METHOD OF REMOVING MATERIALS BY THEIR DISINTEGRATION BY ACTION OF ELECTRIC PLASMA

Abstract

A method of removing materials by their disintegration, especially metal tubes and non-metal materials, particularly in an area of a borehole, by thermal disintegration of materials by action of plasma created in a plasma generator, by hydrodynamic and/or gravitational removing of disintegrated materials from the area of the borehole, characterized in that a directed flow of water vapour-based plasma acts on material being disintegrated and disintegrates it by synergetic simultaneous effect of thermal action and exothermic chemical reactions.

Claims

1. A method of removing materials, especially metal tubes and non-metal materials, in an area of a borehole by disintegration of the materials by action of plasma created in a plasma generator, by hydrodynamic action and/or gravitational removing of disintegrated materials from the area of the borehole, wherein an electric arc generated between a first electrode and a second electrode is rotationally distributed along the perimeter of the first electrode, wherein a plasma-forming medium bypasses the electric arc and the electric arc generates a planary shaped and spatially directed flow of generated water vapour based plasma, whereby a hydrodynamic stream of the plasma-forming medium pushes the generated water vapour based plasma to materials being removed and the generated water vapour based plasma by its movement in an annular sheet acts on the materials being disintegrated and disintegrates the materials by synergetic simultaneous effect of thermal action and exothermic chemical reactions.

2. The method of removing materials according to claim 1, wherein assisting additives are admixed into the plasma-forming medium.

3. The method of removing materials according to claim 2, wherein the assisting additives are fed together with the plasma-forming medium directly into the plasma generator, are fed into the flow of the generated water vapour based plasma, and/or are fed into an outflow channel.

4. The method of removing materials according to claim 3, wherein the assisting additives contain an electrically conductive material comprising Fe, Al, and/or Cu, and wherein the assisting additives continually create an electric conductive layer at an exposed surface of the material being removed.

5. The method of removing materials according to claim 1, wherein the flow of the generated water vapour based plasma and the movement of the root of the electric arc over the surface of the material being disintegrated are also directed by a directing magnetic field.

6. The method of removing materials according to claim 1, wherein the hydrodynamic stream of the plasma-forming medium, generated water vapour based plasma, and water vapour generated in the plasma generator, removes by dynamical effect the attenuated and degraded material in a casing of the borehole.

7. The method of removing materials according to claim 1, wherein the resulting disintegrated and degraded material is removed gravitationally.

8. The method of removing materials according to claim 1, wherein the materials comprise the metal tubes and the metal tubes comprise a coaxial system of tubes, wherein the coaxial system of tubes is removed in such manner that the root of the electric arc is moved continuously from one tube of the coaxial system towards another tube of the coaxial system with a larger diameter.

9. The method of removing materials according to claim 1, wherein a pulsating voltage is conveyed into the electric arc by the plasma generator.

10. The method of removing materials according to claim 1, wherein the method is performed in water and/or a vapour-based environment.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0067] FIG. 1 Set and configuration of the equipment for disintegration of the borehole casing by electrically generated plasma from the plasma generator.

[0068] FIG. 2 Configuration of the plasma generator—diagonal circumferential disintegrating head.

[0069] FIG. 3 Configuration of the plasma generator for the oriented removing of casing in order to create the sector for branching off and new implementation of the borehole.

[0070] FIG. 4 The scheme of model of interactions in the process of disintegration of steel by the electric arc.

EXAMPLES OF EMBODIMENTS

Example 1

[0071] The technological process of the contactless disintegration and removing of metal and non-metal materials of the casing and the objects in the area of the borehole by thermal and thermo-chemical effect is disclosed. The nature of preferred embodiment of the invention described herein consists in that the steel material of the casing being disintegrated is heated and exposed to the action of plasma and to the stream of the medium connected with the plasma. This medium is generated from a plasma-forming and assisting medium and thereafter, in the planar, annularly-shaped and directed discharge from the plasma generator, it is directed and emitted to the surface of the casing being disintegrated, while in contact with the melted steel material the exothermic reactions occur at the surface of steel and thus the steel is disintegrated. Besides the generating of the thermal effect itself, the non-negligible function of the process of disintegration by electrically generated plasma is the creation of the thrust of the flowing medium through the plasma stream, the assisting medium and the magnetic field, which participate in its pushing to the casing, their interaction with the steel casing and subsequently they provide raising and transport of the disintegrated and chemically transformed parts of the casing out of the place of disintegration.

