WATER

Field of the Invention

The present disclosure relates to systems and methods for installing structures in a body of water, for example structures subject to increasing ambient pressures at increasing water depths.

Background of the Invention

In order to increase the buoyancy of subsea structures and/or to insulate the structure from the ambient water temperature, a foam may be applied to the exterior. Generally, a polyolefin foam, for example, polyethylene may be used in depths up to about 100 meters for buoyancy or insulation applications. A polyurethane foam may also be used in depths up to about 100 meters. Co-polymer foams can be used at depths up to 600 or even up to 1000 meters. Syntactic foams are used for installation and buoyancy applications in deeper waters. Syntactic foams are manufactured by placing microspheres of hollow glass or other materials in a polymer matrix. Syntactic foams can be used at depths up to 3000 meters, up to 4000 meters, or more. Generally, foams and some other materials are compressed as they are lowered into water and the ambient pressure increases. Structures that are installed exterior to the foam may fit around the foam perfectly at the surface, but when the foam shrinks in the water, a gap appears between the structure and the foam.

Co-pending patent application publication WO 2008/144410, having attorney docket number TH3254, discloses a system comprising a structure defining an interior of the system; an apparatus exterior to the structure, the apparatus adapted to reduce in size when lowered into a body of water; a strap exterior to the apparatus, the strap adapted to reduce in size as the apparatus reduces in size. Patent Application WO 2008/144410 is herein incorporated by reference in its entirety.

Co-pending patent application PCT/US2009/031503, having attorney docket number TH3244, discloses a system comprising a subsea structure defining an interior of the system, the structure subject to a water current; at least one line exterior to the structure; a collar exterior to the structure adapted to maintain the at least one line adjacent to the structure; and a vortex induced vibration suppression device exterior to the at least one line and the collar. Patent Application PCT/US2009/031503 is herein incorporated by reference in its entirety.

U.S. Patent Number 7,195,530 discloses system comprising a structure in a body of water, wherein the body of water comprises a depth comprising a top-section from a surface of the body of water to one-third of the depth, and a second- section from one-third of the depth to two-thirds of the depth, a first buoyant apparatus attached to the structure in the top- section of the depth, a second buoyant apparatus attached to the structure in the second-section of the depth, wherein the second buoyant apparatus provides a second buoyancy effect average per length of the structure at least 30% less than a first buoyancy effect average per length of the structure provided by the first buoyant apparatus. U.S. Patent Number 7,195,530 is herein incorporated by reference in its entirety. There is a need in the art for systems and/or methods to efficiently install structures in a body of water. There is a need in the art for systems and/or methods to compensate for the shrinkage of foam on the exterior of a structure .

Summary of the Invention One aspect of the invention provides a system comprising a structure defining an interior of the system; an apparatus exterior to the structure, the apparatus adapted to reduce in size when lowered into a body of water; a strap exterior to the apparatus, the strap adapted to reduce in size as the apparatus reduces in size, the strap comprising a first end and a second end; and a connector assembly connected to the first end and the second end, the connector assembly comprising a bolt, a biasing mechanism adapted to keep a level of tension on the strap, a limiter adapted to ensure a minimum length of the biasing mechanism.

Another aspect of the invention provides a method of installing a structure in a body of water comprising attaching an apparatus exterior to the structure; attaching a strap exterior to the apparatus, the strap comprising a mechanism adapted to keep a tension on the strap, and a limiter to control a length of the mechanism; lowering the apparatus and strap into the body of water; and wherein the apparatus has a reduction in volume due to an ambient water pressure in the body of water, and the strap has a corresponding reduction in length to compensate for the apparatus reduction in volume. Advantages of the invention include one or more of the following :

Systems and/or methods to more efficiently install structures in a body of water; and/or Systems and/or methods to compensate for the shrinkage of foam on the exterior of a structure. Brief Description of the Figures

Figure 1 illustrates a subsea structure system.

