Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/10—Sealing or packing boreholes or wells in the borehole
  • E21B33/12—Packers; Plugs
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B29/00—Cutting or destroying pipes, packers, plugs or wire lines, located in boreholes or wells, e.g. cutting of damaged pipes, of windows; Deforming of pipes in boreholes or wells; Reconditioning of well casings while in the ground
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/10—Sealing or packing boreholes or wells in the borehole
  • E21B33/12—Packers; Plugs
  • E21B33/1204—Packers; Plugs permanent; drillable
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/10—Sealing or packing boreholes or wells in the borehole
  • E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
  • E21B33/134—Bridging plugs
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B34/00—Valve arrangements for boreholes or wells
  • E21B34/06—Valve arrangements for boreholes or wells in wells
  • E21B34/063—Valve or closure with destructible element, e.g. frangible disc

Definitions

• 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.
• barrier systems 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.
• 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.
• 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.
• Cycling pressure means repeated pressurizing and depressurizing (bleeding down) the tubing (and/or liner top) pressure in order to operate mecha nical counter systems associated with the downhole barrier.
• the mechanical counter system will engage with a barrier activation mechanism that causes the barrier/valve to open.
• a barrier activation mechanism that causes the barrier/valve to open.
• 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 cha mber via a piston, and the resulting work is used to shift the valve member to an open position .
• 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.
• 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
• ba rrier 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.
• brittle, non-metallic barrier elements are easier to remove mechanically than steel barriers should the mechanical cycle open method of activation fail for any reason.
• wireline could be used, together with a spear, hammer device or other device or combination of devices to crush the barrier.
• a quicker, more cost effective backup activation is possible.
• Publication US 2003000710 Al 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.
• 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 Al 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
• Publication US 2009151958 Al discloses a method and device for temporary well zone isolation.
• 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
• 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.
• US 6,167,963 Bl discloses a drillable composite packer or bridge plug including substantially all nonmetallic components.
• US 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.
• brittle material barriers that are crushed by the means mentioned above, may give rise to another problem.
• the specific well situation local pressure, fluids, compacted debris surrounding the barrier
• 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.
• 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.
• 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 :
• 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 wel lbore;
• 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 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.
• 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.
• 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.
• the support element faces the second portion of the wellbore.
• the sealing means may be a sealing element.
• 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.
• the sealing element is selected from the group comprising an elastomeric membrane, a coating, an adhesive.
• the sealing means is the non-notched portion of the well barrier.
• the well barrier has the form of a pressure arch towards the first portion of the wellbore.
• 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.
• 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.
• 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 well bore 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.
• a method for controlling a disintegration of a well barrier comprising : - pre-shaping the barrier to disintegrate in multiple barrier elements of desired size and shape; and
• Fig. la-lc illustrate one example of generic use of the invention
• Fig. 2-5c illustrate design, functionality and operation of one barrier according to a preferred embodiment of the invention
• Fig. 6 illustrates combination of barrier elements to provide for two way
• Fig. 7 illustrates an embodiment where multiple barrier elements are used to hold pressure from the same direction, to provide for additional operational safety and redundancy
• Fig. 8a-8c illustrate additional system features used to ensure a reliable barrier removal/disintegration process
• FIG. 9-14 illustrate use of pressure compensation systems in conjunction with a double barrier design further to a preferred embodiment.
• Such pressure compensation systems are used to provide for a lower pressure between the barrier elements than on the outside of the barrier elements, respectively;
• Fig. 15 illustrates a preferred design principle for barrier elements constituting the barrier
• Fig. 16a illustrates an exploded view of a barrier according to the present
• Fig. 16b illustrates the barrier in fig. 16a arranged in a portion of a pipe
• Fig. 16c illustrates the barrier in fig. 16b seen from the first portion of a wellbore.
• Fig. la-lc illustrate a borehole 101.
• Casing 102 is used to prevent the borehole 101 from collapsing during drilling and subsequent production, and to seal off the borehole wall to prevent unwanted leakage to or from strata/zones in the underground and ultimately to provide a barrier between the pressurized hydrocarbon reservoir and the open environment.
