EA008959B1 - Mobile offshore nit, mooring apparatus, foundation for an offshore vessel, and a method for mooring a vessel - Google Patents

Abstract

A mobile offshore unit with a vessel (1) and an anchoring includes a mooring apparatus with a receiving area (7) on the vessel (1), shaped as an, in the relation to the sea surface, a horizontal U defining a limited area towards the sea surface. Fenders (2) are placed along the periphery of the receiving area (7) and a foundation (10) for being lowered to the seabed from the vessel (1) forms the anchoring. The foundation is shaped with a cylindrical surface (14) for being received in the receiving area (7) with the fenders (2). A launch system for foundation (10) on the vessel (1) includes a tilt frame (20) supported for being pivoted about a vessel side for launching the foundation (10). A method is also claimed.

Description

The present invention relates to a mooring device for a vessel, a mobile offshore structure, a base, as well as a mooring method. The mooring device is especially adapted for use at sea along with wells intended for the extraction of hydrocarbons. The mooring device according to the invention includes a substantially cylindrical base fixed on the seabed and a receiving portion made on the vessel for receiving and fixing the base. The anchorage system allows the vessel to move around the base as well as up and down along the base.

A method of moving a mobile offshore structure from one place to another is also proposed.

In addition, the invention relates to a mobile offshore structure with a semi-permanent rigid mount, intended for use in the extraction or exploration of hydrocarbons. The structure includes a base or tower adapted to be submerged in the seabed, and a vessel with equipment for lowering and raising the base from the seabed, in addition to securing the vessel to the base when the base is placed on the seabed.

During exploration and / or production of hydrocarbons in the sea, the vessel must in many cases be fixed on the seabed and connected to equipment located on the seabed or else designed to fill hydrocarbons. This anchorage should be such that a vessel intended for anchorage can be positioned relative to waves, ocean currents and wind direction in such a way as to avoid significant loads on the mooring device. In addition, the vessel must be able to move vertically in order to perceive the movement caused by waves, tides and loading or unloading.

The vessel should also conveniently be connected to equipment intended for the transfer of hydrocarbons.

In US Pat. No. 5,447,114, an example of a mooring system for a tanker is shown, in which hydrocarbons are transhipped between the berth and the vessel on the high seas. The mooring system is located in the bow of the vessel and allows the vessel to rotate in addition to certain movements caused by waves and loading. The system contains an underwater buoy, fixed in such a way that it can enter into the corresponding mating elements in the bottom part of the hull. This system, however, requires a rather complicated installation of a loading buoy and is not suitable for use at shallow depths.

In US patent No. 4927296 described vessel designed to install the platform structure on the supporting farms. The vessel is a vessel with two hulls with an opening between the hulls in the front of the vessel, so that the structure can be tilted down between them. The design is inclined relative to the axis of rotation on one side of the opening. However, the system is not adapted to fasten the structure after launching into the water.

Accordingly, there is a need for a system or structure that combines a convenient lowering of the base into the water, the mooring of the base and the mooring of the vessel to the base, and thus adapted for use in shallow water.

In this case, shallow water means water from a depth of 20-30 m.

According to the present invention, the mooring device, the mobile offshore structure, the base and the mooring method are described in the independent claims.

The vessel is equipped with a receiving area intended for receiving and attaching the vessel to the base. The site is located at one of the ends of the vessel, preferably in the fore part of the vessel, and has a shape that allows you to place the fender on the periphery of the site. The plot is placed at the end of the vessel in order to enable the vessel to turn around the base, depending on the impact of weather and currents, like a weather vane. The section may be formed by two projections forming a ϋ-shaped nose at the vessel, or it may be made in the form of a separate structure, which can be attached to the vessel as an auxiliary object. This design may, for example, include three beams, forming an open ϋ-shaped frame, provided with means for fastening to the end of the vessel. The frame in this case can be bolted or welded to the vessel. On the other hand, the design can be hinged and recline on the deck during periods when it is not in use. The open end of the frame must include fastenings, so that one or more restrictive elements can be attached to these fasteners in order to attach the frame to the base. The frame should also include the baffle elements placed between the frame and the base.

