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(11) | EP 2 299 006 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method of attaching a submerged structure to a floor of a body of water |
| (57) A remotely operable drilling apparatus 6 comprises frame 10 and drive means arranged
to drive annular pile 8, which is loaded in the drilling apparatus 6 into the floor
of a body of water. The drive means comprises a power swivel 12 which attaches to
the top of the annular pile 8 by means of a drive head. Delivery means is also provided
which comprises at least one nozzle to enable flushing fluid and grout to be injected
around annular pile 8. The power swivel 12 is raised and lowered by rack and pinion
means 14 disposed on either side of the power swivel 12.
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[0001] The present invention relates to a method of attaching a submerged structure to a floor of a body of water, the submerged structure comprising at least one aperture arranged to receive a pile, and relates particularly, but not exclusively, to a method, apparatus and system for attaching a submerged structure to a floor of a body of water or other submerged surface.
[0002] It is desirable to utilise fast flowing water to generate electricity from submerged power generating turbines. In fast flowing water, these turbines require high integrity submerged turbine supports that will not be moved by the high current.
[0003] In some high current areas, a floor of a body of water, such as the seabed can be formed from a particularly hard rock formation rather than soft mud or sand. This is partly as a result of the fact that the fast current tends to scour soft mud and sand away from the seabed to reveal the base rock formation.
[0004] The combination of fast flowing water and a hard seabed precludes the use of jack-up type vessels. Jack-up vessels comprise a plurality of support legs on which a platform is mounted. The platform is vertically moveable up and down the support legs to account for changing water levels. This type of vessel generally uses a drill string to drill bores in the seabed. Piles can then be grouted into the drilled bores in order to attach a turbine support structure to the seabed.
[0005] However, a problem arises when the legs of a jack-up vessel initially contact a hard seabed because the legs tend to bounce on the hard rock floor and as a result can become damaged and even fracture. Consequently, it is extremely difficult to locate and secure a jack-up vessel in a region where there is a hard seabed formation and they therefore tend not to be used in such circumstances.
[0006] The use of a dynamically positioned (DP) vessel is also generally precluded in areas with particularly high current because it is difficult to ensure that the DP vessel remains on station in such high current areas. Furthermore, because of the amount of fuel used in stabilising the DP vessel at high current speeds, this option is particularly expensive and therefore undesirable.
[0007] Areas of high current speed also pose another problem for securing a subsea structure to the seabed. It is generally only practical to install a pile during the slack water time window when the tide is slowest. This time window can be of the order of less than one hour and it is therefore extremely difficult, if not impossible, to perform multiple drillings in such a time window.
[0008] A solution to the above problems is proposed in WO2008/125830. This document describes a surface vessel on which a structure to be attached to the seabed is located. An example of such a structure is a tripod support for an underwater power generating turbine. When the structure is on the surface vessel, individual drilling rigs are attached to each leg of the tripod which is to be piled to the seabed. A crane is then used to lower the structure, with drilling rigs attached to the seabed.
[0009] At the seabed, each drilling rig is then activated. Each drilling rig comprises a percussion drill which drills into the seabed and pulls down a pile behind the drill bit into the drilled socket. When the socket is drilled to its maximum depth, the drill bit is retracted leaving the pile in the seabed. The drilling rig is then detached and withdrawn to the surface. Grout is then pumped into the annulus between the tripod foot and the outside of the pile and also into the cylindrical hole defined by the centre of the pile to seal the pile into the seabed.
[0010] The method of W02008/125830 suffers from several drawbacks:
- 1) The surface vessel must be particularly large to be able to support and lower a tripod structure to the seabed. Consequently, heavy lifting equipment such as a large crane is required on the vessel.
- 2) Once drilling is complete, the percussion drill must be retracted in order to pump grout into the pile and seal the pile in the seabed.
- 3) The only thing that holds the submerged structure to the pile is the grout or grout disposed in the annulus between the structure foot and the outside of the pile. This joint could be prone to failure, particularly if high current washes grout away before it fully sets.
- 4) Repeated use of the percussion drill will result in wear and tear on the drill leading to increased maintenance and operation costs.
- 5) This system may require the use of an ROV. An ROV can generally only operate in currents of less than 1.5 knots which restricts the areas in which this system can be used.
