Subsea universal Xmas tree hang-off adapter

Abstract

Adapter (15) for an oil or gas field Christmas tree (4), said adapter (15) comprising a first interface (16) to connect the adapter (15) to a corresponding Christmas tree interface (17) on the top of the Christmas tree (4), distinctive in that the adapter (15) further comprises a second interface (18), at least one feed-through, and at least one of: a well barrier element, an internal profile for setting a plug, a hanger or a combined hanger and plug.

Claims

1. An adapter for an oil or gas field Christmas tree, said adapter comprising: a first interface to connect the adapter to a corresponding Christmas tree interface on a top of the Christmas tree; a second interface; at least one feed-through configured to convey electric power; at least one of: a well barrier element, an internal profile for setting a plug, or a combined hanger and plug; wherein said second interface is identical to the Christmas tree interface, and said second interface is at an end of the adapter opposite of said first interface; and wherein the adapter comprises a string hanging down from a lower well barrier within the adapter, through the Christmas tree, and into a production tubing.

2. The adapter according to claim 1, wherein the at least one feed through, arranged lateral or axial, connects an inside of the adapter to an outside of the adapter, and the well barrier element is a well barrier compliant valve or plug, or a combination thereof.

3. The adapter according to claim 1, wherein the feed-through is configured to convey at least one of: electric communication, optical communication, hydraulic liquid, and gas, in any combination.

4. The adapter according to claim 1, wherein said string encloses lines, cables and tubes, said string being suspended from the lower well barrier within the adapter, wherein the lower well barrier is the well barrier element, the combined hanger and plug or the plug within said Christmas tree or said adapter.

5. The adapter according to claim 1, wherein said feed-through extends laterally through a sidewall of said adapter.

6. The adapter according to claim 1, wherein said feed-through extends vertically through a cap on top of said adapter.

7. The adapter according to claim 1, wherein said feed-through is arranged below said well barrier element.

8. The adapter according to claim 1, wherein the adapter comprises two well barriers and said feed-through is arranged between said two well barriers.

9. The adapter according to claim 1, wherein the first interface comprises a Christmas tree connector either adapted to interface with a tubing hanger of the Christmas tree, for connecting to horizontal Christmas trees, or with an inside of a Christmas tree spool, for connecting to vertical Christmas trees.

10. The adapter according to claim 1, wherein the adapter is a high-pressure unit capable of withstanding well pressure.

11. The adapter according to claim 1, wherein the second interface is an H4 profile.

12. An oil or gas field Christmas tree having an adapter, the adapter comprising: a first interface connected to a Christmas tree interface on a top of the Christmas tree and a second interface identical to the Christmas tree interface arranged at an end of the adapter opposite of said first interface; the adapter further comprising at least one feed-through configured to convey electric power to a pump unit via a cable; the pump unit being suspended into a production tubing from a hanger within the adapter via a string, wherein the string comprises the cable and extends from the hanger, through the Christmas tree, and into the production tubing; and the adapter comprising a plug arranged in a through-channel of the adapter, the plug arranged to form a pressure barrier in the through-channel.

13. The oil or gas field Christmas tree adapter according to claim 12, wherein the hanger and the plug are a combined hanger and plug arranged in the through-channel.

14. The oil or gas field Christmas tree adapter according to claim 12, wherein the plug is a first plug forming a first pressure barrier, and the adapter comprises a second plug arranged in the through-channel, the second plug arranged to form a second pressure barrier in the through-channel.

15. The oil or gas field Christmas tree adapter according to claim 14, wherein the hanger and the second plug are a combined hanger and plug arranged in the through-channel.

16. The oil or gas field Christmas tree adapter according to claim 12, wherein the hanger is arranged in the through-channel.

17. The oil or gas field Christmas tree adapter according to claim 12, wherein said feed-through extends laterally through a side wall of said adapter.

18. The oil or gas field Christmas tree adapter according to claim 12, wherein said feed-through extends vertically through a cap on top of said adapter.

19. The oil or gas field Christmas tree adapter according to claim 12, wherein: the first interface comprises a Christmas tree connector; the Christmas tree is a horizontal Christmas tree and the connector interfaces with a tubing hanger of the Christmas tree.

20. The oil or gas field Christmas tree adapter according to claim 12, wherein: the first interface comprises a Christmas tree connector; the Christmas tree is a vertical Christmas tree and the connector interfaces with an inside of a spool of the Christmas tree.

Description

FIGURES

(1) FIG. 1 is an overview of an adaptor of the invention,

(2) FIG. 2 illustrates an adaptor of the invention installed on a horizontal Xmas tree,

(3) FIG. 3 illustrates an adaptor of the invention installed on a vertical Xmas tree,

(4) FIG. 4 illustrates horizontal feed-through in an adaptor of the invention,

(5) FIG. 5 illustrates vertical feed-through in an adaptor of the invention, and

(6) FIG. 6 illustrates an adaptor of the invention installed on a hybrid Xmas tree.

