NO20110246A1 - Bronnbarriere - Google Patents

Abstract

The present invention relates to a well barrier (114) for sealing 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 wellbore is held in place in the wellbore by a holding means ( 207; 602; 805, 806), wherein the well barrier (114) is preformed to disintegrate into at least three barrier elements (114a, 114b, 114k) upon activation of a disintegrant (113; 901), and wherein at least one of the barrier elements has a surface area facing the first portion of the wellbore and larger than the surface area facing the second portion of the wellbore; as well as a method for controlling a well barrier disintegration.

Description

WELL BARRIER

This invention relates to a barrier. More specifically, it relates to a well barrier and/or zone isolation devices for sealing off a first part of a wellbore from a second part of the wellbore in wells related to the production of hydrocarbons.

In connection with the completion of wells, which involves steps such as the installation of production casing, production extension pipe (lower completion) and production pipe (upper completion), barrier systems are usually used.

In one case, a barrier is installed at the top of the lower completion (production extension pipe) to isolate the reservoir, while the production pipe (upper completion) is installed in the upper section of the well.

In another case, a barrier is installed at the bottom of the production pipe during its installation. Once the pipe is positioned correctly, pressure is applied to the inside to set the production packing. In order to form a sealed enclosure during such an operation, and in order to be able to pressurize the interior of the pipe, the bottom of the pipe must be sealed. It is most common to provide such a seal by using a barrier device.

A common requirement for the above-mentioned barrier systems is the ability to hold back the required pressure during the phases where such barrier functionality is required. Another and equally important requirement is that the barrier can be opened or removed when the barrier functionality is no longer needed, thereby opening the extension pipe and/or the production pipe so that fluids can flow through.

Traditionally, these temporary completion barriers were installed and restored using well maintenance techniques, such as cable or coiled tubing.

In many offshore fields, very expensive drilling rigs are used to drill and complete a well. In such cases, any time spent on cable run or coiled tubing operations will contribute to making the completion of the well more and more expensive, as this increases the time that the drilling rig must be rented to complete the well. In order to eliminate the need to operate the above-mentioned barrier systems via cable or coiled pipe, barriers have been developed that can be operated to open without the need for physical intervention in the well. The first systems of this type were ball valves, flap valves, sliding sleeves or the like which were operated to open by cycling the well pressure through the use of a pump at the surface of the well.

Cycle pressurization means the repeated pressurization and depressurization (bleeding) of the pressure in the pipe (and/or the top of the extension pipe) to operate mechanical metering systems associated with the downhole barrier. After a certain number of pressure cycles, the mechanical counting system will typically engage a barrier activation mechanism that causes the barrier/valve to open. Such an intervention is typically achieved by the counter mechanism ultimately operating a valve member belonging to the actuation system, which allows the well pressure to work against an atmospheric chamber via a piston, and where the resulting movement is used to displace the valve member to an open position. In other versions, such engagement is achieved by the counting mechanism ultimately operating a mechanical latch belonging to the actuation system, which releases a biased spring mechanism in the actuation mechanism, after which this causes the valve member to shift to an open position. Other similar methods for activating and displacing the valve part can be used. Such methods will be understood by a person skilled in the art and are not described further here.

A disadvantage of barriers made of metal, such as the barrier systems described in the previous section, is that options for mechanical removal of the barrier are associated with a relatively high cost and risk if the cycle opening mechanism or activation mechanism stops working, or if the valve element fails to shift to open position for any other reason. An example of alternative removal is to use coiled tubing to offset to the open position or, in the worst case scenario, to mill away a steel ball valve or poppet valve.

Typical causes of failure can be waste residues in the well, which jam the cycle opening 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 of barrier removal in this regard is a mechanical cycle opening mechanism that triggers an activation mechanism, where an explosive charge is detonated inside, or near, the brittle barrier. An alternative method results in the mechanical cycle opening mechanism operating a mechanical lock containing a biased spring system. When the pre-tensioned spring is released, it will drive an impact device, such as a spear, into the brittle barrier and shatter it.

A major advantage of using brittle, non-metallic barrier elements is that they are easier to remove mechanically than steel barriers if the mechanical cycle opening procedure for activation fails for any reason. Instead of having to use coiled tubing to mill away a steel barrier, cable driving can be used in conjunction with a spear, hammer device, or other device or combination of devices, to crush the barrier. Thereby, it is possible to provide a faster and more cost-effective backup activation.

Publication US 2003000710 Al presents a downhole, non-metallic sealing element system related to downhole tools, such as bridge plugs, fracturing plugs and gaskets that have a non-metallic sealing element system for isolating formations or leaks in a casing pipe in a wellbore, or in several production zones.

Publication US 2009283279 Al presents a zone isolation system for use in a well. The zone isolation system includes a zone isolation tool, at least one anchor,

and at least one polished bore receptacle. The zone isolation system includes a set string for activating the zone isolation tool and/or the at least one anchor. It may also include an isolation string to maintain separation zones during production or injection into the well.

Publication US 2002195739 A1 discloses a method for producing a sealing or an anti-extrusion component for use in a downhole tool. The component is made from a composition containing a polyether ketone ketone or a derivative of a polyether ketone ketone.

