Well Barrier
A well barrier is for sealing off a first portion of a wellbore from a second portion of the wellbore, the first portion having a higher fluid pressure than the second portion. The well barrier is held in place in the wellbore by a holding means. The well barrier is preshaped to disintegrate in at least three barrier elements upon activation of a disintegration means, at least one of the barrier elements having a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore. A method is for controlling a disintegration of the well barrier.
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This invention relates to a barrier. More particularly it relates to a well barrier and/or zone isolation devices for sealing off a first portion of a wellbore from a second portion of the wellbore in wells related to the production of hydrocarbons.
In conjunction with the completion of wells, involving steps such as the installation of production casing, production liner (lower completion) and production tubing (upper completion), barrier systems are commonly used.
In one scenario, a barrier is mounted in top of the lower completion (production liner), to isolate the reservoir whilst installing the production tubing (upper completion) in the upper section of the well.
In another scenario, a barrier is installed in the bottom of the production tubing during the installation of this. Once the tubing is positioned correctly, pressure is applied on the inside to set the production packer. To form a sealed enclosure during such operation, to allow for pressurizing the internals of the tubing, the bottom of the tubing has to be sealed off. Most commonly, such seal is provided for by using a barrier device.
A common requirement to the above described barrier systems is the ability to withhold the required pressure during the stages where such barrier functionality is required. A second, equally important requirement is that the barrier can be opened or removed when barrier functionality is no longer required, to open the liner and/or production tubular so that fluids can flow through it.
Traditionally, these temporary completion barriers were installed and retrieved using well service techniques such as wireline or coil tubing.
In many offshore fields, very costly drilling rigs are utilized for the purpose of drilling and completing a well. In such cases, any time spent on wireline or coil tubing operations will contribute to making the completion of the well increasingly expensive, as it increases the time the drilling rig has to be rented for the completion of the well. To eliminate the need to operate the above mentioned barrier systems on wireline or coil tubing, barriers that can be operated to open without the need for physical intervention into the well have been developed. Initial systems of such kind were ball valves, flapper valves, sliding sleeves or similar that was operated open by cycling well pressure using a pump at the surface of the well.
Cycling pressure means repeated pressurizing and depressurizing (bleeding down) the tubing (and/or liner top) pressure in order to operate mechanical counter systems associated with the downhole barrier. Typically, after a certain amount of pressure cycles, the mechanical counter system will engage with a barrier activation mechanism that causes the barrier/valve to open. Typically, such engagement is achieved by the counter mechanism ultimately operating a valve member of the activation system, that allows well pressure to work against an atmospheric chamber via a piston, and the resulting work is used to shift the valve member to an open position. In other versions, such engagement is achieved by the counter mechanism ultimately operating a mechanical lock of the activation system that releases a pre-tensioned spring mechanism in the activation mechanism, whereupon this causes the valve member to shift to an open position. Other similar methods of activating and shifting the valve member may be applied. Such methods would be appreciated by a person skilled in the art, and are not described further herein.
A drawback with barriers made of metal, such as the barrier systems described in the previous section, is that if the cycle open mechanism or activation mechanism fails to operate, or if the valve element fails to shift open for any other reason, alternatives for mechanical removal of the barrier are associated with a relatively high cost and risk. An example of alternative removal is to use coil tubing to shift open, or in the worst case mill out a ball valve or a steel flapper valve.
Typical causes of failure may be debris in the well that jams the cycle open mechanism, the activation mechanism or the valve element itself.
Other related barrier systems are made of non-metallic materials such as for example glass, ceramics, salt or other more brittle materials. A common method for barrier removal in this respect is a mechanical cycle open mechanism that triggers an activation mechanism where an explosive charge is detonated inside or in close proximity to the brittle barrier. An alternative method entails the mechanical cycle open mechanism to operate a mechanical lock that holds a pre-tensioned spring system. When releasing the pre-tensioned spring, this will drive an impact device such as a spear into the brittle barrier to crush it.
A great benefit with using brittle, non-metallic barrier elements is that they are easier to remove mechanically than steel barriers should the mechanical cycle open method of activation fail for any reason. Rather than having to use coil tubing to mill out a steel barrier, wireline could be used, together with a spear, hammer device or other device or combination of devices to crush the barrier. Thus, a quicker, more cost effective backup activation is possible.
