P&a tool with collapsible state

Abstract

The present invention relates to a well tool device (1) for being lowered into a well (WE) from a starting location (L0) to a desired location (L1) in the well (WE) to form a permanent barrier at the desired location (L1). The starting location (L0) has a starting pressure and the desired location (L1) has an expected well pressure. The well tool device (1) comprises a housing (10), a heat generating mixture (21) located within the housing (10) and an igniter (25) for igniting the heat generating mixture (21). When the heat generating mixture (21) is ignited by the igniter (25), a heat generating process starts, causing materials of the surroundings (S) of the well tool device (1) in the well (WE) together with at least parts of the well tool device (1) to melt; whereafter the molten materials of the surroundings (S), the molten parts of the well tool device (1) and materials resulting from the heat generating process solidify to form a permanent barrier (PB) in the well (WE). The housing (10) comprises a housing section (11) comprising a housing sleeve (12) with a through bore (12a) in which at least a part of the heat generating mixture (21) is located, an upper housing closure (11U) for closing an upper end of the housing sleeve (12), a lower housing closure (11L) for closing a lower end of the housing sleeve (12). The well tool device (1) is configured to transition from an initial state at the starting location (L0) to a collapsed state at the desired location (L1). In the initial state, the pressure difference between an inside of the housing sleeve (12) and an outside of the housing sleeve (12) is insufficient to cause deformation of at least a part of the housing sleeve (12). In the collapsed state, the pressure difference between the inside of the housing sleeve (12) and the outside of the housing sleeve (12) is sufficient to cause deformation of at least a part of the housing sleeve (12).

Description

[0001] P&A tool with collapsible state

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a well tool device for being lowered into a well from a starting location to a desired location in the well to form a permanent barrier at the desired location.

[0004] BACKGROUND OF THE INVENTION

[0005] To meet governmental requirements during plugging and abandonment (P&A) operations in a well, a deep-set barrier must be installed as close to the potential source of inflow as possible, covering all leak paths. A permanent well barrier shall extend across the full cross section area of the well, including all annuli, and seal both vertically and horizontally in the well. Normally cement is used for the purpose of P&A operations.

[0006] Recently, an alternative method of performing P&A operations has been invented, using a heat generating mixture, e.g. a thermite mixture. This method is described in WO 2013 / 135583 where the method steps comprises providing an amount of a heat generating mixture, the amount being adapted to perform the desired operation, positioning the heat generating mixture at a desired position in the well, igniting the heat generating mixture, thereby melting the surrounding materials in the well.

[0007] In the thermite-based barrier formed by the method of WO 2013 / 135583, the heat generating mixture, e.g. the thermite mixture, when initiated, for example by ignition, will burn with a temperature of up to 3000°C and melt a great part of the proximate surrounding materials, with or without the addition of any additional metal or other meltable materials to the well. The surrounding materials may include any material normally present in the well, such as tubulars, e.g. casing, tubing and liner, cement, formation sand, etc. The heat from the ignited mixture will melt a sufficient amount of said materials. When the heat generating mixture has burnt out, the melted materials will solidify forming a sealing barrier comprising melted metal, cement, formation sand, etc. against the well formation.

[0008] The well tool for transporting the heat generating mixture into the well should store and protect its content until it has reached the intended position in the well. It was therefore believed that the tool must withstand the increasing ambient pressure exerted on it as it is lowered into the well. To withstand this ambient pressure, tools are typically made of expensive high strength materials or their wall thickness is increased, which require more material, which in turn increases cost. NO 20190537 describes a first solution to the above. The well tool here has a first compartment in which the heat generating mixture is located, and a second compartment separated from the first compartment by means of a partition device. The second compartment is exposed to the ambient pressure via a fluid line. The partition device may be a piston, a diaphragm or a bladder which moves and hence equalizes the pressure between the compartments as the well tools is lowered into the well.

[0009] NO 20210637 describes a second solution to the above. Here, the well tool has a downhole pressure equalizer formed by means of two pistons, an inner piston and an outer piston, located within the tool. Here, it was necessary to pressurize a piston compartment on one side of the pistons with a predetermined pressure, typically equal to the expected well pressure at the location of the heat generation process. This was typically performed topside before the well tool was lowered into the well.

[0010] NO 20210355 describes a well tool used to transport heat generating mixture into the well. Above the tool itself, a replenishment string is connected, in order to supply further amounts of heat generating mixture to the heat generating process. The replenishment string may comprise a number of sections connected to each other.

[0011] NO 20191143 describes that the well tool used to transport heat generating mixture into the well may comprise a housing made of aluminium, where the aluminium housing is a constituent of the heat generating mixture.

[0012] N020210353 describes discs of metal and metal oxide, where holes are provided centrally through these discs. These discs are then inserted onto a central carrying device such as a rod or wire etc. In this application, it was stated that the pyrotechnic mixture is forming a self-supported pyrotechnic structure and hence that the outer housing could be omitted. A non-supporting coating could be applied outside of the self-supported pyrotechnic structure.

[0013] NO 20201128 and NO 20201129 describe a well tool device for transporting heat generating mixture into the well. The tool has a lower sealing element which expands outwardly in a radial direction into contact with the well pipe, in order to prevent molten materials to flow down into the well. The tool also has an upper anchoring device which expands outwardly in a radial direction into contact with the well pipe, in order to prevent the tool to move upwardly during the heat generation process.

[0014] Interwell RockSolid™ is a well tool device for reinstating cap rock integrity across the entire cross section of the well. Information about this tool is available from the website interwell.com. The well tool device has a length of 702.0 cm and the housing in which the heat generating mixture is located must be pressurized topside to a predetermined pressure being dependent on the expected pressure at the location of the heat generating process.

[0015] One object of the present invention is to simplify the handling of the well tool topside, before lowering it into the well.

[0016] SUMMARY OF THE INVENTION

[0017] The present invention relates to a well tool device for being lowered into a well from a starting location to a desired location in the well to form a permanent barrier at the desired location, wherein the starting location has a starting pressure and the desired location has an expected well pressure, wherein the well tool device comprises:

[0018] - a housing;

[0019] - a heat generating mixture located within the housing;

[0020] - an igniter for igniting the heat generating mixture; wherein, when the heat generating mixture is ignited by the igniter, a heat generating process starts, causing materials of the surroundings of the well tool device in the well together with at least parts of the well tool device to melt; whereafter the molten materials of the surroundings, the molten parts of the well tool device and materials resulting from the heat generating process solidify to form a permanent barrier in the well; wherein the housing comprises a housing section comprising:

[0021] - a housing sleeve with a through bore in which at least a part of the heat generating mixture is located;

[0022] - an upper housing closure for closing an upper end of the housing sleeve;

[0023] - a lower housing closure for closing a lower end of the housing sleeve; characterized in that

[0024] - the well tool device is configured to transition from an initial state at the starting location to a collapsed state at the desired location; wherein, in the initial state, the pressure difference between an inside of the housing sleeve and an outside of the housing sleeve is insufficient to cause deformation of at least a part of the housing sleeve; wherein, in the collapsed state, the pressure difference between the inside of the housing sleeve and the outside of the housing sleeve is sufficient to cause deformation of at least a part of the housing sleeve.

[0025] According to the above, it is achieved that the inside of the housing sleeve does not need to be pressurized topside to a predetermined pressure. This will simplify the handling of the well tool device topside.

[0026] In addition, the housing sleeve does not need to be designed to withstand the pressure difference between the inside of the housing sleeve and the outside of the housing sleeve. Hence, the housing sleeve of can be made of a thinner layer of metal. One advantage of this thinner layer of metal is that the distance between the heat generating mixture on the inside of the housing sleeve and the well is reduced. Another advantage is that the amount of heat generating mixture per length unit of the well tool device is increased. Hence, the heat generating process may be more efficient.

[0027] The pressure difference between the inside of the housing sleeve and the outside of the housing sleeve in the collapsed state is insufficient to cause deformation of the upper housing closure and the lower housing closure.

[0028] The well tool device is defined with a longitudinal centre axis. As used herein, a longitudinal direction is a direction parallel with or aligned with the longitudinal centre axis. As used herein, a radial direction is a direction perpendicular to the longitudinal centre axis.

[0029] The housing sleeve may be configured to carry a first portion of a weight of the housing sleeve, the heat generating mixture and parts of the well tool device may be located below the housing section in both the initial state and in the collapsed state.

[0030] The portion of the weight carried by the housing sleeve may be more than 50%, preferably more than 70% and even more preferred 95-100%.

[0031] The housing section may comprise a pipe extending through the through bore between the upper housing closure and the lower housing closure.

[0032] The assembly of the housing may be more efficient due to the pipe.

[0033] The pipe may be configured to carry a second portion of the weight of the housing sleeve, the heat generating mixture and parts of the well tool device may be located below the housing section in both the initial state and in the collapsed state.