(7) FIGS. 7 and 8 illustrate prior art embodiments related to installation of ESPs,

(8) FIG. 9 shows a principle arrangement according to the invention,

(9) FIG. 10 shows an adapter according to the invention,

(10) FIG. 11 shows a docking station that can be used together with the invention,

(11) FIG. 12 shows the situation in the well when a docking station has been replaced by a new docking station, and

(12) FIG. 13 shows an alternative embodiment of an arrangement incorporating the adaptor of the present invention.

DETAILED DESCRIPTION

(13) In the following, the same reference number has been used for items that have the same function, even though the item may not be identical throughout the various embodiments.

(14) FIG. 1 illustrates an example of a SUTHA, i.e. an adaptor 15, of the invention. Two plugs 31a and 31b in the design replace the two crown plugs in the XT 4 to maintain sufficient well integrity during production. The plugs have been set in a respective plug profile 31c and 31d formed in the bore of the adaptor 15. The figure also illustrates how the lower plug 31b is designed with necessary electrical, hydraulic, optical fiber or gas feed-through 19 to connect with the string or tubing below. Wet-mate connectors are mated to the signal, power and service lines between the plugs 31a, 31b to allow for horizontal access (similar to hybrid penetration at XT 4). Feed-through 19 can also be done vertically through the top of the hub 50. In that case, both plugs 31a, 31b will have vertical feed through capability. A high pressure debris cap 51 is installed on top of the adaptor 15. Between the XT hub 4 and the adaptor 15 is a XT connector 52 that interfaces the feed through to provide a conduit for the power and communication lines, or gas injection.

(15) FIGS. 2 and 3 below illustrate how the SUTHA adaptor 15 can be installed on both a horizontal (HXT) and vertical (VXT) x-mas trees 4. On the HXT 4 the SUTHA adaptor 15 has an inner profile 54 that interfaces with the Tubing Hanger 53 while on the VXT 4 the inner profile 55 interfaces with the inside of the XT spool 56.

(16) FIGS. 4 and 5 illustrate horizontal and vertical feed-throughs 19, respectively, in adaptors 15 of the invention. As seen in FIG. 5, the vertical feed-through 19 is brought through a high pressure debris cap 51 on top of the adaptor 15. Inside the adaptor 15, the feed-through 19 is typically connected to a hanger connector 31, which is connected with power and communication to instrumentation and equipment in the well.

(17) FIG. 6 illustrates an adaptor 15 of the invention installed on a hybrid Xmas tree.

(18) FIG. 7 shows the principles of the known internal cabling method. The figure shows a well casing 1 that extends into the ground from a wellhead 2 arranged at the seabed 3. On top of the wellhead 2 is a Christmas tree 4. A production tubing 5 extends from the Christmas tree into the well on the inside of the casing. A pump unit 6 (sometimes called ESP) is situated within the production tubing. The Pump unit 6 is suspended from a coiled tubing 7. A signal and power cable 8 is situated within the coiled tubing 7. The coiled tubing is suspended from a hanger plug 9, which has been landed inside the Christmas tree 4. The cable 8 extends through a tree cap 10, and then up to the sea surface (not shown). The tree 4 is a horizontal Christmas tree. It is theoretically feasible, but highly unpractical to use this technique on a vertical Christmas tree due to the smaller production bore size of the vertical Christmas trees.

(19) The major disadvantage of this method of suspending the pump unit 6 is the challenge met during installation of the system and the difficulties in replacing the ESP when it fails. In addition, it requires the use of coiled tubing for installation because of its greater tensile capacity compared to wireline. The weight of the complete system (mainly due to the heavy coiled tubing) also gives limitations to the installation depth. The installation is very difficult to perform on live wells, as the system is dependent on the closing of downhole valves to close the well below the location of the ESP. This makes the system less robust, and the options for contingency operations are limited. The replacement of the pump unit 6 is complex and costly. The reliability of downhole valves for closing the well below the pump unit is questionable, and if the downhole valve should fail, contingency is lost and an expensive operation is necessary to replace the valve.

(20) External Cabling:

(21) FIG. 8 shows a second alternative in established prior art. The well casing 1, wellhead 2, Christmas tree 4 and production tubing 5 are the same as in FIG. 1. In the external cabling method, the pump unit has been landed on a docking station 11. The docking station has been installed together with the production tubing and includes a penetration through the production tubing with a wet mate connection 12 for connecting the power and signal cable 8 to the ESP.

(22) The cable 8 is routed on the outside of the production tubing 5, i.e. in the annulus between the production tubing 5 and the casing 1. It extends through a penetration 13 in the wellhead 2 and through a penetration 14 in the Christmas tree 4. Systems of this type are described in US20100707843 and US20100835578.

