Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
APPARATUS AND METHOD FOR DISINTEGRATING THE PRODUCTION PIPE IN THE BOREHOLE
Document Type and Number:
WIPO Patent Application WO/2019/108139
Kind Code:
A1
Abstract:
The apparatus for removing the production pipe (10) in the borehole is mechanically connected by means of BHA to an electrical power supply (12), coolant supply (13), data cable (14) and control unit (15). The equipment (X) is placed in a contactless manner inside the production pipe (10) and comprises a liquid presursor supply (11) which enters the generator (5) of the plasma-forming medium connected to the nozzle system inlet (6) connected to the nozzle system (7). The nozzle system (7) is placed in the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2), and the upper electrode (1) and the lower electrode (2) are placed axially with respect to each other around the circumference of the equipment (X) and coaxially placed towards the production pipe (10), while in the axis of the upper electrode (1) and the lower electrode (2) there is around the nozzle system inlet (6) at least one magnet (4) placed above the nozzle system (7) and / or under the nozzle system (7). The method of removing the production pipe in the borehole by means of the equipment (X) is carried out in such a way that the equipment (X) is inserted into the production pipe ( 10) in the borehole, and into the equipment (X) liquid precursor (Y) is supplied through the liquid precursor inlet (11) which enters the plasma- forming medium generator (5), which changes it to the plasma-forming medium (Z), which passes through the nozzle system inlet (6) into the nozzle system (7) and is injected from the nozzle system (7) into the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2) where under the effect of the pressure in a range of 0.1 -70 MPa and temperature of the plasma-forming medium (Z) in a range of 1 -1000°C the electric arc (3) is ignited in a liquid environment between the upper electrode (1) and the lower electrode (2).

Inventors:
HORVATH, Gabriel (Cukarabon 73, Dunajska Streda, 929 01, SK)
KUCERA, Marek (Jana Smreka 10, Bratislava 49, 841 08, SK)
DVONC, Lukas (Horska 1314/46, Partizanske, 958 06, SK)
KOCIS, Ivan (Kuklovska 54, Bratislava, 841 04, SK)
SZALAY, Zsolt (Stara cesta 350/48, Samorin, 931 01, SK)
SIMO, Frantisek (Studenohorska 75, Bratislava, 972 12, SK)
BENOVSKY, Peter (Rolnicka 334, Bratislava 36, 831 07, SK)
Application Number:
SK2018/050014
Publication Date:
June 06, 2019
Filing Date:
November 26, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
GA DRILLING, A. S. (Priemyselna 5, Trnava, 917 01, SK)
International Classes:
E21B29/02
Domestic Patent References:
WO2016105279A22016-06-30
WO2011037546A22011-03-31
WO2015116343A12015-08-06
Other References:
SLAVOMIR JANKOVIC ET AL: "Use Of Plasma-Based Tool For Plug And Abandonment", SPE, 8 September 2015 (2015-09-08), pages 1 - 11, XP055563041, ISBN: 978-1-61399-398-9, DOI: 10.2118/175431-MS
Attorney, Agent or Firm:
GIRMAN IP MANAGEMENT ING. ZUZANA GIRMANOVA (Olivova 10, Nitra, 949 01, SK)
Download PDF:
Claims:
CLAIMS

1. Apparatus for removing the production pipe ( 10) in the borehole mechanically connected by means of BHA to an electrical power supply (12), coolant supply (13), data cable (14) and control unit (15) characterized in that the equipment (X) is placed in a contactless manner inside the production pipe (10) and comprises a liquid presursor supply (11) which enters the generator (5) of the plasma-forming media connected to the nozzle system inlet (6) connected to the nozzle system (7), while the nozzle system (7) is placed in the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2), and the upper electrode (1) and the lower electrode (2) are placed axially with respect to each other around the circumference of the equipment (X) and coaxially placed towards the production pipe (10), while in the axis of the upper electrode (1) and the lower electrode (2) there is around the nozzle system inlet (6) at least one magnet (4) placed above the nozzle system (7) and / or under the nozzle system (7).

2. The apparatus for removing the production pipe in the borehole of claim 1 characterized in that one or more centralizers (C) are placed on the outside of the equipment (X), which are in a mechanical contact with the production pipe (10).

3. The apparatus for removing the production pipe in the borehole of claim 1 characterized in that the generator (5) of the plasma-forming media consists of one or several interconnected chambers (18), each chamber (18) having at least one inlet and one outlet, and at least one chamber (18) contains at least one pair of electrodes, the first electrode (16) of the generator being at a negative electrical potential and the second electrode (17) of the generator being at a positive electrical potential.

4. The apparatus for removing the production pipe in the borehole of claim 1 characterized in that the magnet (4) is a permanent magnet or electromagnet.

5. The apparatus for removing the production pipe in the borehole of claim 1 characterized in that the nozzle system (7) is composed of 3-150 channels placed radially towards the production pipe (10) or at an angle of 1-90° from the radial direction.

6. The apparatus for removing the production pipe in the borehole of claim 1 characterized in that the equipment (X) and all its parts are adapted to the effect of pressure in a range of 0.1 -70 MPa.

7. The apparatus for removing the production pipe in the borehole of claims 1 -6

characterized in that an upper dynamic flow restrictor (8) is placed on the outside of the equipment (X), between the equipment and the production pipe (10), at least 10 mm above the level of the nozzle system (7).

8. The apparatus for removing the production pipe in the borehole of claims 1 -7

characterized in that a lower dynamic flow restrictor (9) is placed on the outside of the equipment (X), between the equipment and the production pipe (10), at least 10 mm under the level of the nozzle system (7).

9. The apparatus for removing the production pipe in the borehole of claims 1 -8

characterized in that an electromagnet (M) is placed at the bottom of the equipment (X).

10. The apparatus for removing the production pipe in the borehole of claims 1-9

characterized in that the equipment (X) is placed in the production pipe (10) eccentrically.

11. Method of removing the production pipe in the borehole by means of the equipment (X) of any one of the preceding claims characterized in that the equipment (X) is inserted into the production pipe (10) in the borehole and through the liquid precursor inlet (11) liquid precursor (Y) is supplied, which enters the plasma-forming medium generator (5), which changes in it to the plasma-forming medium (Z), which passes through the nozzle system inlet (6) into the nozzle system (7) and is injected from the nozzle system (7) into the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2) where under the effect of the pressure in a range of 0.1-70 MPa and temperature of the plasma-forming media (Z) in a range of l-l000°C the electric arc (3) is ignited in a liquid environment between the upper electrode (1) and the lower electrode (2), either by contact ignition or voltage ignition, and the electric arc (3) is evenly rotated on a circle by effect of the magnetic field of the magnet (4) and / or interaction of the electric arc (3) with the flow of the plasma-forming media (Z), the axis of the rotational movement of the arc (3) being identical to the axis of symmetry of the upper electrode (1) and the lower electrode (2), and the electric arc (3) input power is in a range of 10-10 000 kW, the material of the production pipe (10) is degraded by the heat flow produced by the j oint action of the rotating electric arc (3) and of the plasma forming media (Z), subsequently the broken material is separated from the production pipe (10) and is removed from the breakdown point, and then the electric arc (3) is extinguished and the equipment (X) is pulled out from the production pipe ( 10) to the outside of the borehole.

12. The method of removing the production pipe in the borehole of claim 11 characterized in that the plasma-forming medium generator (5) changes liquid precursor (Y) to the plasma-forming medium (Z) by thermal decomposition, electrochemical decomposition, chemical decomposition, or a combination of at least two of these decompositions.