[0034] The portion of the weight carried by the pipe may be less than 50%, preferably less than 30% and even more preferred less than 5%. The housing section may be provided without such a pipe. In such a case, the portion of the weight carried by the housing sleeve may be 100%.

[0035] The upper housing closure and the lower housing closure may be sealingly engaged with the housing sleeve both in the initial state and in the collapsed state, and wherein the housing sleeve may be fluid-impermeable both in the initial state and in the collapsed state.

[0036] Hence, it is avoided that fluid from the well enters the through bore in the initial state and in the collapsed state. The heat generating mixture may comprise a particulate material compacted to one or more solid bodies fitted within the through bore and wherein the heat generating mixture may be limiting the deformation of the housing sleeve in the collapsed state.

[0037] As the heat generating mixture is fitted inside the through bore, and further as the heat generating mixture has been compacted, the volume of the heat generating mixture cannot be reduced much. Hence, the heat generating mixture will support the housing sleeve from the inside as the pressure difference between the inside of the housing sleeve and the outside of the housing sleeve gradually tries to deform the housing sleeve inwardly. Hence, after some deformation, the force applied by the heat generating mixture to the inside of the housing sleeve will be equal to the force caused by the pressure difference to the outside of the housing sleeve, and further deformation of the housing sleeve is prevented.

[0038] The heat generating mixture may comprise a metal oxide and a metal, wherein at least some of the metal may be provided as metal discs, wherein the metal discs may be limiting the deformation of the housing sleeve in the collapsed state. The metal discs may be ring-shaped metal discs.

[0039] The metal oxide may here be provided as a particulate material. The metal oxide may here be provided as a compacted particulate material. Some of the metal may also be provided as a particulate material mixed with the metal oxide.

[0040] The metal discs may be provided spaced apart from each other at intervals within the through bore and wherein the metal oxide may be provided within the through bore between the metal discs.

[0041] The metal discs may be provided spaced apart from each other at intervals in the longitudinal direction.

[0042] Hence, the heat generating mixture is formed as layers stacked above each other, where every second layer is mostly a metal oxide and every second layer is a metal.

[0043] The metal discs may be oriented in a radial plane perpendicular to a longitudinal centre axis of the well tool device.

[0044] The metal oxide may be provided as a particulate material compacted to one or more solid bodies. Each solid body of metal oxide may here have the shape of a cylinder with a through bore.

[0045] Hence, also the compacted bodies of metal oxide are limiting the deformation of the housing sleeve in the collapsed state.

[0046] Typically, the housing sleeve will be shaped as a cylinder and the through bore will be cylindrical. Typically, the solid bodies formed by compacting particulate material, either both the metal and the metal oxide or the metal oxide only, will have a cylindrical shape to fit inside the through bore. Typically, also the metal discs will have a circular or cylindrical shape to fit inside the through bore.

[0047] In the initial state, the solid bodies and the metal discs may have an outer diameter being from 90 % and up to 100% of the inner diameter of the housing sleeve.

[0048] The circular discs may have a height of 2 - 15 mm.

[0049] In the initial state, the entire housing sleeve will be aligned with the upper housing closure and the lower housing closure.

[0050] In the collapsed state, a middle portion of the housing sleeve may be out of alignment with the upper housing closure and the lower housing closure. The housing sleeve may here be considered to have a “banana” type of deformation.

[0051] In the collapsed state, the housing sleeve may have a smaller outer diameter than in the initial state or at least a part of the housing sleeve has been moved closer to the longitudinal centre axis of the well tool device. The housing sleeve may here be considered to have a “shrunk” type of deformation. The ratio of shrinkage may vary along the longitudinal direction of the housing sleeve. In the “shrunk” type of deformation, the volume within the housing sleeve in the collapsed state may be equal to, but will typically be smaller than, the volume within the housing sleeve in the initial state.

[0052] In the initial state, a volume of the heat generating mixture amounts to more than 90% of the volume of the bore, preferably more than 95%, even more preferred more than 97.5%.

[0053] In the initial state, a volume of gas within the bore amounts to less than 10 % of the volume of the bore, preferably less than 5%, even more preferred less than 2.5 %.

[0054] The housing section may be referred to as an upper housing section or a first housing section.

[0055] The well tool device may comprise a number of housing sections; the upper housing closure may be an upper connector of a first connector type; the lower housing closure may be a lower connector of a second connector type; wherein the upper connector of a first one of the upper housing sections may be connectable to the lower connector of a second one of the upper housing sections.

[0056] The first connector type may comprise a first cap body sealingly engaged with the upper end of the housing sleeve and wherein the second connector type may comprise a second cap body sealingly engaged with the lower end of the housing sleeve. Hence, fluid flow between the through bore and an outside of the housing section is prevented.

[0057] The first connector type may comprise a first collar protruding in a direction away from the housing sleeve, wherein the second connector type may comprise a second collar protruding in a direction away from the housing sleeve, wherein the first collar may be configured to be located circumferentially outside of or circumferentially inside of the second collar.

[0058] The first collar may be protruding from the first cap body. The first collar may be a cylinder protruding from the first cap body. The first collar and the first cap body may be provided as one single body. The first collar may be oriented parallel with the longitudinal center axis.

[0059] The second collar may be protruding from the second cap body. The second collar may be a cylinder protruding from the second cap body. The second collar and the second cap body may be provided as one single body. The second collar may be oriented parallel with the longitudinal center axis.

[0060] The well tool device may comprise a fastener for securing the first collar to the second collar.

[0061] The first collar may be sealingly engaged with the second collar. The first collar may be sealingly engaged with the second collar by means of a sealing element. The second connector type may comprise a further collar located radially inside of the second collar, wherein the first collar is configured to be located circumferentially outside of the further collar and circumferentially inside of the second collar. The first collar may be sealingly engaged with the further collar. The first collar may be sealingly engaged with the further collar by means of a sealing element. Alternatively, the first connector type comprises the further collar.

[0062] The collars together with the fastener are forming a mechanical connection system for mechanically connecting connectors of the first connector type and connectors of the second connector type to each other.

[0063] The first connector type and the second connector type may comprise a guiding system.

[0064] The guiding system may allow longitudinal relative movement between the first connector type and the second connector type. The guiding system may prevent rotational relative movement between the first connector type and the second connector type. The guiding system may ensure that the first connector type and the second connector type are rotationally aligned with each other before moving them towards each other. The guiding system may comprise one or more pins and one or more apertures adapted to receive the one or more pins. The first connector type may comprise a first electrical connector and the second connector type may comprise a second electrical connector for allowing an electrical signal or electrical power to be transferred between the first connector type and the second connector type.

[0065] The first electrical connector and the second connector type are forming an electrical connection system for electrically connecting connectors of the first connector type and connectors of the second connector type to each other.

[0066] The electrical connection system may comprise an electrical plug and an electrical socket adapted to receive the electrical plug. The plug may comprise one or more male connectors. The electrical socket may comprise one or more female connectors.

[0067] The housing may comprise two or more upper housing sections.

[0068] According to the above, it is achieved that the well tool device may be handled topside in the form of short modules, where the short modules may be connected to each other immediately before they are lowered into the well. In addition, well tool device may be transported from the manufacturing site to the well site in the form of short modules. This will simplify the handling of the well tool device topside. In addition, it will simplify the transportation of the well tool device. In addition, the number of modules connected to each other can be adjusted based on well parameters or requested end-results, such as a length of the permanent barrier required in the well.

[0069] The well tool device is defined with a longitudinal centre axis. As used herein, a longitudinal direction is a direction perpendicular to or aligned with the longitudinal centre axis. As used herein, a radial direction is a direction perpendicular to the longitudinal centre axis.

[0070] The well tool device may comprise one single igniter or more than one igniter. The one or more igniters may be located within one single upper housing section. Igniters may be located within more than one upper housing section.

[0071] The above upper housing sections may have a length of 50 - 200 cm.

[0072] Each upper housing section may comprise a signal wire may extend between the first electrical connector of the upper connector of the first connector type and the second electrical connector of the lower connector of the second connector type.

[0073] The signal wire may be used to transfer the electric signal and / or electric power between the first electrical connector and the second electrical connector. The upper housing section may comprise a channel extending in the longitudinal direction between the upper connector and the lower connector, wherein the signal wire may be located within the channel.

[0074] The channel may be proved as an aperture through the heat generating mixture.

[0075] The upper housing section may comprise a pipe extending in the longitudinal direction between the upper connector and the lower connector, wherein the channel may be provided as a bore through the pipe.

[0076] The housing may comprise a lower housing section, wherein the lower housing section comprises:

[0077] - a housing sleeve with a through bore in which a part of the heat generating mixture is located;

[0078] - an upper connector of the first connector type for closing an upper end of the second housing section, wherein the upper connector of the second housing section is connectable to the lower connector of a lowermost one of the upper housing sections;

[0079] - a lower closure for closing a lower end of the housing sleeve.