(23) The penetration through the production tubing requires that the external cabling option infrastructure must be installed with the production tubing. As the completion must be specially made for the purpose, it requires changing the completion (inter alia the production tubing) if it is to be retrofitted on existing wells. This makes this method very costly to install in brownfield wells. The Christmas tree must also be replaced, as most trees do not have the required feed-through for a power and signal cable. If the docking station or cable is damaged and ceases to function, the whole completion must also be changed.

(24) FIG. 9 shows several of the same elements as in FIGS. 1 and 2. The same reference numbers have been retained for elements that are substantially similar, such as the casing 1, the wellhead 2, the seabed 3, the Christmas tree 4, the production tubing 5, the pump unit 6 and the power and signal cable 8.

(25) The pump unit is landed in a docking station 11, which is similar to the docking station 11 of FIG. 2, but does not include a penetration of the production tubing 5. The docking station 11 may nevertheless be installed together with the production tubing. Alternatively, it may be installed at a later stage by securing it to the inside surface of the production tubing, as will be generally known to the person of skill.

(26) The docking station includes a wet mate connector (see FIG. 5) and the cable 8 is connected to the docking station 11, via a weak link 30, at the inside of the production tubing 5. The cable 8 extends along the production tubing 5 on the inside of the production tubing 5 from the docking station 11 through the wellhead 2 and through the Christmas tree 4.

(27) At the top of the Christmas tree is connected an adapter 15. This adapter is shown in further detail in FIG. 4. The adapter 15 has a lower first interface 16, which is adapted to mate with a corresponding interface 17 on the top of the Christmas tree 4. At the top of the adapter 15 is an upper second interface 18, which is identical to the interface 17 on top of the Christmas tree 4.

(28) The adapter 15 has a feed-through 19 for the power and signal cable 8, which goes through the adapter and onwards to the surface or alternatively connects with a wet mate connector on the outside of the adapter 15. The feed through of the cable 8 is in the lower part of the adapter 15 in order to reduce the height of the adapter 15 as much as possible.

(29) In addition, the adapter 15 has internal plug profiles 20 and 21. Thereby the adapter 15 serves two purposes: 1. to provide a feed-through for the cable 8 and 2. to provide the Christmas tree with plug profiles. The plug profiles, which can be for one, two or more plugs, to plug the bore of the tree and thereby shutting in the well. Thereby, the adapter can serve to provide a tree 4 with additional plug profiles or replace a damaged plug profile within the tree. If one plug profile is provided, the adapter must be for high pressure to maintain two barriers, otherwise a debris cap on the top of the adapter is sufficient. The upper interface 18 of the adapter 15 is preferably of a standard profile, such as a H4 hub, to allow a workover riser system to be connected on top of the adapter 15.

(30) The adapter 15 can also be used for other applications, such as when extra power and/or signals are needed in the well, and when it is considered beneficial to install the equipment inside the production tubing to avoid having to change the completion. Such functions could be smart well functionality, such as closing and opening parts of the reservoir to produce more oil/gas and less water, extra valves for well control, monitoring systems, etc.

(31) FIG. 10 shows the docking station 11 in more detailed. It comprises a docking sleeve 22 and a set of seal elements 23, 24, which serves to lock the sleeve 22 against the inner surface of the production tubing 5, and to seal the annulus between the sleeve 22 and the production tubing 5. The sleeve 22 comprises an ESP landing shoulder 25, which is adapted to receive the pump unit 6. It also comprises plug profiles 26, 27 that are adapted to receive a plug (not shown). The possibility of landing a plug in the docking station 11 will be described further below.

(32) The docking station also comprises a wet mate connector 28, which is in this embodiment is connected to a short cable length 29 and a weak link 30. The weak link is in turn connected to the power and signal cable 8. Alternatively, the weak link 30 may be on the docking station 11, as shown in FIG. 3.

(33) An important feature of the docking station 11 design is that it does not rely on features within the completion tubing for it to be secured within the production tubing. Therefore, the docking station can be secured and sealed to the production tubing by, for example, packers. The seal can either be permanent or be releasable by control signals through the cable 8, or through other mechanical or chemical means, as known per se. The pump unit will be landed on the landing shoulder 25 and connected to the cable 8 through the wet mate connector 28.

(34) FIG. 11 shows a situation in which a docking station 11 has been rendered dysfunctional. This may be because the wet mate connector 28 is faulty, because of damage to the ESP landing shoulder, or other flaws that result in the docking of the pump unit and connection thereof to the cable 8 no longer can be performed. In such a situation, the pump unit (not shown in FIG. 6) will be recovered and a plug (not shown) may be landed and secured to the plug profiles 26, 27 in the docking station 11 so that the flow through the docking station is blocked. The plug may be of a type that dissolves through prolonged contact with the well flow or due to an excess pressure on one side of the plug, e.g. plugs made of glass. Such plugs are well known in the art.

