Patent Application
20120125621
The present invention relates to a device that is used in connection with equipment, various types of work and operations carried out in connection with oil and/or gas wells onshore and offshore, and more particularly the present invention relates to a pressure-controlled device that is operated within a given pressure range.
Hydrocarbons, such as oil, gas and/or mixtures thereof, are normally found in accumulations under pressure in porous formations in a bedrock. These natural hydrocarbon reservoirs are exploited by drilling one or more boreholes into the bedrock. When these boreholes have been fully drilled and the well is in production, various processing installations that are located on or above the seabed will be able to process the hydrocarbons fully or partially.
However, there are hydrocarbon reservoirs where the natural flow of hydrocarbons to the surface is not sufficient to allow or maintain profitable production of the well. This may, for example, be due to the viscosity and/or weight of the hydrocarbons, or that the pressure in the oil well is too low to counter the hydrostatic pressure of the fluid in the well as well as the counter-pressure that the processing installations on the surface exert on the fluid in the oil and/or gas well.
The hydrocarbon reservoir may also, after being in production for some time, “lose” the pressure that is necessary to drive the hydrocarbons out of the reservoir, which will not make it profitable to operate the well any longer.
For such hydrocarbon reservoirs a number of systems and various principles have therefore been developed which are able to increase the production of the well with the aid of so-called artificial lifting. The two most common systems used today are water injection and gas injection. During gas injection gas is injected at high pressure into the annular space between the casing and the production tubing. As a rule, pressure-controlled valves, so-called injection or gas lift valves, are used to be able to supply and control or manage the amount of gas that flows into the actual production tubing.
Such gas lift valves may also be used during a start-up phase of a well, where completion fluid is found in both the well annulus and the production tubing. To start production in such a well, completion fluid that is in the annulus firstly must be displaced therefrom, through one or more gas lift valves, and up to the surface through the production tubing.
Similarly, a gas lift valve may, for example, be used after a well for various reasons has been shut down, with the result that a fluid fills at least parts of the annulus in the well, or that gas from a production fluid migrates to the surface, which may lead to the pressure in the well becoming too low to allow production therein to be resumed without the well being supplied with external pressure support, for example, pressure support by gas injection.
How these pressure-controlled valves are configured and arranged in the well will depend on a number of parameters. For example, according to the size (diameter) of the production tubing and the injection pressure available, so-called gas injection points will be provided at one or more locations in and along the production tubing, the specific configuration for each individual well thus being adapted for optimal gas injection. The pressure-operated valves, such as a gas lift valve, will then be installed at these gas injection points, at the same or different locations along the longitudinal direction of the production tubing with the purpose of being able to initiate gas injection, such that through this artificial “lifting” an optimal production of the well is obtained.
The gas lift valve(s) may then be operated or controlled according to a number of different principles, for example, by means of pressure, where there are pressure differences around and/or across the valve that effect the control of the valve(s), i.e., the opening and closing thereof.
One of the objects of the present invention is therefore to provide a device which is operated and/or controlled by pressure differences.
Another object of the present invention will be to provide a device that can be connected to an injection device and thus be used together with the injection device to operate and/or control the injection of a fluid into an oil and/or gas well.
Yet another object of the present invention will be to provide a device that operates within a predetermined pressure range.
These objects are attained by means of a device as disclosed in the following independent claim, with additional features of the invention set forth in the dependent claims and the description below.
A device according to the present invention is specifically intended to be used in connection with a start-up phase in an oil and/or gas well, in which well the whole or parts of the well annulus and production tubing are filled with, for example, a completion fluid. Before the production of the well can start up, the completion fluid that is in the annulus and/or production tubing must be displaced and replaced by an injection fluid, for example, a gas. Gas or nitrogen under high pressure, in a suitable manner, will then be pumped into the well annulus (the space between the well casing and the production tubing).
An optimal positioning of the various injection valves in such a well is identified using simulation tools for each individual well, the optimal configuration varying from well to well, depending on the specific parameters of the well. A different composition of well fluid during start-up will, moreover, mean that there is a need to have several levels of injection points in the well. However, when optimal production of the well has been achieved, there will only be a need for a (stimulation) injection point, this being located as far down in the reservoir as possible.
