CN101044294A - Downhole swellable seal - Google Patents

Abstract

A method of operating a wellbore formed in a subterranean formation is disclosed. Said wellbore is provided with a tubular element in which wellbore means are to be arranged such that the wellbore means is in sealing contact with the inner surface of the tubular element, whereby the elongate element will extend through said tubular element in order to perform wellbore operations. The method includes: extending an elongated member through a tubular member, thereby performing said wellbore operations; removing the elongated member from the tubular member; providing an expandable seal on an outer surface of the wellbore device that expands upon contact with a selected fluid , and installing the wellbore device in the tubular member; and causing the expandable seal to expand by contacting the expandable seal with a selection fluid.

Description

Downhole Expandable Seals

technical field

The present invention relates to a method of operating a wellbore formed in a subterranean formation, said wellbore being provided with a tubular element in which a wellbore arrangement is to be arranged such that the wellbore arrangement is in sealing contact with the inner surface of the tubular element, whereby an elongated Elements will extend through said tubular element in order to perform wellbore operations.

Background technique

In producing hydrocarbon fluids from a wellbore, it is common practice that the produced hydrocarbon fluids flow from the pay zone below the wellbore to the surface via conduits known as production tubing. The production tubing may be equipped with one or more devices, such as surface-controlled subsurface safety valves, tubing hangers, landing nipples, packers, and sliding bypass holes. Some of these devices are retrievable and hermetically installed in the tubing string. The tubing string is assembled from a plurality of tubular sections, whereby at each location of the string where the above-mentioned recoverable device is to be installed, one or more seating nipples are incorporated in the string. To ensure that each retrievable unit is deployed at the desired depth in the tubing string, each seating nipple is sized to its respective corresponding retrievable unit. The seal between the retrievable device and the inner surface of the seating nipple is obtained by a suitable sealing element, such as a V-seal. In order to obtain an adequate seal, the portion of the sealing surface where the nipple sits is usually polished, thereby providing a very smooth sealing surface.

Another example of a wellbore device sealably received within a tubular element is a seal assembly of production tubing. The seal assembly is formed from the lower end portion of the production tubing and is received in a polished bore seat (PBR) of a production packer disposed adjacent the pay zone of the wellbore. The seal assembly is axially movable relative to the PBR, thereby allowing for thermal expansion/contraction of the production tubing.

Also, as with production tubing and PBRs, tubular elements are used to transport devices that perform downhole operations. For example, in wireline operations, the downhole unit may be lowered on the wireline through the production tubing or PBR. Such operations involve the movement of a steel wireline (which may be thousands of meters long) through the production tubing or PBR at high speed, whereby the wireline scrapes the polished sealing surfaces. As a result, the sealing surfaces become so damaged that adequate sealing of the device in the tubular element is no longer guaranteed. In many cases, this condition results in severe restrictions on drilling operations and may even compromise the safety of drilling. In the particular case of the sealing surface of a surface controlled subsurface safety valve, damage to the sealing surface may mean that the well needs to be shut down. This condition occurs frequently because the sealing surface of the relief valve seating pup joint is often left unprotected during the drilling input that pulls the relief valve out to allow the largest size tool to be lowered into the well.

Accordingly, there is a need to provide an improved method of wellbore operation which overcomes the above-mentioned deficiencies.

Contents of the invention

According to the present invention there is provided a method of operating a wellbore formed in an earth formation, said wellbore being provided with a tubular element in which a wellbore arrangement is to be arranged such that the wellbore arrangement is in sealing contact with the inner surface of the tubular element, by The elongated member is to be extended through the tubular member to perform wellbore operations, the method comprising:

extending the elongated member through the tubular member to perform said wellbore operation;

removing the elongated element from the tubular element;

providing an expandable seal on the outer surface of the wellbore assembly that expands upon contact with the selected fluid and mounting the wellbore assembly within the tubular member; and

Inflation of the expandable seal is caused by contacting the expandable seal with a selection fluid.

Hereby it is obtained that, by means of an expandable seal which expands upon contact with the selected fluid, said seal expands into irregularities at the sealing surface of the tubular element which is damaged due to wellbore operations through which it is performed.

