FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to protection for marine installations and infrastructure and, more particularly, but not exclusively, to floating protection for marine installations such as oil and gas industry marine extraction installations including drilling and production platforms.

An oil platform, also referred to as an offshore platform or, oil rig, is a large structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store the product until it can be brought to shore for refining. The platform may have facilities to accommodate the workforce as well.

Depending on the circumstances, the platform may lay on the seabed, may consist of an artificial island, or in deep waters, may be anchored afloat.

The platforms may be of steel or concrete or other materials.

The environmental consequences of accidents on oil platforms can be catastrophic, and safety issues are considered very important.

Specifically, the nature of the operation of the oil platform, relating as it does to extraction of volatile substances sometimes under extreme pressure in a hostile environment— means risk; and accidents and tragedies occur regularly. The U.S. Minerals Management Service reported 69 offshore deaths, 1,349 injuries, and 858 fires and explosions on offshore rigs in the Gulf of Mexico from 2001 to 2010.

In July 1988, 167 people died when Occidental Petroleum's Piper Alpha offshore production platform, on the Piper field in the UK sector of the North Sea, exploded after a gas leak. On April 21, 2010, the Deepwater Horizon platform, 52 miles off-shore of Venice, Louisiana, exploded, killing 11 people. The platform sank two days later. The resulting undersea oil fountain, conservatively estimated to exceed 76,000 m , became the worst oil spill in US history.

Given the importance of gas/oil platforms to the economy, platforms throughout the world are believed to be potential terrorist targets. The publication, Critical Energy Infrastructure Protection Policy Research Series, - Oil Platform Security: Is Canada Doing All It Should? Peter Avis, No. 3 2006 CCISS provides a survey of the dangers to oil platforms of terrorism around the world. Agencies and military units responsible for maritime counterterrorism often train for attempts to attack oil installations by fire from ships or motor boats, or attempts to board and hijack the oil rig. However the platform is itself inflammable, due to the nature of the materials being extracted from the sea. Thus it would be desirable to defeat this kind of attack before it gets near to the oil platform.

SUMMARY OF THE INVENTION

Regardless of the above, one form of terrorist attack is not currently catered for. It is conceivable that a large ship could be hijacked and used to ram an oil rig, or a smaller ship could be sailed under the oil rig to explode. As oil platforms are generally stationary even if they are floating, a ship need merely be set on course to ram the platform the terrorists being able to escape well before the collision.

The present invention may provide a barrier that surrounds the marine installation to be protected, with the purposes of preventing any unauthorized approach to the oil platform and also absorbing the kinetic energy of any vessel attempting to ram the installation. The barrier may lie on the seabed in shallow waters or anchored afloat in deep waters and may also include additional defensive features to protect the installation from surface or underwater attack.

According to an aspect of some embodiments of the present invention there is provided a protection system for a marine installation, comprising a plurality of hull sections joined together to form a closed shape to surround said marine installation.

The embodiments may comprise a closable gate in said closed shape to allow shipping access to said marine installation.

In an embodiment, the hulls are floating hulls.

In an embodiment, the hulls are shaped to dovetail together.

In an embodiment, the hulls are arranged with ballast pumps to provide variable freeboard.

An embodiment may comprise compressed air tank units for rapid reduction of ballast to increase freeboard in an emergency.

In an embodiment, said ballast pumps and said compressed air tank units are controllable to ensure substantially even change of ballast throughout said closed shape.

An embodiment may comprise a deck to allow personnel to patrol said closed shape. In an embodiment, said deck comprises a driveway capable of allowing a patrol vehicle to patrol around said closed shape.

In an embodiment, said deck further comprises a garage for housing said patrol vehicle.

In an embodiment, at least one of said hull sections and an anchor system further comprise strain gauges to assess stresses on said structures or anchors, to allow for reducing the freeboard of the floating protection system for protection against rough weather.

An embodiment may comprise anchors to hold said system in position.

A dynamic positioning unit may help hold said system in position.

The ship hulls may comprise double hulls.

A gap between inner and outer hulls of respective double hulls, may be greater than 60cm.

More particularly the gap may be greater than 60cm, greater than lm, substantially 1.2m or less than 2m.

The hulls may typically comprise bulkheads.

According to a second aspect of the present invention there is provided a hull for arrangement with additional hulls to form a closed shape around a marine installation, the hull configured as a section of a ring, to form said ring when rigidly connected to said additional hulls.

