Note: Descriptions are shown in the official language in which they were submitted.
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SLIP ASSEMBLY FOR SUBSEA TE~PLATE
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention pertains to a hydraulically
actuated slip assembly for securing a subsea well structure
such as a drilling template or the like to a pile or
support column.
Background
In the art of developing offshore petroleum
deposits and the like it has become particularly important
to be able to locate and properly anchor structures such
as drilling and foundation templates to the seabed so that
additional structures such as wellheads, guide bases and
the like can be properly located on or connected to the
templates. In this regard, there has been a need to
provide an improved apparatus for securing such templates
to the template support columns or piles in a manner which
will permit final levelling and adjustment of the template
or similar structure but which will also provide for
adequately connecting the template to the piles to be
securely anchored and supported thereby. The present
invention pertains to an improved slip assembly for
lnterconnecting a subsea template to a pile or similar
types of support column, which slip assembly may be
actuated by remote oontrol to form a supporting connection
between the pile and the template structure.
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SUMMARY OF THl~ INVENTION
The present in~ention provides improved apparatus for
interconnecting a pile or support column with a subsea well structure
such as a drilling template or the like wherein the template may be
disposed in a predetermined position and supported by one or more of
said piles. In accordance with one aspect of the invention there is
provided a hydraulically actuated slip assembly mounted on a subsea
template structure and adapted to receive and forcibly grip a support
pile member to form the supporting connection between the pile and the
structure to be supported by the pile.
The present invention further provides a slip assembly
comprising a slip bowl having an inwardly facing conical surface, a
series of slip segments arranged ~or limited movement axially and
radially with respect to the axis of the conical surface, and a fluid
operated piston and cylinder type actuator disposed to move the slip
segments so that the corresponding radial mo~ement determined by the
conical surface causes the slip segments to move into or out of gripping
engagement with a cylindrical pile member. The slip bowl is mounted
on a supporting frame for limited axial and radial movement ,vith respect
2~ to the central axis of the slip assembly to provide for alignment with
the axis of the pile. The slip assembly further includes a guide funnel
for guiding a cylindrical pile into alignment with the slip bowl during
insertion of the pile.
In accordance with one embodiment of the present invention
the piston and cylinder type actuator may be of an annular
configuration surrounding the pile and adapted to be generally coaxial
with the axis of the slip bowl. In accordance with another embodiment
of the present invention the piston and cylinder type actuator may
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include a plurality of separate piston and cylinder assemblies spaced
apart in surrounding relationship to the pile and engageable with the
slip members through a connecting member.
In accordance with a still further aspect of the present
invention the slip assembly includes an improved mechanism
interconnecting the slip segments with the slip actuator and a unique
mounting arrangement of the actuator to accommodate and enhance the
self aligning characteristics of the slip assembly. The slip assembly is
also provided with a locating and mounting flange, preferably disposed
at one end of the assembly, for forming a connecting element for
mounting the slip assembly on a subsea template or the like.
The present invention further contemplates the provision of a
subsea template in combination with one or more pile slip assemblies of
the type disclosed herein and wherein the template is adapted for
driving the pile through a receiving sleeve in the template, moving the
template vertically with respect to the pile, and then gripping the pile
with the slip assemblies in accordance with the present invention.
Those skilled in the art will appreciate the features of the
invention described hereinabove as well as other superior aspects of the
invention upon reading the detailed description which follows in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic illustration showing the installation OI
a subsea template using a semi-submersible drilling rig;
Figure 2 is a schematic diagram of a portion of the drilling
rig shown in Figure 1 and showing an arrangement on the drilling rig
which is used to level the template;
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Figure 3 is a longitudinal central section view of one
embodiment of a pile slip assembly wherein the left half of the view
shows the assembly iJI an engagcd condition and the right half shows
the assembly in a retracted condi.ion with respect to a cylindrical pile;
Figure 4 is a section view taken along line 4-4 of ~igure 3
showing the slip segments in the position shown in the left side of
Figure 3;
Figure 5 is a side elevation, partially sectioned, of an
alternate embodiment of a slip assembly in accordance with the present
; invention; and
Figure 6 is a detail section view taken along the line 6-6 of
Figure 5.
DESCRIPTlON OF T~IE PREFEnRED EMBODII~IENTS
In the description which follows like parts are marked
throughout the specification and drawings with the sarne reference
numerals, respectiYely. The drawings are not necessarily to scale and
certain features of the invention may be shown in schematic or
diagrammatic form in the interest of clarity and conciseness.
