U.S. patent application number 15/344204 was filed with the patent office on 2017-05-11 for installation assembly for a subsea wellhead.
This patent application is currently assigned to Vetco Gray, Inc.. The applicant listed for this patent is Vetco Gray, Inc.. Invention is credited to Samved Bhatnagar, Jonathan Clark, Robert K. Voss.
Application Number | 20170130547 15/344204 |
Document ID | / |
Family ID | 57543140 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170130547 |
Kind Code |
A1 |
Bhatnagar; Samved ; et
al. |
May 11, 2017 |
INSTALLATION ASSEMBLY FOR A SUBSEA WELLHEAD
Abstract
A system for load transfer from a wellhead to the sea bed
adjacent a subsea well, including a suction pile for securing to
the sea bed, and a wellhead housing assembly having a longitudinal
axis and attached to the suction pile, the wellhead housing for
subjection to an axial load acting in a direction parallel to the
longitudinal axis, and a bending load acting in a direction not
parallel to the longitudinal axis. The system further includes a
suction pile connector that transmits the axial load and the
bending load from the wellhead housing through the suction pile
toward the sea bed, and that is attached to the suction pile, the
suction pile connector engaged with the wellhead housing to
substantially maintain the relative positions of the wellhead
housing and the suction pile.
Inventors: |
Bhatnagar; Samved; (Houston,
TX) ; Clark; Jonathan; (Houston, TX) ; Voss;
Robert K.; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vetco Gray, Inc. |
Houston |
TX |
US |
|
|
Assignee: |
Vetco Gray, Inc.
Houston
TX
|
Family ID: |
57543140 |
Appl. No.: |
15/344204 |
Filed: |
November 4, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62251803 |
Nov 6, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 7/12 20130101; E21B
33/00 20130101; E21B 17/02 20130101; E02D 5/22 20130101; E21B
33/038 20130101 |
International
Class: |
E21B 33/038 20060101
E21B033/038; E02D 5/22 20060101 E02D005/22 |
Claims
1. A system for load transfer from a wellhead to the sea bed
adjacent a subsea well, comprising: a suction pile for securing to
the sea bed; a wellhead housing having a longitudinal axis and
attached to the suction pile, the wellhead housing for subjection
to an axial load acting in a direction parallel to the longitudinal
axis; and a suction pile connector that transmits the axial load
from the wellhead housing through the suction pile toward the sea
bed, and that is attached to the suction pile, the suction pile
connector engaged with the wellhead housing to substantially
maintain the relative positions of the wellhead housing and the
suction pile.
2. The system of claim 1, wherein the suction pile connector
substantially circumscribes the wellhead housing and has an inner
surface defining a recess, and wherein the suction pile connector
further comprises a dog connector positioned in the recess and
movable toward the longitudinal axis of the wellhead housing into
engagement with the wellhead housing to restrict relative axial
movement between the suction pile connector and the wellhead
housing.
3. The system of claim 2, wherein the dog connector has teeth
extending toward the wellhead housing to engage the wellhead
housing.
4. The system of claim 3, wherein the wellhead housing has an outer
surface with ridges positioned to correspond to the teeth so that
when the dog connector moves into engagement with the wellhead
housing, the teeth of the dog connector engage the ridges of the
wellhead housing.
5. The system of claim 4, wherein the teeth of the dog connector
each have a lower surface, and the ridges of the wellhead housing
each have an upper surface, and when the axial load is applied to
the system, the lower surfaces of the teeth engage with the upper
surfaces of the ridges so that the axial load is transmitted from
the wellhead housing to the suction pile connector through the dog
connector.
6. The system of claim 2, wherein the dog connector is
hydraulically actuated.
7. The system of claim 2, wherein the dog connector is mechanically
actuated.
8. A system for load transfer from a wellhead to the sea bed
adjacent a subsea well, comprising: a suction pile for securing to
the sea bed; a wellhead housing having a longitudinal axis and
attached to the suction pile, the wellhead housing for subjection
to a bending load acting in a direction not parallel to the
longitudinal axis; and a suction pile connector that transmits the
bending load from the wellhead housing through the suction pile
toward the sea bed, and that is attached to the suction pile, the
suction pile connector engaged with the wellhead housing to
substantially maintain the relative positions of the wellhead
housing and the suction pile.