• the casing is cemented to the rock wall as will be appreciated by any person skilled in the art and thus not illustrated herein.
• a generic well completion is illustrated.
• the lower completion comprises a cemented production liner 103 which is open towards the hydrocarbon reservoir via perforations 104.
• the configuration of the production liner 103 may vary significantly from what is illustrated herein.
• the production liner 103 is anchored to and forms a seal towards the casing 102 by means of a liner hanger system 105.
• 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.
• the tubing 106 is terminated in the wellhead 110.
• the completion design may vary significantly from what is shown in fig. 1, and there are common completion components that are not illustrated herein, such as a downhole safety valve. These facts will be appreciated by a person skilled in the art.
• the device according to the present invention can be used for other completion designs than what is shown herein, and fig. 1 provides for an example only.
• the production packer 109 When running the completion in the hole, the production packer 109 is not activated, as illustrated in fig. la.
• the centerline 115 of the tubular is illustrated for reference.
• a pump 111 is put in fluid communication with the wellhead 110.
• the pump 111 is used to apply high pressure to the fluid inside the tubing 106. This is possible due to the sealed enclosure formed by the tubing 106, the sealing arrangement 108, the wellhead 110 and the pump 111.
• 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 on production or injection. To remove the barrier 114, the fluid inside the tubing 106 is pressure-cycled as described earlier in this document, using the pump 111.
• a mechanical counter mechanism 112 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. Fig. lc illustrates the well completion after the barrier 114 has been removed.
• 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.
• FIG. 2 shows in a larger scale one embodiment of the barrier 114 with an associated activation system 113 according to present invention.
• a counter system 112 as indicated in the figures la-lc or alternative systems for wireless activation of the barrier system not shown herein. However such a system is assumed included in the well completion, and in fluid communication with the activation system 113 through a flow channel 201.
• a mechanical counter system 112 upon activation, operates a valve manifold so that a pressurized fluid is lead into the activation system 113 through the flow channel 201. Details of operation of any mechanical counter system 112, or alternative wireless activation system, valve manifolds etc. is known to a person skilled in the art and not further described herein.
• the activation system 113 has a tubular form and is incorporated or connected the production tubing 106. Only one side of the cut activation system 113 is illustrated. The center of the cut activation system 113 is illustrated by the dotted line 115.
• the barrier 114 shown in fig. 2 is made up of smaller barrier elements some of which are indicated by reference numerals 114a, 114b, 114k.
• a relatively thin-walled base dome 114s made of a brittle material such as concrete is applied to simplify the construction of the barrier 114 and to prevent unwanted premature
• the barrier elements 114a, 114b, 114k are attached to the base dome 114s and/or each other by means of an adhesive agent, or using metal wire or other suitable attachment methods.
• a relatively thin walled ring (not illustrated herein) made of a similar brittle material is forming the circumference of the barrier 114 to facilitate mounting and provide inter-component stability of the barrier 114.
• 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.
• pressurized fluid is routed from a valve manifold operated as described elsewhere in the document and into the activation system 113 via channel 201.
• 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.
• 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 fig. 2.
• a thin walled dome 14s assists in holding the geometry of the barrier 114 stable.
• the ba rrier 114 is designed to hold forces from a direction illustrated by arrow 210.
• 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.
• the barrier 114 is in the embodiment shown provided with an elastomeric membrane 212.
• the elastomeric membrane 212 could be replaced with other coating agents suitable for forming a seal.
• a coating agent may be adhesives, resin coating or similar.
• the holding profile 204 is shifted simultaneously. After a certain travel, the holding profile 204 will no longer radially support the finger coupling 207.
• the fingers will be pushed radially outward and away from the centerline 115 of the tubing 106.
• the finger coupling 207 is formed so that the fingers bias towards a position that is radially outward into a recess 503 from the resting position when the barrier 114 is assembled.
