"SYSTEM AND APPARATUS FOR SUPPORT OF SUBSEA ELONGATE

STRUCTURES"

FIELD OF THE INVENTION

[0001] The present invention relates to a system and apparatus for support of an underwater elongate structure.

BACKGROUND

[0002] Subsea elongate structures are installed on the seabed to transport many things, such as fluids and gas through pipelines and data or power through electrical or optical telecommunication cables. In some instances, the elongate structure is installed on a seabed which is undulated and/or uneven. Once laid on such an undulating seabed, the elongate structure may naturally span seabed depressions. Therefore, it may only be supported at local high points on the seabed.

[0003] Instances may occur where the span lengths are greater than what is acceptable in order to maintain integrity of the elongate structure. Hence, some means of span rectification may be required, whereby lengths between high points on the seabed are reduced. As a result, these structures are supported, or the seabed is flattened, by various methods.

[0004] One method of reducing span length is with the provision of intermediate supports between the support points offered by the natural seabed. Subsequent to laying of the elongate structure, grout bags may be individually lowered to the seabed. The grout bags are placed alongside the structure at free span locations then slid under the structure. A grout line is attached from a provided vessel to a bag to facilitate filling of the bag with grout. The bag is inflated with the grout filling process and rises to meet the underside of the structure. Once set, it forms a rigid support. This method is tedious and time-consuming requires much manpower to lower and fill individual grout bags. [0005] A further method of reducing span length involves the assessment and alteration of the seabed prior to laying the elongate structure. Subsequently, the seabed where the elongate structure is to be placed is substantially flattened. This may be achieved by numerous processes including removal of local high points by dredging or jetting and filling natural depressions. These processes are often expensive and very destructive to the ocean environment.

[0006] The present invention attempts to overcome at least in part the aforementioned disadvantages of previous methods for span rectification and/or support of an underwater elongate structure.

SUMMARY OF THE INVENTION

[0007] In accordance with one aspect of the present invention there is provided a system for support of an elongate structure under water characterised by comprising at least one fillable bag installed on the structure and secured thereto by attachment means.

[0008] The bag may be initially in a collapsed condition and wrapped around the elongate structure.

[0009] A release means may be provided to enable the bag to move to an expanded condition to form a receptacle.

[0010] The release means may be arranged to operate in sequential stages in which the bag is initially partially expanded and subsequently fully expanded.

[0011] The bag may contain at least one springing mechanism to facilitate expansion of the , bag to the expanded condition.

[0012] The bag may comprise a flotation means to assist in expansion of the bag.

[0013] The bag may comprise a base which acts as a cover in the collapsed condition of the bag.

[0014] The release means may be located at the base. [0015] The receptacle may comprise a port arranged to be connected to a feed means to enable the receptacle to receive a filling material.

[0016] The attachment means may comprise strap means provided around the elongate structure and connected to the receptacle so as to retain the bag in place.

[0017] In accordance with a further aspect of the present invention there is provided an apparatus for attachment to an elongate underwater structure to provide support characterized by comprising a tillable bag provided with means to secure attachment to the structure.

[0018] The apparatus may be arranged in a collapsed condition initially and disposed about the elongate structure, and means is provided for expanding the bag whilst it is secured to the structure.

[0019] The fillable bag may comprise a base which acts as a cover in the collapsed condition of the apparatus.

[0020] The base may be provided with a release means arranged to enable the bag to be expanded to form a receptacle arranged to support the structure.

[0021] The bag may be arranged to expand in more than one stage to an initially partially expanded condition and subsequently to a fully expanded condition.

[0022] The means to secure attachment to the structure may comprise strap means attached to the bag and arranged to extend around the structure so as to retain the bag in place.

BRIEF DESCRIPTION OF DRAWINGS

[0023] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is an upper perspective view of an apparatus for support of an underwater elongate structure in accordance with one aspect of the present invention in a fully expanded condition; Figure 2 shows an arrangement for installation of the apparatus of Figure 1 on an underwater elongate structure;

Figure 3 is a lower perspective view of the apparatus of Figure 1 in a first, collapsed condition;

Figure 4 is an upper perspective view of the apparatus of Figure 1 in a second, partially expanded condition;

Figure 5 is an upper perspective view of the apparatus of Figure 1 in a third, further partially expanded condition;

Figure 6 an upper perspective view of the apparatus in the condition shown in Figure 3;

Figure 7 is a perspective view of a part of the apparatus of Figure 1 ; and

Figure 8 is an upper perspective view of the apparatus of the present invention in accordance with another embodiment thereof,

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Referring to Figure 1 to 7, there is shown a preferred embodiment of an apparatus for support of an underwater elongate structure such as a pipeline 10 lying on a seabed, comprising one or more fillable bags 12 installed on the pipeline 10 before it is laid underwater, in accordance with the present invention.