The invention also relates to a wellbore device for use in a wellbore formed in an earth formation, said wellbore being provided with a tubular element in which the wellbore device is arranged in such a way that the wellbore device is in sealing contact with the inner surface of the tubular element, by This elongated member will extend through said tubular member for performing wellbore operations, the outer surface of said wellbore device being provided with an expandable seal capable of expanding when in contact with a fluid of choice.

In a preferred embodiment, said tubular element is a production tubing, or a portion thereof, such as a landing nipple for a wellbore arrangement, used to transport hydrocarbon fluids produced from the formation to the surface. In such applications, the wellbore device, such as a relief valve assembly, is used to selectively control the flow of hydrocarbon fluid through the production tubing.

Alternatively, the tubular element may be a polished bore block (PBR) and the wellbore device is a sealed assembly of production tubing used to transport hydrocarbon fluids produced from the formation to the surface.

Preferably, the expandable seal expands upon contact with a hydrocarbon fluid and comprises a material selected from the group consisting of natural rubber, nitrile rubber, hydrogenated nitrile rubber, acrylic butadiene rubber, polyacrylate rubber, Butyl rubber, bromobutyl rubber, chlorinated butyl rubber, chlorinated polyethylene, neoprene, styrene-butadiene copolymer rubber, sulfonated polyethylene, ethylene acrylate rubber, epichlorohydrin ring Ethylene oxide copolymer, peroxide crosslinked ethylene-propylene copolymer, sulfur crosslinked ethylene-propylene copolymer, ethylene-propylene-diene terpolymer rubber, ethylene vinyl acetate copolymer, fluororubber, Fluorosilicone rubber and silicone rubber.

The aforementioned materials are suitably selected from the following: EP(D)M rubber (peroxide crosslinked or sulfur crosslinked ethylene-propylene copolymer), EPT rubber (ethylene-propylene-diene terpolymer rubber), butyl Rubber, bromobutyl, chlorinated butyl, and vinyl chloride.

As an alternative or in addition to expandable seals which expand upon contact with hydrocarbon fluids, expandable seals are also adapted to expand upon contact with water and comprise a material selected from the group consisting of: nitrile rubber, hydrogenated nitrile rubber , carboxylated nitrile rubber, fluorinated rubber, perfluororubber, TPE/P rubber or EPDM. In order to improve the swelling properties of the expandable element even in the saline state, the aforementioned material is suitably a matrix material in which a water-soluble compound is incorporated in the matrix material in such a way that the matrix material substantially prevents or limits migration of the compound from the expandable seal And allows water to penetrate into the expandable seal, thereby causing the expandable element to expand when water enters the expandable seal. The compound suitably comprises a salt, for example at least 20% by weight of the salt based on the combined weight of the matrix material and the salt, preferably at least 35% by weight of the salt based on the combined weight of the matrix material and the salt. In order to prevent or reduce leaching of the compound from the matrix material, it is preferred that the matrix material is substantially impermeable to the compound or ions thereof. The compound is present in the matrix material, for example, in the form of a plurality of compound particles dispersed in the matrix material.

Description of drawings

With reference to the accompanying drawings, the present invention will be described in more detail below by way of example, in the accompanying drawings:

Figure 1 schematically shows an embodiment of a wellbore arrangement according to the present invention;

Figure 2 schematically shows a detail A of the wellbore arrangement in Figure 1;

Figure 3 schematically shows a longitudinal section of a tubular element for use in combination with the wellbore arrangement of Figure 1;

FIG. 4 schematically shows the arrangement of the wellbore arrangement of FIG. 1 in the tubular element of FIG. 3 .

In the above drawings, the same reference numerals denote the same components.

Detailed ways

Referring to Fig. 1, there is shown a surface controlled subterranean safety valve assembly 1 (hereinafter referred to as safety valve assembly 1) which selectively controls the flow of fluid in a wellbore (not shown) for producing hydrocarbon fluids. The safety valve assembly 1 comprises a cylindrical conduit 2 having a channel 4 for produced hydrocarbon fluid, the channel 4 being equipped with a valve 6 for selectively closing the channel 4 . The valve 6 is controlled by a hydraulic control system, the hydraulic control pipes 8, 9 and the plunger system 10 of which are only schematically shown here. The hydraulic control pipes 8 , 9 are in fluid communication with the outside of the relief valve assembly 1 through holes 11 provided in the wall of the cylindrical conduit 2 . On the upper part of the safety valve assembly 1 , there is a locking mandrel 12 for supporting and locking the safety valve assembly 1 in the production tubing mentioned below.

