Part of a drill head for a plasma pulse geo drilling system

Abstract

In the case of a drill head initial part (2) as part of a drill head for a plasma pulse geo drilling system, the drill head initial part (2) comprising at least one electrode section (20) which has a plurality of metal bar electrodes (200) and to which a high-voltage feed (10) can be attached and it being possible for differently polarized voltage pulses to be applied to the bar electrodes (200) by a high-voltage pulse generator (1), continuous drilling operation with increased efficiency is intended to be achieved when using water as drilling fluid. This is achieved in that a drill head connection section (21) in the form of a frame with feed struts (210) and at least two connection flanges (211, 211') is electrically connectedly attached to or integrally formed on the electrode section (20), and the bar electrodes (200) of the electrode section (20) are configured oriented with the same length (L) with diameters (d) of less than 20 mm in a manner running parallel to each other and terminating on a planar electrode face, a cross-sectional area (Q) of the electrode section (20) over which the bar electrodes (200) are distributed being selected to be larger than or equal to a cross-sectional area (q) of the drill head connection section (21) over which feed struts (210) and the at least two connection flanges (211, 211') are distributed.

Description

Technical field

[0001] The present invention describes a drill head start part as part of a drill head for a plasma pulse geo-drilling system, wherein the drill head start part comprises at least one electrode section with several metallic rod electrodes, to which a high voltage supply can be attached and the rod electrodes can be subjected to differently polarized voltage pulses by a high voltage pulse generator. State of the art

[0002] Access to deep energy resources (geothermal, hydrocarbons) from deep reservoirs will play a fundamental role in the coming decades. However, drilling to extract deep georesources is extremely expensive. Deep drilling into hard, crystalline rock poses a major challenge for conventional rotary drilling systems due to high drill bit wear and frequent bit replacements, 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 solution. The resulting Plasma Pulse Geo-Drilling method and the necessary technical resources lead to a massive cost reduction and simplification of deep drilling compared to the use of conventional rotary drilling systems, provided the Plasma Pulse Geo-Drilling system is optimized.

[0004] Plasma-pulsed geo-drilling (PPGD) technology, used in deep drilling processes for the development of oil and gas deposits and geothermal wells, with final depths ranging from a few meters to several kilometers, originated in Russia. PPGD potentially demonstrates its advantages in crystalline rock and is therefore ideally suited for geothermal energy or other activities in hard rock.

[0005] PPGD technology uses high voltages of several hundred kilovolts in the form of nanosecond-high rising electrical pulses through the rock, creating a plasma within the rock that fractures it from the inside out, i.e., against its low tensile strength, without the mechanical abrasion of a drill bit, thus creating a deep borehole. 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, it is suggested that a borehole and subsequent advance can be achieved using a drill head starter 2, a high-voltage pulse generator 1, and electrodes in a water-filled borehole 5, thanks to the high-voltage pulses. This method eliminates the need for a wear-prone drill bit and apparently achieves a high rate of penetration (ROP), as demonstrated in the illustrated borehole.A high-voltage pulse initiates a plasma channel (streamer) 3. The streamer 3 propagates through the rock 4, fracturing the rock 4 from the inside. The electrodes are embedded in the drill head, and the process is surrounded by drilling fluid 5 in the borehole (e.g., oil or water). The entire assembly forms a plasma pulse geo-drilling system 0, as shown in [reference]. Figure 1 shown according to the state of the art.

[0006] However, for this method to effectively fracture rock, the plasma channel must pass through the rock and not along the rock surface, i.e., through the fluid. This is primarily achieved through a rapid pulse ramp-up. The ramp-up time is a crucial factor due to the significant dependence of a material's dielectric strength on the duration of pulsed voltage application.

[0007] The goal today is to use water or a water-based fluid as drilling fluid to simplify the process. While the EPB (Electro-Pulse Boring) process, developed in Russia in the 1960s, required oil as the drilling fluid for both insulation and flushing, a new process will utilize a water-based drilling fluid, saving costs and protecting the environment.

[0008] However, PPGD technology has not yet achieved the desired efficiency, time savings, and drilling quality. Consequently, this method and the plasma pulse geo-drilling system cannot successfully establish themselves in the market.

[0009] CN112227953 discloses a drill head start section as part of a drill head for a plasma pulse geo-drilling system, wherein the drill head start section comprises at least one electrode section with several metallic rod electrodes to which a high-voltage supply can be attached. However, the known plasma drill head has weaknesses that need to be improved. Description of the invention

[0010] The disadvantages described above, which are known from the prior art, are to be eliminated by the present optimized device and the method that can be carried out with it.