13. The method of removing the production pipe in the borehole of claim 11 characterized in that for pressures from 22.06 to 70 MPa and temperatures 374-l000°C, the plasma forming medium (Z) has properties of a mixture of supercritical water and supercritical oxygen.

14. The method of removing the production pipe in the borehole of claim 11 characterized in that for pressures from 5.04 to 22.05 MPa, the plasma-forming medium (Z) has properties of a mixture of water and supercritical oxygen, or a mixture of water vapour and supercritical oxygen.

15. The method of removing the production pipe in the borehole of claim 11 characterized in that for pressures from 0.1 to 5.03 MPa, the plasma-forming medium (Z) has properties of water enriched by oxygen, or a mixture of water vapour and oxygen.

16. The method of removing the production pipe in the borehole of claim 11 characterized in that liquid precursor (Y) is water, a mixture of ethanol and water in any ratio, or a mixture of water and hydrogen peroxide in any ratio, or an aqueous alkali metal hydroxide solution with a concentration of 0.01-5% by weight.

17. The method of removing the production pipe in the borehole of claim 11 characterized in that after ignition the electric arc (3) by deflecting the electrodes (1) and (2) in the axial direction, the arc channel is elongated to the length of 0.1 to 20 mm, whereby the inter-electrode distance between the upper electrode (1) and the lower electrode (2) is maintained at a constant value selected from an interval of 0.1 -20 mm after the electric arc (3) has been stabilized.

18. The method of removing the production pipe of claim 11 characterized in that the particles of broken material of the production pipe (10) are trapped by electromagnet (M) at the bottom of the equipment (X).

19. The method of removing the production pipe of claim 18 characterized in that after the end of the production pipe (10) breakdown process, the electromagnet (M) is switched off and trapped particles of the desintegrated material of the production pipe (10) fall into the bottom of the borehole.

20. The method of removing the production pipe in the borehole of claims 11-19

characterized in that the desintegrated material of the production pipe (10) is removed from the breakdown point by hydrodynamic force generated by the flow of the plasma forming media (Z), coolant (13) a mud, or the gravitational force.

AMENDED CLAIMS

received by the International Bureau on 09 May 2019 (09.05.2019)

CLAIMS

1. Apparatus for disintegrating the production pipe (10) in the borehole mechanically connected by means of BHA to an electrical power supply (12), coolant supply (13), data cable (14) and control unit (15), containing the equipment (X) which is placed inside the production pipe (10) without any contact to the production pipe (10), while the equipment (X) is connected to liquid precursor supply (11) characterized in that the liquid precursor supply (11) enters generator (5) of plasma-forming media connected to the nozzle system inlet (6), which is connected to the nozzle system (7) which is placed in the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2), and the upper electrode (1) and the lower electrode (2) are placed axially with respect to each other around the circumference of the equipment (X) and coaxially placed towards the production pipe (10), while in the axis of the upper electrode (1) and the lower electrode (2) is around the nozzle system inlet (6) placed at least one magnet (4) positioned above the nozzle system (7) and/or under the nozzle system (7).

2. The apparatus for disintegrating the production pipe in the borehole of claim 1

characterized in that one or more centralizers (C) are placed on the outside of the equipment (X), which are in a mechanical contact with the production pipe (10).

3. The apparatus for disintegrating the production pipe in the borehole of claim 1

characterized in that the generator (5) of the plasma-forming media consists of one or several interconnected chambers (18), each chamber (18) having at least one inlet and one outlet, and at least one chamber (18) contains at least one pair of electrodes, the first electrode (16) of the generator being at a negative electrical potential and the second electrode (17) of the generator being at a positive electrical potential.

4. The apparatus for disintegrating the production pipe in the borehole of claim 1

characterized in that the magnet (4) is a permanent magnet or electromagnet.

5. The apparatus for disintegrating the production pipe in the borehole of claim 1

characterized in that the nozzle system (7) is composed of 3-150 channels placed radially towards the production pipe (10) or at an angle of 1-90° from the radial direction.

6. The apparatus for disintegrating the production pipe in the borehole of claim 1

characterized in that the equipment (X) and all its parts are adapted to the effect of pressure in a range of 0.1-70 MPa.

7. The apparatus for disintegrating the production pipe in the borehole of claims 1-6 characterized in that an upper dynamic flow restrictor (8) is placed on the outside of the equipment (X), between the equipment and the production pipe (10), at least 10 mm above the level of the nozzle system (7).

8. The apparatus for disintegrating the production pipe in the borehole of claims 1-7 characterized in that a lower dynamic flow restrictor (9) is placed on the outside of the equipment (X), between the equipment and the production pipe (10), at least 10 mm under the level of the nozzle system (7).

9. The apparatus for disintegrating the production pipe in the borehole of claims 1-8 characterized in that an electromagnet (M) is placed at the bottom of the equipment (X).

10. The apparatus for disintegrating the production pipe in the borehole of claims 1-9

characterized in that the equipment (X) is placed in the production pipe (10) eccentrically.

11. Method for disintegration of the production pipe in the borehole by means of the

apparatus of any one of the preceding claims characterized in that the equipment (X) is inserted into the production pipe (10) in the borehole and through the liquid precursor inlet (11) liquid precursor (Y) is supplied to generator (5) of plasma-forming media, which changes the liquid precursor (Y) to the plasma-forming medium (Z), which passes through the nozzle system inlet (6) into the nozzle system (7) and is injected from the nozzle system (7) into the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2), while between the upper electrode (1) and the lower electrode (2) is a liquid environment with the pressure in a range of 0.1-70 MPa and temperature of the plasma-forming media (Z) in a range of 1-1000°C, and in the space between two cylindrical mechanically movable electrodes is created electric arc (3) with input power in a range of 10-10 000 kW, and the electric arc (3) is ignited either by contact ignition or by voltage ignition, while the electric arc (3) is evenly rotated on a circle by the magnetic field of the magnet (4) and / or by interaction of the electric arc (3) with the flow of the plasma-forming media (Z), the axis of the rotational movement of the arc (3) being identical to the axis of symmetry of the upper electrode (1) and the lower electrode (2), and then the material of the production pipe (10) is degraded by the heat flow produced by the joint action of the rotating electric arc (3) and of the plasma-forming media (Z), subsequently the broken material is separated from the production pipe (10) and is removed from the breakdown point, and then the electric arc (3) is extinguished and the equipment (X) is pulled out from the production pipe (10) to the outside of the borehole.

12. The method for disintegration of the production pipe in the borehole of claim 11

characterized in that the generator (5) of plasma-forming media changes liquid precursor (Y) to the plasma-forming medium (Z) by thermal decomposition, electrochemical decomposition, chemical decomposition, or a combination of at least two of these decompositions.

13. The method for disintegration of the production pipe in the borehole of claim 11

characterized in that for pressures from 22.06 to 70 MPa and temperatures 374- 1000°C, the plasma-forming medium (Z) has properties of a mixture of supercritical water and supercritical oxygen.

14. The method for disintegration of the production pipe in the borehole of claim 11

characterized in that for pressures from 5.04 to 22.05 M Pa, the plasma-forming medium (Z) has properties of a mixture of water and supercritical oxygen, or a mixture of water vapour and supercritical oxygen.

15. The method for disintegration of the production pipe in the borehole of claim 11

characterized in that for pressures from 0.1 to 5.03 MPa, the plasma-forming medium (Z) has properties of water enriched by oxygen, or a mixture of water vapour and oxygen.

