CH719772A2 - Plasma pulse geo drilling rig. - Google Patents

Abstract

In a plasma pulse geo-drilling device (0), comprising a high-voltage pulse generator (1), high-voltage cabling, a drill head (2) with a drill head connection section (21) and an electrode section (20), which has a plurality of electrodes, a generation of suitably high and steep voltage pulses can be achieved even when drilling at depths of several kilometers and the high-voltage supply can be easily adjusted. This is achieved in that the high-voltage cabling is an HV coaxial cable (10), which is electrically conductively fastened from the high-voltage pulse generator (1) directly into a spark gap (12) on or in the drill head connection section (21) and the spark gap (12) with the several electrodes are electrically connected, so that a plasma channel (3) with voltage peaks between 200kV and 800kV and pulse rise times between 50ns and 500ns can be generated in the spark gap (12) by means of flashover voltage.

Description

Technical area

The present invention describes a plasma pulse geo-drilling device comprising a high-voltage pulse generator, high-voltage cabling, a drill head with a drill head connection section and an electrode section which has a plurality of electrodes.

State of the art

[0002] Access to deep energy resources (geothermal energy, hydrocarbons) from deep deposits will play a fundamental role in the next decades. However, drilling to extract deep georesources is extremely expensive. Deep drilling into hard, crystalline rock represents a major challenge for conventional rotary drilling systems as it involves high bit wear and frequent bit replacement, low penetration rates and poor process efficiency.

[0003] With the aim of improving the overall economic efficiency of developing deep georesources in hard rock, we see Plasma-Pulse Geo-Drilling (PPGD) technology as a way out. The resulting plasma pulse geo-drilling process and the necessary technical means lead to a massive cost reduction and simplification of deep drilling compared to the use of conventional rotary drilling systems when the plasma pulse geo-drilling system is optimized.

Plasma-Pulse Geo-Drilling (PPGD) technology for use in deep drilling processes, i.e. deep drilling for the development of oil and gas deposits and geothermal drilling, with final depths of a few meters to a few kilometers, had its origins in Russia. PPGD potentially develops its advantage in crystalline rock and is therefore ideal for geothermal energy or other activities in hard rock.

[0005] The PPGD technology uses high voltage in the form of electrical pulses that increase within nanoseconds through the rock, creating a plasma in the rock that stimulates the rock from the inside out, i.e. H. against its low tensile strength without mechanical abrasion of a drilling tool, thereby creating a deep borehole. As described, for example, in Rossi et al "Advanced drilling technologies to improve the economics of deep georesource utilization", Applied Energy Symposium: MIT A+B, August 12-14, 2020, Cambridge, USA, a high-voltage pulse generator can be used using a suitable drill head 2 1 and two electrodes in a borehole filled with water 5, a borehole including propulsion can be achieved due to the high-voltage pulses. No wearing drill bit is used and a high rate of penetration (ROP) can still be achieved. In this approach, a suitable electrode arrangement is used to initiate a plasma channel (streamer) 3 using a high-voltage pulse.

The streamer 3 spreads through rock 4 and breaks the rock 4 out from the inside. The electrodes are embedded in the drill head 2 and the process is surrounded by a drilling fluid 5 in the borehole (e.g. oil or water). The entire construction forms a plasma pulse geo-drilling device 0, as shown in Figure 1 according to the prior art.

However, in order for this method to be able to effectively break rock, the plasma channel must pass through the rock and not along the rock surface, i.e. H. through the water as a drilling system.

[0008] This is primarily achieved by a rapid pulse increase. Rise time is an important factor because of the remarkable dependence of the dielectric strength of materials on the time of pulsed voltage application. While the EPB (Electro-Pulse-Boring) process developed in Russia in the 1960s had to use oil as drilling fluid as an insulating and flushing medium, a new process is now supposed to use water, which saves costs and protects the environment.

