WO2015105739A1

WO2015105739A1 - Severance tool

Info

Publication number: WO2015105739A1
Application number: PCT/US2015/010098
Authority: WO
Inventors: Curtis Len Wilie; Rae Andrew Younger; Jamie George Oag
Original assignee: Shell Oil Company; Shell Internationale Research Maatschappij B.V.
Priority date: 2014-01-07
Filing date: 2015-01-05
Publication date: 2015-07-16

Abstract

A severance tool for severing a target, comprising: one or more shaped charges, the one or more shaped charges being adapted to detonate upon receipt of an activation signal, the one or more shaped charges being adapted to release energy on detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the one or more shaped charges; and at least one trigger adapted to send the activation signal to the one or more shaped charges and associated methods.

Description

SEVERANCE TOOL

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 61/924,599, filed January 7, 2014, which is incorporated herein by reference.

BACKGROUND

[0002] The present disclosure relates to a tool for severing a target. More particularly, the present disclosure relates to a tool for severing a tubular element.

[0003] During hydrocarbon extraction operations, safety equipment may be installed for utilization in the event of catastrophic failure to prevent damage to human life and the environment. This may be particularly the case for subsea hydrocarbon extraction where the presence of water can carry contamination from an oil well many thousands of miles potentially causing huge environmental damage.

[0004] In emergency situations it is often desirable to be able to sever a tubular in a wellbore. Particularly it is often desirable to sever a workstring at a location above the blowout preventer stack such that the lower part of the workstring can drop down below the blowout preventer stack allowing the blowout preventer to close more effectively than if the workstring was in the path of the blowout preventer rams, and secure the well.

[0005] U.S. Patent Number 5,253,585 discloses that a main charge of explosive may be positioned symmetrically about a passageway-forming tubular member, such as a well pipe assembly. The charge may be outwardly and radially spaced from the member and may be coupled thereto by a dense medium, such as soil, which may be adapted to transfer the produced explosive energy to the tubular member in the form of a pressure pulse applied by the medium. Initiation charges may be supplied at the outer surface of the main charge, to initiate a detonation wave directed at the tubular member. A layer of dense medium may be provided to confine the non-coupled surface of the charge and retard venting of explosive gases away from the tubular member. In the end result, concentrated, converging pressure pulses may be applied to the tubular member on detonation, to cause it to be symmetrically crimped to restrict the passageway. U.S. Patent Number 5,253,585 is herein incorporated by reference in its entirety.

[0006] U.S. Patent Number 7,779,760 discloses a shaped charge assembly that comprises a housing, first shaped charge, a wave shaping relay charge and a second shaped charge located in the housing. The assembly may be configured such that a first active element formed by initiation of the first shaped charge causes detonation of the wave shaping relay charge, which in turn causes initiation of the second shaped charge to form a second active element. The first active element may move beyond a second end of the housing to cause damage of a first kind to an external target and the second active element also may move beyond the second end to cause damage of a second kind to the target. U.S. Patent Number 7,779,760 is herein incorporated by reference in its entirety.

[0007] U.S. Patent Number 5,251,702 discloses a surface controlled, subsurface safety valve in which a force due to control pressure fluid from a first source at the surface for opening the valve is opposed in part by a force due to reference pressure fluid from a second source at the surface, whereby the valve closes in response to a fail condition. U.S. Patent Number 5,251,702 is herein incorporated by reference in its entirety.

[0008] It has been found that linear shaped charges, particularly when closing in on a tubular target, may lose energy as they pass through the medium between the charge and the tubular element. Furthermore, adjacent charge material may coalesce on the target as the charge material converges resulting in uneven impact on the target resulting in non-uniform and inconsistent cutting. To overcome these problems, high amounts of explosives may be required making the produce more dangerous and costly than it otherwise would be.

