy 334 is shown as submerged pressure vessels. Alternatively, the buoyancy compartments may be open to the environment to obtain a variable buoyancy, which increases with decreasing depth, or may contain compressed air cylinders, for example. The risers 214 are hanged off in the riser buoy 334 as described in earlier embodiments, but will be lifted into the FPSO 310 through caissons and hanged off after the SMB assembly 330 has been docked into the FPSO 310 as seen in Fig. 22. The risers 214 will be lifted up and down using an elevator from the SMB assembly 330 using the pull in/out winches rerouted for riser pull in/out as described in previous embodiments. The risers 214 will, after they are hanged off in the FPSO 310 hull, still be routed through the riser buoy 334 where the bend restrictors will be mounted. The pull in/out of the SMB assembly 330 and the mooring buoys 344 is similar to embodiment described above. The riser buoy 334 can be ballasted or deballasted to achieve a preloading between the FPSO 310 hull and the riser buoy bumper 336 to support the lateral loads from the risers 214 at FPSO 310 roll.

[0099] Figures 34 and 35 show an embodiment where a smaller and shorter SMB assembly 430 does not include mooring buoys, such as mooring buoys 244, 344. The SMB assembly 430 can be pre-installed at operational field as previously described. The mooring of a FPSO 410 is a combination between conventional spread mooring 412 and mooring lines 426 from the SMB assembly 430. The mooring lines 412 from the FPSO 410 in addition to the mooring lines 426 from the SMB assembly 430 are needed to avoid large FPSO 410 yaw motions when the longitudinal spacing of the SMB assembly 430 mooring lines 426 are too short. The needed FPSO 410 mooring lines 412 can be transferred from the SMB assembly 430 to the FPSO 410 after docking of the SMB assembly 430. Alternatively, the FPSO mooring lines 412 can be installed in a conventional way with the help of anchor handling and construction vessels.

[00100] Risers 414 and mooring are hung off in the SMB assembly 430 prior to docking into the FPSO 410. The docking of the SMB assembly 430 is performed similar to earlier described embodiments utilizing two pull in/out winches. The pull in/out winches will be connected directly in each end of a riser buoy 434. After docking, the risers 414 can be directly coupled to the topside piping 274 or lifted to a higher hang off elevation in the FPSO 410 hull before hook up. Pull in/out of individual risers 414 can be done similar to what is described in earlier embodiments. The riser buoy 434 is locked into the FPSO 410 hull similar to that shown in previous figures. [ooioi] The SMB assemblies described above also allow for easy disconnect from the FPSO in the event which would require the FPSO to leave the site. In some embodiments, the disconnect procedure is the opposite of the disclosed connection procedures.

[00102] In some embodiments, an offshore production and storage system includes a 5 spread moored buoy assembly including a riser buoy coupled to a mooring buoy, the riser buoy configured to receive and couple to risers, wherein the spread moored buoy assembly is configured to be pre-installed offshore with the risers coupled thereto, and wherein the spread moored buoy assembly is configured to couple to a floating vessel such that the risers fluidicly couple to the floating vessel via the riser buoy. The moor- i o ing buoy may be configured to couple to the floating vessel apart from the riser buoy coupling and the riser fluidic coupling. The riser buoy may couple into an internal cavity of the floating vessel. The offshore production and storage system may further include two mooring buoys coupled to riser buoy by compensation arms, wherein the riser buoy and the risers couple into an internal cavity of the floating vessel and the mooring buoys

15 couple into mooring buoy hull cavities of the floating vessel. The spread moored buoy assembly is configured to couple to an external and underside surface of the floating vessel .

[00103] In some embodiments, an offshore production and storage system includes a spread moored buoy assembly including a riser buoy and two mooring buoys coupled

20 to the riser buoy, risers coupled to the riser buoy, and a floating vessel configured to receive the riser buoy and thereby fluidicly couple to the risers, and configured to receive the mooring buoys separately from the riser buoy and the risers. In some embodiments, an offshore production and storage system includes a spread moored buoy assembly coupled to risers, the spread moored buoy assembly configured to be pre-

25 installed offshore with the risers coupled thereto and a fixed heading floating vessel configured to receive and fix the spread moored buoy assembly to the floating vessel FPSO

[00104] In the following, reference is made to Figs. 39-58, where the reference numeral 1 will be used to denote a FPSO vessel according to a first aspect of the disclosure, while the reference

30 numerals 10 and 90 will be denoting a spread-moored buoy (SMB) according to a second aspect of the disclosure and a FPSO assembly according to a third aspect of the disclosure, respectively.

