INSTALLATION ASSEMBLY FOR A SUBSEA WELLHEAD
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.
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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.
BACKGROUNDField of Invention
This invention relates in general to equipment used in the hydrocarbon industry, and in particular, to systems and methods for subsea drilling operations.
Description of the Prior Art
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.
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.
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.
SUMMARYOne 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.
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.
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.
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:
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.
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.
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
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.
Referring now to
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 FA, FM on the connection between the wellhead housing 16 and the suction pile 42.
An enlarged cross-sectional view of the suction pile connector 52 is shown in
The suction pile connector 52 can be attached to the suction pile 42 in any appropriate way. For example, as shown in
In certain embodiments, such as the embodiment shown in
In
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.
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.
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.
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.
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.
Type: Application
Filed: Nov 4, 2016
Publication Date: May 11, 2017
Applicant: Vetco Gray, Inc. (Houston, TX)
Inventors: Samved Bhatnagar (Houston, TX), Jonathan Clark (Houston, TX), Robert K. Voss (Houston, TX)
Application Number: 15/344,204