- 6) If one of the drilling rigs fails, it is a complicated and costly operation to replace the rig on the seabed and conduct the piling operation.
[0011] Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.
[0012] According to an aspect of the present invention, there is provided a method of attaching a submerged structure to a floor of a body of water, the submerged structure comprising at least one aperture arranged to receive a pile, the method characterised by:
locating a remotely operable drilling apparatus on the submerged structure adjacent an aperture arranged to receive a pile, wherein the remotely operable drilling apparatus is loaded with an annular pile comprising an annular bit at a first end thereof and a locking member at a second end thereof, the annular bit being arranged to drill an annulus into the floor into which the annular pile is to be driven and the locking member being arranged to resist removal of a portion of the submerged structure from the floor of the body of water;
operating the remotely operable drilling apparatus to drive said annular pile through the aperture and into the floor of the body of water to cut an annulus into the floor of the body of water and drive the locking member against a portion of the submerged structure around said aperture; and
filling said annulus with grout in order to retain the annular pile in said annulus and resist removal of a portion of the submerged structure from the floor of the body of water.
[0013] The step of locating a remotely operable drilling apparatus to the submerged structure provides the advantage that a surface vessel is not required to lift the whole structure to the seabed which greatly reduces the size of vessel required and the associated running costs.
[0014] Use of an annular pile comprising an integral annular bit provides the advantage of simplifying the remotely operable drilling apparatus because it does not require a drill bit and is merely required to rotate the annular pile. This reduces the cost and complexity of the drilling apparatus.
[0015] This also provides the advantage that an annulus can be drilled in the seabed rather than a cylindrical socket because the drill bit does not have to be retracted. This means that grout can be used to fill the regions in the annulus outside of and inside of the annular pile to form an annular grout seal in the seabed which is particularly strong. This also requires less grout than filling an entire cylindrical hole.
[0016] Use of an annular pile comprising a locking member provides the advantage of a positive downward force being applied by the pile to the submerged structure, rather than simply relying on an annular grout seal above the seabed.
[0017] As a result of the fact that the drilling and grouting operations are both conducted by the remotely operable drilling apparatus without withdrawal of a drill bit, this provides the advantage of reducing the time taken to place a pile in the seabed.
[0018] In a preferred embodiment, the step of locating a remotely operable drilling apparatus on the submerged structure adjacent an aperture arranged to receive a pile comprises one or more of the following steps:
a) slidably interconnecting the remotely operable drilling apparatus to at least one guide line, wherein at least one said guideline is attached to the submerged structure at a location adjacent an aperture arranged to receive a pile, and lowering the remotely operable drilling apparatus along at least one said guideline whilst the at least one said guide line is pulled taut;
b) moving guide means disposed on the base of the remotely operable drilling apparatus into contact with a portion of the submerged structure adjacent an aperture arranged to receive a pile to align said annular bit with said aperture; or
c) operating first clamping means to clamp said remotely operable drilling apparatus to the submerged structure adjacent said aperture.
[0019] By slidably interconnecting the remotely operable drilling apparatus to at least one guideline, this provides the advantage of simplifying deployment of the drilling apparatus down to the aperture of the submerged structure on the seabed. This greatly reduces the time taken to perform a piling operation and means that more piling operations can be conducted in a slack water time window. The submerged structure can be deployed on the seabed with the guidelines attached to buoys which float on the surface to enable easy location and retrieval by the vessel conducting the drilling and piling operation.
[0020] By moving guide means disposed on the base of the remotely operable drilling apparatus into contact with a portion of the submerged structure adjacent an aperture arranged to receive a pile to align said annular bit with said aperture, this provides the advantage of further simplifying location of the remotely operable drilling apparatus on the submerged structure which saves time and increases the amount of piling operations that can be conducted in a predetermined time period.
[0021] By operating first clamping means to clamp said remotely operable drilling apparatus to the submerged structure adjacent said aperture, this provides the advantage of providing reaction means for the drilling operation.
[0022] In a preferred embodiment, said step of operating the remotely operable drilling apparatus to drive said annular pile through the aperture and into the floor of the body of water to cut an annulus into the floor of the body of water comprises one or more of the following steps:
d) attaching drive means of the remotely operable drilling apparatus to the annular pile and operating the drive means to rotate and push the annular pile into the floor of the body of water; or
e) pumping flushing fluid through said annular pile to remove cuttings from a drilled annulus and provide lubrication and cooling to said annular bit.