[0080] The lower housing section may be referred to as a second housing section.

[0081] The igniter may be located within the lower housing section.

[0082] The lower housing section may comprise a signal wire extending between its upper connector and the igniter.

[0083] The lower closure may comprise a tapered nose section. The lower closure may comprise a lid or cover secured to the lower end of the housing sleeve of the lower housing section. The lower closure may comprise a lower connector of the second type. The lower closure may form the lowermost part of the well tool device.

[0084] The lower closure may comprise a sealing element movable between a radially retracted state and a radially expanded state. In the radially expanded state, the sealing element may be brought into physical contact with an inner surface of the well. In the radially expanded state, the sealing element may prevent or at least considerably reduce molten material from flowing down in the well during the heat generation process.

[0085] The heat generating mixture located in the through bore of the housing sleeve of the lower housing section may be different from the heat generating mixture located in the through bore of the housing sleeve of the upper housing section.

[0086] The heat generating mixture of the lower housing section may have a different particle size and / or may have a different ratio between metal and metal oxide and / or may have different additives than the heat generating mixture of the upper housing section.

[0087] The heat generating mixture of the lower housing section may be easier to ignite than the heat generating mixture of the upper housing section. The heat generating mixture of the lower housing section may have a higher reaction rate than the heat generating mixture of the upper housing section.

[0088] This may ensure that the initial phase of the heat generating process is running as desired, i.e. that the heat generating process develops sufficient heat to ignite the heat generating mixture of the upper housing sections.

[0089] The through bore of the housing sleeve of the lower housing section may be pressurized to a predetermined pressure before lowering the well tool device into the well.

[0090] Also this may ensure that the initial phase of the heat generating process is running as desired, i.e. that the heat generating process develops sufficient heat to ignite the heat generating mixture of the upper housing sections.

[0091] The well tool device is intended for use in wells having a depth between 300 - 5000 meters below sea level, preferably between 300 - 3500 meters below sea level. The predetermined pressure may be independent of the expected pressure at the location of the heat generating process for wells having a depth between 0 - 2000 meters below sea level.

[0092] The predetermined pressure may be set to be independent of the expected pressure at the location of the heat generating process. In the present embodiment, the pressure is set to be 50 bar for wells between 300 - 3500 meters below sea level.

[0093] The lower housing section may have a length of 50 - 200 cm.

[0094] The well tool device may comprise a top section comprising:

[0095] - an upper connection interface located in the upper end of the top section;

[0096] - a lower connector of the second type located in the lower end of the top section; wherein the lower connector of the top section is connectable to the upper connector of an uppermost one of the upper housing sections.

[0097] The top section may comprise an ignition module connected to the igniter via the upper connectors of the first connector type, the lower connectors of the second connector type and the signal wires.

[0098] The ignition module may comprise a control unit for controlling the igniter. The ignition module may comprise a communication unit for receiving signals from the topside of the well and / or from sending signals to the topside of the well. The top section may comprise an anchoring device having a radially retracted state and a radially expanded state. The anchoring device is configured to be engaged with the inner surface of the well in the radially expanded state.

[0099] The anchoring device may be brought from the radially retracted state to the radially expanded state by a weight of the top section being located above the anchoring device.

[0100] The anchoring device may be brought from the radially retracted state to the radially expanded state by a spring.

[0101] The anchoring device may be maintained in its radially retracted state as long as the weight of the well tool device below the anchoring device is suspended from the anchoring device. Hence, when the well tool device has been supported on a base in the well, the weight is no longer suspended from the anchoring device and the spring may move the anchoring device to the radially expanded state.

[0102] The anchoring device may comprise a lower end section and an upper end section being longitudinally movable relative to each other. Guide members are provided between the lower end section and the upper end section for guiding their relative movement. The guide members may also be used to hang off at least parts of the weight below the lower end section in the upper end section.

[0103] The heat generation mixture and the heat generating process

[0104] As used herein, the term “heat generating mixture” is a mixture of a metal oxide of a first type of metal and a metal of a second type of metal, which when heated to an ignition temperature will react spontaneously in an exothermic and self-sustained chemical reaction where the metal oxide of the first type of metal is reduced to elementary metal and the metal of the second type of metal is oxidized to a metal oxide. This type of heat generating mixture is often referred to as thermite, and the heat generating reaction is often referred to as a thermite reaction.

[0105] The metal oxide may be ferric oxide and the metal may be aluminum: Fe2O3 + 2 Al 2 Fe + A12O3 + heat

[0106] The result is here iron, aluminum oxide and heat.

[0107] The metal oxide may be bismuth oxide and the metal may be aluminum: Bi2O3 + 2 Al -> A12O3 + 2Bi + heat

[0108] The result is here bismuth, aluminum oxide and heat.

[0109] It should be noted that there are several alternatives to the above. The metal may be magnesium Mg, calcium Ca and / or silicon Si in addition to, or as an alternative to aluminium Al. The metal oxide may be tin oxide, copper oxide etc. In addition, the heat generating mixture may comprise additives to improve the heat generating process.

[0110] As used herein, the term “materials of the surroundings of the well tool device” is used to denote parts of the well, such as casing, cement, gravel and / or sand etc., and possibly also parts of the formation radially outside of the casing and cement. Typically, it is desired to form the permanent barrier in a layer of cap rock of the formation, the cap rock itself being impermeable for the fluids located below the cap rock. Hence, the result of a heat generating process in this area will be a cap rock to cap rock permanent barrier extending across the whole cross -section of the well.

[0111] It should be noted that there may be two or more casings outside of each other. The annulus between the casings may be fluid-filled, filled with cement, gravel or other materials.

[0112] At least parts of the well tool device may be made of the metal reacting with the metal oxide. The housing sleeve of the upper housing section and / or the housing sleeve of the lower housing section may be made the metal or an alloy thereof.

[0113] The housing sleeve of the upper housing section and / or the housing sleeve of the lower housing section may be extruded from a body of aluminum or an alloy thereof.

[0114] The housing sleeve of the upper housing section and / or the housing sleeve of the lower housing section may be cylindrical, i.e. have a circular cross section. Alternatively, the cross section may be oval, polygonal etc.

[0115] The housing section may be referred to as a first housing section;

[0116] - the housing sleeve and the upper and lower housing closures of the first housing section may be forming a pressure-tight compartment in which the heat generating mixture may be located;

[0117] - the well tool device may comprise a second housing section located above or below the first housing section, wherein the second housing section may comprise a housing sleeve with a through bore in which at least a part of the heat generating mixture may be located, an upper housing closure for closing an upper end of the housing sleeve and a lower closure for closing a lower end of the second sleeve;

[0118] - the upper housing closure and the lower closure of the second housing section may be sealingly engaged with the housing sleeve both in the initial state and in the collapsed state, and wherein the housing sleeve of the second housing section may be fluid-impermeable both in the initial state and in the collapsed state;

[0119] - the housing sleeve, the upper housing closure and the lower closure of the second housing section may be forming a pressure-tight compartment in which the heat generating mixture is be located; wherein the igniter may be located in the pressure-tight compartment of the second housing section.

[0120] When the well tool device is in the initial state, the pressure inside the pressure- tight compartment of the first housing section may be substantially the same as ambient pressure at the starting location.

[0121] When the well tool device is in the initial state, the pressure inside the pressure- tight compartment of the second housing section may be above ambient pressure at the starting location.

[0122] When the well tool device is in the initial state, the pressure inside the pressure- tight compartment of the second housing section may be substantially the same as ambient pressure at the starting location.

[0123] The heat generating mixture may comprise a metal oxide and a metal, wherein at least some of the metal may be provided as metal discs, the metal discs may be provided spaced apart from each other at intervals within the through bore of the first and second housing sections and wherein the metal oxide may be provided within the through bore between the metal discs, and wherein the thickness of the metal discs in at least a portion of the second housing section may be greater than the thickness of the metal discs in the first housing section and / or the spacing between the metal discs in at least a portion of the second housing section may be smaller than the spacing between the metal discs in the first housing section.

[0124] The heat generating mixture in the second housing section may comprise a metal oxide and a metal, wherein at least some of the metal may be provided as metal discs, the metal discs may be provided spaced apart from each other at intervals within the through bore of the second housing section and wherein the metal oxide may be provided within the through bore between the metal discs, and wherein the thickness of the metal discs in a portion of the through bore adjacent to one or both of the upper or lower housing closures of the second housing section may be greater than the thickness of the metal discs in the remainder of the through bore of the second housing section and / or the spacing between the metal discs in a portion of the through bore adjacent to one or both of the upper or lower housing closures of the second housing section may be smaller than the spacing between the metal discs in the remainder of the through bore of the second housing section.

