Apparatus and Method for Detection of Corrosion

Abstract

An apparatus is for detecting corrosion in an internal pipe bore in a pipeline. A tracer chamber containing a first tracer is formed in a portion of the pipeline and is bounded towards the internal pipe bore by a chamber wall having a first corrosion resistance and including at least one wall portion with a second corrosion resistance, the second corrosion resistance being smaller than the first corrosion resistance. A method is for detecting corrosion in an internal pipe bore in a pipeline.

Claims

1. An apparatus for detecting corrosion in an internal pipe bore in a pipeline, the apparatus comprising a tracer chamber containing a first tracer and being formed in a portion of the pipeline and bounded towards the internal pipe bore by a chamber wall having a first corrosion resistance and further comprising at least one wall portion with a second corrosion resistance, the second corrosion resistance being smaller than the first corrosion resistance, wherein said first tracer is arranged in porous polymer rods.

2. The apparatus according to claim 1, wherein the reduced corrosion resistance of the at least one wall portion is provided by said wall portion having a wall thickness smaller than the general wall thickness of the chamber wall.

3. The apparatus according to claim 1, wherein the reduced corrosion resistance of the at least one wall portion is provided by the use of a material with less corrosion resistance than the material forming the remaining part of the chamber wall.

4. The apparatus according to claim 1, wherein the reduced corrosion resistance of the at least one wall portion is provided by structural means such as tensioning said wall portion against adjacent chamber-wall elements in order thereby to increase the material stress in said wall portion.

5. The apparatus according to claim 1, wherein the tracer chamber is annular and surrounds the periphery of the internal pipe bore.

6. An apparatus assembly comprising: a tracer chamber containing a first tracer and being formed in a portion of the pipeline and bounded towards the internal pipe bore by a chamber wall having a first corrosion resistance and further comprising at least one wall portion with a second corrosion resistance, the second corrosion resistance being smaller than the first corrosion resistance, wherein said first tracer is arranged in porous polymer rods; wherein a sacrificial anode which is arranged to be placed in the pipe bore includes a second chamber which is filled with a second tracer.

7. An apparatus assembly comprising: a tracer chamber containing a first tracer and being formed in a portion of the pipeline and bounded towards the internal pipe bore by a chamber wall having a first corrosion resistance and further comprising at least one wall portion with a second corrosion resistance, the second corrosion resistance being smaller than the first corrosion resistance, wherein said first tracer is arranged in porous polymer rods; wherein the apparatus assembly includes one or more further apparatuses selected from the group consisting of a scale-control apparatus, a scale-detection apparatus and an inhibitor-detection apparatus.

8. A method for detecting corrosion in an internal pipe bore in a pipeline, the method comprising: a) arranging a first tracer in porous polymer rods in a first chamber separated from the pipe bore by a chamber wall having a first corrosion resistance; b) forming at least one chamber-wall portion with a second corrosion resistance which is smaller than the first corrosion resistance; c) bringing the chamber wall and the at least one chamber-wall portion into contact with a corrosive fluid flow; d) by corrosion, perforating the at least one chamber-wall portion with reduced corrosion resistance; e) dissolving the first tracer in the fluid flow; and f) detecting the first tracer in the fluid flow by means of a tracer detector placed downstream, as an indication of the pipe bore corroding.

9. The method according to claim 8, further comprising: g) arranging a second tracer in a chamber in a sacrificial anode; h) placing the sacrificial anode upstream of the first tracer chamber; i) releasing a corrosion-inhibiting sacrificial material from the sacrificial anode into the fluid flow and depositing the sacrificial material in the pipe bore downstream of the sacrificial anode; j) releasing the second tracer into the fluid flow in consequence of the sacrificial material having been substantially consumed from the sacrificial anode; and k) detecting the second tracer in the fluid flow by means of a tracer detector placed downstream, as an indication of the sacrificial anode having been substantially consumed and corrosion of the pipe bore being expectable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In what follows, an example of a preferred embodiment is described, which is visualized in the accompanying drawings in which:

[0036] FIG. 1 shows an axial section through a portion of a pipeline provided with a pipe section including an annular tracer chamber in which, in an internal tracer-chamber wall, wall portions having less corrosion resistance than the rest of the internal tracer-chamber wall are indicated;

[0037] FIG. 2 shows an axial section, on a larger scale, through an annular sacrificial anode, that is to say a sacrificial material that inhibits corrosion on adjacent structures by its galvanic effect, a second tracer being enclosed in a second chamber in the sacrificial anode; and

[0038] FIG. 3 shows an axial section, on a smaller scale, through a larger portion of the pipeline including pipe sections provided with apparatus for scale control and detection, an apparatus for detecting return flow of previously injected inhibitors, and an apparatus according to the invention for detecting corrosion.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] In the figures, the reference numeral 1 indicates a pipeline to be monitored. Even though the figures substantially relate to a well pipe, the invention may also relate to other types of pipelines, for example pipelines for conveying fluids on land and at sea, characterized by being pipelines that are subjected to internal corrosion which is difficult to detect because of the pipeline being difficult to access because of the surroundings, the distance to a personnel base, or the fact that great challenges are involved in stopping the fluid flow through the pipeline for an internal, visual check to be carried out.