[00105] Any reference to prepositions, such as "over", "under", "in front of, "behind" etc., or directions, such as "up", "down", "forward", "backward" etc., will refer to the normal orientation and direction of the features in the drawings in their normal position of use.

35 [00106] The buoy will in the following mostly be referred to as a spread-moored buoy (SMB). For most applications, the buoy will be a SMB but in sheltered waters the buoy may stay positioned even without mooring lines or any mooring system to keep it positioned. The risers may then have sufficient capacity to keep the buoy on location without mooring lines. The configuration of the buoy and the FPSO will then remain the same, except that all the mooring of the FPSO assembly after mating will be provided by the FPSO mooring system as will be explained below.

[00107] Fig. 39 shows, in an upside-down isometric view, a FPSO vessel 1 according to the disclosure. The FPSO 1 has a recess, in the form of a trunk 2, extending from the stern 4 of the FPSO, along an axial/longitudinal centreline C inside the hull 3 of the FPSO 1 and to a position substantially amidship 8. In an alternative, not shown embodiment, the trunk 2 may be provided inside the hull 3 of the FPSO but off the centreline. In yet an alternative, not shown embodiment, the trunk 2 may be extending from the bow 5 of the FPSO 1 and into the inside of the hull 3. The trunk 2 may even, in alternative, not shown embodiments, be extending from the sides of the FPSO 1 and into a docking area inside the hull 3. In that regard it should be noted that the seaworthiness of a FPSO 1 in transit is of little importance, as the FPSO 1 will typically be moored and stationary at the wellsite for several years, sometimes for decades. The shown FPSO 1 includes a plurality of riser reception pipes 12, the riser reception pipes 12 constituting a part of a riser reception unit on the FPSO 1 . The trunk 2 allows for the reception of the spread-moored buoy 10, as shown in in Fig. 40, and as will be described in further detail below with reference to the drawings in the following figures. The FPSO 1 is moored by means of plurality of mooring lines 14 to the seabed 21 , as shown e.g. in Fig. 44. The mooring lines 14 are connected to the FPSO 1 at the stern 4 and bow 5 both at the starboard side 16 and port side 18 thereof, in a spread-mooring arrangement. The trunk 2 is closable by means of a hatch 82, which may be beneficial for protecting equipment provided in the trunk 2 from waves, wind etc. The hatch 82 may, in alternative, not shown embodiments, be located near the bow 5 or one the sides 16, 18 of the FPSO 1 .

[00108] The trunk 2 may, as indicated in Fig. 54, be formed with low and narrow aft portion and a wider and deeper portion forward for docking area for the SMB 10, the docking area incorporating equipment for warping, locking and flow line make-up etc., as will be explained in the following. In this embodiment, the SMB 10 may need to be brought to a deeper draft in order to pass the low portion of the trunk 1 , before docking.

