The present invention relates to plugs for use in a wellbore, for example to such plugs suitable for use with side pocket mandrels in a production tubing during petroleum production.
During downhole operations in petroleum production, there are in certain situations a need for communication between a production tubular and an outer annulus between the production tubular and the well casing. Two examples of such downhole operations are gas lift and chemical injection. During gas lift, injecting gas into the production pipe from the annulus assists the production, i.e. the well flow. Similarly, chemical injection can be used, wherein chemicals are injected into the production pipe.
Typically, a controlled amount of gas or chemicals can be injected by means of a control device, which can, for example, be integrated into a side pocket mandrel (SPM) in the production tubular. Such a control device will typically comprise one or more valves disposed in openings in the production pipe, thereby permitting a controlled fluid communication between the annulus and the inside of the production pipe. In some cases, a plurality of valves are provided in series to achieve a double (or multiple) barrier. Documents which may be useful for understanding the background include international patent applications WO 2014/118380 A2 and WO 2016/003890 A1, and US patent document U.S. Pat. No. 6,932,581 B2, U.S. Pat. No. 5,054,558 and US 2010/0122819 A1.
A well goes through several phases during its lifetime. Production rates will usually decline as the well gets more mature, because reservoir pressure drops. Various means can be employed to counteract such a decline in production, for example downhole pumps, gas lift or chemical treatment. There may also be a need for stimulation of the reservoir itself, e.g. through fracturing, chemical treatment, or similar.
When using gas lift valves arranged in SPMs in the production tubing, there may be a considerable period between completion of the well and start of production, and the time at which the pressure has dropped to a level where gas lift is required. This period may be several years. During this time there is no need to have idle valves installed in the SPM, and it may be disadvantageous since such valves may be subjected to clogging, erosion, or other negative effects. In such cases, complicated and laborious operations may be required to repair or replace the valves. Also for the purpose of various other well operations it may be an advantage not having SPM valves installed from the time of completion.
Rather than leaving operational valves installed, unused and idle, it is common to use so-called dummy plugs. These are, in principle, plugs which close the connection between the annulus and the production tubing. When required, the dummies can then be replaced with operational valves in a well intervention operation.
Since the installation of such dummies takes place downhole, it is important that these are easy to install and remove, with low risk of error. Moreover, such dummies may be installed and left in place for long periods of time, commonly several years, and may be subjected to very harsh conditions downhole. It is therefore of critical importance that these dummies are reliable and have low failure rates.
The present invention aims to address challenges and limitations with known technology and provide improved solutions and techniques in relation to such plugs.
In an embodiment, there is provided a downhole plug, having
In an embodiment, the first part and the second part has a surface,
In an embodiment, the first part is coupled to the second part by means of a telescopic connector.
In an embodiment, the telescopic connector comprises a pin fixed to the second part, the pin being slidably arranged in a receiver fixed to the first part.
In an embodiment, the pin comprises a surface having a normal vector, the normal vector having an angle in relation to the longitudinal axis which is different than 90 degrees, and the receiver comprises a port arranged to provide fluid communication between the outside of the plug and the surface.
In an embodiment, the first part forms a back section of the plug and the second part forms a front section of the plug.
In an embodiment, the first part and the second part have substantially circular cross sections, and the cross section of the second part is smaller than the cross section of the first part.
In an embodiment, there is provided a downhole plug, having
In an embodiment, the plug further comprises a pressure control device arranged between the fluid port and the fluid chamber and configured to control the flow of fluid between the fluid port and the fluid chamber.
In an embodiment, the pressure control device is configured to open or break upon being subjected to a pressure exceeding a pre-determined threshold pressure.
In an embodiment, the pressure control device is a rupture disc, a piston, or a rupture pin.
In an embodiment, the pressure control device is a valve.
In an embodiment, the valve is configured to open when subjected to a pressure exceeding a pre-determined threshold pressure.
In an embodiment, the fluid chamber comprises a pressure compensation unit.
In an embodiment, the pressure compensation unit comprises a piston acting against a pre-loaded spring, a piston acting against a compressible gas, or a bladder.
In an embodiment, the plug further comprises a connector configured for engagement with an installation tool.
In an embodiment, the plug is a dummy plug for sealing an opening in a production tubing.
In an embodiment, there is provided a production tubing for a petroleum well, comprising a pipe, at least one side pocket mandrel, and at least one plug.
Illustrative embodiments will now be described with reference to the appended figures, in which:
The body 1 comprises a first part 3 and a second part 4, and the first seal 5 is arranged on the first part 3 and the second seal 6 is arranged on the second part 4. The first part 3 is coupled to the second part 4 and movable in relation to the second part 4 in the direction of the longitudinal axis of the body.
The first part 3 forms a back section 20 of the plug 100 and the second part 4 forms a front section 21 of the plug 100. The first part 3 and the second part 4 have substantially circular cross sections 3a,4a (illustrated in
The first part 3 is coupled to the second part 4 by means of a telescopic connector 10. The telescopic connector 10 comprises a pin 12 fixed to the second part 4, the pin being slidably arranged in a receiver 11 fixed to the first part 3. Relative movement between the first part 3 and the second part 4 in the longitudinal direction 2 of the plug body is therefore made possible.