[0023] The step of filling said annulus with grout in order to retain the annular pile in said annulus may comprise operating delivery means of the remotely operable drilling apparatus to fill said annulus with grout.
[0025] The method may further comprise one or more of the following steps:
f) disconnecting the remotely operable drilling apparatus from the submerged structure and retrieving the remotely operable drilling apparatus to a surface vessel;
g) loading a further annular pile on said remotely operable drilling apparatus and repeating the method as defined above on a further aperture of said submerged structure.
[0026] According to another aspect of the present invention, there is provided a remotely operable drilling apparatus characterised by:
locating means arranged to remotely move into engagement with a submerged structure adjacent an aperture arranged to receive a pile;
drive means arranged to drive an annular pile into a floor of a body of water, wherein the annular pile comprises an annular bit at a first end thereof and a locking member at a second end thereof, the annular bit being arranged to drill an annulus into the floor into which the annular pile is to be driven and the locking member arranged to resist removal of a portion of the submerged structure from the floor of the body of water.
[0027] By providing locating means arranged to move into engagement with a submerged structure adjacent an aperture arranged to receive a pile, this provides the advantage that a surface vessel is not required to lift the whole structure to the seabed which greatly reduces the size of vessel required and the associated running costs.
[0028] Use of an annular pile comprising an integral annular bit provides the advantage of simplifying the remotely operable drilling apparatus because it does not require a drill bit and is merely required to rotate the annular pile. This reduces the cost and complexity of the drilling apparatus.
[0029] This also provides the advantage that an annulus can be drilled in the seabed rather than a cylindrical socket because the drill bit does not have to be retracted. This means that grout can be used to fill the regions in the annulus outside of and inside of the annular pile to form an annular grout seal in the seabed which is particularly strong. This also requires less grout than filling an entire cylindrical hole.
[0030] Use of an annular pile comprising a locking member provides the advantage of a positive downward force being applied by the pile to the submerged structure, rather than simply relying on an annular grout seal above the seabed.
[0031] The apparatus may further comprise delivery means arranged to fill said annulus with grout in order to retain the annular pile in said annulus and resist removal of the submerged structure from the floor of the body of water.
[0032] By providing delivery means arranged to fill said annulus with grout in order to retain the annular pile in said annulus and pin the submerged structure to the floor of the body of water, this provides the advantage of reducing the time taken to place a pile in the seabed because drilling and grouting is performed without removal of a drill bit.
[0033] In a preferred embodiment, the apparatus further comprises one or more of the following features:
h) guide means disposed on the base of the remotely operable drilling apparatus, the guide means arranged to align said annular bit with an aperture arranged to receive the pile; or
i) clamping means for clamping said remotely operable drilling apparatus to the submerged structure adjacent said aperture arranged to receive a pile.
[0034] By providing guide means disposed on the base of the remotely operable drilling apparatus, this provides the advantage of further simplifying alignment of the remotely operable drilling apparatus with an aperture of the submerged structure. This saves time and increases the amount of piling operations that can be conducted in a predetermined time period.
[0035] Said guide means may comprise a female conical portion arranged to abut a corresponding male conical portion disposed around said aperture arranged to receive a pile.
[0036] This provides a relatively straightforward to manufacture guide means which is self-centering.
[0037] In a preferred embodiment, the drive means comprises one or more of the following features:
j) a power swivel comprising a drive head arranged to releasably engage with and rotate said annular pile;
k) rack and pinion means arranged to move said power swivel towards the floor of a body of water; or
l) retractable support clamping means arranged to hold said annular pile in the remotely operable drilling apparatus before drilling and provide stability during drilling.
[0038] The power swivel in combination with rack and pinion means provides the advantage of a drive means that is relatively straightforward and can be used to quickly reload annular piles and perform further piling operations.
[0039] According to a further aspect of the present invention, there is provided a system for attaching a submerged structure to a floor of a body of water, the submerged structure comprising at least one aperture arranged to receive a pile, the system characterised by:
a remotely operable drilling apparatus as defined above; and
umbilical means arranged to provide hydraulic and/or electrical power from a surface vessel to said remotely operable drilling apparatus and to provide flushing fluid and/or grout to said delivery means from a surface vessel.
