Tool with propellant sections

Abstract

A tool for manipulating a tubular. The tool comprising a plurality of tool sections arranged in a stack, each tool section comprising a propellant source having an upper surface and lower surface, the upper and lower surfaces being separated by an outer surface extending around the perimeter of the propellant source, a first flame retardant material being associated with the propellant source upper surface and a second flame retardant material being associated with the propellant source lower surface. The tool further comprises at least one modifying agent provided in or adjacent the tool sections or generated by the tool sections; and an ignition mechanism for igniting the propellant source outer surface of each tool section, such that upon ignition, each propellant source is adapted to deflagrate, creating a stream of combustion products, the stream of combustion products extending around, and flowing away from, the outer surface of said propellant source.

Claims

1. A tool for manipulating a tubular, the tool comprising: a plurality of tool sections, each tool section comprising a propellant source having an upper surface and lower surface, the upper and lower surfaces being spaced apart and separated by an outwards facing outer surface extending around an outer perimeter of the propellant source between the upper and lower surfaces, a first flame retardant material being associated with the propellant source upper surface and a second flame retardant material being associated with the propellant source lower surface; at least one modifying agent provided in or adjacent the tool sections or generated by the tool sections, the modifying agent being for at least one of transferring heat to, eroding, ablating, abrading, displacing, and removing at least a portion of the tubular to be manipulated; and an ignition mechanism for igniting the outwards facing outer surface of the propellant source of each tool section, such that upon ignition, propellant at each propellant source deflagrates, creating a stream of combustion products, the stream of combustion products extending around, and flowing away from, the outwards facing outer surface of said propellant source, wherein the tool sections are arranged in a stack, and wherein the ignition mechanism comprises transfer ignitors positioned between the tool sections of the plurality of tool sections, and an initiator which runs from a control location to the outwards facing outer surface of the propellant source of a first tool section of the plurality of tool sections whereby, following ignition of the outwards facing outer surface of the propellant source of the first tool section, at least one of the transfer ignitors ignites the outwards facing outer surface of a second tool section of the plurality of tool sections.

2. A tool according to claim 1, wherein each tool section comprises a housing and the propellant source is wholly contained within the housing.

3. A tool according to claim 1, wherein each tool section comprises a housing and the propellant for the propellant source is fed into the housing.

4. A tool according to claim 3, wherein the propellant for the propellant source is fed into the housing either continuously or intermittently.

5. A tool according to claim 1, wherein each propellant source is a disk.

6. A tool according to claim 5, wherein the propellant source is a disk, the upper and lower surfaces are aligned, in use, perpendicular to a wellbore axis.

7. A tool according to claim 1, wherein each propellant source is frusto conical.

8. A tool according to claim 1, wherein the stream of combustion products from one tool section overlaps the stream of combustion products from an adjacent section.

9. A tool according to claim 1, wherein each tool section includes a housing.

10. A tool according to claim 9, wherein each housing includes an upper section and a lower section, the housing upper section being adjacent a propellant source upper surface and the housing lower section being adjacent a propellant source lower surface.

11. A tool according to claim 10, wherein each of the upper section of the housing and the lower section of the housing comprises a plate, and the plates are parallel.

12. A tool according to claim 1, wherein each tool section defines an outlet, each tool section being arranged such that the stream of combustion products flows through the outlet, wherein the outlet is, in use, arranged to direct the stream of combustion products to manipulate an area of tubular.

13. A tool according to claim 12, wherein the area of tubular, in use, extends around the internal circumference of the tubular.

14. A tool according to claim 12, wherein the height of the area of tubular is greater than the spacing between the propellant source upper and lower surfaces.

15. A tool according to claim 12, wherein the height of the area of tubular at the surface of the tubular to be manipulated is greater than the spacing between the propellant source upper and lower surfaces.

16. A tool according to claim 1, wherein at least one of the propellant sources comprises a plurality of propellants.

17. A tool according to claim 1, wherein the propellants are arranged concentrically.

18. A tool according to claim 1, wherein the propellants are arranged in layers.

19. The tool of claim 1, wherein the propellant source comprises a body of propellant, the body of propellant defining a combustion surface including the outer surface of the propellant source, the body of propellant comprising a plurality of propellant sections, the propellants sections being relatively movable, in use, to maintain the position of the combustion surface constant relative to an external reference point as the body of propellant deflagrates.