[00109] Reference is now made to Figs. 40-43, showing the spread-moored buoy (SMB) 10 floating in the sea 20. Figs. 40 and 43 show the SMB 10 in a side and top view, respectively, while Figs. 41 and 42 show cross-sections B-B and C-C, respectively, as indicated in Fig. 40. The distance D1 between the sea surface 22 and the bottom 24 of the SMB 10 represents the draft of the SMB 10 in the shown position. A plurality of risers 26 extend from a not shown well head, pipe line or subsea manifold and up to the SMB 10. Each riser 26 enters the bottom 24 of the SMB via a riser bend restrictor/stiffener 28 protecting the risers 26 from static loads that could otherwise have led to bending and buckling during installation and operation. From the bend restrictors 28, the risers 26 extend through guide pipes/caissons 30 in the SMB body, as shown in Figs. 41 and 42, and therein protected through the splash zone to be hung off on the upper surface/weather deck 32 of the SMB 10 in a riser hang off 34 with end fittings 33, flanges for isolation valves 35 and riser isolation valves 36 connected thereto shown extending above the hang-offs. The isolation valves 36, together with emergency shut down valves 37, as shown in Fig. 55, may be important for safety if the risers 26 are already connected to live subsea wells. The risers 26 are hung off in two parallel rows on the SMB 10. A plurality of fenders 38 are provided on each side of the SMB 10 for gentle docking in the trunk 2 inside the hull 3 of the FPSO 1 as will be explained below with reference to the following drawings. The SMB 10 is provided with locking means 40, here shown in the form of locking dogs/arms 43 that are extendible to engage with complementary fitting cradles 42, see e.g. Figs. 50 and 51 , in the trunk 2 of the FPSO 1 as will explained below. The cradles 42 may be lined with an elastomer sheet to reduce the effects of the impacts during the docking/mating operations of the SMB 10 within the hull 3 of the FPSO 1 . The two bodies of the locking means 40 will have different motion characteristics during the docking sequence, and means for reducing the load response caused by the impacts during such mating may be beneficial. The locking arms 43 com- plementary fit with the cradles 42. The locking means 40 includes a stationary sleeve part 41 and a linearly extendable arm part 43 as will be described in further detail below. In alternative, not shown embodiment, the locking dogs 43 may be mounted to the FPSO 1 while the cradles 42 are located on the SMB 10. The SMB 10 is moored to the seabed 21 , as shown in Figs. 43 and 44, by a plurality of SMB mooring lines 44 connected to the aft 46 and front 48 of the SMB 10 on both starboard side 50 and port side 52 thereof, in a spread mooring arrangement, hence the name "spread- moored buoy". Mooring fairleads 54, with lower swivelling members 56 and vertical stationary members 58, extending along the height of the hull of the SMB 10 acting a hawse pipes and supporting the lower swivelling members 56, guide the mooring lines 44 from the sea to the SMB weather deck 32, where in the mooring lines 44 are hung off in mooring line hang-offs 60, here shown in the form of chain stoppers. The vertical, stationary parts 58 of the fairleads 54 are protected by means of vertically extending fenders 62. To tension the mooring of the SMB 10, prior to arrival of the FPSO 1 , the SMB 10 mooring lines 44 on the SMB 10 may be tensioned by a means of a not shown installation vessel carrying the necessary winches and equipment to establish the desired tension, as will be understood by a person skilled in the art. The installation vessel will normally be the same vessel installing the risers 26 and connecting them to the SMB 10. This full installation process does not require the presence of a FPSO. In an alternative embodiment, as indicated in Fig. 55, the SMB 10 itself may be provided with one or more mooring line tensioning members, here in the form of linear winches 64, adapted to tension the mooring lines 44 to the desired tension. The draft D1 of the SMB 10 indicated in Figs. 40-42 is representative for the typi- cal draft of a fully loaded, moored SMB 10 waiting for the FPSO 1 to arrive. The SMB 10 is during and after installation, before connection to a FPSO 1 , made as a barge for surface operations. However, after connection and installation to the FPSO 1 , the SMB 10 is designed to be able to be fully submerged when the FPSO 1 shifts to a fully loaded draft, as will be explained below.

[00110] In the following, with reference to Figs. 44 - 58, the FPSO 1 and SMB 10 will be shown together, both before, during and after connection and installation, and the combined FPSO 1 and SMB 10 will, as already described herein, be referred to as a FPSO assembly 90.

[00111] Fig. 44 shows, in small scale, the FPSO assembly 90, including the FPSO 1 and the SMB 10, installed and spread-moored to the seabed 21 by means of the FPSO mooring lines 14 and the SMB mooring lines 44. In another, not shown embodiment it is envisioned that the SMB 10 may carry a larger part or even all of the mooring, implying that the FPSO 1 , when mechanically con- nected to the SMB 10, may not need to be moored, potentially simplifying the process of connecting the FPSO assembly 90. In still another, not shown embodiment, the mooring lines 44 suspended in the SMB 10 may be idle or dismounted, leaving all the station keeping duties to the mooring system mounted onto the hull 3 of the FPSO 1