9. The system of claim 8, wherein the wellhead housing has an outer
surface with an outwardly directed shoulder.
10. The system of claim 9, wherein the suction pile connector has
an inner surface with an inwardly directed shoulder positioned to
correspond to the outwardly directed shoulder of the outer surface
of the wellhead housing.
11. The system of claim 10, wherein when the bending load is
applied to the wellhead housing, rotational movement of the
wellhead housing relative to the suction pile connector is
restricted by engagement of the outwardly directed shoulder of the
outer surface of the wellhead housing with the inwardly directed
shoulder of the suction pile connector.
12. The system of claim 10, wherein the wellhead housing is
subjected to an axial load acting in a direction parallel to the
longitudinal axis, and the suction pile connector transmits the
axial load from the wellhead housing through the suction pile
toward the sea bed.
13. The system of claim 12, wherein the suction pile connector
substantially circumscribes the wellhead housing and has an inner
surface defining a recess, and wherein the suction pile connector
further comprises a dog connector positioned in the recess and
movable toward the longitudinal axis of the wellhead housing into
engagement with the wellhead housing to restrict relative axial
movement between the suction pile connector and the wellhead
housing.
14. The system of claim 13, wherein the dog connector has teeth
extending toward the wellhead housing to engage the wellhead
housing, and the wellhead housing has an outer surface with ridges
positioned to correspond to the teeth.
15. The system of claim 14, wherein when the bending load is
applied to the wellhead housing, rotational movement of the
wellhead housing relative to the suction pile connector is
restricted by engagement of the outwardly directed shoulder of the
outer surface of the wellhead housing with the inwardly directed
shoulder of the suction pile connector, and the teeth of the dog
connector do not contact the ridges of the wellhead connector.
16. A method of transmitting a load from well equipment to a sea
floor, the method comprising: a) coupling the well equipment to a
suction pile using a suction pile connector, the suction pile
connector defining a recess with a dog connector, the dog connector
having at least one tooth for engagement with the well equipment;
b) transmitting an axial load from the well equipment to the dog
connector via the tooth of the dog connector; c) transmitting the
axial load from the dog connector to the suction pile connector; d)
transmitting the axial load from the suction pile connector to the
suction pile; and e) transmitting the axial load from the suction
pile to the sea floor.
17. The method of claim 16, wherein the well equipment has a
shoulder and the suction pile connector has a corresponding
shoulder, the method further comprising: transmitting a bending
load from the well equipment to the suction pile connector via the
well equipment shoulder and the suction pile connector
shoulder.
18. The method of claim 17, further comprising: transmitting the
bending load from the suction pile connector to the suction pile;
and transmitting the bending load from the suction pile to the sea
floor.
19. The method of claim 16, further comprising: f) prior to step
b), driving the at least one tooth of the dog connector into
engagement with the well equipment using hydraulic or mechanical
force.
20. The method of claim 19, wherein the well equipment at least one
ridge on an outer surface thereof, and step f) further comprises:
driving the at least one tooth of the dog connector into engagement
with the at least one ridge of the outer surface of the well
equipment.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of,
co-pending U.S. Provisional Application Ser. No. 62/251,803, filed
Nov. 6, 2015, the full disclosure of which is hereby incorporated
herein by reference in its entirety for all purposes.
BACKGROUND
[0002] Field of Invention
[0003] This invention relates in general to equipment used in the
hydrocarbon industry, and in particular, to systems and methods for
subsea drilling operations.