Publication US 2009151958 Al presents a method and a device for temporary well zone isolation. In particular, it presents temporary well zone isolation devices with brittle barrier elements and methods for disintegration of the brittle barrier elements.

Publication GB 2391566 A discloses a formation isolation valve for use in an underground well. A mechanical device can be used to open and close the valve. The actuators may include a rupture disk ("rupture haze") or other forms of remote-controlled actuators.

A common problem with barriers made of brittle materials is that a blow or a large force is required to break them. In the case where explosives are used, this may involve a possible safety risk. Requirements to create a mechanical stroke and/or a large force in an actuation system make this somewhat more complex and prone to failure. The presence of waste residues/impurities in the well can inhibit performance to a large enough extent that the opening activation/removal activation fails.

A further method of removing a barrier made of a brittle material consists in disintegrating the barrier by means of a fluid pressure. WO 2009126049 presents a plug element for carrying out tests in a well, a pipe or the like, comprising one or more plug bodies of disintegrable/breakable material which are arranged to be broken into pieces by effects applied from within. The plug comprises an internal cavity adapted to fluidly communicate with an external pressure-generating body, and the plug is designed to be ruptured by the introduction of a fluid into the internal cavity, and such that the pressure in the cavity exceeds an external pressure to a level where the plug is blown to pieces.

Brittle material barriers that are broken by the means mentioned above can, however, lead to another problem. In some cases, and despite cracking of the brittle barrier, the particular well situation (local pressure, fluids, compacted tailings surrounding the barrier) may prevent the particles from being physically removed over any significant distance from their original position. Consequently, the cracked (but not physically disintegrated) barrier may still represent a relatively solid body in the well and prevent flow, thereby blocking subsequent operational steps. Finally, such cracked barriers may have to be physically removed via cable routing or coiled pipe interventions, as described above.

The purpose of the invention is to remedy or reduce at least one of the disadvantages of the known technique.

The purpose is achieved according to the invention by the features indicated in the following description and in the subsequent patent claims.

According to a first aspect of the present invention, a well barrier is provided to seal off a first part of a wellbore from a second part of the wellbore, where the first part has a higher fluid pressure than the second part, where the well barrier is held in place in the wellbore of a retaining means, wherein the well barrier is preformed to disintegrate into at least three barrier elements upon activation of a disintegrating means, and wherein at least one of the barrier elements has a surface area facing the first part of the wellbore, which is greater than the surface area facing the second part of the wellbore. This has the effect that the shape of the individual barrier elements after disintegration of the barrier can be controlled, so that the probability of the barrier elements causing problems after disintegration is minimised. Furthermore, providing a preform where at least one of the barrier elements has a surface area facing the first portion of the wellbore that is greater than the surface area facing the second portion of the wellbore can provide a wellbore barrier capable of withstanding a high fluid pressure in the first part, but which is very vulnerable to fluid pressure in the second part of the wellbore.

The barrier is preferably pre-formed in such a way that it disintegrates into more than the aforementioned three barrier elements.

In one embodiment of the present invention, the preform is provided by means of a notch in at least part of the surface of the well barrier.

In one embodiment of the present invention, the preform is provided by means of separate, preformed barrier elements which are connected together to form the well barrier.

In one embodiment of the present invention, the preform may be provided by means of a combination of one or more parts of the barrier provided by notches, and one or more parts of the barrier provided by separate, preformed barrier elements.

The well barrier can also be provided with a support element to support the barrier elements. Preferably, the support element faces the other part of the wellbore.

The well barrier can also be provided with a sealing element. Preferably, the sealing element faces the first part of the wellbore. The sealing element is selected from a material which is suitable for providing an impermeable barrier between the fluid in the wellbore and the barrier elements.

Preferably, the well barrier has the shape of a pressure arch towards the first part of the wellbore.

In one embodiment, the well barrier is provided with a further well barrier, where the further well barrier is reflected, in relation to the well barrier, around a plane which is perpendicular to a longitudinal axis of the well bore. In this embodiment, the second part of the wellbore is delimited between said well barrier and said further well barrier.

In one embodiment of the present invention, the disintegration agent comprises a releasable holding agent so that the well barrier, upon release of the holding agent, is moved by the fluid in the first part, the movement causing the well barrier to disintegrate.

In one embodiment of the present invention, when the second part is delimited between the well barrier and the further well barrier, the deintegration means is an arrangement to increase the pressure in the fluid in the second part to a level that is higher than the fluid pressure in the first part of the wellbore.

In a second aspect of the present invention, a method is provided for controlling a disintegration of a well barrier, where the method comprises: - pre-shaping the barrier to disintegrate into at least three barrier elements of the desired size and shape; and - to activate a disintegration agent which will cause the barrier to disintegrate into said at least three barrier elements.