[00112] The mooring system for the SMB 10 disclosed herein is just one exemplary embodiment out of a variety of different, possible mooring systems, as will be understood by a person skilled in the art. The SMB 10 may be provided with mooring suspension means as is well known for ordinary moored vessels including mooring systems connected by means of lugs to the SMB. Other alternative mooring systems may include dual axis supported chain stoppers located at the bilge [00113] In the following, with reference to Figs. 45-58, different stages of the process of connecting and installing the FPSO assembly 90 are shown. In the various stages, different steps where the SMB 10 and FPSO 1 are moved relative to each other are involved; first horizontally by hauling/warping one relative to the other in order to dock the SMB 10 in the trunk 2 inside the hull 3 of the FPSO 1 , and then subsequently vertically by ballasting or de-ballasting one relative to the other in order to make up the mechanical connection between the FPSO 1 and SMB 10. It should be noted that in the method according to the disclosure, it is sufficient that there is relative movement between the FPSO 1 and SMB 10, and that instead of hauling the FPSO 1 in over the SMB 10, the SMB 10 may instead be hauled into the trunk 2 of the FPSO 1 . Similarly, steps relating to ballasting and de-ballasting of the SMB 10 could equally well be achieved by de-ballasting and ballasting, respectively, of the FPSO 1 .

[00114] Fig. 45 shows the SMB 10 moored and positioned at its final position, while the FPSO 1 is located with its stern 4 adjacent the front 48 of the SMB 10. The FPSO 1 may now be hauled into a position over the SMB 10 by increasing the tension in the mooring lines 14 connected to the stern 4 of the FPSO 1 , while simultaneously reducing the tension in the mooring lines 14 connected to the bow 5 of the FPSO, as will be understood by a person skilled in the art. In an alternative, not shown embodiment, tug boats may be used in addition or as an alternative to haul the FPSO 1 into position over the SMB 10. Not shown propulsion equipment on the FPSO 1 may also be used to assist in the hauling process.

[00115] Fig. 46 shows a longitudinal cross-section through the FPSO assembly 90 in a stage where the SMB 10 is half-way into the trunk 2 within the hull 3 of the FPSO 1 . The relative movement of the FPSO 1 to SMB 10 is, in the shown embodiment, enabled by re-tensioning of the FPSO mooring lines 14 as described above. During hauling/warping, both the FPSO 1 and the SMB 10 is at a light draft, as will be explained in further detail below

[00116] Fig. 47 shows cross-sections through sections C-C and D-D from Fig. 46 in the upper and lower parts of the figure, respectively. Section C-C in the upper part of the figure clearly shows the SMB 10 in the trunk 2 of the FPSO 1 , while the SMB 10 has not yet reached section D-D, hence the seemingly empty trunk 2. In the shown embodiment, the FPSO 1 is at light ship draft and the SMB 10 is at a deep draft when moving through the aft portion of the trunk 2 for minimum height of the trunk 2. Similarly, Fig. 48 shows cross-sections through sections F-F and G-G from Fig. 46 in the upper and lower parts of the figure, respectively. Section C-C is taken vertically through the front 48 of the SMB 10 just rear of the amidship portion 8 of the FPSO 1 . Section G-G is taken substantially amidship of the SMB 10 towards the stern 4 of the FPSO 1 . Section D-D is taken just in front of the amidship portion 8 of the FPSO 1 , while F-F is taken in front of the trunk 2, between the bow 5 and the amidship portion 8 of the FPSO 1 . As can be seen clearly in sections C-C and G-G, the locking arms 43 of the locking means 40 are in their retracted position, whereby the FPSO 1 can be moved freely, linearly relative to the SMB 10. Fig. 46 and sections D-D and F-F in Figs. 47- 48 also show riser connections in the form of riser reception pipes 12 on the FPSO 1 . Each reception pipe 12 extends from the trunk 2 through an upper part of the trunk 23 in the hull 3 and to the deck 1 1 of the FPSO 1 . The SMB 10 has not yet been mechanically connected to the FPSO 1 and no installation of risers 26 has been made. Process modules 66, to which the riser reception pipes 12 fluidly connect (not shown), are only schematically indicated on deck 1 1 of the FPSO. Each riser reception pipe 12 is provided with its own valve 68, defining the top of the riser reception pipe 12. Winches 70, as shown in sections D-D and F-F, provided on deck 1 1 of the FPSO 1 may be used to tension the SMB mooring lines 44 if needed.

[00117] Fig. 46 shows a warping line 75 extending longitudinally from the SMB to either a winch 70 on deck 1 1 via the hawse pipe 78 (Fig. 48) or preferably from a smaller winch in the forward end of the trunk 2 to the SMB 10. A corresponding warping line from the aft portion of the wide portion of the trunk to the SMB is established as the SMB is entering the trunk. These two warping lines will keep the relative position of the two floating bodies in control relative to one another.

