Patent Application
20140238675
The present invention relates to a downhole injection tool for injecting an injection fluid into an annular space surrounding the downhole injection tool and enclosed by an inside wall of a borehole or a well tubular structure. Furthermore, the present invention relates to a downhole system comprising the downhole injection tool as well as to a method for casting a cement plug downhole.
In the field of hydrocarbon production, it is sometimes necessary to block the wellbore, e.g. to seal of part of the well. In substantially vertical wells, this may be done by setting some kind of plug and pouring cement into the well. When the cement cures, a plug in the wellbore is created. Depending on the materials used for creating the plug, it may be possible to drill through the plug to restore the flow path. Alternatively, the plug may be a permanent plug.
However, in deviated wells, it is not possible to cast a plug by simply pouring cement into the borehole. In deviated wells, such as wells having an inclination close to horizontal, the process of casting a plug is much more complicated.
Injection of a fluid such that the injected fluid fills up all of the available space of a section of the wellbore, either open or cased, is especially challenging in a deviated well inter alia due to gravity. If a plug is set in the well and a fluid is injected above the plug, the fluid will naturally level out in the well above the plug. If the well is highly deviated, it is practically impossible to make the fluid fill out a cross section of the wellbore. If the fluid is to fill out the cross section of the well over a section of the well, e.g. if a plug with a certain length is required, the task becomes even more difficult.
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 injection tool for injecting a fluid into a wellbore to fill up and fully block the wellbore.
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 injection tool for injecting an injection fluid into an annular space surrounding the downhole injection tool and enclosed by an inside wall of a borehole or a well tubular structure, the downhole injection tool comprising:
In an embodiment, the injection unit may be adapted to be disconnected from the remainder of the downhole injection tool.
A length of the at least one pipe element may be adjusted according to the desired length of the isolated zone. Hereby, the length of a cement plug or the length of a section of the well exposed to the injected injection fluid may be adjusted according to specific needs.
Moreover, the retainer sleeve may comprise a first sleeve part and a second sleeve part movable in relation to one another.
The first sleeve part and the second sleeve part may have an internal diameter being smaller than a largest expanded outer diameter of the second expandable cup.
In addition, the first and second sleeve parts may comprise locking means for releasably interconnecting the first and second sleeve parts.
Furthermore, the locking means may comprise a snap mechanism constituted by one or more flexible elements attached to the second sleeve part, the one or more flexible elements being adapted to engage with a recess in an outer surface of the first sleeve part.
Also, the downhole injection tool may comprise breakable retainer elements adapted to prevent unintentional expansion of the expandable cups during insertion of the downhole injection tool in the well, the retainer elements being broken during expansion of the expandable cups.
In an embodiment, the downhole injection tool as described above may further comprise a fluid container in fluid communication with the pipe element, the fluid container containing the injection fluid to be injected into the isolated zone between the two cups via the pipe.
By the downhole injection tool comprising a fluid container, the downhole injection tool may be run on wireline, and the injection unit may be used in deep or deviated wells.
Additionally, the downhole injection tool as described above may further comprise a pump for forcing the injection fluid through the pipe element and into the isolated zone, the pump being in fluid communication with the annular space and fluidly connected to the fluid container to pump driving fluid from the annular space into the fluid container in order to squeeze the injection fluid out of the fluid container and into the pipe element.
By the downhole injection tool comprising a pump, the downhole injection tool may be run on wireline, and the injection unit may be used in deep or deviated wells.
Further, the fluid container may comprise a driving piston arranged inside the fluid container, the driving piston being movable in the longitudinal direction and displaceable by the driving fluid pumped into the fluid container by the pump, the driving piston comprising a driving piston locking mechanism adapted to prevent the driving piston from moving until a pressure inside the fluid container reaches a predetermined threshold value due to driving fluid being pumped into the fluid container.
The predetermined threshold for the pressure may be 0.5-3 bar excess pressure compared to the borehole pressure, preferably 0.5-1.5 bar excess pressure compared to the borehole pressure.
In an embodiment, the driving piston locking mechanism may comprise one or more spring biased pawls adapted to engage with a recess in a wall of the fluid container.
