An Arrangement for Forming a Freeze Plug in a Tubing

Abstract

An arrangement is for forming a freeze plug in a tubing. The arrangement includes a first and a second displacement element adapted to be displaced within the tubing with a medium between them that is adapted to form the freeze plug. The first and the second displacement elements include, at least at a respective end portion facing the medium between them, a sensor arrangement for measuring at least one of a pressure and a temperature.

Claims

1. An arrangement for forming a freeze plug in a tubing, the arrangement comprising: an elongated first displacement element and an elongated second displacement element adapted to be displaced within the tubing with a medium between them that is adapted to form said freeze plug, wherein the first displacement element and the second displacement element comprise, at least at a respective end portion facing the medium between them, a sensor arrangement for measuring at least one of a pressure and a temperature.

2. The arrangement according to claim 1, wherein the first displacement element and the second displacement element comprise, at each of their two end portions, a sensor arrangement for measuring at least one of a pressure and a temperature.

3. The arrangement according to claim 1, wherein the arrangement comprises one or more detection devices for detecting the displacement elements within the tubing, which one or more detection devices are adapted to be positioned at the tubing at a desired location for at least one of the displacement elements.

4. The arrangement according to claim 1, wherein the arrangement comprises a measuring unit adapted to receive information from the sensor arrangement and determining at least one of the pressure and the temperature of the respective end portion of the displacement elements.

5. The arrangement according to claim 1, wherein the arrangement further comprises a freeze element adapted to be arranged around the tubing for forming the freeze plug.

6. The arrangement according to claim 1, wherein the arrangement further comprises a monitoring unit for collecting the measurements of the sensor arrangement and determining if a sufficient freeze plug has been formed on basis of the measurements.

7. The arrangement according to claim 1, wherein the arrangement further comprises an elongated third displacement element, and wherein the first and the second displacement element are adapted to be displaced within the tubing with the medium between them for forming the freeze plug, and the second and third displacement element are adapted to be displaced within the tubing with the medium between them for forming a further freeze plug.

8. A method for forming a freeze plug in a tubing, the method comprising: displacing an elongated first displacement element and an elongated second displacement element within the tubing with a medium between them that is adapted to form said freeze plug, positioning the first displacement element and the second displacement element at respective parts of the tubing in between which the freeze plug is to be formed, freezing the tubing between the first displacement element and second displacement element, thereby forming the freeze plug, measuring at least one of the pressure and temperature on respective end portions of the displacement elements facing the medium between them, and determining if the freeze plug has a sufficient quality on basis of a difference in at least one of the pressure and the temperature between the displacement elements.

9. The method according to claim 8, wherein if the difference between least one of the pressure and the temperature at an end portion of the first displacement element facing the freeze plug and a corresponding end portion of the second displacement element facing the freeze plug is less than a threshold value, it is determined that a freeze plug with sufficient quality has been formed.

10. The method according to claim 8, wherein the method comprises displacing the first displacement element and the second displacement element within the tubing with the medium between them for forming the freeze plug, and displacing the second displacement element and an elongated third displacement element with the medium between them for forming a further freeze plug.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0031] In the following are described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

[0032] FIG. 1 discloses an arrangement for forming a freeze plug in a tubing according to an embodiment of the invention;

[0033] FIG. 2 discloses an example of a displacement element of the arrangement in FIG. 1;

[0034] FIG. 3 discloses a flowchart of a method for forming a freeze plug in a tubing according to an embodiment of the invention.

DETAILED DESCRIPTION

[0035] In FIG. 1 an arrangement 1 for forming a freeze plug 3a in a tubing 5 according to an embodiment of the invention is disclosed. The tubing 5 is for example a pipeline used for conducting oil and gas.

[0036] A section 7 of the tubing 5 is to be repaired. In FIG. 1, for illustration purposes the repair depicted in this case relates to replacement of a damaged valve 9 on the tubing with a new valve. Before initiating repair operation, the section 7 of the tubing 5 needs to be isolated from the rest of the tubing 5. In FIG. 1, the section 7 of the tubing is isolated from the tubing by means of forming the freeze plug 3a and a further freeze plug 3b.

[0037] The arrangement 1 comprises an elongated first displacement element 10a, an elongated second displacement element 10b and an elongated third displacement element 10c. The displacement elements 10a, 10b, 10c are adapted to be displaced within the tubing 5 with a medium between them. The medium is adapted to be frozen into the freeze plug 3a and the further freeze plug 3b. The medium is preferably water. However, another medium, such as oil, may also be solidified to form the freeze plug.

[0038] The displacement elements 10a, 10b, 10c are often denoted pipeline pigs or pipeline scrapers and are used in tubing operations. The displacement elements 10a, 10b, 10c are displaced within the tubing 5 by means of a flow of the medium through the tubing 5.

[0039] The arrangement 1 further comprises detection devices 15 for detecting the displacement elements 10a, 10b, 10c within the tubing 5. The detection devices 15 are positioned at the tubing 5 on desired locations for the displacement elements 10a, 10b, 10c within the tubing 5. The detection devices 15 comprise for example a sensor that detects the displacement elements 10a, 10b, 10c on basis of magnetic field, radio-transmission, ultra sound, et cetera.

