Thermal apparatus and associated methods

Abstract

Embodiments comprise a method of removing material at a well, involving progressively jetting heat along a helical path to heat a target material for removal. Embodiments of the method comprise material removal from a downhole well element, involving running in a downhole assembly with a downhole heating device comprising a fuel towards a target location. For example, such embodiments provide an alternative method for the removal of wellbore tubulars, using a rapid oxidation process to significantly alter the physical state of the tubular well element and reduce it to an oxide deviate, thereby facilitating an area where a more conventional barrier can be installed in the wellbore.

Claims

1. A well material removal apparatus for removing material at a well, the well material removal apparatus comprising a heating device for heating a target material, the heating device being a helical thermic lance configured to progressively jet heat along a helical path to heat the target material for removal, wherein the helical thermal lance is configured to jet heat laterally relative to a longitudinal axis of the heating device, the longitudinal axis being a central longitudinal axis along which the helix of the helical thermic lance extends.

2. The well material removal apparatus of claim 1, wherein the helical thermic lance comprises a helical housing.

3. The well material removal apparatus of claim 2, wherein the helical heating member comprises at least one or more of the following predetermined properties according to intended use: longitudinal separation between adjacent revolutions or turns; a heating member cross-section property/ies; helix pitch; helix diameter; heating member longitudinal length; helix angle.

4. The well material removal apparatus of claim 1, wherein the heating member comprises an expandable heating member, the heating member being at least one of: radially expandable; and longitudinally expandable.

5. The well material removal apparatus of claim 1, wherein the heating member comprises an inlet for receiving oxidant, and the apparatus comprises one or more valves for controlling the supply of oxidant to the heating member.

6. The well material removal apparatus of claim 1, wherein the heating device comprises a central passage located radially inwards of the heating member, wherein the central passage comprises an enclosed hollow central member defining a bore configured for the transmission of signals and/or materials therethrough.

7. The well material removal apparatus of claim 1, wherein the heating device comprises a plurality of heating members, wherein the heating members are arranged longitudinally coincident, with the heating members rotationally offset, such that the two or more heating members are arranged circumferentially around a plane perpendicular to the longitudinal axis.

8. The well material removal apparatus of claim 1, wherein the well material removal apparatus comprises a plurality of heating devices, wherein the plurality of heating devices are spaced longitudinally and are selectively independently controllable.

9. The well material removal apparatus of claim 1, wherein the apparatus is for downhole heating.

10. A method of removing material at a well, the method comprising progressively jetting heat along a helical path with a helical thermic lance configured to jet heat laterally relative to a central longitudinal axis along which a helical of the helical thermic lance extends to heat a target material for removal, wherein the helical thermic lance is configured to progressively jet the heat along a helical path such that heat is jetted laterally relative to a longitudinal axis of the well to progressively helically heat the target material.

11. The method of claim 10, wherein the method comprises transporting the heating device to or towards a target location; providing an oxidant at the target location; heating the target material at the target location to facilitate the removal of the target downhole material; and removing the target material.

12. The method of claim 11, wherein the target location is in a passage, the method comprising transporting the heating device in the passage to the target location.

13. The method of claim 10, wherein the method comprises heating with a plurality of heating members and selectively independently controlling the plurality of heating members.

14. The method of claim 10, wherein the method comprises transporting the heating device in a collapsed configuration to the target location and expanding the helical heating member at the target location.

15. The method of claim 10, wherein the method comprises downhole heating.

16. The method of claim 10, wherein the method comprises oxidizing the target material in an exothermic reaction and generating sufficient heat to heat additional target material sufficiently to propagate the oxidation process.

17. The method of claim 10, wherein the method comprises melting the target material.

18. A well material removal apparatus for removing material at a well, the well material removal apparatus comprising a heating device for heating a target material, the heating device being a helical thermic lance for progressively jetting heat along a helical path, the helical thermic lance being configured to jet heat laterally relative to a longitudinal axis of the well to progressively helically heat the target material for removal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a flow chart of a method in accordance with a first example;

(3) FIG. 2 is a schematic sectional side view of a portion of a well bore in accordance with a first example;

(4) FIG. 3 is a subsequent view of the portion of the well bore of FIG. 2;

(5) FIG. 4 is a subsequent view of the portion of the well bore of FIG. 3;

(6) FIG. 5 is a subsequent view of the portion of the well bore of FIG. 4;

(7) FIG. 6 is a subsequent view of the portion of the well bore of FIG. 5;

(8) FIG. 7 is a subsequent view of the portion of the well bore of FIG. 6;

(9) FIG. 8 is a schematic view of a helical thermic lance;

(10) FIG. 9 is a schematic view of the helical thermic lance of FIG. 8 in use in a first heating device;

(11) FIG. 10 is a schematic view of the helical thermic lance of FIG. 8 in use in a second heating device;

(12) FIG. 11a is a schematic view of a pair of helical thermic lances;

(13) FIG. 11b is a schematic view of three helical thermic lances;

(14) FIG. 11c is a schematic view of four helical thermic lances;

(15) FIG. 12 is a schematic view of an apparatus comprising a pair of second heating devices of FIG. 9;

(16) FIG. 13 shows an example of a surface equipment package for a downhole apparatus;

(17) FIG. 14 schematically illustrates a plurality of target locations for material heating and/or removal; and

(18) FIG. 15 is a flow chart of a method in accordance with another example.

DETAILED DESCRIPTION

(19) Referring first to FIG. 1, there is shown a flow chart depicting an example of a method 5 according to the present disclosure. The method 5 comprises a first step 10 of initiating oxidation; followed by a subsequent step 12 of oxidizing target material and a further step 14 of removing the oxidized target material.

(20) Here, the method 5 comprises downhole material removal from a downhole well element, the method comprising running in a downhole assembly with a downhole heating device comprising a fuel to or towards a target location. The method 5 comprises providing an oxidant at the target location; and oxidizing a target downhole material at a target downhole location to facilitate the removal of the target downhole material. In this method 5, the oxidized target downhole material is removed.

