PRODUCTION OF HYDROCARBONS

Abstract

The present invention relates to a floating production platform for oil and/or gas production in a marine environment, the floating production platform comprising: a floater for providing buoyancy, the floater having suitable motion characteristics for supporting a dry tree riser, at least one riser support point constructed and arranged for supporting at least one dry tree riser which extends between the floating production platform and a seabed, a rotary communication assembly constructed and arranged for providing communication between the floating production platform and a vessel for: transferring a product fluid coming out of the at least one riser to the vessel, and/or transferring other fluids between the floating production platform and the vessel, and/or transferring electrical power via one or more electrical lines between the floating production platform and the vessel, transferring control signals via one or more electrical lines or fibre optic lines between the floating production platform and the vessel, the rotary communication assembly comprising: a circumferential communication line which in top view extends around the at least one riser support point, bridge communication line being in connection with the circumferential communication line at one end and comprising an end coupling at the other end for connection with the vessel, the bridge communication line constructed to bridge a gap between the floating production platform and the vessel, wherein the bridge communication line is movable along the circumferential communication line such that when in use the vessel weathervanes around the floating production platform, the bridge communication line rotates around the floating production platform with the weathervaning vessel, such that the rotary communication assembly maintains communication between the riser and the vessel.

Description

TECHNICAL FIELD

The present invention relates to the field of production of hydrocarbons (oil and/or gas) from subsea wellheads in a deep water marine environment. Hydrocarbons are found in subsea hydrocarbon formations in ever increasing water depths. It becomes increasingly difficult to produce these hydrocarbons. The hydrocarbons generally must be conveyed upwards from the seabed to the water level through a riser. The riser connects the subsea wellheads at the seabed to the supporting floating platform. These risers are in themselves complex and costly structures. The riser is often suspended from a floating platform. Generally, risers may have a catenary form or a straight form. A catenary form is typical for a wet tree system. A straight vertical form is typical for dry tree systems.

Dry Tree Risers and Wet Tree Risers

US2006021756 discloses the concept of dry trees versus wet trees very well. The following text is a quote from this document.

A variety of designs exist for the production of hydrocarbons in deep to ultra-deep waters, i.e. depths greater than 1300 meter. Generally, the preexisting designs fall within one of two types, namely, wet tree or dry tree systems. These systems are primarily distinguished by the location of pressure and reservoir fluid flow control devices. A wet tree system is characterized by locating the trees atop a wellhead on the seafloor whereas a dry tree system locates the trees on the platform in a dry location. These control devices are used to shut in a producing well as part of a routine operation or, in the event of an abnormal circumstance, as part of an emergency procedure.

In wet tree systems, these control devices are located proximate to a subsea wellhead and are therefore submerged. The primary function of the tree is to shut-in the well, in either an emergency or routine operation, in preparation for workover or other major operations.

Dry tree systems, in contrast, place the control devices on a floating platform out of the water, and are therefore relatively dry in nature. Having the production tree constructed as a dry system allows operational and emergency work to be performed with minimal, if any, ROV assistance and with reduced costs and lead-time. The ability to have direct access to a subsea well from a dry tree is highly economically advantageous. The elimination of the need for a separate support vessel for maintenance operations and the potential for increased well productivity through the frequent performance of such operations are beneficial to well operators. Furthermore, the elimination of a dedicated workover riser and the associated deployment costs will also result in a substantial savings to the operator.

Historically, dry tree systems have been installed in conjunction with tension leg platforms (TLP's) or spar-type platforms that float on the surface over the wellheads and have minimal heave motion impact upon the risers.

Dry tree platforms have a large central well bay for the surface trees. The size is dictated by well count and spacing. Topsides equipment has to be arranged around the well bay. The surface trees are designed for full reservoir shut-in pressures. A large production manifold is provided on deck, and a skidable rig is required for individual well intervention.

Compared with the wet tree development, the dry tree development offers a number of advantages, which include:

Easy access for inspection and maintenance.

Minimum loss of production due to maintenance/workover operations.

Higher level of reliability.

In addition, a Dry Tree Unit (DTU, also referred to as Dry Completion Unit, DCU) offers a permanent platform for drilling, workover operation, and hosts limited or full production facilities.

Motions

In a marine environment, weather conditions can be harsh. Wind, waves, currents exert forces on any floating platform and cause movements thereof.

Catenary risers have an advantage in that large motions of the platform can be followed by the catenary riser without damaging the catenary riser. Floating platforms such as semi-submersibles, barges and vessels have been used to suspend catenary steel or flexible risers, connecting the platform with the subsea wet-tree wellheads. This type of floater moves more in waves, but is in general less costly than the TLP's or Spar platforms.

However, a dry tree riser is substantially rigid and does not extend in a catenary form, but extends upwards from the seabed to the sea level along a substantially straight line. Thus, motions of a floating platform at the water level can not be followed very well, and a dry tree riser requires a relatively stable support point at the sea level.

An important aspect in implementing the dry tree solution is to ensure that the riser supporting mechanism can accommodate the platform movement. A DCU hull concept should have desirable motion characteristics. For this reason, the TLP's and SPARs are considered to be suitable DCU hull concepts. The TLP's and SPARs are designed using different principles to suppress motions and accommodate riser movements. The TLP relies upon the high tendon stiffness in the vertical direction so that its heave, roll and pitch natural periods are designed well below the wave excitation period. As a result, the dynamic amplification of vertical motion is almost nonexistent, i.e. the platform has small heave, roll and pitch motions. In the horizontal direction, the TLP is relatively compliant to the environment, and wind and wave generated slow drift motion can be significant. The TLP horizontal movement introduces a static vertical movement called set down. The attractive feature is that the top tensioned risers respond in a similar way to that of the tendons, and the platform set-down actually helps to reduce the riser stoke.

On the other hand, the SPAR is moored by catenary or taut-leg mooring lines and compliant to waves in both the vertical and horizontal directions. The motion natural periods are designed to be greater than the excitation period. By using deep draft and avoiding the wave excitation period, the SPAR has relatively small wave induced motions. The riser stroke of the SPAR is mainly caused by the platform horizontal excursions. Even though the SPAR's riser stroke is significantly larger than that of the TLP, it is accommodated by the specially designed riser buoyancy cans, which isolate the riser vertical movement from that of the platform.

The motion characteristics of conventional floaters (barge, vessel) are not as good as those of the TLP and SPAR. An alternative is a deep draft semi-submersible, having motions characteristics approaching the SPAR.

Costs of Floating Production Platforms

The TLP, SPAR and other floaters are all capable of carrying the full range of topsides facilities weights. Among the concepts, the TLP is most sensitive to topsides weight increase as it has to be accompanied by an increase of tendon sizes in order to maintain the same motion natural periods. This in turn requires a larger hull size to support the tendons. An increase in size leads to an increase in costs. A large TLP is therefore very costly. The costs of a SPAR also increase substantially with an increase in size.

