GB2578806A

GB2578806A - Assembly for controlling flow of fluid from a completed well and method of making such an assembly

Info

Publication number: GB2578806A
Application number: GB1909629.6A
Authority: GB
Inventors: Spitz Stuart
Original assignee: Aker Solutions AS
Current assignee: Aker Solutions AS
Priority date: 2019-07-04
Filing date: 2019-07-04
Publication date: 2020-05-27
Also published as: GB201909629D0

Abstract

An assembly for controlling reservoir fluid from a completed well comprising a main body and main flow passage 20, 24, lined with a thermally insulating liner 30, 32. The liner may have a lower thermal conductivity than that of the main body and be made of a polymer, ceramic or glass. The liner may be in the form of a tube or coating and have sealing elements. The main passage may be a Christmas tree 10, tubing hanger 16 or production tubing 17. There is a further claim for a method of making such an assembly.

Description

Assembly for Controlling Flow of Fluid from a Completed Well and Method of Making such an Assembly The present invention relates to an assembly such as a Christmas tree for controlling flow of fluid from a completed oil or gas well.

Flow of oil and / or gas from a well is controlled, in part, using a metallic assembly of valves, spools and fittings known as a Christmas tree. The Christmas tree is mounted on top of the wellhead or a completed well, and whilst its primary function is to control flow into or out of the well, it also has many other functions including providing ports for the injection of chemicals into the well (chemical injection ports), pressure relief valves for relieving pressure in the well, and connections to sensors for monitoring conditions in the well such as pressure, temperature, flow rate, fluid composition etc. It also provides valves which are operable to shut-in the well in the event of an emergency.

The Christmas tree has a main passage a first end of which is connected to the 15 production tubing, and a second end of which is connected to the production flowline, so that well fluid flows from the production tubing along the main passage of the Christmas tree to the production flowline. The production tubing is suspended from a tubing hanger which may be mounted in the well head as is typical in a vertical Christmas tree, or in the main passage of the Christmas tree, as is known in horizontal Christmas trees.

It is an object of the invention to provide an alternative configuration of assembly for controlling flow of fluid from a well.

According to a first aspect of the invention we provide an assembly for controlling flow of reservoir fluid from a completed well, comprising a main body which surrounds a main passage, the main passage having a first end which is adapted to be connected to the well and a second end which is adapted to be connected to a production flowline, wherein the assembly is further provided with a thermally insulating liner which lines at least a portion of the main passage to prevent direct contact between fluid flowing along the main passage and the main body in that portion of the main passage.

In use, the well fluid entering the main passage of the assembly can be at a relatively high temperature, and can heat up the assembly to such an extent that the hydraulic, electrical and fibre-optic equipment associated with the valves and sensors mentioned above have to be rated to operate at a temperature at or close to well-flowing temperature. This can be challenging, particularly in relation to electrical and fibre-optical couplers between the Christmas tree and tubing hanger. By virtue of providing one or more portions of the main passage with a thermally insulating liner, the temperatures to which thermally sensitive electrical, fibre-optical or hydraulic components in the assembly are exposed may be reduced.

The liner may be made from a material which has a lower thermal conductivity than the material from which the main body of the assembly is made.

The liner may be made from a polymer, a ceramic, a glass, or a combination thereof.

The liner may comprise a tube having an outer surface which is adjacent to or engages with the main body of the assembly, and a radial inner surface which surrounds a central passage along which fluid from well flows. In this case, the assembly may further be provided with seals which extend between the outer surface of the liner and the main body at a first end and a second end of the liner so as to substantially prevent flow of fluid between the outer surface of the liner and the main body of the assembly. The tube may have a generally circular transverse cross-section.

The liner may alternatively comprise a thermally insulating coating applied to at least a portion of the main body of the assembly around the main passage.

The assembly may be provided with two or more non-metallic insulating liners which are each located in different portions of the main passage to prevent direct contact between fluid flowing along the main passage and the main body the portion of the main passage in which the liner is located. In this case, each of the liners may have any of the features listed above.

The assembly may comprise a Christmas tree. The assembly may comprise a tubing hanger.

The assembly may comprise production tubing suspended from a tubing hanger. The main passage may be provided in a Christmas tree. The main passage may be provided in a tubing hanger.

