Tool for severing or assisting in the severing of a conduit

Abstract

A tool for severing or assisting in the severing of a conduit includes a housing defining a void arranged, in use, to at least partially encircle a conduit and an at least one void access, the void access having a void access inlet in fluid communication with the housing and a void access outlet being in fluid communication with the housing void. At least one propellant source is located within the housing. An ignition mechanism is provided for igniting the propellant source and at least one modifying material. Upon ignition, the propellant source deflagrates, creating at least one stream of combustion products, the stream of combustion products flowing out of the tool through the void access into the void, the void access channelling the stream of combustion products towards the conduit, the stream of combustion products combining with the modifying material to sever or assist in severing the conduit.

Claims

1. A severance tool for severing a target, the severance tool comprising: a housing, the housing containing; at least one propellant source; a plurality of nozzles; and a nozzle holder adapted, in use, to encircle the target to be severed, the nozzle holder being adapted to hold the plurality of nozzles; a trigger mechanism adapted to activate the at least one propellant source; and a centralising means adapted, in use, to create relative movement between the target and the nozzle holder to centralise the target with respect to the nozzle holder, wherein the trigger mechanism is adapted to ignite the at least one propellant source, wherein, upon ignition, the at least one propellant source deflagrates, creating at least one jet of combustion products, which, in use, flows out of the severance tool through the plurality of nozzles to sever the target.

2. The severance tool of claim 1, wherein the target is a conduit.

3. The severance tool of claim 1, wherein the at least one jet of combustion products is biased to a particular direction.

4. The severance tool of claim 1, wherein, where there is a plurality of propellant sources, each propellant source combusts separately.

5. The severance tool of claim 1, wherein the at least one propellant source is separated from an adjacent propellant source by means of a barrier.

6. The severance tool of claim 1, wherein there is a plurality of combustion jets.

7. The severance tool of claim 1, wherein at least one nozzle of the plurality of nozzles directs or biases the at least one jet of combustion products in a particular direction.

8. The severance tool of claim 1, wherein at least one of nozzle of the plurality of nozzles comprises a screen with a plurality of holes for creating a plurality of combustion jets.

9. The severance tool of claim 1, wherein the pressure generated by the combustion process is used to move the tool.

10. The severance tool of claim 1, wherein the plurality of nozzles is aligned such that the/each combustion jets generated on combustion of the propellant source travel in a direction which is non-perpendicular to the target surface.

11. The severance tool of claim 1, wherein the target is a tubular element and at least one nozzle is aligned such that the at least one jet of combustion products released upon combustion of the propellant source is directed at a tangent to a target internal surface.

12. The severance tool of claim 1, wherein at least one nozzle is aligned such that the at least one jet of combustion products released upon combustion of the propellant source is directed at a trajectory such that the energy of the at least one jet of combustion products is dissipated within the material from which the target is made.

13. The severance tool of claim 1, wherein at least one nozzle is aligned such that the at least one jet of combustion products released upon combustion of the propellant source is directed at a trajectory such that the energy of the at least one jet of combustion products is dissipated at or adjacent to the target internal surface.

14. The severance tool of claim 1, wherein the tool comprises a combustion chamber for carrying out the combustion of the propellant source.

15. The severance tool of claim 1, wherein the tool comprises at least one ram mounted within the housing for advancing towards the target encircled by the nozzle holder, wherein the at least one ram is configured to eject at least one jet of combustion products from a propellant source towards the target.

16. A method of severing a target, the method comprising the steps of: providing a tool having a housing and a plurality of nozzles; activating at least one propellant source by ignition, creating relative movement between the target and a nozzle holder, the nozzle holder being adapted to hold the nozzles, to centralise the target with respect to the nozzle holder; and severing the target by igniting the at least one propellant source, wherein, upon ignition, the at least one propellant source deflagrates, creating at least one jet of combustion products, which, in use, flows out of the severance tool through the plurality of nozzles to sever the target.

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 schematic of an oilwell incorporating a tool for severing or assisting in the severing of a conduit according to a first embodiment of the present invention;

(3) FIG. 2 is a section of the tool of FIG. 1;

(4) FIGS. 3 to 5 are sections of the tool of FIG. 1 in operation;

(5) FIG. 6 is a section of a tool for severing or assisting in the severing of a conduit according to a second embodiment of the present invention

(6) FIGS. 7 and 8 are sections of part of the tool of FIG. 6 in operation;

(7) FIG. 9 is a section of a tool for severing or assisting in the severing of a conduit according to a third embodiment of the present invention; and

(8) FIGS. 10 to 13 are sections of part of the tool of FIG. 9 in operation.