Thus, floating production platforms which are very stable and show good motion characteristics are relatively expensive to construct. On the other hand, inexpensive floating platforms (barge, normal ship hull) exist which are suitable for carrying equipment for producing oil and gas. However, these inexpensive floating platforms have poor motion characteristics, and thus are less suitable for supporting dry tree risers.

Well Intervention

US2006021756 discloses the concepts of well intervention very well. The text below is a quote from this document. Requirements for workover and servicing of wells are relevant in the design of floating production platforms. All wells require routine or unplanned interventions for maintenance, data gathering, or reservoir management. These interventions can be categorized by frequency and duration. Frequency is a function of many variables including specific reservoir characteristics, well construction, completion type, and reliability of subsea and subsurface equipment.

Heavy intervention operations require production tubing removal and a drilling rig, marine riser, and BOP to perform safe operations. Causes include tubing failure, casing failures, gravel pack or sand screen failure, production isolation, and replacing wellhead connectors.

Light intervention operations are those where downhole service is performed through the wellbore. This includes all slick line, wireline, and coiled tubing work that can be performed without pulling production tubing. Operations include routine production logging, well stimulation, paraffin/asphaltene/hydrate remediation, changeout of downhole values, and reperforations.

Minor workovers are intervention services performed through flowlines or umbilicals, such as pigging, bullheading scale, or hydrate inhibitors, into a wellbore. Also, there are services performed external to the wellbore such as remotely operated vehicle services, control-pod and choke-module changeout on subsea trees, manifold and jumper inspections, etc.

Well interventions from a DTU, with drilling/workover facilities and direct vertical access into the wellheads, is easier and very competitive over working from a floater supporting (catenary) risers to wet-trees at subsea well heads. This is an advantage of dry tree risers. Therefore, in the field of the art, dry tree risers are a preferred choice in several situations.

Temperature Considerations

Other issues are also important. Ultra-deepwater presents flow assurance challenges to both wet and dry tree platform well systems. Production risers in the water column dominate overall hydraulic and thermodynamic system performance.

Wax (or paraffin) may form in a pipeline such as a riser when the temperature of the fluid drops below a certain point. This may clog up a pipeline carrying oil or gas. The clogging may be irreparable and permanently make the pipeline useless. The temperature requirements are important in the design of risers and are a driver in the development of so-called dry tree risers.

Well system architecture for both wet and dry platforms incorporate design features to mitigate and remediate blockage due to formation of wax and hydrates. Features include insulation, dual flow paths, supplemental dead oil circulation, chemical injection, and blockage remediation via coiled tubing.

A dry tree production riser can be double walled for superior temperature maintenance performance in view of single walled risers. Insulation of catenary risers is very expensive and complex and generally results in inferior temperature maintenance characteristics.

Other Design Considerations

Furthermore, various other requirements are relevant in the design of floating production platforms, such as: the need for a short time-to-first-oil, the desire for the possibility of pre-drilling of number of wells prior to the start of production, a desire for a pre-installation of production risers, the need for increased safety with respect to hurricanes, blow-outs, the need for a possibility of fast transfer of people to and from the production platform, the desire for the possibility of a phased field development, from early production to full field development, with extension of number of wells and risers

Moreover, there is a tendency in the field of the art to develop more marginal fields. To reduce risk of how a field will produce it is an option to have only a few wells drilled and during early production one learns more of how the field, being a subsea hydrocarbon formation, behaves and more wells can be drilled to stimulate field pressures and/or for additional hydrocarbon output. From early production, with a number of wells and risers and limited investments, the decision can be taken to drill additional wells and install additional risers. Dry tree units (DTUs) having a drilling derrick are capable of carrying out these further extension from early production to full field development, without the use of a drilling vessel or riser installation vessel, as is the case for wet trees.

The different requirements have led to various configurations for producing hydrocarbons in deep water. Because of the complex and often conflicting requirements, the different configurations vary widely. Some examples are discussed below.

DESCRIPTION OF THE PRIOR ART

U.S. Pat. No. 4,436,048 (Gentry et al) discloses one alternative. FIG. 12 shows a turret 72 positioned in a moonpool of a vessel 50. A derrick 71 is provided at another moonpool 60 for maintenance activities. A riser section 38 is suspended from an underwater floater 39 and connected via a yoke 41 and a flowline bundle 41 to the turret 72.

A disadvantage of the system of U.S. Pat. No. 4,436,048 is that during workover operations, the riser should be connected to the service moonpool 60. However, the vessel 50 is a regular vessel having poor motion characteristics. Motions of the vessel 50 may damage the riser during maintenance. Further, the connection operation of the riser to the service moonpool itself is cumbersome. Further, the presence of a separate turret 72 and a separate service moonpool is a disadvantage.

U.S. Pat. No. 5,857,808 (de Baan) shows another solution. A surface collection vessel 100 is provided having an opening 102 for a turret assembly 130. A problem associated with U.S. Pat. No. 5,857,808 is that the vessel has poor motion behaviour. This renders the use of dry tree risers impossible and necessitates the use of catenary risers which allow more movement of the end point at the surface. Catenary risers have a greater risk of temperature drops and thus clogging of the riser. The preferred option of a dry tree riser is not possible with the solution of U.S. Pat. No. 5,857,808.

Furthermore, because catenary risers are used and not dry tree risers, no maintenance activities can be carried out on the wells.

A further disadvantage of U.S. Pat. No. 5,857,808 is that the vessels 100 can only weathervane about the turret 130 in a limited fashion. For greater angles of rotation, disconnecting of the lines between the turret and the vessel is required, see also column 3, line 25 of U.S. Pat. No. 5,857,808.

U.S. Pat. No. 6,338,505 shows a swivel construction for use on a vessel moored to a single point mooring or a turret. A disadvantage of the system of U.S. Pat. No. 6,338,505 is that workover or maintenance activities are not possible on a well. When the swivel is applied on the vessel, the poor motion characteristics of the vessel limit the system to the use of catenary risers, including the temperature problems and paraffin development that are associated with catenary risers.

U.S. Pat. No. 6,968,899 discloses a system comprising a vessel 50 such as an FPDSO which envelops a turret 51. A small workover rig 56 is positioned on the turret 51. A swivel 53 is positioned on the turret above the workover rig 56.

U.S. Pat. No. 6,968,899 discloses that this system can be used with vessels, see column 1, line 65. In this embodiment, a disadvantage of the system of U.S. Pat. No. 6,968,899 is that it can only use catenary risers, including the temperature problems and paraffin development that are associated with catenary risers. This is due to the fact that vessel 50 has poor motion characteristics that make it unsuitable for the use with other kinds of risers in most operating conditions.

U.S. Pat. No. 6,968,899 also discloses that this system can be used with a semi-submersible. A disadvantage of such a system is that it is extremely costly. A semi-submersible which houses all production equipment and drilling equipment on board needs to be extremely large and automatically becomes very expensive.

