Pulse discharge presplitting rock composite mechanical rotary drilling method and system

Abstract

The invention provides a pulse discharge presplitting rock composite mechanical rotary drilling method and system. The method comprises the steps that low-voltage alternating current is output; the low-voltage alternating current is converted into high-voltage direct current, peak value superposition of output voltage is carried out, high-voltage pulses are obtained, and the rising gradient of the high-voltage pulses is improved; performing electrode discharge crushing for multiple times based on the energy of the high-voltage pulse, so that cracks are generated in the rock in contact with the electrode; the rock with cracks is mechanically crushed for multiple times, and meanwhile rock chippings are discharged through slurry circulation; and the processes of electrode discharge crushing and mechanical crushing are repeated until the target drilling condition is met. According to the method, electrode crushing and mechanical crushing are combined, in the rock crushing process, electrode crushing can enable cracks to be generated in the rock through continuous discharging, then the rock is quickly crushed through mechanical crushing, and therefore the crushing efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of high-voltage pulse discharge rock breaking, and in particular relates to a pulse discharge pre-splitting rock composite mechanical rotary drilling method and system. Background Art

[0002] The development of oil and gas in deep or complex formations, geothermal resources, and pile foundation construction in infrastructure require the crushing of hard rocks. After the Industrial Revolution, humans invented steam engines and TNT explosives, which greatly accelerated the efficiency of rock crushing. However, with the continuous expansion of human transformation and utilization of nature, as well as the pursuit of controllable blasting and environmentally friendly crushing technology, new rock crushing technologies are urgently needed to meet these needs. Taking drilling engineering as an example, rock crushing technology is the core content of oil field development, and its cost accounts for more than 50% of the exploration and development costs. The efficiency of rock crushing determines the drilling speed, cost and economic benefits. As the depth and breadth of human resource exploitation deepens, drilling engineering requires the crushing of hard rocks. The traditional mechanical rotary drilling method is difficult to crush high-hardness rocks, and there are problems such as slow drilling, high cost, and even difficulty in drilling.

[0003] With the development of modern science and technology and the intersection of various disciplines, the new high-voltage pulse discharge rock breaking technology has received widespread attention. It has the characteristics of safety, high efficiency and no pollution. When high-voltage pulse discharge is used to break rocks, it is necessary to ensure that the electrodes and rocks are in a liquid environment and the electrodes are placed on the rock surface. By adjusting the high-voltage pulse parameters and electrode types, the plasma channel can be controlled to form inside the rock. After the plasma channel is formed inside the rock medium, with the rapid injection of external electrical energy, the high-temperature and high-pressure plasma channel expands outward rapidly, generating strong mechanical stress in a very short time, and radiating pressure waves outward, inducing cracks in the rock formation and causing fragmentation; through the cumulative effect of multiple pulse discharges, the electrode moves forward to achieve rock breaking and drilling.

[0004] High-voltage pulse discharge rock breaking technology can solve the problem that traditional rotary rock breaking technology is difficult to break high-hardness rocks. In high-voltage pulse discharge rock breaking technology, the breaking electrode often uses a coaxial "claw electrode", and the breaking and drilling of the rock can only be achieved with the help of repeated pulse discharge. When the number of pulse discharges is small, the rock breaking area and breaking depth are limited, and the breaking area generated under the "claw electrode" is asymmetric, which is difficult to meet the drilling needs of circular apertures. The arc shape is circular, and the maximum penetration depth is the center position of the high-voltage electrode and the grounding electrode. Since the dielectric breakdown is random and cannot be controlled, and for the "claw electrode", the distance between the high-voltage electrode and the grounding electrode is generally far, which increases the randomness of the dielectric breakdown, and it is impossible to ensure that the number of arcs formed between each pair of electrodes is equal. Therefore, it may happen that the number of discharges between some pairs of electrodes is more than that between other pairs of electrodes, which ultimately leads to asymmetric breaking areas. Summary of the invention

[0005] In order to solve at least one problem in the background technology, the present invention provides a pulse discharge pre-splitting rock composite mechanical rotary drilling method and system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A pulse discharge pre-splitting rock composite mechanical rotary drilling method, comprising the following steps:

[0008] Output low voltage AC power;

[0009] Convert low voltage AC into high voltage DC, and perform peak superposition of the output voltage to obtain high voltage pulses, and increase the rising steepness of the high voltage pulses;

[0010] Based on the energy of high-voltage pulses, several electrode discharges are performed to generate cracks inside the rock in contact with the electrodes;

[0011] The cracked rock is mechanically crushed several times, and the rock fragments are discharged through mud circulation;

[0012] The process of electrode discharge crushing and mechanical crushing is repeated until the drilling target conditions are met.

