GB2447782A

GB2447782A - Underwater structure leveled using screw jacks

Info

Publication number: GB2447782A
Application number: GB0805234A
Authority: GB
Inventors: Hugh Malcolm Ian Bell
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-03-22
Filing date: 2008-03-25
Publication date: 2008-09-24
Anticipated expiration: 2028-03-25
Also published as: GB0805234D0; GB2447782B

Abstract

A template 110 is installed in a watercourse by a remotely controlled attachment and leveling machine 130 which is connected to the template 110. The machine 130 uses leveling pins (screw jacks) 60 which abut the river or sea bed 64, to level the template 110. After the template 110 is leveled, holes are drilled in the bed of the watercourse and the base is anchored to the holes, for example by bolts (62, figure 1) or by grouting.

Description

Improvements in or relating to Underwater Structures

FIELD OF THE INVENTION

The present invention relates to underwater structures and submerged devices which may be positioned within a river or tidal current and, in particular, relates to templates for the secure placement of one or more further structures upon the bcd of a watercourse.

BACKGROUND OF THE INVENTION

It is known to construct templates for the locating of structures such as oil drilling platforms in relation to the seabed, in areas such as the North Sea and the Gulf of Mexico. This device, typically, has consisted of an open steel box with multiple holes in it, dependent on the number of wells to be drilled. This drilling template is placed over the well Site, a relatively shallow hole is then dug, in which the drilling template is cemented into place. Drilling into the sea bed may be necessary; where drilling into rock on the seabed is performed, control and power systems on board support ships situated at the sea surface will be required. As will be appreciated these techniques are expensive and employ large vessels often with sophisticated positioning systems. Once secured to the sea or river basin floor, the drilling template can allow accurate drilling using a drill bit connected by a drillstring driven by the drilling platform to take place.

However, templates have evolved from being a piece of equipment that connects an underwater well site to the drilling platform on the surface of the water and the term template is now used for any fixed seabed structure that enables connection with a drill rig, research vessel or similar, together with the use of several anchors whereby, for example drilling pipes can retrieve oil. Templates, however, have been limited in their application to areas of seabed where there is negligible current, since the installation of a template, whether using gravity, remotely piloted vehicles, diving personnel or other techniques, cannot easily he performed where there is a current above 2-3 knots. Whilst compared to above ground speeds, this speed appears to be low, one needs to consider that for every knot of water current passing through an area of one square metre, then the mass of water passing through that area per minute is over 30 tonnes; in high currents >5knots, the mass flowing per unit area per minute is extremely large and this has impeded the positioning of templates in areas other than with low to negligible current without the need for expensive support vessels.

Whilst it is well known that tidal currents can indeed be used to reliably generate electrical energy, the cost of generation can be prohibitively expensive arising from the initial capital cost of the structure and the manoeuvring of the structure to a desired high current location where the energy of the water current flow is proportional to the cube of the velocity and imposes high forces due to drag and can remain, relatively maintenance free in extreme conditions. Certain types of structures, such as those fitted with caissons, are difficult to transport from a port of origin to a destinath)n placement area. The costs of the placement of such structures can be considerable, with a requirement to hire support boats and associated lifting paraphernalia, which would be required, typically for a couple of weeks. Problems have been known to exist in the placement of tidal energy systems and river current hydro-electric schemes in view of the tremendous currents that can be achieved. In addition to tidal currents, prevailing sea and ocean currents also exist.

Accordingly, the installation of devices, such as to harness the energy in river arid tidal currents, poses considerable difficulties; the expensive systems used offshore are not necessarily possible in areas where, for example, the draft of support vessels is too great for the inshore situations favoured.

GB2I 74975 teaches of a template levelling apparatus and a method for levelling a drilling or production template on the sea bed or similar offshore location, particularly in deep waters. However, the teaching provides the use of a free-swimming remote control vehicle (FSRCV) to assist in the placement of a jack for the levelling of a template. This system and method would not be suitable in areas of high current and would not be appropriate for an underwater power generation installation.

GB2054710 provides an inexpensive method of leveffing a seabed template a drilling or production template on the sea bed or similar offshore location by reacting mechanical screw jacks against the seabed and turning them from a rotary table of a drilling rig. The template can be raised or lowered by reversing the rotation direction. The levelling jacks are self locking and no umbilicals, hydraulics or pneumatics are required for jack operation. The sy stem and method do not relate to the issues arising from high currents nor the problems that will arise and accordingly do not offer any assistance with regard o the placement of these devices in areas of high current.