The main passage may be provided in a production tubing suspended from a tubing hanger.

According to a second aspect of the invention we provide a method of thermally insulating an assembly for controlling flow of reservoir fluid from a completed well, the assembly comprising a main body which surrounds a main passage, the main passage having a first end which is adapted to be connected to the well and a second end which is adapted to be connected to a production flowline, wherein the method includes lining at least a portion of the main passage with a thermally insulating liner to prevent direct contact between fluid flowing along the main passage and the main body in that portion of the main passage.

The liner may be made from a material which has a lower thermal conductivity than 15 the material from which the main body of the assembly is made.

The liner may be made from a polymer, a ceramic, a glass or a combination thereof.

The liner may, for example, be made from polyether ether ketone (PEEK) or from PTFE.

The method may comprise the steps of inserting a tubular liner into the main passage, the tubular liner having an outer surface which is adjacent to or engages with the main body of the assembly, and a radially inner surface which surrounds a central passage along which fluid from well flows. In this case, the method may further include mounting seals between the outer surface of the liner and the main body at a first end and a second end of the liner so as to substantially prevent flow of fluid between the outer surface of the liner and the main body of the assembly.

The method may include coating the insulating liner onto at least a portion of the main body of the assembly around the main passage. In this case, the method may comprise spraying a coating made from a ceramic, polymer, glass or combination thereof onto a portion of the main body around the main passage.

The assembly may comprise a Christmas tree.

The assembly may comprise a tubing hanger.

The assembly may comprise production tubing suspended from a tubing hanger.

The main passage may be provided in a Christmas tree.

The main passage may be provided in a tubing hanger.

Embodiments of the invention will now be described, by way of example only, and with reference to the attached figures which,shows a schematic illustration of a cross-section through an assembly according to the first aspect of the invention.

Referring now to the figure, there is shown a Christmas tree 10 mounted on a wellhead 12. The wellhead 12 has a main passage 14, and a tubing hanger 16 is mounted in the main passage 14 at the upper end of the wellhead 12. Production tubing 17 is suspended from the tubing hanger 16 and extends down into a wellbore (not shown) on which the wellhead 12 is provided. The tubing hanger 16 has a main body 18 which encloses a main passage 20 which provides a conduit for flow of fluid from the well head 12 to the Christmas tree 10.

The Christmas tree 10 has a main body 22 which is secured at its lowermost end to the well head 12, and which encloses a main passage 24, a first end which is connected to the main passage 20 in the tubing hanger 16, and a second end which is connected to a production flowline 26. In this embodiment, the Christmas tree is vertical horizontal Christmas tree, and the main passage 24 comprises a first portion 24a which extends from its first end generally parallel to the production tubing 17, and a second portion 24b which extends through the main body 22 generally perpendicular to the first portion 24a to its second end. The invention could equally be applied to a horizontal Christmas tree in which the tubing hanger 16 is located within the Christmas tree 10 rather than within the well head 12 In this embodiment, the first end of the main passage 24 in the Christmas tree 10 is formed from a separate tube 40, a first end of which extends into the main passage 20 of the tubing hanger 16. Seals 38a, 38b, 38c are provided between the radially outward facing surface of the tube 40 and the main body 18 of the tubing hanger 16 so that fluid from the main passage 20 in the tubing hanger 18 flows along the passage 42 enclosed by the tube 40. The second end of the tube 40 engages with the main body 22 of the Christmas tree 10, and seals 36a, 36b, 36c are provided between the radially outward facing surface of the tube 40 and the main body 22 of the Christmas tree 10. In this embodiment, the two sets of seals each comprise a metallic lip seal 36a,38a backed up by non-metallic seals 36b, 36c, 38b, 38c.

Whilst in this embodiment, the tube 40 is a separate part to the main body 22 of the Christmas tree 10, this need not be the case, and it is, for all other purposes 15 considered to be part of the main body 22 Thermally insulating liners 30, 32 are provided to line at least a portion of the main passage 20, 24 the tubing hanger 16 and the Christmas tree 10, to prevent direct contact between fluid flowing along the main passage 20, 24 and the main body 18, 22 in that portion of the main passage 20, 24.