Figure 2 illustrates a top elevational view of a collar.

Figure 3 illustrates a cross sectional view of the connector assembly of Figure 2 in a compressed configuration.

Figure 4 illustrates a cross sectional view of the connector assembly of Figure 2 in an expanded configuration. Detailed Description

Figure 1 : Referring now to Figure 1 there is illustrated offshore system 100. System 100 includes surface structure 102 near a water surface. Surface structure 102 is connected to subsurface structure 103 adjacent to seafloor 108 by a tubular structure 104. In some embodiments, tubular structure 104 may be a riser. Exterior to riser 104 is buoyancy material 106, such as a foam, which may serve to insulate and/or provide buoyancy to riser 104. The water has current 110, which may cause vortex-induced vibration (VIV) of riser 104 and buoyancy material 106. To counter VIV, VIV suppression devices 114 may be installed along the length of riser 104. VIV suppression devices may be any type of device suitable for suppressing VIV. Representatively, VIV suppression devices may be fairings, smooth sleeves, multiple-sided suppression devices or the like. Suitable VIV suppression devices may be made of any one of numerous materials including, but not limited to, thermoplastics, fiberglass and metals.

Collars 112 are further installed about riser 104 and between VIV suppression devices 114 to keep VIV suppression devices 114 from moving along the length of riser 104. Representatively, collars 112 may be load-bearing collars installed when riser 104 is being initially deployed from a floating drilling unit.

As riser 104 is lowered through the water, buoyancy material 106 decreases in size due to ambient pressure increase. This in turn decreases the diameter of buoyancy material 106 around which collars 112 are positioned. Thus, collars 112 must be able to compensate for these size changes so that they do not loosen as the diameter decreases and slide along the length of riser 104. Other environments also encounter situations where the outside diameter of a structure may increase and/or decrease. Such situations are contemplated for the use of this invention which can alternatively increase and/or decrease the diameter of a collar to compensate for these size changes of the structure.

Figure 2 :

Figure 2 illustrates a top elevational view of a collar having a modifiable diameter to accommodate changes in the size of the underlying structure. Collar 212 is formed by body 230 having dimensions suitable for positioning collar 212 around a riser or other offshore structures and buoyancy material attached thereto. Collar 212 may be made of any strong, corrosion resistant material suitable for supporting a fairing or other VIV suppression devices, including but not limited to a high density polyethylene, thermoplastics such as delrin®, fiber-reinforced polymers such as fiberglass and metals. In still further embodiments, collar 212 may be made of an antifouling material such as copper to prevent marine growth. Collar 212 may be extruded or molded or otherwise formed from the desired material. Body 230 may optionally be divided into two sections 230a and 230b. Sections 230a and 230b may be positioned around opposite sides of the buoyancy material and then connected at their ends to hold body 230 in place. Representatively, sections 230a and 230b may be connected at one end with hinge 232 and at another end with connector assembly 216. In this aspect, body 230 may be opened to position body 230 around the buoyancy material and then closed around the buoyancy material to secure body 230 to the riser and buoyancy material. Figure 3:

