Patent Grant
10450821
The present invention relates to a wellhead port plug assembly comprising a first plug body comprising connection elements allowing the first plug body to be sealingly and removably mounted in a port of a wellhead of a hydrocarbon well, i.e. an oil and/or gas well.
The invention also relates to a wellhead of a hydrocarbon well comprising such a plug assembly and to a method of replacing the first plug of the plug assembly.
In particular, the invention relates to a method of replacing the first plug without interrupting production of the well.
It is common to provide a wellhead of a hydrocarbon well with ports allowing the mounting of devices for monitoring the annuli of the well. For example, such a device is disclosed in WO 2013/056857 A1, which is hereby incorporated by reference. Generally, a system for monitoring an annulus via a wellhead port comprises a plug body which is positioned in the port and comprises at least one sensor for measuring and monitoring at least one parameter in the annulus, e.g. pressure or temperature. In addition to provide a measuring or monitoring function, the plug body must provide a sealing function to prevent leakage to or from the annulus.
US 2012/012341 A1 discloses a wellhead port plug assembly comprising a first plug body which is arranged in an outlet port of the wellhead. The plug assembly further comprises a spool which is aligned with the outlet port. A second plug body is arranged in the spool. The first and second plug bodies can be removed from the well head assembly via the spool upon removal of a blind flange from the spool.
WO 2001/57360 A1 discloses a well data monitoring system which enables annulus pressure and other well parameters to be monitored in the outer annuli of the well casing program without adding any pressure containing penetrations to the well system.
WO 2006/061645 A1 discloses a plug retrieval and installation tool comprising a housing that is lowered on a lift line or riser and connected to subsea production equipment. A plug manipulator which can be extended to install, or retracted to retrieve, a plug-type barrier, is detachably mounted to the housing so that it can be retrieved independently of the housing. The installation tool eliminates the need for full-size intervention vessels or drilling rigs for plug retrieval/installation.
Furthermore, when not utilised for monitoring and measuring purposes, the port must be blocked in order to prevent leakage. This is normally accomplished by positioning a blind plug in the port such that the port is blocked. A blind plug is basically a plug body having no other purpose than to provide a sealing or plugging function.
A problem related to plug bodies positioned in wellhead ports of a hydrocarbon producing well, is that the well need normally to be taken out of production if the plug body is to be replaced. For example, a plug body may occasionally leak, in which case the plug body may need to be substituted for a new plug body. Also, it may be desirable to deploy a monitoring or measuring system in a previously unused port, in which case the blind plug needs to be removed and a plug body comprising a sensor needs to be positioned in its place.
In prior art plug assemblies, the well normally needs to be taken out of production in order for the plug body in the port to be replaced. This, of course, is a major disadvantage in a business where well uptime is paramount.
The present invention addresses this problem and seeks to provide a wellhead port plug assembly and a method allowing replacement of a plug body without having to take the well out of production.
The plug assembly according to the invention is characterised in that it comprises:
The method according to the invention comprises the steps of:
In the following, embodiments of the invention will be disclosed in more detail with reference to the appended drawings.
When the hydrocarbon well is in production, a production tubing (not disclosed) will be arranged inside the fourth casing 7.
In order to monitor the wellhead 1, i.e. to detect an increased or a decreased of pressure indicative of pressure leaks, at least one plug assembly according to a first embodiment of the invention, which comprises a measuring and monitoring system, is arranged in the wellhead 1 such that well parameters can be measured and monitored. Such parameters may, for example, include the pressure and/or the temperature in one of annuli A-C of the wellhead 1. The wellhead 1 will then be configured with a through-bore or channel (not disclosed in
In order to get a more complete overview of the performance of the well, it may be advantageous to provide the wellhead 1 with more than one plug assembly, e.g. one plug assembly for each annulus.
The measurements made by the measuring and monitoring system may advantageously be transmitted to an external location for processing and analysis.
The assembly 20 comprises a first unit 23, a spool unit 24, a second unit 25 and a blind flange 26. In the present embodiment, the first and second units 23, 25 are sensor units.
The first sensor unit 23 comprises a plug body 27 which has a generally cylindrical form and comprises at least one sensor 18 (cf.