The following describes a non-limiting example of a preferred embodiment which is illustrated in the attached drawings, where: Fig. 1a-1c illustrate one example of generic use of the invention; Fig. 2-5c illustrate the design, functionality and operation of one barrier according to a preferred embodiment of the invention; Fig. 6 illustrates a combination of barrier elements to provide two-way pressure integrity; Fig. 7 illustrates an embodiment where several barrier elements are used to resist pressure from the same direction to provide further operational security and redundancy; Figures 8a-8c illustrate additional system features used to guarantee a reliable barrier removal/disintegration process; Fig. 9-14 illustrate the use of pressure compensation systems in connection with a double barrier design in continuation of a preferred design. Such pressure compensation systems are used to provide a lower pressure between the barrier elements than on the outside of the barrier elements; Fig. 15 illustrates a preferred design principle for barrier elements that make up the barrier; Fig. 16a illustrates a split drawing of a barrier according to the present invention;

Fig. 16b illustrates the barrier in fig. 16a arranged in a part of a tube; and

Fig. 16c illustrates the barrier of fig. 16b seen from the first part of a well hole. Figs. 1a-1c illustrate a borehole 101. A casing 102 is used to prevent the borehole 101 from collapsing during drilling and subsequent production, and to seal the borehole wall to prevent unwanted leakage to or from strata/zones in the subsurface and, finally, to provide a barrier between the pressurized hydrocarbon reservoir and the open environment. In most cases, the casing is cemented to the rock wall, which will be understood by any person skilled in the art and, accordingly, will not be illustrated here. A generic well completion is illustrated. In this illustrated case, the lower completion comprises a cemented production extension pipe 103 which is open to the hydrocarbon reservoir via perforations 104. One skilled in the art will know that the design and configuration of the production extension pipe 103 may vary significantly from that illustrated here. The production extension pipe 103 is anchored to, and forms a seal against, the casing 102 by means of an extension pipe hanger system 105.

The upper completion comprises the production pipe 106, which is inserted into the lower completion by means of a sealing string assembly 107. A sealing arrangement 108 comprising a barrier 114 according to the present invention is installed below a production package 109. At the top of the well, the pipe is 106 completed in the wellhead 110. The completion execution can vary significantly from what is shown in fig. 1, and there are common add-on components not illustrated here, such as a downhole safety valve. These facts will be understood by those skilled in the art. Correspondingly, the device according to the present invention can be used for other completion designs than the one shown here, and fig. 1 shows only an example.

When the completion is run in the hole, the production pack 109 is not activated, as illustrated in fig. let.

The tube centerline 115 is illustrated for reference.

Referring now to fig. lb, a pump 111 is placed in fluid communication with the wellhead 110. To set the production packing 109, which means to expand the mechanical anchors and sealing elements into contact with the casing 102, the pump 111 is used to apply high pressure to the fluid inside the pipe 106 This is possible because the sealed enclosure formed by the pipe 106, the sealing arrangement 108, the wellhead 110 and the pump 111. After setting the packing 109, the barrier 114 is no longer required in the well. The next step is to remove the barrier 114 so that the well can be put into production or injection.

To remove the barrier 114, the fluid inside the pipe 106 is pressure cycled, as described earlier in this document, using the pump 111. For each complete pressure cycle, a mechanical counting mechanism 112 is operated one step. After a certain number of steps, the mechanical counting mechanism 112 will interact with an activation module 113 which triggers the opening and/or removal of the barrier 114.1 summary then the barrier 114 opens after a certain number of cycles, i.e. pressurization and depressurization of the pipe fluid. Fig. 1c illustrates the well completion after the barrier 114 has been removed.

The mechanical counting system 112 and activation system 113 can be replaced or supplemented by alternative activation systems, such as battery-operated, sensor-based or time-meter-based activation systems, which are controlled by internal microcontroller units or similar that are available in the market. Details regarding such associated activation mechanisms will be understood by one skilled in the art and no further details regarding such are described here.

Fig. 2 shows, on a larger scale, one embodiment of the barrier 114 together with an associated activation system 113 according to the present invention, as well as a counting system 112 as indicated in figures la-lc, or alternative systems for wireless activation of the barrier system, which are not shown here. However, such a system is assumed to be included in the well completion and is in fluid communication with the activation system 113 through a flow channel 201.

In a preferred embodiment, and upon activation, a mechanical counter system 112, as indicated in Figures la-lc, or alternative system for wireless activation, will operate a valve manifold so that a pressurized fluid is introduced into the activation system 113 through the flow channel 201. Details of operation of any mechanical counting system 112, or alternative wireless actuation systems, valve manifolds, etc. are known to one skilled in the art and are not described further here. In the embodiment shown in fig. 2, the activation system 113 has a tubular shape and is incorporated or connected to the production pipe 106. Only one side of the cut-through activation system 113 is illustrated. The center of the cut-through actuation system 113 is illustrated by the dashed line 115.

The barrier 114 shown in FIG. 2, consists of smaller barrier elements, some of which are indicated by reference numbers 114a, 114b, 114k. A relatively thin-walled foundation dome 114s made of a brittle material, such as concrete, is used to simplify the construction of the barrier 114, and to prevent unwanted premature migration/movement of the barrier elements 114a, 114b, 114k in relation to each other. In one embodiment of the present invention, the barrier elements 114a, 114b, 114k are attached to the foundation dome 114s and/or each other by means of an adhesive, or by using a metal wire or other suitable attachment methods. In another embodiment, a relatively thin-walled ring (not illustrated here), which is made of a similarly brittle material, forms the perimeter of the barrier 114 to facilitate assembly, and to provide stability between components of the barrier 114.

In an alternative embodiment, the barrier 114 consists of one element provided with notches that indicate break directions in the barrier 114 and into the barrier elements 114a, 114b, 114k of a desired, predetermined size.