[0040] The system provides the advantage that a process of piling a submerged structure to the floor of a body of water can be operated from the surface in a relatively rapid and straightforward procedure. An annular pile is loaded into the drilling apparatus on the surface and the drilling apparatus is then submerged and descends to the aperture on the submerged apparatus. An annular pile is drilled into the seabed and grouted in a simple procedure without the need for divers or ROVs. The annular pile with integral bit and locking means is a throw away consumable and is therefore a particularly cost-effective.
[0041] In a preferred embodiment, the system further comprises one or more of the following features:
m) adapter means arranged to enable the umbilical means to be disconnected from the surface vessel and attached to a buoy;
n) pumping means disposed on a surface vessel and arranged to pump flushing fluid and/or grout to said delivery means via said umbilical means; or
o) at least one guide line attached to the submerged structure at a location adjacent an aperture arranged to receive a pile, at least one said guide line arranged to be interconnected to said remotely operable drilling apparatus to guide the remotely operable drilling apparatus to a location on said submerged structure adjacent an aperture arranged to receive a pile whilst the at least one said guide line is pulled taut.
[0042] By providing adapter means arranged to enable the umbilical means to be disconnected from the surface vessel and attached to a buoy, this provides the advantage that in the event of bad weather and rough seas, the piling operation can be quickly interrupted and detached from the surface vessel for safety. The buoy can then be retrieved and piling recommenced relatively quickly when conditions permit.
[0043] The at least one guideline provides the advantage of simplifying deployment of the drilling apparatus down to the aperture of the submerged structure on the seabed. This greatly reduces the time taken to perform a piling operation and means that more piling operations can be conducted in a slack water time window. The submerged structure can be deployed on the seabed with the guidelines attached to buoys which float on the surface to enable easy location and retrieval by the vessel conducting the drilling and piling operation.
[0044] The system may further comprise tensioning means arrange to pull at least one said guide line taut.
[0045] According to a further aspect of the present invention, there is provided an annular pile characterised by:
a shaft comprising outer and inner concentric cylindrical sleeves defining an annular channel therebetween;
an annular bit mounted to a first end of the shaft; and
a locking member mounted to a second end of the shaft;
wherein a path for fluid flow is defined from a first opening in the locking member, through said annular channel and through a second opening defined by said inner sleeve.
[0046] This provides the advantage of providing a channel in the pile for flushing fluid and grout. This is particularly useful when drilling in formations where there is a risk that the drilled annulus may collapse. This therefore ensures a rigid piling operation will be completed in such formations.
[0047] Said annular bit may be mounted to said outer sleeve and the second opening may be defined by an end of the inner sleeve.
[0048] Preferred embodiments of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a surface vessel used in a method of attaching a submerged structure to a floor of a body of water in accordance with a first embodiment of the present invention;
Figure 2 is a close up perspective view of the base of a remotely operable drilling apparatus and several annular piles used in a method of attaching a submerged structure to a floor of a body of water in accordance with a first embodiment of the present invention;
Figure 3 is a perspective view of a first stage of loading an annular pile to the remotely operable drilling apparatus;
Figure 4 is a view corresponding to Figure 3 showing the second stage of loading an annular pile into the remotely operable drilling apparatus;
Figure 5 is a close up perspective view of a third stage of loading an annular pile into the remotely operable drilling apparatus;
Figure 6 is a close up perspective view of a fourth stage in loading the annular pile into the remotely operable drilling apparatus;
Figure 7 is a perspective view of the remotely operable drilling apparatus located on a surface vessel and loaded with an annular pile;
Figure 8 is a perspective view of a first stage of deployment of the remotely operable drilling apparatus;
Figure 9 is a perspective view of a second stage of the deployment of the remotely operable drilling apparatus;
Figure 10 is a perspective view of a third stage of the deployment of the remotely operable drilling apparatus showing the submersion of the remotely operable drilling apparatus;
Figure 11 is a perspective view of a fourth stage of the deployment of the remotely operable drilling apparatus;
Figure 12 is a perspective view of a fifth stage of the deployment of the remotely operable drilling apparatus showing the apparatus descending along guidelines towards the submerged structure to be pinned to the seabed;