[0013] Preferably, the drilling target conditions include:

[0014] The drilling wellbore is 216-311 mm and the depth is 5000m-8000m.

[0015] A pulse discharge pre-splitting rock composite mechanical rotary drilling system, comprising:

[0016] A generator unit for outputting low voltage alternating current;

[0017] The voltage superposition boost unit is used to convert low-voltage AC power into high-voltage DC power and perform peak superposition of the output voltage to obtain a high-voltage pulse;

[0018] A high-voltage pulse steepening unit, used to increase the rising steepness of the high-voltage pulse;

[0019] A high voltage pulse transmission unit, used for transmitting high voltage to the crushing electrode unit;

[0020] The crushing electrode unit is used to perform several times of electrode discharge crushing based on the energy of the high-voltage pulse, so as to generate cracks inside the rock in contact with the electrode;

[0021] A mechanical rotary crushing unit for mechanically crushing the cracked rock several times;

[0022] Liquid circulation unit, used to circulate rock debris out of the wellbore and perform mud circulation during electrode crushing and mechanical crushing;

[0023] The process of electrode discharge crushing by the crushing electrode unit and mechanical crushing by the mechanical rotation crushing unit is repeated until the drilling target conditions are met.

[0024] Preferably, the crushing electrode unit comprises an annular body, a high voltage electrode and a grounding electrode;

[0025] A plurality of the high-voltage electrodes and the grounding electrodes are alternately installed on the annular body along the circumferential direction. During operation, a plurality of electric arcs are formed between the high-voltage electrodes and the grounding electrodes.

[0026] Preferably, the diameter of the annular body is 60-72 mm.

[0027] Preferably, the diameter of the annular body is 72 mm.

[0028] Preferably, the number of the high voltage electrodes and the number of the grounding electrodes are 2n, where n≥2.

[0029] Preferably, the voltage superposition boosting unit comprises:

[0030] There are several energy storage elements, which are used to receive high-voltage direct current and perform peak superposition of the output voltage to obtain high-voltage pulses.

[0031] Preferably, the parameters of the energy storage element are set based on drilling target conditions;

[0032] When the drilling well is 216-311mm and the depth is 5000m-8000m, the number of energy storage elements is 5-8, the capacity of a single energy storage element is 15-25nF, the output voltage of a single energy storage power supply is 20-30kV, and the number of discharges N is 40-60 times.

[0033] Preferably, when the drilling well is 216 mm and the depth is 5000 m, the number of the energy storage elements is 7, the capacity of a single energy storage element is 20 nF, the output voltage of a single energy storage power supply is 25 kV, and the number of discharges N is 50 times.

[0034] Beneficial effects of the present invention:

[0035] 1. The method of the present invention combines electrode crushing and mechanical crushing. During the rock crushing process, electrode crushing can generate cracks inside the rock through continuous discharge, and then the rock is quickly crushed by mechanical crushing, thereby improving the crushing efficiency;

[0036] 2. The electrode crushing unit of the present invention is provided with multiple groups of symmetrical high-voltage electrodes and grounding electrodes. During the motor crushing process, a stable electric arc can be formed between the high-voltage electrode and the grounding electrode. In addition, since the electrodes are designed with a symmetrical structure, the electric arc can also remain symmetrical, thereby effectively solving the problem of asymmetric crushing areas. When there are more pairs of high-voltage electrodes and grounding electrodes, the distance between them is shorter, making it easier to break down the rock between them. The electric arc starts from the high-voltage electrode, penetrates into the rock after starting, and finally reaches the grounding electrode. Its shape is an arc that is deep in the middle and shallow at both ends. The position where the arc has the greatest penetration depth is the center position of the high-voltage electrode and the grounding electrode. This shows that the change in the electrode structure and the increase in the number of pairs reduce the randomness of rock breakdown to a certain extent, and ensure that the number of arcs formed between adjacent electrodes is approximately equal, thereby ensuring the symmetry of the crushing area.