[0004] Description of the Prior Art
[0005] Typical subsea drilling operations include a drilling vessel
and an arrangement of equipment to accomplish the first drilling
phase of a well. In many known systems, for example, the first
phase of the drilling operation may include jetting. Jetting is a
process wherein a jetting tool, enclosed within a casing, is placed
adjacent the sea floor. Fluid is sprayed through the end of the
jetting tool and directed at the sand on the sea floor. The fluid
is turbulent and stirs up the sand, which mixes with the fluid and
is carried up the casing away from the bottom of the casing. When
the sand is thus removed, the casing is lowered into the void left
behind. This process is continued until the casing reaches a
predetermined depth, after which equipment related to the next
phase of drilling (i.e. a high pressure housing, blow out
preventer, marine riser, etc.) is connected.
[0006] Jetting and other operation typically require heavy
equipment, which is handled by a drilling rig, often mounted to a
vessel or platform at the sea surface. Certain exploratory or other
types of drilling operations, however, can lower operational costs
by enabling a flexible approach to well construction that can be
carried out by a smaller vessel needing less infrastructure and
space to support heavy equipment. Using this method, the wellhead
can be installed using a suction pile. Such a method typically
requires installation of the wellhead on the suction pile, or a
frame that consists of multiple suction piles, at the surface, and
then lowering the suction pile to the sea floor.
[0007] One problem that can occur in known system relates to the
reduction in weld life of the joints in the low and high pressure
housing of the wellhead. The welds connecting the respective
casings to the low and high pressure housing can be subjected to
frequent cyclic loading caused by equipment connected to the
wellhead, such as the BOP, riser, tensioners, etc., and the side
loading subjected by wave currents, drift of the ship in the sea,
etc. Over time, such axial and bending forces degrade the welded
connections between the low and high pressure housing of the
wellhead and the respective casings, leading to failure and a
potential risk for hydrocarbons to leak to the surface during
drilling or production. In addition, the weld locations are also
not very accessible post-installation of the wellhead to the seabed
and hence, difficult to repair.
SUMMARY
[0008] One embodiment of the present technology provides a system
for load transfer from a wellhead to the sea bed adjacent a subsea
well, including a suction pile for securing to the sea bed, and a
wellhead housing having a longitudinal axis and attached to the
suction pile, the wellhead housing for subjection to an axial load
acting in a direction parallel to the longitudinal axis. The system
further includes a suction pile connector that transmits the axial
load from the wellhead housing through the suction pile toward the
sea bed, and that is attached to the suction pile, the suction pile
connector engaged with the wellhead housing to substantially
maintain the relative positions of the wellhead housing and the
suction pile.
[0009] Another embodiment of the present technology provides a
system for load transfer from a wellhead to the sea bed adjacent a
subsea well, including a suction pile for securing to the sea bed,
and a wellhead housing having a longitudinal axis and attached to
the suction pile, the wellhead housing for subjection to a bending
load acting in a direction not parallel to the longitudinal axis.
The system further includes a suction pile connector that transmits
the bending load from the wellhead housing through the suction pile
toward the sea bed, and that is attached to the suction pile, the
suction pile connector engaged with the wellhead housing to
substantially maintain the relative positions of the wellhead
housing and the suction pile.
[0010] Yet another embodiment of the present technology provides a
method of transmitting a load from well equipment to a sea floor.
The method includes coupling the well equipment to a suction pile
using a suction pile connector, the suction pile connector defining
a recess with a dog connector, the dog connector having at least
one tooth for engagement with the well equipment, and transmitting
an axial load from the well equipment to the dog connector via the
tooth of the dog connector. The method further includes
transmitting the axial load from the dog connector to the suction
pile connector, transmitting the axial load from the suction pile
connector to the suction pile, and transmitting the axial load from
the suction pile to the sea floor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present technology will be better understood on reading
the following detailed description of non-limiting embodiments
thereof, and on examining the accompanying drawings, in which:
[0012] FIG. 1 is a side schematic view of a drilling operation
according to an embodiment of the present technology;
[0013] FIG. 2 is an isometric view of a suction pile connector and
associated elements according to an embodiment of the present
technology;
[0014] FIG. 3 is an enlarged side cross-sectional view of the
section pile connector of FIG. 2 taken along line 3-3 of FIG.