[0125] The heat generating mixture in the second housing section may comprise a metal oxide and a metal, wherein at least some of the metal may be provided as metal discs, the metal discs may be provided spaced apart from each other at intervals within the through bore of the second housing section and wherein the metal oxide may be provided within the through bore between the metal discs, and wherein the thickness of the metal discs in a portion of the through bore adjacent to one or both of the upper or lower housing closures of the second housing section may be greater than the thickness of the metal discs in the remainder of the through bore of the second housing section and / or the spacing between the metal discs in a portion of the through bore adjacent to one or both of the upper or lower housing closures of the second housing section may be smaller than the spacing between the metal discs in the remainder of the through bore of the second housing section.

[0126] The heat generating mixture in the lower housing section may comprise a metal oxide and a metal, wherein at least some of the metal may be provided as metal discs, the metal discs may be provided spaced apart from each other at intervals within the through bore of the second housing section and wherein the metal oxide may be provided within the through bore between the metal discs, at least some of the metal discs each having an aperture, the apertures may be aligned to form a passage in which the igniter may be located, and wherein the thickness of the metal discs with apertures in which the igniter may be located may be greater than the thickness of the remainder of metal discs and / or the spacing between the metal discs with apertures in which the igniter may be located may be smaller than the spacing between the remainder of the metal discs.

[0127] The present invention also relates to a method of forming a permanent barrier in a well at a desired location using a well tool device comprising:

[0128] - a housing;

[0129] - a heat generating mixture located within the housing;

[0130] - an igniter for igniting the heat generating mixture; the housing comprising a housing section comprising:

[0131] - a housing sleeve enclosing a through bore;

[0132] - an upper housing closure for closing an upper end of the housing sleeve;

[0133] - a lower housing closure for closing a lower end of the housing sleeve;

[0134] - the upper housing closure and the lower housing closure being sealingly engaged with the housing sleeve and closing the through bore to form fluid tight compartment in which at least a part of the heat generating mixture is located, the pressure inside the compartment being substantially equal to the ambient pressure at a starting location and the compartment having a starting volume at the starting location; wherein the method comprises:

[0135] - lowering the well tool device into the well from the starting location to the desired location, the ambient pressure at the desired location being higher than the ambient pressure at the starting location;

[0136] - allowing the housing sleeve to deform to a collapsed state in which the volume of the compartment is lower than the starting volume, the upper housing closure and lower housing closure remaining in sealing engagement with the housing sleeve so that the compartment remains fluid tight during and after deformation of the housing sleeve;

[0137] - using the igniter to ignite the heat generating mixture to start a heat generating process, the heat generating process causing materials of the surroundings of the well tool device in the well together with at least parts of the well tool device to melt; and

[0138] - allowing the molten materials of the surroundings, the molten parts of the well tool device and materials resulting from the heat generating process to solidify to form a permanent barrier in the well.

[0139] BRIEF DESCRIPTION OF FIGURES

[0140] Embodiments of the invention will be described, by way of example, with reference to the following drawings, in which;

[0141] Fig. la schematically illustrates the well tool device at an initial location in the well;

[0142] Fig. lb schematically illustrates the well tool device at a desired location in the well before the heat generating process starts;

[0143] Fig. 1c illustrates the permanent barrier formed as a result of the heat generating process;

[0144] Fig. 2a is a side view of the well tool device;

[0145] Fig. 2b is a cross sectional view of the well tool device;

[0146] Fig. 3 is a perspective cross sectional view of a first embodiment of the upper housing section;

[0147] Fig. 4 is a cross sectional view of a second embodiment of the upper housing section;

[0148] Fig. 5a is a perspective view of the first connector type;

[0149] Fig. 5b is a perspective cross sectional view of the first connector type;

[0150] Fig. 6a is a perspective view of the second connector type;

[0151] Fig. 6b is a perspective cross sectional view of the second connector type;

[0152] Fig. 7 is a perspective cross sectional view of a first embodiment of the lower housing section;

[0153] Fig. 8 is a side view of an anchor device of the top section in the radially retracted state;

[0154] Fig. 9 is a side view of the anchor device of the top section in the radially expanded state;

[0155] Fig. 10 is a first image of a part of an upper housing section in the collapsed state;

[0156] Fig. 11 is a second image of a part of an upper housing section in the collapsed state Fig. 12 is a cross sectional view of the upper housing section and the lower housing section, wherein layers of metal oxide and metal are shown;

[0157] Fig. 13 is an enlarged view of the lower part of the lower housing section, wherein layers of metal oxide and metal are shown.

[0158] Common reference numerals are used throughout the figures to indicate similar features.

[0159] DETAILED DESCRIPTION

[0160] Referring to Figs, la-lc, a well tool device 1 is shown at different stages of operation within a well WE. In Fig. la, the well tool device 1 is at an initial location L0 within the well WE. The well WE comprises an inner casing IC, cement CE located outside of the inner casing IC and a cap rock CR outside of the cement. The inner casing IC, cement CE and possibly also parts of the cap rock CR are referred to as the surroundings S of the well tool device 1 at a desired location LI. It should be noted that these surrounds S comprise other materials than those shown in fig. la.

[0161] The well tool device 1 comprises a top section 50, a housing 10, which has multiple (in the present embodiment two) upper housing sections 11 and a lower housing section 15, and a lower closure 60. These components are arranged vertically below each other.

[0162] In Fig. lb, the well tool device 1 has been lowered to a desired location LI within the well WE. At this location, a heat generating process can be initiated. The desired location is typically a location with a co-called cap rock CR. Here, heat generating mixture 21 located within the housing 10 is ignited by an igniter 25. This ignition starts a heat generating process, causing materials S of the surroundings of the well tool device 1 in the well WE, together with at least parts of the well tool device 1, to melt.

[0163] In Fig. 1c, the result after the well tool device 1 has been activated at the desired location LI is shown. The molten materials S, the molten parts of the well tool device 1, and materials resulting from the heat generating mixture 21 have solidified to form a permanent barrier in the well WE. This barrier extends across the entire cross-section of the well WE, effectively sealing it. As the barrier is provided in the cap rock, the cap rock together with the permanent barrier will prevent leakages of oil and / or gas from a location below the barrier to a location above the barrier. In the present embodiment, the heat generating mixture 21 is a mixture of a metal oxide 21a (see fig. 4 and fig. 6) of a first type of metal and a metal 21b (see fig. 4 and fig. 6) of a second type of metal, which when heated to an ignition temperature will react spontaneously in an exothermic and self-sustained chemical reaction where the metal oxide of the first type of metal is reduced to elementary metal and the metal of the second type of metal is oxidized to a metal oxide. This type of heat generating mixture is often referred to as thermite, and the heat generating reaction is often referred to as a thermite reaction.

[0164] In the present embodiment, the metal oxide is bismuth oxide and the metal is aluminum:

[0165] Bi2O3 + 2 Al -> A12O3 + 2Bi + heat

[0166] The result is here bismuth, aluminum oxide and heat.

[0167] Referring to Fig. 2a and Fig. 2b, the well tool device 1 is shown more in detail. It should be noted that the well tool device 1 in fig. 2a and fig. 2b has three upper housing sections 11, indicated as reference numbers I la, 11b, 11c.

[0168] The top section 50 includes an upper connection interface CI located in the upper end of the top section 50, and a lower connector 50L located in the lower end of the top section 50. The lower connector 50L of the top section 50 is connectable to the upper end of an uppermost one of the upper housing sections 11.

[0169] The top section 50 of the well tool device 1 comprises an ignition module 27. The igniter 25 is here located in the lower housing section 15. The ignition module 27 is connected to the igniter 25 via signal wires 26 extending from the ignition module 27 and further down through the upper housing sections 11 and to the igniter 25 of the lower housing section 15. The ignition module 27 comprises a control unit for controlling the igniter 25. The ignition module 27 may also comprise a communication unit for receiving signals from the topside of the well WE and / or for sending signals to the topside of the well WE.

[0170] The top section 50 is also shown with an anchoring device 55. The anchoring device 55 will be described further in detail below with reference to fig. 8 and fig. 9.

[0171] As shown in fig. 2 and fig. 2b, the upper housing sections 11 are connected to each other below the top section 50, and the lower housing section 15 is connected below the upper housing sections 11. The lower closure 60 is connected to the lower end of the lower housing section 15.

[0172] The lower closure 60 comprises a tapered nose section 61 at its lowermost point. Above the tapered nose section 61, the lower closure 60 includes a sealing element 62. The sealing element 62 is movable between a radially retracted state and a radially expanded state. In the radially expanded state, the sealing element 62 may be brought into physical contact with an inner surface of the well WE. The lower closure 60 shown in fig. 2b is considered to be prior art (for example from NO 20201128 and NO 20201129) and will not be described further in detail herein. When expanded, the sealing element 62 may prevent or at least considerably reduce molten material from flowing down in the well during the heat generation process.