U.S. Pat. No. 7,171,479 discloses a system comprising a vessel 12, which comprises a turret 16. On the turret, a drilling/workover rig 60 is mounted. A disadvantage of this system is that in case a dry tree riser is used, the operating conditions are limited to good weather conditions. This is due to the poor motion characteristics of the vessel 12. In most operating conditions, the system of U.S. Pat. No. 7,171,479 is limited to the use of a catenary riser.

Another known concept uses a Dry Tree Unit (DTU) in the form of a Tension leg platform or a Spar. A TLP or a Spar provides excellent motion characteristics and thus is suitable for dry tree risers. However, if a full production unit is installed on a dry tree unit, the Dry Tree Unit becomes very large and thus very expensive.

Another known design comprises a combination of a dry tree unit (DTU) and a separate FPSO. OTC11927—Dry Completion Units for West Africa Field Development, FIG. 1, discloses such a system

The advantage of this design is that the unit which supports the dry trees and requires excellent motion characteristics is relatively small, which limits the costs. The Dry Tree Unit may be a Tension Leg Platform or a Spar. The unit which carries the greater portion of the production and drilling equipment is a simple vessel such as an FPSO, which is relatively cost-effective. An umbilical connection comprising various different lines connects the DTO to the FPSO. Only a small number of key components of the entire facility are located on the relatively expensive DTU.

A disadvantage is the relatively large distance between the DTU and the FPSO, which makes operations difficult. Time lags and other practical problems arise during operation of this configuration.

Another disadvantage of this design is that the connection is fragile. Furthermore, weathervaning is difficult because the umbilical can become intertwined with the tension legs or with the dry tree risers of the TLP, which makes the design vulnerable.

Another known concept is disclosed in U.S. Pat. No. 4,490,121 which shows an FPSO with a disconnectable buoy. A disadvantage of this system is the difficulty in maintenance and workover operations on the wells.

WO2008012358 discloses another variant comprising an FPSO and a spar-like construction. A disadvantage of this system is the low temperature performance of the catenary risers and the lack of maintenance capability.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a working alternative to the prior art.

It is an object of the invention to provide a system which allows the use of dry tree risers in different operating conditions and which is relatively cost-effective.

It is an object of the invention to provide a system for producing hydrocarbons which allows disconnecting of a substantial part of the production equipment in case of bad weather without a risk of temperature drop and wax forming in the risers.

THE INVENTION AND ITS EMBODIMENTS

In order to achieve at least one object, the invention provides a floating production platform for oil and/or gas production in a marine environment, the floating production platform comprising:

• • floater for providing buoyancy, the floater having suitable motion characteristics for supporting a dry tree riser,
  • at least one riser support point constructed and arranged for supporting at least one dry tree riser which extends between the floating production platform and a seabed,
  • rotary communication assembly constructed and arranged for providing communication between the floating production platform and a vessel for:
    • transferring a product fluid coming out of the at least one riser to the vessel, and/or
    • transferring other fluids between the floating production platform and the vessel, and/or
    • transferring control signals via one or more electrical lines between the floating production platform and the vessel,
  • the rotary communication assembly comprising:
    • a circumferential communication line which in top view extends around the at least one riser support point,
    • a bridge communication line being in connection with the circumferential communication line at one end and comprising an end coupling at the other end for connection with the vessel, the bridge communication line constructed to bridge a gap between the floating production platform and the vessel, wherein the bridge communication line is movable along the circumferential communication line such that when in use the vessel weathervanes around the floating production platform, the bridge communication line rotates around the floating production platform with the weathervaning vessel, such that the rotary communication assembly maintains communication between the riser and the vessel.

In one embodiment, the present invention has an advantage in that the vessel may be located at a short distance from the floating production platform. This simplifies operations.

The weathervaning capability of the vessel allows operations in different weather conditions. The floating production platform can be kept small, because a substantial part of the equipment can be located on the vessel. Dry tree risers can be used, because the floating production platform has the required dynamic behaviour for supporting one or more dry tree risers.

The circumferential communication line and bridge communication line may be configured to transfer fluids, electrical power and control signals. Fluids may be transferred in both directions. The invention provides a simple and robust communication between the floating production platform and the vessel. The circumferential communication line defines an opening of substantial size which allows the placement of one or a plurality of riser support points and possibly related equipment within the contours of the circumferential communication line when viewed from above. For instance, a deck may be provided within the opening when viewed in top view. On the deck, the riser support points and other equipment may be positioned.

Because the circumferential communication line extends around the riser support point, the riser itself does not hinder the weathervaning of the vessel. Generally, a plurality of riser support points is located within the opening formed by the circumferential communication line.

Generally, the rotary communication assembly comprises a product fluid line for conveying the product coming from the riser from the floating production platform to the vessel. In use, the product fluid line is in fluid connection with the free end of the riser.

Generally, in an embodiment, a plurality of fluid lines and other lines will extend between the floating production platform and the vessel. Some fluids are transferred to and from the floating production platform, i.e. in both directions.

The circumferential communication line may be located below the free end of the riser, at the same level as the free end of the riser, or above the free end of the riser. The circumferential communication line may have an annular form. When the circumferential communication line is located below the free end of the riser, the riser may extend through the circumferential communication line.

The circumferential communication line may be circular or substantially circular, square, hexagonal, or have another form.

The vessel may be an FPSO. Because the vessel is a separate vessel from the floating production platform, it can be used at other sites earlier or later in time. A separate installation of the floating production platform is possible, prior to the arrival of the vessel.

Furthermore, in an embodiment disconnecting of the vessel from the floating production platform is possible without wax forming, because the dry tree risers have adequate temperature control. Other advantages may also exist, such as that an accommodation may be located on the vessel, at a distance from the risers. This reduces the risk of injuries to personnel in case of a blow-out. A helicopter deck may be located on the vessel. This may reduce the risk of damage to the risers in case of a helicopter crash. The separate configuration also provides an escape route to the floating production platform in case of fire or flooding on board the vessel.

Generally, the vessel will be an elongate, ship-shape vessel. These kinds of vessels are reliable and cost-effective in construction. Other forms are also possible

In an embodiment, the floating production platform comprises a workover rig or a coiled tubing device for performing workover operations on the dry tree risers, in particular to remove wax (paraffin).

In an embodiment, the floating production platform comprises at least one drilling derrick, wherein in top view the circumferential communication line extends around the at least one drilling derrick.

In an embodiment, the circumferential communication line comprises:

• • an annular swivel comprising an inner ring comprising an inner fluid conduit and an outer ring comprising an outer fluid conduit, the inner fluid conduit being in fluid connection with the rise, wherein the inner ring and outer ring are rotatable relative to one another and wherein the inner fluid conduit and the outer fluid conduit are in fluid connection with one another, wherein the bridge communication line is connected to the outer fluid conduit, or
  • a reel, wherein the bridge communication line and the circumferential communication line form one ongoing line which is flexible and is spooled partly on the reel and extends partly from the reel to the vessel.