[0040] The pipeline 1 is connected to a control room 7 where appropriate systems 71 are installed for the operation and control of the pipeline 1 and a fluid flow 12 in an internal pipe bore 11 in the pipeline 1.

[0041] In a portion of the pipeline 1 where it is desirable to monitor the development of corrosion in the pipe bore 11, a corrosion-detection apparatus 2 is arranged. Here, the apparatus 2 is formed in a separate pipe section 21 in which an annular tracer chamber 22 is arranged, extending uninterruptedly around the entire periphery of the pipe bore 11 and substantially in the entire length of the pipe section 21. An internal chamber wall 23 bounds the tracer chamber 22 towards the pipe bore 11. The chamber wall 23 includes several portions 231 with a corrosion resistance CR.sub.2, which is smaller than the general corrosion resistance CR, of the elements forming the pipe bore 11, and thereby also smaller than the general corrosion resistance CR, of the chamber wall 23. It is indicated here by said portions 231 having a smaller wall thickness than the internal chamber wall 23 in general. This wall thickness is so small that a correspondingly deep corrosion in the internal structure of the pipeline 1 will not have a critical effect on the strength of the pipeline 1. Said wall portions 231 may be given a weakened corrosion resistance also by other means, for example by the choice of a material with less specific corrosion resistance than the materials that are used in the pipeline 1 in general, or by said portions being subjected to greater material stresses, that is to say being strained more than the chamber wall 23 in general, by structural means, for example by being tensioned against adjacent chamber-wall elements (not shown).

[0042] Said chamber 22 is filled with a tracer 24. The tracer may be of any kind, which is suitable for dissolving in the fluid flow 12, which is to be carried through the pipe bore 11. The tracer is typically arranged in porous polymer rods.

[0043] Downstream of the corrosion-detection apparatus 2, the pipeline 1 is provided with at least one tracer detector 711 connected in a signal-communicating manner to the operation and control system 71. The tracer detector 711 is preferably arranged in some place on the pipeline 1 where it is easy to supply energy for the operation of the tracer detector 711 and where a connection can easily be established for the transmission of control signals et cetera between said detector 711 and the operation and control system 71. For a production well in a hydrocarbon field, it is obvious to place a tracer detector 711 on or at a wellhead (not shown). For a transport pipeline, a favourable place may be at a pump station (not shown).

[0044] When the wall 23 of the tracer chamber 22 has been corroded through, the tracer 24 is released and carried in the fluid flow 12 through the pipeline 1. The tracer detector 711 registers the occurrence of the tracer 24 and the operation and control system 71 indicates that the corrosion in the pipeline has reached a certain level.

[0045] If the corrosion-detection apparatus 2 includes several tracer chambers 22, each with chamber wall portions 231 with different resistances to corrosion and with different tracers, the operation and control system 71 may indicate when the corrosion in the pipeline has reached further, higher levels.

[0046] Reference is now made to FIG. 2. Here, a second tracer 33 is shown enclosed in a second tracer chamber 32 arranged in a sacrificial anode 3, that is to say a depot containing a sacrificial material 31, typically zinc, which may be placed in a suitable place in the pipeline 1 to protect the interior of the pipeline 1 from corrosion. When the second tracer 33 is found in the fluid flow 12 in the pipeline 1 by means of the tracer detector 711, this may be taken as a signal of the sacrificial material 31 being nearly spent, lopment of corrosion in the pipeline 1 may be expected.

[0047] In FIG. 3, an assembly of several different apparatuses for detecting conditions in a pipeline 1, especially in a hydrocarbon well, by means of tracers is shown. A scale-control apparatus 4 may, for example, provoke early scaling to give an indication of whether the environment in the well involves a risk of developing scale. A scale-detection apparatus 5 gives an indication of how far the scale has developed. An inhibitor-detection apparatus 6 may give an indication of whether a structure is still releasing a previously injected inhibitor, for example a production-promoting inhibitor. Finally, the assembly includes a corrosion-detection apparatus 2 according to the invention.

[0048] It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive. The use of the verb “to comprise” and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article “a” or “an” before an element does not exclude the presence of several such elements.

[0049] The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.