According to a third aspect of the present invention there is provided a floating hull for arrangement with additional hulls to form a closed shape around a marine installation, the floating hull comprising a double hull and having a gap between inner and outer hulls of said double hull exceeding 60cm, and may be more specifically but not exclusively, greater than lm, substantially 1.2m or less than 2m.

According to a fourth aspect of the present invention there is provided a floating hull system comprising a plurality of hulls connected together, said arrangement comprising a ballast management unit configured to provide equalized ballast variation over said system to allow for uniform reduction of freeboard during rough weather.

An embodiment may comprise a plurality of strain gauges distributed over at least one of the group comprising said hulls and anchors, to detect stresses on said hulls and anchors to trigger said uniform reduction of freeboard. According to a fifth aspect of the present invention there is provided a method of providing protection for a marine installation, the method comprising:

providing a plurality of hulls; and

connecting said hulls rigidly together in a closed shape around said marine installation.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a simplified schematic plan view - showing a protection system according to the present embodiments for a marine infrastructure item;

FIG. 2 is a simplified schematic diagram showing the protection system of FIG. 1 in longitudinal view.

FIG. 3A is a simplified schematic diagram showing the protection system of FIG. 1 including a gateway to allow for service traffic;

FIG. 3B is a simplified schematic diagram of the protection system of FIG. 3A where the freeboard has been reduced;

FIG. 4 is a simplified block diagram of a control system for ballasting and deballasting the protection barrier according to an embodiment of the present invention; and FIG. 5 is a cross-section of an individual hull of the protection system of FIG. 1, showing a double hull construction and illustrating the positioning of ballast tanks.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to a protection system for marine infrastructure and, more particularly, but not exclusively, to a protection system for protection of the marine infrastructure from ramming attacks by vessels, or attacks by vessels seeking to explode near or under the platform. The protection system may float, or in shallow water may lie on the sea bed and may consist of elements that contain steel or concrete. The system may comprise a structure that has a closed shape to enclose the infrastructure.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring now to the drawings, Figure 1 illustrates a schematic plan view of a protection system 10 for a maritime installation such as an oil platform 12. The floating protection system is a ring, or other closed shape made up of a multiple hull sections 14.1...14.n connected together. The hulls may float, or when used in shallow water may rest on the sea bed. The closed shape surrounds the installation to be protected and prevents vessels from approaching or ramming the installation. The idea of the closed shape is to strengthen the protection system against structural deformation, and a round - that is a ring shape, is regarded as particularly effective in distributing stresses around the whole of the structure in rough sea conditions and in the event of a collision. Thus the kinetic energy of the attempted collision is absorbed by the entire protection system, which may be ballasted, to increase its mass.

The hulls may be rigidly connected together. The hulls may be shaped to dovetail together to provide a rigid shape that transfers kinetic energy of a collision over the whole structure. In one example the hulls may be constructed with dovetail sections that allow for a hull at a given height to slide into a gap. Then the ballast is adjusted for the hull to slot permanently into place. Adjustable ballast is discussed hereinbelow.

Once dovetailed into position the connection may be reinforced, say by bolts or welding.

As an alternative to dovetailing, the hulls may use corresponding male and female connectors, or any other kind of rigid connection.

As illustrated in Fig. 1 the hulls are built as ring sections. However straight hull sections may be used instead.

Reference is now made to Fig. 2 which illustrates the protection system of claim 1 in longitudinal view over the sea surface. The protection system 10 floats in such a way that its freeboard forms a barrier preventing approach to the installation 12.

The structure may be liberally provided with fenders 16 to absorb impact energy. The fenders may be rubber blocks, rubber rings or any other suitable form of fender.

An oil platform requires constant servicing and thus a way is provided of allowing legitimate maritime traffic to approach the platform. Fig. 3 A is a longitudinal view of a section of the protection system, with the oil platform 12 in the background. A gate 20 in one of the hulls allows for entry of such legitimate traffic.

Typically, the kinds of ships that service oil platforms have a draft of around 4m, so a suitable depth for the gateway may be 6m, to give sufficient clearance.

The gate may be closable to prevent entry of unauthorized vessels. There are numerous ways in which such a gate may be provided. One way is to provide a gate that is opened and closed using hydraulics.

The gate could be a drawbridge style gate that is hinged at its lower end and is raised and lowered from above using chains or cables.

An alternative method for opening and closing a gate is by buoyancy. In one method, the gate is pivoted in between upper and lower tank compartments. Water is pumped to the top compartment to pivot the gate into an open position and is then pumped to the lower section to pivot the gate shut. A variation on the use of buoyancy is to have the gate slide up and down vertically. The gate has compartments to fill and empty with ballast water. The gate floats up to close, or sinks down to open.