Also, the injection unit may further comprise an activation piston arranged inside the pipe element and connected with the retainer sleeve, the activation piston being movable upon injection of the injection fluid through the pipe element, whereby injection of the injection fluid moves the activation piston and the retainer sleeve in the longitudinal direction to release the expandable cups.
In addition, the activation piston may comprise an activation piston locking mechanism adapted to prevent the activation piston from moving until a pressure inside the fluid passage of the pipe element reaches a predetermined threshold value due to injection fluid being pumped into the injection unit.
Moreover, the predetermined threshold for the pressure may be 5-8 bar excess pressure compared to the borehole pressure, preferably 6-7 bar excess pressure compared to the borehole pressure.
Furthermore, the activation piston locking mechanism may be comprised by a cylindrical chamber provided in the activation piston, a slidable piston arranged in the cylindrical chamber, the locking piston being movable between a locking position and a release position and under the influence of a spring member arranged in the cylindrical chamber, and one or more locking elements slidably received in one or more radial bores in the activation piston, the one or more locking elements being locked in an extended position by the locking piston when the locking piston is in the locking position and slidable in a radial direction when the locking piston is displaced in the longitudinal direction towards the spring member by the injected injection fluid.
In an embodiment of the downhole injection tool according to the present invention, both the first and the second expandable cups may be slidably connected with the pipe element.
Additionally, the injection unit may comprise a check valve in fluid communication with the pipe element for preventing return flow of the injection fluid injected into the injection unit from the fluid container. The check valve is described in detail in the international patent application, international publication number WO 2008/085057, which is hereby incorporated by reference.
Also, the injection unit may be a casting unit for casting a cement plug downhole.
Further, the fluid container may be a cement bailer.
In addition, the injection unit may be a fluid treatment unit for exposing part of the well to a treatment fluid, such as an acid, cleaning fluid, etc.
Each of the expandable cups may comprise a connection element connected with the pipe element, a flexible sleeve having a first end connected with the connection element, and a plurality of spring elements arranged around the flexible sleeve to at least partly expand the flexible sleeve.
The downhole injection tool as described above may comprise an expansion mechanism adapted to expand the expandable cups downhole.
In an embodiment, the downhole injection tool may comprise shape memory alloys adapted to expand the expandable cups downhole.
Also, each of the expandable cups comprises an inflatable bladder encircling the pipe section.
Moreover, each of the expandable cups may further comprise a sealing material arranged along an edge in a second end of the flexible sleeve.
The downhole injection tool as described above may further comprise an ejection mechanism adapted to disengage the injection unit from the fluid container and thus from the remainder of the downhole injection tool, the ejection mechanism being activated when a pressure inside the fluid container reaches a predetermined threshold value due to driving fluid being pumped into the fluid container.
Furthermore, the predetermined threshold for the pressure may be 2-7 bar excess pressure compared to the borehole pressure, preferably 2-5 bar excess pressure compared to the borehole pressure.
Additionally, the ejection mechanism may comprise a cylindrical housing, one or more locking pawls, a piston sleeve slidably arranged inside the cylindrical housing and movable between a locking position and a release position, and a spring member pushing the piston sleeve in the longitudinal direction, the locking pawls being slidably received in one or more radial bores in the cylindrical housing and locked in an extended position by the piston sleeve when the piston sleeve is in the locking position and slidable in a radial direction when the piston sleeve is displaced in the longitudinal direction towards the spring member by the injected driving well.
Also, the piston sleeve of the ejection mechanism may be displaced in the longitudinal direction towards the spring member by the driving piston engaging with the piston sleeve to block the flow through the piston sleeve.
In an embodiment, the downhole injection tool may comprise an electrical motor powered through a wireline for driving the pump.
Further, the driving fluid may be a well fluid drawn in from the annulus surrounding the downhole injection tool.
The present invention also relates to a downhole system comprising the downhole injection tool as described above and a downhole tractor connected to one end of the downhole injection tool, the tractor being adapted to push the downhole injection tool into the borehole before the expandable cups are released and the injection fluid injected.
The present invention further relates to a method for casting a cement plug downhole using the downhole injection tool as described above, the method comprising the steps of:
The driving fluid may be a well fluid drawn in from the annulus surrounding the downhole injection tool.