16. The method for disintegration of the production pipe in the borehole of claim 11

characterized in that liquid precursor (Y) is water, a mixture of ethanol and water in any ratio, or a mixture of water and hydrogen peroxide in any ratio, or an aqueous alkali metal hydroxide solution with a concentration of 0.01-5% by weight.

17. The method for disintegration of the production pipe in the borehole of claim 11

characterized in that after ignition the electric arc (3) by deflecting the electrodes (1) and (2) in the axial direction, the arc channel is elongated to the length of 0.1 to 20 mm, whereby the inter-electrode distance between the upper electrode (1) and the lower electrode (2) is maintained at a constant value selected from an interval of 0.1-20 mm after the electric arc (3) has been stabilized.

18. The method for disintegration of the production pipe in the borehole of claim 11

characterized in that the particles of broken material of the production pipe (10) are trapped by electromagnet (M) at the bottom of the equipment (X).

19. The method for disintegration of the production pipe in the borehole of claim 18

characterized in that after the end of the production pipe (10) breakdown process, the electromagnet (M) is switched off and trapped particles of the desintegrated material of the production pipe (10) fall into the bottom of the borehole.

20. The method for disintegration of the production pipe in the borehole of claims 11-19 characterized in that the disintegrated material of the production pipe (10) is removed from the breakdown point by hydrodynamic force generated by the flow of the plasma forming media (Z), coolant (13) a mud, or the gravitational force.

Description:
APPARATUS AND METHOD FOR DISINTEGRATING THE PRODUCTION PIPE IN THE BOREHOLE

Field of technology

The invention relates to equipment for removing a production pipe in the borehole and a method for removing the production pipe in the borehole.

State of the art

Thousands of boreholes for the crude oil and natural extraction gas built in the 20 th century are on the brink of their lifetime. Nowadays, due to the lack of profitability of extraction from these boreholes, their temporary closure or even complete shutdown is considered. It is estimated that approximately 30,000 boreholes around the world will have to be closed over the next fifteen years. “Decommissioning” is a term used to disable the installation / platform (which is the construction from which extraction is being carried out) from operation, which requires safe sealing of the hole on the earth’s surface and the disposal of equipment used for offshore oil extraction. Decommissioning is a rapidly evolving market sector in the petroleum industry, which has great potential for development but also carries great risks. The decommissioning process needs to be well understood if it needs to be managed with efficient spending of funds.

The most expensive decommissioning operation is Plug & Abandonment.

Plug & Abandonment (hereinafter only P & A) is the closure and permanent insulation of the borehole. There are legislative and regulatory requirements associated with the P & A process, with the aim to ensure sufficient isolation and of the entire borehole against leakage of fluids as well as for the protection of drinking water sources against hydrocarbon contamination. In most cases of P & A, a series of cement plugs / seals is placed in the borehole, with a test to confirm the isolation function of these cement plugs at each level.

P & A consists of several steps: removing the production pipe from the borehole, from filling / sealing of the borehole, and finally removing the infrastructure above the earth’s surface, or on the bottom of the sea.

The task of P & A is to create a barrier to prevent leakage of hydrocarbons to the earth's surface. The height of such a barrier is given by local legislation, for example, in the British North Sea, at least 100 feet (approx. 30 meters) of the continuous layer of concrete impeding the axial and radial flow of hydrocarbons is stated as usual requirement in practice. Hydrocarbons could escape to the earth's surface along the original sheeting, respectively concrete. Therefore, it is necessary to precisely carry out the shutdown of the borehole. The borehole closure consists, using conventional mechanical methods, of the following steps:

- Preparatory work and installation of the necessary infrastructure,

- Removing the“production tree” and installation of a“blowout preventer” (BOP),

- Cutting and removing the production pipe,

- Milling of certain section of the steel sheeting of the borehole,

- Milling of concrete that separates the sheeting and rock massif,

- Inserting the plug into the given section of the borehole,

- And finally, the injection of new concrete closing the given section of the borehole.

Blowout preventer (hereinafter only BOP) is a large valve at the top of the borehole which closes if the operators of the borehole lose control over the borehole pressure. By closing this valve (usually

l controlled remotely by hydraulic drives), drilling operators gain control over the borehole, and then procedures for increasing the density of the mud can be applied, until it is possible to open the BOP and maintain control over the borehole pressure.

BOP is of critical importance for the safety of the operators of the drilling rig, drilling accessories and the borehole itself.

In practice, the term "production tree" is used, which is the name for a set of valves, spools and fittings connected with the top part of the borehole to operate and control the flow of fluids originating in the borehole. Production tree is used only during production, not used during drilling.

The most time-consuming step in the decommissioning process are initiating operations, i.e. installing the necessary infrastructure, removing the production tree and installing the BOP, removing the production pipe and milling the sheeting. These operations bring the most potential complications.

Steel sheeting and concrete don’t need to be milled in the case if the concrete which separates sheeting and rock massif is of sufficient quality. This quality is mainly determined by conventional ultrasonic methods known as“cement bond log”. A“cement bond log” (hereinafter only CBL) is the term used for a system in which acoustic logs provide a means of assessing the mechanical integrity and quality of the cement bond. Acoustic logs measure the quality of the cement directly, whereby this value derives from the degree of acoustic bond of cement to sheeting and rock. Correctly made and interpreted cement bond logs (CBL) provide highly reliable estimates of the borehole integrity and isolation of the individual zones.

Since these methods cannot analyze cement through two layers of steel material, in conventional methods it is necessary to cut off the production pipe and remove it from the borehole. This operation usually takes a few days and requires the presence of a conventional drilling rig with sufficient capacity to pull out the production pipe (which may be several kilometres long).

A different technical problem is solved by the borehole closure procedure which is called Perforate & Wash & Cement (PWC), in which it does not come to removing the production pipe from the borehole but only to its perforation. The formed holes cannot be used to verify the cement quality by CBL method, which is a considerable disadvantage. The PWC method is also subsequently associated with other disadvantages, such as uneven cement distribution during the cementation process and thus insufficient isolation, which can lead even to leakage of hydrocarbons.

P & A costs are costs without turnover generation. Naturally, mining companies around the world are looking for effective solutions to help reduce these massive expenses.

Research and development in the mining segment focused primarily on progressive materials and methods in the field of drilling and assembly of the borehole, while the development of innovative technologies in the P & A field has long been neglected.

Up to now, particularly conventional mechanical technologies have been used in the P & A field.

A conventional method based on the use of a hydraulically operated tool - milling cutter, is currently being developed by the company Deltide Energy Services, LLC in the document WO2016085899 Al. It is a mechanical milling tool (called Medusa), which, in addition to the standard axial movement, is able to change its position even in the radial direction, thus achieving removing material also from misaligned production pipes.

Similarly, in the document AU2014280087 of the company Welltec A/S a tool is described that can adapt the position of blades to production pipe geometry, i.e. radially press the blades and anchoring arms which ensure stabilisation. The disadvantages of conventional mechanical methods are in particular:

1) The need for a heavy rotary drilling rig to pull out the production pipe, while renting the rig is costly,

2) Damage and locking of the tool may occur, or seizing some of its part in the borehole during cutting of the production pipe,

3) Demanding and costly processing and recycling of the production pipeline, which, moreover, often shows low levels of radioactivity caused by long-term placement in the borehole.