The spool unit 24 displays a through-bore or channel 32 which runs in the longitudinal or axial direction between a first end 24a and a second end 24b of the spool unit 24. The spool unit 24 comprises a housing 35 which is generally circular symmetric about the longitudinal axis of the spool unit 24. At the first end 24a, the housing 35 comprises a first flange section 33, and at a second end 24b the housing comprises a second flange section 34. The first flange section 33 is connected to the wellhead 21 by means of fastening means in the form of bolts 36 such that the channel 32 of the spool unit 24 is coaxial with the channel 22 of the wellhead 21. An annular sealing element 37 is positioned between the first flange portion 33 and the wellhead 21 to ensure a fluid-tight connection between the spool unit 23 and the wellhead 21. A first section 32a of the channel 32, which faces towards the wellhead 21, has a diameter which is less than a second section 32b facing away from the wellhead 21 such that that an annular shoulder 38 is formed within the channel 32 (cf.
The second sensor unit 25 comprises a plug body 42 which has a generally cylindrical form and comprises electronics for receiving signals from the sensors of the first plug body 27 and forwarding the signals to a signal transmission unit of the assembly (to be discussed below). The unit 25 may also comprise electronics for processing the signals prior to forwarding them, and electronics for communicating with the sensors. The plug body 42 comprises external threads 43 for cooperation with corresponding internal threads 44 of the channel 32 (cf.
The blind flange 26 is connected to the second flange section 34 of the spool unit 24 by means of fastening means in the form of bolts 47. An annular sealing element 48 is positioned between the blind flange 26 and the second flange section 34 to ensure a fluid-tight connection between the spool unit 23 and the blind flange 26. The blind flange 26 comprises a lead-through 49 which, on the inside of the blind flange 26, comprises a connector element 50 which is connected to a corresponding connector element (not disclosed) of the second sensor unit 25. The connector element 50 is connected to the unit 25 by means of an axial release coupling, i.e. a coupling which allows the connector element 50 to be connected and disconnected from the second sensor unit 25 upon a movement of the connector element 50 in the longitudinal or axial direction of the spool unit 24. On the outside of the blind flange 26, the lead-through 49 is connected to a signal transmission unit 66 for forwarding the signals to said external location. In the disclosed embodiment, the signal transmission unit 66 comprises a communication cable. Power for operating the sensors and the sensor electronics may be provided to the assembly 20 via the same cable 66. In an alternative embodiment (not disclose), the sensor signals are transmitted wirelessly to the external location. In such an embodiment, the cable may be substituted for wireless transmission means such as an antenna which advantageously is positioned on the outside surface of the blind flange. Also, in such an embodiment, a power supply, e.g. an electric battery, is advantageously arranged in the assembly, e.g. in the second sensor unit 24, to provide power to the sensors and to the associated electronics and signal transmission means.
The plug bodies 27 and 42 provide two independent barriers against the channel 22 and, consequently, against the annulus the assembly 20 is set to monitor. Should the spool unit 24 be knocked of the wellhead 21, e.g. due to a falling load hitting the spool unit 24, the connector elements 30 and 45 will separate and the first plug body will remain in the channel 22, thus preventing fluid in the annulus from escaping via the channel 22.
The spool unit and blind flange assembly enables the first sensor unit 23 and/or the second sensor unit 25 to be substituted while maintaining production in the well. In the following, a method of substituting the first sensor unit 23 while maintaining the pressure integrity of the wellhead 21 will be disclosed.
The first step of the method comprises removing the blind flange 26 from the second flange section 34 of the spool unit 24. When moving the blind flange 26 away from the second flange section 34 in the longitudinal or axial direction of the spool unit 24, the connector element 50 will automatically release from the second sensor unit 25 due to the axial release coupling between the connector element 50 and the sensor unit 25.