The method for casting a cement plug downhole may further comprise the step of disconnecting the injection unit from the remainder of the downhole injection tool.
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
a-1c show the downhole injection tool according to an embodiment of the invention,
a shows an injection unit with two expandable cups in an expanded position,
b shows another injection unit with two expandable cups in an expanded position,
a shows the driving piston positioned in the bottom of the fluid container,
b shows a cross section of
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.
a-1c show a downhole injection tool 1 comprising a downhole tractor section 6 for pushing the downhole injection tool forward in a well, a pump 8 for pumping a driving fluid into the downhole injection tool, a fluid container 9 containing an injection fluid to be injected downhole, and an injection unit 10 through which the injection fluid is injected into a well 4, as shown in
The injection unit 10 extends in a longitudinal direction 13 and comprises a first section 101 through which the injection unit is connected to the fluid container 9 and thus the remainder of the downhole injection tool. From an inlet 104 arranged in the first section of the injection unit, a fluid passage 108 extends to a second section 110 of the injection unit. Towards the inlet 104, the first section has a wider part 102 in which a check valve 106 and a recess 107 are provided for engaging with an ejection mechanism of the fluid container. Towards a second end 105 of the first section 101, a length 103 of reduced diameter for accommodating a centraliser mechanism 11 is provided. Various types of centraliser mechanisms are known to those skilled in the art, and further details of the centraliser will not be disclosed. The second end 105 of the first section is connected to an intermediate pipe section 130 connecting the first and the second section of the injection unit 10. The length of the intermediate pipe section 130 may be varied according to the specifications of the specific job to be carried out. The intermediate pipe section 130 is connected with a pipe element 111 of the second section 110, whereby fluid communication is established between the first and the second section of the injection unit 10. Surrounding the pipe element 111, a first expandable cup 118a and second expandable cup 118b are provided. In
The first expandable cup 118a and the second expandable cup 118b are adapted to provide a first seal 119a and a second seal 119b, respectively, against an inside wall 3a of a borehole or well tubular structure 3, as shown in
It is to be understood by those skilled in the art that the expandable cups may be constructed in a number of different ways without departing from the scope of the present invention.
Before inserting the downhole injection tool into the well, injection fluid is poured into the fluid container 9 and the first section 101 and the intermediate pipe section 130 of the injection unit. The injection fluid is poured into the tool through an opening positioned below the check valve 106 in
Subsequently, the downhole injection tool is inserted into the well, and when the downhole injection tool has been positioned in the well 4 by operating the downhole tractor section 6, the pump 8 is activated to pump driving fluid into the downhole injection tool 1 from the annular space 5a. The pump 8 is in fluid communication with the fluid container 9, and the driving fluid is forced into the fluid container to squeeze out the injection fluid contained therein. Inside the fluid container 9, a driving piston 20 is provided to separate the driving fluid and the injection fluid, thereby preventing intermixture of the two. The driving fluid displaces the driving piston 20 in the longitudinal direction 13 to squeeze the injection fluid contained in the fluid container 9 into the injection unit 10 through the check valve 106. The check valve is a dual check valve opening in a first direction at one excess pressure or over-pressure and opening in the direction opposite the first direction at another excess pressure. Hereby, the total volume of injection fluid is squeezed through the injection unit 10. When the injection fluid is sufficiently pressurised, the activation piston 40 is displaced in the longitudinal direction 13, thereby displacing the retainer sleeve 112. As the activation piston 40 is displaced through the pipe element 111, well fluid present in the pipe element 111 on the side of the activation piston 40 opposite the injection fluid is displaced out through the fluid openings 126. As the activation piston reaches the end of the pipe element 111, the retainer sleeve is fully displaced, and the expandable cups have been extended in the radial direction to provide an isolated zone 5b, as shown in
It is to be understood by those skilled in the art that the downhole injection tool according to an embodiment of the invention may also be inserted into the well without the use of a downhole tractor. Further, the downhole injection tool may be used as a wireline tool, as shown in
To be able to control when the expandable cups are extended and the injection fluid injected, the driving piston 20 and the activation piston 40 are provided with pressure-sensitive locking mechanisms 21, 41. The driving piston 20 shown in