Figure 13 is a perspective view of the remotely operable drilling apparatus locating itself adjacent an aperture through which the annular pile is to be driven;
Figure 14 is a view corresponding to Figure 13 in which the lower locking clamps have moved into an engaged position around the aperture of the submerged structure to hold the remotely operable drilling apparatus on the structure;
Figure 15 is a perspective view corresponding to Figures 13 and 14 in which drilling has commenced and the upper locking clamps have been retracted in order to allow the locking member to pass through the upper locking clamps;
Figure 16 is a view corresponding to Figure 15 showing the annular pile being drilled into the seabed;
Figure 17 is a view corresponding to Figure 16 in a further advanced stage of drilling;
Figure 18 is a partially cross-sectional perspective view from below showing the annular pile cutting through rock as it is drilled downwardly to form an annulus;
Figure 19 is a partially cross-sectional perspective view from below showing the final drilling stage;
Figure 20 is a view corresponding to Figure 19 showing grout after it has been pumped into the annulus;
Figure 21 is a perspective view of the remotely operable drilling apparatus in the condition at the end of drilling;
Figure 22 is view corresponding to Figure 21 in which the annular pile has been released from the remotely operable drilling apparatus;
Figure 23 is a view corresponding to Figure 22 showing the remotely operable drilling apparatus released from the submerged structure and in a condition to be raised to the surface;
Figure 24 is a perspective view of a remotely operable drilling apparatus of a second embodiment of the present invention;
Figure 25 is a perspective view of the remotely operable drilling apparatus of Figure 24 located adjacent a structure to be pinned to the seabed;
Figure 26A is a cross section taken through a shaft of an annular pile according to an embodiment of the present invention;
Figure 26B is a longitudinal cross sectional view of the annular pile of Figure 26A; and
Figure 26C is a perspective view showing an annular pile installed through a collar of a submerged structure.
[0049] Referring to Figure 1, a surface vessel such as a ship 2 is located on a body of water 4 such as a sea, river or estuary having a floor to which a submerged structure is to be attached. A remotely operable drilling apparatus 6 is disposed on vessel 2. A plurality of annular piles, also known as pin piles 8 are also located on vessel 2.
[0050] Referring to Figures 11 and 12, remotely operable drilling apparatus 6 comprises frame 10 and drive means arranged to drive annular pile 8, which is loaded in the drilling apparatus 6 into the floor of a body of water. The drive means comprises a power swivel 12 which attaches to the top of the pin pile by means of a drive head 11 (Figure 22). The drive head 11 contains drive pins (not shown) arranged at equal points around the outer diameter of the drive head. The drive head engages with machined locating slots (not shown) which are located in the annular pile locking collar 22 (Figure 2). The drive head 11 can be released from the pin pile by rotating the power swivel in a reverse direction. The power swivel can be rotated in either a forward or reverse direction with an equal amount of torque being available in either direction. Delivery means is also provided which comprises a fluid conduit (not shown) located adjacent drive head 11 to enable flushing fluid and grout to be injected around annular pile 8.
[0051] The power swivel 12 is raised and lowered by rack and pinion means 14 disposed on either side of the power swivel 12. Different pin pile lengths can be accommodated in the drilling apparatus 6 by means of insertion of additional shortened pre-manufactured sections of the integrated frame and rack and pinion sections.
[0052] Centring and location of the remotely operable drilling apparatus onto the submerged structure to be pinned is assisted by guide means located on the remotely operable drilling apparatus. The guide means may comprise a female cone portion 16 disposed on the base of drilling apparatus 6. The female cone portion 16 is arranged to contact a male cone portion 18 disposed adjacent aperture 30 of submerged structure 32. Submerged structure 32 in the present example is a tripod having a platform 31 on to which a submerged turbine (not shown) is to be mounted. The tripod comprises three apertures or collars 32 through which piles are to be passed to pin the structure 32 to the seabed.
[0053] Referring to Figure 2, annular pile 8 comprises a substantially hollow cylindrical portion 20, a locking member such as locking collar 22 at a first end, and an annular bit 24 at a second end. The annular bit 24 forms a cutting shoe and is wider than the cylindrical portion 20 such that when annular bit 24 is drilled into the seabed an annulus is formed behind the annular bit 24. The locking member 22 is arranged to engage the edges of aperture 30 (Figure 12) to resist removal of a portion of submerged structure 32 from the seabed.
