EP3178902A1

EP3178902A1 - Downhole completion system

Info

Publication number: EP3178902A1
Application number: EP15199294.8A
Authority: EP
Inventors: Christian Krüger
Original assignee: Welltec AS
Current assignee: Welltec AS
Priority date: 2015-12-10
Filing date: 2015-12-10
Publication date: 2017-06-14

Abstract

The present invention relates to a downhole completion system arranged in a borehole of a well for producing hydrocarbon-containing fluid from a reservoir, comprising a well tubular metal structure forming a conduit for conducting fluid, the well tubular structure having an inner face and an outer face, and at least one metal component mounted as part of the well tubular metal structure and having an inner component face, wherein the inner component face is at least partly covered by an ion diffusion barrier.

Description

Field of the invention

The present invention relates to a downhole completion system arranged in a borehole of a well for producing hydrocarbon-containing fluid from a reservoir.

Background art

Precipitation of scale or debris on the metal surfaces downhole is due to a chemical reaction with the surface and occurs when certain chemical elements are present in the conduit at the same time, and in the event of the occurrence of a change in pressure and/or temperature or a change in the composition of a solution.
Scale forming on the inner face of a completion component is especially undesirable as the function of the component is compromised by such formation of scale. Therefore scale inhibitors are added to many wells, but they do not seem to solve the problem, as scale is still precipitated on the completion components and causes the function of the component to fail.

Summary of the invention

It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved downhole completion system in which scale does not easily precipitate, especially on the surfaces of completion components.
The above objects, together with numerous other objects, advantages and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole completion system arranged in a borehole of a well for producing hydrocarbon-containing fluid from a reservoir, comprising:

a well tubular metal structure forming a conduit for conducting fluid, the well tubular structure having an inner face and an outer face, and
at least one metal component mounted as part of the well tubular metal structure and having an inner component face,

The ion diffusion barrier may comprise an electric insulator.
Moreover, the ion diffusion barrier may comprise a layer of the electric insulator.
Further, the ion diffusion barrier may comprise ceramics or glass.
Also, the ion diffusion barrier may comprise Polytetrafluoroethylene (PTFE), fibre glass, silicon, diamond-like carbon, polymer, such as epoxy or phenolic polymers, or graphene.
Additionally, the metal component may comprise a recess or a circumferential groove.
Furthermore, the metal component may comprise a movable part, the movable part comprising the recess or the groove being at least partly covered by the ion diffusion barrier.
Moreover, the recess or the cirdumferential groove of the movable part may have an inclining end face, so that turbulence of the fluid around the recess or groove is minimised.
The metal component may be a sliding sleeve and/or a valve.
In addition, the metal component may be a nipple or a no-go.
Also, the inner face may be at least partly covered by the ion diffusion barrier.
Further, the well tubular metal structure may comprise a recess or a groove being at least partly covered by the ion diffusion barrier.
The downhole completion system as described above may further comprise a tool having a projecting part configured to engage the recess or the groove of the metal component.
Moreover, the metal component may be a tool permanently installed in the well tubular metal structure.
Additionally, the well tubular metal structure may have an opening covered by the ion diffusion barrier.
Also, the outer face of the well tubular metal structure may be at least partly covered by the ion diffusion barrier.
The downhole completion system as described above may further comprise at least one annular barrier, each annular barrier comprising:

a tubular metal part, the tubular metal part being mounted as part of the first well tubular metal structure,
an expandable tubular surrounding the tubular metal part, each end section of the expandable tubular being connected with the tubular metal part,
an annular barrier space between the tubular metal part and the expandable tubular, and
an expansion opening in the tubular metal part through which pressurised fluid passes in order to expand the expandable tubular and bring the annular barrier from an unexpanded position to an expanded position.

Moreover, the expandable tubular may be made of metal.
The ion diffusion barrier may have a thickness of 10^-6-3 mm.

Brief description of the drawings

The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which

Fig. 1 shows a partly cross-sectional view of a downhole completion system,
Fig. 2 shows a cross-sectional view of an inner face of the well tubular metal structure covered by an ion diffusion barrier, and
Fig. 3 shows a cross-sectional view of a metal component partly covered by an ion diffusion barrier.

All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.