The slip assembly of the present invention ~vill be described
in conjunction with some of the steps involved in an improved procedure
for lowering and levelling a subsea template from a semi-submersible
drilling rig. Referring to Figure 1, there is illustrated a seagoing
semi-submersible drilling rig, generally designated by the numeral 10,
which is shown in position for lowering a drilling template 12 toward a
seabed 13. The drilling rig 10 is preferably of the submersible hull
column stabili~ed type. The template 12 is preferably suspended from a
derrick 11 on the rig and by a suitable riser string 15 suspended from
the derrick. The liser string 15 typically e~tends through a rotary
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table 18 mounted on a deck or platform 19, as shown in l~igure 2. The
d~lling rig 10 is a~so of a type which includes suitable (Irill stem
hoisting and rotating apparatus associated with the derrick 11 for
handling a drill stem in a conventional manner for performing clrilling
5operations and for handling elongated risers or tubing strings. The
rig 10 is also adapted to utilize the aforementioned hoisting apparatus
or additional apparatus for raising and lowering structures such as the
' template 12. The template 12 is similar in some respects to known
types of skeletal framelike structures used as support frames for subsea
10well drilling and development applications. As shown in Figure 2, the
template 12 includes four spaced apart vertical tubular pile receiving
sleeves 24 interconnected by suitable frame members 25 and 26. The
template 12 may inciude additional structure, depending on its specific
purpose.
15When the drilling rig 10 is disposed in the desired installation
position for the template 12, the template is properly oriented and then
lowered, using suitable cables or the riser string 15 ' and a sling
assen~bly 21, as shown in Figure 2. The sling 21 is connected to the
template 12 at points which will preferably place the center of gravity
20of the template directly below the riser string 15. ~'hen the template
12 reaches seabed 13 weight on the riser string 15 is slacked off in
increments of approximately 50,000 lbs., for e~;ample9 until all of the
weight is off the riser string and then an additional length of about 30
ft. is slacked off to accommodate settling of the template and assure
25that there is slack in the lowering structure. If the template is
reasonably level, the lifting slings 21 are released and recovered.
At this point, typically, guidance and verification of template
position is planned and carried out as a three phase program described
in United States Patent No. 4,435,108 which issued to
J.E, ~ampton on March 6 r 1984. The guidance phase includes
guidance during initial set down and may include an
acoustic or sonar type system for determining the exact
location of the template using hardwired connections
between the drilling rig and the template. Additionally,
inclinometer and gyro devices on board the template and
hardwired to the drilling rig may be utilized for providing
information during levelling and orientation of the
template.
When the drilling t mplate 12 has been accurately
positioned on the seabed 13 suitable elongated columnlike
support members or piles 22 are inserted through the
respective pile receptacles or sleeves 24 in the template
12~ see Figure 2, in the process of securing the template
to the seabed. It may be required to drill a pile
r~ceiving hole before lowering one or more of the piles 22
and also perform cementing operations after the pile or
piles have been lowered and placed in the receiving
2~ holes. These operations may be carried out in a generally
conventional manner but may be done wi~h the slip
assemblies of the present invention in place on the
template by lowering the drill stem through the slip
assemblies. Preferably, if the template is more than
about two degrees out of level, a suitable tensioning
line is connected from a low point on the template to a
tensioner assembly on the drilliny rig and ~he template
is then levelled to within the required accuracy.
Template levelling can also be carried out using
3Q a heave compensator on board the drilling rig 10 or a
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similar suitable vessel, generally as follows. Referring
to Figure 2 there is illustrated in somewhat schematic
form a portion of the rig 10 including the derrick 11
having a suitable heave compensator mechanism 30 suspended
therefrom. The levelling procedure is usually carried out
after all piles 22 have been drilled, if necessary, run to
position and cemented in
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position and suitable hydraulic lines have been run from the rig 10 to
the template 12 for controlling the operation of the improved pile slip
assembly of the present invention. Figure 2 also illustrates a hydraulic
control pod 32 connected to a suitable pod receptacle 34 with attendant
hydraulic conduits running from the rig 10 through the pod to each of
- the slip assemblies which are respectively designated by the numeral
40. The control pod and receptacle may be of a general type
commercially available, and comprising no part of the present invention
per se are not believed to require a detailed description. The levelling
procedure is described in detail in a copending application filed
concurrently herewith and incorporated by reference herein. lIowever,
basically the levelling procedure is carried out also using r;ser string
suitably connected to the template 12 at its center of gravity
through sling 21, for example, and a tensioning line 36 attached to one
corner of the template as indicated schematically in Figure 2. The riser
string 15 is connected to bails 17 suspended from the hook of heave
compensator 30. The tensioning line 36 is trained upward and is
connected to the drum of a constant torque fluid operated winch 38
mounted on a frame 39 supported on the upper end of the riser string
15.
In Figure 2, the slip assemblies 40 are shown in place
supported on top of each of the sleeves 24. The slip assemblies 40 are
each provided with a frame having a lower transverse mounting flange
41 adapted to be supported on and bolted or otherwise secured to a
cooperating flange 43 secured to the top of each of the pile sleeves 24.