(21) In particular examples, the applicant has developed an alternative method for the removal of wellbore tubulars, using a rapid oxidation process to significantly alter the physical state of the tubular well element and reduce it to an oxide deviate thereby facilitating an area where, for example, a more conventional barrier can be installed in the wellbore.

(22) The rapid oxidation process of the tubular element occurs with the addition of a fuel, typically steel rods and an oxidizing agent such as oxygen. The process utilizes an initiator to initially raise the temperature to start the process off during which the fuel rapidly oxides in the presence of the oxygen, releasing heat as part of the highly exothermic reaction. In so doing the target material, such as the well bore tubular element, temperature raises and reaches a point whereby it also undergoes the same rapid oxidation process and is also oxidized. The resultant by-product of the reaction, metal oxide, can be then easily be removed, such as by conventional well techniques if necessary.

(23) After ignition, the introduced fuel and oxidizing agent will ignite, the reaction is exothermic in nature developing very high temperatures as part of the rapid oxidation process. The heat raises the surrounding target well element tubular temperature such that, in the presence of the introduced oxidizing agent, it will induce the well element to also undergo rapid oxidation.

(24) The reaction process is controlled by the control and supply of the oxidizing agent. The process can be regulated and stopped by the cessation of supply of the oxidizing agent, so enabling precise targeting of specific lengths and geometry of well bore tubular elements to be oxidized and so removed. After the reaction is complete the residual metal oxide can be removed from the well bore by conventional means.

(25) The method may further comprise the step of arranging an igniting head in connection with the fuel and oxidizing agent. The igniting head may be suitable for igniting the fuel and oxidizing agent.

(26) In some embodiments the method comprises the step of positioning at least one high temperature resistant element close to the target position in the well. The high temperature resistant element serves to protect parts of the well or well elements that lies above, below and/or contiguous to the target position. The high temperature resistant element may be made of high temperature resistant materials such as a ceramic element or a glass element. There may be arranged one or more high temperature resistant elements in the well.

(27) In at least some embodiments, the method comprises the steps of positioning the fuel material element in a container and lowering the container to the target position in the well by the use of coiled tubing or jointed pipe. Other methods can additionally or alternatively include positioning by wireline, slickline, cable or the like.

(28) The desired amount of fuel is prepared at the surface and positioned in a container. The fuel will typically consist of steel rods. The container may be any container suitable for lowering into a well. Dependent on the desired operation, the container, or a set of a number of containers, may be a short or a long container. In a P&A operation, where the need of a large section of target tubular element to be removed is desired, the set of container may be several meters, ranging from 1 meter to 1000 meters.

(29) In some embodiments, the method comprises the step of circulating the oxidizing agent material to the fuel in the container that has been positioned at the target tubular element position in the well. The oxidizing agent may be brought from the surface to the fuel position in the container in the well by circulation through coiled tubing or jointed pipe. The coiled tubing or jointed pipe may support the heating device and/or the container. Alternatively, the coiled tubing or jointed pipe may be discrete from the heating device and/or the container, such as where the heating device and/or container is located within the jointed pipe.

(30) In some embodiments, the invention relates to the use of a fuel and oxidizing mixture for the removal of well bore tubular elements by rapid oxidation of the target well bore tubular element, which may be a key process step in the overall abandonment of a well.

(31) Referring now to FIGS. 2, 3, 4, 5 and 6, there is shown sequentially a method of plugging a well for abandonment, the method comprising the oxidization and removal of target downhole material.

(32) FIG. 2 shows a schematic sectional side view of a portion of a well bore 20 in accordance with a first example. Here the well bore 20 comprises a series of successively narrower sections of casing or liner 22, 24, 26, 28, 30 extending from a platform wellhead deck towards a subsea well. The respective casings 22, 24, 26, 28, 30 terminate with a respective shoe 32, 34, 36, 38, 40 with each casing 22, 24, 26, 28, 30 having been cemented in place. The well bore 20 shown in FIG. 2 is a completed production well bore with a production tubing 42 accessing a production fluid zone 44 axially sealed from a first annulus by a packer 48. Here the production fluid zone 44 comprises a perforated liner 50 allowing flow from (and to) the surrounding formation. Although shown here in FIG. 2 relative to a platform well, it will be appreciated that other examples may be for other bores, such as subsea wells and/or onshore wells.

(33) Referring now to FIG. 3, there is shown the well bore 20 of FIG. 2 following processes prior to the material removal with a heating device. As can be seen here, the method comprises a prior operation of preparing the target location 52, involving a plugging operation prior to the material removal. As can be seen in FIG. 3, the method comprises a prior isolation operation by providing a cement plug 54 below the target location 52 to seal the perforated liner 50 in the production fluid zone 44. In addition, the method comprises providing a plug 56 to provide at least a temporary seal below the target location 52 to prevent or reduce undesired flow during the oxidation process. It will be appreciated that the plug 56 can provide support for the cement plug 54 on top; and, can provide a temporary barrier below the cement plug 54. As shown in FIG. 3, the downhole well element to be oxidized here is the production tubing 42, which forms the target material in this example.

(34) As shown in FIG. 3, there is provided a downhole apparatus 60 for the removal of downhole material. Here, the downhole apparatus 60 comprises a thermal or heating device, the heating device comprising a container for fuel and oxidizing agent. Here, the container comprises an inlet for connection to the coiled tubing 62, on which the downhole apparatus 60 has been run in to the target location 52. In at least some examples, the housing comprises a consumable sheath of a similar fuel material to steel and/or aluminium fuel rods housed therewithin. In at least some examples, the apparatus 60 comprises one or more valves for controlling the supply of oxidant to the downhole apparatus via the coiled tubing 62. In at least some examples the apparatus 60 comprises a controller for controlling the supply of fuel and/or oxidant to and/or from the downhole apparatus 60. Here, the downhole apparatus 60 is connected uphole to surface via the coiled tubing 62. Here, the apparatus 60 comprises an initiator for initiating the heating device with an ignition head comprising a charge. Although not shown in FIG. 3, in some examples the downhole apparatus 60 comprises a shield, such as a thermal shield.