20. The tool of claim 19, wherein the propellants sections being relatively movable, in use, maintain constant external diameter of the propellant source as the body of propellant deflagrates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described with reference to the accompanying drawings in which:

(2) FIG. 1 is a section of a tool for stripping a length of wellbore casing and associated cement back to bare rock to allow a wellbore plug to be fitted to seal the wellbore in accordance with a first embodiment of the present invention;

(3) FIGS. 2, 3, 4 and 5 are section views showing the operation of the tool FIG. 1;

(4) FIG. 6 is a section of a tool for stripping a length of wellbore casing and associated cement back to bare rock to allow a wellbore plug to be fitted to seal the wellbore in accordance with a second embodiment of the present invention;

(5) FIG. 7 is a section of a tool for stripping a length of wellbore casing and associated cement back to bare rock to allow a wellbore plug to be fitted to seal the wellbore in accordance with a third embodiment of the present invention;

(6) FIG. 8 is a plan view of the propellant source of the embodiment of FIG. 7; and

(7) FIGS. 9, 10 and 11 are alternative structures propellant source according to further embodiments of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(8) Reference is first made to FIG. 1 a section of a tool, generally indicated by reference numeral 10, for stripping a length (indicated by the letter “L”) of wellbore casing 12 and associated cement 14 back to bare rock 16 to allow a wellbore plug (not shown) to be fitted to seal the wellbore 18, in accordance with a first embodiment of the present invention.

(9) The tool 10 comprises a plurality of tool sections 20a-e. As will be shown each tool section 20 strips a section of the length L of casing 12 and cement 14, the tool sections 20 combining to strip the entire length L of casing 12 and cement 14.

(10) The tool sections 20a-e have similar constructions and the first tool section 20a will now be described.

(11) The first tool section 20a comprises a propellant source 22a in the form of a ring defining an upper surface 26a and a lower surface 24a, the upper and lower surfaces 26a, 24a being parallel and linked by a propellant source defined outer surface 28a extending around the perimeter 30a of the propellant source 22a and a propellant source inner surface 50a bounding a propellant source throughbore 52a.

(12) Embedded within the propellant source 22a is a modifying material (not shown) in the form of metal particles. The purpose of these particles will be discussed in due course.

(13) The first tool section 20a further comprises a first sheet 32a of a rubber flame retardant material adhered to the propellant source upper surface 26a and a second sheet 34a of a rubber flame retardant material adhered to the propellant source lower surface 24a.

(14) The first tool section 20a further comprises a housing 36a. The housing 36a comprise an upper steel disk 38a and a lower steel disk 40a, the steel disks 38a, 40a being parallel. Each of the steel disks 38a, 40a also define a throughbore 48a, 49a.

(15) Attached to the upper and lower steel disks 38a, 40a are upper and lower circumferential lips 42a, 44a respectively. The circumferential lips 42a, 44a define a 360 degree divergent nozzle 46a.

(16) When assembled each of the tool sections 20 define a throughbore 54, the tool section throughbore 54 being the combined throughbores 48, 49, 52 of the steel disks 38, 40 and the propellant source 22.

(17) The tool 10 further comprises a mandrel 56 which passes through the tool section throughbores 54, forming a threaded connection with the housing of each of the tool sections.

(18) The tool 10 additionally comprises an ignition mechanism 58 for igniting the propellant sources 22. The ignition mechanism 58 comprises an electronic initiator 60 which runs from a control location (not shown) to the outer surface 28a of the first tool section propellant source, the electronic initiator 60 terminating in a spark generator 62.

(19) The ignition mechanism 58 further comprises four transfer ignitors 64,66,68,70 the first transfer ignitor 64 being positioned between the first tool section 20a and the second tool section 20b, the second transfer ignitor 66 being positioned between the second tool section 20b and the third tool section 20c, the third transfer ignitor 68 being positioned between the third tool section 20c and the fourth tool section 20d, and the fourth transfer ignitor 70 being positioned between the fourth tool section 20d and the fifth tool section 20e. The transfer ignitors 64, 66, 68, 70 are strips of propellant which provide a continuous connection between the tool sections 20, for transferring the flame/combustion zone from one tool section 20 to the next tool section 20, as will now be described.