In order to eliminate the disadvantages of conventional mechanical methods, conventional methods are increasingly combined with unconventional ones, such as in the patent application W02016170048 of the company Welltec A/S. The invention uses conventional mechanical milling technology enhanced by the addition of a corrosive additive which weakens and etches off the wall of the production pipe in the borehole. The milling blades then remove the thinned wall, i.e. the milling cutter takes less material from the production pipe.

Also, the company Spex Engineering Ltd. deals with the development of an alternative method based on a controlled explosion. In the documents GB2532609A, GB2533844A and US20l6290082Al, the idea of using a detonation mechanism to remove borehole materials is developed. The use of carrier materials allows the generation of thermal energy and the expansion of gases directed to a concrete place of degradation of the material. The type of explosive material used in the equipment determines the interaction zone and at the same time the amount and placement of the required segments.

The document GB2532609A discloses in more detail fuels into rocket motors as carrier / explosive material that provide detonation and the necessary heat and kinetic energy to remove materials. The presence of oxygen improves the detonation mechanism. The main used mechanism is the combustion process and the subsequent detonation.

The company Interwell Technology AS deals with an alternative based on exothermic chemical reactions, e.g. explosion, e.g. in the document WO2013135583A2. The mechanism of removing the production pipe is the melting of the material using the heat-generating mixture of thermite. The process runs spontaneously, it cannot be controlled after initialization. The borehole is permanently closed by solidification of the melt.

The technology of exothermic chemical reactions is also used in the“Radial Cutting Torch” technology. A typical example of this technology is the patent US6598679 B2. It describes a technology that perforates the production pipe around the circumference and divides it into two parts.

The technology is based on combustible / fuel pellets that are built into the cylindrical body of the cutter. After an electrical ignition of combustible / fuel, the hot liquid environment expands, and a high-speed and high-temperature flow is generated through the outflow nozzles placed in one plane around the circumference.

The aforementioned technology is used for cutting, and it is a process that is only performed once (as the amount of explosive in the cutter body is limited). It is not a continuous process.

Another alternative direction to the conventional method of mechanical milling is the use of a laser described e.g. in the patent AU2015203686 of the company Halliburton Energy Services Inc. The laser beam that is fed into the space can be directed to the selected position and positioned in the immediate vicinity. In the set position, the laser beam gradually cuts the production pipe material and sheeting up to the rock material.

Disadvantages of alternative technologies:

Technologies Problem

The size or unsuitable shape of splinters complicates the "milling" process”, most often with conventional mechanical technologies, but larger splinters can also occur with some combined alternative technologies (e.g. explosive cutting of the company Spex).

The most promising alternative direction to the conventional method of mechanical milling is a technology based on the use of plasma.

The technology of plasma cutting of metallic materials under atmospheric conditions is made by the so-called plasma cutter.

With this cutting method, the plasma flow is concentrated to a small cross-section (at the level of mm 2 units). This the most striking shortcoming of such equipment, since it is a point effect rather than a planar one.

Plasma cutters use a flow of gaseous media for their activity, thus being dependent on the physicochemical properties of this medium.

For high-pressure gaseous medium, based on the present knowledge, it is not technically possible to ensure sufficient energy flow density for the plasma cutter. The reason is voltage limitations of the sources, the design electrical isolation limits and constraints given for the purpose of use in the borehole environment.

Moreover, in the case of supercritical phase transformation of the medium, associated with the increase in ambient pressure, these properties change abruptly, making it impossible to use the plasma cutting principle for this environment.

The basis of milling technology with using plasma is described in the document WO2014137299 Al of the company GA Drilling, a.s., where the use of plasma for thermal removal of conductive and non-conductive materials, preferably in the axial direction, is generally described. The equipment uses helically rotating electric arc drawn from the central electrode to the surface of the outer electrode. The described solution requires the creation of a relatively long electric arc with sufficient thermal action at atmospheric pressure realizable at atmospheric pressure.

However, the existence of a helically rotating electric arc with a given geometry of the equipment at pressures higher than atmospheric, as well as the actual realization of the material removal process using current technology and knowledge is very problematic, or questionable, since in higher pressures at the source with the same parameters, the maximum sustainable length of the electric arc significantly decreases, what is also related to the reach of the process.

The optimization of the metal removing technology is described in the patent application WO2016105279 of the company GA Drilling, a.s., where the material removal efficiency is increased by elongation of the arc (thus increasing electrical and thus thermal power) by the principle of the arched connection, i.e. the localization of the heat output, where the arc bums between the electrode and the metal pipeline removed. Such a mode, however, requires a high- quality electrical connection of the source pole with the metal pipeline removed.

The disadvantage of such a solution is also the considerably higher voltage requirements to maintain the bonded (long) arc in the liquid environment at increased pressures which limit its usability in the borehole environment.

Summary of the invention

The requirement of the drilling industry is currently a technology that would eliminate the shortcomings of the present technical solutions in the field of the production pipe removing, i.e. a technology that does not require a production pipe to be taken out from the borehole, and for its operation a simple, easy and thus cheap drilling kit can be used.

Modern drilling technology involves the use of“coiled tubing” instead of conventional rotating drill pipes. The advantage is that the coiled tubing offers simpler processes of commissioning

and pulling out from the borehole compared to the drill pipes which must be connected and later dismantled during the process of commissioning and pulling out.

Another advantage is that the coiled tubing enters the borehole through a“stripper”, mounted under the“injector head”. Stripper is equipment which ensures the primarily operational sealing between pressurized fluids in the borehole and the surface environment, and thus provides dynamic sealing around the“coiled tubing” during operation. By this, it offers borehole control capabilities beyond those that are possible with conventional drilling pipeline, and thus allows also drilling so-called “underbalanced boreholes“, where the pressure is less than optimal.

The injector head provides a driving force for inserting and removing coiled tubing from the borehole. An important advantage of coiled tubing is the significantly lower cost of purchasing or renting in comparison with a conventional rotary drilling rig.

The solution of the present invention eliminates the shortcomings of the solutions known up to now. For the needs of describing the invention and the unambiguous definition of the equipment orientation in the production pipe we state, that the equipment is connected to an electrical power supply, a coolant supply, a liquid precursor supply, data cable and control unit, which are connected to the equipment on the top side of the equipment (i.e. from the side of the borehole surface).

The invention relates to equipment for removing a production pipe in the borehole and a method for removing the production pipe in the borehole.

The equipment can also be classified as a milling head that is part of the“Bottom Hole Assembly” (hereinafter only BHA). BHA is that part of the drilling rig that runs into the borehole and allows adjusting the necessary inputs for the milling head directly above the milling point.

The invention addresses the removal of the production pipe by means of an electric arc nozzle rotating in a liquid environment in the presence of a plasma-forming medium, preferably a mixture of supercritical water and supercritical oxygen. Removing the production pipe is made without direct contact of the equipment with the pipeline, which results in elimination of undesirable degradation of the material of the milling tools and elimination of the necessity to exchange the milling tools during the process of removing the production pipe.

The equipment can make a hole in the production pipeline, through which CBL measurement can be made.

The advantage of such a solution is that it is not necessary to take out a multi-kilometre production pipe, and in addition to saving costs, also elimination of health risks due to the contact of the operators with the production pipe is not negligible.