In this embodiment, the liner 32 in the main passage 24 of the Christmas tree 10 is provided in both the first 24a and second 24b portions of the main passage 24, and lines the radially inward facing surface of the tube 40, in addition to the part of the first portion 24a of the main passage 24 just above the tube 40 and below the second portion 24b of the main passage 24.. In this embodiment, a thermally insulating liner 34 is also provided to line the radially inwardly facing surface of the upper end of the production tubing 17.

Also in this embodiment of the invention, the end of the production flowline 26 adjacent the Christmas tree 10 is provided with a thermally insulating liner 38.

It should be appreciated, however, that it is not necessary to provide a liner in all of these locations. A liner could equally be provided in only one or any of these locations. For example, a liner 30, 32, 34 might only be provided in the main passage 20 of the tubing hanger 16, only in the main passage 24 of the Christmas tree 10, or only in the production tubing 17. Where the liner 32 is only provided in the main passage 24 of the Christmas tree 10, it need not be provided in all the locations illustrated in the figure -it could be provided in only one or these locations or in any number and combination of these locations.

The liner 30, 32, 34 is made from a material which has a lower thermal conductivity than the material from which the main body 18, 22 of the tubing hanger 16 or Christmas tree 10, or the production tubing 17 is made. These components are typically metallic -normally some sort of steel or a superalloy such as Inconel, and the liner 30, 32, 34 is preferably made from a polymer, a ceramic, or a glass, or a combination of any of these.

The liner 30, 32, 34 may comprise a tube having an outer surface which is adjacent to or engages with the main body 18, 22 of the tubing hanger 16 or Christmas tree 10 (which includes the tube 40), or the interior surface of the production tubing 17, and a radially inner surface which surrounds a central passage along which fluid from well flows. The shape of the transverse cross-section of the tube corresponds to the shape of the main passage 20, 24 or the production tubing 17, and therefore will, in most cases be generally circular.

Where the liner 30, 32, 34 is a tube, there may be seals which extend between the outer surface of the liner 30, 32, 34 and the main body 18, 22 or production tubing 17 at a first end and a second end of the liner 30, 32, 34, so as to substantially prevent flow of fluid between the outer surface of the liner 30,32, 34 and the main body 18, 22 or the production tubing 17.

The liner may, for example, be made from polyether ether ketone (PEEK) or PTFE.

In alternative embodiments of the invention, the liner 32, 34 comprises a coating applied to at least a portion of the main body 18, 22, or production tubing 17.

The coating may be a ceramic, glass or combination material such as alumina or mullite, or it may be a polymer such as polytetrafluorethylene (PTFE), or a mixture of 30 polymers such as Xylan® or a combination of one of any of these materials.

The coating may be applied using the conventional deposition techniques for the material concerned. It may be painted or sprayed on, perhaps using a thermal spraying technique such as high-velocity oxy-fuel spraying, or may be applied by a technical deposition process such as physical or chemical vapour deposition.

Alternatively, the liner may be formed by treating the surface of the main body 18, 22 around the main passage 20, 24, or the interior face of the production tubing 17 to form a layer which has a different chemical composition, and lower thermal conductivity, than the original material.

By virtue of its low thermal conductivity, the liner 30, 32 34 may reduce transfer of heat from the well fluid to the tubing hanger 16, Christmas tree 10, or production tubing 17. Such heat transfer is undesirable for two reasons. First, it may expose electrical, fibre-optic or hydraulic components in the Christmas tree 10 or tubing hanger 16 to temperatures they are not designed to tolerate, and as such, may cause these components to malfunction or be irreparably damaged or said high-temperature exposure may result in limited life due to thermal degradation of materials. By positioning the liner 30, 32 in regions of the main passage 20, 24 which are close to thermally sensitive electrical, fibre-optic or hydraulic components contained by or embedded in the main body 18, 22, the temperatures to which those components are exposed may be reduced.