Publication US 2003000710 A1 discloses a downhole non-metallic sealing element system related to downhole tools such as bridge plugs, frac-plugs, and packers having a non-metallic sealing element system for isolation of formation or leaks within a wellbore casing or multiple production zones.
Publication US 2009283279 A1 discloses a zonal isolation system for use in a well. The zonal isolation system includes a zonal isolation tool, at least one anchor, and at least one polished bore receptacle. The zonal isolation system includes a setting string for activation of the zonal isolation tool and/or the at least one anchor. It may also include an isolation string for maintaining separation zones during production or injection of the well.
Publication US 2002195739 A1 discloses to a method of manufacturing a sealing or an anti-extrusion component for use in a downhole tool. The component is formed from a composition that contains a polyetherketoneketone or a derivative of a polyetherketoneketone.
Publication US 2009151958 A1 discloses a method and device for temporary well zone isolation. In particular, it discloses temporary well zone isolation devices with frangible barrier elements and methods for the disintegration of frangible barrier elements.
Publication GB 2391566 A discloses a formation isolation valve for use in a subterranean well. A mechanical apparatus may be used to open and close the valve. The actuators may include a rupture disc or other forms of remotely operable actuator.
U.S. Pat. No. 6,167,963 B1 discloses a drillable composite packer or bridge plug including substantially all nonmetallic components.
U.S. Pat. No. 6,796,376 B2 discloses a composite bridge plug system for containing a well bore with reduced drill up time.
A generic problem with barriers made of brittle materials is that impact or a large force is required to crush them. In the case where explosives are used, this may entail a potential safety risk. Requirements to create mechanical impact and/or a large force in an activation system make it somewhat more complex and susceptible to failure. The presence of debris/impurities in the well may impair the performance to the extent where the opening/removal activation fails.
Still another method for removing a barrier made of a brittle material is to disintegrate the barrier by means of fluid pressure. WO 2009126049 discloses a plug element for conducting tests of a well, a pipe or the like, comprising one or more plug bodies of disintegratable/crushable material set up to be ruptured by internally applied effects. The plug comprises an internal hollow space set up to fluid communicate with an external pressure providing body, and the plug is designed to be blown apart by the supply of a fluid to the internal hollow space so that the pressure in the hollow space exceeds an external pressure to a level at which the plug is blown apart.
However, brittle material barriers that are crushed by the means mentioned above, may give rise to another problem. In some cases, despite crackling the brittle barrier, the specific well situation (local pressure, fluids, compacted debris surrounding the barrier) may prevent the particles from physically being removed to any significant distance from their original position. As a result, the crackled (but not physically disintegrated) barrier may still represent a relatively solid body in the well, preventing flow, hence obstructing for subsequent operational steps. Ultimately, such crackled barriers may have to be physically removed by wireline or coil tubing interventions as described above.
The object of the invention is to remedy or reduce at least one of the drawbacks of prior art.
The object is achieved in accordance with the invention, by the characteristics stated in the description below and in the following claims.
According to a first aspect of the present invention there is provided a well barrier for sealing off a first portion of a wellbore from a second portion of the wellbore, the first portion having a higher fluid pressure than the second portion, wherein the well barrier is held in place in the wellbore by a holding means preventing movement of the well barrier in a direction from the first portion to the second portion, the well barrier comprising:
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- multiple barrier elements initially held together by a connection means to form the barrier, the barrier having a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore;
- a sealing means for preventing fluid flow from the first portion to the second portion;
- a destabilizing mechanism arranged for disengaging the connection means from at least one of the barrier elements upon activation of the mechanism, so that support between adjoining barrier elements is removed, thereby disintegrating the well barrier.
This has the effect that the shape and form of the individual barrier elements after disintegration of the barrier can be controlled so that the likelihood for the barrier elements creating problems after disintegration is minimized. Further, providing a preshape wherein at least one of the barrier elements having a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore may provide a well barrier that is capable of carrying a high fluid pressure in the first portion, but very vulnerable to fluid pressure in the second portion of the wellbore.
In one embodiment of the present invention the multiple barrier elements are formed in one piece provided with notches in at least a portion of the surface of the well barrier, and the connection means comprises the non-notched portion of the well barrier.