One or more pressure-operated valves, comprising the device according to the present invention, which are arranged in the longitudinal direction of the production tubing, will then, in the light of the simulation that has been conducted, be so-called “start-up units”, where these units are to be closed successively downwards in the well after the well has started up its production, so that the injection fluid is distributed downwards to the desired “start-up unit”.
When the pressure above such a “start-up unit” is great enough, it is opened and a throughflow of completion fluid through the unit is allowed, such that the completion fluid can flow from the annulus into the production tubing. The introduction of additional pressurised gas into the annulus will result in the completion fluid being displaced from the annulus and up through the production tubing. This process is repeated for each injection point downwards in the well. When the pressurised gas begins to flow into the production tubing, the well can start production from unit to unit until the main injection point is reached. It is then only this injection point that is in use. All the other initial units are closed.
The device according to the present invention can also conceivably be used when the well does not have sufficient pressure to drive the hydrocarbons up to the surface, or during a start-up of a well which has been temporarily shut down, where a fluid has filled up at least parts of the annulus and/or the production tubing, or where the production fluid has remained for some time in the annulus and/or the production tubing and where gas has migrated to the surface, the result being that pressure in the well is too low for the well to begin producing without receiving pressure support from gas injection.
It should be understood, however, that the device according to the present invention may also have other areas of use, for example, in connection with equipment that is used in an oil and/or gas well, equipment that is at the top of the process or that is located on the seabed.
The present invention relates to a device that comprises an outer structure. A bore is formed in the outer structure, which bore is delimited by an end surface that is arranged at one end of the outer structure. Thus, the outer structure will be closed at one of end thereof and open at an opposite end. One or more through holes are provided in an area close to the open end of the outer structure, which allows a fluid surrounding the device to flow into the device. The termination or edge of the outer structure may furthermore be configured with connecting means so as to allow the device to be coupled or connected to other equipment or tools, for example, a gas lift valve.
The outer structure of the device may be made in a single piece, or it may be composed of several substructures.
According to the present invention, a first and a second pressure-actuated bellows device are arranged in the longitudinal bore of the outer structure. Such a pressure-actuated bellows device, when seen in section in its longitudinal direction, may have a shape that may be oval, polygonal, curved, but preferably not circular, in order to obtain a simple compression or extension of the bellows device. This compression or extension is obtained by subjecting the pressure-actuated bellows device(s) to pressure conditions and/or reciprocal actuation.
The pressure-actuated bellows device may, for example, be made of a plurality of sections or lamellae which, when assembled, form the bellows device. It is also conceivable that the bellows device can be made by machining, moulding etc. Furthermore, the pressure-actuated bellows devices may be made of a metallic material, but they may also be made of a non-metallic material or of an elastomeric material. In some cases the pressure-actuated bellows devices may also be made of different materials.
The pressure-actuated bellows devices are further made hollow and they are delimited at one end by a flange or the like, whilst at their other end (open end) they are connected to a support means. How this connection is made and the structure of the connecting means is explained below.
The pressure-actuated bellows devices may further be designed to hold the same or different fluid volumes. This will mean that one of the pressure-actuated bellows devices will act on the second pressure-actuated bellows device in such a way that the second pressure-actuated bellows device is compressed/extended by the same or different length as the first pressure-actuated bellows device, that the “force” which is transmitted by the first and the second pressure-actuated bellows device is the same or different etc.
The foregoing means that the pressure-actuated bellows devices and the support means form a closed unit, which unit preferably is filled with an incompressible fluid.
When arranged in the outer structure, the first pressure-actuated bellows device will only be supported by the support means, whilst the second pressure-actuated bellows device will be supported by the support means at one end and a piston rod at the opposite end.
As the first and the second pressure-actuated bellows device are arranged in the longitudinal bore in the outer structure, the pressure-actuated bellows devices must have a radial extent (diameter) that is smaller than the radial extent (diameter) of the longitudinal bore, when seen in the longitudinal direction of the bore.
According to a preferred embodiment of the present invention, both the outer structure and the pressure-actuated bellows devices are configured with a circular cross-section, but they may have any suitable shape.