Second, if the temperature of well fluid drops too much as a result of heat transfer to the tubing hanger 16, Christmas tree 10 or production tubing 17, this may cause problems in relation to the processability of the well fluid. For example, flow of the well fluid along the production flowline 26 may be compromised by the increasing viscosity of the well fluid as it cools, or, where the well fluid is or contains natural gas, the temperature drop may cause condensation of water vapour in the gas, and the formation of hydrates, which could choke or block the main passages 20, 24 or production flowline 26. The liner 30, 32, 34 may reduce the need to provide external insulation on the Christmas tree 10 or production flowline 26 to maintain the well fluid in a desired temperature range.

Claims

Claims 1. An assembly for controlling flow of reservoir fluid from a completed well, comprising a main body which surrounds a main passage, the main passage having a first end which is adapted to be connected to the well and a second end which is adapted to be connected to a production flowline, wherein the assembly is further provided with a thermally insulating liner which lines at least a portion of the main passage to prevent direct contact between fluid flowing along the main passage and the main body in that portion of the main passage.
2. An assembly according to claim 1 wherein the liner is made from a material which has a lower thermal conductivity than the material from which the main body of the assembly is made.
3. An assembly according to claim 1 or 3 wherein the liner is made from a polymer, a ceramic, a glass, or a combination thereof.
4. An assembly according to any preceding claim wherein the liner comprises a tube having an outer surface which is adjacent to or engages with a main body of the assembly, and a radially inner surface which surrounds a central passage along which fluid from well flows.
5. An assembly according to claim 4 further comprising seals which extend between the outer surface of the liner and the main body at a first end and a second end of the liner so as to substantially prevent flow of fluid between the outer surface of the liner and the main body of the assembly.
6. An assembly according to any one of claims 1 to 3 wherein the liner comprises a coating applied to at least a portion of a main body of the assembly around the main passage.
7 An assembly according to any preceding claim wherein the assembly is provided with two or more thermally insulating liners which are each located in different portions of the main passage to prevent direct contact between fluid flowing along the main passage and the main body the portion of the main passage in which the liner is located.
8. An assembly according to any preceding claim wherein the assembly comprises a Christmas tree.
9. An assembly according to any preceding claim wherein the assembly comprises a tubing hanger.
10.An assembly according to any preceding claim wherein the assembly comprises production tubing suspended from a tubing hanger.
11. An assembly according to any preceding claim wherein the main passage is provided in a Christmas tree.
12.An assembly according to any preceding claim wherein the main passage is provided in a tubing hanger.
13.An assembly according to any preceding claim wherein the main passage is provided in a production tubing suspended from a tubing hanger.
14.A method of making an assembly for controlling flow of reservoir fluid from a completed well, the assembly comprising a main body which surrounds a main passage, the main passage having a first end which is adapted to be connected to the well and a second end which is adapted to be connected to a production flowline, wherein the method includes lining at least a portion of the main passage with a thermally insulating liner to prevent direct contact between fluid flowing along the main passage and the main body in that portion of the main passage.
15.A method according to claim 14 wherein the liner is made from a material which has a lower thermal conductivity than the material from which the main body of the assembly is made.
16.A method according to claim 14 or 15 wherein the liner is made from a polymer, a ceramic, a glass, or a combination of polymer and ceramic.
17.A method according to any one of claims 14 to 16 wherein the method comprises the step of inserting a tubular liner into the main passage, the tubular liner having an outer surface which is adjacent to or engages with the main body of the assembly, and a radially inward facing surface which surrounds a central passage along which fluid from well flows.
18.A method according to claim 17 further including mounting seals between the outer surface of the liner and the main body at a first end and a second end of the liner so as to substantially prevent flow of fluid between the outer surface of the liner and the main body of the assembly.
19.A method according to any one of claims 14 to 16, the method including coating the insulating liner onto at least a portion of the main body of the assembly around the main passage.
20.A method according to any one of claims 14 to 19 wherein the assembly comprises a Christmas tree.
21.A method according to any one of claims 14 to 20 wherein the assembly comprises a tubing hanger.
22.A method according to any one of claims 14 to 21 wherein the assembly comprises production tubing suspended from a tubing hanger.
23.A method according to any one of claims 14 to 22 wherein the main passage is provided in a Christmas tree.
24.A method according to any one of claims 14 to 23 wherein the main passage is provided in a tubing hanger.
25.A method according to any one of claims 14 to 24 wherein the main passage is provided in production tubing suspended from a tubing hanger.