In one embodiment of the present invention the barrier elements are provided by means of separate, preshaped barrier elements being connected to each other by the connection means, the connection means being selected from one of or a combination of: an adhesive; a wire; the sealing means, to form the well barrier.
In one embodiment of the present invention the preshape may be provided by means of a combination of one or more portions of the barrier being provided by notches and one or more portions of the barrier being provided by separate, preshaped barrier elements.
The well barrier may further be provided with a support element for supporting the barrier elements. Preferably, the support element faces the second portion of the wellbore.
The sealing means may be a sealing element. Preferably, the sealing element faces the first portion of the wellbore. The sealing element is selected from a material suitable for providing an impermeable barrier between the fluid in the wellbore and the barrier elements. In one embodiment the sealing element is selected from the group comprising an elastomeric membrane, a coating, an adhesive.
In one embodiment the sealing means is the non-notched portion of the well barrier.
Preferably, the well barrier has the form of a pressure arch towards the first portion of the wellbore.
In one embodiment the well barrier is provided with a further well barrier, the further well barrier being mirrored with respect to the well barrier about a plane being perpendicular to a longitudinal axis of the well bore. The second portion of the wellbore is in this embodiment defined between said well barrier and said further well barrier.
In one embodiment of the present invention the destabilizing mechanism comprises a releasable holding means arranged such that upon releasing the holding means the well barrier is moved by the fluid in the first portion, the movement causing the well barrier to disintegrate.
In one embodiment of the present invention when the second portion is defined between the well barrier and the further well barrier, the destabilizing mechanism is an arrangement for raising the pressure of the fluid in the second portion to a level higher than the fluid pressure in the first portion of the wellbore facing the further well barrier
At least one of the multiple barrier elements may have a form as a keystone supporting adjoining barrier elements, the keystone element having a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore. The at least one keystone element may be provided by means of multiple elements.
The barrier facing the first portion of the wellbore may have a concave lens shape, wherein a majority of the barrier elements are wedge shaped with a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore.
In a second aspect of the present invention there is provided a method for controlling a disintegration of a well barrier according to the first aspect of the invention, the method comprising:
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- pre-shaping the barrier to disintegrate in multiple barrier elements of desired size and shape; and
- activating a destabilizing mechanism that will provide a force sufficient to break a connection means initially holding the multiple barrier elements together, thereby causing the barrier to disintegrate into said multiple barrier elements of desired size and shape.
The following describes a non-limiting example of a preferred embodiment illustrated in the accompanying drawings, in which:
The upper completion comprises the production tubing 106, which is stung into the lower completion by means of a seal stinger assembly 107. A sealing arrangement 108 comprising a barrier 114 according to the present invention is installed below a production packer 109. In the top of the well, the tubing 106 is terminated in the wellhead 110. The completion design may vary significantly from what is shown in
When running the completion in the hole, the production packer 109 is not activated, as illustrated in
The centerline 115 of the tubular is illustrated for reference.
Now considering
To remove the barrier 114, the fluid inside the tubing 106 is pressure-cycled as described earlier in this document, using the pump 111. For each complete pressure cycle, a mechanical counter mechanism 112 is operated one step. After a certain amounts of steps, the mechanical counter mechanism 112 will interact with an activation module 113 that triggers the opening and/or removal of the barrier 114. In summary, after a certain amount of cycles, i.e. pressurizing and de-pressurizing the tubing fluid, the barrier 114 opens.
The mechanical counter system 112 and activation system 113 could be replaced or supplemented by alternative activation systems, such as battery operated, sensor based or timer based activation systems, controlled by internal micro controllers or similar available in the marked. Details of such associated activation mechanisms would be appreciated by a person skilled in the art and no further details of such are provided for herein.
In a preferred embodiment, upon activation, a mechanical counter system 112 as indicated in
The barrier 114 shown in
In an alternative embodiment, the barrier 114 is constituted by one element provided with notches providing nicking of the barrier 114 into barrier elements 114a, 114b, 114k of a desired, predetermined size.
The barrier 114 is locked in place inside the tubular of the activation system 113 by means of a finger coupling 207 and a lock/cover sleeve 208.
