Patent Application
20180245302
This invention is in the field of anchoring systems. In particular, the invention relates to submerged anchoring systems and methods.
There is a need for anchoring systems to provide anchoring in soft ocean floors. A variety of tools are known, some of which rely upon suction to hold an anchor in the sea floor. For example as disclosed in US Publication No. 2012/0024535 discloses underwater wellhead closure systems that include a template having first and second anchoring ports and that is secured to a floor of a body of water. A suction pile having a cylindrical body with a head portion and an open bottom is coupled to the first anchoring port, such that the suction pile provides additional hold down force to the template. The system also includes a suction cap coupled to the second anchoring port, and has a cylindrical body with an open bottom and a head portion having at least one suction pump.
There is provided an anchoring system having plural water tubes, each water tube defining a longitudinal channel, each longitudinal channel having an open end and a closed end opposite to the open end, a connecting structure maintaining the plural water tubes in rigid relation to one another, and each water tube of the plural water tubes extending from the connecting structure at least in a first direction, the longitudinal channels extending in the first direction from the respective open ends to the respective closed ends.
In various aspects, there may be included any one or more of the following features: the connecting structure may comprise a cap. There may be a skirt extending in the first direction from the cap, for example along the full length of the skirt. There may be a suction element and a suction flow channel through the cap defined by the suction element or defined by the cap and connected to the suction element. There may be an additional flow channel through the cap and a valve controlling flow through the additional flow channel. There may be a suspension element connected to the connecting structure. There may be respective walls at the closed ends of the longitudinal flow channels, the flexible walls comprising a material selected to withstand undersea pressure, and each flexible wall separating the respective longitudinal flow channel from a respective air chamber to maintain a pressure differential in use of the anchoring system.
There is also provided a ballasting unit having a housing open at a first end, a flexible wall separating the first end of the housing from a second end to define an air chamber at the second end, the flexible wall comprising a material selected to withstand undersea pressure, and to maintain a pressure differential in use of the ballasting unit.
According to an aspect, an anchoring system may be configured to be installed on a bottom of a body of water, the bottom of the body of water being formed of a bottom material. The anchoring system may comprise: a tube sheet that may have a top side and a bottom side; an access tube may define a flow channel through the tube sheet from the top side to the bottom side; and a plurality of water tubes may pass through the tube sheet. The anchoring system may be cylindrical.
Each of the plurality of water tubes may define a longitudinal channel from the top side to the bottom side of the tube sheet. Each longitudinal channel may comprise an open end at the top side and a closed end below the bottom side. A plurality of flow channels may pass through the tube sheet from the top side to the bottom side. A skirt may extend from the bottom side of the tube sheet and may define a volume within the skirt below the tube sheet encompassing at least a portion of the water tubes and the flow channels.
The anchoring system may further comprise a shock absorber that may be coupled to the closed end of at least one of the plurality of water tubes. The shock absorber may comprise an air chamber. The air chamber may comprise at least one flexible wall configured to withstand undersea pressure and may maintain a pressure differential between the longitudinal flow channel and the air chamber. The at least one flexible wall may comprise a neoprene material. A cylinder may have the at least one flexible wall closing the closed end longitudinal channel. The shock absorber may withstand pressures in excess of 20,000 PSI. The shock absorber may be rounded at a bottom end to facilitate penetration into the bottom material.
The anchoring system may further comprise an excavation pump operatively coupled to the access tube on the top side of the tube sheet. The excavation pump may transfer at least a portion of the bottom material from the bottom side to the top side of the tube sheet.
The anchoring system may further comprise at least one valve port fluidly coupled to the plurality of flow channels. The plurality of flow channels may be located near an edge of the tube sheet and an edge of the skirt. The at least one valve port may be configured to remove water, the bottom material, and a combination of water and the bottom material from the volume of the skirt. An injected material may be injected into the at least one valve port and deposited within the volume of the skirt. The injected material may comprise barite mud.
The anchoring system may further comprise a reinforcement structure coupled to the skirt. The reinforcement structure may resist lateral motion and maintains the position of the skirt.