[00118] Alternatively, as mentioned previously and shown in Fig. 55, the SMB 10 may carry its own winch 64 for the tensioning up its mooring lines. Winches 71 are connected to the FPSO mooring lines 14 for tensioning of the mooring lines 14. The mooring lines 14 extend from the seabed 21 , as shown in Fig. 44, to deck 11 of the FPSO 1 through fairleads 67, which are of similar construction as the fairleads 54 on the SMB 10, discussed in relation to Figs. 41 and 42 above. Chain stoppers 69 are used to hang-off the FPSO mooring lines 14 on deck. 1 1 . The winches 71 will normally be used in order to haul/warp the FPSO 1 in over the SMB 1 in the installation process. A winch 72, adapted to pull in risers 26 by means of a pull-in rope 73, is provided on a carriage 74, linearly movable on rails 76 extending longitudinally in the upper trunk 23. This carriage 74 may thus be placed at any longitudinal position over the risers 26 once the SMB 10 is installed to make up con- nection with any of the risers 26. The process of pulling in risers 26 in order to make up the connection between the risers 26, hung off at the SMB 10, and the riser receptions pipes 12 will be described in further detail below. Section F-F of Fig. 48 further shows hawse pipes 78 extending through the hull 3 of the FPSO 1 . When installed, the mooring lines 44 from the SMB 10 may extend through these hawse pipes 78 for connection to the tensioning winches 70 on deck 1 1 of the FPSO. The cradles 42, into which the locking arms 43 will be extending to make up the mechanical connections between the SMB 10 and FPSO 1 , is e.g. shown in sections C-C, D-D and F-F of Figs. 47-48. The process of making the mechanical connection will be described in further detail below.

[00119] Reference is now made to Figs. 49-51 a, b, where Fig. 49 shows the SMB 10 docked into the trunk 2 of the FPSO 1 in the final horizontal position of the FPSO 1 , while Fig. 50 shows the cross-sections F-F and D-D from Fig. 49, and Fig. 51 a shows the cross-sections G-G from Fig. 49 and the detail M from the cross-section G-G. The SMB 10 is still at the same draft D1 as shown in Figs. 40-42, where the waterline/sea surface 22 is at the level of the fenders 38. In this relatively light draft D1 of the SMB 10, the locking arms 43 are at a higher vertical position than the corresponding cradles 42 in the trunk 2 of the FPSO 1 , and may be extended horizontally into a vertical position above the cradles 42, as best seen in Fig. 51 a and in particular in detail M. Each locking arm 43 is formed with an inclined end/engagement portion 45 adapted to be received by a complementary inclined receiving portion 47 in the cradle 43 in order to position the SMB 10 sideways relative to the FPSO 1 . The extension of the arms 43 is actuated by means of not shown linear actuators, which may be operated hydraulically, pneumatically, electrically or manually- mechanically as will be understood by a person skilled in the art. In the shown position, the SMB 10 is now ready to be mechanically connected to the FPSO 1 .

[00120] Figs. 52-53a-c show the SMB 10 after it has been mechanically connected to the FPSO 1 . Fig. 52 shows a longitudinal cross-section through the FPSO assembly 90, Fig. 53a shows a cross- section G-G from Fig. 52 and a detail M from G-G, while Fig. 53b shows the cross-section X-X from Fig. 53a. The actual connection is made by changing the relative vertical position between the SMB 10 and FPSO 1 , here by ballasting the SMB 10 to a deeper draft D2, where the waterline 22 is closer to the weather deck 32 of the SMB 10.

[00121] Referring again to Figs. 51 a, b, the vertical clearance/distance between the locking arms 43 and the cradles 32 is reduced as ballast water is pumped into the SMB 10 until the underside 83 of the arm 43 comes into contact with the liner 84 in bottom of the cradle 42. The inclined portion 45 of the arm 43 eventually ensures centralizing effects on the SMB 10 as it comes into engagement with the complementary inclined receiving portion 47 in the cradle 42, whereby the remaining portion of the difference between submerged buoyancy of the SMB 10 and the weight of the SMB 10 with all mooring and riser loads carried by it becomes carried by the FPSO 1 . Section X-X in Fig. 51 b similarly shows the principles for longitudinal positioning of the SMB 10 versus the FPSO 1 , wherein the inclined sidewalls of the cradle 42, provided with liner 85, ensure gentle docking and longitudinal positioning of the arms 43 into the cradles 42.