A swivel may allow an unlimited number of rotations of the vessel around the floating production platform. A swivel construction is also possible for electric power lines. In this embodiment, one or more circular electrical tracks are provided and slider contacts are provided which make contact with the circular track. This swivel construction can also be used for control lines.

A reel is a reliable system and can comprise several windings of lines, which allows multiple rotations of the vessel around the floating production platform. Generally, the weathervaning action will not require a substantial number of rotations of the vessel about the floating production platform and a reel will allow a sufficient number of windings. The line on the reel may be a bundle of different lines, sometimes referred to as an umbilical.

In an embodiment, in top view the floating production platform is substantially circular. If both the circumferential communication line and the floating production platform are circular, a simple construction is possible which allows easy weathervaning. The floater may also be substantially circular. The circumferential communication line may extend along the outer perimeter of the floater or along the outer perimeter of a topside construction which is supported by the floater.

In an embodiment, the circumferential communication line extends around a plurality of riser support points. In this way a plurality of risers can be connected to the vessel.

In an embodiment, the circumferential communication line extends, in top view, around primary drilling equipment and primary production equipment. Thus, the equipment is conveniently placed inside the circumferential communication line.

In an embodiment, in top view the circumferential communication line extends substantially along an outer circumference of the floating production platform.

In an embodiment, the floating production platform is a Tension Leg Platform (TLP). TLP's are reliable structures which have excellent dynamic behaviour and are suitable for supporting dry tree risers. Because a substantial part of the equipment can be positioned on board the vessel, the TLP can be kept relatively small. The TLP will have connection points for connecting tendon legs to the seabed.

In an embodiment, the floating production platform is a Spar. Spars are also known structures which have good dynamic behaviour and are suitable for dry tree risers. Because a substantial part of the equipment can be positioned on board the vessel, the Spar can be kept relatively small. Typically, the Spar will have mooring points for connecting mooring lines to the seabed.

It is also possible to provide a semi-submersible vessel as the floating production platform. The semi-submersible will comprise a DP system for position control and orientation control.

In an embodiment, the floating production platform is a Dry Tree Unit (DTU). Other kinds of Dry Tree Units than a Spar or a TLP may also be used, such as a deep draft semi-submersible. Deep draft semi-submersibles have also good motion characteristics which approach the low Spar motions.

In an embodiment, the rotary communication assembly is constructed to allow rotation of the vessel around the floating production platform over an angle of at least 180 degrees.

In an embodiment, the rotary communication assembly is constructed to allow rotation of the vessel around the floating production platform over a plurality of revolutions.

In an embodiment, the floating production platform comprises a plurality of circumferential communication lines above one another in order to allow a plurality of fluid lines and other communication lines to extend between the floating production platform and the vessel. In this way, a plurality of lines can be provided between the floating production platform and the vessel, while maintaining the weathervaning capability.

In an embodiment, the circumferential communication line comprises a reel which is substantially flat and comprises a vertical rotation axis. A flat reel having a vertical rotation axis is a simple way of providing the circumferential communication line.

In an embodiment, the floater is a turret like construction constructed to be positioned in a moonpool of a vessel. This allows the vessel to be constructed such that it extends around or substantially around the floating production platform, when viewed in top view.

The present invention also relates to a combination of the floating production platform according to the invention and a vessel, wherein the at least one bridging communication line is connected at one end to the floating production platform and at the other end to the vessel.

In an embodiment, the combination comprises a rotary mooring assembly constructed to bear a mechanical load and configured to allow weathervaning of the vessel about the floating production platform, the rotary mooring assembly comprising:

• • one end which is connected with the floating production platform,
  • an opposite end which is connected with the vessel,
  • a rotary coupling at the end which is located at the floating production platform, which rotary coupling is constructed to allow weathervaning of the vessel around the floating production platform, the rotary mooring assembly being constructed for maintaining the vessel at a substantially controlled distance from the floating production platform.

With the rotary mooring assembly, a sturdy mechanical coupling between the floating production platform and the vessel is provided.

In an embodiment, the vessel is substantially separate from the floating production platform.

In an embodiment, the floating production platform comprises primary production equipment and the vessel comprises auxiliary production equipment and supplies which are auxiliary to the primary production equipment on the floating production platform.

This arrangement allows the floating production platform to be kept relatively small, while the vessel is constructed relatively large. Overall, this is a cost-efficient configuration.

In an embodiment, the floating production platform comprises:

• • a heat control device for paraffin/asphaltene/hydrate remediation to maintain wells after disconnect of the vessel and/or
  • a small accommodation for crew. In an embodiment, the auxiliary production equipment on the vessel comprises one or more components chosen from a group comprising:
  • a well stimulation device with water, gas and/or chemical injections
  • separation equipment for separating oil from water,
  • storage equipment for storing water, sand and/or sulphur which is separated from oil,
  • pressure reduction equipment for reducing a pressure in the oil and/or gas,
  • heating equipment for generating heat for heating the one or more production risers,
  • large accommodation for a crew,
  • fluid supply equipment for well maintenance,
  • power generator/power supply.

These components are relatively bulky and heavy and would result in a costly floating production platform if they were positioned on the floating production platform. Due to the positioning on the vessel, overall costs can be limited.

In an embodiment, the floating production platform comprises primary drilling equipment comprising at least one drilling derrick, wherein the vessel comprises auxiliary drilling equipment comprising at least one component chosen from a group comprising

• • mud supply equipment for providing mud to the drilling derrick,
  • drilling fluid equipment for providing drilling fluid to the drilling derrick.

These drilling components are relatively bulky and heavy and would result in a very costly floating production platform if they were positioned on the floating production platform. Due to the positioning on the vessel, overall costs can be limited.

In an embodiment, the circumferential communication line comprises a first reel, and the vessel comprises at least one second reel, wherein the at least one communication line is spooled on both reels, allowing a part of the fluid line which is spooled from the reel on the floating production platform during weathervaning to be spooled onto the second reel on the vessel and vice versa, thereby maintaining the length of the fluid line between the floating production platform and the vessel substantially the same.

With the reel on board the vessel, the communication line can have the same length at any weathervaning angle. This prevents entanglement of the communication line or damage thereto. As will be apparent the communication lines can be a fluid line, a power line, a different line or a bundle of different lines.

In an embodiment, the circumferential communication line comprises a reel for spooling the bridge communication line, allowing a part of the bridge communication line to be spooled from the reel during weathervaning of the vessel around the floating production platform, wherein an end of the bridge communication line is connected to a discharge point on the vessel, wherein the circumferential communication line and the discharge point are constructed to allow an excess length of the bridge communication line to be suspended in the water between the floating production platform and the vessel.

In an embodiment, the suspended part of the bridge communication line has a substantially catenary or U-shaped form.