The barrier 114 is locked in place on the inside of the activation system 113's tube by means of a finger coupling 207 and a locking/cover sleeve 208.

When activated, pressurized fluid is led from a valve manifold which is operated as described

at other places in the document, and into the activation system 113 via the channel 201. Here the pressurized fluid acts on a piston 202. The piston 202 is in mechanical contact with a holding profile 204 via a piston tube stem (piston mandrel) 203. Longitudinal grooves 205 are provided in piston tube stem 203. A set of fastening bolts 209 is screwed into the lock/cover sleeve 208, where the fastening bolts 209 protrude through the grooves 205 in the piston tube stem 203.

In one embodiment, the smaller elements 14a, 14b, 114k are freely movable in relation to each other, but they form a mechanically stable geometry when assembled as shown in fig. 2. In alternative embodiments, a thin-walled dome 14s helps to keep the geometry of the barrier 114 stable. In the described embodiment, the barrier 114 is designed to resist forces from a direction illustrated by an arrow 210.

Thus, a well sealing arrangement 108 is provided where the power integrity is provided by at least one barrier 114 associated with at least one activation system 113 which includes at least one operable support element 207, where said barrier 114 is constructed of smaller barrier elements 114a, 114b, 114k which 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 operating at least one support element 207.

Thus, a well sealing arrangement 108 is provided where the force integrity is provided by at least one barrier 114 associated with at least one activation system 113, where said barrier 114 is constructed of smaller barrier elements 114a, 114b, 114k which form a stable mechanical structure against forces from at least one side of the sealing arrangement 108, where said stable mechanical structure becomes unstable by operating the activation system 113.

To ensure pressure integrity and not just force integrity, the barrier 114 in the embodiment shown is provided with an elastomeric membrane 212. In other embodiments, the elastomeric membrane 212 can be replaced with other coating means suitable for forming a seal. Such a coating agent can consist of adhesives, resin coatings or the like.

Reference is now made to fig. 3. When the high-pressure fluid pushes the piston 202 downwards, the holding profile 204 is displaced at the same time. After a certain travel, the holding profile 204 will no longer support the finger coupling 207 radially. When the radial support is removed from the finger coupling 207, the fingers will be pushed radially outward and away from the tube 106's centerline 115. In the embodiment shown in fig. 4, the finger coupling 207 is designed so that the fingers spring from the rest position and towards a position radially outwards and into a recess 503 when the barrier 114 is assembled. In another embodiment, the cloud wing, which is produced by the thrust force indicated by the arrow 210 acting on the barrier 114, pushes the fingers of the finger coupling 207 radially outward and into the recess 503.

Reference is now made to fig. 5a. As a consequence of the finger joint 207 no longer supporting the barrier 114, the barrier 114 is free to move downward. As the piston 202, the piston tube stem 203 and the support member 204 are displaced downward some distance after the radial support has been removed from the finger coupling 207, the piston tube stem 203 comes into contact with the fixing bolt 209 when the bolt 209 abuts an end portion of the slot 205. Accordingly, the locking /cover sleeve 208 downwards. At the time that the retaining bolt 209 and the associated profile in the lock/cover sleeve 208 lands on a shoulder 501 provided in a tube recess 502, the downward movement of the piston 202, the piston tube stem 203 and the support member 204 stops. At this time the lock/cover tube stem 208 covers the opening between the bore and the recess 503. Preferably, a mechanical locking system will ensure that the lock/cover pipe stem is locked in place in relation to the recess 503. Such a locking system is not shown, but it can for example be made up of a snap lock or another suitable locking device that will understood by a person skilled in the art.

While still referring to fig. 5a, the barrier 114 is now free to move further down the pipe 106. In a preferred embodiment of the invention, the barrier 114 will now disintegrate due to the forces caused by the pressure according to arrow 210, associated flow forces, collisions with the pipe 106's wall, or collisions with other objects in the well. In a preferred embodiment, the smaller barrier elements 114a, 114b, 114k are free to move relative to each other, or they are in contact with each other by means of a relatively weak adhesive, thin metal wires, or other means that will be released when relatively moderate forces act on the barrier 114.1 the case where a relatively thin-walled dome 114s is used or, alternatively, in combination with a thin-walled edge (rim) along the perimeter of the barrier 114, a preferred embodiment of this is that the thin-walled dome 114s and/or edge is made of a brittle material which will shatter in the process after the radial release of the finger coupling 207. Fig. 5b illustrates the situation where the barrier 114 is in the process of being disintegrated.

As will be understood by one skilled in the art, a barrier element of the type illustrated here as barrier 114 is designed to withstand greater forces from the direction illustrated by arrow 210 than in the opposite direction (from below in the illustrated embodiment).

Fig. 5c illustrates another preferred feature. Here, the elastomer membrane 212 is physically bonded to the cover tube stem 208 along its circumference 504. When the barrier 114 is activated, the barrier elements 114a, 114b, 114k, etc. will thus be physically separated from

the elastomer membrane 212. Furthermore, the elastomer membrane 212 will eventually be inverted and torn to pieces/permanently destroyed by the fluid forces acting on it. In this way, a potential problem is avoided in that the mechanical parts, such as the barrier elements 114a, 114b, 114c, as well as the sealing parts, such as the elastomer membrane 212 in the barrier 114, are able to re-form a barrier seal elsewhere in the well. The bond between the elastomer membrane 212 and the cover tube stem 208 can be achieved by means of mechanical fasteners, adhesives, or by vulcanizing the elastomer membrane 212 to the cover tube stem 208.