[0054] Alternatively, Figures 26A to 26C show an alternative embodiment of an annular pile that can be used with remotely operable drilling apparatus 6. This embodiment is useful in formations where there is a risk that a cut annulus will collapse. Annular pile 208 comprises a shaft 220 formed from outer 220A and inner 220B concentric cylindrical sleeves defining an annular channel 223 therebetween. An annular bit 224 is mounted to a first end of the shaft and a locking member 222 is mounted to a second end of the shaft 220.
[0055] A path for fluid flow is defined from a first opening 222A in the locking member, through the annular channel 223 and through a second opening 223A defined by said inner sleeve. The annular bit 224 is mounted to the outer sleeve 220A and the second opening 223A is defined by the end of the inner sleeve. Alternatively, second openings may be formed at different points through the length of inner sleeve 220B. Pile 208 can be formed by welding a length of pipe to forma an inner sleeve 220B in an existing annular pile. Pile 208 is very useful for overcoming a problem of annulus blockage.
[0056] In order to guide the remotely operable drilling apparatus 6 to aperture 30, at least one guideline 34 is attached to an arm 38 and guide post 38A of submerged structure 32. Corresponding eyelets 36 and a post guide 36B are arranged on the drilling apparatus 6 through which the guidelines 34 can be fed. Prior to being attached to the drilling apparatus 6, guidelines 34 are floated to the surface by buoys 40 (Figures 1 and 11). Consequently, referring to Figure 1, buoys 40 identify locations on the surface of the water 4 to which the remotely operable drilling apparatus 6 is to be submerged to perform a piling operation.
[0057] Referring to Figures 9 and 10, umbilical means comprises at least one cable 50 to provide hydraulic or electrical power to the remotely operable drilling apparatus 6 from the surface vessel 2. The umbilical means may also include a hose 52 through which flushing fluid and/or grout can be provided to the delivery means as will be explained in further detail below. Pumping means (not shown) is located on vessel 2 to pump flushing fluid and/or grout through hose 52. The umbilical 50, 52 may also comprise adapter means (not shown) arranged to enable the umbilical means to be disconnected from the surface vessel and attached to a buoy in the event of adverse weather conditions. This provides the advantage that in the event of bad weather and rough seas, the piling operation can be quickly interrupted and detached from the surface vessel 2 for safety. The buoy can then be retrieved and piling recommenced relatively quickly when conditions permit.
[0058] Referring to Figures 2 to 7, a method of loading an annular pile 8 in the remotely operable drilling apparatus 6 will be described.
[0059] A roller assembly 42 is provided on the surface of vessel 2. An annular pile 8 is loaded on the roller assembly 42 such that the locking collar 22 is arranged adjacent lower drilling aperture 7 of the drilling assembly 6. Annular pile 8 is then installed by running locking collar 22 rearwardly into aperture 7 such that the locking collar 22 engages the drive head 11 of power swivel 12. The power swivel 12 is then retracted along the rack and pinion means 14 to draw the annular pile 8 into the drilling apparatus 6 as shown in Figure 4.
[0060] Referring to Figures 5 and 6, once drive head 11 of the power swivel is connected to locking collar 22, retractable support clamping means such as upper locking clamps 15 are deployed to contact outer cylindrical surface 20 of annular pile 8 as shown in Figure 6. Upper locking clamps 15 serve two functions. Firstly, they hold annular pile 8 on the centre line of the drilling apparatus 6 whilst being deployed. Secondly, upper clamps 15 also give initial stability whilst drilling to establish a spud of a hole until such time a predetermined hole depth as been established. At this point the upper clamps are retracted clear of the pin pile 8.
[0061] When the power swivel has been fully retracted along the rack 13 of rack and pinion means 14, roller assembly 42 can be removed as shown in Figure 7. The remotely operable drilling apparatus 6 is now ready for deployment.
[0062] Referring to Figures 8 to 14, submersion of the remotely operable drilling apparatus 6 to an aperture 30 of submerged structure 32 will be described. The method of interconnecting the remotely operable drilling apparatus 6 to the submerged structure 32 adjacent an aperture 30 will also be described.