(35) Before or after the plug has been set in the docking station, a pull is exerted on the cable 8 (see FIG. 5). The pull breaks the weak link 30, so that only the short cable length 29 remains. Then the cable 8 may be pulled out of the well for re-use or replacement.

(36) When the flow through the docking station has been blocked, a new docking station 11 may be run into the production tubing 5 and secured to the inner surface of the production tubing 5. This docking station 11 may be identical to the faulty docking station 11, but may also be of an improved type. The cable that was recovered from the well, or alternatively a new cable, is connected to the new docking station 11 prior to its insertion into the well. The pump unit that was recovered from the first docking station 11 may be (if it has not been damaged) landed on the new docking station 11 and coupled to the cable 8 through the wet mate connector 28. Thereafter the plug that has been set in the first docking station 11 will be removed by well-known means. As soon as the plug has been removed, the operation of the ESP may resume.

(37) As described above, if a new docking station is to be installed, the old one can be left in the well. The cable 8 can then be released and reused (if not damaged) by performing the described over-pull on the cable 8 to break the weak link 30. Since the old docking station has plug profiles 26, 27 to enable easy plugging of the well at the correct location, this allows for retrieving of the cable 8 on a closed well.

(38) The power and signal cable 8 (also termed ESP cable) may comprise power lines, signal lines and hydraulic lines. According to the invention, the cable 8 can be routed from the adapter 15 or tree cap in several different ways. However, it should be ensured that the cable runs close to the inner wall of the production tubing. This provides better space for running the pump unit into and out of the well, as well as other types of equipment. The cable 8 will also be less subject to forces from the well flow.

(39) FIG. 13 describes an embodiment of the present invention, which utilizes the adapter 15 described above in combination with a pump unit 6 suspended on a length of coiled tubing 7 from a hanger plug 31. This embodiment can be beneficial for cases where it is difficult to get the correct hanger plug profile to fit the existing profiles in the Christmas tree 4. The adapter 15 will provide the desired internal profile for a plug 9, from which the coiled tubing is suspended. The cable 8 may be going out through a tree cap 10 on top of the adapter 15 or be fed through the side of the adapter 15, as described in connection with the embodiment in FIGS. 3 and 4. The embodiment of FIG. 7 may also be beneficial over prior art for contingency operations, since an open water workover system can land on the standard, e.g., H4, hub profile and gain well control before the hanger plug is removed.

(40) A possible first time installation of the arrangement of the present invention may be as follows:

(41) 1. Plug the well using glass, step, or dissolvable plugs.

(42) 2. Circulate the well above the plugs with MEG (or similar types of fluids) using, e.g., coiled tubing.

(43) 3. Land the adapter on the Christmas tree, with the cable and the docking station attached.

(44) 4. Secure the docking station to the production tubing using, e.g., packers or other means that acts against a slick tubing surface.

(45) 5. Land a workover system (open water or riserless system) on top of the adapter.

(46) 6. Install the pump unit by landing it in the docking station.

(47) 7. Plug the adapter and install a debris cap, or a high-pressure tree cap.

(48) 8. Break the plugs, e.g., glass plugs, by pressurising through the Christmas tree. Alternatively, let the plugs dissolve by contact with the well flow, or use explosives to dissolve the plugs.

(49) When the pump unit needs to be replaced, the following procedure can be used:

(50) 1. Install a workover system on top of the adapter (either an open water or a riserless system).

(51) 2. Remove the plugs in the adapter.

(52) 3. Remove the pump unit using a wireline (preferably, the pump can be retrieved in several parts to enable conventional wireline to be used and to reduce the required lubricator length).

(53) 4. Install a new pump unit (preferably in several parts).

(54) 5. Set plugs in the adapter and install a debris cap or a high-pressure cap.

(55) If the docking station, cable or adapter should fail, the following procedure can be used:

(56) 1. Install workover system on top of the adapter (either open water or riserless system)

(57) 2. Remove plugs in the adapter

(58) 3. Remove the pump unit using wireline (preferably, the pump can be retrieved in several parts to enable conventional wireline to be used and to reduce the required lubricator length).

(59) 4. Set glass or dissolvable plugs in the docking station to close the well.

(60) 5. Circulate the well by, e.g., MEG.

(61) 6. Retrieve the adapter with a running tool, performing over-pull to release the cable at the weak link close to the docking station.

(62) 7. Perform the same operation as described for first time installation.

(63) The adaptor of the invention may include any feature or step herein described or illustrated, in any operative combination, each such combination is an embodiment of the invention.

(64) The method of the invention may include any feature or step herein described or illustrated, in any operative combination, each such combination is an embodiment of the invention.