[0072] The system providing the technological process of disintegration in the example (FIG. 1) of the embodiment contains the following main procedural parts: [0073] Generating the electric arc 14, which is the source of plasma 11 [0074] Shaping and forming of the plasma 11 stream and the electric arc 14 at the surface being disintegrated by using the magnetic field 17 of directing and forming elements: electrodes, magnets, which act on the electric arc 14 by force and shape it in the area between the permanent electrode 11 and alternating electrodes 12 or 12′. For the transferred mode, the electrode 12′ is represented by metal wall 7 of the casing itself and for non-transferred mode it is the electrode 12, which is the part of the plasma generator 10. [0075] Admixing the assisting additives 16 into the plasma-forming medium 15, which create the heat in oxidation of metals and push the combustion products out of the area 4 of disintegration. [0076] The thermal and thermo-chemical processes occur in the interactive area 4 of disintegration, where additives react with the material of the casing 7, 8, and thereby they disintegrate it. [0077] Removing of the attenuated and disintegrated material by streams of the main plasma flow and auxiliary streams fulfilling the protective function in relation to the parts of the generator 10. The effect of the hydrodynamic action of the flow of plasma for removing the attenuated parts of the casing is intensified by pulse mode, which is characterized by pulse power discharges conveyed into the electric arc and into the stream of plasma-forming medium as well. Before raising to the outflow channel 6, the part of fragments is removed gravitationally to the borehole bottom. [0078] The secondary reactions occur in the outflow channel 6 and in the neutralization area 5, when the free fractions of the raising gasses are eliminated, and the initial cooling, condensation and the subsequent directing and raising of disintegrated fragments of the casing take place.

[0079] The borehole 1 is formed by the casing consisting mostly of steel casing pipes of various diameters which are sunk into each other and are made of high-alloyed steel according to specifications of API (American Petroleum Industry) standards and of concrete 8, which is filling the space between the geological formation 2 and the casing pipe. High-alloyed steels of the casing pipe contain the high proportion of the alloying elements, which improve the thermal and strength properties of resulting austenitic structure. The equipment 3 for disintegration is inserted into the borehole 1 and anchored into its walls by using fixation arms 9, which provide the anchoring of the equipment in the borehole and its subsequent movement in the axial and radial direction towards the axis of the borehole 1. The process of disintegration of the metal objects is provided by the interaction of all discharging media from the plasma generator 10, especially of plasma medium 15 and casing being disintegrated, namely by shaping and adding of assisting additives of the plasma flow, which is generated in the plasma generator 10 in the end part of the equipment 3. The generated plasma 11 is being pushed in the determined area of the annulus from the outlet of the plasma generator 10 towards the casing being disintegrated.

[0080] Plasma 11 is generated between the surfaces of the electrodes 12, 13 in the plasma generator 10, whereby the plasma-forming medium bypasses the electric arc, rotationally conveyed along perimeter of the electrode 12. The stream of plasma 11 is shaped by the plasma generator 10 and by geometry of the working space along the perimeter of the outlet and is directed radially to the cylindrical wall of the casing. The plasma stream 11 is planary distributed to the surface of the casing.

[0081] Under the influence of thermal effect and by action of mainly oxidative and assisting additives in contact with material of the casing, the plasma 11 causes especially exothermic chemical reactions at the steel casing itself and at the concurrent releasing, the heat disintegrates the exposed material. After delivery of the heat and reaching temperatures over 2900° C., depending upon the amount of alloying elements present in the steel bonds between ferritic and alloyed components are unbound and released and new bonds with the assisting additives are formed, the assisting additives create the slug after cooling down. For heating, especially of steels with the high proportion of alloying elements of chromium, the required temperature to make it boil is 4000° C., by which its structural decomposition is reached. The assisting additives in the mixture of medium being directed provide the control of the course of the reactions and the bounding of non-desirable, especially gas, media in the outflow channel 6. During and especially after the disintegration of the steel casing 7 the filling of concrete-cement 8 is disintegrated as well by thermal influence up to the geologic formation 2.

[0082] The effect of the disintegration of the steel casing 7 is enhanced by erosive effect of the root of the electric arc 14. The electric arc 14 is transferred in the initiation and partial working phase between electrodes 12 and 13 in the plasma generator 10. From there it is subsequently transferred by the action of hydrodynamic flow of the plasma-forming medium 15 to the close proximity of the surface of casing being disintegrated. After transferring the arc from the plasma generator 10 and by setting the required electric potentials of the same polarity for the electrodes 12 and 12′, the transferred root of the arc is moved from the electrode 12 to the steel casing 7 being removed, which thus functions as an separate electrode 12′. The metal materials Cu, Fe which ensure the conductive way for the electrode 12′, are added to the melted and disintegrated part of the casing. These mechanisms are preferably used in the multi-layered coaxial structures of the casing and especially in the place of overlapping of the reduced perimeter of casing, where the electric arc 14 is transferred among non-conductively connected casing pipes.

[0083] The effect of the distribution of the generated plasma 11 is enhanced by directed movement of the electric arc 14, which is achieved by the magnetic field 17 being created by permanent magnets in cooperation with the discharging stream of the generated plasma 11 and plasma-forming medium 15.