(35) Once the downhole apparatus 60 has been run in to the target location 52, as shown in FIG. 3, the method comprises the targeted oxidation of the target downhole material 42 at the target location. The heating device of the downhole assembly 60 directly and indirectly heats the target material 42 to be removed at the target location 52. Here, the method comprises initiating the heating device by the ignition of the combustible charge, bringing the fuel of the heating device up to a temperature sufficient for the fuel to oxidize. The temperature is sufficient for the heating device to break down the oxidizing agent to facilitate oxidation of the target material 42. The heating device heats the target material 42 to a sufficient temperature to start oxidation of the target material 42, in the presence of the suitable oxidant. The oxidizing target material 42 is heated to a sufficient temperature to break down the oxidizing agent to facilitate continuing oxidation of further target material 42. The method comprises supplying oxygen to the heating device and the target material 42 to propagate the oxidation.

(36) The method may comprise directing a stream of pure oxygen at a red-hot area of the target material 42, so as to immediately form a film of oxide (e.g. iron oxide). Where the target material 42 is a steel tubing, the melting point of iron oxide (approx. 800-900 degrees C.) is well below the melting point of steel (1,400-1,500 degrees C.). The velocity of the stream of high pressure oxygen blows the oxide film away and another film of oxide is instantly formed and blown away. The intense heat generated at the end of the heating device, when applied to a material will quickly burn through it; and also consume the heating device. In at least some examples, the heating device is a thermic lance. The heating device may operate at a temperature in the order of 4,000 degrees C. The heating device may comprise an appropriate diameter for location within and thermal engagement with the target material 42. For example, the heating device may comprise a diameter from less than one inch, up to several inches. The diameter of the heating device may be selected according to an inner diameter at the target location 52, such as to provide a particular clearance between an outer diameter of the heating device and an inner diameter of the target material 42.

(37) The method comprises oxidizing the downhole material 42 in an exothermic reaction. The oxidation comprises a rapid oxidation. Here the method comprises supplying the oxidizing agent from a surface source via the coiled tubing 62. The exothermic reaction generates sufficient heat to heat additional target material 42 sufficiently to propagate the oxidation process. The method comprises continuing the oxidation process to further remove target material 42 by oxidation. The method comprises continuing oxidation until a sufficient amount of target material 42 has been oxidized and removed (see FIG. 4). Here, the sufficient amount of target material 42 to be oxidized and removed is predetermined to provide an appropriate axial length of removed production tubing 42.

(38) The downhole apparatus 60 is configured to oxidize and remove target material from the target downhole location 52. Here, the apparatus 60 comprises a predetermined amount of fuel. The heating device is configured to be consumed at a rate slightly less than the target material 42. Here, an expected axial rate of oxidation of the target material 42 has been predetermined (e.g. by calculation or simulation) such that the heating device is configured to diminish by oxidation at a corresponding rate, incorporating a safety margin to ensure that all target material 42 is removed along the desired axial length of the target material 42 to be removed. Furthermore, the apparatus is configured to control the rate of consumption of the heating device by controlling the supply of the oxidizing agent via the coiled tubing 62. As shown in FIG. 3, the downhole assembly 60 remains substantially stationary during the oxidation process. Here, the heating device is consumed during oxidation axially along its length, typically upwardly from a downhole or lower end portion thereof. In other examples, the heating device fuel is consumed downwardly from an upper end portion. The axial length of the thermic length consumed or to be consumed during oxidation corresponds directly to the axial length of the target material to be removed. The axial length of the target material to be removed is selected from one metre, up to hundreds of metres, or even kilometres, depending upon the operation.

(39) In other examples, the method comprises repositioning the downhole assembly 60 during the oxidation process. For example, the method comprises repositioning the heating device to accommodate a rate of material removal. Particularly where there is a difference between the axial rate of removal of material from the target material 42 and the axial rate of consumption of the heating device, then the downhole assembly 60 is repositioned during the oxidation process to locate an oxidizing portion of the heating device relative to the target material 42 (e.g. axially adjacent or within the target material 42).

(40) Here, the method comprises the successive oxidation of sequential layers of the downhole material 42, each layer being oxidized prior to its removal to reveal a next, underlying layer of downhole material 42 for oxidation. The oxidized layers are removed by a flow, such as a flow of one or more of: oxygen; oxidized material; fuel; oxidizing agent; carrier fluid; flushing fluid; injection fluid; acid and/or a mixture. In other examples, the oxidized material is removed by an additional process or step, such as by a mechanical removal process (e.g. a milling, drilling or other mechanical material removal process, or perforating or the like); and/or a chemical or fluid process (e.g. flushing with an acid or the like). The oxidation improves, quickens or simplifies the additional process or step, such as by enabling quicker and easier mechanical and/or chemical removal of the target material (e.g. compared to mechanical and/or chemical removal of non-oxidized target material).

(41) The method comprises predetermining an amount of fuel required. Here, the method comprises providing an excess of fuel, the excess being greater than an amount of fuel required to remove a target amount of target material 42. The method comprises terminating the oxidation process prior to exhaustion of the fuel. For example, the method comprises extinguishing the oxidation process by the cessation of the availability of the oxidant, such as by reducing or stopping supply via the coiled tubing 62.