The equipment for removing the production pipe in the borehole is placed in a contactless manner inside the production pipe and comprises a liquid presursor supply which enters the plasma-forming medium generator, and the plasma-forming medium generator is connected to the nozzle system inlet connected to the nozzle system, while the nozzle system is placed in the space between two cylindrical mechanically movable electrodes, an upper electrode and a lower electrode. The upper electrode and the lower electrode are placed axially with respect to each other around the circumference of the equipment and are coaxially placed towards the production pipe. Both electrodes are connected to a standard motion mechanism that allows independent movement of electrodes. In the axis of electrodes, around the nozzle system inlet there is at least one magnet placed. The magnet may be placed below the nozzle system, above the nozzle system, or simultaneously under as well as above the nozzle system. The magnet is a permanent magnet or electromagnet.

The equipment is inserted into the production pipe in the borehole, whereby its diameter is in the cross-section adjusted to the cross-section of the production pipe so that there is free space between the equipment and the production pipe and the equipment does not touch the production pipe. Thus, the equipment is placed in the production pipe in a contactless manner, but in the case of a large length of the equipment, one or more centralizers are placed on the equipment, which are in a mechanical contact with the production pipe.

The equipment is mechanically connected with the remaining part of the BHA and is in a standard manner connected by means of interconnection units with the electrical power supply, coolant supply, liquid precursor supply, data cable and control unit.

The plasma-forming medium generator consists of at least one chamber, or several interconnected chambers, each chamber having at least one inlet and one outlet. In the case of multiple chambers, these are arranged in series, in parallel or in a combination of these methods. There are three possibilities of content of chamber, namely:

- A catalyst

- Or at least one pair of electrodes, the first electrode being at a negative electrical potential and the second electrode being at a positive electrical potential

- Or the resistance wire or the chamber is surrounded by the resistance wire.

A preferred solution is, if at least one generator chamber contains at least one pair of electrodes, the first electrode being at a negative electrical potential and the second electrode being at a positive electrical potential.

The nozzle system is composed of 3 to 150 channels placed radially towards the production pipe or at an angle of 1 -90 ° from the radial direction. An upper dynamic flow restrictor may be placed on the outside of the equipment, between the equipment and the production pipe, at least 10 mm above the level of the nozzle system and / or a lower dynamic flow restrictor may be placed on the outside of the equipment, between the equipment and the production pipe, at least 10 mm under the level of the nozzle system.

The use of restrictors in the equipment is not necessary, but has the following benefits for the breakdown process:

Upper dynamic flow restrictor

- Prevents leakage of superheated plasma-forming medium which desirably preheats the production tube to a higher initiation temperature,

- Prevents flushing of chips into the space between the equipment and the production pipe,

- Prevents the penetration of the surrounding drilling fluid (water, brine, mud...) into the process,

- By maintaining the plasma-forming medium with the lower density in the process area, the radial reach of the process increases.

Lower dynamic flow restrictor

- Prevents leakage of superheated plasma-forming medium which desirably preheats the production tube to a higher initiation temperature,

- Prevents the penetration of the surrounding drilling fluid (water, brine, mud...) into the process,

- By maintaining the plasma-forming medium with the lower density in the process area, the radial reach of the process increases,

- Directs the flow of the superheated plasma-forming medium towards the production pipe.

An electromagnet (M) may be placed at the bottom of the equipment, the purpose of which is to collect the chips formed during the production pipe removing process.

The equipment operates in a wide range of pressures of 0.1 MPa-70 MPa. An advantage is the continuous operation of the equipment without the need for exchange / modification of the components at different depths of the borehole.

The process of removing the production pipe in the borehole with the action of the equipment described above begins by inserting the equipment into the production pipe without contact with the production pipe.

Subsequently, a liquid precursor is introduced into the equipment via the liquid presursor supply. The liquid precursor is a mixture of ethanol and water in any ratio, or a mixture of hydrogen peroxide and water in any ratio, water or an aqueous alkali metal hydroxide solution with a concentration of 0.01-5% by weight.

The plasma-forming medium generator modifies the incoming liquid precursor to plasma-forming medium by thermal, electrochemical or chemical decomposition, or a combination of at least two of these decompositions - depending on the type of equipment, and additional energy may be released.

The plasma-forming medium has the following properties:

- For pressures from 0.1 to 5.03 MPa: waters enriched with oxygen, or mixtures of water vapour and oxygen,

- For pressures from 5.04 to 22.05 MPa: mixtures of water and supercritical oxygen, or mixtures of water vapour and supercritical oxygen,

- For higher pressures from 22.06 to 70 MPa (with temperature 374-l000°C): mixtures of supercritical water and supercritical oxygen (SCW+SCO).

After its formation, the plasma-forming medium passes through the nozzle system inlet into the nozzle system and is injected from the nozzle system into the inter-electrode space under the effect of the ambient pressure in a range of 0.1-70 MPa. The temperature of the plasma-forming medium is in the range of 1-1000 °C.

The used plasma-forming medium has the following advantages for the process:

- Expansion in the transformation of the liquid precursor to the plasma-forming medium - increasing the range of the process effect,

- Creates better conditions for arc initiation and stability (low-energy process),

- Higher degree of oxidation of the removed material.

The main role of the plasma-forming medium is to ensure suitable conditions for the creation and existence of plasma for plasma removal of materials / milling. Increased oxygen concentration in the plasma-forming medium favours the degradation process, and additional thermal energy is released. A part of the released additional energy is consumed to increase the thermodynamic temperature of the plasma-forming medium passing through the electric arc, where the temperature of the medium incident to the surface of the production pipe material is further increased; the remaining part of the energy is consumed by the volume expansion of the decomposed medium. Higher thermodynamic temperature accelerates the process of oxidation and overall degradation of the production pipe material. The expansion increases the distance in the radial direction, to which the equipment is capable of disintegrating the production pipe material, and at the same time the efficiency of removing the broken production pipe material increases by expansion.

The plasma-forming medium has 3 decisive properties with respect to electric parameters and the electric arc stability:

- Low permissivity - the lower permissivity, the lower arc voltage requirements,

- Low density - the lower density, the lower arc voltage requirements; at lower density it is easier to move the medium and this exhibits smaller voltage and shape fluctuations,

- Above the critical point of water, the presence of the arc does not trigger further phase change, and therefore it is more energy efficient to maintain the electric arc.

Prior to starting the P & A process, in many cases, a borehole is fdled with a fluid such as brine or seawater in which residual hydrocarbons or residues of fluid used in drilling (on an aqueous or oil basis) may be present.

The process continues by the subsequent ignition of the electric arc in the fluid at high borehole pressure (up to 70 MPa) between the upper electrode and the lower electrode which are placed coaxially with the production pipe. The arc is ignited either by contact ignition or voltage ignition.

Contact ignition is accomplished by approaching, touching both electrodes and then separating them to the required distance (FIG. 1).

For voltage ignition, the advantage of mechanically movable electrodes is also fully used, and a fixed voltage value in the 0.1 kV-l MV range, which is not pulse-like, is used to carry out the electrical breakthrough. Electric arc ignition takes place at a constant electric voltage, the inter electrode distance begins to change and the electrical breakthrough takes place after reaching the minimum distance required to form a conductive channel between both electrodes. In this case, the electrodes will not touch. After ignition the electric arc, the electrodes move away to the required distance.

The main purpose of using this method of initiating the electric arc is to ensure reliability and higher efficiency of the electric arc ignition process in a wide range of pressures and in a fluid environment.

After ignition the electric arc, elongation of the arc channel to the length from 0.1 to 20 mm occurs by deflecting the electrodes in the axial direction. The electric arc is then maintained by a constant electric current.