[0025] The, or each, bag 12 is arranged to be engaged with the pipeline 10. As seen in Figure 2, each bag 12 is preferably arranged to be mounted upon the pipeline 10 prior to submersion of the pipeline 10. A preferred means for mounting the bag 12 upon the pipeline 10 comprises the use of straps 38 typically with buckles 40 (see Figure 7). The straps 38, preferably of a tough, heavy duty fabric, are fixed to the bag 12 through any suitable means such as stitching or using adhesive. The straps 38 span the pipeline 10 and are secured using the buckles 40 to result in the mounting of the bag 12 upon the pipeline 10.

[0026] In a preferred embodiment, each bag 12 is constructed from woven marine-grade fabric and is arranged in a first condition wherein the bag 12 is in a collapsed configuration and arranged to be wrapped around the pipeline 10 as shown in Figure 3. Upon activation of a means for opening such as a release mechanism 22, the bag 12 goes from the first condition to a second condition, wherein the bag 12 is arranged in a partially expanded configuration, as shown in Figure 4, with a first side of the bag 12 unwrapped. Subsequently, as shown in Figure 5, a second side of the bag 12 is also unwrapped from the pipeline 10 so that the bag 12 is in a third condition. Final y, a resulting receptacle 14, comprising sides 24, when the bag 12 is in a fourth, fully expanded condition, is shown in Figure 1.

[0027] As best seen in Figure 6, the release mechanism 22 preferably comprises a rod 21 housed within a shaft 25. The rod 21 may be made from any suitable material, preferably carbon steel. The rod 21 includes, preferably two, L-shaped fingers 23 which engage with receptacle tubes 27 when in the locked position. The shaft 25 is segmented to allow protrusion of the fingers 23. That is, the shaft 25 is provided in two or more segments so that a space defined between segments of the shaft 25 is where a finger 23 may protrude from the rod 21. The rod 21 further comprises a cap plate and handle 29 which, when pulled, slides the rod 21 axially within the shaft 25. The fingers 23 are simultaneously pulled and released from the tubes 27 allowing transition of the bag 12 from its first condition to its second and third conditions.

[0028] Preferably, transition of the bag 12 from the first condition to the second and third conditions is facilitated through the presence of one or more springing mechanisms 18 (see Figure 1). The springing mechanism 18 comprises any suitable tensile material such as spring steel or tensile plastic, which allows an unfurling of the bag 12. Transition to the second and third conditions is preferably enabled by utilising energy stored in the, or each, springing mechanism 18, when tensioned through the arrangement of the bag 12 in its first, collapsed condition as shown in Figure 3.

[0029] As discussed above, the bag 12 is arranged to go from the second and third conditions to a fourth condition, wherein the bag is arranged in a fully expanded condition, as shown in Figure 1. In the fourth condition, the bag 12 forms a receptacle 14 disposed substantially below the pipeline 10. The two sides of the receptacle 14 separated by the pipeline 10 are in connection with one another via the straps 38.

[0030] Transition from the third condition to the fourth condition is preferably enabled by buoyant material present within flotation strips 20 in an upper portion of the receptacle. Preferably, the flotation strips are substantially parallel to the pipeline 10 and positioned in a roof 36 of the receptacle 14, near the upper edge of each side 24 of the receptacle 14. The buoyant material acts in assisting the bag 12 to form the desired shape upon opening into the fourth condition. The flotation strips 20 may comprise any suitable material which is less dense than seawater, including but not limited to polystyrene, foam or gas.

[0031] In accordance with a preferred embodiment of the present invention, the springing mechanism 18, which facilitates the transition of the bag 12 from the first condition to the second and third conditions, is located in a base 16 of the receptacle 14 as seen in the fully expanded fourth condition, as shown in Figure 1. In one embodiment, the springing mechanism 18 may be integrally formed with the base 16. More preferably, the material of the base 16 allows the base 16 to act as the springing mechanism 18. The springing mechanism 18 is preferably denser than seawater to ensure the base 16 falls to the seabed. The base 16 of the receptacle 14 preferably comprises a relatively hard shell, which may be constructed from any suitable material including, but not limited to, low-density polyethylene (LDPE).