In an embodiment, the rotary mooring assembly is somewhat flexible in that it allows a limited variation in distance between the floating production platform and the vessel in addition to the weathervaning capability.

The flexibility reduces the forces exerted by the vessel on the floating production platform.

In an embodiment, the rotary mooring assembly is constructed to maintain the vessel at a fixed distance from the floating production platform.

A fixed construction provides the advantage of no variations in distance between the floating production platform and the vessel which simplifies various operations.

In an embodiment, the vessel comprises a dynamic positioning system. The dynamic positioning system reduces the forces on the rotary mooring assembly and improves the position keeping of the vessel. In some embodiments, the position keeping of the DTU is also improved, especially in strong currents.

In an embodiment, the floating production platform is a Tension leg Platform (TLP) and the vessel is a Floating Production, Storage and Offloading (FPSO) vessel. This configuration provides a substantially complete and cost-efficient production facility.

In an embodiment, the floating production platform is a Tension leg Platform (TLP) and the vessel is a Floating Production and Offloading (FPO) vessel. In this configuration, the produced oil and/or gas can be exported to a remote location via an export flowline which is suspended from the floating production platform. No storage is required on board the vessel.

In an embodiment, the rotary communication assembly comprises a connecting/disconnecting coupling for connecting and disconnecting the vessel from the floating production platform, allowing:

• • the vessel to be removed to a remote location in times of bad weather or for other reasons and/or
  • installation of the floating production platform at a site prior to an installation of the vessel.

In an embodiment, the rotary communication assembly comprises a return product fluid line configured for transferring a product fluid back to the floating production platform, wherein the production platform comprises a support point for supporting a riser of an export pipeline which extends from the floating production platform to a remote location, the combination being configured to convey oil and/or gas from the vessel back to the floating production platform through the return fluid line and subsequently through the export riser and the export line to a remote location.

The present invention further relates to a method for producing oil and/or gas, the method comprising the steps of:

1. providing a floating production platform for oil and/or gas production in a marine environment, the floating production platform comprising:

• • a floater for providing buoyancy, the floater having suitable motion characteristics for supporting a dry tree riser,
  • at least one riser support point constructed and arranged for supporting at least one dry tree riser which extends between the floating production platform and a seabed,
  • a rotary communication assembly constructed and arranged for providing communication between the floating production platform and a vessel for:
    • transferring a product fluid coming out of the at least one riser to the vessel, and/or
    • transferring other fluids between the floating production platform and the vessel, and/or
    • transferring control signals via one or more electrical lines between the floating production platform and the vessel,
  • the rotary communication assembly comprising:
    • a circumferential communication line which in top view extends around the at least one riser support point,
    • a bridge communication line being in connection with the circumferential communication line at one end and comprising an end coupling at the other end for connection with the vessel, the bridge communication line constructed to bridge a gap between the floating production platform and the vessel, wherein the bridge communication line is movable along the circumferential communication line such that when in use the vessel weathervanes around the floating production platform, the bridge communication line rotates around the floating production platform with the weathervaning vessel, such that the rotary communication assembly maintains communication between the riser and the vessel,

2. providing a vessel, mooring the vessel to the floating production platform via a mooring assembly which allows weathervaning of the vessel about the floating production platform, and connecting the at least one bridge communication line to the vessel,

3. conveying untreated oil and/or gas hydrocarbons upwards through the production riser to the floating production platform,

4. transferring the oil and/or gas through the rotary communication assembly from the floating production platform to the vessel.

In an embodiment, the method comprises treating polluted hydrocarbons such as oil and/or gas on board the vessel. The treatment on board the vessel saves payload on the floating production platform which results in a lighter floating production platform

In an embodiment, the method comprises providing:

• • a return fluid line configured for transferring a fluid back to the floating production platform, and providing,
  • an export support point on the floating production platform for supporting a riser of an export line which extends from the floating production platform to a remote location,
  • an export line comprising an export riser suspended from the export support point, the method comprising:
  • transferring the treated oil and/or gas from the vessel back to the floating production unit through the return fluid line,
  • conveying oil and/or gas through the export riser and the export line to a remote location.

In this embodiment, no storage is required and the end product is directly transported away from the production facility to a remote location.

The present invention further relates to oil or gas, obtained via the method according to the invention.

The present invention further relates to a vessel constructed and arranged to be connected to the floating production platform of the invention, the vessel comprising:

• • a communication line coupling for connection with the bridging communication line of the rotary communication assembly,
  • a mooring assembly coupling for coupling with a rotary mooring assembly.

The invention is explained in more detail in the text, which follows with reference to the drawing, which shows a number of embodiments, which are given purely by way of non-limiting examples. In the Figures, like numbers denote like elements.

LIST OF FIGURES

FIG. 1A shows a diagrammatic side view of a combination of a floating production platform and a vessel according to the invention.

FIG. 1B shows a diagrammatic side view of a embodiment of the embodiment of FIG. 1A comprising stacked reels.

FIG. 2A shows a diagrammatic top view of another embodiment of the floating production platform according to the invention.

FIG. 2B shows a schematic aerial view of the variant of FIG. 2A.

FIG. 3A shows a side view in cross-section of a part of another embodiment of the floating production platform according to the invention.

FIG. 3B shows a side view of a cart for a fluid swivel conduit of the embodiment of FIG. 3A.

FIG. 4 shows a diagrammatic side view of another embodiment a floating production platform and a vessel according to the invention and shuttle tanker,

FIG. 5A shows a diagrammatic side view of another combination of a floating production platform and a vessel according to the invention.

FIG. 5B shows a diagrammatic side view of yet another combination of a floating production platform and a vessel according to the invention.

FIG. 6 shows a diagrammatic side view of another combination of a floating production platform and a vessel according to the invention.

FIG. 7 shows a diagrammatic side view of yet another combination of a floating production platform and a vessel according to the invention.

FIG. 8 shows a diagrammatic side view of another combination of a floating production platform and a vessel according to the invention.

FIG. 9 shows a diagrammatic side view of another combination of a floating production platform and a vessel according to the invention.

FIG. 10A shows a diagrammatic side view of another combination of a floating production platform and a vessel according to the invention.

FIG. 10B shows another diagrammatic side view of the floating production platform and a vessel of FIG. 10A.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1A shows a floating production platform 10 (FPP) according to the invention. The floating production platform 10 is connected to a vessel 12 via the rotary communication assembly 14 and via a rotary mooring assembly 16.

The floating production platform floats at the water line 18. The floating production platform may be a Tension Leg Platform (TLP), or may be a different kind of platform. The floating production platform 10 comprises a floater 20, which is substantially circular above the waterline. The floating production platform 10 can be moored to the seabed by means of mooring lines 102 and/or by means of tendon legs 24 (or tethers) extended downwards to the seabed. The floater 20 can consist of one large column with a central moonpool 79, or of multi columns. The floater 20 may have a tubular form with a vertical through passage (also referred to as moonpool), or a substantially tubular form. The moonpool 79 may have a circular form, but may also have another form, such as a square or rectangular form, or another form.