Fig. 6 illustrates a barrier system comprising two barriers 114, 601. The barrier 601 is added to enable the system to withstand forces and pressures according to an arrow 604.

As illustrated in fig. 6, the barrier 601 is held in place by a retaining sleeve 603 and a wedge 602. Further, regarding this embodiment, the barrier 601 is removed as a result of the barrier 114 being removed or disintegrated. When barrier 114 is disintegrated, as shown in fig. 5c, the barrier 601 will be exposed to the disintegrated barrier 114 and to fluid forces acting on the barrier 601 from a direction indicated by arrow 210, where the barrier 601 has very limited pressure integrity.

In another embodiment of the invention, the barrier 601 can be activated by a similar activation system and method, and as described in connection with Figures 2-5. Such an activation mechanism can be independent of, or form an integral part of, the activation system 113.

In one embodiment of the present invention, it is the lower of the two barriers, i.e. the barrier 601, which is operated by the activation system 113, as discussed above. This means that the barrier system presented in fig. 6, is turned upside down. In many cases, it is desirable to open the well in an underbalanced condition, which means that the volume above the upper barrier 114 has been filled with a relatively light fluid, such as a salt solution (brine), so that the reservoir is capable of producing fluids into the well immediately after the barrier removal. In this way, one avoids "shock-injecting" a potentially contaminated fluid into the formation, thereby achieving a potential cleaning effect by "shock-producing" from the reservoir into the well when the barrier is removed. In order to enable barrier removal in underbalance, the lower barrier 601 must thereby be removed before the upper barrier 114 is removed.

In yet another embodiment of the invention, the barriers 114 and 601 are operated simultaneously when the activation system 113 is activated.

In one embodiment of the present invention, the barriers 114 and 601 are fully or partially integrated into one structural element with a cavity on its inside.

In all embodiments exemplified in Figs. 2-6, the barriers, such as barrier 114, are prevented from disintegrating in the opposite direction to that illustrated in Figs. 5, of mechanical forces applied by such as the finger coupling 207, the holding sleeve 208 and the elastomer membrane 212. Also in a preferred embodiment of the invention, barriers, such as the barrier 114, are further held in place by means of compressive forces acting on them via the elastomer membranes, such as the elastomer membrane 212. Furthermore, regarding FIG. 6, this is achieved by always ensuring that there is a lower pressure between the barriers 114, 601 than that which exists at the top of the barrier 114 and the bottom of the barrier 601, respectively. In one embodiment, this is achieved by maintaining atmospheric pressure conditions in the area between the barriers 104 , 601. In this way, the well pressure above the barrier 114 and below the barrier 601 will keep the barrier in place until the activation system 113 is activated.

In one embodiment, a vacuum is applied in the cavity between the barriers 114 and 601 to ensure that compressive forces keep the barriers in place and intact while they are handled on the surface, and with ambient atmospheric pressure.

In one embodiment, the activation system 113 does not include the finger clutch 207 and the associated mechanisms. Instead, the barriers 114 and 601 are removed by introducing a high pressure into the cavity between them, either from a source at a location above the barrier 114 or below the barrier 601, or on the radial outside thereof or from a pressurized fluid reservoir forming 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 directing a high-pressure fluid into the cavity between the barriers 114, 601, as shown, in combination with the removal of mechanical support of one or more barriers.

In one embodiment, the elastomeric membrane 212 will keep the barrier 114 mechanically stable by means of mechanical forces/mechanical stiffness associated with the membrane 212 (similar considerations apply to the barrier 601).

In one embodiment, the cycle opening system 112 and/or the activation system 113 is incorporated in one or all of the barriers 114, 601 and/or in the smaller barrier elements 114a, 114b, 114k.

In the following figures, the internal parts of the cut-through activation system are not shown for the sake of simplicity.

Reference is now made to fig. 7. Further regarding the illustrations herein, in one embodiment of the invention the barriers 114, 601 described in FIG. 6, supplemented by further barriers 114', 601'. This may be required in cases where additional security and/or redundancy is required.

Fig. 8a illustrates an embodiment where the barriers 114, 601 are provided with rod elements 801, 802 which will add thrust to the wedge stones 114k, 804 when one or both of the barriers 114, 601 are activated. In other embodiments of the invention, the rods 801, 802 are replaced by cutting elements which will be forced up between, inside or through the barriers 114, 601 and through the elastomer membranes, such as the elastomer membrane 212. The intent of the construction shown in fig. 8, is to prevent accidents where the barriers 114, 601 re-form stable barrier structures after activation instead of disintegrating.