Depending on the operational requirements and the state of the well, a valve can be arranged in the slot 53. In the case of gas lift, pressurised gas can then be supplied to the inlet 51 and selectively led to the outlet 52 by the valve.
Alternatively, a dummy plug 100 can be arranged in the slot 53. The plug has the objective to seal between the inlet 51 and the outlet 52 in a reliable manner, for example when the well is producing sufficiently as a result of the existing reservoir pressure, and no gas lift is required.
A problem which may occur when using such plugs is that one in certain situations can experience an undesired pressure build-up between the seals 5 and 6. This may occur, for example, if the inlet 51 is closed upstream of the SPM, for example if the inlet 51 is connected to a second SPM which holds a plug or a closed valve. (This is common in configurations which are set up for using two or more gas lift valves in series.) In such a case, the inlet 51 and the volume between the seals 5 and 6, as soon as these seal against the walls of the SPM 61, may form a closed, liquid-filled volume. When installing the plug, this volume will be reduced as the plug is moved into the slot 53, and the trapped liquid may cause a significant pressure build-up, which may damage the seals 5 and 6. This may also cause so-called hydro-locking, i.e. prevent a correct installation of the plug in the slot. Further, when installed, the liquid trapped in this volume may be subjected to large temperature variations during the petroleum production processes. This may cause the trapped liquid to expand or contract, which may also cause excessive, and varying, pressure differentials across the seals 5 and 6.
When the plug 100 is exposed to a large pressure increase in the space between the seals 5 and 6, the first part 3 will be urged away from the second part 4. Since the first part 3 and second part 4 are movable relative to one another, this motion reduces the pressure of the trapped liquid, thereby ensuring that the seals 5 and 6 are not damaged. Similarly, if the pressure in the trapped volume is reduced, and the seals 5 and 6 is exposed to a large pressure differential in the opposite direction, the first part 3 and the second part 4 will move towards each other and thus reduce the load on the seals.
The first part 3 may have at least one surface 7a,7d on which this pressure acts, and which thereby aids the motion of the first part 3 relative to the second part 4. Similarly, the second part 4 may have at least one surface 7b,7c which aids the motion of the second part 4 relative to the first part 3. This is illustrated in
The surfaces 7a,7b,7c,7d each have a normal vector 8 (illustrated only in relation to surface 7c). The normal vector need not be the same for all surfaces. The normal vector has an angle in relation to the longitudinal axis 2 which is different than 90 degrees. When subjected to a pressure from the fluid trapped between the seals 5 and 6, each surface thereby produces a pressure force which urges the first part 3 away from the second part 4. The normal vector does not need to be parallel to the longitudinal axis 2, it is sufficient that there is an angle such that a pressure force component in the direction of the longitudinal axis 2 is generated.
The pin 12 may comprise a surface 7c and the plug may further comprise a port 13 (see
As described above, in certain situations there may be a pressure build-up between the first seal 5 and the second seal 6. In such a case, the pressure control device 42 may admit fluid into the fluid chamber 40, thereby reducing the pressure acting on the seals 5 and 6.
The pressure control device 42 may be a rupture disc, a piston, a piston held in place by a rupture pin, or any other element which is configured to break upon being subjected to a pressure exceeding a pre-determined threshold pressure.
The pressure control device 42 may, alternatively, be a valve. The valve may be pressure-controlled such as to open when subjected to a pressure exceeding a pre-determined threshold pressure.
The fluid chamber 40 may comprise a pressure compensation unit. This is illustrated in
The pressure compensation unit may be of any suitable type, such as a piston acting against a pre-loaded spring, a piston acting against a compressible gas, a bladder accumulator, or an equivalent arrangement.
In a further embodiment according to the invention, illustrated in
By providing a production tubing as illustrated in
The scope of the invention is not limited to the embodiments described herein; reference should be had to the appended claims.
Number | Date | Country | Kind |
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20160961 | Jun 2016 | NO | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NO2017/050140 | 6/1/2017 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2017/209626 | 12/7/2017 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
2601614 | Johnson | Jun 1952 | A |
4359094 | Risinger | Nov 1982 | A |
5054558 | Barneck | Oct 1991 | A |
6932581 | Messick | Aug 2005 | B2 |
7845401 | Wildman | Dec 2010 | B2 |
20100084139 | Moreno | Apr 2010 | A1 |
20100122819 | Wildman et al. | May 2010 | A1 |
Number | Date | Country |
---|---|---|
2014118380 | Aug 2014 | WO |
2016003890 | Jan 2016 | WO |
Entry |
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PCT International Search Report; PCT/NO2017/050140; dated Sep. 22, 2017. |
Norwegian Search Report; NO 20160961; dated Dec. 16, 2016. |
Number | Date | Country | |
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20200123872 A1 | Apr 2020 | US |