The next step comprises attaching a valve 51, e.g. a gate valve, to the spool unit 24, as is disclosed in
The next step comprises attaching a plug placement and removal tool 58 to the valve 51, as is disclosed in
When the tool 58 has been connected to the valve 51, the valve 51 is opened by bringing the valve body 56 to the open position and the arm 62 is extended such that the plug engagement element 63 is brought into contact with and connects to the tool engagement element 42 of the second sensor unit 25, as is disclosed in
Thereafter, the arm 62 and the attached second sensor unit 25 are retracted in the longitudinal or axial direction of the spool unit 24 such that the connector element 45 is released from the connector element 30 due to the axial release coupling between the connector elements 30 and 45. The arm 62 and the attached second sensor unit 25 are then withdrawn through the valve 51, whereafter the valve body 56 is brought to its closed position, as is disclosed in
The next step comprises detaching the tool 58 from the valve 51, removing the second sensor unit 25 from the arm 62, substituting the first plug engagement element 63 for a second plug engagement element 64 which is compatible with the tool engagement element 31 of the first sensor unit 23, and reattaching the tool 58 to the valve 51, as is disclosed in
Next, the valve 51 is once again opened by bringing the valve body 56 to the open position and the arm 62 is extended through the valve 51 and the spool unit 24 such that the plug engagement element 64 is brought into contact with and connects to the tool engagement element 31 of the first sensor unit 23, as is disclosed in
Thereafter, the arm 62 and the attached first sensor unit 23 are retracted in the longitudinal or axial direction of the spool unit 24 through the spool unit 24 and the valve 51, as is disclosed in
Next, the tool 58 is detached from the valve 24 and the first sensor unit 23 to be replaced is removed from the plug engagement element 64. Thereafter, a new first sensor unit is attached to the plug engagement element 64 and the tool 58 is reattached to the valve 51.
Next, the above-disclosed steps are performed in reversed order, i.e.:
When a through-bore or channel leading into one of the annuli A-C of the wellhead 1 is not utilised for monitoring purposes, the through-bore or channel may need to be plugged in order to prevent leakage.
The general structure of this second embodiment of the assembly 70 is generally the same as the above-disclosed first embodiment 20 and like parts have been denoted like reference numerals.
The assembly 17 comprises a first unit 71, a spool unit 24, a second unit 72 and a blind flange 79. However, in this case the first and second units 71 and 72 are not sensor units but blinds, each comprising a plug body 73, 74 arranged to provide a sealing function but not a monitoring or measuring function. Consequently, the assembly 70 lacks the monitoring and measuring features of the first assembly 20, e.g. connector elements corresponding to the connector elements 45 and 50, a signal transmission unit etc.
The first plug body 73 is positioned in the outermost section 22b of the wellhead channel 22, and the second plug body 74 is positioned in the though channel 32 of the spool unit 24. Consequently, the plug bodies 73, 74 form a double plug barrier preventing leakage from the wellhead channel 22. Furthermore, even if the spool unit 24 should be damaged, e.g. knocked of the wellhead 21 by a falling load, the first plug body 73 will remain in the wellhead channel 22 and prevent uncontrolled leakage from the channel 22.
The method of substituting the first plug body 73 is generally the same as the above-disclosed method of substituting the plug body 27, i.e. it comprises the steps of:
For co-operating with the plug engagement elements 63, 64 of the tool 58 (see
In an alternative embodiment, it may be advantageous to rotate only the plug engagement element 63, 64, which is attached to the outer end of the arm 62, about the longitudinal axis.
As the spool unit of the first plug assembly 20 (see
The channels 39, 75 and 76 may be utilised at any one of above-disclosed steps, e.g. to verify the integrity of the plug assembly. For example, any one of channels 75 and 76 may be utilised to verify the integrity of the second unit 72 prior to removing the blind flange 26.
In the preceding description, various aspects of the assembly according to the invention have been described with reference to the illustrative embodiment. For purposes of explanation, specific numbers, systems and configurations were set forth in order to provide a thorough understanding of the assembly and its workings. However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiment, as well as other embodiments of the assembly, which are apparent to persons skilled in the art to which the disclosed subject matter pertains, are deemed to lie within the scope of the present invention. For example, instead of first attaching the valve 51 to the spool unit 24 and then attaching the tool 58 to the valve, the skilled person readily understands that a possible alternative is to first attach the tool 58 to the valve 51 and then attach the valve-spool assembly to the spool unit 24. Also, after completion of the substitution of the first sensor unit, the valve 51 and the tool 58 may be removed in the same manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20140536 | Apr 2014 | NO | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/058880 | 4/24/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/162241 | 10/29/2015 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20010011593 | Wilkins | Aug 2001 | A1 |
| 20120012341 | White et al. | Jan 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 2 461 402 | Sep 2005 | CA |
| WO 0157360 | Aug 2001 | WO |
| WO 2006061645 | Jun 2006 | WO |
| WO 2013056857 | Apr 2013 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20170044861 A1 | Feb 2017 | US |