OBJECT TO THE INVENTION

The present invention seeks to provide a low capital cost sub-sea structure. The present invention also seeks to provide a secure base which is easily transportable to a placement destination, whereby to locate structures/fixtures with respect to the seabed. The present invention seeks to provide an underwater template to enable economic positioning of structures and systems operable in conditions where strong river currents or tidal forces are present.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, there is provided a method of installing a template to the bed of a watercourse, the template being operable to secure a functional body to said bed; the method comprising the steps of: placing the template on the bed of the watercourse; utilising a remotely controlled attachment and levelling machine that is connected to the template in operation whereby i) to operate a levelling device or mechanism in relation to the template so that the levelling device can abut against the bed of the watercourse whereby to the structure and ii) to drill holes to attach the template to the bed of the watercourse; and, anchoring the template with respect to the drilled holes using chemical and/or mechanical means.

The method can conveniently comprise the further step of attaching the functional body or structure to the template. The levelling device can comprise one or more jacks in relation to the template so that they abut against the bed of the watercourse whereby to level the template. The jacks may comprise levelling pins, screw operated means, hydraulic means, levers or other means as are known.

The chemical means can comprise cement, grout or glues such as epoxy adhesives.

Mechanical means can comprise screws, bolts, such as rock anchors, bolts and dowels as are known. Anchors may assist in the step of attaching the structure to a base structure whereby to withstand currents to provide temporary stability.

Conveniently, the remote control vehicles connected to the template can perform all the sub-sea operations. Notwithstanding this, the remote control vehicles can be operated in conjunction with divers to perform certain sub-sea operations.

One or more anchors may be utilised to ensure that the template can withstand currents prior to attachment of the template to the bed of the watercourse. One or more anchors may be utilised to ensure that the functional structure can be positioned accurately with respect to the template prior to attachment of the functional structure with respect to the template.

The remotely controlled attachment and levelling machine may be attached to the template either prior to placement upon the bed of the watercourse; alternatively, the remotely controlled attachment and levelling machine can be connected to the template once placed upon the bed of the watercourse.

In accordance with another aspect of the invention, there is provided a template for placement on a bed of a watercourse, whereby once the template has been p]accd upon said bed, the weight of the template is sufficient to enable the template to remain, despite the presence of high currents, the template being of a configuration such that a remote controlled attachment and levelling machine can be connected thereto whereby to enable levelling and attachment operations of the template so that is can be securely attached to said bed.

The template can comprise a ring corresponding to one of a generally circular, elliptical or rectangular shape. The template can have side walls against which a remote controlled attachment and levelling device can move relative to and locate with. Alternatively the template can be provided with a track mounted upon the body, or comprising part of the structure, of the template, whereby to enable the device to move about the template, to enable attachment of the template to the bed of the watercourse.

In accordance with a still further aspect to the invention, there is provided a remotely controlled attachment and levelling device for underwater operation, upon the bed of a watercourSe, the device being configured to connect with respect to a template, for operation in underwater conditions, with remote operation by personnel, whereby, in use, the device can assist in the securing the template to the bed of the watercourse. The device has at least one articulated arm operable to retain and control tools for connection of the template with respect to the bed of a watercourse.

The device can have wheeled connection means which locate with the body of a template, whereby to enable the device to move about the template, to enable attachment

D

of the template to the bed of the watercourse. Alternatively or additionally, the device can have wheeled connection means which locate with a track mounted upon the body, or comprising part of the structure, of the template, whereby to enable the device to move about the template, to enable attachment of the template to the bed of the watercourse.

The present invention provides means particularly suited for shallow water, high current inshore situations, where known systems would fail or would not be able to work in the water depth available and/or would be more expensive.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference will now be made, by way of example only, to the Figures as shown in the accompanying drawing sheets, wherein:-Figure 1 shows a sectional view of an underwater installation in accordance with the invention; Figure 2 shows a template in plan view; Figure 3 is a side view of an attachment device upon a template; and, Figure 4 shows the attachment device upon a template in plan view.

DETAILED DESCRIPTION OF THE INVENTION

In order to provide a better understanding of the present invention an embodiment of the invention will now be described. It will be apparent, however, to one skilled in the art, that the present invention may be practised without these specific details. This should not be construed to limit the present invention, but should be viewed merely as an example of a specific way in which the invention can be implemented. Well known features have not been described in detail so as not to obscure the present invention.