[00122] A large draft during the connect-up operation of the SMB 10 to the FPSO 1 may be beneficial for minimizing the reserve buoyancy of the SMB 10. (The reserve buoyancy is the difference between the SMB 10 total buoyancy less the total weights and loads on the SMB 10.) The locking means 40 will thus be exposed to less loads when the FPSO 1 is at loaded drafts and the SMB 10 is fully submerged. The most beneficial reserve buoyancy will be the one resulting in net load reaction between the locking means 40 and the cradle 42 just a little larger than the double amplitude of the dynamic vertical loads between the SMB 10 and the FPSO 1 . Then alternative loads passing zero in the locking device 40 connections represented by Fig. 53a, b is avoided.

[00123] The locking means 40 will be subjected to a static force corresponding with the reserve buoyancy at the draft at connect-up of the SMB barge 10 to the FPSO vessel 1 hull 3. This draft will in most cases correspond with a reserve buoyancy which will be too small for a free-floating barge in open sea. [00124] Ballast water is filled into the ballast water tanks in the SMB 10 sufficiently to keep it calmly in the cradles 42. The docking operation is completed by engaging uplift preventers 86 to the cradle 42, by means of not shown fixing means, as indicated in the cross-section shown in Fig. 53c [00125] The design of the SMB 10 and the FPSO 1 may, as mentioned above, be inversely de- signed so that the FPSO 1 play the active role in the shifting of the relative draft between the SMB 10 and the FPSO 1 during the mating operation, implying that when the vertical distance/clearance between the locking dogs 43 and the cradles 42 are to be closed/reduced, the FPSO 1 may be de- ballasted to a lighter draft, in contrast to the shown embodiment where the SMB 10 is ballasted to a heavier draft.

[00126] The connection of the risers 26 to the riser connection pipes 12 may then commence as well as adjustment of the tension in mooring lines suspended by the SMB 10

[00127] Reference is now made to Figs. 54-57, showing the process of connecting the risers 26 on the SMB 10 to the riser reception pipes 12 on the FPSO 1 . The FPSO 1 is shown with two different drafts in the figures, a first draft D3 indicating the relatively light draft maintained by the FPSO 1 during the whole installation and connection phase, and a second, deeper draft D4 which will be the draft of the FPSO assembly 90 after installation and connection has been finalized. When the FPSO assembly 90 is in the final, deep draft D4, the SMB 10 will be fully submerged, which will significantly reduce the hydrodynamic forces acting on then the submerged SMB 10, and the risers 26 are now protected through the splash zone. Fig. 54 is a longitudinal cross-section through the FPSO assembly 90, while Figs. 55-57 show vertical cross-sections through C-C, D-D and F-F, respectively, from Fig. 54. As mentioned above, the embodiment shown in Fig. 55 also includes a winch 64 that may be used to tension the SMB mooring lines 44. The winch 64 may be used in addition to or as an alternative to the winches 70 on deck 1 1 of the FPSO 1 , as e.g. shown in section D-D of Fig. 47. The riser pull in winch 72 is available for pulling in additional risers 26 through the guide tubes in the SMB 10 after docking, and for later riser installation/demobilization operations. Chain hoists or similar, or riser pull in winch 72 as shown in Fig. 56 may be used for mounting the spool piece 80 for establishing the final connection between one of the risers 26 on the SMB 10 and one of the riser reception pipes 12, whereby hydrocarbons extracted from a not shown subsea reservoir may be transported from the reservoir, through a not shown wellhead at the sea- bed, through the risers 26, up to the SMB 10, and further through the riser reception pipes 12 on the riser reception unit into the process modules 66. Emergency shut-down valves 37 are either mounted onto the isolation valve 36 on the SMB 10 or provided on the riser reception pipe side (topside) of the spool pieces 80. The actual processing of hydrocarbons in the processing units 66 will not be described in any detail herein. When all the risers 26 have been connected to their re- spective riser reception pipes 12, the installation process in finished. The FPSO 1 may then be ballasted to the full/deep draft D4. In order to secure the mechanical connection between the SMB 10 and the FPSO 1 , the locking means 40 may be provided with means to prevent the SMB 10 from disengage from the FPSO 1 due to negative load, locking the locking arms in the cradles 42. The negative load prevention means may be provided as a roof/superstructure above the cradle 42. It should be noted that the locking means 40 disclosed herein is only one of multiple possible embodiments. In one alternative embodiment, the locking means 40 may be based on not shown tongues on one of the SMB 10 and the FPSO 1 and complementary fitting grooves on the other of the SMB 10 and the FPSO 1 . The tongues may be provided on the SMB 10, whereby a similar ballasting and de-ballasting process discussed above may also be used in the alternative embodi- ment. The preferred location of the SMB as regards the effects on both the riser loads and the vessel motions is at longitudinal centreline midship