2;
[0015] FIG. 4 is an enlarged side cross-sectional view of an
interface between a wellhead housing and a suction pile connector
according to another embodiment of the present technology;
[0016] FIG. 5 is an alternate view of the enlarged side
cross-sectional view of the interface between the wellhead housing
and the suction pile connector of FIG. 4;
[0017] FIG. 6 is an alternate view of the enlarged side
cross-sectional view of the interface between the wellhead housing
and the suction pile connector of FIG. 4 when under an axial
load;
[0018] FIG. 7 is an alternate view of the enlarged side
cross-sectional view of the interface between the wellhead housing
and the suction pile connector of FIG. 4 when under a bending load;
and
[0019] FIG. 8 is an alternate view of the enlarged side
cross-sectional view of the interface between the wellhead housing
and the suction pile connector of FIG. 4 when under both an axial
and a bending load.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The foregoing aspects, features and advantages of the
present technology will be further appreciated when considered with
reference to the following description of preferred embodiments and
accompanying drawings, wherein like reference numerals represent
like elements. In describing the preferred embodiments of the
technology illustrated in the appended drawings, specific
terminology will be used for the sake of clarity. The invention,
however, is not intended to be limited to the specific terms used,
and it is to be understood that each specific term includes
equivalents that operate in a similar manner to accomplish a
similar purpose.
[0021] Embodiments of this disclosure provide systems and methods
of installing a wellhead assembly using a suction pile and enabling
a more robust transfer of installation and operational loads to the
sea bed during the entire life cycle of the well. During
exploration, utilization of such a wellhead assembly configuration
enables operators to use a lower day-rate vessel for construction
of the well before the drilling activity and allows, for example,
for lower cost drilling.
[0022] FIG. 1 shows a side schematic view of a subsea drilling
operation, according to one example embodiment of the present
technology. The drilling operation includes a vessel 10 floating on
the sea surface 12 substantially above a wellbore 14. A wellhead
housing 16 sits at the top of the wellbore 14 and is connected to a
blowout preventer (BOP) assembly 18, which may include shear rams
20, sealing rams 22, and/or an annular ram 24. One purpose of the
BOP assembly 18 is to help control pressure in the wellbore 14. The
BOP assembly 18 is connected to the vessel 10 by a riser 26. During
drilling operations, a drill string 28 passes from a derrick 30 on
the vessel 10, through the riser 26, through the BOP assembly 18,
through the wellhead housing 16, and into the wellbore 14. The
lower end of the drill string 28 is attached to a drill bit 32 that
extends the wellbore 14 as the drill string 28 turns. Additional
features shown in FIG. 1 include a mud pump 34 with mud lines 36
connecting the mud pump 34 to the BOP assembly 18, and a mud return
line 38 connecting the mud pump 34 to the vessel 10. A remotely
operated vehicle (ROV) 40 can be used to make adjustments to,
repair, or replace equipment is necessary. Although a BOP assembly
18 is shown in the figures, the wellhead housing 16 could be
attached to other well equipment as well, including, for example, a
tree, a spool, a manifold, or another valve or completion
assembly.
[0023] One efficient way to start drilling a wellbore 14 is through
use of a suction pile 42. Such a procedure is accomplished by
attaching the wellhead housing 16 to the top of the suction pile 42
and lowering the suction pile 42 to the sea floor 44. As interior
chambers in the suction pile 42 are evacuated, the suction pile 42
is driven into the sea floor 44, as shown in FIG. 1, until the
suction pile 42 is substantially submerged in the sea floor 44 and
the wellhead housing 16 is positioned at the sea floor 44 so that
further drilling can commence. As the wellbore 14 is drilled, the
walls of the wellbore are reinforced with concrete casings 46 that
provide stability to the wellbore 14 and help to control pressure
from the formation.
