GB2486256A

GB2486256A - Downhole sealing device

Info

Publication number: GB2486256A
Application number: GB201020896A
Authority: GB
Inventors: David Glen Martin
Original assignee: Caledyne Ltd
Current assignee: Caledyne Ltd
Priority date: 2010-12-09
Filing date: 2010-12-09
Publication date: 2012-06-13
Anticipated expiration: 2030-12-09
Also published as: GB201020896D0; GB2486256B

Abstract

The invention relates to a downhole tool for use with an electric submersible pump or other downhole devices requiring conduits running downhole from the surface along the external surface of a drill string. The downhole tool comprises a substantially cylindrical member having upper and lower connections (10A, B figure 3) for connecting within an axial downhole string; an intermediate portion 4 configured to allow a seal 5 to be selectively formed at the annulus defined by the intermediate portion and the well bore. The cylindrical member has a channel for receiving a conduit which runs axially along the external surface of the downhole string such that the conduit does not interfere with the seal when formed at the annulus. The channel may be internal to the cylindrical member at the intermediate portion. The cylindrical member may be axially split to form two axial portions which when connected form the cylindrical member.

Description

1 Sealing device for ESP completions 3 This invention relates to an apparatus for use with 4 electric submersible pump (ESP) completions or other downhole devices requiring conduits running downhole from 6 the surface in the oil and gas extraction industry.

B ESP5 are used for artificial lift applications in the oil 9 and gas extraction industry. An electrically driven pump is used to pump oil from the wellbore, when the bottom 11 hole pressure is not sufficient to allow the oil to flow 12 freely. Generally, the ESP is installed within the 13 wellbore on a tubing string, termed the production string 14 at a depth sufficient for the pump intake to be near the oil production zone.

17 Conventionally, The ESP motor is powered via a cable, 18 strapped to the outside of the tubing string which runs 19 from the surface to the ESP within the wellhore. This cable may be circular or rectangular in shape.

21 Additionally, there may also be discrete cables or 22 hydraulic lines run in parallel with the ESP power cable, 23 also strapped to the tubing string. These cables may also 1 be combined with the ESP power cables within an 2 encapsulation or wound metal jacket.

4 When the ESP tubing string, consisting of the ESP mounted in the tubing string, and the said power cable is 6 installed within the wellbore, it is customary to use a 7 blowout preventer (BOP) BOP5 are standard commercially 8 available equipment. If a safety issue arises when 9 installing or removing the ESP, the BOP is closed, forming a seal on the outside of the tubing string. To 11 allow the BOP rams to close onto the circular cross- 12 section of the tubing, the ESP cable has to be cut. This 13 is of particular concern as the cable then needs to be 14 either rejoined in situ, with possible electrical integrity issues, or the entire string removed from the 16 wellbore and the cable replaced.

18 This scenario may also occur when work patterns dictate 19 that installation or removal is suspended, or when weather prohibits further work.

22 The current state of the art is to sever the ESP cable to 23 allow use of a BOP to seal on the outside of the tubing 24 string to provide well control.

2 The invention discloses apparatus for which allows 3 standard BOP5 to be used to seal on the outside of the 4 tubing string, but does not reguire the ESP cable to be severed.

7 According to a first aspect of the invention there is 8 provided a downholLe tool comprising: 9 a substantially cylindrical member having upper and lower connections for connecting within an axial downhole 11 string; 12 an intermediate portion configured to allow a seal 13 to be selectively formed at the annulus defined by the 14 intermediate portion and the well bore, wherein the cylindrical member defines a channel for 16 receiving a conduit which runs axially along the external 17 surface of the downhole string such that the conduit does 18 not interfere with the seal when formed at the annulus.

The cylindrical member may define the intermediate 21 portion. The intermediate portion may comprise a waist 22 portion of the cylindrical member. The seal may comprise 23 a blowout preventer seal.