A further alternative is to provide a horizontally hinged lock-type gate as commonly used in canal locks or in dry docks. Reference is now made to Fig. 3B, which shows how the protection system of Fig. 3A has lowered itself in the water compared to the state in Fig. 3A. In an embodiment, the floating protection system is provided with ballast pumps to provide variable freeboard. The floating barrier may be designed to ballast or deballast to change its freeboard from say 5% to 50% of its total depth. Reducing freeboard permits a reduction in stresses to the barrier during bad weather.

Reference is now made to Fig. 4, which is a block diagram showing a central ballast controller 40 that operates ballast pumps at each of the barrier's section hulls. Pumps 42 in each hull operate to pump out water from the ballast tanks or to pump water in. Compressed air tanks units 44 are used for rapid deballasting to increase freeboard in an emergency, such as when an apparently hostile ship is spotted approaching.

The ballast pumps 42 serve to reduce the structure's freeboard in bad weather, and may leave as little as 5% of the total depth as freeboard, with enough reserved buoyancy. In an emergency, compressed air from the compressed air tanks units 44 can allow for the structure to increase its freeboard rapidly to the designed freeboard by pushing out the water ballast in a way similar to the system used in submarines. The controller 40 is provided for the whole structure, to ensure that the pumping in and out of ballast is balanced between the different sections of the structure, so as to equalize the floating and submerging. As mentioned, the floating barrier can ballast/deballast to reduce the freeboard to just 5% of the structure's total depth and maintain enough reserve buoyancy. The idea is to reduce the freeboard so as not to subject the structure or anchors to excessive stresses in rough weather.

The hull sections and the anchors 48 will include strain gauges 46 to assess stresses on the structure and/or anchors in bad weather. The data may be fed back to the controller 40 to allow for reducing the freeboard of the floating protection system to avoid damage in rough seas.

Reference is now made to Fig. 5, which illustrates a cross section taken through one of the hulls 50 of the protection system. The hull is constructed as a double hull, having an outer hull 52 and an inner hull 54.

On top of the hull there may be a deck 56 to allow personnel to patrol over the closed shape. The deck may comprise a driveway capable of allowing a patrol vehicle to patrol around the closed shape, for example an armored car. A garage may be provided for housing the patrol vehicle, which then moves around on the surface of the closed structure.

Turrets, for weapons or for sensors, may be located on the structure for additional protection.

Anchors system, similar to the system used for floating oil rigs, may typically be used to hold the barrier system in position. In addition, a dynamic positioning unit may help to keep the system in position. Dynamic positioning uses thrusters, to correct the position against position signals obtained, for example, from GPS or from a laser device designed to keep the barrier at a fixed distance from the infrastructure being protected.

In one embodiment, both anchors and dynamic positioning are used together. Such a combination allows thrusters to work together with anchors and with the mass of the system to work against the momentum of the ship trying to ram the oil platform.

As mentioned, the ship hulls may comprise a double hull structure such as that used in tanker ships. In an oil tanker the double hull has a gap of 60cm in order to allow maintenance, but no larger so as not to reduce the oil carrying capacity. In the present system there is no issue of capacity, and the only concern is the ability to defeat deliberate ramming. Thus the gap between the hulls may be greater than 60cm, for example, greater than 61cm, greater than 70cm, greater than lm, substantially 1.2m or anything between 60cm and 2m.

As well as a double hull there may be provided bulkheads, longitudinal, frames, beams stringers brackets and other structural elements used in shipbuilding.

Fig. 5 further illustrates a possible positioning of ballast tanks 60, and shows the tanks in a full state.

In the present embodiments, a floating hull may be constructed in order that, when arranged with additional hulls of the same or similar construction, a closed shape can be formed around a marine installation. The individual hull may be configured as a section of a ring, and all the hulls together form a rigid ring or close structure when joined to each other.

In the present embodiments the floating hull is constructed as discussed above so as to form a closed shape around a marine installation. The individual hulls are all double hulls and have a gap between inner and outer hulls of the double hull which exceeds 60cm.

The ability of various structures of double hull to resist collisions is discussed in Shengming Zhang - January 1999 PhD thesis at the Department of Naval Architecture and Offshore Engineering - Technical University of Denmark, in particular sections 3.6, 4.3, 4.4 and 4.5.

In the present embodiments, the floating hull system may comprise multiple hulls connected together, with a ballast management unit that equalizes ballast variation over the system to allow for uniform reduction of freeboard during rough weather.

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.