(42) The method comprises remotely controlling the process from surface by controlling the supply of oxidizing agent via the coiled tubing 62. Furthermore, the method comprises controlling the initiation, using a remote signal to ignite the thermite charge. In some examples, the remote signal is conveyed through the bore (e.g. along the coiled tubing, fluid therewithin, or the tubing 42 or casing 28), such as using a pulse signal. Controlling the process comprises actively adapting the process, selecting when to initiate the process and when and how to vary a process parameter mid-process. The method is selectively controlled, obtaining feedback, and adapting the process according to the feedback, such as to vary one or more of: a supply of oxygen, a supply of oxidizing agent; a supply of fuel; a temperature; a fluid flow; a position of the downhole assembly.

(43) Here, the method comprises a rigless operation. The method comprises an intervention or downhole operation from a rigless mobile surface unit. For subsea bores, as shown here, the method comprises operation from a floating vessel.

(44) Referring now to FIG. 4, there is shown the portion of the well bore 20 following the downhole material removal with the downhole apparatus 60 of FIG. 6. As shown here, the method comprised removing material 42 to create an axial discontinuity, by removing material circumferentially so as to provide a split in the downhole well element represented here by the production tubing 42. The axial discontinuity eliminates a portion of the first annulus 46 that was previously between the production tubing 42 and the lined borewall 28. It will be appreciated that the coiled tubing 62 connected to the downhole assembly 60 has been pulled from the bore 20, allowing further subsequent operations, such as a perforation shown in FIG. 5. As will be appreciated, the method here comprises a plugging method, for abandonment, the method comprising the tubing 42 removal to allow placement of a plug 70 at the location 52 of the removed tubing 42, as shown in FIG. 6.

(45) As shown in FIG. 4, the length of removed tubing 42 corresponds to an axial length of the heating device. Here, the method comprises removing only a portion of the downhole well element 42. In other examples, a shorter portion of the tubing 42 may be removed, merely to provide an axial discontinuity, allowing the portion of tubing 42 above the discontinuity to be pulled from the bore 42.

(46) As will be appreciated from FIGS. 5, 6, and 7, the method here comprises processes subsequent to the material 42 removal with the heating device. The subsequent operations of preparing the target location 52 by perforating has used one or more perforating guns or assemblies run-in from surface after the heating device has been removed. As shown in FIG. 6, here the method comprises providing a cement plug 70 at the target location 52 to provide an absolute axial barrier, with the removed material 42 having removed a possible leakpath, along or within the production or the first annulus 46, that may otherwise have been present prior to the material removal. It will be appreciated that in other example methods, as an alternative to perforating the casing, a rock to rock window can be created for the cement plug to be placed within, the rock to rock window being created by the apparatus 60, such as where the apparatus 60 has a heating member that can be expanded once at the target location.

(47) As shown in FIGS. 6 and 7, the method comprises providing a permanent well barrier extending across the full cross-sectional area of the bore 20, including any annuli, sealing both vertically and horizontally. FIG. 7 shows the removal or recovery of casing and tubing (and any conductor) between the platform and the seabed (or below the seabed).

(48) It will also be appreciated that a subsequent step of providing an environmental plug at the mouth of the bore 20 (as exposed in FIG. 7) may be provided, such as to prevent passage into or out of the bore 20 at the seabed.

(49) Here, removal comprises local removal, locally removing material from the tubing 42 that remains downhole in another downhole location (e.g. below the target location 52). In other examples, at least a portion of the locally removed material is removed or extracted from the bore, such as by retrieval uphole.

(50) In other examples (not shown), the method comprises the removal of target material at a plurality of target locations. For example, the method comprises the removal of target material from a first downhole target location, then repositioning the downhole assembly at a second downhole target location (e.g. by partially pulling the downhole assembly) and then removing target material at the second downhole target location, all in a single run. Such a method comprises repositioning the downhole assembly without requiring a re-initiation of the heating device. In at least some examples, oxidation may continue uninterrupted whilst the downhole assembly is repositioned. In other methods, the oxidation is interrupted whilst the downhole assembly is repositioned, in at least some examples requiring a re-ignition of the heating device. Such methods comprise an interruption in or reduction of the supply of fuel and/or oxidizing agent during the repositioning. Additionally, or alternatively, the downhole assembly is repositioned at a sufficient rate so as not to substantially remove material between the first and second downhole target locations. It will be appreciated that the first downhole target location could be below or above the second target location, with the downhole assembly either being run-in further or partially pulled as appropriate.

(51) In other examples (not shown), the method comprises protecting at least one part or region with a shield. For example, the method comprises providing a thermal shield downhole. The thermal shield comprises a high temperature resistant element, such as comprising, by way of example, ceramic and/or glass. The method comprises providing a plurality of shields. The method comprises positioning the shield/s downhole prior to initiation. The shield/s may protect one or more zone/s, area/s or portion/s downhole so as to prevent heating and/or oxidation and/or material removal therefrom. In at least one example, shield/s protect a zone, area or portion uphole of the target material, such as a non-oxidizing portion of the downhole assembly and uphole equipment and/or materials associated with or attached thereto (e.g. coiled tubing, uphole casing, or the like associated with or attached to the downhole assembly). Additionally, or alternatively, the shield/s protect a zone, area or portion downhole of the target material, such as a seal, plug or packer located below the downhole assembly, typically below the target material. In at least some examples, the shield/s protect a non-window portion, that is a portion of the downhole part or component not intended to be removed, such as a portion of casing, liner or tubular surrounding a window portion to be removed. In at least some examples, the method comprises a preparation for a sidetracking or secondary bore-drilling process.

(52) Referring now to FIG. 8, there is shown a schematic view of a helical thermic lance 80 for a heating device.

(53) The helical thermic lance 80 comprises a circumferential extent, such as when viewed axially (e.g. when viewed along the longitudinal axis 82). The helical thermic lance 80 comprises a heating member that is configured to direct heat sequentially or temporally in an angular direction, such as radially or laterally relative to the longitudinal axis. Here, the heating member is configured to progressively direct heat around the longitudinal axis 82, such as at least 360 degrees around the longitudinal axis. Here, the heating member is configured to direct heat progressively in multiple revolutions around the longitudinal axis 82 (5 revolutions shown here). Accordingly, in use, the thermic lance 80 heats around the entire longitudinal axis 82, such as progressively or sequentially around an entire circumference of the longitudinal axis 82.