1 The conduit may be an electrical cable. The conduit may 2 be an electrical cable for an ESP.

4 The channel may be internal to the cylindrical member at the intermediate portion. The intermediate portion may 6 define a circular section for sealing at the intermediate 7 portion.

9 The depth of the channel within the cylindrical member may increase from the upper connection to the 11 intermediate portion. The depth of the channel within 12 the cylindrical member may increase from the lower 13 connection to the intermediate portion.

The cylindrical member may be axially split. The 16 cylindrical member may comprise two axial portions which 17 are connectable to form the cylindrical member. Each 18 portion may include co-operating mating members for 19 connecting the two portions. This allows insertion of the conduit prior to connecting the two portions.

22 The cylindrical member may define one or more recesses or 23 pockets at the channel. A plurality of recesses may be 1 provided along the channel, the recesses being axially 2 spaced apart.

4 The apparatus may include one or more housing members for housing the conduit. The or each housing member may be 6 axially split to allow insertion of the conduit.

8 The housing member may be configured to provide a housing 9 seal between the conduit and the housing. The housing member may include one or more compression seals. The 11 apparatus may be adapted such that connecting of the two 12 portions causes compression of the compression seals.

14 In an alternative embodiment, the housing member may be fillable with a sealing material, such as grease. The 16 apparatus may define one or more injection paths for the 17 sealing material.

19 A plurality of housing members may be provided, each for a particular axial section of the conduit. The or each 21 housing member may be receivable in the or each recess.

22 Each recess may be configured to prevent axial movement 23 of the housing member. A plurality of housing members 1 provides multiple seals along the channel but does not 2 require that the whole length of the channel be sealed.

4 The cylindrical member may define an axial fluid channel which allows fluid flow in either direction between the 6 upper and lower connections.

8 The invention may therefore comprise a special tubing 9 joint, which has a cavity into which is laid the ESP cable. The cavity is covered by a housing, which returns 11 the cross section to a circle, which is sealed upon by 12 the BOP ram. Within the cavity are sealing means which 13 prevent fluid bypass to maintain integrity of the tubing 14 joint as if it were a plain pipe.

16 Within the special tubing joint may be an axial fluid 17 channel which allows fluid to be transferred from either 18 end without affecting the ESP cable cavity. Fluid or qas 19 pressure may then be transmitted up or down hole throuqh the joint.

22 The sealing means may be either compression seals which 23 conform to the outside of the ESP cable or a grease 24 injection system, where heavy qrease is injected into the 1 small cavities between the outside of the ESP cable and 2 the inside of "flow tubes". The flow tube inside profile 3 approximates to the outside of the ESP cable, with 4 manufacturing clearances. Grease injection systems are commonly used with "slickline" sealing systems and are a 6 well understood method of sealing.

8 A particular embodiment of the invention will now be 9 described, by way of example only, with reference to the accompanying drawings in which: 12 Figure 1 shows a general arrangement of the joint, where 13 the ESP cable 3, is contained within the joint 1 and seal 14 housing 2.

16 Figure 2 shows the position of the BOP seals 5, which 17 seal on the cylindrical waist 4, formed by the mandrel 1 18 and housing 2.

Figure 3 shows a general view of the joint 1, showing a 21 plurality of pockets 6A for containing sealing means.

22 Also identified are fixing points 7A for the housing 2, 23 pockets 8 to allow ESP cable 3 bypass, a grease injection 1 path 9, upper connection 1OA and lower connection lOB to 2 attach the joint to the tubing string.

4 Figure 4 shows a general view of the housing 2, where fixing points 7B mate with the corresponding points 7A on 6 the joint 1. Pockets 6B correspond to pockets 6A on the 7 joint 1 to contain sealing means.

9 Figure 5 shows a general view of a housing member in the form of a rubber sealing device 11. Preferably a rubber 11 extrusion, the interior profile 12 matches the outside 12 profile of the FSP cable. A scarf cut 13 allows the 13 sealing device to be wrapped around the ESP cable before 14 being placed within the pockets 6. Affixing the housing 2 compresses the rubber sealing device 11. This forms a 16 seal against the ESP cable.