[0009] What is extremely important in the PPGD process is the provision of extremely rapidly increasing HV pulses with high maximum electrical voltages of greater than 200 kV, preferably up to 500 kV. Usual high-voltage pulse generators 1 are connected via an overhead line directly to the drill head 2, more precisely to a drill head connection section 21, and these voltage pulses are guided to electrodes of an electrode section 20, so that the plasma channel 3 is triggered by the electrodes through the rock 4, whereby rock parts, so-called cuttings, are knocked out become. At least the electrode section 20 is located in the drilling fluid 5, with which the rock parts are transported away, which requires appropriate infrastructure with drilling fluid supply and pumps for removal. As a rule, overhead lines are connected to an insulator element, which then has a conductive connection up to the electrode section 20 via inserted pipe sections.

In known PPGD devices, especially the first ones from the 1960s, high voltage generated is led directly from a high-voltage pulse generator via an overhead line to an insulated connection point on the drill head 2. The voltage pulse should be pulsed to its maximum value extremely quickly, less than 500ns. After reaching the maximum value, the plasma channel is created between electrodes with different polarizations and the voltage collapses and the process is repeated continuously during the drilling process.

With this direct transmission of the voltage pulse, the impairment of the pulse steepness is very low and through constant further development of commercially available high-voltage pulse generators, suitable current/voltage pulses can be generated. However, this arrangement requires an extension of the drill string, a separation of the pulse and fluid guidance in the drill string and thus an interruption of the drilling operation. This is particularly disadvantageous for deep drilling, where depths of several kilometers are to be drilled.

In further developments, the voltage pulse has been generated using a suitable high-voltage pulse generator located inside the drill head. To do this, the high-voltage pulse generator 1 practically had to be integrated into the drill head and it had to be constantly carried along with the drill head. In principle, this is the most desirable variant, but to date no one has succeeded in reliably generating the pulse energies required for an economical drilling speed in such a limited space and in reconciling them with other important parameters such as drilling fluid throughput, etc. The size of the suitable high-voltage pulse generator is problematic and the electronics must be protected against drilling fluid and chipped cuttings, which has not been possible so far.

[0013] The PPGD method relies on extremely rapidly increasing HV pulses. While generating the pulse height is usually not problematic, the pulse steepness becomes a problem. However, the desired voltage pulses must also arrive primarily at the ends of the majority of electrodes and thus on the rock surface to be drilled.

The PPGD devices used so far did not yet have the desired efficiency, time savings and drilling quality. As a result, this process and plasma pulse geo-drilling equipment could not successfully establish itself on the market.

Presentation of the invention

The present invention has set itself the task of further developing a plasma pulse geo-drilling device for plasma-pulse geo-drilling (PPGD) in such a way that the generation of suitably high and steep voltage pulses is achieved even when drilling at depths of a few kilometers is, problem-free tracking of the high-voltage supply is achieved when using water or a water-based liquid as drilling fluid, so that maximized drilling efficiency results in continuous operation.

The quality of the pulse transmission link is significantly influenced by the electrical circuitry, the drill head geometries and the materials used for the drill head and the drilling fluid. From an electrical engineering point of view, an isolated consideration of the individual components and also the pulse transmission path does not make sense, since the entire system, including the high-voltage pulse generator, interacts.

Variations of combinations of features or adaptations of the invention can be found in the detailed description, shown in the figures and included in the dependent claims.

Brief description of the drawings

A preferred embodiment of the subject matter of the invention is described below in connection with the accompanying drawings in the detailed description.

Further features, details and advantages of the invention also emerge from the following description of slightly modified embodiments of the invention, some of which will be clear to those skilled in the art from the drawings alone. 1 shows a schematic view of a plasma pulse geo-drilling device known from the prior art with a high-voltage pulse generator outside the drill head, with the drill head partially embedded in the rock. Figure 2 shows a plasma pulse geo-drilling device according to the invention in a schematic representation, whereby the voltage pulse generation is optimized and a plasma channel is generated in the rock. Figure 3a shows a schematic perspective view of an optimized drill head hanging outdoors, the electrically optimized plasma pulse geo-drilling device, while Figure 3b shows a schematic side view of a drill head with an integrated spark gap and Figure 3c shows a schematic view of a preferred electrode pattern of the optimized drill head .