(20) Referring to FIG. 2, a section through the tool 10 of FIG. 1, showing the ignition of the first tool section 20a, the ignition signal has been sent from above ground to the tool 10, through the electronic initiator 60. Particularly, the electronic initiator generates a spark which ignites the outer surface 28a of the propellant source 22a of the first tool section 20a.

(21) The first tool section outer surface 28a is “V”-shaped to generate a stream of combustion products 72a, carrying the particles of metal modifying material (not shown), which passes through the divergent nozzle 46a.

(22) The nozzle 46a spreads the stream of combustion products out and impacts the casing surface. The particles of metal within the stream of combustion products 72a are heated by the stream of combustion products. On impact these heated metal particles will transfer heat to the casing 12 allowing the casing 12 to be manipulated and removed, exposing the cement 14 which is then also removed stripping the wellbore 18 back to bare rock 16.

(23) As the propellant source 22a deflagrates, the outer surface 28a recedes back towards the mandrel 56. Once the outer surface reaches the first transfer ignitor 64, the combustion travels along the transfer ignitor 64 to ignite the outer surface 28b of the second tool section 20b.

(24) Reference is now made to FIG. 3, a section through the tool 10 of FIG. 1, showing the initiation of the second tool section 20b. This drawing shows that a portion of the casing 12 and cement 14 have been removed by the first tool section 20a and a stream of combustion products 72b from the second tool section is now attacking the next portion of casing 12 and cement 14. It will be understood that the same mechanism as before transfers the combustion from the second tool section 20b to the third tool section 20c and for subsequent sections thereafter.

(25) Reference is now made to FIG. 4, a section through the tool 10 of FIG. 1, showing the initiation of the third tool section 20c, This drawing shows further removal of the casing 12 and cement 14 by the second tool section 20b has been achieved and a stream of combustion products 72c from the third tool section is now attacking the next portion of casing 12 and cement 14.

(26) Reference is now made to FIG. 5, a section through the tool 10 of FIG. 1 at the completion of removal of casing 12 and cement 14 from the length L of the wellbore 18. As can be seen from this Figure, the wellbore 18 has been stripped back along the length L to bare rock 16. The tool 10 can now be removed or dropped and a plug set in place to allow the wellbore 18 to be abandoned.

(27) Referring to FIG. 6, a tool 110 is shown according to a second embodiment of the present invention. This tool 110 is largely identical to the tool 10 of FIG. 1 other than the propellant sources 122 are frusto conical, creating a slight angle from the horizontal to the direction of flow of the stream of combustion products when the tool 110 is ignited. This allows for the stream of combustion products to push the manipulated material downwards. It is believed this will improve the removal of material from the length of wellbore to be stripped back to bare rock.

(28) Referring to FIG. 7, a tool 210 shown according to a third embodiment of the present invention. This tool 210 is largely identical to the tool 10 of FIG. 1 (although only one tool section 20 is shown) other than the propellant source 222 is made up of three different propellant materials. A plan view of the propellant source 222 can be seen in FIG. 8. This shows that the three different propellant materials are arranged concentrically.

(29) As the propellant 222 burns the diameter of the propellant 222 decreases, resulting in a reduced surface outer surface 228 area and the distance from the perimeter 230 to the casing 212 increases. In this example, the propellant materials have progressively faster deflagration rates creating a stronger stream of combustion products to maintain the stripping capacity of the tool 210. As an alternative, propellant may be fed into the propellant source as indicated by arrows 214 in FIG. 7. Feeding of propellant may be continuous or intermittent.

(30) An alternative structure of a propellant source 322 according to a fourth embodiment of the present invention is shown in FIG. 9. In this embodiment the propellant source 322 is made up of layers of propellant. Upon ignition of the propellant source 322, the deflagration not only occurs on the outer surface 328 of the propellant source 322 but along interfaces 380 between the layers. This increases the surface area of the deflagration.

(31) A further alternative structure of propellant source 422, according to a fifth embodiment of the present invention is shown in FIG. 10 and FIG. 11. The propellant source 422 comprises a series of wedges 482 which, as shown in FIG. 11, move and slide under the action of the spring mechanism 484 to maintain a constant external diameter of the propellant source 422.