18 Figure 6 shows general view of an alternate housing 19 member in the form of a flow tube device 14. Preferably metal, the interior profile 12 matches the outside 21 profile of the ESP cable. A slot 153 allows the sealing 22 device to be fitted around the ESP cable before being 23 placed within the pockets 6. The grease injection path 1 pumps the grease to the pockets 6, where the grease fills 2 the voids between the flow tube and ESP cable.

4 Maintaining pressure and injecting grease within the tool prevents well fluids migrating through the device, under 6 the IBOP ram seals.

8 It can be seen to those skilled in the art that various 9 changes may be made to the features within this embodiment, without departing from the scope of the 11 invention.

Claims

Claims 1. A downhole tool comprising: a substantially cylindrical member having upper and lower connections for connecting within an axial downhole string; an intermediate portion configured to allow a seal to be selectively formed at the annulus defined by the intermediate portion and the well bore, wherein the cylindrical member defines a channel for receiving a conduit which runs axially along the external surface of the downhole string such that the conduit does not interfere with the seal when formed at the annulus.
2. A downhole tool as claimed in claim 1, wherein the cylindrical member defines the intermediate portion.
3. A downhole tool as claimed in claim 2, wherein the intermediate portion comprises a waist portion of the cylindrical member. r
4. A downhole tool as claimed in any preceding claim, wherein the seal comprises a blowout preventer seal.o
5. A downhole tool as claimed in any preceding claim, wherein the conduit comprises an electrical cable for an ESF.
6. A downhole tool as claimed in any preceding claim, wherein the channel is internal to the cylindrical member at the intermediate portion.
7. A downhole tool as claimed in any preceding claim, wherein the intermediate portion defines a circular section for sealing at the intermediate portion.
8. A downhole tool as claimed in any preceding claim, wherein the depth of the channel within the cylindrical member increases from the upper connection to the intermediate portion.
9. A downhole tool as claimed in any preceding claim, wherein the depth of the channel within the cylindrical member increases from the lower connection to the intermediate portion.
10. A downhole tool as claimed in any preceding claim, wherein the cylindrical member is axially split, and wherein the cylindrical member comprises two axial portions which are connectable to form the cylindrical member.
11. A downhole tool as claimed in claim 10, wherein each portion includes co-operating mating members for connecting the two portions.
12. A downhole tool as claimed in any preceding claim, wherein the cylindrical member defines one or more recesses or pockets at the channel.
13. A downhole tool as claimed in claim 12, wherein a plurality of recesses are provided along the channel, the recesses being axially spaced apart.
14. A downhole tool as claimed in any preceding claim, including one or more housing members for housing the conduit. r15. A downhole tool as claimed in claim 14, wherein the or each housing member is axially split to allow insertion of the conduit.o 16. A downhole tool as claimed in claim 14 or 15, wherein the housing member is configured to provide a housing seal between the conduit and the housing.17. A downhole tool as claimed in claim 16, wherein the housing member includes one or more compression seals, and wherein the apparatus is adapted such that connecting of the two portions causes compression of the compression seals.18. A downhole tool as claimed in claim 16, wherein the housing member is fillable with a sealing material.19. A downhole tool as claimed in claim 18, wherein the apparatus defines one or more injection paths for the sealing material.20. A downhole tool as claimed in any of claims 14 to 19, wherein a plurality of housing members are provided, each for a particular axial section of the conduit.21. A downhole tool as claimed in claim 20, wherein each housing member is receivable in a recess.22. A downhole tool as claimed in claim 21, wherein each recess is configured to prevent axial movement of the housing member.23. A downhole tool as claimed in any preceding claim, wherein the cylindrical member defines an axial fluid channel which allows fluid flow in either direction between the upper and lower connections.24. A downhole tool as claimed in claim 5, including a tubing joint having a cavity for receiving the ESP cable. r c\J Co