Referring now to Figure 1, there is shown an underwater enclosure 100 suitable for fitment of a waterwhccl arrangement, for example. The enclosure comprises a gas-and water-tight dome structure 102 which is adapted to overlie a waterwhccl arrangement 114, the enclosure being such that it encloses a volume of gas. The size of the enclosure can be 20m in diameter or more; the height can be 8 meters or more. The shape of the dome structure is such that undersea pressures can be tolerated whilst iLJS() ensuring that it does not present a significant barrier to the flow of water around the structure. The fcature of a watcrwhccl 104 within an undersea enclosure, whereby to enable the waterwheel to operate as an under-current waterwheel is disclosed in a co-pending patent application. The enclosure 100 is mounted, via legs ii, upon a template 110; attached to and extending below the templates screw anchors 62 which securely locate the template to a bedrock or similar foundation after positioning with levelling pins 60 on the bed 104 of the watercourse.

As discussed above, it is known in the undersea industry, for example, in the securing of oil platforms that templates are employed whereby drilling into rock on the seabed is performed with control and power systems being situated at the sea surface. Figure 2 shows the template in plan view upon a watercourse 104.

The mass of the template must be sufficient whereby it can withstand high currents, whilst the structure is being attached to the seafloor/bed of the watercourse. Only in conditions of extremely high current, such as 10 knots or more, would further securing means, such as one or more anchors, be necessary prior to attachment to a bedrock.

Typically, the weight would be of 5 -20 tonnes. Whilst free swimming remotely controlled vehicles can be employed in certain conditions, such remotely controlled vehicles cannot operate in conditions of high current. Note also that divers may operate in groups to enable anchoring procedures to be accomplished and generally assist, but again will not be capable of assisting in most conditions where there is more than a negligible current. For example, in areas of high current, it will be appreciated that the deployment of divers, if possible, would be both dangerous and would possibly mean that work could not be carried out to a required standard.

with reference to Figure 3, the invention provides a template in combination with a template connected remotely controlled attachment and levelling device 130 for the positioning of underwater structures to harness tidal power etc.. The template comprising a ring in this instance, to support an underwater device which is circular in plan, is conveniently uniform in cross-section or other structure and a template connected remotely controlled attachment and levelling device çITRCALD), is mounted to the template and operates during levelling and installation of the template.

Conveniently, the template is lowered to the bed of the watercourse, with the remotely controlled attachment and levelling device being connected to the template, whereby attachment of the template to the bed of the watercourse is simplified. Alternatively, the template and the ren-iotcls controlled attachment and levelling device are brought to the bed separately; an initial process step being required to connect the remotely controlled attachment and levelling device to the track or body of the template and can only be performed in regions of high current during slack water. This will necessarily be more time consuming.

The remotely controlled attachment and levelling device 130 is shown connected with respect to a section of the template or attachment structure or ring 110. The remotely controlled attachment and levelling device 130 is capable of travelling around the periphery of the circular template although its means of propulsion are not shown. The remotely controlled attachment and levelling device is connected temporarily or otherwise to the template to perform levelling and attachment functions. Wheels associated with the attachment and levelling device may clamp, for example, the template between an inside circumference and an outside circumference, conveniently under tension and with the use of wheels with rubber/elastic tvres. The template could comprise a generally linear component, or be a frame of a square/rectangular contiguranon, but special wheels and rollers would need to be provided to enable the remotely controlled attachment and levelling device to traverse around right-angle junctions and the like, but details such as propulsion means are not shown for simplicity.

Altemativel', a track (or alternative guide means) may be fitted to one or more surfaces of the template, whereby the attachment and levelling device can travel about the template by means of such track. Conveniently, the track could be removed or serve a further function at a later date.

The remotely controlled attachment and levelling device comprises a manipulator 132, a drilling/torque head 136 and a tool/component storage arrangement 134. Conveniently articulated arms would be employed, from a base whereb) accurate positioning of tools etc is possible. The vehicle also comprises a manipuiitor 132, a drilling and torque head and a tool/component storage rack 134. The manipulator 132 can move and rotate as indicated by the arrows and is capable of extracting tools from the rack 134, which tools are placed beneath the tool head 134 to rotate and manipulate the tool. Here, the term tool is used broadly to refer to any item required by the tool head whereby to level and secure the template 110 to the bed of any watercourse. An anchorage device 136 is shown passing through the template 110. The use of a remotely controlled attachment and levelling device attached to and relatively moveable about the same enables the template and subsequent functional structures to be attached with minimal deployment of pcrsonncl, often in inhospitable conditions, importantly with personnel not ordinarily being recpii-ed to be present in such inhospitable conditions. The remotely controlled attachment and levelling device may be controlled using acoustic signals.