Fenders around the periphery of the site are placed in such a way that they can absorb the forces arising between the vessel and the turret. The fenders can be rotated to reduce the transmission of torque to the ground in order to reduce abrasion of the fenders. The baffle elements can rotate around an axis parallel to the base or perpendicular to the base. The fenders are preferably made of a durable and resilient material capable of withstanding typical mooring conditions, such as rubber or elastomer.

- 1 008959

The area formed by two protrusions and preferably having an I-shape has an open end into which a base can be inserted. When the base is introduced into the receiving area, it is fastened to the vessel by leading locking elements with fender elements facing the base, and the base is fixed in a position limited by the dimensions of the receiving section and the fixing element or elements. Fixation can be accomplished, for example, by placing a beam across the open end of the I-shaped section, or by using clamping elements with fender elements attached to them, which can be led to the base with one or more actuators and can be fixed with one or several locking elements. The actuator (s) may include hydraulic cylinders, pneumatic cylinders, thrust screws, rack and pinion gears, or similar actuators. When using clamping elements, they can be secured in position by means of clamping clamping elements and can include a locking bar holding the clamp in a predetermined closed position. In another embodiment, the locking bar may be placed between the clamps. The clamps will be hinged in the receiving area.

In addition, the vessel can be equipped with equipment for receiving and lowering the base in order to create a mobile structure intended for use primarily in the area of hydrocarbon production.

The equipment may include a skidder on the deck of the vessel, intended to push the base forward or backward, a means for leading the base along the skidding track to the inclined frame or the tilting beam at the edge of the receiving section. The tilting frame rests at the turning point on this edge and is adapted for temporary attachment to a tower or base, and interacts with the means for controlling the angular position of the tilting frame relative to the vessel when the axis of rotation is essentially perpendicular to the longitudinal axis of the barge. The tilting frame can be rotated relative to the edge by at least 90 ° using hydraulic jacks, winches, or other mechanical devices adapted to rotate the base in a vertical position. Temporary fastening of the tower can be carried out with fasteners or partial fasteners, so that the base can be temporarily held in a certain position relative to the inclined frame, and released only after the load is in the desired position. The detachable fastener may preferably be electrically or hydraulically controlled. Launching can be carried out when an inclined frame, made in the form of a hydraulic telescopic beam, is allowed to lower the inner telescopic beam, so that the base slides along the outer beam and sinks to the seabed. Fasteners that hold the base can then be separated, so that the inclined frame is released and it can be returned to its original position. On the other hand, the launching can be carried out by winches, lifting the base from the fasteners and lowering the base to the seabed in a controlled manner.

In addition, the vessel can be equipped with conventional units designed for the extraction of oil and gas, such as separating elements, pumps and valves.

The base preferably has the shape of a tower with at least a cylindrical part that is always above the surface for contact with the baffle elements of the receiving section. Accordingly, the length of the base should be such that it can extend from the seabed and for a certain distance above the sea surface. The base is preferably made of steel or concrete, and it is adapted for attachment to the seabed, preferably by direct installation at the bottom. It can be equipped with self-absorbing anchors or piles and pile hammers for attaching the base to the seabed. The base may also be equipped to be adapted for the production of hydrocarbons or for exploration and drilling. The dimensions of the base should provide resistance to the loads that are created by the vessel, which is attached to it. The base or tower may be hollow, may contain various equipment, and may in some cases be adapted to the release of water so that easy access to the equipment may be facilitated.

However, the structure or system can also be used in floating bases that are attached to the seabed by anchor chains or similar devices, and it is important that the base can remain essentially stable, with a vertical axis, in order to ensure the correct functioning of the vessel anchorage system.

If the vessel is intended for oil production, the base should be equipped with a swivel and wellhead equipment. The swivel allows the vessel to turn without damaging the pipe connections and similar equipment. On the other hand, it is possible to use the chain triggering dredge system. The vessel is equipped with cranes and similar equipment for all mechanisms that must be installed on the tower.

When the building with the vessel and the base should be moved to the next place, the vessel itself can lift the foundation and carry it with them. If the ship is not self-propelled, tug assistance may be required.

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A structure or system is limited to water depth and 20 m is considered the real upper limit in accordance with the forces that will impact the foundation, which must be attached to the seabed, and the foundation may become too heavy and cumbersome. However, there is nothing wrong with giving the building dimensions that allow it to be used at other depths.