[0024] More specifically, the wellhead assembly, including the
wellhead housing 16, is mounted on top of the suction pile 42 and
held axially while lowering to the sea floor 44. Depending on the
soil conditions, in certain cases, only a low pressure housing may
be mounted on top of the suction pile while the high pressure
housing is installed in a secondary drilling and cementing
operation. Once the suction pile 42 and wellhead assembly reaches
the seabed, an ROV can shut off the water access hatch and actuate
a valve to pump fluid from within the suction pile 42, and enable
the suction pile 42 to be installed in the seabed. The wellhead
assembly can be installed on a single suction pile 42 or on a frame
that consists of multiple suction piles 42. The suction pile(s) 42
can have a greater outer diameter than the cemented casing 46 that
extends into the well. As an example the cemented casing 46 can
have a maximum outer diameter of 36 inches while a suction pile 42
can have an outer diameter of up to 20 feet, or can include one or
more piles with an outer diameter of 20 feet or more.
[0025] Referring now to FIG. 2, there is shown the suction pile 42,
BOP assembly 18, and wellhead housing 16. The wellhead housing 16
includes a high pressure housing 48 and a low pressure housing 50.
Also shown in FIG. 2 is a suction pile connector 52, which serves
to connect the wellhead housing 16 to the suction pile 42. Although
a single suction pile 42 is shown, multiple suction piles can be
used, with a frame connecting the multiple suction piles. The
suction pile connector 52 of the present technology is advantageous
because it provides a secure way to connect the wellhead housing 16
to the suction pile 42 that is capable of withstanding forces on
the wellhead housing 16, including axial forces, which act on the
connection in the axial direction indicated by arrows F.sub.A, and
bending forces, which act on the connection as indicated by arrow
F.sub.M. Axial forces F.sub.A may be produced, for example, by
tension in the riser 26, which exerts an upward force on the BOP
assembly, and in turn on the wellhead housing 16, as well as the
weight of the casing (not shown) extending from the wellhead
housing 16 downward into the wellbore 14. Bending forces F.sub.M
may be produced, for example, by ocean currents or other
environmental conditions acting on the riser 26, BOP assembly 18,
etc., lateral to the axis of the suction pile 42 and the wellhead
housing 16.
[0026] In some known systems, the wellhead housing 16 has simply
been welded or otherwise fastened to the suction pile 42 using
fasteners, such as bolts. Such connections are often inadequate,
however, for the rigors of the subsea environment. For example,
riser tension and ocean currents can vary over time, thereby
causing cyclical loading of the connection between the wellhead
housing 16 and the suction pile 42 over time. Such cyclical loading
can lead to fatigue in the components, and ultimately to costly
repairs or failure. The suction pile connector 52, on the other
hand, advantageously couples the wellhead housing 16 to the suction
pile 42 in a way that reduces wear caused by axial and bending
forces F.sub.A, F.sub.M on the connection between the wellhead
housing 16 and the suction pile 42.
[0027] An enlarged cross-sectional view of the suction pile
connector 52 is shown in FIG. 3, along with the suction pile 42,
the low pressure housing 50, and the high pressure housing 48. As
shown, the high pressure housing 48 has a bore 54 extending axially
through the high pressure housing 48 parallel to the longitudinal
axis A of the assembly. It is through this bore 54 that the drill
string 28 (shown in FIG. 1) passes as it extends into the wellbore
14. The high pressure housing 48 is circumscribed by the low
pressure housing 50. The high pressure housing 48 and the low
pressure housing 50 may be locked together using a lock ring 56.
Axial movement between the high pressure housing 48 and the low
pressure housing 50 may be further restricted by the geometry of
the housings 48, 50. For example, shoulders 58 of the high pressure
housing 48 may interfere with shoulders 60 of the low pressure
housing 50 to restrict downward axial movement of the high pressure
housing 48 relative to the low pressure housing 50.
[0028] The suction pile connector 52 can be attached to the suction
pile 42 in any appropriate way. For example, as shown in FIG. 3,
the suction pile connector 52 can be attached to the suction pile
42 using fasteners 62. Alternately, the suction pile connector 52
and suction pile 42 can be welded together, or the suction pile
connector 52 can be integrally formed with the suction pile 42. The
suction pile connector 52 extends upwardly from the suction pile 42
toward the wellhead housing 16, and substantially surrounds a
portion of the low pressure housing 50. The geometry of the suction
pile connector 52 relative to the low pressure housing 50, as
described in greater detail below with regard to FIGS. 9 and 10,
can help to resist bending loads. This geometry of the present
technology thus enables a side, or bending load on the wellhead
housing 16 to be transmitted to the suction pile connector 52, from
the suction pile connector 52 to the suction pile 42, and from the
suction pile to the sea floor 44. Thus, wellhead welds 63, surface
casing, and cement in the annulus is prevented from encountering
any side or tension loading, which mitigates or eliminates fatigue
life concerns of the conductor or surface casing welds.