DETAILED DESCRIPTION OF THE DRAWINGS

(9) Reference is first made to FIG. 1, a schematic of an oil well generally indicated by reference numeral 5, incorporating a tool 10 for severing or assisting in the severing of a conduit 12 according to a first embodiment of the present invention.

(10) The tool 10 is part of a well string 14 providing fluid communication between a reservoir 16 and a rig 18. The primary components of the conduit 14 are a riser 20, the tool 10 and a wellbore 22 lined with a casing 24.

(11) The rig 18 floats on the sea 26 and receives hydrocarbons from the reservoir 16 which flow into the well string 14, as indicated by the arrow 28, and particularly into the conduit 12, towards surface.

(12) Referring now to FIG. 2, a section of the tool 10, the tool 10 is an integral part of the blowout preventer (BOP) and comprises a housing 30 defining a void 32. The void 32 is a through bore 34 fully encircling the conduit 12. Located within the housing 30 is a first propellant source 36 and a second propellant source 38.

(13) A housing internal wall 40 defines a first circumferential void access (nozzle) 42 having an inlet 44 in fluid communication with a housing interior 46 and an outlet 48 in fluid communication with the through bore 34. Similarly the housing internal wall 40 defines a second circumferential void access (nozzle) 50 with an inlet 52 and an outlet 54, the second circumferential void access (nozzle) 50 providing fluid communication between the housing interior 46 and the through bore 34.

(14) The tool 10 further comprises a first shear ram 58 and a second shear ram 60, the purpose of which will be discussed in due course, and a trigger or ignition mechanism 56 for igniting the first and second propellant sources, 36, 38.

(15) The tool 10 is activated in a well control emergency in which it is necessary to seal the wellbore 22 by closing the shear rams 58, 60. This requires severance of the conduit 12.

(16) The propellant sources 36, 38 are potassium perchlorate. Upon ignition by the ignition mechanism 56, the propellant sources 36, 38 deflagrate, forming a hot gas of combustion products which, due to the confines of the housing 12, is highly pressurised. The propellant sources 36,38 further comprise a modifying material in the form of a metal, in this case silver (not visible) embedded in the potassium perchlorate. The deflagration process heats the silver until the silver becomes molten.

(17) The highly pressurised combustion products produced by the deflagration of the potassium perchlorate flows away from the propellant sources 36, 38 at great velocity as a stream of combustion products carrying with it the molten silver modifying material.

(18) The streams of combustion gases carrying the molten silver modifying material can be seen with reference to FIG. 3, a section of the tool 10 showing the beginning of the process of severing a conduit 12.

(19) The propellant sources 36, 38 have been ignited by the ignition mechanism 56 and the propellant sources 36, 38 have released a first stream and a second stream of combustion products 62, 64 containing the molten silver modifying material.

(20) The streams of combustion products 62, 64 flow towards, and impinge on, the housing internal wall 40. Part of the streams of combustion products, 62, 64 flow through the first and second circumferential void accesses (nozzles) 42, 50 and impact on the conduit 12.

(21) The gas within the streams of combustion products 62, 64 heats the conduit 12 and the modifying material melts the conduit 12. As the conduit melts, the streams of combustion products 62,64 move the molten material away revealing and further melting conduit material. Through this process, conduit 12 is severed or at the very least softened by the streams of combustion products 62, 64 containing the modifying material in the form of molten silver.

(22) As shown in FIG. 4, the streams of combustion products 62, 64 containing the molten silver modifying material, work through the conduit 12 until, as shown in FIG. 5 the first and second propellant sources 36, 38 have been fully deflagrated, the conduit 12 has been severed and the shear rams 58, 60 can close sealing the through bore 34.

(23) Reference is now made to FIG. 6, a section of one side of a tool 110 according to a second embodiment of the present invention.

(24) The tool 110 is similar in many ways to the tool 10 of the first embodiment and rather than repeat the structural similarities, the primary differences will be highlighted.

(25) The tool 110 has a single circumferential void access (nozzle) 142 defined by the housing internal wall 140. The circumferential void access (nozzle) 142 has a seal sleeve 166 covering the circumferential void access (nozzle) 142 to prevent ingress of well fluids from the through bore 134 into the housing interior 146.

(26) There are three propellant sources 168, 170, 172 shown in FIG. 6. The upper and lower sources 168, 172 produce a gas, the purpose of which will be discussed in due course. The middle propellant source 170 is of similar construction to the propellants 36, 38 of the first embodiment, and produces a similar effect.

(27) The tool 110 further comprises a positioning mechanism 173 in the form of a plurality of arms, as centralising means, of which one is visible in FIG. 6. These arms are pressed against the conduit 112 to bring the conduit into the optimum position for severance.

(28) The operation of the tool 110 will now be described. To give the propellant 170 the best environment in which to sever the conduit 112, it is it is desirable to remove any well fluids in the through bore 134.