• the push created by the pressure force indicated by arrow 210 acting on barrier 114 forces the fingers of the finger coupling 207 radially outward into the recess 503.
• a mechanical lock system will ensure that the lock/ cover mandrel is locked in place with respect to recess 503.
• a lock system is not shown, but may for example be a snap lock or other suitable locking device that will be appreciated by a person skilled in the art.
• the barrier 114 is now free to move further downwards in the tubing 106.
• the barrier 114 will now disintegrate due to forces caused by pressure according to arrow 210, associated flow forces, collisions with the wall of the tubing 106, or collision with other objects in the well.
• the smaller barrier elements 114a, 114b, 114k are free to move with respect to each other, or engaged to each other by means of relatively weak adhesive, thin metal wires, or other means that will disengage when relatively modest forces are acting on the barrier 114.
• a preferred embodiment of this is that the thin walled dome 114s and/or rim is made in a brittle material that will crush in the process subsequent to the radial disengagement of finger coupling 207.
• Fig. 5b illustrates the situation where the barrier 114 is in the process of disintegrating.
• 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 .
• Fig. 5c illustrates another preferred feature.
• the elastomeric membrane 212 is physically bonded to the cover mandrel 208 along its circumference 504.
• the barrier elements 114a, 114b, 114k etc will be physically separated from the elastomeric membrane 212.
• the elastomeric membrane 212 will ultimately be inverted and torn/permanently destructed from the fluid forces acting on it. This way, one avoids a potential problem of the mechanical parts such as barrier elements 114a, 114b, 114c and sealing parts such as the elastomeric membrane 212 of the barrier 114 being able to re-form a barrier seal elsewhere in the well.
• the bonding between elastomeric membrane 212 and cover mandrel 208 could be achieved by means of mechanical fixture means, adhesives, or by vulcanizing the elastomeric membrane 212 to cover mandrel 208.
• Fig. 6 illustrates a barrier system comprising two barriers 114, 601.
• Barrier 601 is added to enable the system to withstand forces and pressure according to a rrow 604.
• barrier 601 is held in place by holding sleeve 603 and wedge 602. Further to this embodiment, barrier 601 is removed as a consequence of removing or disintegrating barrier 114.
• barrier 601 will be exposed to the disintegrated barrier 114 and to fluid forces acting on barrier 601 from a direction indicated by arrow 210, where barrier 601 has a very limited pressure integrity.
• barrier 601 may be activated by a similar activation system and method as described in relation to figures 2-5.
• Such an activation mechanism could be independent to or form integral part of activation system 113.
• the lower of the two barriers i.e. barrier 601 is the one that is operated by the activation system 113 as discussed above.
• barrier system disclosed in fig. 6 is turned upside down.
• a relatively light fluid such as brine
• the lower barrier 601 must be removed prior to removing the upper barrier 114.
• barriers 114 and 601 are operated simultaneously when activating the activation system 113.
• barriers 114 and 601 are fully or partially merged into one structural element with a cavity inside of it.
• the barriers such as barrier 114 are prevented from disintegrating in the reverse direction from what is illustrated in fig. 5 by mechanical forces applied by such as finger coupling 207, holding sleeve 208 and elastomeric membrane 212. Also, in a preferred embodiment of the invention, barriers such as barrier 114 are further held in place by the aid of pressure forces acting on them via the elastomeric membranes such as elastomeric membrane 212. Further to fig. 6, this is achieved by always ensuring that there is a lower pressure between the barriers 114, 601 than there is on the top of barrier 114 and bottom of barrier 601, respectively. In one embodiment, this is achieved by having atmospheric pressure conditions in the area between the barriers 104, 601. By means, well pressure from above barrier 114 and below barrier 601 will keep the barriers in place until the activation system 113 is activated.
• 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.
• 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.
• 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.
• 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).
• 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.
• the barriers 114, 601 described in fig. 6 are supplemented with additional barriers 114', 601'. This may be required in cases where added safety and/or redundancy are needed.