[0011] The present invention aims to optimize a plasma pulse geo-drilling system for carrying out PPGD in such a way as to achieve continuous operation with maximum efficiency when using water or a water-based fluid as drilling fluid. Accordingly, a part of the drill head was designed for a plasma pulse geo-drilling system.

[0012] Variations in feature combinations or minor adjustments to the invention can be found in the detailed description, illustrated in the figures, and included in the dependent patent claims. Brief description of the drawings

[0013] A preferred embodiment of the invention is described below in connection with the accompanying drawings.

[0014] Further features, details and advantages of the invention will become apparent from the following description of preferred embodiments of the invention and the drawings. These are illustrated in Figure 1 shows a schematic view of a plasma pulse geo-drilling system known from the prior art, the reference numerals also applying in the remainder of the description of the invention. Figure 2a shows a schematic perspective of an optimized drill head start section, while Figure 2e is a schematic side view of the drill head start section, without high-voltage connections and generator, and Figure 2c is a section of the sectional view along section line AA. Figure 2b through the electrode section of the drill head start part. Figure 3 shows a schematic perspective of another drill head start part with outer, slightly tilted rod electrodes. Description

[0015] The well-known plasma pulse geo-drilling system 0 with high-voltage pulse generator 1, to which a drill head start section 2, comprising a drill head connection section 21 and a front electrode section 20 with a plurality of n rod electrodes 200, is connected by means of a high-voltage supply 10, has been optimized here. The entire drill head start section 2, as part of a drill head comprising further features, is inserted into a borehole down to the bottom of the borehole. This enables optimized rock excavation 4 in a borehole filled with water as drilling fluid 5 or a water-based drilling fluid 5 containing less than or equal to 100% water, whereby the known plasma channel is generated pulse by pulse.

[0016] To improve the breakout behavior during drilling using the plasma pulse geo-drilling system 0, the shape of the drill head start part 2, or of the electrode section 20, in which a plurality of n rod electrodes are arranged, is of particular importance.

[0017] It was known from the prior art that the number of electrodes should be increased, or electrodes with concentrically arranged "support shoes" were introduced. Rings, plates, and claws in various designs were also arranged in the electrode area. However, these simple modifications did not yield satisfactory results.

[0018] To optimize the breakout behavior and thus the breakout performance, an optimal arrangement and shape of the positive and negative electrodes had to be found. This arrangement must serve the entire borehole cross-section equally and, in particular, generate over-breakout in the edge zone of the drill head start section 2, ensuring that the drill head start section 2 can reliably follow the drill during the drilling process. A reliable supply of high-voltage pulses must be maintained at all times, and the entire drill head start section 2 must possess sufficient mechanical strength. This has been achieved with the arrangement of rod electrodes 200 in the electrode section 20, described in more detail below. The lengths L of all rod electrodes 200 are selected such that all tips of the rod electrodes 200 are flush with a flat electrode surface, ensuring uniform contact of all rod electrodes 200 with the flat borehole bottom.

[0019] The drill head start part 2 is designed as a metallic frame, comprising at least the electrode section 20 and a drill head connection section 21, which are attached to each other or integrally formed.

[0020] A plurality of n rod electrodes 200 extend from electrode section 20 in the direction 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 start part 2.

[0021] For stability reasons, the n rod electrodes 200 are rod-shaped and solid, so that they are insulated from each other 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 no flashovers or short circuits occur at high electrical voltages. The drill head connection section 21 is therefore essentially a metallic frame comprising several feed struts 210 with direct or indirect contact to the n rod electrodes 200 and at least two connection flanges 211, 211' to which the feed struts 210 are attached or integrally formed.

[0022] The connection flanges 211, 211' are generally used to fasten the drill head start part 2 to other components of the drill head and / or to the high voltage supply 10.

[0023] High-voltage cables 10 can be connected to the connection flanges 211, 211' as a form of the high-voltage supply 10 of a high-voltage generator 1, which is located in Figure 2a as indicated by a high-voltage symbol. Sufficient stability must also be achieved in the drill head connection section 21 to prevent short circuits. Although no mechanical loads occur here as in conventional rotary drilling systems, since there is no rotational movement, the pressure with which the drill head start section 2 is pressed against the rock 4 in the feed direction is quite high. Ideally, the axial load on the drill head start section 2 is practically zero. The rod electrodes 200 are each connected to the first connection flange 211 or to the second connection flange 211' in a short-circuit and flashover-free manner. This allows different rod electrodes 200 to have different polarizations.

[0024] Instead of high-voltage cables 10, mechanically more stable struts can also function as high-voltage supply 10, which create mechanical stabilization.

[0025] The feed struts 210 can be designed as metallic tubes or solid bars, 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 in order to prevent short circuits and flashovers. Since an aqueous fluid 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.