Upon activation, pressurized fluid is routed from a valve manifold operated as described elsewhere in the document and into the activation system 113 via channel 201. Here, the pressurized fluid acts on piston 202. The piston 202 is mechanically in contact with holding profile 204 via piston mandrel 203. Longitudinal slots 205 are provided in the piston mandrel 203. A set of engagement bolts 209 are screwed into the lock/cover sleeve 208, the engagement bolts 209 protruding through the slots 205 of the piston mandrel 203.
In one embodiment, the smaller elements 14a, 14b, 114k are free to move with respect to each other, but form a mechanically stable geometry when mounted as shown in
Thus, there is provided a well sealing arrangement 108 where the force integrity is provided by at least one barrier 114 associated with at least one activation system 113 that includes at least one operable support element 207, wherein said barrier 114 is construed by smaller barrier elements 114a, 114b, 114k that form a stable mechanical structure against forces from at least one side of the sealing arrangement 108; and said stable mechanical structure becomes unstable by means of operating at least one support element 207.
Thus there is provided well sealing arrangement 108 where the force integrity is provided by at least one barrier 114 associated with at least one activation system 113, wherein said barrier 114 is construed by smaller barrier elements 114a, 114b, 114k that form a stable mechanical structure against forces from at least one side of the sealing element 108, said stable mechanical structure becomes unstable by means of operating the activation system 113.
To ensure pressure integrity and not only force integrity, the barrier 114 is in the embodiment shown provided with an elastomeric membrane 212. In other embodiments, the elastomeric membrane 212 could be replaced with other coating agents suitable for forming a seal. Such a coating agent may be adhesives, resin coating or similar.
Now consider
Now consider
Still considering
As would be appreciated by a person skilled in the art, a barrier element of the kind illustrated herein as barrier 114 is designed to withstand a larger forces from the direction illustrated by arrow 210 than in the opposite direction (from below in the embodiment illustrated.
In another embodiment of the invention, barrier 601 may be activated by a similar activation system and method as described in relation to
In one embodiment of the present invention, the lower of the two barriers, i.e. barrier 601 is the one that is operated by the activation system 113 as discussed above. This means that the barrier system disclosed in
In even another embodiment of the invention, barriers 114 and 601 are operated simultaneously when activating the activation system 113.
In one embodiment of the present invention barriers 114 and 601 are fully or partially merged into one structural element with a cavity inside of it.
In all embodiments exemplified in
In one embodiment, vacuum is applied to the cavity between barrier 114 and 601, to ensure that pressure forces keep the barriers in place and intact while handling them on the surface, with atmospheric pressure in the surroundings.
In one embodiment, the activation system 113 does not comprise the finger coupling 207 and associated mechanisms. Instead, the barriers 114 and 601 are removed by leading high pressure into the cavity there between, either sourced from a location above barrier 114 or below barrier 601, or on the radial outside of thereof or from a pressurized fluid reservoir that forms part of the installed downhole assembly. One such activation system is known from the publication WO 2009126049.
In one embodiment, disintegration of the barrier according to the present invention is achieved by leading high pressure fluid into the cavity between the barriers 114, 601 as shown, in combination with removal of mechanical support of one or more barrier.
In one embodiment, the elastomeric membrane 212 will hold the barrier 114 mechanically stable by means of mechanical forces/mechanical rigidity associated with membrane 212 (similar considerations applying for barrier 601).
In one embodiment, the cycle open system 112 and/or activation system 113 are incorporated in one or all of the barriers 114, 601, and/or smaller barrier elements 114a, 114b, 114k.
In the following figures, for simplicity, the inner parts of the cut activation system are not shown.