According to an aspect, there is provided a method of installing an anchoring system on a bottom of a body of water, the bottom of the body of water being formed of a bottom material. The method may comprise submerging the anchoring system and lowering the anchoring system until a bottom of a skirt rests on the bottom of the body of water. The skirt may define an inner volume with the bottom of the body of water. The method may comprise pumping, using an excavation pump, the bottom material from the inner volume through an access tube to produce a negative pressure within the inner volume. The negative pressure may be configured to pull the anchoring system beneath the bottom of the body of water. The method may comprise continuing to pump the bottom material from the inner volume until the bottom of the skirt reaches a solid substrate. The method may comprise injecting a mud denser than the bottom material into the inner volume using one or more flow channels. The method may comprise dissipating lateral motion, vertical motion, and a combination of lateral and vertical motion of the anchoring system using a plurality of shock absorbers on a bottom end of a plurality of water tube within the skirt.
The method may further comprise stabilizing the anchoring system with a reinforcement structure. The mud may comprise barite.
According to an aspect, there is provide a method of removing an anchoring system installed on a bottom of a body of water, the bottom of the body of water being formed of a bottom material. The method may comprise providing suction to at least one flow channel to withdraw a mud denser than the bottom material from a skirt defining an inner volume of the anchoring system, the skirt in contact with a solid substrate of the body of water. The method may comprise pumping water through an access tube to produce a positive pressure within the inner volume of the anchoring system causing the skirt to lift from the solid substrate of the body of water. The method may comprise continuing to pump water into the inner volume until the anchoring system becomes free from the bottom of the body of water. The method may comprise lifting the anchoring system from the bottom of the body of water.
While the invention is claimed in the concluding portions hereof, example embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:
The aspects described herein may serve as a mooring system in areas of the ocean, rivers, and/or other bodies of water where poor anchorage or holding ground exists. In particular, the aspects herein may be particularly applicable to sandy or silt ocean floor such as the Gulf of Mexico. The aspects herein may be used as a ballasting system in emergency procedures where a blowout has occurred in a deep sea oil field. The aspects herein may be constructed to conform to one or more requirements of a subsea structure for applications such as ballasting or anchoring. Some examples include: hydraulic valve systems, drilling systems, and/or excavation equipment.
As shown in
A mud or excavation pump 48 may be mounted at the top of the center access tube 12 in order to excavate mud, silt, and/or sand from the underside of the tube sheet 14. The excavation may cause the core anchor system 10 to become submerged in the ocean floor/substrate. When the anchor system unit 10 has reached a desired depth, the excavation pump 48 may be removed and replaced with a flange cap 46.
The tube sheet 14 may maintain the one or more water tubes 16 in rigid relation to one another. The hollow water tubes 16 may extend through and downward from the tube sheet 14. The water tubes 16 may define longitudinal channels from a top of the tube sheet 14 to a bottom of the tube sheet 14. The water tubes 16 may be located at precise locations in order to balance the tube sheet 14. The water tubes 16 may be constructed from steel and may be seal-welded into the tube sheet 14. Alternatively, the water tubes 16 may be fitted with collars and bolted into place.
According to the aspect presented in
As seen in
According to the aspects presented in
Turning to
The shock absorbers 60 may comprise an outer housing 36. A flexible wall 38 may separate an air chamber 40 within the housing 36 from seawater admitted through an opening 42. The flexible wall 38 may take the form of the bottom 30 of the neoprene cylinder. The air chamber 40 may provide a cavity for expansion of the neoprene cylinder. The neoprene cylinder may be suitable for pressures in excess of 20,000 PSI. When the shock absorbers 60 cap the bottom ends 30 of the water tubes 16, a rounded housing 36 may aid penetration of the water tubes 16 into the mud.
The shock absorber 60 may be placed on the water tubes 16 when the core unit 10 functions as a mooring device for a vessel or structure floating on the ocean surface and subjected to energy created through wave action. If a lateral or vertical force is applied to the core unit 10 (e.g. through severe wave action), the core unit 10 may undergo a jarring effect against the water column. The shock absorber 60 may dissipate the energy by having the air and neoprene compress without causing damage.