[0063] Firstly, buoys 40 are retrieved and guidelines 34 to which a predetermined pair of buoys 40 are attached are connected to surface vessel 2 by tensioning means. Tensioning means may for example comprise compensation air winches 54. Tension is set in guidelines 34 and this can be slackened during operations if required. The taut guidelines 34 can also be disconnected and buoyed off in the event of an emergency. An A-frame assembly 56 is used to raise the remotely operable drilling apparatus 6 into a vertical configuration and into the water as shown in Figures 8 through 10. Guidelines 34 can then be connected to eyelet 36and post guide 38B of drilling apparatus 6 as shown in Figure 20.
[0064] Referring to Figure 11 and 12, the drilling apparatus 6 is then submerged and lowered down guidelines 34 towards aperture 30 of submerged apparatus 32. Guide post 38A comes in to contact with post guide 38B and female conical guide 16 comes into contact with male conical guide 18 to locate the annular bit 24 of annular pile 8 into the aperture 30.
[0065] Referring to Figures 13 and 14, clamping means such as lower locking clamps 17 are actuated to grip the portion of submerged structure 32 around the aperture. Drilling can now commence in response to delivery of power to the power swivel 12 via cable 50 and flushing fluid via the hose 52.
[0066] Referring to Figures 15 to 20, the process of pinning a portion of submerged structure 32 around aperture 30 to the seabed, or a floor of another body of water, will be described.
[0067] Referring to Figure 15, drilling commences by powering power swivel (not shown) to rotate drive head 11 (Figure 22) and therefore rotate annular pile 8. The power swivel is drawn downwardly by a pinion rolling along rack 13. Annular bit 24 is therefore biased against the sea bed and begins to cut an annulus 60 into the rock of seabed 64. After an initial drilling to a predetermined depth, upper clamps 15 are retracted to provide space for locking collar 22 to pass through and into contact with structure 32. The drive bore in collar 22 contains a circumferential sealing arrangement (not shown) to prevent leakage or loss of pressure during either normal flushing fluid or during any grouting operations. Accordingly, flushing fluid is pumped from the service vessel via drilling apparatus 6, through the centre of annular pile 8, up through annulus 60 and out of vent holes 67 to flush out debris 59 produced by the drilling.
[0068] As can be seen from Figure 18, annular bit 24 creates an annulus 60 through which flushing fluid can pass down the centre of annular pile 8 and out up the sides of annulus 60 to lubricate and cool the annular bit 24 and remove debris 59. A flexible skirt 62 is provided on the base of submerged structure 32 to serve as a cofferdam around the annulus.
[0069] Referring to Figures 19 and 20, when the annular pile 8 is fully drilled into the seabed 64, such that annulus 60 is fully formed, grout 66 can be pumped via hose 52 and out of the delivery means of the apparatus 6 into the centre of annular pile 8. When the grout reaches down as far as the base of annular bit 24, the grout moves up annulus 60 and out into a flexible skirt 62.
[0070] Figure 20 shows the resulting configuration at the end of the grouting operation. During the grouting process, the exhaust to water is via vent holes 67 formed in the circumference of the collar around aperture 30. The vent holes ensure that the grout is pumped into the annulus between the collar and the annular pile. Flexible skirt 62 serves as a cofferdam around the outer surface of the aperture to prevent scouring of the grout should there be any leakage under the footing of the submerged apparatus 32.
[0071] Referring to Figures 21 and 22, drive head 11 of power swivel 12 can then be detached from locking collar 22 and the lower clamps 17 retracted. Drilling apparatus 6 can then be retrieved to the surface leaving annular pile 8 embedded in the seabed and sealed in grout 66 contained in the annulus 60. The locking collar 22 of pin pile 8 therefore pins a portion of structure 32 around aperture 30 to the seabed.
[0072] This process can be repeated for other apertures 30 of the structure 32. For example, referring to Figure 12, submerged structure 32 is a tripod having three apertures. The pining procedure therefore has to be repeated three times in order to attach structure 32 fully to the seabed. In an alternative embodiment, the remotely operable drilling apparatus may drill the annular pile in to the seabed, and the grouting operation may be performed after by a different apparatus.
[0073] The hole drilling operation can be controlled from a control room on vessel 2. Power and hydraulics are provided via the umbilical 50, 52 to the drilling apparatus 6. The umbilical 50, 52 can be disconnected and buoyed off in the event of rough weather and then retrieved to complete the drilling procedure. This can be done even when the drilling apparatus 6 is attached to the structure 32 at the seabed.