[0009] Thus, there is a need in the art for one or more of the following: improved systems and methods for severing tubular elements; improved systems and methods for remotely severing tubular elements; improved systems and methods for remotely severing tubular elements when the tubular elements are in a subsea well; and/or improved systems and methods for remotely severing tubular elements when the tubular elements are suspended above a subsea well that is flowing oil and gas at an undesirable rate.

SUMMARY

[0010] The present disclosure relates to a tool for severing a target. More particularly, the present disclosure relates to a tool for severing a tubular element.

[0011] In one embodiment, the present disclosure provides a severance tool for severing a target, comprising: one or more shaped charges, the one or more shaped charges being adapted to detonate upon receipt of an activation signal, the one or more shaped charges being adapted to release energy on detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the one or more shaped charges; and at least one trigger adapted to send the activation signal to the one or more shaped charges.

[0012] In another embodiment, the present disclosure provides a well emergency separation tool for separating a tubular element, comprising: at least one shaped charge, the shaped charge being adapted to detonate upon receipt of an activation signal, the shaped charge being adapted to release energy on detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the shaped charge; and at least one trigger adapted to send the activation signal to the shaped charge.

[0013] In another embodiment, the present disclosure provides a method of severing a target, the method comprising the steps of: providing at least one shaped charge, the shaped charge being adapted to detonate upon receipt of an activation signal; transmitting an activation signal to the shaped charge such that the shaped charge detonates, the shaped charge releasing energy upon detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the shaped charge.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings.

[0015] Figure 1 is a schematic diagram of a well emergency separation tool positioned above a subsea reservoir in accordance with certain embodiments of the present disclosure.

[0016] Figure 2 is a schematic diagram of the internal structure of the well emergency separation tool of Figure 1.

[0017] Figure 3 is a schematic diagram of the charge carrier used in the well emergency separation tool of Figure 1.

[0018] Figure 4 is a schematic diagram of the internal structure of the well emergency separation tool of Figure 1 after detonation of the shaped charges.

[0019] Figure 5 is a schematic diagram of the internal structure of well separation tool after detonation of a plurality of shaped charges in accordance with certain embodiments of the present disclosure.

[0020] Figure 6 is a schematic diagram of the internal structure of a well separation tool in accordance with certain embodiments of the present disclosure.

[0021] Figure 7 is a schematic diagram of the internal structure of the well separation tool of Figure 6 after inflation of the air bladder.

[0022] Figure 8 is a schematic diagram of the internal structure of a well separation tool in accordance with certain embodiments of the present disclosure.

[0023] Figure 9 is a schematic diagram of the internal structure of a well separation tool in accordance with certain embodiments of the present disclosure.

[0024] The features and advantages of the present disclosure will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the disclosure.

DETAILED DESCRIPTION

[0025] The description that follows includes exemplary apparatuses, methods, techniques, and/or instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details.

[0026] The present disclosure relates to a tool for severing a target. More particularly, the present disclosure relates to a tool for severing a tubular element.

[0027] In one embodiment, the present disclosure provides a severance tool for severing a target, comprising: one or more shaped charges, the one or more shaped charges being adapted to detonate upon receipt of an activation signal, the one or more shaped charges being adapted to release energy on detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the one or more shaped charges; and at least one trigger adapted to send the activation signal to the one or more shaped charges.

[0028] In certain embodiments, providing one or more shaped charges to sever, for example, a well tubular provides for greater control over the severing process because the shape of the one or more charges substantially determines the direction of the energy released by the one or more charges on detonation.

[0029] In certain embodiments, the released energy may be in the form of a Shockwave. The released energy may be in the form of a jet of material. The jet of material may be a high velocity jet of material. The jet of material may include, but is not limited to, a metallic material, a glass material, a ceramic material or any suitable material. In certain embodiments, the jet of material may be a combination of materials.

[0030] In certain embodiments, the first portion of the released energy may be more than 50% of the energy released by the detonation. In certain embodiments, the first portion of the released energy may be more than 75% of the energy released by the detonation.