[0037] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 A flow chart of a pulse discharge pre-splitting rock composite mechanical rotary drilling method of the present invention is shown;

[0040] Figure 2 A block diagram of a pulse discharge pre-splitting rock composite mechanical rotary drilling system of the present invention is shown;

[0041] Figure 3 A simplified structural diagram of a mechanical rotary rock breaking unit is shown;

[0042] Figure 4 The schematic structure diagram of the crushing motor in the fourth embodiment is shown;

[0043] Figure 5 A schematic diagram showing the principle of electrode crushing. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Embodiment 1

[0046] A pulse discharge pre-splitting rock composite mechanical rotary drilling method, such as Figure 1 As shown, the following steps are included:

[0047] S1: Output low voltage AC power;

[0048] S2: convert low voltage AC into high voltage DC, and perform peak superposition of the output voltage to obtain a high voltage pulse, and increase the rising steepness of the high voltage pulse;

[0049] S3: Based on the energy of high-voltage pulses, several electrode discharges are performed to generate cracks inside the rock in contact with the electrodes;

[0050] S4: Mechanically crush the cracked rock several times and discharge the rock debris through mud circulation;

[0051] S5: Repeat the process of electrode discharge crushing and mechanical crushing until the drilling target conditions are met. Specifically, the target conditions include a wellbore size of 216mm-311mm and a depth of 5000m-8000m.

[0052] Embodiment 2

[0053] A pulse discharge pre-splitting rock composite mechanical rotary drilling system, such as Figure 2As shown, a pulse discharge pre-splitting rock composite mechanical rotary drilling method used in Example 1 includes a generator unit, a voltage superposition boost unit, a high-voltage pulse steepening unit, a high-voltage pulse transmission unit, a crushing electrode unit, a mechanical rotary crushing unit and a liquid circulation unit. The generator unit is used to output low-voltage alternating current; the voltage superposition boost unit is used to convert the low-voltage alternating current into high-voltage direct current, and perform peak superposition of the output voltage to obtain a high-voltage pulse; the high-voltage pulse steepening unit is used to increase the rising steepness of the high-voltage pulse; the high-voltage pulse transmission unit is used to transmit the high voltage to the crushing electrode unit; the crushing electrode unit is used to perform several electrode discharge crushing based on the energy of the high-voltage pulse to generate cracks inside the rock; the mechanical rotary crushing unit is used to perform several mechanical crushing of the cracked rock; the liquid circulation unit is used to discharge rock debris during electrode crushing and mechanical crushing, and perform mud circulation; the process of electrode discharge crushing of the crushing electrode unit and mechanical crushing of the mechanical rotary crushing unit is repeated until the drilling target conditions are met.

[0054] It should be noted that before executing steps S1 to S5, the radius and number of electrode pairs of the crushing electrode unit, the number, capacity and output voltage of the energy storage elements in the voltage superposition boost unit, the number of discharge times N, etc. are determined according to the drilling requirements.

[0055] It should be further explained that the voltage superposition boost unit includes an energy storage element. Specifically, a plurality of energy storage elements are provided for receiving high-voltage direct current and performing peak superposition of output voltages to obtain high-voltage pulses.

[0056] In addition, if Figure 3 As shown, the mechanical rotary rock breaking unit includes a drill bit, a drill string and an uphole device. The uphole device is installed on the ground, the drill string is connected to the uphole device, and the drill bit is installed at one end of the drill string. In terms of positional relationship, the uphole device is located at the uppermost end, the drill bit is located at the lowermost end, and the drill string is located in the middle. The three are mainly used to realize the connection of mechanical structures and are used to transmit force and torque. Specifically, the uphole device is used to control the rotary drilling distance and drilling pressure, drive the drill string to rotate, and then drive the drill bit to squeeze and crush the rock. In addition, it can also realize torque crushing of the rock. At the same time, the liquid circulation unit includes a drilling fluid input channel and a drilling fluid output channel, and the drilling fluid input channel and the drilling fluid output channel are both connected to the bottom of the well. During the working process, the drilling fluid enters the bottom of the well through the drilling fluid input channel, and at the same time, the motor crushing unit and the mechanical crushing unit produce crushed rock at the bottom of the well, and finally the drilling fluid flows out of the drilling fluid output channel with the crushed rock.