[0026] In Figure 2bIt can be seen that the different feed struts 210 provide for tension application and mechanical stability. Here, the distance between the at least two connection flanges 211, 211' is approximately half the length of the entire drill head connection section 21. This is shown with dashed vertical lines in Figure 2b hinted at.

[0027] In the electrode section 20, a uniform distribution of parallel to each other of the same thickness n rod electrodes 200, with rod electrode diameters d of greater than 5mm, particularly preferably of 8mm, but basically with a rod electrode diameter d less than 20 mm, has proven to be advantageous, since only in this way could a homogeneous drilling result be achieved.

[0028] The length L of the n rod electrodes 200 between their tips and the drill head connection section 21 should be greater than 100mm and preferably less than 200mm, particularly preferably between 150 and 170 mm.

[0029] In relation to the length L of the rod electrodes 200 between the tip and the rear end of the rod electrode 200 to the distance a to the nearest neighbor between rod electrodes 200, a ratio of L / a of 1:1 to 5:1 is advantageous. The length L of the rod electrodes 200 is measured between the tip of the rod electrode 200 and the rear end of the rod electrode 200 opposite the tip, regardless of the mounting method.

[0030] Another feature of the drill head start part 2 is a distance x between a first rod electrode mounting level and a second rod electrode mounting level of the various rod electrodes 200. This distance x should preferably correspond to one to three times the distance a.

[0031] The total length of the drill head start part 2 should be approximately greater than or equal to 2 times the length L of the rod electrodes 200, so that the mechanical stability is sufficient.

[0032] In order to achieve a homogeneous plasma channel 3, a uniform distribution of the plasma channels 3 or, consequently, a homogeneous bore in water 5 as drilling fluid 5, the n rod electrodes 200 with different polarity were arranged such that the distance a between the nearest adjacent rod electrodes 200 is at least 10 mm, preferably greater than 40 mm, and preferably 48 mm.

[0033] In addition to an arrangement of parallel rows and columns of rod electrodes 200 with the same polarity, wherein each rod electrode 200 has two nearest neighbors on both sides in the same row and one left and one right nearest neighbor in each neighboring column, a further embodiment has proven to be more efficient.

[0034] The in Figure 2cThe electrode arrangement pattern shown is based on a hexagonal arrangement of rod electrodes 200, wherein a rod electrode 200 of a first polarity is arranged in the center of a hexagon, and six further rod electrodes 200' are arranged along the circumference of the hexagon at its vertices. In such an arrangement, the distances a between nearest neighboring electrodes are also equal to distance a. Except for rod electrodes 200 in the edge region, 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 subjected to a correspondingly polarized electrical voltage. For this to occur, rod electrodes 200 must be connected to the suitable connection flange 211.

[0035] Preferred are arrangements in which rod electrodes 200 with alternating polarity are arranged along the circumferential line of the hexagon, running around the centrally positioned rod electrode 200.

[0036] The cross-sectional area Q of the electrode section 20 must be greater than or equal to the cross-sectional area q of the drill head connection section 21 so that the drill head start section 2 can create a sufficiently large borehole and be guided into the borehole. The cross-sectional area q, or the maximum diameter, corresponds here to the diameter of the second connection flange 211'.

[0037] By designing the drill head start part 2 as a frame, waste rock can be transported away using drilling fluid 5.

[0038] The connection flanges 211, 211' result in an extremely stable, short-circuit and flashover-free mounting of the high-voltage supply 10 to the drill head start part 2.

[0039] In a further embodiment of the electrode section 20, the outer rod electrodes 200', located furthest from the central longitudinal axis, are not arranged parallel to the longitudinal axis, but at an angle away from the longitudinal axis. This embodiment is described in Figure 3 Schematically represented, showing only the upper half of the drill head's initial section 2'. The angle of the outer rod electrodes 200' to the longitudinal axis should be 1.5° or more.

[0040] With the drill head start section 2 described above, so-called loops can also be drilled efficiently and cost-effectively to depths of several kilometers, using water as drilling fluid 5 and without significant mechanical wear. Crucially, the n rod electrodes 200 must be in contact with the rock as homogeneously and evenly as possible. The drill head start section 2 is moved onto the rock 4 and placed in position. Then, one or more voltage pulses are applied until the drill head start section 2 is moved again. Ideally, the drill head start section 2 is balanced, relieved of pressure, or charged in such a way that it automatically and continuously follows the borehole bottom as it moves with the drilling progress.