[0031] In certain embodiments, the first direction may, in use, be towards a first target location.

[0032] In certain embodiments, upon detonation the one or more shaped charges may release a second portion of released energy, the second portion being released in a second direction. The second direction may, in use, be towards a second target location, the second target location being different to the first target location.

[0033] In certain embodiments, the one or more shaped charges may define at least one geometry. In certain embodiments, the one or more shaped charges may define a plurality of geometries. The one or more shaped charges may be conical, oval, linear or any suitable shape. In certain embodiments, there is a plurality of shaped charges. In embodiments where there is a plurality of shaped charges, each of the one or more shaped charges may define a geometry or a plurality of geometries. In such embodiments, there may be one shaped charge defining a geometry or plurality of geometries which is different to another shaped charge.

[0034] In certain embodiments, where there is a plurality of shaped charges, the shaped charges may be positioned such that at least one shaped charge can be detonated in isolation from another at least one shaped charge. In certain embodiments, it may be preferable to ensure the detonation of one shaped charge does not trigger the detonation of an adjacent shaped charge. Alternatively or additionally, the geometry of each shaped charge may be selected to direct energy released on detonation away from the other shaped charge.

[0035] In at least one embodiment, at least one of said shaped charges may be adapted, in use, to be located adjacent to the target. In some embodiments at least one of said shaped charges may be adapted to be connected to the target. The charges may be connected to the target by any suitable means. For example the charges may be adhered to the target for example, or pressed into a recess provided on the target. In certain embodiments, at least one of the one or more shaped charges may be adapted to be spaced away from the target.

[0036] In certain embodiments, the severance tool may further comprise one or more charge holders adapted to hold at least part of the one or more shaped charges. The one or more charge holders may be provided, in use, to for example position the one or more shaped charge such that the first directions of the one or more shaped charges are aligned with the first target location on the target, such that upon detonation the released energy has maximum effect on impact with the target. In certain embodiments, the one or more charge holders may be adapted to hold a single charge. In certain embodiments, the one or more charge holders may be adapted to hold a plurality of charges. In such embodiments, each charge holder may be adapted to receive the least part of the shaped charge. In some embodiments, there may be a charge holder associated with each shaped charge. Alternatively there may be a single charge holder adapted to hold a plurality of charges.

[0037] In certain embodiments, the one or more charge holders may define a charge holder geometry, the charge holder geometry being selected to direct energy released from the shaped charge. The charge holder geometry may direct energy released from the shaped charge, in use, towards the target. Alternatively or additionally, the charge holder geometry may direct energy released from the shaped charge, in use, away from an undetonated shaped charge.

[0038] In certain embodiments, controlling the released energy may be important, as not all the energy released can be directed at the target. Energy which it is unable to direct at the target may trigger a detonation of another charge in the same holder or another holder. The charge holder geometry may, for example, define a convoluted path for the released energy. In some embodiments, the charge holder geometry may at least partially reflect the released energy. The charge holder geometry may be adapted to absorb at least some of the energy reflected off it.

[0039] In certain embodiments, the one or more charge holders may comprise a polymer. In certain embodiments, the one or more charge holders may comprise a metal. In certain embodiments, the metal may be steel. Alternatively or additionally the one or more charges holders may comprise a material adapted to retard the velocity of the released energy. Retarding the velocity of the released energy reduces the possibility that an adjacent charge is not detonated intentionally.

[0040] In certain embodiments, each charge holder may define at least one charge storage location. In certain embodiments, the charge storage location may be a pocket. In certain embodiments, each charge holder may define a plurality of pockets.

[0041] In certain embodiments, the severance tool may further comprise an energy attenuation device. An energy attenuation device may be provided to inhibit a flow of released energy. The energy attenuation device may be adapted to slow a flow of released energy. The energy attenuation device may comprise a solid, a composite and/or an aerated solid. Aerated solids such as foams comprise pockets of air which may slow the travel of a flow of released energy. Composite materials may also provide beneficial shock attenuation.