The advantage of allowing the vessel to turn in the wind is that it will significantly reduce the forces acting on the vessel and the foundation. Without the possibility of rotation, the system will not be able to act properly under all possible weather conditions. If, for example, oil is unloaded from a vessel, if the vessel is used as a storage barge, tankers can be positioned along the barge, avoiding outside waves. The vessel can be attached to the base and rotate relative to the base when the wind direction and weather change, and will be equipped with all the equipment necessary for oil production, drilling or similar activities. The vessel can slide along the tower up and down vertically.

After installation, the vessel may be moored to the base as an object of support for activities carried out on the base or on a tower, such as a supply vessel in connection with drilling operations, oil storage, living quarters, etc. The foundation or tower can serve as the foundation of a drilling platform. In this regard, it is possible to achieve a reduction in the volume of drilling equipment, since the need for compensation for heave or for BOP blowout devices is reduced. The vessel can be equipped with modules capable of performing several functions, for example, drilling and production. The base should be sized to withstand significant loads, such as ice loads that are present in the winter in the north of the Caspian Sea. The cylindrical shape of the base is convenient for withstanding ice loads. The receiving section of the vessel, which can be performed at one of its ends, is formed by two bow projections, so that this receiving section is limited to these two projections. The base may be omitted between the two protrusions. The plot can usually have a size of 20 x 30 m. These protrusions are convenient, as they will restrict the deck portion, which facilitates access to the base, and lead to improved buoyancy when lowering and raising the tower.

Brief Description of the Drawings

FIG. 1 shows a perspective view of a vessel, a mooring device and a tower according to the invention;

in fig. 2 is a partial sectional view of a perspective view of an embodiment of a base according to the invention;

in fig. 3 is a perspective view of a vessel, a mooring arrangement and a tower according to the invention, where the carrier of the swivel is clearly shown;

FIG. 4 corresponds to FIG. 3, with clearly shown swivel assembly on the base;

in fig. 5 is a perspective view in detail of the receiving portion of the vessel where the fender elements are clearly shown;

FIG. 6 corresponds to FIG. 5 with clearly shown clamping elements;

FIG. 7 corresponds to FIG. 5 and 6, however, the vessel is shown moored to the base;

in fig. 8 is a perspective view of how the base can move on the vessel in a substantially horizontal position;

FIG. 9 corresponds to FIG. 8, however, the base is in the lowering position on the seabed; and FIG. 10 corresponds to FIG. 9, however, the base is placed in a vertical position for subsequent lowering, placing and fixing on the bottom.

A detailed description of the preferred embodiments of the invention.

FIG. 1 shows a vessel according to the invention in the form of a barge 1. The barge has a large deck with equipment for producing hydrocarbons. Barge 1 includes two protrusions that form a ϋ-shaped nose, bounding the receiving area 7, intended for the base 10 in the form of a tower. The base 10 is intended for mooring the barge 1. The base 10 also serves as the installation site for various equipment adapted to combine the base 10 or the tower and the vessel or barge 1. The base 10 is equipped with a swivel that allows the barge to turn without twisting or breaking the pipes and other connections. On the other hand, it is possible to use the chain triggering dredge system. The barge is equipped with cranes and similar devices for all equipment that must be installed on the base. The figure also shows breaker elements 2 designed to absorb the forces that occur between the base 10 and the barge 1 in addition to the two clamping elements 3 in the receiving area 7. The mooring device is shown as an integrated part of the barge 1.

FIG. 2 shows how the base can be equipped with self-absorbing elements 12, which are intended to allow the base 10 to be attached to the seabed in the usual manner by suction.

Self-absorbing elements 12 are connected to a vacuum pump (not shown). Self-absorbing elements 12 are adapted for fastening the base 10 to the loose seabed.

In addition, the base is equipped with piles 13, which can be driven into the sea in the usual way.

- 3 008959 bottom with pile hammers (not shown). With this equipment, the base 10 can be fixed on a solid seabed. Thus, the base 10 can be adapted to be placed on different types of seabed. The base 10 includes a cylindrical outer surface 14, which is adapted to the mooring system with the receiving area, the fender elements and the fixing elements of the vessel. A swivel is shown, designed to connect the base to the vessel or barge 1.