With reference to Figures 3 & 4, the template is levelled and attached to the watercourse using levelling pins 60 and securing devices 62, respectively -note, however that only one of each is shown in Figure 1. The process of attaching the template, which happens to be in the form of a ring in this instance, requires a levelling mechanism taking the form of pins 60 which are inserted through the template; the pins act against the template or ring and arc moved downwardly and adjusted such that they can level the template against sub-sea rock 64, below shale/sand 66. The pins conveniently comprise a screw threaded bolt; typically three will be used, but more or less may be used.

Alternative levelling means may be deployed, as is known, such as hydraulic means, levers and the like. Once the base is level, the base is fastened to the sea bed by' bolts 62 or other fastening means such as rock bolts and/or dowels. Chemicals may be employed, such as epoxy adhesive; cement or grout may also be used. Injection drilled anchors such as those sold under the Titan brand may be employed. Such types of bolts comprise steel tube using fcrritic-austenitic steels and other micro- alloy structural steels having deep threads. As these types of bolts are drilled into the rock, grout is pumped through the centre of the drill steel and flushes debris out of the hole. Once at its required length, the drill string is cut and becomes the anchor bolt. Further bolts are secured thereafter, moving progressively around the circumference of the structure; the total number of bolts that are required depends on the nature of the bed, the types of anchoring devices, the expected forces anticipated and the like. Initial bolts placed to secure and level the structure would be approximately 24mm in diameter; other screws, which are placed into rock would be of a greater diameter, typically 75mm diameter, or more. Those skilled in the art would be able to calculate the number and size of screws to be placed to support the structure, with regard to type of materials employed, the type of rock and the nature of the watercourse bed. The function at low cost, by a few engineers, for example, based on the shore in a temporary shelter such as a container based workshop facility. This is in critical contrast to the use of support ships and the like which operate freely piloted mini-subs to enable placement of known templates.

During a levelling and securing process power and necessary fluids are supplied from a remote location, either being a boat or a land base using a control line (umbilical).

Once the template is installed, the functional structural device can be installed upon the template relatively quickly, using appropriate means, when conditions permit.

Alternavelv, the remote controlled attachment and levelling device may assist in the placement of the functional structure. As referred to above, when the device to be installed is a power generation unit, the lightness and simplicity of construction of the proposed underwater attachment will enable the device to be installed quickly and safely.

The template may comprise a simple linear base whereby a different type of functional structure may be placed securely upon the bed of a water course -for example, the functional structure may comprise a base for a wind powered generator or a barrage system for an underwater current generator system, or the footings for a causeway or bridge etc.. The remote controlled attachment and levelling device can then be removed from the template.

One method of positioning the structure would be to use flotation bags: the device to be installed would be floated by the use of a support vessels; and tethered to a ground anchor against the prevailing current and the device would be lowered, with a remote controlled vehicle or similar whereby, upon de-ballasting of the buoyancy or flotation bags, the structure can be sunk in a controlled fashion, using the template as an anchor, the umbilical may be simply deployed using a winch and be connected. A minimal amount of diver intervention may be required to assist the process. \Vherc the device attached to the template is a hvdro-electric generator system, it is anticipated that it will generally be placed close to the shore, within a few kilometres of land, in areas where there are likely to be strong tidal / river flows; accordingly it would be convenient to use remotely piloted vehicles for such installations. It is especially convenient if such servicing can be performed from the shore. The current also imposes high forces on such a structure; the energy of a current of the wheel is proportional to the cube of the velocity of the water flow current. ft would be very difficult -if not impossible -to install and secure such a structure in areas of high current to the seabed in the time it takes for the tide to turn without the use of a template connected remotely controlled attachment and levelling device as described above -this is different to a free-swimming remote control vehicle -which cannot be used in conditions of high current.

Notwithstanding this, it may be appropriate to remove the remote controlled attachment and levelling device prior to attachment of the functional structure.