The slip assemblies 40 are hydraulically actuated to grip or release the
associated piles 22 which are disposed in the pile sleeves 24 and are
supplied with hydraulic fluid through the control pod 32 and receptacle
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34. The control pod receptacle 34 is suitably supported on the template
and interconnected with cach of the slip assemblies by way of suitable
hydraulic con$rol lines 35 and 37. Accordingly, the slip assemblies ~0
may be individually remotely controlled from the surface or other remote
location to secure or release the slip assemblies with respect to the
piles disposed therein once the template has been positioned~ Once the
template 12 is properly levelled with each of the piles in place the slip
assemblies 40 are suitably actuated to grip the respective piles to
secure the template to the piles in the preferred position. Thanks to
~ the arrangement of pile gripping members of the slip assemblies ~0,
which will be described in further detail herein, the weight of the
template is effective to somewhat self-energize the slip assemblies to
secure the templatè to the pilings once the gripping members are
forcibly engaged with the pile regardless of whether or not hydraulic
fluid is continuously supplied to the templates.
Referring to Figure 3, one preferred embodiment of a slip
assembly 40 according to thb present invention is illustrated in a split
longitudinal section view. The slip assem~ly 40 is adapted to surround
a pile 22 and to grippingly engage the pile as will be evident from the
following description. The slip assembly 40 includes a frame comprising
upper and lower ring shaped abutment plates 51 and 53, respectively,
which are secured to and spaced apart by a cylindrical tu~ular wall
member 52. An annular slip bowl 54 is disposed within the enclosure
formed by the frame plates 51 and 53 and includes upper and lower
plates 55 and 57 which are spaced apart by an outer cylindrical wall 58
and a conically tapered inner wall 60. The slip bowl 54 fits loosely
between the plates 51 and 53 and is operable to center itself radially
with respect to the longitudinal central a~is 47 of the slip assembly
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which coincides in the view of Figure 3 with the central axis of a pile
22. The slip bowl 54 is also operable to move axially and to tilt with
respect to the central axis of the slip assembly within the limits imposed
by the frame plates 51 and 53 to accommodate some skew misalignment of
the pile with respect to the slip assembly.
The lower plate 53 is supported by a cylindrical tubular frame
; member G1 which is sccllred to a mounting ring 63 and defines a
receptacle 45 in which the pile 22 is disposed together with an actuator
for the slip assembly to be described herein. The mounting ring 6~ is
supported by and secured to a base plate 64. The base plate 64 is
supported on and secured to a sleeve 66 and the locating flange 41 by
a plurality of radially extending gusset plates 68. Referring further to
~igure 3 the slip assembly 40 is also provided with a cylindrical outer
housing member 72 disposed around the frame portion formed by the
plates 51 and 53 and fixed thereto by a plurality of radially projecting
gusset plates 65, opposed ones of which are shown in Figure 3. The
gussets 65 are also secured to lower and upper conical plates 73 and
74, disposed below and above the housing member 72, as shown. The
conical plate 74 forms a guide funnel for guiding a pile 22 into the
central receptacle in the frame of the slip assembly.
Referring to Figures 3 and 4, the slip assembly 40 is also
provided with a plurality of slip segments 76 which are disposed
generally within the tapered slip bowl wall 60 in surrounding
relationship to the pile 22. The segments 76 are preferably formed of
case hardened steel and are arranged to engage the pile 22 as shown
by the position of one of the slip segments on the left side of the
central axis 47 of the slip assembly in rigure 3. The slip segments 76
are each in the form of a circular segment or sector portion, are
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preferably provided eight in numbcr and are irlterconllected and biased
outwardly against the wall 60 by suitable annular resilient retaining
springs 75 fitted in cooperating grooves in the inner wall surfaces of
the slip segments. The springs 75 may be formed as a resilient steel
split ring, for example, not unlike a piston ring and operable to bias
the slip segments radially outward with respect to the axis 47 against
the inner wall 60 of slip bowl 54. The segments 76 include a sloping
outer wall 79 and a cylindrical inner wall 81, the latter being provided
with a series of gripping teeth or serrations for gripping the surface of
the pile 22. As shown in Figures 3 and 4, the se~ments 76 are also
provided with slots 77 formed in the opposed sidewalls of the segments.
The slots 77 are adaptecl to receive link means comprising oppositely
projecting trunnions 78 which are attached to spaced apart brackets 80
mounted on a circular guide ring 82.
The slip assembly 40 further includes hydraulic actuator
means comprising an annular hydraulic cylinder 83 having a lower head
member 84 which is supported on an anti-friction ball bearing assembly
including a ball housing 86 supported on the base plate G4 and adapted
to include bearing elements 87. The cylinder 83 is adapted to form a
chamber 85 having an annular piston 88 disposed therein and connected
to a piston rod portion ~9 which is vertically extendable and retractable
with respect to the cylinder through an upper head member 9û and is
in supportive relationship with the guide ring 82. Pressure fluid is
supplied to cylinder 83 to act alternately on opposed faces of the piston
88 through suitable conduits 91 and 92, respectively.