FIG. 3 shows how the crane equipment of the barge 1 can be used for installation on the basis of the equipment, for example, the carrier of the swivel 15. An auxiliary vessel moored to the barge is shown, and since the barge will turn in the direction of wind and waves, the auxiliary vessel lying along the barge also will be installed in the desired position.

FIG. 4 shows how the crane systems of the barge 1 can lift the swivel 11 to the place intended for it on the base 10, and it also clearly shows how the clamping elements 3 with the baffling elements 2 and the locking elements 4 of the clamping elements 3 hold the barge 1 at the base 10 .

FIG. 5 shows in detail the receiving section 7 of the barge 1, where the baffle elements 7, the clamping element 3 and the actuating element 5 of the clamp 3 are clearly visible. The clamp 3 is shown in the retracted position. In this position, the vessel 1 can be separated from the base, or the base can be introduced into the receiving section 7. The figures also clearly show how the I-shaped nose forms the deck area on the sides of the receiving section 7.

FIG. 6 corresponds to FIG. 5, however, shows the clamping elements 3 in the position of fixing the base. This figure clearly shows the fastener or clamp 8 of the breaker element, which can be designed in such a way that the breaker elements 2 can rotate around its axis to prevent the transfer of torque between the barge 1 and the base. At the same time, this will reduce wear between the fender elements and the base. The locking elements 4 are placed between the stiffening elements along the peripheral part of the receiving section and the clamping elements 3 in order to keep these elements in the locked position, when the barge 1 has to be moored to the base 10.

FIG. 7 corresponds to FIG. 6, but also shows how the base 10 with the cylindrical outer surface 14 is placed in the locked position relative to the barge 1 by means of clamping elements fixed by locking elements 4 of the clamping elements 3.

FIG. 8, 9 and 10 three successive operations of placing the base 10 on the seabed are shown. Raising the base will be performed in the reverse order of launching.

FIG. 8 shows a mobile offshore structure that contains a barge 1 with a tilting frame 20 designed to lower the base 10. In this position, the base 10 is attached to the tilting frame 20, and the base 10 lies essentially in a horizontal transport position so that it is outside the working area when moving the barge 1. The inclined frame 20 includes means for securing and releasing the base 10, and the mechanism for moving the base 10 relative to the frame 20. This mechanism may include telescopic frame elements with hydraulic driven drive, screw systems or rack and pinion systems, or winches. On the other hand, the inclinable frame 20 may be provided with an upper frame 21 with a lifting system including winches or hydraulic cylinders placed between the upper frame and the holding device 23 for the base.

The inclined frame 20 with the upper frame 21 is pivotally mounted on the end of the barge 1 so that the inclined frame 20 with the upper frame 21 and the base 10 is temporarily fixed, can be inclined relative to the end edge of the barge 1 and move or float. This inclination can be carried out by moving the center of gravity of the inclined frame 20 relative to the axis of rotation using hydraulic cylinders, winches, or a combination of these mechanisms.

FIG. 8 also shows a restrictive beam 22 for the inclined frame 22, which holds the inclined frame in place and fastens the inclined frame during transport of the barge.

FIG. 9 corresponds to FIG. 8, however, shows that the restrictive beam 22 for the inclined frame 20 has been removed, and the inclinable frame 20 with the base 10 is partially inclined to lower the base 10 and is held by the holding device 23.

FIG. 10 corresponds to FIG. 8 and 9, however, the inclinable frame is transferred substantially to a vertical position for lowering the base 10. FIG. 10 also clearly shows a holding device 23 for the base 10 suspended on the upper frame 21 of the inclined frame 20. The holding device 23 can be raised up and down relative to the upper frame 21 for raising or lowering the base 10.

Thus, the barge can lower or lift the tower 10 from the seabed and move it to a new location.

Raising and lowering the base is preferably performed through the receiving portion 7, so that the base is placed on the seabed and ready to be fixed.

The method of using a mobile offshore structure includes bringing the structure to the desired position using tugs or own means of transportation, removal

- 4 008959 of the strut beam 22 from the locking position under the inclined beam 20, the inclination of the inclined beam 20 relative to the pivot bearing at the end of the barge 1 together with the base 10 fixed by the holding fixture 23 until the base 10 is located essentially vertically, lowering the base 10 by a lifting system, which may include winches or hydraulic cylinders placed between the upper frame and the holding device 23 for the base, fixing the base 10 on the seabed by means of piles 13 or sa ozasasyvayuschegosya armature 12, fixed to the base 1 of the barge 10 by actuation of the clamping elements 3 actuators 5, fixing clamping elements 3, 4 locking elements for mooring the barge 1 to the base 10, and the separation of the retaining device 23 from the base 10.