(54) Here, the helical portion of the helical thermic lance 80 comprises a regular cylindrical helix, shown here as a right hand helix. Here, the helix comprises five revolutions; and a helix angle, the helix angle being defined as the angle between the helix and an axial line on the helix's right, circular cylinder or cone. The helix comprises a helix pitch 84, the pitch being the height of one complete revolution, measured parallel to the longitudinal axis 82 of the helix.

(55) The helical thermic lance 80 comprises a member cross-section, shown here as a circular member cross-section. As will be appreciated, an outline of the cross-section of the thermic lance is defined by the container or sheath of the thermic lance (not shown). The cross-section is continuous along the helical length of the thermic lance. The cross-section comprises a non-solid or a hollow profile, such as with several openings 69 therein, the openings 69 extending along the entire length of the thermic lance 80. The openings allow the transmission of oxygen to the end 89b or tip of the thermic lance 80. For example, where the thermic lance 80 has a sheath 93 with multiple fuel rods 91 therewithin, the openings 69 correspond to the gaps between the fuel rods (e.g. where the fuel rods have non-tessellating cross-sections, such as circular). Here, additional oxygen can be supplied to the burning end 89b of the thermic lance 80 and also the target material by pumping oxygen down the annulus in which the thermic lance 80 is positioned. For example, where the thermic lance 80 is mounted on a coiled tubing string, oxygen may be pumped down the coiled tubing and optionally also down the inner central annulus in which the coiled tubing is located. It will be appreciated that the thermic lance 80 progressively shortens in use, with a burning tip progressively travelling along the helical path defined by the helical lance 80. Here, the thermic lance 80 comprises a circular cross-section, with wire fuel rods housed within a tube-shaped sheath, the circular cross section comprising a cross-sectional diameter 86.

(56) The helical thermic lance 80 comprises a longitudinal length 88, shown here as a total separation between opposite ends 89a, 89b of the helical thermic lance 80 in a longitudinal direction. It will be appreciated that although schematically shown here as open at both ends 89a, 89b, the thermic lance 80 is generally closed or connected at at least one end, such as the upper end 89a, typically for connection to an oxygen supply through that closed connection. The helical thermic lance 80 comprises a total heating member length along the helical path, the heating member length being considerably longer than the longitudinal length of the heating member. The helical heating member length can be considered as unraveled or unwound, such heating member length being considerably longer than the longitudinal separation 88 between the opposite ends 89a, 89b of the heating member in its helical form. Accordingly, the helical thermic lance 80 can have a longer burn time for a same cross-sectional profile relative to a straight axial thermic lance (not shown) of similar longitudinal length.

(57) The helical heating member comprises a longitudinal separation 90 between adjacent revolutions or turns of the helix. Here, the helical thermic lance 80 comprises no more than a maximum longitudinal separation 90 between adjacent revolutions or turns of the helix, such that there is no longitudinal separation between corresponding revolutions or turns of target material that is not sufficiently heated and/or oxidised. Accordingly the helical thermic lance 80 here is configured to remove a tube or cylindrical shaped volume of target material.

(58) The longitudinal separation 90 between adjacent revolutions or turns of the helix is determined by or at least related to the pitch 84 and the cross-sectional property of the helical thermic lance 80. Here, the pitch 84 of the helix is the sum of the longitudinal separation 90 between adjacent revolutions or turns and an outer diameter 86 of the cross-section of the heating member.

(59) The helix comprises a helix diameter 92, with an inner helix diameter being the helix diameter 92 less the outer diameter 86 of the cross-section of the heating member' and an outer helix diameter being the helix diameter 92 plus the outer diameter 86 of the cross-section of the heating member. The inner and outer diameters are defined when viewed axially, such as by circles in a plane perpendicular to the longitudinal axis 82 along which the helix extends. The helix outer diameter is selected according to an intended use, such as a minimum inner diameter of a target material into which the helical thermic lance is intended for insertion. The helix inner diameter is selected according to an intended use, such as an intended central passageway defined by an inner cylindrical volume within the inner diameter of the helix. The inner and outer diameters of the helix are determined by or related to the heating member cross-sectional property/ies, such as the heating member cross-sectional diameter 86. The outer helix diameter is greater than the helix inner diameter by an amount defined by the heating member cross-sectional diameter 86 (being twice the heating member cross-sectional diameter 86).

(60) Here, each of the helix pitch 86; helix diameter 92; heating member longitudinal length 88; helix angle and heating member cross-section property 86 is selected according to the portion of target material to be heated. Here, the helix outer diameter is selected to be less than a minimum inner diameter of the target material to be heated. For example, where the helical thermic lance 80 is for heating a portion of a passage, such as a portion of a downhole wellbore, the helix outer diameter is selected to be less than a minimum diameter of a restriction, such as an inner diameter of a flow control device or flange, through which the helical thermic lance 80 must pass to reach the target material.

(61) Although not shown here, in other examples the helical thermic lance comprises an expandable heating member. For example, the heating member comprises a helical member that is radially and/or longitudinally expandable. In at least some examples, the heating member is transferable to the target location in a collapsed configuration for expansion at the target location. Particularly where the heating member is a helical heating member for target material heating and/or removal within or of the enclosed volume, the heating member is transported to the target location in the collapsed configuration to allow or simplify the passage of the heating member thereto, such as through one or more restrictions. For example, where the target material to be heated and/or removed is or is in a passage, such as in a well bore or being a well apparatus, the heating device is transportable to the target location in the passage with the heating member radially collapsed so as to ease transport through a narrow diameter passage.