Referring further to FIG. 2 , the safety valve assembly 1 is provided with two annular seals 14 , 16 arranged axially spaced apart from each other, whereby the bore 11 is provided between the annular seals 14 , 16 . Each annular seal 14, 16 includes a plurality of V-shaped seals 18, and an expandable seal 20 made of ethylene propylene diene monomer (EPDM) Swelling can occur when hydraulic fluids used in control systems are used.

Referring further to Figure 3, there is shown a tubular element in the form of a seating sub 22 incorporated in production tubing (not shown) for transporting hydrocarbon fluids produced through the wellbore to the surface. The inner diameter of the seating nipple 22 is slightly larger than the outer diameter of the safety valve assembly 1 , thereby allowing axial movement of the safety valve assembly 1 through the seating nipple 22 . The inside of the seating nipple 22 is equipped with a locking face 24 which complements and cooperates with the profile of the locking mandrel 12 , thereby allowing the safety valve assembly 1 to be supported and locked in the seating nipple 22 . Furthermore, the inner surface of the seating sub 22 is provided with two polished annular surface portions 26 , 28 which are slightly smaller in diameter than the remaining inner surface of the seating sub 22 . The polished surface portions 26, 28 are arranged such that the annular seal 14 is opposed to the polished surface portion 26 when the safety valve assembly 1 is locked in the seating nipple 22 by cooperating the locking arbor 12 and the locking surface 24 , while the annular seal 16 is opposed to the polished surface portion 28 .

On the wall of the seating nipple 22 at a location between the polished surface portions 26, 28, there is a bore 30 through which a hydraulic control line 32 extending along the outer surface of the production tubing communicates with a hydraulic control unit ( not shown) in fluid communication. It should be understood that the surface hydraulic control unit, control tube 32 , bore 30 , bore 11 , hydraulic control tubes 8 and 9 , and plunger system 10 described above are all components of a hydraulic control system for controlling valve 6 .

With further reference to Figure 4, during normal use, the relief valve assembly 1 is disposed in a seating nipple 22 of production tubing. Hydrocarbon fluids are extracted from the formation surrounding the wellbore and transported to the surface through production tubing. Thus, the produced hydrocarbon fluid flows through the passage 4 of the safety valve assembly 1 . If it is necessary to shut down the well (such as in the event of an emergency), valve 6 is caused to close under the control of the hydraulic control system operated at the surface. Leakage of hydrocarbon fluids along the outside of the safety valve assembly 1 is avoided due to the annular seals 14 , 16 which seal the polished surface portions 26 , 28 of the production tubing 22 .

After a period of continuous production of hydrocarbon fluids from the wellbore, it may be necessary to shut down the wellbore and remove the safety valve assembly 1 from the production tubing in order to perform downhole maintenance operations using wireline (not shown) extending from the surface through the production tubing. During maintenance operations of this type, the wireline is moved at high speed through the production tubing, and thus through the seating sub 22 . The wire rope would thereby scrape the protruding polished surface portions 26 , 28 of the seating nipple 22 . As a result, the polished surface portions 26, 28 tend to become damaged so that after the safety valve assembly 1 is reinstalled into the seating nipple 22, the V-seals 18 of the annular seals 14, 16 no longer adequately seal against these surface portions. sealed. However, the sealing function of the annular seals 14, 16 is still ensured due to the expandable seal 20, which expands by means of contact with the hydraulic oil present in the annular chamber, which is controlled by the safety The outer surface of the valve assembly 1 , the inner surface of the seating nipple 22 and the annular seals 14 , 16 are defined. In this way, the seal 20 extends after expansion into the irregularities formed at the damaged surface portions 26 , 28 and thereby adequately seals the safety valve assembly 1 against the seating sub 22 .

It should be understood that the present invention is not limited to applications where the tubular member is a production tubing or a portion thereof (eg, a landing sub). Other beneficial applications include, for example, tubing hangers, packers, polished hole seats, and slip bypass holes.