Description

The plasma pulse geo-drilling device 0 according to the invention has a high-voltage pulse generator 1, a drill head 2, comprising an electrode section 20 with a plurality of electrodes and a drill head connection section 21 for connection to the high-voltage pulse generator 1. The complete drill head 2 is inserted into a rock 4, surrounded by a drilling fluid 5 in the form of water or a water-based liquid consisting of up to 100% water, with plasma channels 3, called streamers 3, being generated by electrical high-voltage pulses, which are pieces of rock break out of the bottom of the borehole. With each high-voltage pulse, more or less rock is broken out, the waste is removed and the borehole is enlarged in continuous operation.

A high-voltage pulse generator 1 is used, which generates voltage pulses of 400 kV to 500 kV and energies between 3 and 4 kJ, for example from 40 kV DC side.

The high-voltage pulse generator 1 is connected to the drill head 2 via an HV coaxial cable 10 as high-voltage cabling. An extension device 11 is indicated here in order to adjust the HV coaxial cable 10 and also the flushing device of the drilling fluid 5 according to the drilling depth. This makes it possible to continuously unwind the HV coaxial cable 10 as the drill hole depth increases, instead of constant interruptions to the drilling and thus flushing process according to the prior art. The HV coaxial cable is compact and light, making it easier to use.

The rapidly increasing voltage pulse generated by the high-voltage pulse generator 1 has a flattened pulse steepness due to the HV coaxial cable 10. At the head end of the HV coaxial cable 10, the pulse steepness is reduced to such an extent that an optimal plasma channel 3 cannot be generated and the efficiency of breaking out rock is too low and cannot be reproduced. Here, a spark gap 12 is attached to the HV coaxial cable 10 in or on the drill head 2 in order to make the voltage pulse steeper again. Here, the spark gap 12 is preferably arranged in the drill head 2, more precisely in the area of the drill head connection section 21, with the high voltage being passed to the plurality of electrodes through an appropriate electrical connection. The arrangement of the spark gap 12 in the drill head connection section 21 is more stable and safer and leads to a more compact structure of the drill head 2 than in variants known from the prior art.

The spark gap 12 is preferably designed as a gas-encapsulated spark gap 12 or with an encapsulated gas-tight housing, whereby extremely steep high-voltage pulses can be achieved and unwanted flashovers to the drill head 2 are excluded.

The spark gap 12 has two separate conductors or an interrupted conductor in an encapsulated gas-tight housing. Electrical supply and discharge lines are arranged on both conductors or the sections of the interrupted conductor on both sides of the housing. The spark gap is directly or indirectly electrically connected to the electrodes by two or the interrupted conductor.

Parts carrying high voltage are not openly accessible, which ensures safe operation. Due to the arrangement in the drill head connection section 21, the spark gap 12 is secured and protected, but is still easily accessible. The space available in our drill head 2 or drill head connection section 21 is sufficient for the spark gap 12 to be installed.

[0027] Voltage pulses can be achieved using a spark gap 12, which range from 200 kV upwards and for a short time even reach maximum voltages of up to 800 kV and pulse durations between 50 ns and 500 ns. The pulse duration depends largely on the design of the pulse generator and the test parameters. The required steepness is given due to the spark gap 12. Thus, even with simple electrode arrangements, deep drilling using water or a water-based liquid as drilling fluid 5 can also be carried out as a so-called loop at a depth of several kilometers.