[0042] In certain embodiments, the severance tool may further comprise an energy damping device. The energy damping device may be provided to absorb residual energy after detonation once the target has been severed. The energy damping device may be adapted to generate a gas. The gas may be generated prior to detonation. The energy damping device may be adapted to generate the gas such that the gas is in the vicinity of the direction of travel of the released energy when the shaped charge is detonated. The gas may be generated by a combustion, injection, vibration, chemical reaction or flow of electricity. Any suitable method for generating gas may be employed. The gas may be in the form of bubbles. Bubbles of gas can absorb residual energy after detonation.

[0043] In alternative or additional embodiments, the energy damping device may comprise at least one void or cavity adapted to receive energy after detonation. The severance tool may define one or more cavities. Each cavity may be adapted to receive the released energy. The provision of a cavity provides an energy damping effect by giving a volume into which the released energy can move. Each severance tool cavity may contain a compressible substance. The compressible substance may be a compressible fluid. The compressible fluid may be a compressible gas. The compressible gas may be air. Alternatively or additionally, the compressible fluid may be a compressible liquid. The compressible liquid may be a liquid polymer. The compressible substance may be a solid. The compressible solid may be a rubber material. Alternatively or additionally, the compressible solid may be a foam or a composite. The compressible substance may be any suitable material which can compress under a force.

[0044] Each severance tool cavity may be sealed prior to detonation. Each cavity may be adapted to be opened immediately before or as a result of detonation. Each cavity may be opened by an opening signal. Each opening signal may be received prior to the activation signal. In alternative embodiments, each cavity may be opened by the activation signal. In still further embodiments the cavity may be opened by the energy released by the detonation. The cavity may comprise a closure. The closure may be adapted to open the cavity. Where the cavity is opened by the energy released by the detonation, the closure may rupture under the force of detonation.

[0045] The severance tool may comprise one or more vents. Each vent may be adapted to permit energy released by detonation to pass from a vent inlet in a location adjacent each shaped charge and/or adjacent the target to a vent outlet in a location displaced from the target. Each vent outlet location may permit energy released by detonation to be released in to the environment. Alternatively or additionally, each vent outlet location may permit energy released by detonation to be released in to a vessel such as an expansion tank or a hydraulic accumulator. The vent may permit unidirectional passage of energy. The vent may comprise a one way valve.

[0046] The energy released by detonation may, in use, pass through an environmental medium, the environmental medium being located between each shaped charge and the target to be severed. The severance tool may further comprise a preferred medium generating or storage device. Each severance tool cavity may contain a preferred medium. The preferred medium is a material which is adapted to at least partially displace the environmental medium if a preferred medium can be located, the preferred medium having a lower density than the environmental medium. It is preferred to have as low a density medium as possible on the flow path as the density of the medium affects the energy of the Shockwave, energy being absorbed by higher density materials reducing the severance energy available. The preferred medium may be a gas. The gas may be air, nitrogen, carbon dioxide or any suitable gas. Alternatively or additionally the flow path substance may be a low density fluid. For example, a light oil may be used.

[0047] Alternatively or additionally the flow path substance may be a solid. Any fluid or solid of lower density than the environmental medium will increase the energy available for severing the target as the lower density preferred medium will absorb less energy than the environmental medium. Where the preferred medium is a gas, the gas may be in the form of bubbles. Bubbles of gas are preferred as they can both provide a lower density medium through which the shock wave can travel and the bubbles can also provide a shock damping means.