(29) Referring to FIG. 7, the conduit has been positioned in the optimum position with respect to the tool 110 by the positioning mechanism 173. Once positioned, the upper and lower gas producing propellant sources 168, 172 are ignited by the ignition mechanism (not visible) creating a flow of high pressure combustion gas 174. This pressurises the seal sleeve 166 (not shown in FIG. 7) until the seal sleeve 166 ruptures and the gas 174 escapes through the void access (nozzle) 142 into the through bore 134, driving well fluids away from the propellant source stream of combustion products and modifying material (shown in FIG. 8).

(30) Referring to FIG. 8, a potassium perchlorate propellant 170 is then ignited by an ignition mechanism (not visible) and a stream of combustion products carrying a modifying material 164, in this case garnet, flows towards the conduit 112. The high pressure combustion gas 174 formed from the deflagration of the upper and lower gas producing propellant sources 168, 172 channels the stream of combustion products 164 towards the target. On impact with the conduit 112, the garnet modifying material is in solid form and removes material from the conduit 112 by abrasion.

(31) The use of the combustion gas 174 reduces friction between the stream of combustion products carrying a modifying material 164 and the housing wall 140 around the void access (nozzle) 142. This maximises the energy of the stream of combustion products 164, thereby increasing the efficiency of the severing of the conduit 112.

(32) FIG. 9 shows a third embodiment of a tool 210 for severing through a conduit 212. In this case the tool 210 is fitted to the outside of a tubular 276 through which the conduit 212 passes. The conduit 212 has an increased diameter portion 278 which, in essence, is a non-shearable object in that the increased diameter portion 278 is too thick for a conventional BOP to sever using conventional shear rams.

(33) The tool 210 utilises three potassium perchlorate propellant sources 268, 270, 272, each propellant source being associated with a void access or nozzle 280, 282, 284, each void access or nozzle 280, 282, 284 being arranged to channel a stream of combustion products and a molten silver modifying material (not shown in this Figure but discussed in due course) towards a different focal point, progressively an increasing distance away from the tool 210. The plurality of void accesses or nozzles 280, 282, 284 are provided on housing internal wall 240, that acts as nozzle holder.

(34) The tool 210 further comprises an ignition mechanism 238 and a first and second barrier 286, 288. The barriers 286, 288 prevent one propellant source 268, 270, 272 igniting an adjacent propellant source 268, 270, 272 as will be shown.

(35) The operation of the tool 210 will now be described with reference to FIG. 10.

(36) As shown in FIG. 10, the first propellant source 270 has been ignited by the ignition mechanism 238 and a first stream of combustion products and modifying material 290 flows through the first void access (nozzle) 280, first piercing the tubular 276 and then moving material from the conduit increased diameter portion 278.

(37) Referring to FIG. 11, the first propellant source 270 has completed deflagration and the flame transfers up a first fuse 292 inside the second barrier 288 to the second propellant source 272 which deflagrates producing a second stream of combustion products and modifying material 294 which flows through the second void access (nozzle) 282, first piercing the tubular 276 and then moving material from the conduit increased diameter portion 278. It will be noted that the focal point of this second stream of combustion products and modifying material 294 is deeper into the conduit increased diameter portion 278.

(38) Referring to FIG. 12, the second propellant source 272 has completed deflagration and the flame transfers up a second fuse 296 inside the ignition mechanism 238 to the third propellant source 268 which deflagrates producing a third stream of combustion products and modifying material 298 which flows through the third void access (nozzle) 284, first piercing the tubular 276 and then moving material from the conduit increased diameter portion 278. It will be noted that the focal point of this third stream of combustion products and modifying material 298 is deeper again into the conduit increased diameter portion 278.

(39) Finally referring to FIG. 13, upon completion of the deflagration of the third propellant source 268, the conduit 212 is severed.

(40) Various modifications and improvements may be made to the above described embodiments without departing from the scope of the invention. For example, although the tool is described integrated into a blow out preventer (BOP), to form an integral part of the BOP, the tool may be positioned adjacent a BOP. In other embodiments it can be used with other suitable well control equipment, for example a rigless/riserless well intervention system or in other locations such as with a riser or as part of a downhole completion.

(41) When used with a riser, the tool may form an integral part of the riser. In some embodiments the tool may sever the riser itself in an emergency, including all the control lines and other equipment items. For this functionality it may also include a sealing mechanism to seal off the riser itself and prevent a spill of the fluids in the riser to sea.

(42) Similarly, when integrated into a downhole completion to form an integral part of the downhole completion the tool may also include a sealing mechanism to seal off the well itself to prevent fluids travelling up the wellbore to surface.

(43) In all of these locations the tool may act as the primary method for severing shearable and/or non-shearable items that may be passing through the tool void.