Referring now to Figure 3, a diameter of collar 212 may be modified to compensate for compression of the underlying buoyancy material using connector assembly 216. In this aspect, connector assembly 216 may be spring loaded so that a diameter of collar 212 changes without user intervention along with the underlying structure (for example a buoyancy material 106 (see Figure 1) moving through depths of a subsea environment with changing pressures) . Connector assembly 216 may further be dimensioned to allow for control of the spring length to prevent over and/or under tightening of collar 212. In this aspect, connector assembly 216 may include bolt 222 which passes through stops 220a and 220b attached to ends of sections 230a and 230b opposite hinge 232. Bolt 222 may be any type of bolt suitable for securing sections 230a and 230b of collar 212 together as described herein. In some embodiments, bolt 222 may be a 13 inch bolt with 7 inch threading. Washer 226 may be positioned adjacent the bolt head and spring 302 may be positioned around bolt 222 between washer 226 and stopper 220a. Limiter tube 224 is further positioned around bolt 222 and spring 302 to control a length of the spring. In this aspect, limiter tube 224 may have any dimension suitable for setting a desired length of the spring. Representatively, in one embodiment, limiter tube 224 is a hollow, cylindrical tube having openings at both ends. In some embodiments, limiter tube 224 may have a tubular body with open ends having interior diameters dimensioned to fit around spring 302. In this embodiment, washers may be placed around bolt 222 at opposite ends of limiter tube 224 to facilitate positioning of limiter tube 224 between the bolt head and stop 220a. In other embodiments, limiter tube 224 may include a capped end and a tubular body having an interior diameter dimensioned to slidably fit around bolt 222. The opposite end and body of limiter tube 224 may have a larger opening to allow limiter tube 224 to slide over spring 302. It is contemplated that limiter tube 224 may be separate from collar 212 or attached to stopper 220a of collar 212 at one end. Limiter tube 224 may be made of any strong, corrosion resistant material, including but not limited to, a high density polyethylene, thermoplastics such as delrin®, fiber-reinforced polymers such as fiberglass or metals such as aluminum or stainless steel.

During installation, washer 226 is first positioned around bolt 222 near the bolt head, followed by spring 302 and limiter tube 224. The free end of bolt 222 is then inserted through openings in stop 220a and 220b. In one embodiment in which the spring may decrease the diameter during the operation, bolt 222 may be tightened using primary nut 228 so that washer 226 hits limiter tube 224 and compresses the spring to a length of limiter tube 224. Since the spring cannot be compressed beyond a length of limiter tube 224, over tightening of bolt 222 is prevented. In this aspect, the length of limiter tube 224 is such that over or under tightening of bolt 222 is prevented.

In another embodiment in which the spring may increase and/or decrease the diameter during the operation, bolt 222 may be tightened using primary nut 228 so that washer 226 has a gap between limiter tube 224 and spring 302 is connected to stop 220a and washer 226 so that spring 302 is in tension is biased to increase the diameter of collar 212, until limiter tube 224 encounters washer 226. As the diameter of collar is increased, washer 226 compresses the spring 302 to a length of limiter tube 224. Since the spring cannot be compressed beyond a length of limiter tube 224, a maximum diameter of collar can be set. When spring 302 is in compression, it is biased to decrease the diameter of collar 212 and create a gap between the washer 226 and limiter tube 224.

Representatively, in some embodiments, limiter tube 224 has a length of about 3 inches to 5 inches. For example, limiter tube 224 may have a length of from 2 inches to 6 inches or from 3.5 inches to 4.5 inches. Once bolt 222 is tightened to the desired length, secondary jam nut 229 may be inserted over the end of bolt 222 and tightened against primary nut 228 to lock primary nut 228 in place.

Components of connector assembly 216 (e.g., bolt 222, washer 226, nuts 228, 229, limiter tube 224, etc.) may be made of materials including, but not limited to, thermoplastics, fiberglass and metals.

Figure 3 illustrates a cross sectional view of the connector assembly of Figure 2 in a compressed configuration. Spring 302 is shown in Figure 3 compressed within limiter tube 224. Spring 302 may be any type of spring and be made of any type of material suitable for modifying a diameter of collar 212 as described herein. In one embodiment, spring 302 may be obtained from materials commercially available from Mearthane Products Corporation under the model number DS-390A Ether Type MDI Urethane. It is further contemplated that spring 302 may be made of materials including, but not limited to, thermoplastics, fiberglass and metals such as stainless steel or aluminum. In some embodiments, spring 302 is about 5 inches to 7 inches in its uncompressed, natural state. For example, spring 302 in its uncompressed state is 4 inches to 8 inches or from 5.5 inches to 6.5 inches.