[0173] Referring to Figs. 3-4, each upper housing section 11 of the well tool device 1 comprises a housing sleeve 12 with a through bore 12a. The housing sleeve 12 is cylindrical and may be extruded from a body of aluminum or an alloy thereof. Hence, the material of the housing sleeve 12 is made of the metal 21b being a part of the heat generating process, and will preferably be consumed as part of the heat generating process. Within the through bore 12a, at least a part of the heat generating mixture 21 is located.

[0174] The upper housing section 11 further comprises an upper connector 11U of a first connector type 30 for closing an upper end of the housing sleeve 12, and a lower connector 1 IL of a second connector type 40 for closing a lower end of the housing sleeve 12. The upper connector 11U of a first one 1 la of the upper housing sections 11 is connectable to the lower connector 1 IL of a second one 1 lb of the upper housing sections 11. This allows for the modular assembly of multiple upper housing sections 11, enabling the well tool device 1 to be customized to the specific requirements of the well WE.

[0175] It should be noted that the upper connector 11U and the lower connector 1 IL serves two purposes - closing of the bore 12a and enabling that several housing sections can be connected to each other. In some embodiments, the upper connector 11U and the lower connector 1 IL serves only the purpose of closing of the bore 12a.

[0176] The upper housing section 11 comprises a pipe 18 extending in the longitudinal direction between the upper connector 11U and the lower connector 1 IL. A channel 19 is provided as a bore through the pipe 18 serving as a conduit for a signal wire 26.

[0177] At least some of the metal 21b is provided as metal discs fitted within the through bore 12a. These metal discs are spaced apart from each other at intervals within the through bore 12a. The metal oxide 21a is provided within the through bore 12a between the metal discs as shown in fig. 4. This arrangement forms a layered structure of the heat generating mixture 21, with alternating layers of metal oxide 21a and metal 21b.

[0178] The metal discs 21b are oriented in a radial plane perpendicular to a longitudinal center axis LCA of the well tool device 1. The metal oxide 21a is provided as a particulate material that has been compacted to form one or more solid bodies. These solid bodies of metal oxide 21a are also fitted within the through bore 12a.

[0179] Typically, the housing sleeve 12 is shaped as a cylinder and the through bore 12a is cylindrical. The solid bodies formed by compacting the particulate material, either both the metal 21b and the metal oxide 21a or just the metal oxide 21a, will have a cylindrical shape to fit inside the through bore 12a. Similarly, the metal discs will typically have a circular or cylindrical shape to fit inside the through bore 12a.

[0180] In fig. 4, the solid bodies and the metal discs may have an outer diameter D21a, D21b that is up to 100% of the inner diameter D12 of the housing sleeve 12. This close fit ensures that the heat generating mixture 21 is securely contained within the housing sleeve 12 and contributes to the structural integrity of the upper housing section 11. Similarly, there is a close fit between the pipe 18 and the metal 21b radially outside of the pipe 18 and between the pipe 18 and the metal oxide 21b radially outside of the pipe 18.

[0181] Referring to Figs. 5a-5b, the first connector type 30 is shown in detail. The first connector type 30 comprises a first cap body 31 that is sealingly engaged with the upper end of the housing sleeve 12. This engagement prevents fluid flow between the through bore 12a and the outside of the housing section 11, ensuring that the heat generating mixture 21 is securely contained within the housing sleeve 12. The first cap body 31 may be sealingly engaged with the housing sleeve 12 by means of a threaded connection. A sealing element such as an O-ring may also be provided between the first cap body 31 and the housing sleeve 12.

[0182] The first connector type 30 also includes a first collar 33 that protrudes in a direction away from the housing sleeve 12. This first collar 33 is a cylinder that protrudes from the first cap body 31 and is oriented parallel with the longitudinal center axis LCA. The first collar 33 and the first cap body 31 may be provided as a single body, simplifying the construction of the well tool device 1. However, as shown in fig. 5a, the first collar 33 may be formed by several bodies. Here it is shown that first collar 33 comprises a main collar body 31c which is formed as one single body together with the first cap body 31. In addition, the first collar 33 comprises a first ring 32rl and a second ring 32r2 provided radially outside of the main collar body 3 Irl .

[0183] It is further shown that the first connector type 30 comprises three guiding pins 35 and a first electrical connector 36 comprising multiple male connectors.

[0184] Referring to Figs. 6a-6b, the second connector type 40 is shown in detail. The second connector type 40 comprises a second cap body 41 that is sealingly engaged with the lower end of the housing sleeve 12. This engagement prevents fluid flow between the through bore 12a and the outside of the housing section 11, ensuring that the heat generating mixture 21 is securely contained within the housing sleeve 12. The second cap body 41 may be sealingly engaged with the housing sleeve 12 by means of a threaded connection. A sealing element such as an O-ring may also be provided between the second cap body 41 and the housing sleeve 12.

[0185] The second connector type 40 also includes a second collar 43 that protrudes in a direction away from the housing sleeve 12. This second collar 43 may be a cylinder that protrudes from the second cap body 41 and is oriented parallel with the longitudinal center axis LCA. The second collar 43 and the second cap body 41 may be provided as a single body, simplifying the construction of the well tool device 1. The second collar 43 has an outer diameter being equal to the outer diameter of the outer housing sleeve 12.

[0186] The second connector type 40 also comprises a further collar 44 positioned radially inside of the second collar 43. This arrangement creates an annular space between the further collar 44 and the second collar 43. The further collar 44 also extends in a direction away from the housing sleeve 12, parallel to the longitudinal center axis LCA of the well tool device 1.

[0187] The annular space between the further collar 44 and the second collar 43 of the second connector type 40 are adapted to receive the first collar 33 of the first connector type 30 when two housing sections are connected to each other. This configuration may provide additional stability and alignment to the connection between housing sections. The annular space between the further collar 44 and the second collar 43 may accommodate a sealing element 8, which can help ensure a fluid-tight connection between housing sections.

[0188] The second connector type 40 comprises three apertures 45 provided in the end surface of the further collar 44. The three apertures 45 are adapted to receive the three pins 35. Together, the three apertures 45 and the three pins 35 are forming a guiding system. This guiding system may allow longitudinal relative movement between the first connector type 30 and the second connector type 40, while preventing rotational relative movement between them. This ensures that the first connector type 30 and the second connector type 40 are correctly rotationally aligned with each other before they are moved towards each other.

[0189] The second connector type 40 comprises a second electrical connector 46 comprising multiple female connectors adapted to receive the male connectors of the first electrical connector 36. Together, the first electrical connector 36 of the first connector type 30 and the second electrical connector 46 of the second connector type 40, forms an electrical connection system. This system allows an electrical signal and / or electrical power to be transferred between the first connector type 30 and the second connector type 40, enabling the control and ignition of the heat generating mixture 21.

[0190] It should be noted that the guiding system formed by the three apertures 45 and the three pins 35 are initially used to rotationally align the different modules relative to each other, before the two connector types 30, 40 are moved longitudinally together. This ensures that the electrical connection system formed by the first electrical connector 36 and the second electrical connector 46 are rotationally aligned and hence becomes correctly assembled. As the two connector types 30, 40 are moved longitudinally together, the first collar 33 is moved into the annular space between the further collar 44 and the second collar 43.

[0191] The well tool device 1 may comprise a fastener 9 for securing the first collar 33 to the second collar 43. This fastener 9, in conjunction with the collars 33, 43, forms a mechanical connection system for mechanically connecting connectors of the first connector type 30 and connectors of the second connector type 40 to each other.

[0192] It should be noted that the signal wire 26 or signal wires 26 connected between the multiple female connectors and the multiple male connectors of the same upper housing section 11 are not shown in fig. 5b and fig. 6b.

[0193] Referring to Fig. 7, the lower housing section 15 of the well tool device 1 is shown in detail. Initially, it should be noted that the lower housing section 15 has many similarities with the upper housing section 11. Hence, not all details of the lower housing section 15 will be repeated below, as they are considered to be described above in relation to the upper housing section 11 above.

[0194] The lower housing section 15 comprises a housing sleeve 16 with a through bore 16a. The housing sleeve 16 is cylindrical and may be extruded from a body of aluminum or an alloy thereof. Hence, the material of the housing sleeve 16 is made of the metal 21b being a part of the heat generating process, and will preferably be consumed as part of the heat generating process.

[0195] The lower housing section 15 further comprises an upper connector 15U of the first connector type 30 for closing an upper end of the housing sleeve 16, and a lower closure 60 (shown in fig. 2a and fig. 2b, but not shown in fig. 7) for closing a lower end of the housing sleeve 16. The upper connector 15U of the lower housing section 15 is connectable to the lower connector 1 IL of a lowermost one of the upper housing sections 11.

[0196] As described above in relation to the upper housing the section 11, the upper connector 15U and lower closure 60 are sealingly engaged with the ends of the housing sleeve 16. This engagement prevents fluid flow between the through bore 16a and the outside of the housing section 15, ensuring that the heat generating mixture 21 is securely contained within the housing sleeve 16. The upper connector 15U and lower closure 60 may be sealingly engaged with the housing sleeve 16 by means of a threaded connection. A sealing element such as an O-ring may also be provided between the connector 15U / closure 60 and the housing sleeve 16.