A first electrical high voltage is passed through the HV coaxial cable 10 to the spark gap 12 on or in the drill head 2. The spark gap 12 is formed here by a housing which is filled with a gas, so that the flashover voltage is in the range of the desired 400kV to 500kV and the required steepness of the voltage pulse is also given. This can be estimated using the well-known Paschen law. If roughly one kV of voltage is required for air under standard conditions per millimeter of distance between the conductors of the spark gap 12 until a spark flashes, the dimensions for air are 400 to 500 millimeters, which can be achieved by using other pressurized gases and the Encapsulation can be made even smaller. Integration into the drill head 2 or drill head connection section 21 is therefore possible without any problems.

The high-voltage pulse is conducted from two poles of the spark gap 12 into the electrode section 20 and onto the plurality of electrodes. The plasma channel 3 is formed between at least two electrodes due to the flashover voltage in the rock 4. Using flashover voltage in the spark gap 12, the plasma channel 3 can be generated with voltage peaks between 400kV and 500kV and pulse rise times between 50ns and 500ns.

In order to optimize the plasma channel 3, special developments of the drill head 2 or the electrode section 20 have proven successful, as described below. This modified electrode section 20, in conjunction with the spark gap 12, was able to demonstrate previously unattainable drilling efficiency.

In order to optimize the excavation behavior and thus the excavation performance, an improved arrangement and shape of the plus and minus electrodes was found, which serves the entire drilling cross-section equally and, above all, generates an over-excavation in the edge zone of the drill head 2, so that the drill head 2 can Tracking can be followed safely during the drilling process. A process-reliable supply of high-voltage pulses must always be achieved and the entire drill head 2 must have sufficient mechanical strength. This has been achieved with the arrangement of rod electrodes 200 in the electrode section 20, which is described in more detail below.

The drill head 2 is designed as a metallic frame, comprising at least the electrode section 20 and a drill head connection section 21, which are fastened or molded onto one another. A plurality of n rod electrodes 200 protrude from the electrode section 20 in the direction facing away from the drill head connection section 21. The longitudinal direction is marked with the dashed arrow, with the arrowhead pointing in the feed direction of the drill head 2.

For reasons of stability, the n rod electrodes 200 are rod-shaped and solid, so that they are isolated from one another and distributed over the largest possible area, along the cross-sectional area of the electrode section 20. The n rod electrodes 200 are attached to the electrically conductive drill head connection section 21 in such a way that it is at There are no flashovers or short circuits at high electrical voltages. The drill head connection section 21 is therefore essentially a metallic frame, comprising a plurality of feed struts 210 with direct or indirect contact with the n rod electrodes 200 and at least two connecting flanges 211, 211 'on which the feed struts 210 are attached or formed.

High-voltage cables 10 are connected to the connecting flanges 211, 211' between the spark gap 12 after the high-voltage generator 1. Sufficient stability must also be achieved in the drill head connection section 21 so that short circuits are prevented. Although no mechanical loads occur here as in classic rotary drilling systems, the pressure with which the drill head 2 is pressed onto the rock 4 in the feed direction is quite high.

The rod electrodes 200 are each connected to the first connecting flange 211 and thus indirectly to a first pole of the spark gap or indirectly via the second connecting flange 211 'to a second pole of the spark gap 12 without short circuits or flashovers. This means that different stick electrodes 200 can have different polarizations.

The feed struts 210 can be designed as metallic tubes or as solid rods, while the at least two connecting flanges 211, 211 'are preferably welded on. The distances between feed struts 210, which are polarized differently during operation and subjected to high voltage, are selected to match the high voltage so that short circuits and flashovers are excluded. Since, for example, water 5 is used as drilling fluid 5 in the borehole, the specifications are defined accordingly, so that the plasma channel 3 is preferably generated by the rock 4 during operation.

In Figure 3b, the spark gap 12 is indicated schematically in the drill head connection section 21. It can be seen that the different feed struts 210 ensure the application of tension and mechanical stability. Here the distance between the at least two connecting flanges 211, 211' is approximately half the length of the entire drill head connection section 21. This is indicated by dashed vertical lines in Figure 3b.