[0032] As can be appreciated from the Figures, the base 16 forms the exterior of the bag 12 when it is arranged in its first, collapsed condition. As such, the base 16 acts as a shell or cover of the bag 12 in its first condition. Therefore, the base 16 is ideally constructed of a strong but flexible material which allows the bag 12 to be arranged in its first condition wrapped about the pipeline 10. The base 16 may be in connection with the bag 12 by being sandwiched between layers two or more layers of fabrics of the bag 12. Alternatively, the base 16 may be stitched or otherwise connected with the sides 24 of the receptacle 14 of the bag 12.

[0033] Again, as can be understood from the Figures, the release mechanism 22 is located at the base 16. In a preferred embodiment of the present invention, the shaft 25 and tubes 27 of the release mechanism 22 are integrally formed with the base 16. In an embodiment where the base 16 is constructed from LDPE, the shaft 25 and tubes 27 may be integrally moulded with the LDPE base 16.

[0034] Referring to Figure 1 , a roof 36 of the receptacle 14 preferably comprises a port 26, connected to a line 42 and a connector 46, to which a conduit 28 (see Figure 2) may be attached to facilitate filling of the receptacle 14 with a filling material. Preferably, the filling material comprises a settable material, such as grout or concrete. The roof 36 of the receptacle 14 preferably further comprises a second port 30 which allows return of the material inside the receptacle 14. The ports 26 and 30 may be made from any suitable material, preferably woven marine-grade fabric similar to the preferred fabric of the bag 12. As such, the ports 26 and 30 may be integrally formed with the bag 12.

[0035] As seen in Figure 1 , the straps 38 span the pipeline 10 and connect to the roof 36 on opposite sides of the receptacle 1 . In one embodiment of the present invention, the straps 38 are applied tightly around the pipeline 10 to prevent movement of the bag 12 longitudinally with respect to the pipeline 10. In another embodiment of the present invention, the straps 38 are applied in a loose fashion, in order to allow the receptacle 14, to be disposed substantially below the pipeline 10, or to freely rotate about the pipeline 10 to find an optimal final position on the seabed or other floor as may be present. A hold back strap 50 is provided in accordance with this embodiment to restrict or substantially prevent movement of the bag 12 along the length of the pipeline 10.

[0036] With reference to Figure 8, in another embodiment of the present invention, internal straps 48 are provided at the interior of the bag 12. The internal straps 48 extend between any one or more of the interior of the walls 24, base 16 and roof 36 of the receptacle 14. The internal straps 48 are constructed of the fabric of the bag 12 or the straps 38, or any other suitable material, and assist in reinforcing the receptacle 14 and forming the desired shape of the receptacle 14.

[0037] Referring to Figure 2, there are shown two embodiments of a method for support of an underwater elongate structure such as a pipeline 10 lying on a seabed, comprising fillable bags 12 installed on the pipeline 10 before it is laid. The support of the pipeline 10 may include support required where the pipeline spans a low point on an uneven sea floor, herein referred to as span rectification. Additionally, support may be provided where the resting place, other than the seabed, of the pipeline 10 is not even, for example, where the pipeline 10 may be in connection with a structure and is off the seabed.

[0038] In accordance with a first aspect of the present invention, the bags 12 are filled once they are at rest on the seabed. In accordance with a second aspect of the present invention, the bags 12 are at least partially filled after submersion but prior to reaching the seabed. In accordance with this second method, each bag 12 further comprises the hold back strap 50 for maintaining the bag 12 in its longitudinal position relative to the pipeline 10. The hold back strap 50 is, at a first end, in connection with the at least partially filled receptacle 14 and, at a second end, in connection with a point on the pipeline 10 in the direction of laying.

[0039] Support of the pipeline 10 is achieved using a filling material which is receivable within the apparatus of the present invention. As best seen in Figure 7, a line 42 is receivable within the filling port 26. The line 42 may be made of any suitable material including but not limited to flexible high pressure hose. Preferably, a hose clamp 44 is employed to secure the connection of the line 42 and port 26. A distal end of the line 42 is secured to a strap 38 of the bag 12 using a clamp 52 or other suitable means. The distal end of the line 42 also comprises a connector 46, preferably a female grout stab-in connector. The connector 46 provides a means for attachment of a conduit 28 (see Figure 2) for supplying of a filling material to the receptacle 14.