After this procedure, various equipment can be installed on base 10, and various connections between base 10 and barge 1 can be made.

If it is necessary to move the mobile offshore structure, these operations are performed in the reverse order, and the structures can be moved to a new location.

Claims (9)

CLAIM 1. A mooring device adapted to be placed at the end of a floating vessel (1), with two projections (6), forming an essentially ϋ-shaped receiving section (7) with lateral sides, an open end and fender elements (2), characterized by the fact that the baffle elements (2) are placed along all lateral sides of the internal-shaped receiving section (7), so that the device is adapted to receive and mooring, essentially, to the cylindrical body (10) of the base attached to the sea or ocean floor and protruding above the surface of the sea I; and the presence of at least one restrictive element at the open end of the receiving section (7) with additional baffling elements, designed for detachable and pivotal attachment of the cylindrical base body to the device. 2. Mooring device according to claim 1, in which the device forms an integrated part of the bow or stern of the floating vessel (1). 3. The mooring device according to claim 1, comprising two restriction members comprising two clamping members (3), which at one end are hingedly connected to the inner I-shaped receiving portion (7), and an actuating member (5) intended to be actuated each of the clamping elements (3) for fixing and releasing the cylindrical body (10). 4. The mooring device according to claim 1, in which the fender elements (2) are cylindrical, pivotally connected and fixed to a central axis substantially parallel to the central axis of the base body (10) during mooring. - 5 008959 5. The mooring device according to claim 1, wherein the fencing elements (2) are cylindrical, pivotally connected and fixed to a central axis substantially perpendicular to the central axis of the base body (10) during mooring. 6. Base (10) for a sea vessel (1), designed to be placed on the seabed, characterized in that it additionally includes a tower adapted to extend from the seabed to a certain height above sea level, at least , partly with a cylindrical surface (14) of the section projecting above sea level at the time when the base (10) is placed on the seabed; and piles (13), pile hammers and self-priming anchors (12) with suction pumps, designed to fasten the base (10) to the seabed. 7. A mobile offshore structure, comprising a vessel (1) and a mooring device for securing the vessel on the seabed, characterized in that it additionally includes an essentially cylindrical base (10) having a length in which the base can be placed on the seabed and stretch to a certain height above the seabed, and adapted for lowering to the seabed from the ship (10); a mooring device on a vessel with a receiving area (7) for the base (10), forming a horizontal figure relative to the sea surface and with internal periphery and sides surrounding a limited portion of the sea surface when the unit is launched into the water, and with fender elements (2) placed along periphery of the receiving area (7); the system of launching the base (10) on the water on the vessel (1) with a tilting frame (20) installed with the possibility of rotation relative to the ship’s side from a practically horizontal transportation position to a practically vertical installation position and tilting the base (10), means of moving the base (10) relative to the inclinable frame (20), the retaining device (23) for holding the base (10) on the inclinable frame (20), and the means for fixing the inclined frame (20) practically in the transport position. 8. The mobile offshore structure according to claim 7, in which the means for fixing the inclined frame (20) includes a fencing beam (22) designed to be placed under one of the ends of the inclined frame (20) and fixing the inclined frame (20) when located essentially in a horizontal transportation position. 9. The method of mooring a vessel with a structure according to claim 7, characterized in that it includes outputting the structure to the desired place using tugs or own means of transportation; unlocking the locking means of the inclinable frame (20) in a substantially horizontal transport position; the inclination of the inclined frame (20) relative to the hinge support at the end of the barge, together with the base (10), fixed by the holding device (23), until the base (10) is located essentially vertically; lowering the base (10) by hoists or hydraulic cylinders of the lifting system, placed between the upper frame and the holding device (23) for the base; separating the retaining device (23) from the base (10); securing the base (10) on the seabed by means of piles (13) or a self-absorbing anchor (12); fastening the barge (1) to the base (10) by actuating the clamping elements (3) with actuating elements (5) and fixing the clamping elements (3) with locking elements (4) for mooring the barge (1) to the base (10).