[0074] Referring to Figures 24 and 25, a second embodiment of a drilling apparatus 106 does not use guidelines to be located on aperture 130 of structure 132. In this embodiment, the movement of the drilling apparatus 106 can be controlled from the surface using cameras to locate the drilling apparatus 106 on aperture 130.
[0075] It will be appreciated by person skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alternations and modifications are possible without departure from the scope of the invention as defined by the appended claims.
locating a remotely operable drilling apparatus on the submerged structure adjacent an aperture arranged to receive a pile, wherein the remotely operable drilling apparatus is loaded with an annular pile comprising an annular bit at a first end thereof and a locking member at a second end thereof, the annular bit being arranged to drill an annulus into the floor into which the annular pile is to be driven and the locking member being arranged to resist removal of a portion of the submerged structure from the floor of the body of water;
operating the remotely operable drilling apparatus to drive said annular pile through the aperture and into the floor of the body of water to cut an annulus into the floor of the body of water and drive the locking member against a portion of the submerged structure around said aperture; and
filling said annulus with grout in order to retain the annular pile in said annulus and resist removal of a portion of the submerged structure from the floor of the body of water.
a) slidably interconnecting the remotely operable drilling apparatus to at least one guide line, wherein at least one said guideline is attached to the submerged structure at a location adjacent an aperture arranged to receive a pile, and lowering the remotely operable drilling apparatus along at least one said guideline whilst the at least one said guide line is pulled taut;
b) moving guide means disposed on the base of the remotely operable drilling apparatus into contact with a portion of the submerged structure adjacent an aperture arranged to receive a pile to align said annular bit with said aperture; or
c) operating first clamping means to clamp said remotely operable drilling apparatus to the submerged structure adjacent said aperture.
d) attaching drive means of the remotely operable drilling apparatus to the annular pile and operating the drive means to rotate and push the annular pile into the floor of the body of water; or
e) pumping flushing fluid through said annular pile to remove cuttings from a drilled annulus and provide lubrication and cooling to said annular bit.
f) disconnecting the remotely operable drilling apparatus from the submerged structure and retrieving the remotely operable drilling apparatus to a surface vessel;
g) loading a further annular pile on said remotely operable drilling apparatus and repeating the method of any one of claims 1 to 5 on a further aperture of said submerged structure.
locating means arranged to remotely move into engagement with a submerged structure adjacent an aperture arranged to receive a pile;
drive means arranged to drive an annular pile into a floor of a body of water, wherein the annular pile comprises an annular bit at a first end thereof and a locking member at a second end thereof, the annular bit being arranged to drill an annulus into the floor into which the annular pile is to be driven and the locking member arranged to resist removal of a portion of the submerged structure from the floor of the body of water.
h) guide means disposed on the base of the remotely operable drilling apparatus, the guide means arranged to align said annular bit with an aperture arranged to receive the pile; or
i) clamping means for clamping said remotely operable drilling apparatus to the submerged structure adjacent said aperture arranged to receive a pile.
j) a power swivel comprising a drive head arranged to releasably engage with and rotate said annular pile;
k) rack and pinion means arranged to move said power swivel towards the floor of a body of water; or
l) retractable support clamping means arranged to hold said annular pile in the remotely operable drilling apparatus before drilling and provide stability during drilling.
a remotely operable drilling apparatus according to any one of claims 6 to 10; and
umbilical means arranged to provide hydraulic and/or electrical power from a surface vessel to said remotely operable drilling apparatus and to provide flushing fluid and/or grout to said delivery means from a surface vessel.
m) adapter means arranged to enable the umbilical means to be disconnected from the surface vessel and attached to a buoy;
n) pumping means disposed on a surface vessel and arranged to pump flushing fluid and/or grout to said delivery means via said umbilical means; or
o) at least one guide line attached to the submerged structure at a location adjacent an aperture arranged to receive a pile, at least one said guide line arranged to be interconnected to said remotely operable drilling apparatus to guide the remotely operable drilling apparatus to a location on said submerged structure adjacent an aperture arranged to receive a pile whilst the at least one said guide line is pulled taut.
a shaft comprising outer and inner concentric cylindrical sleeves defining an annular channel therebetween;
an annular bit mounted to a first end of the shaft; and
a locking member mounted to a second end of the shaft;
wherein a path for fluid flow is defined from a first opening in the locking member, through said annular channel and through a second opening defined by said inner sleeve.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description