[0084] By effect of the root moving along the steel casing pipe, which also functions as the electrode 12′, the electric arc is pushed by the stream of medium to the surface of the non-metal material, which mostly is filling concrete, and while being in contact with it, the electric arc causes disintegration of this material.

[0085] The additives (fluid, gas, and solid fractions) are being added into such shaped and generated plasma 11 and they effectively attenuate the material of the casing during the thermo-chemical effect and the material is subsequently hydrodynamically removed and flushed out of the area 4 of disintegration by using the stream of plasma 11. After the interaction with plasma, the thermo-mechanical disintegration occurs and it is combined with fast, cyclically repeated or pulse heating, cooling down of the melted and purposefully chemically and structurally transformed material, which allows to the formed oxides and attenuated parts of casing, because of the different thermal expansivity, the formation of cracks and fissures and the peeling off the fragments. At the rapid changes of the temperatures in the melted material of the casing of melted gas additions with hydrogen and oxygen content, the mechanical processes of attenuation, stressing, and contamination occurs, by which the strength properties of the disintegrated casing are lowered. The hydrodynamic effect of the generated stream of plasma 11 enhances the dynamic effect of removing the attenuated materials of the casing 7 by pulse mode, wherein the pulsating voltage is conveyed into the electric arc 14 by the plasma generator 10.

Example 2

[0086] The process of the contactless oriented disintegration and removing of especially metal materials of the casing and objects in the area of the borehole 1 by direct simultaneous action of the thermal and exothermic thermo-chemical reactions and the subsequent disintegration, attenuation, melting by partial and total disintegration of the part of the casing for the branching off and the new introduction of the borehole is disclosed. The example of the embodiment is schematically depicted in the FIG. 3.

[0087] The nature of herein described preferred embodiment of the invention consists in that, the object being disintegrated, in this case especially the part of the steel borehole casing 7 and the filling concrete 8 are heated by the planary shaped and spatially directed flow of the plasma 11, which is formed by active particles of the water vapour dissociated by the electric arc and thereby formed mixture of the oxidative environment. Beside the thermal degradation of the material being disintegrated, the oxidative exothermic chemical reactions take place simultaneously in the area of disintegration 4. The final product of these reactions are mainly oxides FeO, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, Cr.sub.2O.sub.3 and others, formed from the alloying elements. The process of disintegration of the casing is performed in the water based and partially vapour based environment, in which the stream of the plasma medium partially melts and by oxidation degrades the exposed steel material and subsequently removes the products of combustion and oxidation. The method of the embodiment of the invention for the oriented removing of the casing in order to create the window/sector for branching off and the new introduction of the borehole.

[0088] The system, which provides the technological process of disintegration consists of the following main parts: [0089] Generating the plasma 11 by the electric arc 14 fed from the plasma-forming medium 15 [0090] Shaping and forming the stream of plasma 11 and of the electric arc 14 to the surface being disintegrated, the part of which are hydrodynamically (by using the plasma 11) and by the magnetic field 17 directing and forming elements—electrodes, discharge nozzles, magnets, which act on the electric arc 14 by force and they shape it in the area between the permanent electrode 13 and the alternating electrode 12,12′ for the non-transferred (transferred) mode, when for the transferred mode, one of the alternating electrodes 12,12′ is represented by the casing metal wall of the itself and for the non-transferred mode it is the electrode 12 in the plasma generator 10. [0091] Admixing the assisting additives 16 into the plasma-forming medium 15, which create the heat in the oxidation of metals and push the combustion products. [0092] The thermal and thermo-chemical processes occur in the interactive area of disintegration, where the oxidizing additives and contaminative additions react with the materials of the casing 7, 8, and thereby they disintegrate it. [0093] Removing of the attenuated and disintegrated material is ensured by its gravitational removing—by falling down into the borehole. When non-separated parts solidify, their thermo-chemical disintegration occurs at the temperature changes, and this disintegration is initiated by different volume changes. The parts of the attenuated material are arising and their fragments are easily separable by the hydrodynamic stream of medium and mechanic scrapers. These are removed from the place of disintegration by the hydrodynamic stream of plasma 11, the extincting plasma and the discharge medium. [0094] The secondary reactions occur in the outflow channel 6 and in the neutralization area 5, wherein the free fractions of gasses are eliminated, the initial cooling, condensation and the subsequent directing and raising of the disintegrated fragments of the casing take place.