• Fig. 8a illustrates an embodiment where the barriers 114, 601 are provided with rod elements 801, 802 that will apply push to the keystones 114k, 804 when one or both of the barriers 114, 601 are activated.
• the rods 801, 802 are replaced by cutting elements that will be forced up between, inside or through the barriers 114, 601 and through the elastomeric membranes such as elastomeric membrane 212.
• the intention with the design shown in fig. 8 is to prevent accidental occurrences where the barriers 114, 601 re-form stable barrier
• a cutting device will be deployed on wireline or coil tubing and applied to cut through the membrane 212.
• 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).
• this will disintegrate, too, for similar reasons, as the higher reservoir pressure will act on it in the reverse direction.
• the membrane 212 is mechanically protected or double barriers are applied (as described in relation to fig. 7).
• a spear device will be deployed on wireline or coil tubing and applied to crush the barrier 114.
• the wireline tool will be a combined cutting and spear device.
• the finger coupling 207 is different in form and function from what has been described above.
• two different profiles are supporting the barrier 114.
• the supporting profiles are lower support shoulder 805 and upper support shoulder 806.
• 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.
• the upper support shou lder 806 forms part of or is fixed to the tubing 106.
• the upper support shoulder 806 will oppose this, but further to a preferred embodiment, this shoulder is made so thin that the local compression forces on the barrier 114 where this is in contact with upper support shoulder 806 will cause the barrier 114 to deform or partly disintegrate along this surface. Upon this, the barrier 114 will be forced through upper support shoulder 806. In a preferred embodiment, this sequence of events will cause the barrier 114 to open in a fashion where the lower, now unsupported outskirts of the barrier 114 will be forced towards the tubing wall, and barrier 114 opens similarly to "a flower that is blooming". The intention with the features described above and indicated in fig.
• barrier 8b is to provide for as controlled a disintegration of barrier 114 as possible, and to avoid an accidental situation where the barrier 114 looses support, but does not disintegrate, and where it lands on a lower-lying shoulder (not shown) in the well and re-establishes as a stable structure.
• Fig. 8c illustrates the process of opening the barrier like a blooming flower in more detail.
• the lower support shoulder 805 shown in fig. 8b has been removed, and the barrier 114 now only rests 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 elements 114a, 114b, 114c to be forced outwards towards the tubing 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 from exposure to the fluid force 210.
• the barrier elements 114a, 114b, 114c will be forced outwards to such a degree that the "key stone" element 114k of the barrier elements can pass through the center of the barrier 114, as illustrated by arrow 810, whereupon the entire barrier structure will collapse.
• both the upper support shoulder 806 and lower support shoulder 805 are operable.
• both shoulders 806, 805 could be operable in a longitudinal direction of the well as indicated by arrow 808.
• 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.
• 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.
• an associated system component is introduced in the form of a pressure compensation system 901.
• the right side of the cut tubing is shown in a larger scale with respect to the barrier and pipe dimension.
• a main intention with a pressure compensation system is to balance pressure in the cavity 902 between barriers 114, 601 (the second portion of the wellbore) with respect to the pressure on the outside of the barriers 114, 601 (the first portion of the wellbore) . That way, the barriers 114, 601 may not be required to withstand as large forces as would be the case if there was atmospheric pressure inside cavity 902. This may entail the barriers 114, 601 to be built more slender. In some cases, the inclusion of pressure
• the illustrated pressure compensation system 901 balances the cavity 902 pressure with respect to tubing pressure above the barrier 114. In an alternative embodiment (not shown), the pressure compensation system 901 balances the pressure with respect to tubing pressure below barrier 601, or from the annulus between the tubing and the casing of the well.
• the pressure compensation system 901 is in fluid communication with the inside of the tubing via channel 903 and in fluid communication with the cavity 902 via channel 904. Channel 903 is in fluid contact with piston 905 which is supported by spring 906.
• 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.
• said temperature expansion is compensated for by allowing for a compensating travel of piston 905.
• 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.
• the pressure on top of barrier 114 and barrier 601, respectively, may vary with respect to each other.