To compress spring 302 to the desired length, primary nut 228 at the end of bolt 222, having washer 226, spring 302 and limiter tube 224 thereon, may be tightened until washer 226 contacts the end of limiter tube 224. Such tightening compresses spring 302 to the length of limiter tube 224. This in turn tightens collar 212 around the underlying riser to prevent it from moving along the length of the riser. As previously discussed, in some embodiments, limiter tube 224 has a length of about 3 inches to 5 inches. In this aspect, spring 302 in its compressed state has a length of about 3 inches to 5 inches. Secondary jam nut 229 is then further tightened along bolt 222 until it reaches primary nut 228. Figure 4 : Figure 4 illustrates a cross sectional view of the connector assembly of Figure 2 in an expanded configuration. In this embodiment, spring 302 is expanded from the compressed state shown in Figure 3 and therefore extends out an end of limiter tube 224. Expansion of spring 302 as shown in Figure 4 occurs when the buoyancy material around which collar 212 is positioned contracts due to the pressure increase that occurs as the riser is lowered through the water. In particular, spring 302, which is compressed between washer 226 and stop 220a, biases sections 230a and 230b of collar 212 together thereby tightening collar 212 around the underlying riser. When the riser is lowered into the water, the buoyancy material around the riser contracts which in turn decreases a diameter of the surface around which collar 212 is positioned. This allows spring 302 to expand along bolt 222. Bolt 222 is slidably positioned through stops 220a and 220b such that expansion of spring 302 pulls bolt 222 further through stop 220a which in turn forces the ends of sections 230a and 230b toward one another. As the ends of sections 230a and 230b move toward one another, the diameter of collar 212 decreases to accommodate the size of the underlying surface (e.g. riser with buoyancy material thereon) to ensure collar 212 is held tightly around the surface. In this aspect, connector assembly 216 allows the diameter of collar 212 to be automatically adjusted as the size of the underlying buoyancy material changes. While VIV suppression devices such as fairings are described, it is contemplated that the embodiments described herein may further be used in connection with other types of VIV suppression devices.

Illustrative Embodiments:

In one embodiment, there is disclosed a system comprising a structure defining an interior of the system; an apparatus exterior to the structure, the apparatus adapted to reduce in size when lowered into a body of water; a strap exterior to the apparatus, the strap adapted to reduce in size as the apparatus reduces in size, the strap comprising a first end and a second end; and a connector assembly connected to the first end and the second end, the connector assembly comprising a bolt, a biasing mechanism adapted to keep a level of tension on the strap, a limiter adapted to ensure a minimum length of the biasing mechanism. In some embodiments, the structure is in a body of water, further comprising a vessel connected to the structure, wherein the vessel is floating in the body of water. In some embodiments, the structure is selected from the group consisting of an oil or gas flowline, an oil or gas export line, a pipeline, a riser, and a steel tubular. In some embodiments, the apparatus comprises a polymeric foam. In some embodiments, the system also includes a polymeric skin exterior to the foam. In some embodiments, the structure comprises a plurality of sections welded to each other. In some embodiments, the structure comprises a plurality of sections threaded and/or clamped to each other. In some embodiments, the apparatus comprises foam having a thickness of at least 10 cm. In some embodiments, the biasing mechanism comprises a spring. In some embodiments, the limiter comprises a tube, and the biasing mechanism is located within the tube.

In one embodiment, there is disclosed a method of installing a structure in a body of water comprising attaching an apparatus exterior to the structure; attaching a strap exterior to the apparatus, the strap comprising a mechanism adapted to keep a tension on the strap, and a limiter to control a length of the mechanism; lowering the apparatus and strap into the body of water; and wherein the apparatus has a reduction in volume due to an ambient water pressure in the body of water, and the strap has a corresponding reduction in length to compensate for the apparatus reduction in volume. In some embodiments, the reduction in volume of the apparatus is at least about 0.1%. In some embodiments, the reduction in volume of the apparatus is at least about 0.5%. In some