In a preferred embodiment, and if the main method of barrier removal/disintegration (cycle opening) does not work, a cutting device will be sent down the cable or coiled pipe and used to cut through the membrane 212. This means that the upper barrier 114 will leak, and this will cause a pressure to act on top of the barrier 601, causing it to disintegrate (as it is not designed to withstand pressure from that direction). By then bleeding off the pressure above barrier 114, this will also disintegrate, and for similar reasons, as the higher reservoir pressure will act on it in the opposite direction. In some embodiments, the membrane 212 is mechanically protected or double barriers are used (as described in connection with Fig. 7). This may be the case if the operational order to complete the well involves a risk of objects accidentally falling onto the diaphragm 212 and causing it to leak when it was intended to provide pressure integrity. In such cases, and further regarding another embodiment of the invention, a spear device will be sent down the cable or coiled pipe and used to crush the barrier 114. In one embodiment, the cable driving tool will be a combined cutting and spear device.

Reference is now made to fig. 8b. For simplicity, only one barrier 114 is shown. In this embodiment, the finger coupling 207 is different in form and function from what has been described above. In fig. 8b, the barrier 114 is supported by two different profiles. The supporting profiles are formed by a lower support shoulder 805 and an upper support shoulder 806. In the embodiment shown, the lower support shoulder 805 is part of the finger coupling 207 and can be operated in a radial or longitudinal direction, as illustrated by arrows 807 and 808. In in the same embodiment, the upper support shoulder 806 forms part of, or is attached to, the pipe 106. When the lower support shoulder 805 is released, pressure forces beyond the arrow 210 will thus attempt to push the barrier 114 downwards. The upper support shoulder 806 will counteract this but, further regarding a preferred embodiment, this shoulder is made so thin that the local compressive forces on the barrier 114, where it is in contact with the upper support shoulder 806, will cause the barrier 114 to deform or partially disintegrate along this surface. Next, the barrier 114 will be pushed through the upper support shoulder 806. In a preferred embodiment, this sequence of events will cause the barrier 114 to open in a manner where the lower and now unsupported outer edges of the barrier 114 will be pushed against the pipe wall, whereupon the barrier 114 opens like "a flower blooming". The intention of the features described above and indicated in fig. 8b, is to arrange for the most possible controlled disintegration of the barrier 114, as well as to avoid an accident situation where the barrier 114 loses support, but does not disintegrate, and where it lands on a low-lying shoulder (not shown) in the well and re-establishes itself as a stable structure. Fig. 8c illustrates in greater detail the process of opening the barrier as a blooming flower. Here, the lower support shoulder 805, which is shown in fig. 8b, has been removed, and the barrier 114 now rests only on the upper support shoulder 806. The loss of radial support combined with the force (indicated by arrow 210) acting on the barrier causes the barrier members 114a, 114b, 114c to be pushed outward against the pipe wall, as illustrated by arrows 809a and 809b. The outward movement can be a result of physical displacement of the barrier elements 114a, 114b, 114c, 114k as well as deformation and physical destruction as a result of exposure to the fluid force 210. In the shown embodiment, the barrier elements 114a, 114b, 114c will be pushed outwards to such an extent that the "wedge" element 114k of the barrier elements can pass through the center of the barrier 114, as illustrated by an arrow 810, after which the entire barrier structure will collapse.

In one embodiment, both the upper support shoulder 806 and the lower support shoulder 805 are operable. For example, both shoulders 806, 805 can 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 movement distance than the lower support shoulder 806, so that the support shoulders does not re-establish itself in a fully supporting mode relative to the barrier 114. For this embodiment, and as the lower support shoulder 805 is allowed to travel a certain longitudinal distance before landing on a dedicated stop profile, an impact force will be applied to the barrier 114 in in addition to the static fluid pressure forces. In one embodiment, such an impact force will help to deform and/or partially disintegrate the barrier 114 in the area where it is in contact with the lower support shoulder 805.

In the embodiment shown in fig. 9, an associated system component is introduced in the form of a pressure compensation system 901. To facilitate the illustration of the pressure compensation system 901, the right side of the cut-through pipe is shown on a larger scale relative to the barrier and pipe dimension. A main intention of a pressure compensation system is to equalize pressure in the cavity 902 between the barriers 114, 601 (the second part of the wellbore) in relation to the pressure on the outside of the barriers 114, 601 (the first part of the wellbore). In this way, the barriers 114, 601 do not have to withstand as large forces as it would have been if there was atmospheric pressure on the inside of cavity 902. This may mean that the barriers 114, 601 are built slimmer.

In some cases, the incorporation of the pressure compensation system 901 will enable the use of the barrier in cases where it would not be physically possible to use a similar barrier system with atmospheric pressure inside the cavity 902. The illustrated pressure compensation system 901 equalizes the pressure in the cavity 902 in relation to the pipe pressure above the barrier 114. In an alternative embodiment (not shown), the pressure compensation system 901 equalizes the pressure in relation to the pipe pressure below the barrier 601, or from the annulus between the pipe and the well's casing. The pressure compensation system 901 is in fluid communication with the inside of the pipe via a channel 903, and in fluid communication with the cavity 902 via a channel 904. The channel 903 is in fluid contact with a piston 905 which is supported by a spring 906. In this way, and when the completion is run in the hole, the increased pipe pressure will act on the piston 905 via the channel 903, after which the piston 905 will travel downwards and pressurize the fluid in the cavity 902 via the channel 904. As the spring 906 exerts a force on the lower side of the piston 905, however, the pressure on the inside of the cavity 902 always be lower than the pressure on the inside of the tube, which acts on the channel 903.