[0040] When the displacement elements 10a, 10b, 10c have been positioned in their desired locations in the tubing 5, a respective freeze element 20 is arranged at the location between the first and the second displacement elements 10a, 10b for forming the freeze plug 3a, and between the second and the third displacement elements 10b, 10c for forming a further freeze plug 3b. The freeze element 20 comprises a chamber adapted to receive a cooling medium, such as liquid nitrogen, carbon dioxide, et cetera, for solidifying the medium between the displacement elements 10a, 10b, 10c.

[0041] Each of the displacement elements 10a, 10b, 10c comprises a respective sensor arrangement 30 at their end portions for detecting pressure and a temperature. The arrangement 1 further comprises a measuring unit 32 adapted to receive information from the sensor arrangements 30 and determining the pressure and the temperature of the respective end portion of the displacement elements 10a, 10b, 10c.

[0042] The information from the sensor arrangements 30 is transmitted through the tubing 5 by means of radio communication or other wireless means of communication. The displacement elements 10a, 10b, 10c comprise a respective transmitter 34 for transmitting information to a respective receiver 36 at the outside of the tubing 5. The measuring unit 32 is connected to the receiver 36 and is adapted to receive pressure and temperature information from the sensor arrangements 30.

[0043] The arrangement 1 further comprises monitoring unit 40 for collecting the measurements of the sensor arrangements 30 and determining if a sufficient freeze plug 3a and further freeze plug 3b have been formed on basis of the measurements. The monitoring unit 40 comprises for example a logic unit 42, such as a CPU, and means for storing data 44, such as a hard disc drive. Preferably, the arrangement also comprises a display unit 46 for displaying the pressure and the temperature, and the determination on the quality of the freeze plug 3a and further freeze plug 3b.

[0044] The determinations on the quality of the freeze plug 3a and further freeze plug 3b are made on basis of difference between the measurements on different ends of the freeze plug 3a and the further freeze plug 3b. In particular, the determination is based on if the difference between measurements below a threshold value.

[0045] In FIG. 2, an example of the first displacement element 10a of the arrangement 1 in FIG. 1 is disclosed in further details. Preferably, the second and third displacement element 10b, 10c are provided with the corresponding features. The first displacement element 10a is arranged within the tubing 5.

[0046] The first displacement element 10a comprises an elongated form comprising two opposite end portions. In the disclosed example, one of the end portions is facing the freeze plug 3a and the other end portion is facing the section 7 of the tubing 5 to be repaired.

[0047] The first displacement element 10a comprises a respective contact flange 50 at the two end portions. The contact flange 50 has the function of providing a contact between the first displacement element 10a and an inner envelope surface of the tubing 5. The contact flange 50 of the first displacement element 10a enables the medium to essentially be maintained between two adjacent displacement elements 10a, 10b, 10c during the duration of freezing the medium to the freeze plug 3a or the further freeze plug 3b.

[0048] The first displacement element 10a comprises two sensor arrangements 30 arranged in respective end portions. In the disclosed embodiment, the sensor arrangements 30 are contained within the displacement element 10a. The sensor arrangements 30 comprise a pressure sensor element 52 and a temperature sensor element 54. The sensor elements 52, 54 are connected to the transmitter 34 that is adapted to transmit information on the pressure and temperature measurements to the receiver 36 outside the tubing 5.

[0049] In FIG. 3 a flowchart of a method for forming a freeze plug 3a in a tubing 5 according to an embodiment of the invention is disclosed.

[0050] In a step 110, the method comprises displacing the first and the second displacement elements 10a, 10b within the tubing 5 with a medium between them. The displacement is done by means of a flow of the medium. The displacement comprises first arranging the first displacement element 10a in a launcher and introducing the first displacement element in the tubing. After the first displacement element 10a has been displaced a certain length within the tubing 5, the second displacement element 10b is arranged in the launcher and introduced in to the tubing 5.

[0051] In a step 120, the method comprises positioning the first and the second displacement elements 10a, 10b at respective parts of the tubing in between which the freeze plug 3a is to be formed. Preferably, at least one of the first and second displacement elements 10a, 10b are detected by means of one or more detection devices 15 arranged at the outside of the tubing 5.

[0052] In a step 130, the method comprises freezing the tubing 5 between the first and the second displacement element 10a, 10b. Thereby freeze plug 3 is formed. The tubing is preferably frozen by means of arranging a freeze element 20 at the outside of the tubing 5.

[0053] In a step 140, the method comprises measuring the pressure and/or the temperature on respective end portions of the first and second displacement elements 10a, 10b, which end portions facing the medium between them.

[0054] In a step 150, the method comprises determining if a freeze plug 3a of sufficient quality has been formed on basis of a difference in at least one of the pressure and the temperature between the displacement elements 10a, 10b. Preferably, the determination is based on if the difference between the pressure and/or the temperature is less than a threshold value.

[0055] In case when the further freeze plug 3b is formed between the second and third displacement elements 10b, 10c, the quality of the further freeze plug 3b can determined in a corresponding manner to the determination of the freeze plug 3a.

[0056] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb comprise and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article a or an preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.