[0048] The preferred medium generation or storage means may comprise a vessel adapted to store a preferred medium. The vessel may be positionable adjacent the target. The vessel may be adapted to displace the environmental medium. The vessel may be an air bladder. The air bladder may be inflatable. [0049] The severance tool may comprise a target positioning means. A positioning means may be provided to position the target in the optimum position to maximize the severance effect of the tool. The positioning means, in use, may be adapted to contact at least part of the target to move the target with respect to each shaped charge. The positioning means may include an engagement member. The engagement member may be adapted to contact the target. The engagement member may be mechanically actuated. The engagement member may be solid. Alternatively the engagement member may be resilient. The engagement member may be moveable from a first position to a second position, movement to the second position moving the target to the desired location. Alternatively, the engagement member may be fixed with respect to each shaped charge, the engagement member guiding the target to the desired location and/or restricting the target from moving away from the desired location. In alternative embodiments the engagement member may transform in moving from the first position to the second position. The engagement member may transform by inflation. In some embodiments the engagement member may be an inflatable torus, inflation of said torus centralizing the target with respect to each shaped charge. In embodiments where the shaped charges are located radially, in use, with respect to the target, the positioning means may be adapted to centralize the target with respect to the shaped charges. There may be more than one positioning means. Where there is a plurality of positioning means at least one of said positioning means may be located on either side of the target. Additionally or alternatively a positioning means may be on the direction of travel towards the target by the energy released by detonation.

[0050] In an embodiment, where the positioning means is located on the direction of travel towards the target by the energy released by detonation, the energy travels through the positioning means. This may be of benefit where the positioning means is, for example, an air filled bladder and the air is of lower density than the flow path medium. Where there is a plurality of shaped charges, the trigger may be adapted to detonate a plurality of the shaped charges simultaneously. It is believed that simultaneous detonation of more than one charge focused at a target results in an increased severance energy due to a compounding of energy at the target.

[0051] Where there is a plurality of shaped charges, the trigger may be adapted to detonate a shaped charge or a combination of shaped charges in a sequence with another shaped charge or combination of shaped charges. The shaped charges may be triggered in a sequence such as at predetermined intervals to maximize the severance effect. At least some of the energy released by each shaped charge may, in use, be directed to apply an axial force and/or torsional force to the target.

[0052] According to a second aspect of the present disclosure there is provided a well emergency separation tool for separating a tubular element, comprising: at least one shaped charge, the shaped charge being adapted to detonate upon receipt of an activation signal, the shaped charge being adapted to release energy on detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the shaped charge; and at least one trigger adapted to send the activation signal to the shaped charge.

[0053] According to a third aspect of the present disclosure there is provided a method of severing a target, the method comprising the steps of: providing at least one shaped charge, the shaped charge being adapted to detonate upon receipt of an activation signal; transmitting an activation signal to the shaped charge such that the shaped charge detonates, the shaped charge releasing energy upon detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the shaped charge.

[0054] It will be understood that features of the first embodiment may be equally applicable to subsequent embodiments but have not been repeated for brevity.

[0055] Referring now to Figure 1, Figure 1 depicts a severance tool, generally indicated by reference numeral 100, in the form of a well emergency separation tool according to a first embodiment of the present disclosure. The well emergency separation tool 100 is an element in a chain of well string 101 providing fluid communication between a reservoir 116 and a surface structure 104. The primary components of the well string 101 are a riser 102, the well emergency separation tool 100, a blowout preventer (BOP) stack 112 and a wellbore 115 lined with a casing 114. The surface structure 104 floats on the sea 106. The surface structure 104 may be, for example, a spar, a semisub, a TLP, an FPSO, a temporary or permanent storage system, a vessel, another containment apparatus, or a separator that separates components of fluid, such as gas and liquid, etc.

[0056] The surface structure 104 is fluidly connected to the well emergency separation tool 100 by the riser 102. Opposite the riser 102, the well emergency separation tool 100 is fluidly connected to a flex joint 110 by a connector element 108. The flex joint 110 extends from the connector element 108 to the BOP 112. The flex joint 110 provides a certain degree of movement of the surface structure 104 with respect to the BOP stack 112, to allow for movement of the surface structure in, for example, rough seas. The casing 114 is a tubular element fluidly connected to the BOP stack 112.