The flexible wall 38 of the shock absorber 60 may be selected to be of a stiffness such that the shock absorber 60 may be moved by pressures encountered when deployed but may not fully collapse the air chamber 40 at an intended depth of use. The pressure of the overlying water on the flexible wall 38 of the shock absorber 60 may act to resist changes in attitude of the core anchor system unit 10 and exposed to the overlying water through the longitudinal channels of the water tubes 16. If the density of the substrate material surrounding the core unit 10 is inconsistent in density, the shock absorbers 60 may maintain the unit 10 in a vertical position while a lateral force is applied to the core unit 10. The sealed cavity 40 may be at ambient sea level air pressure and may require a non-conductor coating to prevent condensation in the air chamber 40.
In another aspect, the flange cover 46 may not be required when the core anchor system unit 10 acts as a drilling template or as a second layer of safety above a blowout preventer on an oil well. The unit 10 and center tube 12 may be large enough to accommodate a superstructure which would, in turn, may support a hydraulically operated knife gate valve with the capacity to sever steel. The center access tube 12 may extend downward to a point where the tube 12 may form a seal in the substrate. The diameter of the tube 12 may be large enough to accommodate a standard riser pipe. The entire structure may be locked in place by the weight of the above water column.
When the core anchor system unit 10 is deployed having the pump 48, the core anchor system unit 10 may be connected by one or more hydraulic lines 54 to a hydraulic manifold system 52. The hydraulic manifold system 52 may be situated either on board a surface vessel or may be placed on the bed, bottom, substrate, or floor 50 of a body of water, such as the sea, ocean, river or lake. The particular arrangement may be selected based on the field conditions and the particular use of the core anchor system unit 10. The hydraulic manifold system 52 may be charged from a single source (not shown) located onboard a surface vessel (not shown). Hydraulic fluid may be directed under pressure to the core anchor system unit 10 to a point where the hydraulic fluid may open or close one of the individual valve ports 22 or power a motor (not shown) of the pump 48.
The hydraulic pump 48 and the valve ports 22 may be employed in the course of submerging the core anchor system unit 10 in the floor 50 and injecting mud. Once the core anchor system unit 10 is in position, the hydraulic manifold system 52 and the pump 48 may be removed to be used on another core anchor system unit 10. If the core anchor system 10 is to be removed, the hydraulic manifold system 52 and the pump may be reattached to the core anchor system unit 10 and water may be pumped below the tube sheet 14.
According to some aspects, the flange cover 46 may comprise two valve ports 22. One port 22 may have a check valve between approximately 2-inches to 4-inches in diameter. The other port 22 may have a small gate valve of the same size. Both valves may facilitate the injection of barite mud and/or the extruding of water. These gate valves 22 may be operated mechanically by remotely operated vehicles (ROVs). The a core anchor system unit 10 may comprise attachments to accommodate a remote-operated vehicle (ROV) attached in a similar manner as the flange cover 46 shown in
When the core anchor system unit 10 is used as a blowout preventer, one hydraulic knife gate may be used to sever a defective pipe portion. The dimensions of this valve may be approximately 5-feet to 6-feet in diameter and may weight approximately 1000-lbs or more.
According to aspects herein, the core anchor system unit 10 may be submerged in order to rest on the ocean floor. The anchor system unit 10 may be suspended to deploy and/or retrieve the anchor system unit 10 using the center access tube 12. The center access tube 12 may be used to provide suction or injection of material to assist in sinking or raising the anchor system unit 10 into or from a substrate 50 of an ocean, a river, and/or a lake. The center access tube 12 may provide both a suspension element and a suction element.