[0095] The borehole 1 is formed by the steel casing pipe and the cement 8, which is filling the space between the geological formation 2 and the casing pipe. The equipment for disintegration 3 is inserted into the borehole 1 and anchored to the walls of the borehole 1 by using the fixations arms 9, which provide the anchoring of the equipment in the borehole 1 and its subsequent movement in the axial and radial direction towards the axis of the borehole 1. The process of disintegration of the metal objects is provided by the interaction of all discharging media from the plasma generator 10, especially of plasma medium 15 and the surface of casing being disintegrated, namely by shaping and adding of the assisting additives to the plasma flow, which is generated in the plasma generator 10 in the end part of the equipment 3. The generated plasma 11 is being pushed in the determined area of the annulus from the outlet of the plasma generator 10 towards the casing being disintegrated. Plasma 11 is generated between the surfaces of electrodes 12, 13 in the plasma generator 10, whereby the plasma-forming medium bypasses the electric arc, rotationally conveyed along perimeter of the electrode 12 and its discharge is directed in the planary concentrated cone to the place of the interaction with the casing. Plasma 11 disintegrates the casing by the thermal influence and by the action of the exothermic chemical processes, especially oxidative reactions with the steel material. During and especially after the disintegration of the steel casing 7 the filling of concrete-cement 8 is disintegrated as well by the thermal influence up to the geologic formation 2. The discharging plasma cake is limited by its spatial distribution to the disintegration of the chosen part of casing, wherein by its movement in the axial and radial course, the surface of the part of the casing being disintegrated is determined, in such manner that it preferably disintegrates the part of the casing designed for the forming of the aperture and removing of the casing in the place of branching of the borehole.

[0096] The effect of disintegration of the steel casing 7 is enhanced by erosive effect of the root of the electric arc 14. The electric arc 14 is transferred in the initiation and partial working phase between cathode and anode 12 and 13 in the plasma generator 10. From there it is subsequently transferred by the action of hydrodynamic flow of the plasma-forming medium 15 to the close proximity of the surface of casing being disintegrated. After transferring the arc from the plasma generator 10, and by setting the required potentials of the same polarity between the electrodes 12 and 12′, the transferred root of the arc is moved from the electrode 12 to the steel casing 7 being removed, which thus functions as an separate electrode 12 During movement of the electric arc 14 over the surface of the casing, in the interaction with oxidizing gasses, explosive melting up and exfoliating of the parts of the disintegrated casing occur. The processes occurring at strong oxidation causes rapid explosive reaction, during which the parts of melt, formed slagging compounds and combustion products are being ripped from the disintegrated surface of casing. Some fractions of the combustion products and oxidised products condensate at cooling down to the fine powder.

[0097] The effect of the distribution of the generated plasma 11 is enhanced by directed movement of the electric arc 14, which is achieved by the magnetic field 17 being created by permanent magnets in cooperation with the discharging stream of the generated plasma 11 and plasma-forming medium 15.

[0098] The additives (fluid, gas, and solid fractions) are being added into such shaped and generated plasma 11 and they effectively attenuate the material of the casing during the thermo-mechanical and thermo-chemical effect and the material is subsequently hydrodynamically removed and flushed out of the area 4 of disintegration. After the interaction with plasma, the thermo-mechanical disintegration occurs and it is combined with fast, cyclically repeated or pulse heating, cooling down of the melted and purposefully chemically and structurally transformed material, which allows to the formed oxides and attenuated parts of casing, because of the different thermal expansivity, the formation of cracks and fissures and the peeling off the fragments. At the rapid changes of the temperatures and at forming secondary gas additions with hydrogen and oxygen content, the thermo-mechanical processes of disintegration, stressing, and contamination occurs, in order to lower strength properties of the disintegrated casing, whereby stiffer fraction are mechanically removed by scraper and raking knife 18.

[0099] Cooled down and embrittled material, that remained in contact with the wall of casing is by axial and rotational move of the plasma generator scraped by the raking knife 18 located on the opposite, cold side of the plasma generator.

REFERENCE SIGNS

[0100] 1 Borehole [0101] 2 Geologic formation—naturally grown geologic rock [0102] 3 Equipment for disintegration of casing objects [0103] 4 Field of action—area of disintegration [0104] 5 Through area (reaction-neutralizing) [0105] 6 Outflow channel [0106] 7 Steel part of casing [0107] 8 Casing—cement/concrete [0108] 9 Fixation anchorage/arms [0109] 10 Plasma generator [0110] 11 Generated plasma [0111] 12 Electrode—in non-transferred arc mode—temporary/working [0112] 12′ Electrode—for transferred arc mode, with conductive interconnection of the casing—supply contact of electric potential to the casing [0113] 13 Permanent electrode [0114] 14 Electric arc [0115] 15 Flow of plasma-forming medium [0116] 16 Flow of additives, additions (of secondary medium) [0117] 17 Directing magnetic field [0118] 18 Disintegrative mechanical tool—raking knife [0119] 19 Slag in the melt [0120] 20 Slag-steel interface [0121] 21 Separated slag [0122] 22 Exfoliated melt [0123] 23 Combustion products [0124] 24 Gas-slag interface [0125] 25 Thermo-chemical interface