Detailed description of the invention

Fig. 1 shows a downhole completion system 100 arranged in a borehole 2 of a well 3 for producing hydrocarbon-containing fluid from a reservoir 4. The downhole completion system comprises a well tubular metal structure 5 forming a conduit 6 for conducting the fluid. The well tubular structure has an inner face 7 forming the conduit and an outer face 8 facing the annulus or cement arranged in the borehole. The downhole completion system further comprises a metal component 10 mounted as part of the well tubular metal structure and having an inner component face 11 forming part of the inner face of the well tubular metal structure. The inner component face is at least partly covered by an ion diffusion barrier 12, so that metal ions from the well tubular metal structure are prevented from diffusing into the hydrocarbon-containing fluid in the conduit.
Formation of scale or debris on the metal surfaces downhole occurs when certain chemical elements are present in the conduit at the same time. Tests have shown that such build-up of scale is more likely in areas in the well tubular metal structure where turbulence occurs than in other areas. Furthermore, tests have also shown that scale precipitates more easily on metal surfaces, and since completion components are made of metal and cause more turbulence, it is important to reduce the scale precipitation thereon by other means. By covering the surfaces opposite the most turbulent areas with an ion diffusion barrier, the scale precipitation in these areas has shown to decrease substantially, which is due to the fact that the metal ions diffusing from the metal component or metal casing are prevented from entering the fluid in the conduit. This is especially useful when the completion component is a metal component and has a movable part or a groove into which a tool is to engage, since the scale often prevents the movable part from moving or fills up the groove, so the tool cannot engage the groove. By covering the inner component face with the ion diffusion barrier, scale is not formed to the same extent as on other faces in the well tubular metal structure, and the function of the metal component is not compromised. Scale will then precipitate on the other surfaces not covered by the ion diffusion barrier, but this is more acceptable since scale in these areas does not adversely affect the function of the well. If the scale precipitation becomes too excessive, a cleaning operation is then initiated during which the scale is mechanically removed.
In order to prevent the metal ions from diffusing, the ion diffusion barrier comprises an electric insulator 23. As shown in Fig. 2, the ion diffusion barrier comprises a layer 22 of the electric insulator 23 closest to the inner face or outer face of the well tubular metal structure. The second layer of the ion diffusion barrier may be a material providing a smoother surface or a layer protecting the ion diffusion barrier. The ion diffusion barrier comprises ceramics or glass for providing the electric insulator 23, and since fragments are more easily broken off such material than off e.g. polymers, a protective polymer layer may be arranged outside the electric insulator. Thus, the ion diffusion barrier may also comprise Polytetrafluoroethylene (PTFE), fibre glass, silicon, diamond-like carbon, polymer, such as epoxy or phenolic polymers, or graphene.
In Fig. 3, the metal component comprises a recess 14 which is a circumferential groove 15. The metal component comprises a movable part 16 sliding in the recess 14, and the movable part also comprises a recess 14B in the form of a circumferential groove 15B which is covered by the ion diffusion barrier. As can be seen, the inner component face 11 and thus part of the inner face facing the inside of the conduit are covered by the ion diffusion barrier so as to prevent scale from precipitating on the inner component face and thus hindering movement of the movable part 16. If scale was allowed to build up in the recess 14, the movable part could not move and close off the opening 18.
Furthermore, the opening 18 in the well tubular metal structure is also covered by the ion diffusion barrier in order to prevent scale from precipitating on the inner face 25 of the opening. In this way, closure or at least choking of the opening caused by such precipitation on the inner face of the opening is prevented. Part of the outer face 8 of the well tubular metal structure surrounding the opening 18 is furthermore partly covered by the ion diffusion barrier.
In Fig. 3, the recess 14B or the cirdumferential groove 15B of the movable part 16 has an inclining end face 17, so that turbulence of the hydrocarbon-containing fluid around the recess or groove is minimised. The movable part is thus the movable part of a sliding sleeving sliding in a recess in the well tubular metal structure, and by having the movable part arranged slidably in the recess instead of inside the well tubular metal structure, the fluid is more easily led past the metal component 10. By having inclined end faces, the fluid is also easily led past the movable part without causing significant turbulence as compared to grooves having end faces perpendicular to the longitudinal extension of the well tubular metal structure.
A wall of the well tubular metal structure may have an opening 18 in which a valve, such as an inflow control valve, is arranged. The valve may have inner faces covered by ion diffusion barrier hindering the forming of scale inside the valve and thus preventing the valve from functioning as intended. The metal component may be a nipple or a no-go having profiles in which tools or the like are to dock. These profiles may also be covered by the ion diffusion barrier to prevent the formation of scale and thus prevent that the tools cannot dock into the profiles.
As mentioned, the inner face may be partly covered by the ion diffusion barrier and the scale will thus form and precipitate in the parts not coverd by the ion diffusion barrier, which is more acceptable as the scale does not adversely affect the function of the well in these areas.
The well tubular metal structure of Fig. 2 comprises a recess 14C which is a helical groove 15C at least partly covered by the ion diffusion barrier. Such helical groove is often used to align and/or orientate a tool inside the well tubular metal structure, e.g. to shift a gas lift valve. As shown the groove is also covered by the ion diffusion barrier, so that the scale does not precipitate in the groove and hinder the function of the groove which is to guide the tool in place.
The downhole completion system shown in Fig. 1 further comprises a tool 20 having two projecting parts 21 configured to engage the recess or the groove of the metal component, such as a sliding sleeve, to pull the sleeve from an open position to a closed position, or vice versa. The tool may be a metal component which is permanently installed in the well tubular metal structure and having its faces at least partly covered by the ion diffusion barrier especially in and around the functional areas.
In Fig. 1, the downhole completion system further comprises two annular barriers 30 providing zonal isolation of a first zone from a second zone, where the second zone is a production zone and an opening 18 is arranged opposite the second zone in order to allow the fluid to flow into the well tubular metal structure when the metal component is in its open position. Each annular barrier comprises a tubular metal part 31 being mounted as part of the first well tubular metal structure, an expandable tubular 32 surrounding the tubular metal part, where each end section 33, 34 of the expandable tubular is connected with the tubular metal part, creating an annular barrier space 35 between the tubular metal part and the expandable tubular. An expansion opening 36 is arranged in the tubular metal part through which pressurised fluid passes in order to expand the expandable tubular and bring the annular barrier from an unexpanded position to an expanded position.
The ion diffusion barrier has a thickness which is 10^-6-3 mm so that the ion diffusion barrier does not substantially minimise the inner diameter of the well tubular metal structure of the metal component.
By fluid or well fluid is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By gas is meant any kind of gas composition present in a well, completion, or open hole, and by oil is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc. Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively.
By a casing, production casing or a well tubular metal structure is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production.
In the event that the tool is not submergible all the way into the casing, a downhole tractor 50 can be used to push the tool all the way into position in the well. The downhole tractor may have projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.
Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.