The excavation pump 48 may then be enabled to pump water, mud, silt, sand, and/or other material from the ocean floor through the center access tube 12. By pumping this material through the center access tube 12, a buoyancy of the core anchor system unit 10 may be moved to a lower position and one or more hydrostatic forces push the tubes 16 into the ocean floor. The stability of the unit 10 may be maintained by the hydrostatic force. An excavation of the mud, silt, and/or sand may cause the core anchor system unit 10 to become completely submerged in the substrate 50.
Once the core anchor system unit 10 has reached a desired depth, the excavation pump 48 may be removed and the center access tube 12 may be capped. When deployed as a mooring device, the flange cover 46 may be fastened to the center access tube 12 of the core anchor system unit 10 after being submerged in the substrate 50. The flange cover 46 may be fitted with two valve ports 22, a check valve, and a gate valve. The gate valve allows dense mud to be pumped into the center tube 12 while the check valve allows water to be forced out of the capped access of the center access tube 12 as gate valve fills with the injected mud (e.g. barite).
After the unit 10 is pushed down to the desired depth, the unit 10 may be positioned vertically. The unit 10 may be submerged to a depth in the ocean substrate where an aggregate material of the ocean floor may be compacted and becoming solidified. This process involves no pounding of piles in any part of the deployment process. In some aspects, the top of the unit 10 may be submerged in mud, sand, or a combination of both mud and sand.
The core anchor system unit 10 displaces the water by volume and therefore, the core anchor system 10 may experience buoyancy on an underside surface area of the tube sheet 14 and the skirt 18. In order to counteract this effect, each water tube 16 extending below the tube sheet 14 lowers a center of gravity of the anchor system unit 10. Also, a portion of the underside surface area of the tube sheet 14 may be transferred down deep into compacted substrate material of the ocean. By lowering the center of gravity and transferring the underside surface area to a deeper position, the buoyancy may have a lesser effect on the portion of the core anchor system 10 remaining at the surface of the substrate. The water tubes 16 may leave a small water-filled cavity on the underside of the tube sheet 14, between the outer walls of the water tubes 16 and the skirt 18.
When a seal could be formed underneath the skirt 18 and the compacted ocean substrate, the remaining water present underneath the skirt 18 may be extruded through check valves by injecting fine ground heavy mud (e.g. barite) underneath the skirt 18. To remove a majority of the buoyancy effect and hold the anchor system unit 10 in place, material with a higher density than the naturally deposited substrate material may be injected along an interior wall of the skirt 18 using the flow channels 24. By injecting material with the higher density, water may be forced out from underneath the skirt 18 using one or more check valves. Through removal of the water under the skirt 18, a continuity of the water column may be interrupted sufficiently so as to cause a pressure imbalance which would in turn, lock the core unit 10 and any attached superstructure in place. The injected material, e.g. barite, may be mixed with water only to a degree which may produce a viscosity to facilitate pumping or mixed with water only to a consistency which would permit pumping.
The process may be reversed to remove the core anchor system unit 10. The buoyancy may be restored by injecting water through the flow channels 24.
Turning to
The stabilizing reinforcement structure 800 provides a reinforcement and stabilizing effect. For example, a mooring unit 10 may be deployed at a depth of approximately 1-km and having a 35-feet height in order to reach the compacted substrate material. In this case, the skirt 18 needs to be approximately 35-feet in height in order to reach down to compacted substrate material. For the sake of stability and considering the ocean environment, if the skirt 18 were to be 35 feet in height, the tube sheet 14 may have a diameter of at least 25-feet. The hydrostatic pressure at a 1-km depth may be over approximately 1450-lbs per sq. inch. The square footage of the tube sheet 14 combined with the added pressure caused by the transfer of portions of the tube sheet 14 by the water tubes 16, may cause excessive total pressure exerted on the unit 10. In order to compensate for this excessive total pressure, the reinforcement structure 800 allows for the unit 10 having a small calculated, diameter tube sheet 14, while having an overall diameter that may be stable for the desired height of the unit 10.