A plurality of risers 28 extend downward from the floating production platform 10 to the seabed. The risers 28 extend through a wellbay in the floater 20 and are connected to the floating production platform 10 at respective riser support points 48. The support points 48 generally comprise hydro-pneumatic tensioner systems mounted on the platform deck. Other systems are also possible and are known in the field of the art. The support points 48 comprise suspender-like members which connect the risers 28 to the floating production platform. ‘Trees’ are generally positioned at the upper end of the risers 28. The trees comprise couplings via which different lines are connected with the risers 28 such as product fluid, chemical injection fluid, water injection.

The risers 28 are dry tree risers which extend according to a substantially straight line downward to the seabed. The dry tree risers 28 allow workover operations to be performed on the well from the floating production platform 10.

On the floater 20, a topside construction 32 is mounted. The topside construction 32 extends above the water level 18 and provides space for various components. The topside construction 32 comprises different decks 36.

A drilling derrick 30 is provided on the floating production platform 10. The drilling derrick 30 comprises the known components of a hoisting assembly and a drive for rotating a drill string 34.

The Rotary Communication Assembly (RCA) 14 comprises three circumferential communication lines 38A, 38B, and 38C.

For the product coming from the risers, the circumferential communication line is in connection with the risers via a manifold to which each riser is connected. The product flows from the risers merge at the manifold and are subsequently directed as a single flow to the circumferential communication line 38.

Other lines also connect the floating production platform with the vessel, such as power lines for electrical power, control lines for control signals and other fluid lines for other fluids such as high pressure water and gas for gas injection, which fluids are also essential for the working of the entire facility.

The RCA further comprises three bridge lines 40A, 40B, 40C. Each bridge communication line 40 extends from a respective point 42 on the respective circumferential communication line 38 to a discharge point 44 on the vessel 12.

Each circumferential communication line 38 extends along the outer perimeter of the floating production platform 10. The circumferential communication lines 38 are circular, but may also have another form, such as an oval, a triangular form, a square or polygonal form. As will be discussed below, a spiral form is also possible. The circumferential communication lines 38 extend in a substantially horizontal plane, wherein each circumferential communication line 38 extends at a different level.

Each circumferential communication line 38 defines an opening 46. The openings 46 are located above one another and are large. The openings 46 are large enough for a plurality of riser support points 48 to be located within the opening, i.e. to be surrounded by the circumferential communication lines 38.

The drilling derrick 30 is normally located above the surrounded by the circumferential communication lines 38. Further, primary drilling equipment and primary production equipment is on board the floating production platform 10 and is positioned above or below the circumferential communication lines or is, in top view, also positioned in the opening 46, i.e. surrounded by the circumferential communication lines 38.

In this embodiment, the circumferential communication lines 38 are spooled on respective reels 49. The reels can also be horizontally positioned, separate or stackable, as shown in FIG. 1B. The bridge lines 40 extend to respective reels 49 on the vessel 12. The reels 49 are constructed to take in excessive lengths of the bridge communication lines 40 or to provide extra length of bridge communication lines 40, depending on the direction of rotation of weathervaning.

From the reels 49, further connecting lines run to equipment 50 installed on board the vessel 12. The equipment 50 comprises auxiliary drilling equipment 52 and auxiliary production equipment 54.

The auxiliary drilling equipment 52 on board the vessel comprises:

• • mud supply equipment for providing mud to the drilling derrick,
  • drilling fluid equipment for providing drilling fluid to the drilling derrick.
    The auxiliary production equipment 54 on the vessel comprises:
  • separation equipment for separating oil from water,
  • storage equipment for storing dirty water, sand, sulphur and other contaminations separated from the crude oil or gas,
  • pressure reduction equipment for reducing a pressure in the oil and/or gas,
  • heating equipment for generating heat for heating the one or more production risers,
  • accommodation for a crew,
  • fluid supply equipment for well maintenance,
  • power generator/power supply.

Further, an accommodation, a helicopter deck, and other facilities are provided on the vessel 12. Also storage of other products, i.e. ammonium, as by-product from the processed hydrocarbons can be stored in storage 56 on board the vessel 12 and the crude oil can be stored in the vessel 12. The vessel 12 may be referred to as an FPSO.

The vessel 12 is a low-cost ship-shape vessel or barge, whereas the floating production platform 10 is a costly Spar or TLP. Because a substantial part of the equipment is located on board the vessel 12, the floating production platform 10 can be designed relatively small. The combined configuration therefore is cost-effective.

The vessel 12 may be equipped with a dynamic positioning (DP) system 58 for position control not only of the vessel 12, but also controlling the position of floating production platform 10 and the DP also controls the forces in the rotary mooring assembly 16.

The rotary mooring assembly 16 comprises an annular rail 60 extending around the floating production platform 10 and mounted to the floating production platform 10. A slider or roller 62 is mounted to the annular rail 60 and movable along the rail 60. A hinge 64 is provided, which connects one end 65 of a beam 66 to the roller 62. The opposite end 65 of said beam 66 is connected via to a dead weight 68 which is suspended via another beam 70 from a suspension point 72. A hinge 71 is provided to allow for some rotation of the dead weight 68. The suspension point 72 is supported by a frame 74 which extends over the bow or stern 76 of the FPSO 12.

The mooring assembly 16 allows rotation of the vessel 12 around the floating production platform 10. Further, the mooring assembly allows some variation in distance between the floating production platform 10 and the vessel 12. When the distance increases, the beam 70 is inclined from the vertical, creating a return force via the dead weight. The return force returns the distance to the required distance. The opposite effect is attained when the distance between the floating production platform 10 and the vessel 12 decreases.

In use, the floating production platform 10 may be installed months before the vessel 12 is positioned in place. Some wells can be predrilled and other wells can be additional drilled if needed from the floating production platform 10, and the wells can be commissioned one by one. At a certain point in time, the vessel 12 is positioned in place and connected to the floating production platform 10 via the rotary communication assembly 14 and the rotary mooring assembly 16.

As production continues, a need for maintenance operations of the wells may arise. These can be carried out from the floating production platform 10 with the drilling derrick 30 or with other equipment on board the floating production platform 10.

On regular intervals, a shuttle tanker (not shown) can be moored at the vessel 12 for offloading hydrocarbons from the storage on board the vessel 12. The shuttle tanker then transports the hydrocarbons to another off-loading location or harbour for further processing.

In times of bad weather, the vessel 12 can be uncoupled from the floating production platform 10 and moved to a safe location. This removal does not necessary lead to wax deposition in the risers, because dry tree risers have good temperature control using the production control equipment on the floating production platform 10 to prevent a drop in temperature in the risers 28 and wells, limiting risk of wax deposition.