Claims

A downhole completion system (100) arranged in a borehole (2) of a well (3) for producing hydrocarbon-containing fluid from a reservoir (4), comprising:
- a well tubular metal structure (5) forming a conduit (6) for conducting fluid, the well tubular structure having an inner face (7) and an outer face (8), and

- at least one metal component (10) mounted as part of the well tubular metal structure and having an inner component face (11),
wherein the inner component face is at least partly covered by an ion diffusion barrier (12).
A downhole completion system according to claim 1, wherein the ion diffusion barrier comprises an electric insulator (23).
A downhole completion system according to claim 1 or 2, wherein the ion diffusion barrier comprises a layer (22) of the electric insulator.
A downhole completion system according to any of the preceding claims, wherein the ion diffusion barrier comprises ceramics or glass.
A downhole completion system according to any of the preceding claims, wherein the metal component comprises a recess (14) or a circumferential groove (15).
A downhole completion system according to claim 5, wherein the metal component comprises a movable part (16), the movable part comprising the recess (14B) or the groove (15B) being at least partly covered by the ion diffusion barrier.
A downhole completion system according to claim 5 or 6, wherein the recess or the cirdumferential groove of the movable part has an inclining end face (17), so that turbulence of the fluid around the recess or groove is minimised.
A downhole completion system according to any of the preceding claims, wherein the metal component is a sliding sleeve and/or a valve.
A downhole completion system according to any of the preceding claims, wherein the inner face is at least partly covered by the ion diffusion barrier.
A downhole completion system according to any of the preceding claims, wherein the well tubular metal structure comprises a recess (14C) or a groove (15C) being at least partly covered by the ion diffusion barrier.
A downhole completion system according to any of the preceding claims, further comprising a tool (20) having a projecting part (21) configured to engage the recess or the groove of the metal component.
A downhole completion system according to any of the preceding claims, wherein the metal component is a tool (20B) permanently installed in the well tubular metal structure.
A downhole completion system according to any of the preceding claims, wherein the well tubular metal structure has an opening (18) covered by the ion diffusion barrier.
A downhole completion system according to any of the preceding claims, wherein the outer face of the well tubular metal structure is at least partly covered by the ion diffusion barrier.
A downhole completion system according to any of the preceding claims, further comprising at least one annular barrier (30), each annular barrier comprising:
- a tubular metal part (31), the tubular metal part being mounted as part of the first well tubular metal structure,

- an expandable tubular (32) surrounding the tubular metal part, each end section (33, 34) of the expandable tubular being connected with the tubular metal part,

- an annular barrier space (35) between the tubular metal part and the expandable tubular, and

- an expansion opening (36) in the tubular metal part through which pressurised fluid passes in order to expand the expandable tubular and bring the annular barrier from an unexpanded position to an expanded position.