In one embodiment of the invention, the cavity 902 is filled with a fluid under vacuum, which can for example be introduced in combination with a small gas pocket. The purpose of the gas pocket is to compensate for temperature-induced fluid expansion on the inside of the cavity 902 when the system is lowered into a warm well climate. Such temperature expansion can, if not compensated for, cause the barriers 114, 601 to leak and fail. In another embodiment, said temperature expansion is compensated for by allowing a compensatory travel of the piston 905.

In one embodiment of the invention, the system is arranged for installation in the well by pushing the piston 905 to a position where the spring 906 is compressed while the cavity 902 is filled with said fluid and/or fluid/gas mixture. After filling the cavity 902 and closing the filling port (not shown in the drawing), the piston 905 is released so that the spring 906 pushes it upwards. In this way, a pressure is created on the inside of the cavity 902 which is lower than the surrounding (atmospheric) pressure. This can help to keep the barrier elements 114,601 more stable during assembly and intervention down the well, as the elastomer membrane will be exposed to suction forces from inside the barrier.

Reference is now made to fig. 10. In many cases, and during the installation sequence of the well completion, the pressure on the top of the barrier 114 and the barrier 601 can vary in relation to each other. For example, the completion equipment may be run in drilling fluid, and consequently the barrier 114 as well as the barrier 601 may be subjected to pre-pressures corresponding to the hydrostatic column of the drilling fluid when installed at depth. In the pipe above the barrier 114, the drilling fluid can be displaced by so-called completion fluids, usually salt water, before setting the production pack and opening the barrier. As the completion fluid is usually less dense than the drilling fluid, the pressure on top of the barrier 114 can now be significantly lower than the pressure below the barrier 601. Under other conditions, other parameters can change this relationship. In all cases, it is important that the pressure on the inside of the cavity 902, which constitutes the second part of the wellbore as mentioned in the first aspect of the invention, is always lower than the pressure in the first part of the wellbore, i.e. the pressure above the barrier 114 and below the barrier 601 as shown in the figures, during all relevant phases of the well completion process. If the pressure in the cavity 902 exceeds any of the pressures present in any phase, this may cause leaks and, in the worst case, a premature disintegration of the barriers 114, 601. To prevent the pressure in the cavity 902 from exceed a defined maximum pressure, the piston 905 is provided with a stop rod 1001. After a certain travel of the piston 905, the stop rod 1001 will hit the bottom of the drilled hole 1002 and prevent the piston 905 from moving further. Accordingly, the pressure inside cavity 905 will not increase as a function of advancing the barrier further into the well. This is illustrated in fig. 11.

Fig. 12 illustrates another way to avoid over-pressurization of cavity 902. Here the channel 903 is in fluid communication with the top of the piston 905 via a channel 1202 in a plug 1201. The plug 1201 is provided with elastomer seals at both ends. In the initial position, the plug 1201 is fixed to the pipe wall by means of shear pins 1203. The cavity 1204 which is formed at the right end of the plug 1201 and the associated bore in the pipe, and which is sealed by the seal at the right end of the plug 1201, houses initially a gas at near atmospheric pressure. As the barrier is lowered into the well and the surrounding pressure increases, the cutting pins 1203 will be cut off at a certain depth due to forces generated by the difference between the pressure in cavity 1204 and the surrounding pressure. This is illustrated in fig. 13 and will cause plug 1201 to move to the right. When this is fully displaced, the seal on the left side of the plug 1201 will be in contact with the wall of the channel 903 and form a seal. Consequently, no further pressure increases will occur inside the cavity 902 as a function of the barrier being lowered into the well. Fig. 14 illustrates an embodiment where the piston and plug mechanism is mirrored above and below the barriers 114 and 601 to compensate both from the top and bottom of the barrier. The capacity of the shear pins 1203 of the upper piston and plug mechanism, as shown in Figure 13, may be equal to or different from the capacity of the shear pins of the mirrored piston and plug mechanism arranged below the barrier 601. The capacity may be selected depending on the specifications of a given case. Fig. 15 illustrates one method for delimiting the barrier elements in the barrier 114, some of which are indicated by reference numbers 114a, 114b, 114c, 114k. In the embodiment shown in fig. 15, a cut is made in the concave lens shape of the barrier 114 and from an imaginary point 1501 which is located somewhere on the centerline axis 115, and which points straight out from the center of the barrier 114, i.e. the center axis 115 of the wellbore or the tubular element (not shown) where the barrier 114 is mounted.

In the embodiment shown, the lenticular barrier 114 is provided with cuts that run out from point 1501, where the cuts are symmetrical in relation to the centerline axis 115 in the wellbore/pipe. In one embodiment, two sets of cuts, such as the illustrated cuts, are made perpendicular (or at any desired angle) to each other relative to the xy plane. As a result, the smaller elements 114a, 114b will assume a wedge-shaped configuration with a cubical base along the outer edges of the barrier 114, while they will have a concave cubical/rectangular configuration in the center of the lens.