• the completion equipment may be run in drilling mud, hence barrier 114 as well as barrier 601 may be exposed to pressures equal to the hydrostatic column of drilling mud when installed at depth.
• the mud may be displaced with so-called completion fluids, normally salt water, prior to setting the production packer and opening the barrier.
• completion fluids normally salt water
• the pressure on top of barrier 114 may now become significantly lower than the pressure below barrier 601. In other circumstances, other parameters may change this relation.
• the pressure inside cavity 902 which is the second portion of the wellbore as stated in the first aspect of the invention, always is lower than the pressure in the first portion of the wellbore, i.e. the pressure above barrier 114 and below barrier 601 as shown in the figures, during all relevant stages of the well completion process. Should the cavity 902 pressure exceed any of those pressures at any stage, this may entail leaks, and in worst case a premature disintegration of the barriers 114, 601.
• the piston 905 is provided with a stop rod 1001. After a certain travel of piston 905, the stop rod 1001 will abut against the bottom of the drilled bore 1002 and prevent the piston 905 from travelling further. Hence, the pressure inside cavity 905 will not increase as a function of deploying the barrier further into the well. This is illustrated in fig. 11.
• Fig. 12 illustrates a different approach to avoid over-pressurizing cavity 902.
• channel 903 is in fluid communication with the top of piston 905 via channel 1202 in plug 1201.
• Plug 1201 is provided with elastomeric seals in both ends.
• plug 1201 is attached to the tubing wall by means of shear pins 1203.
• the cavity 1204 formed by the right end of plug 1201 and the associated bore in the tubing, and sealed off by the right end seal of plug 1201, is i nitially housing a gas at near atmospheric pressure.
• the shear pins 1203 will shear at a certain depth, hence pressure due to forces generated by the pressure differential between cavity 1204 and the surrounding pressure.
• Fig. 14 illustrates an embodiment where the piston and plug mechanism is mi rrored above and below barriers 114 and 601, to compensate from both top and bottom of the barrier.
• the capacity of the shear pins 1203 in the upper piston and plug mechanism as shown in figure 13 may be equal to or different from the capacity of the shear pins for the mirrored piston and plug mechanism arranged below the barrier 601. The capacity may be selected depending on the given case specifications.
• Fig. 15 illustrates one method for defining the barrier elements of the barrier 114, some of which are indicated by reference numerals 114a, 114b, 114c, 114k.
• cuts are made in the concave lens shape of the barrier 114 from an imaginary point 1501 located somewhere on the center line axis 115 pointing straight out of the center of the barrier 114, i.e. the center axis 115 of the wellbore or tubular element (not shown) wherein the barrier 114 is mounted.
• 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.
• 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.
• 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.
• 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.
• 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 figures 16a-16c that will be discussed below.
• 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.
• 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.
• 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 fig. 2) in between and/or on the outskirts of the layer barrier elements, form the complete assembled barrier 114.
• 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.
• the smaller elements 114a, 114b, 114c, 114k are machined or manufactured in alternative known fashions.
• 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.
• the barrier elements may also be made of a material having a lower density than that of the fluid in the weiibore, if it is desired to prevent the disintegrated barrier elements to sinking in the well.
• Fig. 16 a-c illustrates further details of a design of the force bearing part of ba rrier 114 according to one embodiment of the present invention .
• Fig. 16a shows an exploded isometric view
• fig. 16b shows and isometric view of an assembled barrier 114 shown in fig. 16a
• fig. 16c shows a top view of the assembled barrier 114.
• the barrier 114 is made up of rings 1601-1604 cut in a concentric fashion, with an angle on the outskirts further to the logic as explained with respect to fig. 15.
• the rings 1601-1604 are radially cut in barrier elements 114a, 114b, 114c, 114k.
• the barrier elements in one ring are mounted with an angular displacement with respect to the barrier elements in adjoining ring(s). This way, for the embodiment shown, the splice between two barrier elements of ring 1601 meets the center of a barrier element in ring 1602 etc. This way, the barrier 114 becomes more physically stable.

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