[0057] The BOP stack 112 may be any BOP stack 112 as are known in the art and commercially available, such as those provided by Cameron, Vetco-Gray, Patterson, Hydril, etc. and disclosed, for example, in U.S. Patent Number 7,410,003, herein incorporated by reference in its entirety. In normal use, fluid may flow from the reservoir 116 through the casing 114 towards surface in the direction marked by the arrow 120.

[0058] During drilling or workover operations, a workstring 122 may extend from the surface structure 104 to the casing 114. The workstring 122 is contained within the riser 102 and passes through the well emergency separation tool 100, the connector element 108, the flex joint 110 and the BOP stack 112.

[0059] Referring now to Figure 2, a schematic diagram of the internal structure of the well emergency separation tool 100 of Figure 1 is shown. The well emergency separation tool 100 comprises a plurality of shaped charges 130, each shaped charge 130 being adapted to detonate upon receipt of an activation signal from a trigger 134.

[0060] The charges 130 are held within a charge carrier 132 in a specific geometric configuration. The shaped charges 130 are positioned so that the majority of the energy released by the charges 130 is directed through a charge cover sleeve 150 towards the outer surface 152 of the tubular element 122, the released energy severing the tubular element 122, as will be shown in due course.

[0061] Referring to Figure 3, a schematic diagram of the charge carrier 132 used in the well emergency separation tool of Figure 1, the charge carrier 132 has a plurality of openings 136 for the placement of the shaped charges 130. As can be seen most clearly from this figure, the openings 136 for the shaped charges 130 are in two parallel rows 138, 140. The charge carrier 132 is designed such that energy released during detonation of the charges 130 which does not initially travel in the direction of the tubular element 122, is reflected by the charge carrier 132 such that the released energy does travel in the direction of the tubular element 122 thereby maximizing the effectiveness of the released energy in severing the tubular element 122.

[0062] Referring back to Figure 2, the charge carrier 132 and the shaped charges 130 are mounted in a containment housing 126, designed and constructed to be able to withstand the explosion of the shaped charges 130 in the well emergency separation tool 100. This construction maintains the integrity of the system and prevents flow from exiting the riser 102. The containment housing 126 defines a substantially vertical bore 142 extending from the riser 102 to the flex joint 110 (as shown on Figure 1). The outer surface of the containment housing 126 is fluidly isolated from sea 106 by a tool body 127.

[0063] Referring to Figure 4, a schematic diagram of the internal structure of the well emergency separation tool 100 of Figure 1 after detonation of the shaped charges 130, it can be seen that upon detonation, each shaped charge 130 releases energy in the form of a high velocity jet of metallic material 144. The jets of metallic material 144 are fired perpendicularly at the surface of the tubular element 122, each jet of material 144 combining with other jets of material 144 in each of the respective rows 138, 140 to form two explosive impacts with the tubular 122.

[0064] Referring to Figure 5, a schematic diagram of the internal structure of well separation tool 200 after detonation of a plurality of shaped charges 230, according to a second embodiment of the present disclosure, it can be seen from this figure that the shaped charges 230 are positioned differently in a charge carrier 232 of this embodiment such that jets of metallic material 244 released on detonation of the shaped charges 230 directed to a central point 246 in the centre of a well separation tool through bore 242. Such an arrangement allows for the energy released by detonation to be focused on a smaller region of a tubular element 222 with a potential enhanced cutting effect.

[0065] Reference is now made to Figure 6, a schematic diagram of the internal structure of a well separation tool 300 according to a third embodiment of the present disclosure. The well separation tool 300 of this embodiment is similar to the well separation tools 100, 200 of the first and second embodiment with the essential difference that the well separation tool 300 includes an air bladder 350 housed in a charge cover sleeve 380. In this embodiment, the annulus 358 between the outer surface 352 of the tubular element 322 and the internal surface 354 of the well separation tool 300 is filled with a dense liquid 356. On detonation of the charges 330, the dense liquid 356 will absorb some of the energy released by the detonation of the charges 330, reducing the cutting effect of the high velocity jet of material. As shown in Figure 7, a schematic diagram of the internal structure of the well separation tool 300 of Figure 6 after inflation of the air bladder 350, the air bladder 350 is inflated immediately prior to the detonation of the charges 330 to displace the dense liquid 356 from the annulus immediately surrounding the shaped charges 330 to provide a less energy absorbing medium (air) through which the energy released by detonation of the shaped charges 330 can travel.