The inter-electrode distance is kept approximately constant throughout the entire milling time at a selected value in the range from 0.1 to 20 mm.

The electric arc burns exclusively between a pair of electrodes of the same shape and the length of the electric arc is adapted to the electrical source parameters. The arc length detection is performed by continuous monitoring the required average voltage required to maintain the electric arc. The electric arc input power is 10-10000 kW.

With the stated mode of maintaining the electric arc - unlike in older solutions - the electrode wear is more uniform, thereby simplifying the control of the electrode movement.

The electric arc burns between two cylindrical electrodes in a liquid environment at an ambient pressure in the range from 0.1 to 70 MPa and is evenly rotated by a Lorentz force on a circle, the axis of the rotational movement of the arc being identical to the axis of symmetry of the electrodes, thus eliminating the need to rotate the components of the equipment. In this case, the term rotated on a circle means the movement of the two roots of the electric arc on a circle.

The rotation of the electric arc is ensured by the magnetic field of a permanent magnet or electromagnet and / or by the interaction of the electric arc with the flow of the plasma-forming medium.

Since the actual breakdown process does not require a mechanical contact of the broken material and equipment, mechanical wear of the functional parts of the equipment does not occur and the efficiency of the equipment does not decrease over time. Additionally, the process also operates at a pressure range from 0.1 to 70 MPa, and therefore it is not necessary to exchange the equipment during the milling process at various depths. The necessary wear of the electrodes, which occurs during the process, is compensated by an increase in the volume of the wear part, by the material composition itself and by the electrode construction, as well as by the mutual axial movement of the electrodes. This ensures that it is not necessary to change the milling tool or its parts during the entire time of the production pipe removing due to wear or different pressures of the surrounding environment.

The production pipe material is degraded by the heat flow produced by the joint action of the rotating electric arc and the plasma-forming medium, whereby the created heat flow has the character of a flat action.

The process of the production pipe breakdown involves several simultaneously acting mechanisms. The triggering element of each mechanism is an elevated temperature.

The temperature triggers the first mechanism, which is the melting process, which directly results in the mechanical separation of degraded material in the form of melt from the production pipe.

The second mechanism of degradation is high-temperature oxidation, a direct exothermic reaction of solid or melted material of the production pipe with oxygen, or another oxidizing agent supplied in the plasma-forming medium.

Additional energy is supplied to the breakdown process by the plasma-forming medium flow from nozzles towards the wall of the production pipe, through inter-electrode space, where the medium passes through the electric arc. The radial flow component contributes to the efficient transfer of heat output to the disintegrated material of the production pipe.

Subsequently, the broken material of the production pipe is separated from the production pipe and removed from the breakdown point. The material is broken mainly to particles of a size 0.01-5 mm.

The degree of roughness of the remaining material of the production pipe after milling does not exceed the size of the created particles.

The broken material of the production pipe is removed from the breakdown point by hydrodynamic force generated by the flow of the plasma-forming medium, coolant and mud acting on the broken particles or the gravitational force.

Particles of broken material - chips:

1) Are flushed by mud to the surface, or

2) Are guided by the flow of media to the bottom of the borehole, or other closure of the borehole, or

3) Are trapped by electromagnet in the bottom part of the equipment, since the originated chips are magnetic. This provides for more intensive removing chips from the breakdown point of the production pipe, while at the same time ensuring the reduction of the chip trapping on the magnet responsible for the rotation of the electric arc, thereby prolonging its lifetime. After termination of the equipment action, the electromagnet can be switched off and trapped chips fall into the bottom of the borehole.

The use of a particular type of chip removal depends on the requirements of the borehole operator.

After the desired section of the production pipe is milled, the process of removing the production pipe in the borehole is terminated by extinguishing the arc. The equipment is subsequently pulled out of the borehole.

The equipment may be placed in the production pipe centrically as well as eccentrically, to remove the unsymmetrical part of the production pipeline.

Description of figures on drawings

FIG.l presents the process of contact ignition.

FIG.2 presents equipment for removing the production pipe with two magnets, with upper and lower dynamic flow restrictor and electromagnet for the chip trapping. It is positioned centrically in the production pipe in a lateral cross-section, and in a cross-section from above.

FIG.3 presents equipment for removing the production pipe with one magnet, without dynamic flow restrictors and without electromagnet for the chip trapping. It is positioned centrically in the production pipe in a lateral cross-section.

FIG.4 presents equipment for removing the production pipe with two magnets, without dynamic flow restrictors and without electromagnet for the chip trapping. It is positioned eccentrically in the production pipe, in a lateral cross-section and in a cross-section from above.

FIG.5 presents equipment for removing the production pipe with one magnet, with upper dynamic flow restrictor and with electromagnet for the chip trapping. It is positioned centrically in the production pipe in a lateral cross-section. FIG.6 presents equipment for removing the production pipe with one magnet, with lower dynamic flow restrictor and without electromagnet for the chip trapping. It is positioned centrically in the production pipe in a lateral cross-section.

Examples of embodiments

The equipment X for removing the production pipe JJ) in the borehole is mechanically connected by means of BHA to an electrical power supply 12, coolant supply 13, data cable 14 and control unit 15. The equipment X is placed in a contactless manner inside the production pipe JJ) and comprises a liquid presursor supply JT which enters the plasma-forming medium generator 5 connected to the nozzle system inlet 6 connected to the nozzle system 7, while the nozzle system 7 is placed in the space between two cylindrical mechanically movable electrodes, an upper electrode J_ and a lower electrode 2, and the upper electrode J_ and the lower electrode 2 are placed axially with respect to each other around the circumference of the equipment X and coaxially placed towards the production pipe j_0, while in the axis of the upper electrode J_ and the lower electrode 2 there is around the nozzle system inlet 6 at least one magnet 4 placed above the nozzle system 7 and / or under the nozzle system 7. The magnet 4 is a permanent magnet or electromagnet. Plasma-forming medium generator 5 consists of one chamber J_8, or several interconnected chambers J_8, each chamber J_8 having at least one inlet and one outlet. In the case of multiple chambers J_8, these are arranged in series, in parallel or in a combination of these methods. There are three possibilities of content of chamber J_8, namely:

- A catalyst

- Or at least one pair of electrodes, the first electrode J_6 of the generator being at a negative electrical potential and the second electrode 3/7 of the generator being at a positive electrical potential

- Or the resistance wire or the chamber J_8 is surrounded by the resistance wire.

A preferred solution is, if at least one generator chamber J_8 contains at least one pair of electrodes, the first electrode 16 being at a negative electrical potential and the second electrode 3/7 being at a positive electrical potential.

The nozzle system 7 is composed of 3 to 150 channels placed radially towards the production pipe 10 or at an angle of 1-90 ° from the radial direction.

The equipment is in the production pipe JJ) placed without contact with the production pipe, but in the case of a longer equipment, one or more centralizers C are placed on the outside of the equipment X, which are in mechanical contact with the production pipe JJ).

An electromagnet M may be placed at the bottom of the equipment X.

The equipment X is placed in the production pipe JJ) centrically, or eccentrically.

Between the equipment X and the production pipe JJ), restrictors can be placed, namely upper dynamic flow restrictor 8 and /or lower dynamic flow restrictor 9.

The equipment X and all its parts are adapted to operate at a pressure in the range from 0.1 to 70 MPa.