[0197] The lower housing section 15 comprises the igniter 25 located near or at a distance from the lower end of the housing sleeve 16. The igniter 25 is used to initiate the heat generating process by igniting the heat generating mixture 21.

[0198] The lower housing section 15 comprises a signal wire 26 extending between its upper connector 15U and the igniter 25. The signal wire 26 is used to transfer the electric signal and / or electric power between the upper connector 15U and the igniter 25, enabling the control and ignition of the heat generating mixture 21.

[0199] Also here, the signal wire 26 is provided within a pipe 18 forming a channel 19 for the signal wire 26.

[0200] Within the through bore 16a, a part of the heat generating mixture 21 is located. The heat generating mixture 21 also here comprises a metal oxide 21a and a metal 21b. The heat generating mixture 21 located in the through bore 16a of the housing sleeve 16 of the lower housing section 15 is here different from the heat generating mixture 21 located in the through bore 12a of the housing sleeve 12 of the upper housing section 11. This difference may be in terms of particle size, the ratio between metal 21b and metal oxide 21a, and / or the presence of different additives.

[0201] This variation in the heat generating mixture 21 ensures that the initial phase of the heat generating process is running as desired, i.e., that the heat generating process develops sufficient heat to ignite the heat generating mixture 21 of the upper housing sections 11.

[0202] The igniter 25 is advantageously surrounded by heat generating mixture 21. Where the metal is provided in solid layers 21b, the igniter 25 is advantageously located within an aperture in each metal layer, the apertures being aligned to form a passage for the igniter 25. Similarly, where the metal oxide is provided as a plurality of solid bodies 21a formed by compacting particulate metal oxide, the igniter 25 is located within an aperture in each metal oxide body, the apertures being aligned to form a passage for the igniter 25. In this embodiment heat generating mixture surrounding the igniter comprises alternating metal discs 21b and metal oxide cylinders 21a all of which have a generally central generally circular aperture, the apertures being aligned to form a generally cylindrical passage in which the igniter 25 is located.

[0203] In the present embodiment, the through bores 12a of the upper housing sections 11 are not pressurized topside before lowering the well tool device 1 into the well. However, in this embodiment, the through bore 16a of the lower housing section 15 is pressurized to a predetermined pressure before lowering the well tool 1 device into the well. This is an advantage - only one of the housing sections needs to be pressurized, and there is no need to calculate pressure based on an expected pressure at the desired location LI .

[0204] It should be noted that contrary to the prior art Interwell RockSolid™ tool, the lower housing section 15 is pressurized to a predetermined pressure for a wide range of well depths. Tests of prototypes of the above embodiments indicate that a predetermined pressures of 50 bar and 10 bar can be used for wells having depths between 300 - 3500 meters (assuming that the well fluid has a density approximately equal to water). For wells with well fluids having densities different from water, the depth must be changed correspondingly. Pressurising the lower housing section 15 to 50 bar provides greater control of the heat generating process just after ignition, but requires the thickness of the housing sleeve 12 to be adequate to ensure that there is no deformation thereof before the well tool device 1 is lowered into the well. It has been found that the heat generating process can be adequately controlled with only 10 bar of pressure, and reducing the pressure in the lower housing section 15 to this level is advantageous as the thickness of the housing sleeve 12 can be reduced without any risk of deformation thereof before the well tool device 1 is lowered into the well.

[0205] Referring to Figs. 8-9, the top section 50 of the well tool device 1 includes an anchoring device 55. The anchoring device 55 is designed to secure the well tool device 1 within the well WE during the heat generating process. The anchoring device 55 is movable between a radially retracted state, as shown in Fig. 8, and a radially expanded state, as shown in Fig. 9.

[0206] In the radially retracted state, the anchoring device 55 has a smaller outer diameter, allowing the well tool device 1 to be freely moved within the well WE. In the radially expanded state, the anchoring device 55 has a larger outer diameter, enabling it to engage with the inner surface of the well WE and secure the well tool device 1 in place.

[0207] The anchoring device 55 comprises an upper end section 56ue and a lower end section 561e that are longitudinally movable relative to each other. Force transmitting elements 56gm are provided between the upper end section 56ue and the lower end section 561e to transfer forces between the upper end section 56ue and the lower end section 561e. Hence, the force transmitting elements 56gm are used to hang off at least parts of the weight of the well tool device 1 located below the lower end section 561e in the upper end section 56ue.

[0208] The anchoring device 55 further comprises a slips element 56a with a serrated surface for engaging with the inner surface of the well WE. The slips element 56a is pivotably connected to an upper arm 56b and a lower arm 56c. The upper arm 56b is pivotably connected at its lower end to an upper end of the slips element 56a, and at its upper end to an actuating sleeve 57. The lower arm 56c is pivotably connected at its upper end to a lower end of the slips element 56a, and at its lower end to the lower end section 561e. The actuating sleeve 57 comprises wheels 58 that facilitate the movement of the anchoring device 55 and hence of the well tool device 1 down into the well WE.

[0209] A spring 59 is connected between the actuating sleeve 57 and the upper end section 56ue. Relative movement between the actuating sleeve 57 and the lower end section 561e. The spring 59 provides a biasing force that tends to move the anchoring device 55 to the radially expanded state. However, when the weight of the well tool device 1 located below the anchoring device 55 is suspended from the anchoring device 55, the anchoring device 55 is maintained in its radially retracted state. When the well tool device 1 is supported on a base in the well WE, the weight is no longer suspended from the anchoring device 55, assisting the spring 59 to move the anchoring device 55 to the radially expanded state. This configuration simplifies the operation of the well tool device 1, as the transition between the retracted and expanded states of the anchoring device 55 is automatically controlled by the weight of the well tool device 1 and the biasing force of the spring 59. In order to maintain the anchoring device 55 in the radially retracted state during topside handling, i.e. when the top section 50 is oriented horizontally and there is no weight suspended from the lower end section 561e, a shear mechanism may be used to prevent movement of the actuating sleeve 57.

[0210] It should further be noted that the serrated surface of the slips element 56a is used to prevent upward movement of the well tool device 1 during the heat generation process.

[0211] Operation of the well tool device 1

[0212] Initially, the well tool device 1 is transported from the manufacturing site to the topside of the well WE in modules separated from each other. The well tool device 1 shown in fig. 2a and 2b has five modules: One top section 50, three upper housing sections I la, 11b and 11c and one lower housing section 15 to which the lower closure 60 has been connected. The height of the top section 50 is 1750 mm (including the height of the connection interface CL, the height of each upper housing section I la, 11b, 11c is 1545 mm and the height of the lower housing section 15 together with the lower closure 60 is 1735 mm. The outer diameter of the modules is the same, when assuming that the anchoring device 55 is radially retracted topside.

[0213] More efficient transportation and more efficient storage of the well tool device 1 is hence achieved. Manufacturing of the well tool device 1 is made more efficient, as the upper housing section 11 can be standardized, and the operator can select a first number of upper housing sections 11 for one well and a different number of upper housing sections 11 for a different well.

[0214] In some situations, it may be required to transport and store the igniter 25 as a separate module. It may also be required to transport and store the lower housing section 15 non-pressurized. When preparing the well tool device 1 topside, the lower closure 60 is disconnected from the lower housing section 15, the igniter 25 is inserted into, and is connected to the signal wire 26 of, the lower housing section 15. The lower closure 60 is re-connected to the lower housing section 15 again, and then the lower housing section 15 is pressurized to the predetermined pressure. The modules are then assembled into the well tool device 1 and is then lowered into the well WE as shown in fig. la.

[0215] At the starting location L0 the pressure difference between an inside of the housing sleeve 12 of the upper housing section 11 and an outside of the housing sleeve 12 of the upper housing section 11 is insufficient to cause deformation of at least a part of the housing sleeve 12. The well tool device 1 is here in an initial state. As the well tool device 1 is lowered towards the desired location LI, the pressure outside of the housing sleeve 12 of the upper housing section 11 will increase. At the desired location LI, the pressure difference between the inside of the housing sleeve 12 of the upper housing section 11 and the outside of the housing sleeve 12 of the upper housing section 11 is sufficient to cause deformation of at least a part of the housing sleeve 12 of the upper housing section 11. The well tool device 1 is here in a collapsed state. As the through bore 16a of the lower housing section 15 is pressurized, the housing sleeve 16 of the lower housing section 15 will typically be less deformed, or not deformed at all.