[0041] The rod electrodes 200 described here allow for point contact of the rod electrodes 200 distributed across the entire borehole cross-section, since the rod 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 connection flanges 211, 211' are also selected accordingly. The ends of the individual rod electrodes 200 are preferably designed as a spherical head with a defined radius; they do not taper to a point. Rock fragments excavated during operation, so-called cuttings, are reduced in size by the uniform, homogeneous arrangement of the rod electrodes 200 to such an extent that the required transport diameter for removal is reliably achieved and wedging of the cuttings in the drill head start section 2 is prevented.The tests carried out yielded good drilling results, which are also advantageous in continuous drilling operation. Reference symbol list

[0042] 0 Plasma pulse geo-drilling system 1 High-voltage pulse generator 10 High-voltage supply (e.g., high-voltage cable) 2 Drill head start section 20 Electrode section 200 n Rod electrodes d Rod electrode diameter (preferably 8 mm) a Distance to nearest neighbor (preferably > 40 mm, 48 mm) L Length of rod electrodes between tip and drill head connection section Q Cross-sectional area of ​​the electrode section 20 21 Drill head connection section 210 Supply 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 fluid)

Claims

1. Drill head initial part (2) as part of a drill head for a plasma pulse geo-drilling system (0), wherein the drill head initial part (2) comprises at least one electrode portion (20) with several metallic rod electrodes (200), to which a high-voltage supply (10) can be attached and the rod electrodes (200) can be applied by a high-voltage pulse generator (1) with differently polarized voltage pulses, wherein at the electrode portion (20), facing away from the side of the rod electrode tips, a drill head connection portion (21) in the form of a frame with feed struts (210) and at least two connection flanges (211, 211') is electrically connected or molded and the rod electrodes (200) of the electrode portion (20) run parallel to each other and terminate on a flat electrode surface with the same length (L) of metallic tubes or solid rods with diameters (d) less than 20 mm are aligned, wherein a cross-sectional area (Q) of the electrode portion (20) on which the rod electrodes (200) are distributed is greater than equal to a cross-sectional area (q) of the drill head connection portion (21) on which feed struts (210) and the at least two connection flanges (211, 211') are distributed, and wherein an electrode arrangement pattern of the plurality of rod electrodes (200) is based on a hexagonal arrangement of rod electrodes (200), wherein in the middle of a hexagon a rod electrode (200) of a first polarity is arranged and along the circumference of the Seckseck on the corners of which six further rod electrodes (200') are arranged.

2. The initial part of the drill head (2) according to claim 1, wherein the plurality of rod electrodes (200) form parallel rows and columns of rod electrodes (200), wherein each rod electrodes (200) have two nearest neighbours in the same row and one left and one right nearest neighbour in each neighbouring column.

3. The initial part of the drill head (2) according to claim 1, wherein except for rod electrodes (200) in the edge region, each rod electrode (200) has six nearest neighbors at the same distance (a) which have the same or the opposite polarity.

4. Drill head initial part (2) according to claim one of the preceding claims, wherein the rod electrodes (200) along the hexagonal circumferential line around the centric rod electrode (200) are each subject to alternately polarized electrical voltage and are electrically conductively connected accordingly to the connection flanges (211, 211').

5. Drill head initial part (2) according to any of the preceding claims, wherein the distance (a) between directly adjacent rod electrodes (200) is equal and at least 10mm.

6. Drill head beginning part (2) according to any one of the preceding claims, wherein the ratio of the length (L) of the rod electrodes (200) between the tip and the rear end of the rod electrode (200) to the distance (a) to the nearest neighbor between rod electrodes (200) L / a is between 1:1 and 5:1.

7. A drill head initial part (2) according to any one of the preceding claims, wherein a distance (x) between a first rod electrode mounting plane and a second rod electrode mounting plane corresponds to the various rod electrodes (200), with a value between one to three times a distance (a).

8. Drill head initial part (2) according to any of the preceding claims, wherein the protruding ends of the rod electrodes (200) are each designed as a ball head, with a defined radius.

9. Drill head initial part (2) according to any one of the preceding claims, wherein the length (L) of the rod electrodes (200) between their tips and the drill head connection portion (21) is greater than 100mm and preferably less than 200mm, especially preferably between 150 and 170mm.

10. The cutterhead initial part (2) according to any of the preceding claims, wherein the total length of the cutterhead initial part (2), electrode portion (20) and cutterhead connection portion (21) together is greater than twice the length (L) of the rod electrodes (200).

11. Cutterhead initial portion (2) according to any one of the preceding claims, wherein the distance between the at least two connection flanges (211, 211') is not more than half the length of the entire cutterhead connection section (21).

12. The cutterhead initial part (2) according to any one of the preceding claims, wherein outer rod electrodes (200') furthest from a centric longitudinal axis of the cutterhead header (2) are arranged at an angle of more than 1.5° away from the longitudinal axis.

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