The stabilizing reinforcement structure 800 may also permit the core anchor system unit 10 to remain stable as the barite is pumped into the core anchor system unit 10. The reinforcement structure 800 may resist lateral pressure and/or collapse while the pressure inside the unit 10 is neutral or above neutral during mud injection and water removal. For example, the stabilizing reinforcement structure 800 may support the anchor system unit 10 if the continuity of the water column is interrupted before the mud is sufficiently pressurized and compacted. The reinforcement structure 800 may also support the anchor system unit 10 while the mud compacts slowly as the mud settles due to gravity. The reinforcement structure increases the surface area in order to produce additional friction to resist lateral motion during suction.
Along an edge opposite to the edge welded to the skirt 18, a strengthening flange 804 may be welded to the rib 802. The strengthening flange 804 may minimize listing of the core anchor system unit 10. The flange 804 may be curved with a radius of curvature similar to that of the skirt 18 and may extend the length of the skirt 18. In this aspect, the flange 804 may be centrally attached to the edge of the rib 802. In other aspects, the flange 804 may be integrally formed from the rib 802 by bending the edge of the rib 802.
One or more rings 806 may be welded to the flanges 804. The rings may have a radius of curvature similar to that of the skirt 18. In this aspect, three rings 806 are present with one on each end of the core anchor system unit 10 and one centrally located along the unit 10. The three rings 806 enable material surrounding reinforcement structure 800 to flow toward the perimeter of the core unit 10 and tighten around the skirt 18 of the unit 10.
Although the aspects shown herein demonstrate the center access tube 12 not extending below the tube sheet 14, in other aspects, the center access tube 12 may extend below the tube sheet 14. For example, the center access tube 12 may extend to the bottom end of the water tubes 16 or to the level of the bottom of a skirt or shell casing 18 for aspects having a skirt 18.
Although the shock absorbers 60 shown herein demonstrate a rounded housing 36, other aspects may have different shaped housings 36 to assist in penetration of the water tubes 16 into the mud.
Although the aspects herein demonstrate using the center access tube 12 for positioning the core anchor system unit 10, other aspects may provide separate elements for positioning. For example, a suspension element (not shown) may deploy and/or retrieve the anchor system unit 10.
Although particular dimensions, reinforcements, and/or stabilizer requirements may be described herein, these attributes may be adjusted based on the ocean depth, field conditions, and/or an intended use of the core anchor system unit 10. Although particular proportions may be demonstrated in the drawings, the proportions may be adjusted based on the ocean depth, field conditions, and/or the intended use of the core anchor system 10. The aspects presented herein operate similar to conventional anchors with generally smaller dimensions. For example, conventional anchors have dimensions of between 6-20 meters in diameter and lengths of 30 meters or more.
For example, the conventional suction anchor having dimensions of 30-feet in height and a diameter of 20-feet provides approximately 3786 square feet of surface area which would produce suction and friction between the anchor and the surrounding ocean substrate. In an example aspect herein having the same overall volume and dimensions (e.g. height of 30 feet and a diameter of 20 feet) the core anchor system unit 10 may have a surface area of 5652 square feet (excluding outer stabilizers and reinforcement) providing friction and suction at the interface between the unit 10 and the ocean substrate. When the surface area of the water tubes 16 plus the center access tube 12 are calculated, the additional surface area may provide suction and friction may be 1884 square feet.
Additionally, conventional anchors may require complete submersion in the substrate. In the aspects herein, the core anchor system unit 10 may only be submerged only to a point in the substrate where the aggregate material is sufficiently compacted in order to form a seal by injecting finely ground barite mud.
According to some aspects, the a core anchor system unit 10 may permit a number of structures to be attached, separate and apart from simple mooring lines. For example, several core units 10 may be held together by a superstructure to form a secure platform placed above or on the mud-filled substrate. In one example, the core units 10 may support a wind turbine that may be erected with minimal environmental impact in a cost effective manner.
Although the aspects herein describe a generally cylindrical core anchor system unit 10, other aspects may comprise different shapes, such as for example, a rectangular prism.
Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.
In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.
| Number | Date | Country | |
|---|---|---|---|
| 62294290 | Feb 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15429768 | Feb 2017 | US |
| Child | 15964996 | US |