Claims (18)

1. A method of operating a wellbore formed in an earth formation, said wellbore being provided with a tubular element in which wellbore means are arranged such that the wellbore means is in sealing contact with the inner surface of the tubular element, whereby the elongated element Extending through the tubular element to perform wellbore operations, the method comprising: extending the elongated member through the tubular member to perform the wellbore operation; removing the elongate element from the tubular element; providing an expandable seal on an outer surface of the wellbore assembly that expands upon contact with a selected fluid, and mounting the wellbore assembly within the tubular member; and Expansion of the expandable seal is caused by contacting the expandable seal with the selection fluid. 2. The method of claim 1, wherein the tubular element is a production tubing for transporting hydrocarbon fluids produced from the formation to the surface. 3. The method of claim 2, wherein said tubular member includes a seating nipple for receiving said wellbore device, and said step of installing said wellbore device in said tubular member comprises installing said wellbore device in The seat is placed in a pup joint. 4. The method of claim 3, wherein the wellbore device is a relief valve assembly for selectively controlling the flow of hydrocarbon fluid through the production tubing. 5. The method of claim 1, wherein the tubular element is a polished bore seat and the wellbore device is a sealed assembly of production tubing for transporting hydrocarbon fluids produced from the formation to the surface . 6. The method of any one of claims 1-5, wherein the selection fluid is a hydrocarbon fluid and the expandable seal comprises a material selected from the group consisting of natural rubber, nitrile rubber, hydrogenated Nitrile Rubber, Acrylic Butadiene Rubber, Polyacrylate Rubber, Butyl Rubber, Bromobutyl Rubber, Chlorinated Butyl Rubber, Chlorinated Polyethylene, Neoprene Rubber, Styrene-Butadiene Copolymer Rubber, Sulfonated polyethylene, ethylene acrylate rubber, epichlorohydrin ethylene oxide copolymer, peroxide crosslinked ethylene-propylene copolymer, sulfur crosslinked ethylene-propylene copolymer, ethylene-propylene-diene triene Meta-copolymer rubber, ethylene vinyl acetate copolymer, fluororubber, fluorosilicone rubber, and silicone rubber. 7. The method of claim 6, wherein the material is selected from the group consisting of EP(D)M rubber (peroxide crosslinked or sulfur crosslinked ethylene-propylene copolymer), EPT rubber (ethylene-propylene- Diene terpolymer rubber), butyl rubber, bromobutyl rubber, chlorinated butyl rubber, and vinyl chloride. 8. The method of any one of claims 1-5, wherein the selection fluid is water and the expandable seal comprises a material selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile Rubber, fluorinated rubber, perfluororubber, TPE/P rubber or EPDM rubber. 9. The method of claim 8, wherein the material is a matrix material, and wherein the water-soluble compound is incorporated in the matrix material in a manner that the matrix material substantially prevents or limits the compound from moving away from the inflatable seal and Water is allowed to penetrate into the expandable seal, thereby causing the expandable element to expand when water enters the expandable seal. 10. The method of claim 9, wherein the compound comprises a salt. 11. The method of claim 10, wherein the expandable seal comprises at least 20% by weight of the salt based on the total weight of the matrix material and salt, preferably at least 35% by weight salt. 12. The method of any one of claims 9-11, wherein the matrix material is substantially impermeable to the compound or ions thereof. 13. The method of any one of claims 9-12, wherein the compound is present in the matrix material in the form of a plurality of compound particles dispersed in the matrix material. 14. The method of any one of claims 1-5, wherein the selected fluid is hydraulic oil, and the wellbore device is controlled by a hydraulic control system that communicates with the inflatable seal A stream of said hydraulic oil in contact is manipulated, and wherein the step of causing expansion of the expandable element comprises supplying a stream of hydraulic oil to said hydraulic control system. 15. A wellbore device for use in a wellbore formed in a subterranean formation, said wellbore being provided with a tubular element in which the wellbore device is arranged in such a manner that the wellbore device is in sealing contact with the inner surface of the tubular element, whereby fine An elongated element will extend through said tubular element for wellbore operations, and the outer surface of said wellbore device is provided with an expandable seal capable of expanding upon contact with a fluid of choice. 16. The wellbore arrangement of claim 15, wherein the wellbore arrangement is disposed in the tubular element, the inner surface of which is damaged as a result of performing a wellbore operation in which the elongate element extends through the tubular element, and wherein the expandable element expands upon contact with the selection fluid, thereby sealing the wellbore device to the inner surface of the tubular element. 17. A method substantially as hereinbefore described with reference to the accompanying drawings. 18. A wellbore arrangement substantially as hereinbefore described with reference to the accompanying drawings.

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