[00128] Fig. 58 shows, in a longitudinal cross-section, an alternative embodiment of a FPSO assembly 90 according to the present disclosure. The trunk 2 of the FPSO 1 is, in this alternative embodiment, shorter than in the embodiment shown in the previous figures, whereby the SMB 10 connects to the FPSO 1 at the stern/aft end 4 thereof rather than amidship 8. The SMB 10 is still provided along the axial centreline of the FPSO 1 , though this positioning is not visible in the shown cross-section, which is beneficial for reducing the previous mentioned roll effects due to the lever arm resulting from riser connections on the sides of the FPSOs according to the prior art and reduced vertically imparted motion on the flexible risers. The shorter trunk 2 represents a smaller insection in the hull 3 of the FPSO 1 , whereby more of the hull's 3 structural integrity may be maintained. The SMB 10 may carry all of the stern mooring of the FPSO 1 , though in the figure, also the stern of the FPSO 1 is shown moored by means of mooring lines 14. The shorter trunk 2 may simplify the actual installation process, since the FPSO 1 and SMB 10 may need to be moved a shorter distance relative to each other in order to make the final connection. The quick connection may also result in a quick de-connection, which may be useful e.g. in an emergency situation. In the figure, the SMB 10 is shown after it has been mechanically connected to the FPSO 1 , but before final connection of the risers 26 to the riser reception pipes 12. In an alternative, not shown embodiment, an even shorter trunk 2 than the one shown in Fig. 58 may extend the full height over the hull 3 of the FPSO 1 at the aft 4 thereof, whereby the SMB 10 may fill the whole trunk 2 through the whole height of the FPSO 1 . The SMB 10 may thus carry all of the aft mooring of the FPSO assembly 90.

[00129] A (SMB) buoy 10 may, as also mentioned above, especially in sheltered waters stay positioned even without mooring lines 44 or any mooring system to keep it positioned. The risers 26 may then have sufficient capacity to keep the buoy 10 on location without mooring lines 44. The configuration of the buoy 10 and the FPSO 1 will then remain the same, except that all the mooring of the FPSO assembly 90 after mating will be provided by the FPSO mooring system 14

[00130] Not shown in the figures or discussed in detail herein are the ballast systems provided on both the FPSO 1 and the SMB 10. The ballast systems typically comprise pumps, pipes, valves etc., as will be known to a person skilled in the art, for changing the draft/draught of the FPSO 1 and the SMB 10 by pumping water into or out from the SMB/FPSO for controlling the weight and thereby buoyancy of the SMB/FPSO.

[00131] It should be noted that the above-mentioned embodiments illustrate rather than limit the disclosure, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[00132] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage

[00133] The above discussion is meant to be illustrative of the principles and various embodiments of the present disclosure. While certain embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the disclosure. The embodiments described herein are exemplary only, and are not limiting. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.

[00134] The following clauses set out features of the invention which may not be presently claimed but which may form the basis for amendments or future divisional applications:

C l a u s e s Floating production storage and offloading vessel (FPSO) formed with a recess inside its hull for receiving and connecting to a buoy therein. FPSO according to clause 1, wherein said recess extends from the stern or from the bow of said FPSO along an axial centerline thereof. FPSO according to clause 1 or 2, wherein said recess extends from the stern or bow of said hull and substantially amidship. FPSO according to any of the preceding clauses, wherein the FPSO is provided with a plurality of riser reception pipes located substantially at said axial centerline of the FPSO. FPSO according to clause 4, wherein said plurality of riser reception pipes also are located substantially amidship of the FPSO. FPSO according to any of the preceding clauses, wherein said FPSO is moored by means of a plurality of mooring lines. FPSO according to any of the preceding clauses, wherein the hull of said FPSO is provided with a closable hatch for closing the entrance of said recess in the hull. Buoy, said buoy being provided with a plurality of riser suspensions and said buoy being adapted to be received and connected to a FPSO in a recess thereof inside the hull of the FPSO. Buoy according to clause 8, wherein said buoy is provided with ballasting means for shifting the draft of the buoy in water. Buoy according to any of the clauses 7-9, wherein the buoy is provided with locking means for mechanically locking the buoy to the FPSO. FPSO assembly comprising a FPSO according to any of the clauses 1-7 and a buoy according to any of the clauses 8-10, wherein said buoy is connected to the FPSO in said recess, and wherein a plurality a risers are connected to riser reception pipes on said FPSO via said buoy. Method for establishing an FPSO assembly according to clause 11, the method comprising the steps of: - hauling said FPSO relative to said buoy so that said buoy is slid horizontally into the recess of said hull of the FPSO;