In the electrode section 20, a uniform distribution of n rod electrodes 200 of equal thickness arranged parallel to one another, with rod electrode diameters d of greater than 5 mm, particularly preferably 8 mm, has proven to be advantageous. The rod electrode diameter d should be less than 10 mm, as this was the only way to achieve a homogeneous drilling result.

The length L of the n rod electrodes 200 between their tips and the drill head connection section 21 should be greater than 100 mm and preferably less than 200 mm, particularly preferably between 150 and 170 mm. The total length of the drill head 2 should be approximately equal to 2 times the length L of the rod electrodes 200, so that the mechanical stability is sufficient. In order to achieve a homogeneous plasma channel 3 or a homogeneous bore in water 5 as drilling fluid 5, the n rod electrodes 200 with different polarities were arranged in such a way that the distance a between the next adjacent rod electrodes 200 is at least 40 mm, particularly preferably 48 mm.

In addition to an arrangement of parallel rows and columns of stick electrodes 200 with the same polarity, with each stick electrode 200 having two nearest neighbors on both sides in the same row and a left and a right nearest neighbor in each neighboring column, there is a further embodiment proven to be more efficient.

[0041] The electrode arrangement pattern shown in Figure 3c is based on a hexagonal arrangement of rod electrodes 200, with a rod electrode 200 of a first polarity being arranged in the middle of a hexagon and six further rod electrodes 200' being arranged along the circumference of the hexagon on the corners of the hexagon. Even in such an arrangement, the distances a between nearest neighboring electrodes are the same distance a. Except for rod electrodes 200 in the edge area, each rod electrode 200 has six nearest neighbors at a distance a. These nearest neighbors can have the same or opposite polarity, i.e. be subject to a correspondingly polarized electrical voltage. To do this, rod electrodes 200 must be connected to the suitable connecting flange 211. Arrangements are preferred in which rod electrodes 200, each with alternating polarity, are chosen to be arranged along the circumferential line of the hexagon, around the centrally positioned rod electrode 200.

The cross-sectional area Q of the electrode section 20 must be chosen to be greater than the cross-sectional area q of the drill head connection section 21 so that the drill head 2 creates a sufficiently large borehole and can be tracked into the borehole. The cross-sectional area q or the maximum diameter here corresponds to the diameter of the second connecting flange 211 '.

By designing the drill head 2 as a frame, overburden can be transported away using drilling fluid 5.

[0044] The connecting flanges 211, 211' lead to an extremely stable, short-circuit and flashover-free installation of the high-voltage cabling 10 on the drill head 2.

With the drill head 2 described above, so-called loops can also be drilled several kilometers deep efficiently, cost-effectively, using water or a water-based liquid as drilling fluid 5 and without major mechanical wear. What is crucial is that the n rod electrodes 200 are placed on the rock as homogeneously as possible. The drill head 2 is tracked and placed on the rock 4, then one or more voltage pulses occur, knocked-out rock is removed and the drill head 2 is tracked again.

The stick electrodes 200 described here make it possible to place point supports of the stick electrodes 200 distributed over the entire drilling cross section, since the stick electrodes 200 are distributed over the cross-sectional area of the electrode section 20. There are no electrical cross-connections between the individual rod electrodes 200 and the distances between the feed struts 210 and connecting flanges 211, 211 'are selected accordingly. The ends of the individual rod electrodes 200 are preferably designed as a spherical head with a defined radius, so they do not taper to a point. Rock parts broken out during operation, so-called cuttings, are reduced in size by the uniform, homogeneous arrangement of the rod electrodes 200 in such a way that the transport diameter for removal is safely achieved and the cuttings are prevented from jamming in the drill head 2. Good drilling results were achieved in the tests carried out, which are also advantageous in continuous drilling operations.