The first and the second pressure-actuated bellows device are further hydraulically connected to one another via the support means, which means that the pressure-actuated bellows devices will act mutually on one another in their axial direction. If, for example, the first pressure-actuated bellows device is actuated such that it is compressed, the compression will be “transmitted” via the support means so that the second pressure-actuated bellows device is extended a certain length. Similarly, actuation of the second pressure-actuated bellows device will result in the first pressure-actuated bellows device being extended or compressed, depending upon whether the first pressure-actuated device was compressed or extended. The incompressible fluid will then be “transmitted” from the one pressure-actuated bellows device to the other, this “transmission” between the pressure-actuated bellows devices thus being able to operate and control the opening and closing of the device.
The support means is suitably fixedly mounted internally in the outer structure. This may be done, for example, by welding, adhesive bonding, screwing etc. As the support means has a radial extent (diameter) that essentially corresponds to the radial extent (diameter) of the bore, the support means, the outer structure and the closed end of the outer structure will define a fluid-tight space, in which fluid-tight space the first pressure-actuated bellows device is arranged. The second pressure-actuated bellows device will then be arranged in the space that is defined by the support means, the outer structure and the open end of the outer structure.
The support means, according to a preferred embodiment of the invention, is configured as a hollow, closed cylinder, where in the top and bottom face of the closed cylinder, seen in the longitudinal direction of the cylinder, there is provided a through hole or opening. The first and the second pressure-actuated bellows device are then connected through their open end to the holes in the top and bottom face of the support means, such that the first and the second pressure-actuated bellows device together with the support means form a closed unit.
In a preferred embodiment of the invention, the cavity that is defined by the first pressure-actuated bellows device, the support means and the second pressure-actuated bellows device is preferably filled with an incompressible fluid.
According to one embodiment of the invention, a “floating” piston may be provided in the support means, the piston being allowed to move in the axial direction of the support means when one or both of the pressure-actuated bellows devices are subjected to an external force. The piston has a radial extent (diameter) which is essentially the same radial extent as the inner surface of the support means. When the piston comes into contact with the top or bottom face of the support means, the piston will not move further, thereby also stopping the movement of the pressure-actuated bellows devices.
In another embodiment of the present invention, a delay device may be provided in the support means, this delay device having the purpose of delaying the flow of the incompressible fluid into the closed unit. In its simplest form, this delay device may comprise a plate that is configured with one or more through holes. The plate is suitably fastened internally in the support means.
Since through the invention it is desired to provide a device which operates within a predefined pressure range, the pressure-actuated bellows devices are supported internally in the longitudinal housing bore in such a way that the support means per se forms a limitation (end stop) for the movement that respectively the first and the second pressure-actuated bellows device are permitted to make. This means that if the first pressure-actuated bellows device is subjected to pressure which results in it being compressed in its axial direction, the support means, i.e., the end stop, will prevent a further extension of the second pressure-actuated bellows device. Similarly, the second pressure-actuated bellows device, when the pressure surrounding it increases, will only be allowed a certain displacement in its axial direction before its movement is stopped by the end stop, whereby also the first pressure-actuated bellows device is prevented from being further extended.
In an alternative embodiment, the end stop may be a sleeve which is preferably arranged on the inside of the support means, the sleeve then extending outwards from the support means and some length into the axial direction of the pressure-actuated bellows device. The end stop may be arranged in each of the pressure-actuated bellows devices, or only in one of them. However, it should be understood that the sleeve can also be arranged on the outside of the pressure-actuated bellows device, and in that case the sleeve can be connected to the support means.
The end stop may also be constituted of a flange or the like that is arranged internally in the outer structure.
In a preferred embodiment of the present invention one or both of the pressure-actuated bellows devices may be so configured that when a desired compression of the pressure-actuated bellows device has obtained, the pressure-actuated bellows device will essentially be compressed so that a further compression thereof is not obtainable. This means that the pressure-actuated bellows device in its maximum compressed position will act as a solid, rigid element, which gives the pressure-actuated bellows device substantial mechanical strength and resistance to pressure.
By introducing a fluid into the fluid-tight space in which the first pressure-actuated bellows device is located, i.e., the fluid-tight space defined by the outer structure, the support means and the closed end of the outer structure, and subsequently pressurizing it with a specific pressure, which results in the first pressure-actuated bellows device being subjected to a preset pressure, the first pressure-actuated bellows device will be actuated by the preset pressure and compressed against the support means. The first pressure-actuated bellows device will then be fully compressed, i.e., that it assumes the position of a solid rigid element, which cannot be compressed further. This compression of the first pressure-actuated bellows device will then result in the second pressure-actuated bellows device being extended a length, with the effect that the second pressure-actuated bellows device, which via a piston rod or the like is connected to a valve body, will force the valve body into contact with a valve seat, which results in the device being held in a shut or closed position. In this situation, the second pressure-actuated bellows device is actuated by the first pressure-actuated bellows device only.