(62) In at least some examples, the heating member is radially and/or longitudinally expandable by an active or forced expansion by an expander. For example, an apparatus comprising the expandable heating member also comprises an expansion cone for axial passage through the helical heating member so as to increase the inner diameter of the helix, thereby increasing the outer diameter of the helix. The heating member is selectively expandable, such as upon selected actuation of the expander.

(63) Additionally or alternatively, the heating member is radially and/or longitudinally expandable according to a spring property of the heating member. For example, the helical heating member is transported in a collapsed configuration, with the heating member radially and/or longitudinally constrained. The radial and/or longitudinal constraint is achieved by an apparatus member, such as an apparatus sheath and/or apparatus piston. Alternatively, the constraint is external to the apparatus, such as defined by the enclosed volume into or through which the heating member is to pass. For example, the helical heating member for downhole well material heating and/or removal is collapsed at surface to radially fit within a casing or tubular, with the casing or tubular constraining the outer diameter of the helix. The helical member may then be transported downhole to the target location, the target location including a larger diameter, or acquiring a larger diameter during material removal, so as to allow or trigger expansion of the heating member to a larger outer helix diameter. The heating member is expandable before and/or during and/or after a heating. For example, the heating member is expandable after a first heating, being expanded to a greater diameter for a second heating.

(64) In at least some examples, the heating member is longitudinally and/or radially expandable by an application of tension or compression to the heating member. For example, the heating member is selectively subjected to a tensile longitudinal force (e.g. by pulling on one or both ends) so as to longitudinally stretch the heating member, optionally thereby radially collapsing the heating member. Particularly where the heating member comprises the helix, the property/ies of the helix is adjustable, such as selectively adjustable. For example, the helix pitch is adjustable with the application of longitudinal tension to the heating member.

(65) Additionally, or alternatively, the heating member comprises a collapsible heating member. For example, the heating member is radially collapsible to a smaller diameter, such as for passage or subsequent passage through a restriction prior to a heating. The heating member is collapsible by the passage of a member, such as a sheath, along the outer diameter of the heating member.

(66) In use, the helical thermic lance 80 directs a jet of heat, indicated by an arrow 99 in FIG. 8. The helical form of the thermic lance 80 causes the jet 99 to be directed tangentially, such as when viewed axially along the central longitudinal axis 82 of the helix. It will be appreciated that as the helix is consumed during use, that the jet 99 is progressively directed outwards around 360 degrees for each revolution of the helix, as the burning end 89b of the helical thermic lance 80 tracks along the helical path of the lance 80. Accordingly, in use, the jet 99 is directed at an entire circumferential portion of a target material. In at least some examples, the jet 99 includes heat, oxidized and/or molten and/or gaseous material from the thermic lance 80, such as a plasma. The jet 99 can also optionally include oxygen, particularly where oxidation of the target material is desired.

(67) Referring now to FIG. 9, there is shown a portion of an apparatus 160 for heating, in use, shown here within a tubular 142 within a cased bore wall 128. As will be appreciated, the apparatus 160 shown here is a well apparatus 160 for removing material at a well, such as downhole; and/or for removing material at surface, such as for removing material from a surface apparatus 160 or installation (e.g. caisson or other tube-shaped equipment). As with preceding apparatus 60, the apparatus 160 shown here comprises a heat source; and a fuel supply and an oxidant supply. The apparatus 160 comprises a heating device for removing at least a portion of the target material. Here, the target material is an axial portion of a tubular 142 within a cased bore wall 128, the tubular 142 defining a passage. Here, the heating device comprises the thermic lance 80 of FIG. 8. The thermic lance 80 comprises a similar sheath and fuel to the apparatus 60 of FIG. 3.

(68) The thermic lance 80 comprises a longitudinal extent that extends in an axial direction along the enclosed volume of the tubular 142 when the apparatus 160 is in use. The heating device comprises a longitudinally extending heating member. The heating device is configured to heat along the axial extent. The apparatus 160 is configured to heat progressively along the axial extent, such as by progressive heating longitudinally along the thermic lance 80.

(69) The thermic lance 80 is configured to oxidise and heat transversely, such as transversely to a longitudinal axis of the apparatus 160 and the passage. The apparatus 160 is configured to oxidise and heat laterally. Here, the apparatus 160 is configured to direct heat transversely, substantially tangentially, such as when viewed axially (e.g. with a tangential component or vector).

(70) It will be appreciated that the apparatus 160 can cause the target material to be removed by melting and/or oxidation, in use. For example, heat emanating directly or indirectly from the apparatus 160 may heat the target material beyond its melting point. The target material melts accordingly and can fall away.

(71) In at least some examples, the apparatus 160 comprises an inlet (not shown) for receiving oxidant to be supplied, such as via a conduit or passage (e.g. from a remote source). The apparatus 160 comprises one or more valves for controlling the supply of oxidant to the thermic lance 80. Here, the apparatus 160 comprises a controller (not shown) for controlling the supply of oxidant to the heating member. The apparatus 160 comprises an ignition, which is a remotely controllable electrical ignition (not shown).

(72) It will be appreciated that although shown here for removing a circumferential window from a 5½″ (17 lbs/ft) production tubing inside a 9⅝″ (47 lbs/ft) casing cemented in formation, other dimensions and types of target material can be removed with this or other helical thermic lance 80, such as with helix properties configured for the particular target material (e.g. with a smaller or larger helix diameter as appropriate).