[0066] Reference is now made to Figure 8, a schematic diagram of the internal structure of a well separation tool 400 according to a fourth embodiment of the present disclosure. The well separation tool 400 of this embodiment is similar to the well separation tools 100, 200, 300 of the first, second and third embodiments the essential difference that the well separation tool 400 includes a chamber 460 adapted to release pressure built up in the separation tool through bore 442 after the detonation of the shaped charges 430. Once the shaped charges 430 have detonated and severed the tubular 422, the residual energy released by the explosion can continue to cause further damage which may be undesirable. The chamber 460 is sealed from the well separation tool through bore 442 by a number of covered ports 462. The ports 462 covered by a frangible metallic cover 463 which rupture with the increase of energy in the through bore 422 allowing the released energy to pass through the ports 462 to dissipate in the chamber 460.

[0067] Referring to Figure 9, a schematic diagram of the internal structure of a well separation tool 500 according to a fifth embodiment of the present disclosure. In this embodiment, an additional use of the chamber 560 is shown. The chamber 560 contains a body of air 564 which is pumped through the ports 562 by a pump 566 when there is a dense fluid 556 in the annulus 558 to provide a curtain of bubbles 568 in the path of the energy released by the detonation of the shaped charges 530. Again this provides a less energy absorbing medium through which the energy can pass to maximize the effect of the energy and severing the tubular 522.

[0068] Various modifications and improvements may be made to the above described embodiments without departing from the scope of the disclosure. For example, it may be desired to have multiple well emergency separation tools 100 installed between the riser 102 and the BOP stack 112. A second well emergency separation tool 100 may be included for redundancy. Alternatively, additional well emergency separation tools 100 may be included if various sizes or types of workstring 122 will be utilized. It may be desirable to install several sets of well emergency separation tools 100 to increase flexibility of design. The well emergency separation tool 100 may be installed when drilling operations commence and left on the BOP stack until all completion and workover activities are finished. Alternatively, the well emergency separation tool 100 may be left on the well indefinitely and may be removed only when the well is decommissioned or when certain portions of well emergency separation tool 100 need to be repaired or replaced. The well emergency separation tool 100 is independent of traditional BOP stacks 112.

[0069] The charge carrier 132 is shown as having two rows of shaped charges. In other embodiments, the charges can be arranged in three or more rows of openings as necessary to provide a sufficient release of energy upon detonation to separate a tubular element.

[0070] While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible.

[0071] Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.

Claims

C L A I M S

1. A severance tool for severing a target, comprising:

one or more shaped charges, the one or more shaped charges being adapted to detonate upon receipt of an activation signal, the one or more shaped charges being adapted to release energy on detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the one or more shaped charges; and

at least one trigger adapted to send the activation signal to the one or more shaped charges.

2. A well emergency separation tool for separating a tubular element, comprising: at least one shaped charge, the shaped charge being adapted to detonate upon receipt of an activation signal, the shaped charge being adapted to release energy on detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the shaped charge; and

at least one trigger adapted to send the activation signal to the shaped charge.

3. A method of severing a target, the method comprising the steps of:

providing at least one shaped charge, the shaped charge being adapted to detonate upon receipt of an activation signal; and

transmitting an activation signal to the shaped charge such that the shaped charge detonates, the shaped charge releasing energy upon detonation, a first portion of the released energy being released in a first direction, the first direction being at least partially determined by the geometry of the shaped charge.