[0216] Referring to Fig. 10, the upper housing section 11 of the well tool device 1 is here shown in the collapsed state. The housing sleeve 12 was initially cylindrical, but has here deformed inwardly, reducing its outer diameter on at least some locations along the longitudinal direction. This deformation is limited by the heat generating mixture 21 located within the through bore 12a of the housing sleeve 12. As shown in fig. 10, the metal discs of the metal 21b limit the deformation of the housing sleeve 12 in the collapsed state more than the metal oxide 21a between the metal discs. Hence, the outer diameter of the housing sleeve 12 is larger at the positions of the metal discs of the metal 21b than at the positions of the metal oxide 21a. This inward deformation of the housing sleeve 12 may be considered a "shrunk" type of deformation. The ratio of shrinkage may vary along the longitudinal direction of the housing sleeve 12. In this "shrunk" type of deformation, the volume within the housing sleeve 12 in the collapsed state may be equal to, but will typically be smaller than, the volume within the housing sleeve 12 in the initial state. It should be noted that the deformation will progress gradually between the starting location L0 and the desired location LI. It should be noted that the housing sleeve 12 of the upper housing section 11 will carry most of the weight of the housing sleeve 12, the heat generating mixture 21, and parts of the well tool device 1 located below the upper housing section 11 in both the initial state and the collapsed state.

[0217] The upper connector 11U and the lower connector 1 IL of the housing sleeve 12 are sealingly engaged with the housing sleeve 12 both in the initial state and in the collapsed state. The housing sleeve 12 itself is also fluid-impermeable in both the initial state and in the collapsed state. As a result, the housing sleeve 12 may maintain its integrity and continue to securely contain the heat generating mixture 21 even in the collapsed state.

[0218] Referring to Fig. 11, the upper housing section 11 of the well tool device 1 is shown in a collapsed state. In the collapsed state, a middle portion of the housing sleeve 12 is here out of alignment with the lower connector 11U and the lower connector 1 IL, as indicated by the distance d between an alignment axis AA drawn between the lower connector 11U and the lower connector 1 IL and a central area of the housing sleeve 12. This misalignment may be due to the deformation of the housing sleeve 12 under the pressure difference between its inside and outside. The housing sleeve 12 may here be considered to have a "banana" type of deformation. It should be noted that in the collapsed state, the upper housing section 11 may have both a "banana" type of deformation and a "shrunk" type of deformation.

[0219] The heat generating process is described above with reference to fig. lb and 1c.

[0220] Alternative embodiments

[0221] In the above embodiment, ends of the pipe 18 is not connected to the lower connector 11U and / or the lower connector 11L. The housing sleeve 12 therefore carries all weight of the housing sleeve 12, the heat generating mixture 21, and parts of the well tool device 1 located below the respective upper housing sections 11, both in the initial state and in the collapsed state.

[0222] It should be noted that the pipe 18 is not an essential feature. The channel 19 for the signal wire 26 may be provided as a number of openings or apertures through the different layers of metal oxide 21a and metal 21b, where the openings or apertures are longitudinally aligned with each other. Also in this case, the housing sleeve 12 will carry all weight of equipment below the respective upper housing sections 11, both in the initial state and in the collapsed state.

[0223] In another embodiment, the pipe 18 could have its upper end connected to the lower connector 11U and its lower end connected to the lower connector 1 IL. In such a case, weight could be carried together by the pipe 18 and the housing sleeve 12. As mentioned above, where the heat generating mixture comprises metal discs, the metal discs can limit the deformation of the housing sleeve 12 in the collapsed state. The thickness of and / or the separation between the metal discs can therefore be used to control the amount of deformation of the housing sleeve 12, for example to ensure that the pressure integrity of each housing section 11, 15 is retained in the collapsed state. Moreover, the thickness of and / or the separation between the metal discs can be used to allow different amounts of deformation in different housing sections or in different parts of one housing section.

[0224] For example, excess deformation to any housing section containing an igniter 25 might damage the igniter 25 which can cause it to malfunction. In addition, in the event that once the well tool device 1 is in the desired location, the heat generating process does not occur, perhaps because of a fault with the igniter 25, it may be necessary to retrieve the tool and remove the igniter 25 from the housing section 15 to repair or replace it. Excessive deformation of the housing section may render this impossible.

[0225] It may therefore be desirable to allow for more deformation of any housing section 11 which does not contain an igniter and less deformation of any housing section 15 which does contain an igniter 25. This could be achieved by providing thicker and / or more closely spaced metal discs in each housing section 15 containing an igniter and thinner and / or less closely spaced metal discs in each housing section 11 which contains only heat generating mixture.

[0226] This is illustrated in fig. 12. Here it is shown that the metal discs 21b are both thicker and more closely spaced in the housing section 15 than in the housing section 11.

[0227] Equally, or alternatively, in some embodiments, within a housing section 15 containing an igniter 15, the metal discs around the igniter 25 might be thicker and / or more closely spaced than the metal discs in the remainder of the housing section 15. Moreover, in order to ensure that there is still a passage along which the igniter 25 can be extracted after retrieval of the well tool device 1, the metal discs from the igniter 25 and up to one of the housing closures 11U, 15U, 1 IL, 60 may be thicker and / or more closely spaced than the metal discs in the remainder of the housing.

[0228] This is illustrated in fig. 13. Here it is shown that the metal discs 21b are both thicker and more closely spaced in the specific part of the housing section 15 in which the igniter is located, than in other parts of the housing section 15. As mentioned above, the housing sections 11, 15are configured to be pressure tight before and after collapse. The fluid-tight seal between the housing sleeve 12, 16 and the housing closures 11U, 15U, 11L, 60 may be particularly vulnerable to damage which compromises the pressure integrity of the housing sections 11, 15 after collapse. To minimise this risk, it is possible to reduce the amount of deformation of the housing sleeve 12 at its ends, by providing thicker and / or more closely spaced metal discs at one or both ends of the housing sleeve 12, 16.

[0229] Moreover, if the heat generating mixture 21 does not completely fill the housing section, there could be a space within the through bore 12a, 16a of the housing sleeve 12, 16 at the uppermost end of the housing section 11, 15. This should be avoided as it would result in excessive deformation of the housing sleeve 12, 16 at or adjacent its uppermost end, which could compromise the integrity of the seal between the housing sleeve 12, 16 and the upper housing closure 11U, 15U. In one embodiment, therefore the space between the heat generating mixture 21 and the upper housing closure 11U, 15U is filled with a shim, advantageously a metal shim. The shim may be perforated. Alternatively, the thickness of the layer of heat generating mixture 21 directly adjacent to the upper housing closure 11U, 15U may be adjusted to ensure that there is no or negligible space between the heat generating mixture and the upper housing closure 11U, 15U. Whilst in the embodiment described above, the lower housing section 15 is pressurised, this need not be the case. For example, it may be possible to adjust the composition of the heat generating mixture so that the heat generating process after ignition is sufficiently controlled that lower housing section 15 can also be at ambient pressure when the well tool device 1 is in the starting location. It was noted above that when the through bore 16a of the lower housing section 15 is pressurized, the housing sleeve 16 of the lower housing section 15 will typically be less deformed, or not deformed at all. If the lower housing section 15 is not pressurized, it may be necessary to provide thicker and / or more closely spaced metal discs in the lower housing section 15 to achieve the same absence of or negligible deformation of the housing sleeve 16.

[0230] Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

[0231] It will be understood that the above description of a preferred embodiment is given by way of example only and that various modifications may be made by those skilled in the art. What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable modification and alteration of the above devices or methods for purposes of describing the aforementioned aspects, but one of ordinary skill in the art can recognize that many further modifications and permutations of various aspects are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the scope of the appended claims.

Claims

29CLAIMS1. A well tool device (1) for being lowered into a well (WE) from a starting location (L0) to a desired location (LI) in the well (WE) to form a permanent barrier at the desired location (LI), wherein the starting location (L0) has a starting pressure and the desired location (LI) has an expected well pressure, wherein the well tool device (1) comprises:- a housing (10);- a heat generating mixture (21) located within the housing (10);- an igniter (25) for igniting the heat generating mixture (21); wherein, when the heat generating mixture (21) is ignited by the igniter (25), a heat generating process starts, causing materials of the surroundings (S) of the well tool device (1) in the well (WE) together with at least parts of the well tool device (1) to melt; whereafter the molten materials of the surroundings (S), the molten parts of the well tool device (1) and materials resulting from the heat generating process solidify to form a permanent barrier (PB) in the well (WE); wherein the housing (10) comprises a housing section (11) comprising:- a housing sleeve (12) with a through bore (12a) in which at least a part of the heat generating mixture (21) is located;- an upper housing closure (11U) for closing an upper end of the housing sleeve (12);- a lower housing closure (1 IL) for closing a lower end of the housing sleeve (12); characterized in that- the well tool device (1) is configured to transition from an initial state at the starting location (L0) to a collapsed state at the desired location (LI); wherein, in the initial state, the pressure difference between an inside of the housing sleeve (12) and an outside of the housing sleeve (12) is insufficient to cause deformation of at least a part of the housing sleeve (12); wherein, in the collapsed state, the pressure difference between the inside of the housing sleeve (12) and the outside of the housing sleeve (12) is sufficient to cause deformation of at least a part of the housing sleeve (12).