connecting said buoy mechanically to the hull of said FPSO; and

- connecting said plurality of risers, suspended on the buoy, to the FPSO. Method according to clause 12, wherein the hauling of the FPSO relative to the SMB includes hauling the FPSO in over the SMB while the position of the buoy is substantially fixed. Method according to clause 12 or 13, wherein the method further comprises the step of pre-installing and suspending said plurality of risers to the buoy prior to arrival of the FPSO. Method according any of the clauses 12-14, wherein the method further comprises the step of ballasting the FPSO assembly to a final draft, after connecting the risers to the FPSO, where the buoy is fully submerged.

Claims

C L A I M S

1. An offshore production and storage system, comprising :

a spread moored buoy assembly including a riser buoy coupled to a mooring buoy, the riser buoy configured to receive and couple to risers;

wherein the spread moored buoy assembly is configured to be pre-installed offshore with the risers coupled thereto; and

wherein the spread moored buoy assembly is configured to couple to a floating vessel such that the risers fluidicly couple to the floating vessel via the riser buoy.

2. The offshore production and storage system of claim 2, wherein the mooring buoy is configured to couple to the floating vessel apart from the riser buoy coupling and the riser fluidic coupling.

3. The offshore production and storage system of claim 1, wherein the riser buoy couples into an internal cavity of the floating vessel.

4. The offshore production and storage system of claim 1, further comprising a compensation arm coupled between the riser buoy and the mooring buoy.

5. The offshore production and storage system of claim 4, wherein the mooring buoy is moveable relative to the compensation arm.

6. The offshore production and storage system of claim 1, further comprising two mooring buoys coupled to the riser buoy by compensation arms, wherein the riser buoy and the risers couple into an internal cavity of the floating vessel and the mooring buoys couple into mooring buoy hull cavities of the floating vessel.

7. The offshore production and storage system of claim 1, wherein the spread moored buoy assembly is configured to couple to an external and underside surface of the floating vessel.

8. The offshore production and storage system of claim 1, further comprising locks to moveably couple the spread moored buoy assembly to the floating vessel.

9. An offshore production and storage system, comprising : a spread moored buoy assembly including a riser buoy and two mooring buoys coupled to the riser buoy;

risers coupled to the riser buoy; and

a floating vessel configured to receive the riser buoy and thereby fluidicly couple to the risers, and configured to receive the mooring buoys separately from the riser buoy and the risers.

10. The offshore production and storage system of claim 9, further comprising moveable compensation arms coupled between each of the mooring buoys and the riser buoy.

11. The offshore production and storage system of claim 9, further comprising an internal hull cavity to receive the riser buoy and the risers, and two mooring buoy hull cavities each to receive one of the two mooring buoys.

12. The offshore production and storage system of claim 9, further comprising locks to moveably couple the riser buoy to the floating vessel.

13. An offshore production and storage system, comprising :

a spread moored buoy assembly coupled to risers, the spread moored buoy assembly configured to be pre-installed offshore with the risers coupled thereto; and a fixed heading floating vessel configured to receive and fix the spread moored buoy assembly to the floating vessel FPSO.

14. The offshore production and storage system of claim 13, wherein an internal bay of the floating vessel is configured to receive a riser buoy of the spread moored buoy assembly and two hull cavities in the floating vessel are configured to receive two mooring buoys of the spread moored buoy assembly.

15. The offshore production and storage system of claim 13, wherein hull cavities in the floating vessel are configured to receive mooring buoys of the spread moored buoy assembly while a riser buoy of the spread moored buoy assembly is configured to be secured at the external and underside surface of the floating vessel.

16. The offshore production and storage system of claim 13, wherein the floating vessel includes an underside opening to receive a submerged riser buoy of the spread moored buoy assembly.