(73) Referring now to FIG. 10, there is shown an apparatus 260 for heating, in use, generally similar to that shown in FIG. 9. Accordingly, the apparatus 260 comprises a heating device with the helical thermic lance 80 of FIG. 8. Again, the apparatus 260 is shown here within a tubular within a cased bore wall. As shown here, the heating device comprises a central passage 294, located radially inwards of the helical thermic lance 80, the central passage 294 being located in the helix inner diameter. Here, the central passage 294 includes the central longitudinal axis 82 of the helical thermic lance. The central passage 294 is parallel to and collinear with the central longitudinal axis 82 of the helical thermic lance 80. Here, the central passage 294 comprises a central member 295, here being an enclosed hollow central member 295 defining a bore or throughbore therewithin. The central passage 294 is configured for the transmission of signals and/or materials therethrough, such as oxygen, to one or more heating devices. The signal/s comprises one or more of: an actuation signal/s; a control signal/s; a measurement signal/s. In at least some examples, the signals comprises the incoming actuation and the deactuation signals for the thermic lance 80 and a further thermic lance (not shown); and an outgoing measurement signal indicative of the heating process, such as to indicate a temperature and/or a material removal status. The central passage 294 comprises one or more of: an electrical line/s; a fluid line/s; a fibreoptic line; an acoustic transmission line; an electromagnetic transmission line. The central passage 294 is configured to protect from heat. For example, here, where the apparatus 260 is configured to direct heat laterally outwards, the central passage 294 located centrally, at an inner diameter, is configured to inherently receive less heat, relative to radially outside the helical thermic lance 80. Here, the central passage 294 is additionally thermally shielded by the central member 295 comprising a cylindrical thermal shield. The apparatus comprises a controller, such as for controlling ignition and/or extinction of the helical thermic lance 80. In at least some examples, the controller is located remotely from the thermic lance 80, such as at or near an oxygen source therefor.

(74) Referring now to FIGS. 11a, 11b and 11c, there are shown examples of arrangements of a plurality of thermic lances 80. As can be appreciated by comparing the figures, the helix angle, pitch and number of revolutions of each helical thermic lance 80 is adapted to account for the number of helical thermic lances 80 in the arrangement.

(75) At least some example apparatus comprises a plurality of helical thermic lances 80, such as shown in FIG. 11a, 11b or 11c. The heating device of the apparatus comprises the plurality of helical thermic lances 80 as shown in the respective arrangements. For example, the heating device comprises two, three or four helical thermic lances 80, respectively. Each of the helical thermic lances 80 is arranged at a similar longitudinal position.

(76) The plurality of helical thermic lances 80 is configured to heat and/or oxidise a same portion of target material. The same portion of target material is located at the same target location. Each of the helical thermic lances 80 is configured to remove a helical-form portion of target material, each helical form portion rotationally spaced. Each of the helical thermic lances 80 is configured to remove a helical-form portion of target material such as to remove a tube-shaped or cylindrical volume of target material when the plurality of helical-form portions is combined. The plurality of helical thermic lances 80 is configured for substantially simultaneous actuation. Actuation comprises ignition. The plurality of helical thermic lances 80 is configured for simultaneous heating. The plurality of helical thermic lances 80 is configured to concurrently heat. The plurality of helical thermic lances 80 is singularly controllable, such as via a single controller for controlling the plurality of helical thermic lances 80. The plurality of helical thermic lances 80 is configured for simultaneous oxygen supply, such as from a single oxygen source. The plurality of helical thermic lances 80 is configured for substantially simultaneous deactuation. Deactuation comprises extinction, such as by cessation of the oxygen supply.

(77) It will be appreciated that in at least some examples, the plurality of thermic lances may be noncontemporaneously activated. For example, at least some of the plurality of thermic lances may be sequentially activated, such as with a first thermic lance 80a heating a first target material (e.g. the production tubing 42 of FIG. 2) and a second thermic lance 80a heating a second target material (e.g. the casing 28 of FIG. 2). In at least some examples, the first and second target materials are located at a similar axial position (e.g. similar bore depth); whilst in other examples, the first and second target materials are axially spaced (e.g. the heating device is moved from a first target location to a second target location between activation of the first and second thermic lances 80a).

(78) Two or more of the helical thermic lances 80 comprises one or more similar properties. For example two or more of the helical thermic lances 80 comprises similar helical thermic lances 80, comprising similar: helix pitch; heating member longitudinal length; helix angle and/or helical thermic lance 80 cross-section property/ies. In at least some examples, the plurality of helical thermic lances 80 have similar properties, arranged longitudinally coincident, with the helical thermic lances 80 rotationally offset, such that the two or more helical thermic lances 80 are arranged circumferentially around the plane perpendicular to the longitudinal axis. The helical thermic lances 80 are evenly rotationally offset. For example, where there are two longitudinally coincident similar helical thermic lances 80, such as shown in FIG. 11a, the helical thermic lances 80 are arranged rotationally offset by 180 degrees. As shown in FIGS. 11a, 11b and 11c, the burning ends of each helical thermic lance are arranged to track along their respective helical paths at a similar rate, with the burning ends being axially aligned in use as depicted in FIGS. 11a, 11b and 11c (e.g. with a burning end of a first lance 80a directly above a burning end of a second lance 80a). It will be appreciated that in other examples, the burning ends in use may be axially misaligned, such as diametrically opposed. Each burning end of a helical thermic lance 80 provides a jet 99 directed tangentially, noting also that the jet will be directed angularly according to a pitch angle of the helix. The longitudinal separation between adjacent revolutions or turns of a single helix of each helical thermic lance 80 exceeds the maximum longitudinal separation, such that a corresponding helical portion of the target material is insufficiently heated by a single thermic lance 80, which would leave the corresponding portion of the target material unheated and unremoved—in the absence of the other of the thermic lances 80a. Accordingly, each thermic lance 80 is configured to heat only a helical portion of target material. However, the corresponding portions of each of the thermic lances 80 overlap such that the combined heated target material of both of the thermic lances 80 is a cylindrical sufficiently heated volume.