In response to application of pressure fluid into the portion
of annular cylinder chamber 85 formed below the piston 88, viewing
Figure 3, the guide ~ing 82 is moved upwardly which in turn moves the
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slip segments 76 against the tapered inner wull 60 to force the segments
radially inwardly into gripping engagement with the ou~er
circumferential surface of the pile 22. Thus, the effect of increased
hydraulic pressure in the lov,~er chamber of the cylinder 83 is to force
the slips segments 76 inwardly against the resistance of the retaining
springs 75 into gripping engagement with the pile as the upper slip
bowl plate 55 is forced into engagement with the frame plate 51.
Thanks to the arrangement of the floating slip bowl 54 some
misalignment of the pile 22 with respect to the central longitudinal axis
of the slip assembly may be tolerated when the slip assembly is mounted
on a template such as the template 12. The cylinder 83 may also
undergo lateral excursion with respect to the central axis 47 of the slip
assembly to accommodate movement of the slip bowl and the slip
segments. In the retracted condition of the slip segments 76 the upper
edges of the segments norr.~ally remain engaged with the slip bowl 54 as
shown by the view to the right of the central axis in Figure 3.
Referring now to Figures 5 and 6, an alternate embodiment of
a slip assembly is illustrated and generally designated by the numeral
100. The slip assembly 100 includes several components which are
identical to corresponding components in the slip assembly 40. The slip
assembly 100 also includes components which are generally functional
counterparts of the components of the slip assembly ~0 and each of
which are designated with the same reference numeral but having a
suffix "a". The slip assembly 100 includes a plurality of separate
hydraulic cylinder assemblies 102 which are spaced apart
circumferentially within the chamber formed by a frame tube Gla. The
cylinder assemblies 1~2 include piston rods 10~ which are connected to a
guide ring 82 having brackets 80 with trunnions 78 slidable in radially
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extending slots 77 in slip segmen-ts 76 corresponding to the arrangement
of the slip asscmbly 40. The cylinder assemblies 102 are preferably
double acting mechanical locking type and are interconnected by a
suitable hydraulic circuit, not shown, in parallel with each other
wherein each of the associated piston rods 104 may be extended under
the same urging force to cause the slip segments 76 to move radially
inwardly as they engage the inner wall 60 of the slip bowl 54 to move
into gripping engagement with a pile 22. The cylinder assemblies 102
are preferably provided three in total number spaced apart equidistant
with respect to each other around the central axis 47a of the slip
assembly 100, as shown in Figure 6. Each cylinder assembly 102 is also
mounted on frame plate 64a by a ball and socket or knuckle joint 86a to
permit limited pivotal movement of the cylinder assemblies to
accommodate radial displacement of the slip bowl 54 in the event the pile
22 is misàligned with respect to the slip assembly 100. The operation
of the slip assembly lO0 is similar to that of slip assembly 40. The
frame plate 64a is welded directly to a sleeve 66a and to frame member
61a. A tubular sleeve 107 extends upward from plate 64a and is
adapted to support a running tool during pile hole drilling operations
and to prevent back flow of drill cuttings into the interior receptacle
45a of the slip assembly in the vicinity of the actuators 102 which, if
allowed to occur, might impair their operability.
The slip assembly 100 is adapted for use with relatively large
diameter piles, larger than approximately 20 inches nominal diameter.
This is due to the fact that the annular cylinder and piston
arrangement for the slip assembly 40 is more difficult to design for
suitable operation with larg~er diameter piles. For pile sizes smaller
than approximately 20 inches diameter the annular cylinder configuration
.
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of the slip assembly 40 is preferred since the space available to house
the multiple cylinders 102 typically becomes too small. The slip
assembly 100 includes a mounting flange 41 for securing~ the slip
assembly to the flange 43 of a pile sleeve 24 as shown in Figure 5. A
major advantage of the slip assemblies 40 and 100 is that they allow for
dlilling operations to tal~e place through the slip assembly as well as
the subsequent driving of a pile through the slip assembly.
One way of releasing the slip assemblies 40 or 100 from the
piles 22 would be to pull upward on the template 12 to release the
downward force of the slip bowl 54 on the slip segments while reversing
the direction of movement of the actuators 83 or 102 to allow the
annular springs 75 to urge the slip segments 76 radially outward while
they are pulled axially downward, viewing Figures 3 and 5,
respectively.
Those skilled in the art will appreciate that various
substitutions and modifications may be made to the embodiments of the
invention described herein without departing from the scope and spirit
of the invention as recited in the appended claims.
~'~hat I claim is:
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