In a preferred embodiment, the smaller elements 114a, 114b, 114c, 114k are made by providing circular cuts concentric with the circumference of the barrier 114, where the cuts are made along lines similar to the lines emanating from point 1501. Next, radial cuts are made from the outer edges of the barrier 114 and towards the centre. In one embodiment, the entire barrier is cut by said radial cut, right from the outer edges to the center. In another embodiment, the center barrier element 114k, i.e., the "wedge", is not cut. Accordingly, the barrier elements 114a, 114b, 114c will be formed from concentrically and radially cut intersections, with the exception of the wedge stone barrier element 114k which will have a substantially truncated cone shape where the surface area facing the first part of the wellbore is greater than the surface area facing the second part of the wellbore. This is shown clearly in figure 16a-16c, which will be discussed hereafter.

In the embodiment shown, the barrier elements 114a, 114b, 114c, 114k will resemble building blocks in an igloo; however, the block along the perimeter of the "lens" will be supported by an angled plinth rather than a horizontal plinth.

In one embodiment, the barrier 114 will consist of barrier elements 114a, 114b, 114c, 114k which are delimited by cuts running all the way from the top/outer end to the bottom/inner end of the barrier. In another embodiment, layered sub-elements (not shown) form the fully assembled barrier 114, the sub-elements consisting of smaller barrier elements 114a, 114b, 114c, possibly with thin-walled dome elements (similar to the dome elements 114s shown in, for example, Fig. 2) between and/or on the outer edges of the layered barrier elements.

In a preferred embodiment, the smaller elements 114a, 114b are made of cast elements made of fiber-reinforced concrete or other robust materials which are suitable for casting, and which are capable of withstanding the required forces. In another embodiment, the smaller elements 114a, 114b, 114c, 114k are machined or produced in alternative, known ways. Preferably, the barrier elements are made of a material that has a higher density than the density of the fluid in the wellbore. This is to ensure that the disintegrated barrier elements sink into the well and do not pose any risk of failure in, for example, any valves that are located downstream of the sealing arrangement 108 that is arranged in a producing well. If it is desirable to prevent the disintegrated barrier elements from sinking into the well, however, the barrier elements can also be made of a material that has a lower density than the density of the fluid in the wellbore.

Fig. 16 a-c illustrate further details of a construction of the force-bearing part of the barrier 114 according to one embodiment of the present invention. Fig. 16a shows an isometric split drawing, fig. 16b shows an isometric view of an assembled barrier 114 according to fig. 16a, and fig. 16c shows a plan view of the assembled barrier 114. Furthermore

regarding this embodiment, the barrier 114 consists of rings 1601-1604 which are cut concentrically, and with an angle on the outer edges which is in accordance with the logic explained in relation to fig. 15. The rings 1601-1604 are cut radially in the barrier elements

114a, 114b, 114c, 114k. In the embodiment shown, the barrier elements in one ring are mounted with an angular offset in relation to the barrier elements in the adjacent ring(s). In this way, and for the embodiment shown, the joint between two barrier elements in the ring 1601 meets the center of a barrier element in the ring 1602, etc. In this way, the barrier 114 becomes physically more stable.

Claims (12)

1. Well barrier (114) for sealing a first part of a wellbore from a second part of the wellbore, where the first part has a higher fluid pressure than the second part, where the wellbore barrier (114) is held in place in the wellbore by a holding means ( 207; 602; 805, 806), characterized in that the well barrier (114) is pre-shaped to disintegrate into at least three barrier elements (114a, 114b, 114k) upon activation of a disintegrating agent (113; 901), and where at least one of the barrier elements has a surface area facing the first part of the wellbore, which is greater than the surface area facing the second part of the wellbore. 2. Well barrier according to claim 1, where the preform is provided by means of notches in at least a part of the surface of the well barrier (114). 3. Well barrier according to claim 1, where the preform is provided by means of separate, preformed barrier elements (114a, 114b, 114k) which are connected to each other to form the well barrier (114). 4. Well barrier according to any one of the preceding claims, where the well barrier (114) is further provided with a support element (114c) to support the barrier elements (114a, 114b, 114k), and where the support element faces the other part of the well hole. 5. Well barrier according to any one of the preceding claims, where the well barrier is further provided with a sealing element (212), where the sealing element faces the first part of the well hole. 6. Well barrier according to claim 5, where the sealing element (212) is selected from the group comprising an elastomer membrane, a coating and an adhesive. 7. Well barrier according to any one of the preceding claims, where the well barrier (114) is provided with a pressure arc against the first part of the well hole. 8. Well barrier according to any one of the preceding claims, provided with a further well barrier (601), where the further well barrier (601) is reflected about a plane which is perpendicular to a longitudinal axis of the well hole. 9. Well barrier According to claim 8, where the second part of the well hole is delimited between the well barrier (114) and the further well barrier (601). 10. A well barrier according to any one of the preceding claims, where the disintegrating means comprises a releasable holding means (207) so that the well barrier (114), upon release of the holding means, is moved by the fluid in the first part, the movement causing the well barrier to disintegrate. 11. Well barrier according to claim 1 when dependent on claim 9, where the disintegration means is constituted by an arrangement to increase the pressure in the fluid in the second part to a level that is higher than the fluid pressure in the first part of the wellbore. 12. Method for controlling a disintegration of a well barrier (114), characterized in that the method includes: - pre-shaping the barrier (114) to disintegrate into at least three barrier elements (114a, 114b, 114k) of the desired size and shape; and - to activate a disintegration agent (207, 901) which will cause the barrier (114) to disintegrate in said at least three barrier elements (114a, 114b, 114k).