(79) In other examples (not shown), it will be appreciated that the helical thermic lances comprise dissimilar properties. For example, particularly where the plurality of helical thermic lances are non-contemporaneously activated, then the helical thermic lances may be non-identical. Especially where the thermic lances are intended to heat different target materials, then the thermic lances can have different properties. For example, where a first thermic lance is for heating a first target material, such as an inner target material (e.g. the production tubing 42 of FIG. 2); and a second thermic lance is for heating a second target material, such as an outer target material (e.g. the casing 28 of FIG. 2), then the second thermic lance may be configured to provide a different jet of heat from the first thermic lance. In at least some examples, the second thermic lance has a greater outer diameter 86 (not shown), allowing the second thermic lance to jet more heat to bridge a greater gap to the outer target material. It will be appreciated that the first and second thermic lances can have a similar helix diameter 92 such as to allow both thermic lances to be positioned within the inner target material.

(80) Referring now to FIG. 12, there is shown an apparatus 260 comprising a plurality of heating devices, each heating device comprising a thermic lance 80. Here, the plurality of heating devices are spaced longitudinally, along a longitudinal axis of a downhole tool string. Each of the plurality of heating devices is similar, each comprising a single helical thermic lance 80. The plurality of heating devices is selectively controllable. Each of the heating devices is independently controllable. For example, a supply of oxidant to a first heating device is controlled separately from a supply of oxidant to a second heating device. The plurality of heating devices is selectively independently actuatable. For example the first heating device is actuated prior to the second heating device. Here a controller 296 more proximal the heating device is included. It will be appreciated that the apparatus 260 can optionally include other devices, such as selected from one or more of: perforation guns, logging tools, cementing tools, plugs, packers.

(81) FIG. 13 shows an example of a surface equipment package 400 for a downhole apparatus. Here the package 400 comprises a coiled tubing package, with a liquid oxygen converter and pump for pumping oxygen through the coiled tubing 402 to the downhole apparatus 460. It will be appreciated that the coiled tubing 402 may be connected to a central member of a heating device of the downhole apparatus, such as to allow selective passage of oxygen internally to a helical thermic lance associated with the heating device. In addition, oxygen may be supplied externally to a target location, such as passing from the coiled tubing into an annulus in which the downhole apparatus 460 is located.

(82) Referring now to FIG. 14, there is shown an example well 500, with selected target locations 505a, 505b, 505c, 506a, 506b, 506c. Multiple target locations 505a, 505b, 505c are located downhole, such as for removing tubing and/or casing in preparation for plugging and abandonment. It will be appreciated that multiple target locations 505a, 505b, 505c may be subjected to simultaneous heating, such as by multiple heating devices located at each target location 505a, 505b, 505c. Alternatively, the target locations 505a, 505b, 505c may be subjected to sequential heating, such as by pulling a heating device with multiple thermic lances from a lowermost target location 505c, to an upper target location 505b—after first heating the lowermost target location 505c. Multiple target locations 506a, 506b, 606c are located at surface, such as for removing material from a surface apparatus or installation (e.g. caisson or other tube-shaped apparatus).

(83) Referring now to FIG. 15, there is shown a flow chart generally similar to that shown in FIG. 1. Here, the method 505 comprises a first step 510 of heating; followed by a subsequent step 512 of melting and/or oxidizing target material and a further step 514 of removing the oxidized target material. It will be appreciated that in at least some examples the steps may be linked or even concurrent. For example, where target material is melted the target material may be concurrently removed by the melted target material dropping away as it melts.

(84) It will be appreciated that any of the aforementioned device or apparatus may have other functions in addition to the mentioned functions, and that these functions may be performed by the same device or apparatus.

(85) The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims.

(86) The applicant indicates that aspects of the present disclosure may consist of any such individual feature or combination of features. It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the disclosure. For example, it will to be appreciated that although shown here as a bore with a vertical orientation, other bores may have other orientations. For example, other example bores may have at least non-vertical portions, such as deviated or horizontal sections or bores. It will be appreciated that as used herein, ‘uphole’ may refer to a direction towards surface or an entry point to the bore, without necessarily being purely vertically upwards. Likewise, ‘downhole’ may not necessarily be purely directly downwards, such as merely away from a bore entry point in a deviated or horizontal bore.

(87) In addition, features disclosed for a particular example use or application, may be applicable for other uses or applications. For example, features disclosed in relation to downhole examples, such as for downhole target material, may be applicable to other target material, not necessarily downhole.

(88) It will be appreciated that example or embodiments can be realized in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage, for example a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory, for example RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium, for example a CD, DVD, magnetic disk or magnetic tape or the like. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs comprising instructions that, when executed, implement embodiments of the present disclosure.

(89) Accordingly, examples or embodiments provide a program comprising code for implementing apparatus or a method as claimed in any one of the claims of this specification and a machine-readable storage storing such a program. Still further, such programs may be conveyed electronically via any medium, for example a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

(90) Although various denotations have been used throughout the description, tubing, liner, casing etc. should be understood as pipe or tubular of steel or other metals or materials such as used in well operations. In at least some examples, by the use of the described invention, all operations can be performed from a light well intervention vessel, offshore platform installation, land-based well site or similar, and the need for a rig is eliminated. Prior to the ignition of the fuel-oxidizing mixture, the well may be pressure tested to check if the seal is tight. This may be performed by using pressure sensors or other methods of pressure testing, such as conventionally.

(91) It will also be appreciated that although shown here with particular reference to wells, other applications and uses are also disclosed. For example, a helical thermal lance for non-well use is also disclosed, particularly for use in enclosed volumes such as passages. Especially where an exterior of the passage is poorly accessible, then the helical thermic lance can have special utility. Accordingly, pipes, such as in nuclear, chemical and other processing; or buildings or transport networks; can be heated and/or removed by the helical thermic lance.

(92) Likewise, where a helical thermic lance has been shown here, in other examples, the heating device may comprise additional or alternative heating elements or members. For example, in at least some embodiments, the heating device may comprise a helical heating element in the form of a combustible material helically arranged. The combustible material may be a highly exothermic combustible, such as a powder charge, with the helical arrangement being provided by a container, matrix (e.g. cylindrical or helical matrix) or the like for supporting the combustible material.