To introduce a fluid into the fluid-tight space defined by the outer structure, the closed end of the outer structure and the support means, a through hole may be provided in the outer structure, to which hole, for example, a non-return valve may be connected.
Subsequently, the device may, for example, be connected to a gas lift valve, and then lowered into the well so as to then be arranged in a production tubing.
When the device and the attached gas lift valve are arranged in the production tubing, the second pressure-actuated bellows device, which is arranged in the space defined by the support means, the outer structure and the open end of the outer structure, will be subjected to an external force (in addition to the force from the first pressure-actuated bellows device), for example, from a pressure of a fluid in the well annulus. If the pressure in the fluid that is in the well annulus is less than the preset pressure by which the first pressure-actuated bellows device is actuated of the device will remain in its shut or closed position. By pressurizing a fluid and adding it to the fluid that is in the well annulus, the pressure in the well annulus can be increased until this pressure is as great as the pressure in the fluid-tight space. The pressure to which the first and the second pressure-actuated device are subjected will then be equalized, which will result in the second pressure-actuated bellows device being compressed slightly (and the first pressure-actuated bellows device being extended as a result), whereby this compression will cause the valve body to be lifted out of engagement with the valve seat. The device is now in its working position, and the surrounding fluid (the fluid in the annulus) is then allowed to flow through the device and into the gas lift valve, whereby this also is actuated to be opened. The fluid that is in the well annulus can now, via the device and the gas lift valve, flow from the annulus and into the production tubing, so that, for example, completion fluid is displaced from the annulus.
The transmission of the axial movement between the first and the second pressure-actuated bellows device may, however, also take place in other ways than by the first pressure-actuated bellows device being subjected to a fluid pressure, for example, by mechanical transmission. A person skilled in the art will know how this may be done.
It is also conceivable that the first and the second pressure-actuated bellows device can be filled with a fluid such that they have the same pressure, or that the pressure in the two pressure-actuated bellows devices may be different. This will give a better possibility of controlling the range of movement of the pressure-actuated bellows devices.
In a preferred embodiment of the present invention, the first and/or the second pressure-actuated bellows device may be configured so as to be capable of being filled with or emptied of the fluid it contains, thereby allowing the pressure and/or the fluid it contains to be varied/replaced.
In the volume defined by the bore in the outer housing and the pressure-actuated bellows device itself, one of the solutions according to the present invention may be that around each pressure-actuated bellows device there is provided a nitrogen package (or another gas) that is pressurised, where the nitrogen package forms a bias that must be overcome if the pressure-actuated devices is to capable of being actuated. The nitrogen package may be configured as a hollow, closed cylinder that is arranged around the pressure-actuated bellows device, or it may consist of several individual packages that are distributed around the outer periphery of the pressure-actuated bellows device. Alternatively, the nitrogen package can be replaced by, for instance, disc springs or similar resilient devices. The nitrogen packages or the resilient devices for each of the pressure-actuated bellows elements may have the same or different resilience (modulus of elasticity).
The second pressure-actuated bellows device may be connected to a piston rod or the like, which piston rod is further connected directly or indirectly to a valve body. Upon reciprocal actuation of the first and the second pressure-actuated bellows device, the valve body will be lifted out of or brought into contact with a valve seat, thereby opening or closing the device for through flow of a fluid.
If the second pressure-actuated bellows device is connected directly to the valve body via a piston rod, there will be a direct linear transmission of the movement of the second pressure-actuated bellows device to the valve body. In one embodiment of the invention, the device may comprise two valve seats, between which the valve body is disposed, so that the device can be held closed when there is “equilibrium” between the two pressure-actuated bellows devices, or that the device is held closed in that the external pressure (which surrounds the second pressure-actuated bellows device) is greater than the preset pressure that surrounds the first pressure-actuated bellows device.