Also, when the fields have no more producible hydrocarbons, the vessel 12 can be removed and upgraded for use at the same or at another site.

FIG. 1b shows a substantially same embodiment as FIG. 1a, but in FIG. 1B the reels 49 are oriented horizontally, i.e. have a vertical axis.

FIG. 2A shows the configuration in top view and FIG. 2B in an aerial view. The circumferential communication line 38 extends in a spiral form around the riser support points 48 in the well bay 45. The product and other lines connect the dry tree on top of each riser with the process equipment on the floating production platform 10 or vessel 12. Each tree on top of each riser 28 is connected via product and other lines to one or more supply openings 78 of the circumferential communication line 38 on deck 36. The supply opening 78 is stationary with respect to the risers 28 and the riser support points 48.

From the supply opening 78, the circumferential communication line 38 extends in one or multiple windings around the reel 47. This can be a spiral form. The bridge communication line 40 is the part of the fluid line which extends to the vessel 12. When the vessel 10 weathervanes in clockwise direction around the floating production platform 10, the bridge communication line 40 is spooled off the reel 47 and is wound onto the reel 49. When the vessel 12 weathervanes in anti-clockwise direction around the floating production platform, the bridge communication line 40 is spooled from the reel 49 and onto the reel 47.

Because the bridge communication line 40 originates from an outer perimeter of the floating production platform 10, there is no or little risk of obstruction of any equipment to the bridge communication line 40. There is also no or little risk of entanglement of the bridge communication line 40 with any other object such as a mooring line of the floating production platform 10 or the risers 28.

FIGS. 3A and 3B show another embodiment of the invention. The floating production platform 10 is shown having a moonpool 79 through which a riser 28 extends upwards. The riser support point 48 is provided for providing support for the riser 28. Often, only lateral support is provided, since dry tree risers are generally equipped with buoyancy devices 86 around the riser. Thus, dry tree risers 28 are often free standing and only need lateral support.

The circumferential communication line 38 comprises a fluid swivel conduit 83 which comprises an inner non rotatable ring 80 and an outer ring as sliding door 82. The inner fluid conduit 81 and the fluid swivel conduct 83 are in fluid communication with one another via supply opening 89. The sliding door ring 82 is pulled outward to seal-off the fluid conduit swivel 83 to the seals of restrainers 87 by means of carts 84, positioned on deck 36 on a circular track around the topside 32. The fluid swivel 83 allows an unlimited number of rotations of the vessel 12 around the floating production platform 10.

FIG. 4 shows another embodiment, wherein the floating production platform 10 is a Truss Spar. Spars are known to have good dynamic characteristics and are suitable for supporting dry tree risers. Fluid swivels are provided as circumferential communication lines 38. The Truss Spar comprises a floater 20, a truss 23 and a stabilizing weight 21 at a lower end of the Spar.

Three fluid swivels 38 are provided above one another, forming a swivel stack. The swivels 38 are circular and extend around the outer perimeter of the floating production platform 10.

FIGS. 5A and 5B show embodiments comprising a floating production platform 10 and a vessel 12, wherein the rotary mooring assembly 16 comprises a fixed distance yoke. The rotary mooring assembly comprises the annular rail 60, the rollers 62, the hinge 64, a rotary device (swivel) 67 to allow the vessel to roll, and a beam 88 connected to the vessel 12 via a hinge 90. The embodiment of FIG. 5A has horizontal beams 22 which extend outwardly away from the floater 20. The ends of the beams 22 are constructed as a connection point for the tendon legs 24. The embodiment of FIG. 5B is substantially the same as the embodiment of FIG. 5A, but does not have the beams 22. Here, the tendon legs 24 are connected to the tubular floater 20 directly.

FIG. 6 shows another embodiment of the invention, wherein the vessel 12 does not comprise a substantial storage for end product, but a return fluid line is provided from the vessel 12 to the floating production platform 10, here being a multi column TLP, moored to the seabed with tendon legs 24. The return fluid line is configured in the same way as the fluid line from the floating production platform 10 to the vessel 12. A bridge communication line is provided and a circumferential communication line is provided. At the floating production platform 10, the circumferential communication line is connected to an export riser 96 which extends downward to a seabed 98 and which exports the product to a remote location.

In use, the hydrocarbons are transferred from the floating production platform 10 to the vessel 12. The hydrocarbons are subsequently treated on board the vessel 12, are subsequently returned to the floating production platform 10 and are subsequently exported through the export riser 96.

FIG. 7 shows an embodiment which is similar to the embodiment of FIG. 1, but with a Truss Spar as the floating production platform 10, with mooring lines 102 and truss 23 connected to the floater 20.

FIG. 8 shows an embodiment wherein the rotary mooring assembly 16 comprises a catenary chain, wire or cable 100. The catenary chain is connected to a roller 62 which is mounted for rotation on annular rail 60.

The floating production platform is a Spar which is moored to the seabed via mooring lines 102.

The vessel 12 is kept at an approximately constant distance from the floating production facility 10, using its dynamic positioning system with thrusters 58.

FIG. 9 shows an embodiment wherein the floating production platform 10 is configured as a turret-like construction and positioned in a moonpool 104 of a vessel 12. The rotary communication assembly 14 is substantially the same as in other embodiments. However, the rotary mooring assembly is different, in that the floating production platform 10 is kept in position because of a substantial form fit between the floating production platform 10 and the moonpool 104 of the vessel. In this configuration, the dry tree risers 28 have a curve to allow heave motions of the vessel in waves. The risers 28 may be Compliant Vertical Access Risers (CVAR).

FIG. 10A shows an embodiment wherein the bridge lines 40 extend from a respective point 42 on the respective circumferential communication line 38 to a discharge point 44 on the vessel 12. An end of the bridge communication line is connected to a discharge point on the vessel 12. No reels are provided on the vessel 12 for spooling an excess length of the bridge line 44. In this embodiment, the suspended length of the bridge lines 40 varies with the weathervaning of the vessel 12, as is shown in FIG. 10B. Preferably the floating production platform 10 is moored with tendon legs 24, to avoid contact with the suspended lines 40.

The circumferential communication line 38 and the discharge point 44 are constructed to allow any excess length of the bridge communication line 38 to be suspended in the water between the floating production platform 10 and the vessel 12 in a substantially catenary or U-shaped form. The size of the suspended part varies in dependence of the position of the vessel.

It will be obvious to a person skilled in the art that numerous changes in the details and the arrangement of the parts may be varied over considerable range without departing from the spirit of the invention and the scope of the claims.