Reference symbol list

0 Plasma pulse geo-drilling device 1 High-voltage pulse generator (40kVDC/480kV, 3..36kJ pulse voltage) 10 HV coaxial cable = high-voltage cabling 11 Extension device 12 Spark gap 2 Drill head 20 Electrode section 200 n stick electrodes d stick electrode diameter (preferably 8mm) a Distance to nearest neighbors (preferably > 40mm, 48mm) L Length of the rod electrodes between tip and drill head connection section Q Cross-sectional area of the electrode section 20 21 Drill head connection section 210 Feed strut 211, 211' Connection flange q Cross-sectional area of the drill head connection section 21 3 Plasma channel/streamer 4 Rock 5 Drilling fluid (preferably water or water-based Liquid)

Claims (10)

1. Plasma pulse geo-drilling device (0), comprising a high-voltage pulse generator (1), high-voltage cabling, a drill head (2) with a drill head connection section (21) and an electrode section (20) which has a plurality of electrodes, characterized in that the high-voltage cabling is an HV coaxial cable (10), which is electrically conductively fastened from the high-voltage pulse generator (1) directly into a spark gap (12) on or in the drill head connection section (21), and the spark gap (12) is electrically conductively connected to the plurality of electrodes , so that a plasma channel (3) with voltage peaks of 200kV to 800kV and pulse rise times between 50ns and 500ns can be generated by means of flashover voltage in the spark gap (12). 2. Plasma pulse geo-drilling device (0) according to claim 1, wherein the spark gap (12) is formed by a housing which is filled with a pressurized gas. 3. Plasma pulse geo-drilling device (0) according to claim 2, wherein the spark gap (12) has two conductors or an interrupted conductor in an encapsulated gas-tight housing, the conductors being directly or indirectly electrically connected to the electrodes. 4. Plasma pulse geo-drilling device (0) according to one of the preceding claims, wherein the spark gap (12) is fastened in the drill head connection section (21) and the conductors of the spark gap (12) are connected directly to the electrodes of the electrode section (20). . 5. Plasma pulse geo-drilling device (0) according to one of the preceding claims, wherein the drill head connection section (21) is designed in the form of a frame with feed struts (210) and at least two connection flanges (211, 211 '), the spark gap (12 ) in the drill head connection section (21) and the conductors of the spark gap (12) on the first connection flange (211) and on the second connection flange (211 ') are electrically conductively connected and thus indirectly with the plurality of electrodes. 6. Plasma pulse geo-drilling device (0) according to claim 5, wherein the electrode section (20) comprises a plurality of metallic rod electrodes (200) which are electrically conductively connected to the spark gap (12), run parallel to each other and are made of metallic tubes or solid rods with diameters (d) of less than 10 mm with the same length (L). 7. Plasma pulse geo-drilling device (0) according to claim 6, wherein the electrode section (20) is designed such that a cross-sectional area (Q) of the electrode section (20), on which the rod electrodes (200) are distributed, is greater than one Cross-sectional area (q) of the drill head connection section (21) on which the feed struts (210) and the at least two connection flanges (211, 211 ') are distributed is selected. 8. Plasma pulse geo-drilling device (0) according to one of claims 6 or 7, wherein the plurality of rod electrodes (200) form parallel rows and columns of rod electrodes (200) with the same polarity, each rod electrode (200) having two nearest neighbors in the same row and has a left and a right nearest neighbor in each neighboring column. 9. Plasma pulse geo-drilling device (0) according to one of claims 6 to 8, wherein an electrode arrangement pattern of the plurality of rod electrodes (200) is based on a hexagonal arrangement of rod electrodes (200), with a rod electrode in the middle of a hexagon ( 200) of a first polarity is arranged and six further rod electrodes (200 ') are arranged along the circumference of the hexagon on the corners. 10. Plasma pulse geo-drilling device (0) according to claim 9, wherein the rod electrodes (200) can be supplied with alternatingly polarized electrical voltage along the hexagonal circumferential line around the central rod electrode (200) and correspondingly with the connecting flanges (211, 211 ') are electrically connected.