[0029] In certain embodiments, such as the embodiment shown in FIG.
3, the suction pile connector 52 can include one or more recesses
64, and the recesses 64 can each accept a dog connector 66 having
teeth 68 extending inwardly toward the low pressure housing 50. The
teeth 68 of the dog connector 66 can correspond to ridges 70 on the
outer surface of the low pressure housing 50. The dog connector 66
can be moved, either hydraulically (e.g. using hydraulic piston
actuated dogs) or mechanically (e.g., using screw driven dogs),
inwardly toward the low pressure housing 50 until the teeth 68 of
the dog connector 66 engage the ridges 70 of the low pressure
housing 50, thereby locking the low pressure housing 50 relative to
the suction pile connector 52. In such engaged position, the
interface between the teeth 68 of the dog connectors 66 and the
ridges 70 of the low pressure housing 50 can serve to transmit
axial forces between the suction pile 42 and the low pressure
housing 50.
[0030] FIGS. 6-10 depict a step by step process of making up the
connection between the suction pile connector 52 and the low
pressure housing 50, using the dog connections 66, according to one
embodiment of the present technology. These figures also show the
interaction between the suction pile connector 52, the low pressure
housing 50, and the dog connections 66 as forces act on components
of the system.
[0031] In FIG. 4 there is shown the suction pile connector 52, with
the dog connector 66 fully retracted into the recess 64. In this
configuration, there is minimal interference between the teeth 68
of the dog connector 66 and the ridges 70 of the low pressure
housing 50 as the connection is made up. These allows easy
insertion of the low pressure housing into the suction pile
connector 52 when components of the system are assembled, a process
which typically occurs at the surface, prior to lowering the
suction pile/well housing combination to the sea floor. During the
phase of the process shown in FIG. 4, the teeth 68 of the dog
connectors 66 and the ridges 70 of the low pressure housing 50 can
be disengaged, or can be pre-loaded. Although three teeth 68 are
shown in the figures, it is to be understood that more or fewer
teeth could be used in alternate embodiments of the technology.
Also shown in FIG. 4 are the suction pile connector shoulder 78 and
the low pressure housing shoulder 80. The suction pile connector
shoulder 78 and low pressure housing shoulder 80 are arranged
adjacent to one another when the suction pile connector 52 is fully
in place relative to the low pressure housing 50.
[0032] FIG. 5 depicts inward movement of the dog connector 66
toward the low pressure housing 50 as indicated by arrow B. Such
movement of the dog connector 66 can be driven by any appropriate
means. In some embodiments, the dog connector can be controlled by
hydraulics. In others it can be driven mechanically, such as using
an ROV, or the connection can be made at the surface. As the dog
connector 66 moves toward the low pressure housing 50, the teeth 68
of the dog connector 66 engage the ridges 70 of the low pressure
housing 50. As the teeth 68 become engaged with the ridges 70, the
suction pile connector shoulder 78 and low pressure housing
shoulder 80 remain aligned adjacent one another.
[0033] FIG. 6 shows the relative positions of the suction pile
connector 52, low pressure housing 50, and dog connector 66 when an
axial force F.sub.A is applied to the connection. Specifically,
when such an axial force F.sub.A is applied to the low pressure
housing 50, a lower surface 82 of each tooth 68 of the dog
connector 66, contacts or engages an upper surface 84 of each ridge
70 of the low pressure housing 50. This contact restricts movement
of the low pressure housing 50 relative to the suction pile
connector 52, with load being transmitted through the teeth 68 of
the dog connector 66 to the suction pile connecter 52, and not
through the weld on the casing 63 (shown in FIG. 3), casing, casing
hanger or other equipment attached directly or indirectly to the
wellhead housing. In addition, it is to be understood that,
although not shown in the figures, if the axial force were acting
in the opposite direction, the connection would behave in the same
way. That is, the top surface 86 of each tooth 68 of the suction
pile connector 52 would contact the bottom surface 88 of each ridge
70 of the los pressure housing 50, thereby limiting movement of the
suction pile connector 52 relative to the low pressure housing 50
and transmitting the axial force F.sub.A through the teeth 68 of
the dog connector 66.