[0040] In use, the bag 12 is arranged in the first condition shown in Figure 3 so as to be wrapped around the pipeline 10 prior to the pipeline 10 being laid. As seen in Figure 2, each bag 12 is preferably arranged to be mounted upon the pipeline 10 prior to submersion of the pipeline 10. According to a preferred method of using of the apparatus of the present invention, the bag 12 is mounted upon the pipeline 10 while the pipeline 10 remains on a ship or other structure from which it will be laid. The wrapped arrangement of the bag 12 about the pipeline 10, as will be understood with reference to the Figures, is achieved through firstly, mounting of the bag 12 onto the pipeline 10 in a typical fashion using the straps 38 and buckles 40, wrapping of a first then a second side of the bag 12 about the pipeline 10, and finally securing of the bag 12 with the release mechanism 22 in its closed position.

[0041] In accordance with one aspect of the present invention, once the pipeline 10 is in its desired location such as on the seabed or spanning local high points on the seabed, the release mechanism 22 is activated. In accordance with another aspect of the present invention, the release mechanism 22 is activated prior to the pipeline 10 resting on the seabed. Activation of the release mechanism 22 involves pulling the cap plate and handle 29 which in turn causes the rod 21 to slide axially within the shaft 25. The fingers 23 are simultaneously pulled and released from the tubes 27 and the release mechanism 22 is opened. The bag 12 is then able to move from the first condition to the second, third and fourth conditions thereby forming the receptacle 14 disposed substantially below the pipeline 10. In one embodiment, the release mechanism 22 may be activated locally by a diver. In another embodiment, the release mechanism 22 may be activated remotely, such as for example through the use of an ROV 34.

[0042] Once the release mechanism 22 has been activated, the springing mechanism 18, through the energy stored therein from the wrapped configuration of the bag 12, acts to open the bag firstly into the second then third conditions. Transition into the second condition involves the unfurling of a first side of the shell base 16 of bag 12, as shown in Figure 4. Following this, transition into the third condition involves unfurling of the second side of the shell base 16 of the bag 12, as shown in Figure 5.

[0043] Subsequently, the bag 12 goes from the third condition to the fourth condition as shown in Figure 1. The flotation strips 20 included in the roof 36 of the receptacle 14 assists in causing the collapsed sides 24 of the bag 12 in the second and third conditions to float until they are extended, forming the desired shape of the receptacle 14 in the fourth condition. The internal straps 48 in the embodiment of Figure 8 act to reinforce the bag 12 and assist in formation of the expanded receptacle 14.

[0044] When filling of the bag 12 is to commence, the conduit 28 is attached to the connector 46 in connection with the first port 26 on the roof 36 of the receptacle 14. Attachment of the conduit 28 to the connector 46 may comprise any suitable means for connection relative to the type of connector 46 chosen. Material may be provided to the bag 12 through the conduit 28, from a vessel 32 as shown in Figure 2. According to one aspect of the present invention, material is pumped from the vessel 32 through the conduit 28 to the bag 12. According to a second aspect of the present invention, material travels from the vessel 32 through the conduit 28 to the bag 12 under the force of gravity. The second port 30 on the roof 36 of the receptacle 14 may facilitate displacement of sea water or other substance in the bag 12 to allow the filling material to fill the volume within the receptacle 14. Once the bag 12 is filled with material, return of filling material through the second port 30 may also assist in determining when the receptacle 14 has been filled completely.

[0045] Once the bag 12 has received the fill ing material and/or the filling material has set, the filled receptacle 14 provides an artificial point on the seabed upon which the pipeline 10 rests. As such, the pipeline 10 is effectively supported by the filled bag 12, where support may be required, for example where the pipeline 10 spans a low point on the seabed.

[0046] Other embodiments for span rectification and/or support of an underwater elongate structure are also contemplated in accordance with the present invention. For instance, the aforementioned bag 12 may, instead of being constructed from woven marine-grade f bric, be constructed of any material suited to the relevant function of being collapsible and fillable. For example, canvas, hessian or polypropylene may be used as the material for constructing the bag 12.

[0047] In addition, for ease of representation and description, the illustrated underwater elongate structure 10 is a pipeline. It will be appreciated, however, that the present invention is adaptable for use with chains, cables and numerous other underwater elongate structures that require span rectification and/or support.

[0048] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.