Claims

1. Floating production platform for oil and/or gas production in a marine environment, the floating production platform comprising:

a floater for providing buoyancy, the floater having suitable motion characteristics for supporting a dry tree riser,

at least one riser support point constructed and arranged for supporting at least one dry tree riser which extends between the floating production platform and a seabed,

a rotary communication assembly constructed and arranged for providing communication between the floating production platform and a vessel for transferring a product fluid coming out of the at least one riser to the vessel, and/or transferring other fluids between the floating production platform and the vessel, and/or transferring electrical power via one or more electrical lines between the floating production platform and the vessel, and/or transferring control signals via one or more electrical lines or fibre optic lines between the floating production platform and the vessel,

the rotary communication assembly comprising: a circumferential communication line which in top view extends around the at least one riser support point, a bridge communication line being in connection with the circumferential communication line at one end and comprising an end coupling at the other end for connection with the vessel, the bridge communication line constructed to bridge a gap between the floating production platform and the vessel, wherein the bridge communication line is movable along the circumferential communication line such that when in use the vessel weathervanes around the floating production platform, the bridge communication line rotates around the floating production platform with the weathervaning vessel, such that the rotary communication assembly maintains communication between the riser and the vessel.

2. Floating production platform of claim 1, comprising at least one drilling derrick, wherein in top view the circumferential communication line extends around the at least one drilling derrick.

3. Floating production platform of claim 1, wherein the circumferential communication line comprises:

an annular swivel comprising an inner ring comprising a inner fluid conduit and an outer ring comprising an outer fluid conduit, the inner fluid conduit being in fluid connection with the supply opening, wherein the inner ring and outer ring are rotatable relative to one another and wherein the inner fluid conduit and the outer fluid conduit are in fluid connection with one another, wherein the bridge communication line is connected to the outer fluid conduit, or

a reel, wherein the bridge communication line and the circumferential communication line form an ongoing line which is flexible and is spooled partly on the reel and extends partly from the reel to the vessel.

4. Floating production platform of claim 1, wherein the floating production platform comprises a plurality of riser support points and wherein the circumferential communication line extends around the plurality of riser support points.

5. Floating production platform claim 1, wherein the floating production platform comprises primary drilling equipment and primary production equipment and wherein in top view the circumferential communication line extends around the primary drilling equipment and primary production equipment.

6. Floating production platform of claim 1, wherein in top view the circumferential communication line extends substantially along an outer circumference of the floating production platform.

7. Floating production platform of claim 1, wherein the rotary communication assembly is constructed to allow rotation of the vessel around the floating production platform over a plurality of revolutions.

8. Floating production platform of claim 1, comprising a plurality of circumferential communication lines above one another in order to allow a plurality of fluid connections between the floating production platform and the vessel.

9. Floating production platform of claim 1, wherein the circumferential communication line is shaped by a reel which is substantially flat and comprises a vertical rotation axis.

10. Floating production platform of claim 1, wherein the floater is a turret like construction constructed to be positioned in a moonpool of a vessel.

11. Combination of the floating production platform of claim 1 and a vessel, wherein the at least one bridge communication line is connected at one end to the floating production platform and at the other end to the vessel.

12. Combination of claim 11, comprising a rotary mooring assembly constructed to bear a mechanical load and configured to allow weathervaning of the vessel about the floating production platform, the rotary mooring assembly comprising:

one end which is connected with the floating production platform,

an opposite end which is connected with the vessel,

a rotary coupling at the end which is located at the floating production platform, which rotary coupling is constructed to allow weathervaning of the vessel around the floating production platform, the rotary mooring assembly being constructed for maintaining the vessel at a substantially controlled distance from the floating production platform.

13. Combination of claim 11, wherein the floating production platform comprises primary production equipment and wherein the vessel comprises auxiliary production equipment and supplies which are auxiliary to the primary production equipment on the floating production platform.

14. Combination of claim 11, wherein the circumferential communication line comprises a first reel, and wherein the vessel comprises at least one second reel, wherein the at least one bridge communication line is spooled on both reels, allowing a part of the bridge communication line which is spooled from the reel on the floating production platform during weathervaning to be spooled onto the second reel on the vessel and vice versa, thereby maintaining the length of the bridge communication line between the floating production platform and the vessel substantially the same.

15. Combination of claim 11, wherein the circumferential communication line comprises a reel for spooling the bridge communication line, allowing a part of the bridge communication line to be spooled from the reel during weathervaning of the vessel around the floating production platform, and wherein an end of the bridge communication line is connected to a discharge point on the vessel, wherein the circumferential communication line and the discharge point are constructed to allow an excess length of the bridge communication line to be suspended in the water between the floating production platform and the vessel.

16. Combination of claim 11, wherein the floating production platform is a Tension leg Platform (TLP), a Spar or a Dry Tree Unit (DTU) and the vessel is a Floating Production, Storage and Offloading (FPSO) vessel or a Floating Production and Offloading (FPO) vessel.

17. Combination of claim 11, the rotary communication assembly comprising a return fluid line configured for transferring a fluid back to the floating production platform, wherein the production platform comprises a support point for supporting a riser of an export pipeline which extends from the floating production platform to a remote location, the combination being configured to convey oil and/or gas from the vessel back to the floating production platform through the return fluid line and subsequently through the export riser and the export line to a remote location.

18. Method for producing oil and/or gas, the method comprising:

1. providing a floating production platform for oil and/or gas production in a marine environment, the floating production platform comprising a floater for providing buoyancy, the floater having suitable motion characteristics for supporting a dry tree riser, at least one riser support point constructed and arranged for supporting at least one dry tree riser which extends between the floating production platform and a seabed, a rotary communication assembly constructed and arranged for providing communication between the floating production platform and a vessel for: transferring a product fluid coming out of the at least one riser to the vessel, and/or transferring other fluids between the floating production platform and the vessel, and/or transferring electrical power via one or more electrical lines between the floating production platform and the vessel, and/or transferring control signals via one or more electrical lines or fibre optic lines between the floating production platform and the vessel, the rotary communication assembly comprising: a circumferential communication line which in top view extends around the at least one riser support point, a bridge communication line being in connection with the circumferential communication line at one end and comprising an end coupling at the other end for connection with the vessel, the bridge communication line constructed to bridge a gap between the floating production platform and the vessel, wherein the bridge communication line is movable along the circumferential communication line such that when in use the vessel weathervanes around the floating production platform, the bridge communication line rotates around the floating production platform with the weathervaning vessel, such that the rotary communication assembly maintains communication between the riser and the vessel,

2. providing a vessel and mooring the vessel to the floating production platform via a mooring assembly which allows weathervaning of the vessel about the floating production platform, and coupling the rotary communication assembly to the vessel,

3. conveying substantially untreated oil and/or gas hydrocarbons upwards through the production riser to the floating production platform,

4. transferring the oil and/or gas through the rotary communication assembly from the floating production platform to the vessel.

19. Oil or gas, obtained via the method of claim 18.

20. Vessel constructed and arranged to be connected to the floating production platform of claim 1, the vessel comprising:

a coupling for connection with the bridge communication line of the rotary communication assembly of claim 1,

a mooring assembly coupling for coupling with a rotary mooring assembly.