[0034] FIG. 7 shows the relative positions of the suction pile
connector 52, low pressure housing 50, and dog connector 66 when a
bending force F.sub.M is applied to the connection. The solid line
90 indicates the position of the outer surface of the low pressure
housing 50 before application of the bending force F.sub.M. The
dotted line 92 shows the position of the outer surface of the low
pressure housing 50 after application of the bending force F.sub.M.
Specifically, when such a bending force F.sub.M is applied, the low
pressure housing shoulder 80 rotates upward until it contacts the
suction pile connector shoulder 78, which restricts further
movement of the low pressure housing 50 relative to the suction
pile connector 52. As the low pressure housing shoulder 80 and
suction pile connector shoulder 78 engage, the upper and lower
surfaces 82, 86 of the teeth 68 of the dog connector 66 remain
substantially out of contact with the upper and lower surfaces 84,
88 of the ridges of the low pressure housing 50. Thus, the bending
forces are transmitted substantially through the shoulders 78, 80
of the suction pile connector 52 and low pressure housing 50, and
not through the dog connector 66 or its teeth 68.
[0035] FIG. 8 depicts the relative positions of the suction pile
connector 52, the low pressure housing 50, and the dog connector 66
when an axial force F.sub.A and a bending force F.sub.M are
simultaneously applied. In such a situation, axial force F.sub.A
causes the lower surfaces 82 of the teeth 68 of the dog connector
66 to engage the upper surfaces 84 of the ridges 70 of the low
pressure housing 50, so that the dog connectors bear the axial
load. At the same time, the bending force F.sub.M causes suction
pile connector shoulder 78 to contact the low pressure housing
shoulder 80, so that the bending load is transferred directly
between the suction pile connector 52 and the low pressure housing
50, and not transmitted through the dog connection 66.
[0036] The present technology provides many advantages over known
methods and systems of connecting a wellhead assembly to a suction
pile. For example, by forming load paths as described above, forces
that are directed through the conductors and cement in the wells of
known systems can be redirected to travel instead through the wiser
diameter of the suction pile directly into the sea bed. This way
radial or tensile loading of wellhead welds, surface casing, and
cement in the annulus can be reduced and fatigue life of the
conductor and surface casing welds is improved. The loads of the
suction pile are transmitted from the outer diameter of the suction
pile through to the sea bed. This results in a longer fatigue life
for the wellhead assembly and a longer cement life for the cement
in the annulus between the casings.
[0037] In alternate designs, the suction pile connector can provide
a load path for a portion of the tension loads and a minimal to no
part of the bending loads or side loads; a portion of the bending
or side lads and a minimal to no part of the tension loads; or a
portion of both the tension loads and the bending or side loads.
The portion of loads can be, for example, more than 50% of the
applicable loads applied to the wellhead assembly and in alternate
embodiments can be more than 80% of the applicable loads applied to
the wellhead assembly. The load sharing is dependent on the design
intent and the actual application.
[0038] The suction pile can provide a load path for loads applied
to the wellhead assembly during installation of the wellhead
assembly, such as when the suction pile is used as an installation
tool. The suction pile can alternately provide a load path for
loads applied to the wellhead assembly, and act as a wellhead
assembly foundation and transfer operational loads during operation
of the subsea well. The suction pile can alternately provide a load
path for loads applied to the wellhead assembly both during
installation of the wellhead assembly and during operation of the
subsea well.
[0039] Although the technology herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present technology. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments and that other arrangements may be devised
without departing from the spirit and scope of the present
technology as defined by the appended claims.
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