The method of removing the production pipe in the borehole by means of the equipment X is carried out in such a way that the equipment X is inserted into the production pipe JJ) in the borehole, and into the equipment X through the liquid precursor inlet JT liquid precursor Y is supplied which enters the plasma-forming medium generator 5 and changes in it to the plasma- forming medium Z, which passes through the nozzle system inlet 6 into the nozzle system 7 and is injected from the nozzle system 7 into the space between the upper electrode and the lower electrode 2 where under the effect of the pressure in a range of 0.1-70 MPa and temperature of the plasma-forming medium Z in a range of l-l000°C the electric arc 3 is ignited, either by contact ignition or voltage ignition, in a liquid environment between the upper electrode 1 and the lower electrode 2. The electric arc 3 is evenly rotated on a circle, the axis of the rotational movement of the arc 3 being identical to the axis of symmetry of the upper electrode 1 and the lower electrode 2, and the rotation of the electric arc 3 is ensured by the magnetic field of a magnet 4 and / or by the interaction of the electric arc 3 with the flow of the plasma-forming medium Z. The electric arc 3 input power is in a range of 10-10000 kW. The production pipe material 1_0 is degraded by the heat flow produced by the joint action of the rotating electric arc 3 and the plasma-forming medium Z, subsequently the broken material is separated from the production pipe JJ) and is removed from the breakdown point, and then the electric arc 3 is extinguished and the equipment X is pulled out from the production pipe JJ) to the outside of the borehole.

The plasma-forming medium generator 5 modifies the liquid precursor Y to the plasma-forming medium Z by thermal, electrochemical or chemical decomposition, or a combination of at least two of these decompositions.

For pressures from 22.06 to 70 MPa and temperatures from 374 to l000°C, the plasma-forming medium Z has the properties of a mixture of supercritical water and supercritical oxygen, for pressures from 5.04 to 22.05 MPa, the plasma-forming medium Z has the properties of a mixture of water and supercritical oxygen, or a mixture of water vapour and supercritical oxygen, and for pressures from 0.1 to 5.03 MPa, the plasma-forming medium Z has the properties of a mixture of water and oxygen (oxidizing agent), or a mixture of water vapour and oxygen.

The liquid precursor Y is water, a mixture of ethanol and water in any ratio, a mixture of hydrogen peroxide and water in any ratio, or an aqueous alkali metal hydroxide solution with a concentration of 0.01-5% by weight.

After ignition the electric arc 3 by deflecting the electrodes, of the upper electrode 1 and the lower electrode 7 elongation of the arc channel to the length of 0.1 to 20 mm in the axial direction occurs. Inter-electrode distance between the upper electrode 1 and the lower electrode 2 is maintained at a constant value selected from an interval of 0.1-20 mm after the electric arc 3 has been stabilized.

The particles of broken material of the production pipe JJ) may be trapped by electromagnet M placed at the bottom of the equipment X.

The broken material of the production pipe JJ) is removed from the breakdown point by hydrodynamic force generated by the flow of the plasma-forming medium Z, coolant 3 and mud acting on the broken particles or the gravitational force.

Example 1

The equipment X has two magnets 4, and both magnets are permanent magnets.

An upper dynamic flow restrictor 8 is placed on the outside of the equipment X, between the equipment and the production pipe 10, 10 mm above the level of the nozzle system 7.

The nozzle system 7 is composed of 36 channels placed at an angle of 26° from the radial direction towards the production pipe.

At the bottom of the equipment X, an electromagnet M is placed.

The equipment X is placed in the production pipe JJ) centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with a concentration of 69% by weight.

It enters the plasma-forming medium generator 5 and changes in it by electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical mechanically movable electrodes, the upper electrode J_ and the lower electrode 2 under the effect of the ambient pressure of 30 MPa. Plasma-forming medium Z has a temperature of 400°C and the properties of a mixture of supercritical water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode J_ and the lower electrode 2 is maintained at a constant value of 3 mm after the electric arc 3 has been stabilized.

The broken material of the production pipe JJ) is removed from the breakdown point by hydrodynamic force generated by the flow of the plasma-forming medium Z acting on the broken particles. Subsequently, the particles of broken material (chips) are trapped by electromagnet M at the bottom of the equipment X.

After the end of the process, the electric arc 3 is extinguished, electromagnet M is switched off and trapped chips fall into the bottom of the borehole. Subsequently, the equipment is pulled out from the production pipe JJ) to the outside of the borehole.

Example 2

The equipment X in FIG. 2 has two magnets J_, and both are permanent magnets.

An upper dynamic flow restrictor 8 is placed on the outside of the equipment X, between the equipment and the production pipe j_0, at least 10 mm above the level of the nozzle system 7.

A lower dynamic flow restrictor 9 is placed on the outside of the equipment X, between the equipment and the production pipe JJ^ at least 10 mm under the level of the nozzle system 7.

One centralizer C is placed on the outside of the equipment X, between the equipment and the production pipe 1_0, which is in a mechanical contact with the production pipe 10.

The nozzle system 7 is composed of 24 channels placed radially towards the production pipe.

At the bottom of the equipment X, an electromagnet M is placed. The equipment X is placed in the production pipe 1_0 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with a concentration of 35% by weight.

It enters the plasma-forming medium generator 5 and changes in it by electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode J_ and the lower electrode 2 under the effect of the ambient pressure of 19 MPa. Plasma- forming medium Z has a temperature of 200°C and the properties of a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode J_ and the lower electrode 2 is maintained at a constant value of 10 mm after the electric arc 3 has been stabilized.

The broken material of the production pipe JJ) is removed from the breakdown point by hydrodynamic force generated by the flow of the plasma-forming medium Z acting on the broken particles. Subsequently, the particles of broken material (chips) are trapped by electromagnet M at the bottom of the equipment X.

After the end of the process, the electric arc 3 is extinguished, electromagnet M is switched off and trapped chips fall into the bottom of the borehole. Subsequently, the equipment is pulled out from the production pipe JJ) to the outside of the borehole.

Example 3

The equipment X is long, and therefore it has two centralizers C placed on the outside of the equipment X between the equipment a production pipe j_0, which are in a mechanical contact with the production pipe JJ).

The equipment X has two magnets 4, and both are permanent magnets.

A lower dynamic flow restrictor 9 is placed on the outside of the equipment X, between the equipment and the production pipe JJ), 10 mm under the level of the nozzle system 7.

The nozzle system 7 is composed of 8 channels placed at an angle of 60° from the radial direction towards the production pipe. The equipment X is placed in the production pipe JJ) centrically.

The liquid precursor Y is aqueous ethanol solution with a concentration of 96% by weight.

It enters the plasma-forming medium generator 5 and changes in it by electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode J_ and the lower electrode 2 under the effect of the ambient pressure of 15 MPa. Plasma-forming medium Z has a temperature of 30°C and the properties of a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by contact ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode J_ and the lower electrode 2 is maintained at a constant value of 7.5 mm after the electric arc 3 has been stabilized.

Example 4

The equipment X in FIG.4 has two magnets 4, and both are electromagnets.

The nozzle system 7 is composed of 120 channels placed at an angle of 5° from the radial direction towards the production pipe.

The equipment X is placed in the production pipe JJ) eccentrically. The liquid precursor Y is aqueous potassium hydroxide solution with a concentration of 3% by weight.

It enters the plasma-forming medium generator 5 and changes in it by electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode l and the lower electrode 2 under the effect of the ambient pressure of 70 MPa. Plasma- forming medium Z has a temperature of l00°C and the properties of a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode \ and the lower electrode 2 is maintained at a constant value of 0.8 mm after the electric arc 3 has been stabilized.