For a similar purpose, the activation piston 40 shown in
a shows a retainer sleeve 112 comprising a first sleeve part 112a and a second sleeve part 112b movable in relation to one another. The first and the second sleeve part comprise a locking means 140 for releasably interconnecting the first and the second sleeve part, as shown in
The downhole injection tool 1 further comprises an ejection mechanism 30, partly shown in
During injection of the injection fluid, the driving piston 20 moves through the fluid container 9 to squeeze injection fluid into the injection unit 10. When the driving piston 20 has been pushed through the fluid container in the longitudinal direction and the fluid container is empty, the driving piston 20 engages with the piston sleeve 33 of the ejection mechanism 30, as shown in
The pressure of the injection fluid varies inside the tool during the filling and injection processes, respectively. Firstly, the injection fluid is filled into the container at an excess pressure of 1-5 bar, and secondly, the driving fluid is pumped into the injection tool to exert a force on driving piston locking mechanisms 21 that releases the driving piston at en excess pressure of 0.5-2 bar. Subsequently, the driving piston moves, thereby building up the pressure in the injection fluid until an excess pressure of maximum 4 bar is reached and the dual check valve opens, whereby the injection fluid passes the check valve. Then the pressure of the injection fluid inside the injection unit is increased and reaches an excess pressure of 5-8 bar, the activation piston locking mechanism 41 is released, and the activation piston 40 displacing the retainer sleeve is activated. Then, the injection fluid is injected into the annulus between the cups, and the pressure of the injection fluid drops substantially. The driving piston moves until the fluid container 9 is empty, and the pressure increases again until it reaches an excess pressure of 2-5 bar, whereupon the ejection mechanism 30 is released and the injection unit is released from the rest of the tool.
By the driving piston locking mechanisms 21, the activation piston locking mechanism 41 and the ejection mechanism 30 being released at 0.5-3 bar, 5-8 and 2-5 bar, respectively, it is secured that the various operating steps of the downhole injection tool are performed in the correct sequence. However, it is to be understood by those skilled in the art that various other combinations of the pressure of P1, P2, and P3 may be applied to achieve the desired effect of releasing the locking mechanism and the ejection mechanism in the prescribed sequence.
Referring to
In the above description, the fluid to be injected into the annulus has been referred to as the injection fluid, without regard to specific fluid properties. The downhole injection tool may be used for injecting various types of injection fluids, such as but not limited to cement slurry, an acid solution or a cleaning fluid.
If the downhole injection tool is used in combination with a cement slurry, the fluid container may be referred to as a cement bailer, and the injection unit may be used as a casting unit for casting a cement plug downhole. When casting a cement plug, the downhole injection tool 1 is operated in a manner similar to what has been described above. When the driving piston 20 has squeezed the cement slurry out of the fluid container or cement bailer, the injection unit is disengaged from the fluid container, and the casting unit is left downhole for the cement slurry to cure. When the cement slurry has cured, the injection unit is permanently fixed inside the borehole or well tubular structure, and a cement plug has been created. Depending on the material properties of the injection unit, the cement plug may subsequently be drilled away to re-establish a fluid passage past the cement plug.
Alternatively, the downhole injection tool may be used as a fluid treatment tool for exposing part of the well to a treatment fluid, such as an acid solution, cleaning fluid, etc. During such use, it may not be necessary to disengage the injection unit 10 from the fluid container 9, or the injection unit may be left inside the borehole or well tubular structure for shorter or longer periods of time. When operated as part of a fluid treatment tool, the injection unit may be referred to as a fluid treatment unit.
By expansion of the expandable cups is meant that each of the cups is expandable as a whole. The expandable cups may be constructed from parts not being individually expanded, but the design of the cups and the interconnected parts make the cups expandable as a whole. Expansion of the expandable cups may also be regarded as the expandable cups being unfolded.
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 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 tools are not submergible all the way into the casing, a downhole tractor can be used to push the tools all the way into position in the well. 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11183496.6 | Sep 2011 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/069088 | 9/27/2012 | WO | 00 | 3/31/2014 |