2. The well tool device (1) according to claim 1, wherein the housing sleeve (12) is configured to carry a first portion of a weight of the housing sleeve (12), the heat generating mixture (21) and parts of the well tool device (1) being located below the housing section (11) in both the initial state and in the collapsed state.

3. The well tool device (1) according to claim 1 or 2, wherein the housing section (11) comprises a pipe (18) extending through the through bore (12a) between the upper housing closure (11U) and the lower housing closure (1 IL).

304. The well tool device (1) according to claim 3, wherein the pipe (18) is configured to carry a second portion of the weight of the housing sleeve (12), the heat generating mixture (21) and parts of the well tool device (1) being located below the housing section (11) in both the initial state and in the collapsed state.

5. The well tool device (1) according to any one of the above claims, wherein the upper housing closure (11U) and the lower housing closure (1 IL) are sealingly engaged with the housing sleeve (12) both in the initial state and in the collapsed state, and wherein the housing sleeve (12) is fluid-impermeable both in the initial state and in the collapsed state.

6. The well tool device (1) according to any one of the above claims, wherein the heat generating mixture (21) comprises a particulate material compacted to one or more solid bodies fitted within the through bore (12a) and wherein the heat generating mixture (21) is limiting the deformation of the housing sleeve (12) in the collapsed state.

7. The well tool device (1) according to any one of the above claims 1 - 5, wherein the heat generating mixture (21) comprises a metal oxide (21a) and a metal (21b), wherein at least some of the metal (21b) is provided as metal discs, wherein the metal discs are limiting the deformation of the housing sleeve (12) in the collapsed state.

8. The well tool device (1) according to claim 7, wherein the metal discs are provided spaced apart from each other at intervals within the through bore (12a) and wherein the metal oxide (21a) is provided within the through bore (12a) between the metal discs.

9. The well tool device (1) according to claim 7 or 8, wherein the metal discs are oriented in a radial plane perpendicular to a longitudinal centre axis (LCA) of the well tool device (1).

10. The well tool device (1) according to any one of claims 7 - 9, wherein the metal oxide (21a) is provided as a particulate material compacted to one or more solid bodies.

11. The well tool device (1) according to any one of the above claims, wherein:- the housing section (11) is referred to as a first housing section (11);- the housing sleeve (12) and the upper and lower housing closures (11U, 1 IL) of the first housing section (11) are forming a pressure-tight compartment in which the heat generating mixture is located;- the well tool device (1) comprises a second housing section (15) located above or below the first housing section (11), wherein the second housing section (15) comprises a housing sleeve (16) with a through bore (15a) in which at least a part ofthe heat generating mixture (21) is located, an upper housing closure (15U) for closing an upper end of the housing sleeve (16) and a lower closure (60) for closing a lower end of the second sleeve (16);- the upper housing closure (15U) and the lower closure (60) of the second housing section (15) are sealingly engaged with the housing sleeve (16) both in the initial state and in the collapsed state, and wherein the housing sleeve (16) of the second housing section (15) is fluid-impermeable both in the initial state and in the collapsed state;- the housing sleeve (16), the upper housing closure (15U) and the lower closure (60) of the second housing section (15) are forming a pressure-tight compartment in which the heat generating mixture is located; wherein the igniter (25) is located in the pressure-tight compartment of the second housing section (15).

12. The well tool device (1) according to claim 11 wherein when the well tool device (1) is in the initial state, the pressure inside the pressure-tight compartment of the first housing section (11) is substantially the same as ambient pressure at the starting location.

13. The well tool device (1) according to claim 12 wherein when the well tool device (1) is in the initial state, the pressure inside the pressure -tight compartment of the second housing section (15) is above ambient pressure at the starting location.

14. The well tool device (1) according to claim 12 wherein when the well tool device (1) is in the initial state, the pressure inside the pressure -tight compartment of the second housing section (15) is substantially the same as ambient pressure at the starting location.

15. The well tool device (1) according to any one of claims 11 -14 wherein the heat generating mixture (21) comprises a metal oxide (21a) and a metal (21b), wherein at least some of the metal (21b) is provided as metal discs, the metal discs are provided spaced apart from each other at intervals within the through bore (12a, 16a) of the first and second housing sections (11, 15) and wherein the metal oxide (21a) is provided within the through bore (12a, 16a) between the metal discs, and wherein the thickness of the metal discs in at least a portion of the second housing section (15) is greater than the thickness of the metal discs in the first housing section (11) and / or the spacing between the metal discs in at least a portion of the second housing section (15) is smaller than the spacing between the metal discs in the first housing section (11).

16. The well tool device (1) according to any one of claims 11 - 15 wherein the heat generating mixture (21) in the second housing section (15) comprises a metal oxide (21a) and a metal (21b), wherein at least some of the metal (21b) is provided asmetal discs, the metal discs are provided spaced apart from each other at intervals within the through bore (16a) of the second housing section (15) and wherein the metal oxide (21a) is provided within the through bore (16a) between the metal discs, and wherein the thickness of the metal discs in a portion of the through bore (16a) adjacent to one or both of the upper or lower housing closures of the second housing section (15) is greater than the thickness of the metal discs in the remainder of the through bore (16a) of the second housing section (15) and / or the spacing between the metal discs in a portion of the through bore (16a) adjacent to one or both of the upper or lower housing closures of the second housing section (15) is smaller than the spacing between the metal discs in the remainder of the through bore (16a) of the second housing section (16).

17. The well tool device (1) according to any one of claims 11 - 16 wherein the heat generating mixture (21) in the second housing section (15) comprises a metal oxide (21a) and a metal (21b), wherein at least some of the metal (21b) is provided as metal discs, the metal discs are provided spaced apart from each other at intervals within the through bore (16a) of the second housing section (15) and wherein the metal oxide (21a) is provided within the through bore (16a) between the metal discs, and wherein the thickness of the metal discs in a portion of the through bore (16a) adjacent to one or both of the upper or lower housing closures of the second housing section (15) is greater than the thickness of the metal discs in the remainder of the through bore (16a) of the second housing section (15) and / or the spacing between the metal discs in a portion of the through bore (16a) adjacent to one or both of the upper or lower housing closures of the second housing section (15) is smaller than the spacing between the metal discs in the remainder of the through bore (16a) of the second housing section (15).

18. The well tool device (1) according to any one of claims 11 - 16 wherein the heat generating mixture (21) in the lower housing section (15) comprises a metal oxide (21a) and a metal (21b), wherein at least some of the metal (21b) is provided as metal discs, the metal discs are provided spaced apart from each other at intervals within the through bore (16a) of the second housing section (15) and wherein the metal oxide (21a) is provided within the through bore (16a) between the metal discs, at least some of the metal discs each having an aperture, the apertures being aligned to form a passage in which the igniter (25) is located, and wherein the thickness of the metal discs with apertures in which the igniter (25) is located is greater than the thickness of the remainder of metal discs and / or the spacing between the metal discs with apertures in which the igniter is located is smaller than the spacing between the remainder of the metal discs.3319. A method of forming a permanent barrier in a well at a desired location (LI) using a well tool device (1) comprising:- a housing (10);- a heat generating mixture (21) located within the housing (10);- an igniter (25) for igniting the heat generating mixture (21); the housing (10) comprising a housing section (11) comprising:- a housing sleeve (12) enclosing a through bore (12a);- an upper housing closure (11U) for closing an upper end of the housing sleeve (12);- a lower housing closure (1 IL) for closing a lower end of the housing sleeve (12);- the upper housing closure (11U) and the lower housing closure (1 IL) being sealingly engaged with the housing sleeve (12) and closing the through bore (12a) to form fluid tight compartment in which at least a part of the heat generating mixture is located, the pressure inside the compartment being substantially equal to the ambient pressure at a starting location (L0) and the compartment having a starting volume (V0) at the starting location (L0); wherein the method comprises:- lowering the well tool device into the well (WE) from the starting location (L0) to the desired location (LI), the ambient pressure at the desired location being higher than the ambient pressure at the starting location (L0);- allowing the housing sleeve (12) to deform to a collapsed state in which the volume of the compartment is lower than the starting volume (V0), the upper housing closure (HU) and lower housing closure (HL) remaining in sealing engagement with the housing sleeve (12) so that the compartment remains fluid tight during and after deformation of the housing sleeve (12);- using the igniter to ignite the heat generating mixture (21) to start a heat generating process, the heat generating process causing materials of the surroundings (S) of the well tool device (1) in the well (WE) together with at least parts of the well tool device (1) to melt; and- allowing the molten materials of the surroundings (S), the molten parts of the well tool device (1) and materials resulting from the heat generating process to solidify to form a permanent barrier (PB) in the well (WE).

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