As will be appreciated known techniques are expensive and employ large vessels with sophisticated positioning systems. The installation of devices to harness the energy in river and tidal currents, poses considerable difficulties; the expensive systems used offshore are not necessarily possible in areas where the expense and possibly the draft of support vessels is too great for the inshore situations favoured. The installation of a structure in accordance with the present invention provides an economical system. ii

Claims

1. A method of installing a template to the bed of a watercourse, the template being operable to secure a functional body to said bed; the method comprising the steps of: placing the template on the bed of the watercourse; utilising a remotely controlled attachment and levelling machine that is connected to the template in operation whereby i) to operate a levelling device in relation to the template so that the levelling device can abut against the bed of the watercourse whereby to level the structure and ii) to drill holes to attach the template to the bed of the watercourse; and, anchoring the template with respect to the drilled holes using chemical and/or mechanical means.

2. A method according to claim 1, further comprising the step of attaching the functional structure to the template.

3. A method according to claim 1, wherein remote control vehicles are operated to perform all the sub-sea operations.

4. A method according to claim 1, wherein remote control vehicles are operated in conjunction with divers to perform the sub-sea operations.

5. A method according to any one of claims I to 4, further comprising the step of attaching one or more anchors to ensure that the base structure can withstand currents prior to attachment of the template to the bed of the watercourse.

6. A method according to any one of claims I to 5, wherein the chemical means can comprise cement, grout or glues.

7. A method according to any one of claims I to 5, wherein mechanical means can a functional body in a watercourse, the functional body comprising comprise screws, bolts, such as rock anchors, bolts and dowels.

8. A method according to any one of claims I to 7, wherein the method further comprises the step of connecting the remotely controlled attachment and levelling machine to the template upon the bed of the watercourse.

9. A method according to any one of claims 1 to 7, wherein the method further comprises the step of connecting the remotely controlled attachment and levelling machine to the template prior to the placement of the template upon the bed of the watercourse.

10. A method according to any one of claims 1 to 9, further comprising the steps of: transporting a functional structure to the surface above the point where it is required; lowering the functional structure b' releasing gases from buoyancy devices; positioning the functional structure above the base and coupling the two bodies together.

11. A functional structure being the product of any one or more (if claims I to 10, wherein the functional structure is operable to perform an one or more of the tasks associated with one or more of the following activities, namely drilling, installing explosive piles, generating electricity, materials handling, pumping of tluids, operating valves, operating mechanical mechanisms, operating hydraulic systems; operating telemetry systems.

12. A template for placement on a bed of a watercourse, the weight of the template being sufficient to enable the template once placed upon said bed to remain in position despite the presence of high currents, the template being of a configuration such that a remote controlled attachment and leveffing machine can be connected thereto whereb) to enable levelling and attachment operations of the template so that is can be securely attached to said bed.

13. A template according to claim 12, wherein the template comprises a ring corresponding to one of a generally circular, elliptical or rectangular shape.

14. A template according to claim 12, wherein the template has side walls against which a remote controlled attachment and levelling device can move relative to and locate therewith.

15. A template according to claim 12, wherein the template is adapted to support a track about which a remote controlled attachment and levelling device can move relative to and locate therewith.

16. A remotely controlled attachment and levelling device for underwater operation, upon the bed of a watercourse, the device being configured to connect with a template, for operath)n in underwater conditions, with remote operation by personnel, whereby, in use, the device can assist in the securing the template to the bed of the atercourse.

17. A dcvicc according to Claim 16, wherein the device has wheeled connection means which locate with the body of a template, whereby to enable the device to move about the template, to enable attachment of the template to the bed of the watercourse.

18. A device according to Claim 16, wherein the device has wheeled connection means which locate with a track mounted upon the body, or comprising part of the structure, of the template, whereby to enable the device to move about the template, to enable attachment of the template to the bed of the watercourse.

19. A device according to an one of claims 16 -18, wherein the device has at least one articulated arm operable to retain and control tools for connection of the template with respect to the bed of a watercourse.

20. A device according to any one of claims 16 -18, wherein one or more articulated arms are provided with a manipulator operable to retain and control tools for connection of the template with respect to the bed of a watercourse.

21. A method substantially as described herein, with reference to any one or more of the accompanying Figures.

22. A template substantia1l as described herein, with reference to any one or more of the accompanying Figures.

23. A device substantially as described herein, with reference to any one or more of the accompanying Figures.