It is also conceivable that the second pressure-actuated bellows device is connected via a piston rod to two sub-pistons, which two sub-pistons are connected to each other through a hinge device. In one embodiment, the hinge device comprises a rotational axis, where the linear movement of the second pressure-actuated bellows device through the rotational axis is transmitted to the two sub-pistons. The rotational axis of the hinge device, in one embodiment, may be substantially transverse to the longitudinal axis of the device. In another embodiment, it may intersect the longitudinal axis or be arranged eccentrically in the device. A rotational axis is also conceivable that is not transverse, but that forms another angle to the longitudinal axis of the device. In one embodiment, the hinge device may comprise a pivot pin arranged to rotate about its own longitudinal axis, which thus forms the rotational axis of the hinge device. The pivot pin is arranged to rotate relative to the outer structure and further comprises two engaging portions on either side of the pivot pin, which engaging portions are in engagement with a recess in their respective sub-piston.
The first and the second sub-piston may have a form that allows it to slide in the outer structure without any hindrance to the movement of the sub-pistons. In one embodiment, one sub-piston, in a portion at one end thereof facing away from the other sub-piston, may be so configured that it fills the whole of the inner cross-section of the bore in the outer structure, whilst at the opposite end facing the second sub-piston it may be configured so as to fill only a part of the cross-section of the bore. This allows the second sub-piston to fill a part of the same inner cross-section. The second sub-piston, in one embodiment, may be connected to a valve body by a connecting rod or piston, so that the valve body may be arranged at a distance from the portion of the second sub-piston that substantially fills the whole of the inner cross-section of the bore in the outer structure. The sub-pistons fill the inner cross-section of the outer structure, but there is nonetheless fluid communication across the sub-pistons. This can also be obtained by configuring the sub-pistons with recesses in the surfaces on top of the sub-pistons and/or in an interior surface of the outer structure.
In an alternative embodiment of the present invention, the second pressure-actuated bellows device, via a piston rod, is directly connected to an inner movable body in, for example, a gas lift valve, whereby the piston rod, when actuated by the second pressure-actuated bellows device, will displace the inner movable body in the axial direction of the gas lift valve, thereby opening the gas lift valve.
The device according to the present invention may also comprise locking and sensor means, which locking means will be able to lock the device in a desired position (open or closed). The device will remain in the locked position until the locking means is actuated to be opened, this taking place, for instance, after the sensor means has measured a certain surrounding pressure. The locking means may, for example, be electric, electromagnetic, etc.
Other advantages and characteristic features of the present invention will be clearly apparent from the following detailed description, the appended figures and the following claims.
The invention will now be described in more detail with reference to the following figures, wherein:
The figures show different embodiments of the device according to the present invention, where the device connected to other equipment is, for example, intended to be arranged in a production tubing in an oil and/or gas well. One of skill in the art will appreciate how this is done and it is therefore not described in the description.
In the outer structure 1 there is further provided a first and a second pressure-actuated bellows device 3, 4.
The first and the second pressure-actuated bellows device 3, 4 are configured as a bellows in the form of an “accordion”, where a plurality of sections or lamellae 6 are assembled to form the actual bellows. This may be done, for example, by welding, adhesive bonding or in some other suitable way connecting the sections or lamellae 6 to each other.
The two pressure-actuated bellows devices 3, 4 are interconnected via a support means 5. The outer section 6 (i.e., the end section) at one end of the pressure-actuated bellows devices 3, 4 is thus welded, adhesively bonded or in some other manner connected to its respective side of the support means 5. The support means 5 is in turn fixedly mounted to the inside of the bore 2. This may be done, for example, by welding, adhesive bonding, screwing or some other suitable manner.
The second pressure-actuated bellows device 4, like the first pressure-actuated bellows device 3, is at its other end (i.e., the end opposite the connection to the support means 5) connected to a flange 9. The flange 9 is further configured with a hole internally and with at least one through hole 10 at one of its ends, which allows the second pressure-actuated bellows device 4 to be connected via the flange to a piston rod 12. The piston rod 12 is then fastened to the flange 9 by means of a cotter pin, screw etc. (not shown) through the hole 10.
