[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.
[0024] This provides the advantage of reducing the time taken to conduct a piling operation.
[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.
1. 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.
2. A method according to claim 1, wherein 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.
3. A method according to claim 1 or 2, wherein 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.
4. A method according to any one of the preceding claims, wherein the step of filling
said annulus with grout in order to retain the annular pile in said annulus comprises
operating delivery means of the remotely operable drilling apparatus to fill said
annulus with grout.
5. A method according to any one of the preceding claims, further comprising 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 of any one of claims 1 to 5 on a further aperture of said submerged
structure.
6. 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.
7. An apparatus accoriding to claim 6, further comprising 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.
8. An apparatus according to claim 6 or 7, further comprising 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.
9. An apparatus according to claim 8, wherein said guide means comprises a female conical
portion arranged to abut a corresponding male conical portion disposed around said
aperture arranged to receive a pile.
10. An apparatus according to any one of claims 6 to 9, wherein 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.
11. 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 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.
12. A system according to claim 11, further comprising 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.
13. A system according to claim 12, further comprising tensioning means arrange to pull
at least one said guide line taut.
14. 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.
15. An annular pile according to claim 14, wherein said annular bit is mounted to said
outer sleeve and the second opening is defined by an end of the inner sleeve.