ll embodiments, the reduction in volume of the apparatus is at least about 1%. In some embodiments, the reduction in length of the strap is at least about 0.1%. In some embodiments, the reduction in length of the strap is at least about 0.5%. In some embodiments, the reduction in length of the strap is at least about 1%. In some embodiments, the method also includes a skin or a pipe exterior to the apparatus, the skin adapted to provide additional strength to the apparatus. In some embodiments, at least a portion of the structure rests on a bottom of the body of water. In some embodiments, the strap is adapted to hold the apparatus about the structure. In some embodiments, the apparatus comprises one or more foam modules. In some embodiments, the strap is adapted to hold a second apparatus about the apparatus and the structure. In some embodiments, the second apparatus comprises a vortex induced vibration and/or drag suppression device, for example a strake or a fairing.

Collars may be used to hold fairings. Alternatively, fairings may be replaced with strakes, shrouds, wake splitters, tail fairings, buoyancy modules, or other devices as are known in the art. Suitable sleeves, suitable collars, and suitable devices to install exterior to structures, and methods of their installation are disclosed in U.S. Patent Application Publication Number 2006/0021560, having attorney docket number TH1433; U.S. Patent Number 7,406,923, having attorney docket number TH0541; U.S. Patent Application Publication Number 2006/0280559, having attorney docket number TH2508; U.S. Patent Application Publication Number 2007/0003372, having attorney docket number TH2876; U.S. Patent Application Publication Number 2009/0242207, having attorney docket number TH2969; U.S. Patent Application Number 12/305,212, having attorney docket number TH1500; U.S. Patent Application Number 12/515,911, having attorney docket number TH3112; U.S. Patent Application Number 12/515,922, having attorney docket number TH3190; U.S. Patent Number 5,410,979; U.S. Patent Number 5,410,979; U.S. Patent Number 5,421,413; U.S. Patent Number 6,179,524; U.S. Patent Number 6,223,672; U.S. Patent Number 6,561,734; U.S. Patent Number 6,565,287; U.S. Patent Number 6,571,878; U.S. Patent Number 6,685,394; U.S. Patent Number 6,702,026; U.S. Patent Number 7,017,666; and U.S. Patent Number 7,070,361, which are herein incorporated by reference in their entirety.

Suitable methods for installing fairings, collars, and other devices to install exterior to structures, are disclosed in U.S. Patent 7,578,038, having attorney docket number TH1853.04; U.S. Patent Application Publication Number 2005/0254903, having attorney docket number TH2463; U.S. Patent Application Publication Number 2008/0056828, having attorney docket number TH2900; U.S. Patent Application Publication Number 2007/0125546, having attorney docket number TH2926; U.S. Patent Application Publication Number 2007/0140797, having attorney docket number TH2875; U.S. Patent Application

Publication Number 2010/0014922, having attorney docket number TH2879; U.S. Patent Application Number 12/442,015, having attorney docket number TH2842; U.S. Patent Number 6,695,539; U.S. Patent Number 6,928,709; and U.S. Patent Number 6,994,492; which are herein incorporated by reference in their entirety.

The collars and/or fairings may be installed on the tubular member (e.g. buoyancy material and riser) before or after the tubular member is placed in a body of water.

The collars, fairings and/or other devices exterior to the structure may have a clamshell configuration, and may be hinged with a closing mechanism opposite the hinge, for example a mechanism that can be operated with an ROV.

Collars and/or fairings may be provided with copper plates on their ends to allow them to weathervane with adjacent fairings or collars. Collars and/or fairings may be partially manufactured from copper.

Those of skill in the art will appreciate that many modifications and variations are possible in terms of the disclosed embodiments, configurations, materials and methods without departing from their spirit and scope. Accordingly, the scope of the claims appended hereafter and their functional equivalents should not be limited by particular embodiments described and illustrated herein, as these are merely exemplary in nature.