As the support means 5 is fixedly mounted on the inside of the bore 2, the support means 5 will form a fluid tight partition internally in the outer structure between the first and the second pressure-actuated bellows device 3, 4. This means that a closed space 11 is formed, which closed space 11 encircles the first pressure-actuated bellows device 3. This closed space 11 is filled with a fluid, for example, nitrogen under pressure, which means that the first pressure-actuated bellows is subjected to a desired “bias”. This bias will, depending upon its size, actuate the first pressure-actuated bellows device 3, so that it is compressed. The closed space 11 is filled in that in the outer structure there is provided a through hole (not shown), to which, for example, a non-return valve is connected.
However, it is also conceivable that the first pressure-actuated bellows device 3 can be actuated by an actuating mechanism (not shown), thereby making it unnecessary to preset the closed space 11 at a pressure. The actuating mechanism may then be so configured that it transmits or applies a force to the first pressure-actuated device 3 such that it is compressed or extended in its axial direction. The actuating mechanism may, for example, be so configured that it is activated electrically, hydraulically etc.
Similarly, a space will also be formed around the second pressure-actuated bellows device 4, which space is defined by the support means 5, the outer structure 1 and the open end of the outer structure. The second pressure-actuated bellows device 4 will then also be subjected to an external force, for example, from a pressure in a fluid in the well annulus.
Each of the pressure-actuated bellows devices 3, 4 is made hollow and holds an incompressible fluid, and the bellow devices 3, 4 must thus be configured as a closed unit. This can be done in different ways, for example, in that one end of the pressure-actuated devices 3, 4 is connected to the support means 5, whilst the opposite end is delimited by the flange 7, 9.
The support means 5 according to
Internally in the support means 5 there is further provided a movable piston 101 (see also
A sleeve 104 may further be provided internally in the support means 5, which sleeve will extend some distance inwards in the closed space of the first and/or the second pressure-actuated bellows device 3, 4. This will allow the first and/or the second pressure-actuated bellows device 3, 4 to be extended or compressed until the pressure-actuated bellows device 3, 4 is brought into contact with the sleeve 104, whereby further extension or compression of the pressure-actuated bellows device 3, 4 is stopped.
In the support means 5 there may also be provided a delay device 102, the purpose of said delay device 102 being to delay the flow of the incompressible fluid into the support 5. In its simplest form, the delay device 102 comprises a plate formed having one or more through holes 103. The delay means 102 is supported in a suitable way in the support means 5.
A second embodiment of the device according to the present invention is shown in
The first sub-piston 17 comprises a first end portion 27, which comprises the contact face 28. This first end portion 27 is shown so that a cross-section of this end portion 27 fills almost the whole bore 2 of the outer structure 1. Furthermore, the first sub-piston 17 comprises a second end portion 29 which faces away from the first end portion 27, which second end portion 29 fills only a part of the bore 2 of the outer structure 1. This second end portion 29 is also connected to a hinge device 18 comprising a pivot pin 30 and a first engaging portion 31 which rests in a recess 32 in the second end portion 29 of the first sub-piston 17. The hinge device 18 further comprises a second engaging portion 33 which extends from the pivot pin 30 on the opposite side relative to the first engaging portion 32. This second engaging portion 33 rests in a recess 34 in a second end portion 38 of a second sub-piston 19. The motion of the first sub-piston 17 is transmitted to the second sub-piston 19 through the hinge device 18, whereby the second sub-piston 19 will be moved in the opposite direction to the movement of the first sub-piston 17. The movement takes place essentially in an axial direction of the device. The second end portion 38 of the second sub-piston 19 also has a smaller cross-sectional extent than the bore 2 in the outer structure 1, so that there is room for the hinge device 18 and the movement of the sub-pistons 17, 19. A first end portion 39 of the second sub-piston 19, which faces way from the first sub-piston 17, covers essentially the whole cross-section of the bore 2 in the outer structure 1. To the end of this first end portion 39 there is connected a piston rod 12 to which the valve body 13 is secured. A movement of the second sub-piston 19 will thus move the valve body 13 relative to the valve seat 14. The device according to this embodiment will be closed or opened in the same way as described above.
Only elements relating to the invention have been explained and described above and a person of skill in the art will appreciate that the outer structure can be formed as one unit or it may comprise several elements that are joined together. The valve device should further have suitable means for connection or installation in a process fluid stream. The skilled person will further understand that a number of embodiments and modifications of the described and illustrated embodiment can be provided within the scope of the invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20084969 | Nov 2008 | NO | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NO2009/000406 | 11/25/2009 | WO | 00 | 6/27/2011 |