Now consider
In a preferred embodiment, should the main (cycle open) barrier removal/disintegration method fail to operate, a cutting device will be deployed on wireline or coil tubing and applied to cut through the membrane 212. By means, this will entail that the upper barrier 114 will leak, and this will cause pressure to act on top of barrier 601 so that this disintegrates (as it is not designed to hold pressure from that direction). By subsequently bleeding off pressure above barrier 114, this will disintegrate, too, for similar reasons, as the higher reservoir pressure will act on it in the reverse direction. In some embodiments, the membrane 212 is mechanically protected or double barriers are applied (as described in relation to
Now consider
In one embodiment, both the upper support shoulder 806 and lower support shoulder 805 are operable. For example, both shoulders 806, 805 could be operable in a longitudinal direction of the well as indicated by arrow 808. For this embodiment, it is preferred that the upper support shoulder 806 has a longer permitted distance of movement than the lower support shoulder 806, so that the support shoulders does not re-establish in a fully supporting modus with respect to barrier 114. For this embodiment, as the lower support shoulder 805 is permitted to travel a certain longitudinal distance before landing on a dedicated stop profile, a shock force will be applied on the barrier 114 in addition to the static fluid pressure forces. In one embodiment, such shock force will help deforming and/or partly disintegrating the barrier 114 in the area where this is in contact with lower support shoulder 805.
In the embodiment shown in
In one embodiment of the invention, the cavity 902 is filled with a vacuumed fluid, which may for example be inserted in combination with a small gas pocket. The gas pocket is intended to compensate for temperature derived fluid expansion inside cavity 902 as the system is lowered into the hot well climate. Such temperature expansion could, if not compensated for, cause barriers 114, 601 to leak and malfunction. In another embodiment, said temperature expansion is compensated for by allowing for a compensating travel of piston 905.
In one embodiment of the invention, the system is prepared for installation in the well by pushing the piston 905 to a position where the spring 906 is compressed whilst filling cavity 902 with said fluid and/or fluid/gas mixture. After filling the cavity 902 and closing the fill port (not shown in the drawing), piston 905 is released so that the spring 906 pushes it upwards. By means, a pressure that is lower than the surrounding (atmospheric) pressure is created inside the cavity 902. This may assist keeping the barrier elements 114,601 more stable during assembly and intervention into the well, as the elastomeric membrane will be subject to suction forces from the inside of the barrier.
Now consider
In the embodiment shown, the lens-shaped barrier 114 is provided with cuts running from the point 1501, the cuts being symmetrical with respect to the center line axis 115 of the wellbore/tubular. In one embodiment, two sets of cuts such as the illustrated cuts are made perpendicular (or in any desired angle) to each other with respect to the xy plane. As a result, the smaller elements 114a, 114b will assume a wedge shaped form with a cubic base along the outskirts of barrier 114, whereas the form will be a concave cubic/rectangular shape in the center of the lens.
In a preferred embodiment, the smaller elements 114a, 114b, 114c, 114k are made by providing circular cuts that are concentric with the circumference of the barrier 114, the cuts being made along lines that resemble the lines running out of point 1501. Subsequently, radial cuts are made from the outskirts of the barrier 114 towards the centre. In one embodiment, the entire barrier is cut by the said radial cuts all the way from the outskirts to centre. In another embodiment, the centre barrier element 114k, the “key stone”, is not cut. Hence, the barrier elements 114a, 114b, 114c will be formed from concentric and radial cut intersections, with the exception of the key stone barrier element 114k that will have a substantially frustoconical shape wherein the surface area facing the first portion of the wellbore is larger than the surface area facing the second portion of the wellbore. This is clearly shown in
The barrier elements 114a, 114b, 114c, 114k will in the embodiment shown resemble building blocks of an igloo; however the blocks along the circumference of the “lens” will be supported by an angled base rather than a horizontal base.
In one embodiment, the barrier 114 will be constituted by barrier elements 114a, 114b, 114c, 114k defined by cuts that run all the way from the top/outer end to the bottom/inner end of the barrier. In another embodiment, layered sub elements (not shown) that are constituted by smaller barrier elements 114a, 114b, 114c, possibly with thin walled dome elements (similar to the dome element 114s shown for example in
In a preferred embodiment the smaller elements 114a, 114b are molded elements, made of fibre armed concrete or other rugged materials suitable for molding, able to withstand the required forces. In another embodiment, the smaller elements 114a, 114b, 114c, 114k are machined or manufactured in alternative known fashions. Preferably, the barrier elements are made of a material having a higher density than that of the fluid in the wellbore. This to ensure that the disintegrated barrier elements sink down in the well and do not represent any risk for malfunction of e.g. any valves arranged downstream of the sealing arrangement 108 arranged in a producing well. However, the barrier elements may also be made of a material having a lower density than that of the fluid in the wellbore, if it is desired to prevent the disintegrated barrier elements to sinking in the well.