Example 5

The equipment X in FIG. 3 has one magnet 4, which is permanent. Magnet 4 is placed around the nozzle system inlet 6 above the nozzle system 7.

The nozzle system 7 is composed of 3 channels placed radially towards the production pipe.

The equipment X is placed in the production pipe J_0 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with a concentration of 80% by weight.

It enters the plasma-forming medium generator 5 and changes in it by chemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode l and the lower electrode 2 under the effect of the ambient pressure of 50 MPa. Plasma-forming medium Z has a temperature of 500°C and the properties of a mixture of supercritical water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode l and the lower electrode 2 is maintained at a constant value of 1 mm after the electric arc 3 has been stabilized.

Example 6

The equipment X in FIG. 5 has one magnet 4, which is permanent. Magnet 4 is placed

under the nozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of the equipment X, between the equipment and the production pipe 10, 10 mm above the level of the nozzle system 7.

The nozzle system 7 is composed of 90 channels placed at an angle of 45° from the radial direction towards the production pipe J_0. At the bottom of the equipment X, an electromagnet M is placed. The equipment X is placed in the production pipe JJ) centrically.

The liquid precursor Y is aqueous sodium hydroxide solution with a concentration of 0.01 % by weight. It enters the plasma-forming medium generator 5 and changes in it by electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode l and the lower electrode 2 under the effect of the ambient pressure of 0.1 MPa. Plasma-forming medium Z has a temperature of l°C and the properties of a mixture of water and oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode \ and the lower electrode 2 is maintained at a constant value of 4 mm after the electric arc 3 has been stabilized.

The broken material of the production pipe J_0 is removed from the breakdown point by hydrodynamic force generated by the flow of the plasma-forming medium Z acting on the broken particles. Subsequently, the particles of broken material (chips) are trapped by electromagnet M at the bottom of the equipment X.

After the end of the process, the electric arc 3 is extinguished. Subsequently, the electromagnet M is switched off and trapped chips fall into the bottom of the borehole. Subsequently, the equipment is pulled out from the production pipe J_0 to the outside of the borehole.

Example 7

The equipment X has one magnet 4, which is electromagnet and is placed around the nozzle system inlet 6 above the nozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of the equipment X, between the equipment and the production pipe j_0, at least 10 mm above the level of the nozzle system 7.

A lower dynamic flow restrictor 9 is placed on the outside of the equipment X, between the equipment and the production pipe H), at least 10 mm under the level of the nozzle system 7.

The nozzle system 7 is composed of 48 channels placed at an angle of 80° from the radial direction towards the production pipe. The equipment X is placed in the production pipe J_0 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with a concentration of 1% by weight.

It enters the plasma-forming medium generator 5 and changes in it by thermal decomposition and electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode l and the lower electrode 2 under the effect of the ambient pressure of 3 MPa. Plasma-forming medium Z has a temperature of 270°C and the properties of a mixture of water vapour and oxygen.

The electric arc 3 is ignited by contact ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode l and the lower electrode 2 is maintained at a constant value of 20 mm after the electric arc 3 has been stabilized.

Example 8 The equipment X has one magnet 4, which is electromagnet and is placed around the nozzle system inlet 6 above the nozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of the equipment X, between the equipment and the production pipe 10, 10 mm above the level of the nozzle system 7.

A lower dynamic flow restrictor 9 is placed on the outside of the equipment X, between the equipment and the production pipe 10, 10 mm under the level of the nozzle system 7.

The nozzle system 7 is composed of 12 channels placed radially towards the production pipe. The equipment X is placed in the production pipe 1_0 centrically.

The liquid precursor Y is water. Water enters the plasma-forming medium generator 5 and changes in it by electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7_into the space between two cylindrical electrodes, the upper electrode 1 and the lower electrode 2 under the effect of the ambient pressure of 25 MPa. Plasma-forming medium Z has a temperature of 50°C and the properties of a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by contact ignition in a liquid environment between the upper electrode 1 and the lower electrode 2. Inter-electrode distance between the upper electrode 1 and the lower electrode 2 is maintained at a constant value of 1 mm after the electric arc 3 has been stabilized.

Example 9

The equipment X has one magnet 4, which is permanent magnet electromagnet and is placed around the nozzle system inlet 6 above the nozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of the equipment X, between the equipment and the production pipe 10, 10 mm above the level of the nozzle system 7.

The nozzle system 7 is composed of 60 channels placed radially towards the production pipe. The equipment X is placed in the production pipe 1_0 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with a concentration of 10 % by weight. It enters the plasma-forming medium generator 5 and changes in it by thermal decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode 1 and the lower electrode 2 under the effect of the ambient pressure of 5.03 MPa. Plasma-forming medium Z has a temperature of l00°C and the properties of a mixture of water and oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode 1 and the lower electrode 2. Inter-electrode distance between the upper electrode 1 and the lower electrode 2 is maintained at a constant value of 15 mm after the electric arc 3 has been stabilized.

Example 10

The equipment X has two permanent magnets. An upper dynamic flow restrictor 8 is placed on the outside of the equipment X, between the equipment and the production pipe Hf, at least 10 mm above the level of the nozzle system 7. The nozzle system is composed of 150 channels placed 90° from the radial direction towards the production pipe. The equipment X is placed in the production pipe J_0 centrically.

The liquid precursor Y is aqueous sodium hydroxide solution with a concentration of 5% by weight. It enters the plasma-forming medium generator 5 and changes in it by electrochemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode l and the lower electrode 2 under the effect of the ambient pressure of 60 MPa. Plasma-forming medium Z has a temperature of 374°C and the properties of a mixture of supercritical water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode l and the lower electrode 2 is maintained at a constant value of 0.1 mm after the electric arc 3 has been stabilized.

Example 11

The equipment X has two magnets 4, and both magnets are permanent magnets.

The nozzle system is composed of 18 channels placed 1° from the radial direction towards the production pipe. The equipment X is placed in the production pipe eccentrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with a concentration of 90% by weight.

It enters the plasma-forming medium generator 5 and changes in it by chemical decomposition to the plasma-forming medium Z and this passes through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into the space between two cylindrical electrodes, the upper electrode l and the lower electrode 2 under the effect of the ambient pressure of 22.06 MPa. Plasma-forming medium Z has a temperature of l000°C and the properties of supercritical water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquid environment between the upper electrode I and the lower electrode 2. Inter-electrode distance between the upper electrode l and the lower electrode 2 is maintained at a constant value of 2 mm after the electric arc 3 has been stabilized.

Industrial applicability

The equipment for removing the production pipe in the borehole and method for removing the production pipe in the borehole of this invention is utilised in the mining industry, particularly in the petroleum industry when performing decommissioning operations. List of reference signs

1 - Upper electrode

2 - Lower electrode

3 - Electric arc

4 - Magnet

5 - Plasma-forming medium generator

6 - Nozzle system inlet

7 - Nozzle system

8 - Upper dynamic flow restrictor

9 - Lower dynamic flow restrictor

10 - Production pipe

11 - Liquid precursor supply

12 - Electrical power supply

13 - Coolant supply

14 - Data cable

15 - Control unit

16 - First electrode of the generator

17 - Second electrode of the generator

18 - Generator chamber

X - Equipment for removing the production pipe

Y - Liquid precursor

Z - Plasma-forming medium

M - Electromagnet to collect particles of the degraded material C - Centralizer