Claims
1. A well barrier for sealing off a first portion of a wellbore from a second portion of the wellbore, the first portion having a higher fluid pressure than the second portion, wherein the well barrier is held in place in the wellbore by a holding means preventing movement of the well barrier in a direction from the first portion to the second portion, the well barrier comprising:
- multiple barrier elements initially held together by a connection means to form the barrier, the barrier having a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore;
- a sealing means for preventing fluid flow from the first portion to the second portion; and
- a destabilizing mechanism arranged for disengaging the connection means from at least one of the barrier elements upon activation of the mechanism, so that support between adjoining barrier elements is removed thereby disintegrating the well barrier.
2. The well barrier of claim 1, wherein the multiple barrier elements are formed in one piece provided with notches in at least a portion of the surface of the well barrier, and the connection means comprises the non-notched portion of the well barrier.
3. The well barrier of claim 1, wherein the barrier elements are provided by means of separate, preshaped barrier elements being connected to each other by the connection means, the connection means being selected from one of or a combination of: an adhesive; a wire; the sealing means, to form the well barrier.
4. The well barrier of claim 1, wherein the well barrier is further provided with a support element for supporting the barrier elements, the support element facing the second portion of the wellbore.
5. The well barrier of claim 1, wherein the sealing means is a sealing element facing the first portion of the wellbore.
6. The well barrier of claim 5, wherein the sealing element is selected from the group consisting of an elastomeric membrane, a coating, and an adhesive.
7. The well barrier of claim 1, wherein the sealing means is the non-notched portion of the well barrier.
8. The well barrier of claim 1, wherein the well barrier is provided with a pressure arch towards the first portion of the wellbore.
9. The well barrier of claim 1, wherein the well barrier is provided with a further well barrier, the further well barrier being mirrored with respect to the well barrier about a plane being perpendicular to a longitudinal axis of the wellbore.
10. The well barrier of claim 9, wherein the second portion of the wellbore is defined between the well barrier and the further well barrier.
11. The well barrier of claim 1, wherein the destabilizing mechanism comprises a releasable holding means arranged such that upon releasing the holding means the well barrier is moved by the fluid in the first portion, the movement causing the well barrier to disintegrate.
12. The well barrier of claim 1, wherein the destabilizing mechanism is an arrangement for raising the pressure of the fluid in the second portion to a level higher than the fluid pressure in the first portion of the wellbore facing the further well barrier.
13. The well barrier of claim 1, wherein at least one of the multiple barrier elements has a form as a keystone supporting adjoining barrier elements, the keystone element having a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore.
14. The well barrier of claim 13, wherein the at least one keystone element is provided by means of multiple elements.
15. The well barrier of claim 1, wherein the barrier facing the first portion of the wellbore has a concave lens shape, and wherein a majority of the barrier elements are wedge shaped with a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore.
16. A method for controlling a disintegration of a well barrier for sealing off a first portion of a wellbore from a second portion of the wellbore, the first portion having a higher fluid pressure than the second portion, wherein the well barrier is held in place in the wellbore by a holding means prevention movement of the well barrier in a direction from the first portion to the second portion, the well barrier comprising:
- multiple barrier elements initially held together by a connection means to form the barrier, the barrier having a surface area facing the first portion of the wellbore that is larger than the surface area facing the second portion of the wellbore;
- a sealing means for preventing fluid flow from the first portion to the second portion; and
- a destabilizing mechanism arranged for disengaging the connection means from at least one of the barrier elements upon activation of the mechanism, so that support between adjoining barrier elements is removed, thereby disintegrating the well barrier, the method comprising:
- pre-shaping the barrier to disintegrate in multiple barrier elements of desired size and shape; and
- activating a destabilizing mechanism that will provide a force sufficient to break a connection means initially holding the multiple barrier elements together, thereby causing the barrier to disintegrate into said multiple barrier elements of desired size and shape.
Type: Application
Filed: Feb 9, 2012
Publication Date: Jan 9, 2014
Applicant: WTW SOLUTIONS AS (STAVANGER)
Inventor: Bard Martin Tinnen (STAVANGER)
Application Number: 13/985,272
International Classification: E21B 33/12 (20060101); E21B 33/134 (20060101);