[0057] Embodiment 3

[0058] In some embodiments, the borehole diameter requirement is 216 mm in diameter and 5000 mm in depth. At the same time, the radius of the crushing electrode unit is 72 mm, and the number of electrode pairs is 4. The number of energy storage elements in the voltage superposition boost unit is 5-8, the capacity of a single energy storage element is 15-25 nF, the output voltage of a single energy storage power supply is 20-30 kV, and the number of discharges N is 40-60 times.

[0059] The drilling method of the system of implementation three is described below in combination with implementation one and implementation two, wherein the number of energy storage elements is 7, the capacity of a single energy storage element is 20nF, the voltage of a single energy storage power source is 25kV, and the number of discharges N is 50:

[0060] A: starting the liquid circulation unit and the generator unit, and the generator unit outputs electrical energy (low-voltage alternating current);

[0061] B: The electric energy is first transmitted to the voltage superposition boosting unit to charge the capacitor, and a high-voltage pulse is generated after the capacitor is charged; under the action of the high-voltage pulse steepening unit, the pre-peak rise time of the high-voltage pulse is shortened, and the changed high-voltage pulse is transmitted to the crushing electrode unit through the high-voltage pulse transmission unit. After the electric energy is transmitted to the crushing electrode unit, rock breaking is carried out under the action of the electric pulse. At the same time, the body circulation unit always works during the rock breaking process to ensure the timely discharge of rock debris and waste liquid generated in the rock breaking process.

[0062] C.: Repeat steps A and B N times and control the generator unit to stop working.

[0063] The number of executions N is 50, and its numerical value represents the number of times high-voltage pulse discharge breaks the rock. After 50 repeated discharges, cracks are generated inside the rock, reducing the macroscopic mechanical parameters of the rock such as the compressive strength, and reducing the difficulty of mechanical rotation to break the rock.

[0064] D: Control the mechanical rotary rock breaking unit to work and mechanically break the rock that has been broken by electric pulse.

[0065] E: Repeat steps A, B, C, and D to achieve large-diameter drilling.

[0066] It should be noted that in Example 3, the number of discharges N=50. This is because in order to increase the number of pulse discharges, the life requirements of high-power devices are also increased accordingly, so the rock breaking cost will also increase. For drilling projects with large apertures, the above problems are particularly obvious.

[0067] It should be further explained that during the process of high-voltage pulse discharge to break rocks, plasma channels are formed inside the rocks. The stress waves generated by the expansion of the channels will expand the original cracks in the rocks on the one hand, and will also generate new cracks on the other hand. When the number of pulse discharges is small, the broken area in the rock is limited, but the cracks in the rock have a large distribution range, and lead to a decrease in the macroscopic physical strength of the rock, including the compressive strength and tensile strength of the rock. After the macroscopic physical strength of the rock is reduced, the difficulty of traditional mechanical rotary crushing of the rock is reduced. Based on this, the rock can first be pre-cracked by high-voltage pulse discharge to generate cracks inside the rock, and then the rock can be mechanically crushed by traditional mechanical rock breaking methods. The combination of the two rock breaking methods can improve the service life of the high-voltage pulse discharge rock breaking equipment, increase the drilling speed of rocks with higher hardness, and reduce industrial costs.

[0068] Embodiment 4

[0069] like Figure 4 As shown, the crushing electrode unit includes an annular body, a high-voltage electrode and a grounding electrode. 2n high-voltage electrodes and 2n grounding electrodes are alternately installed on the annular body along the circumferential direction. When working, multiple arcs are formed between the high-voltage electrode and the grounding electrode, n≥2. In theory, the arc develops according to the principle of the shortest path, that is, the starting point of the arc is the high-voltage electrode, which penetrates into the rock after starting and finally reaches the grounding electrode. For a certain arc, its shape is an arc that is deep in the middle and shallow at both ends. The position where the arc has the greatest penetration depth is the center position of the high-voltage electrode and the grounding electrode.

[0070] It should be noted that in this embodiment, the diameter of the annular body is preferably 60-72 mm, and four high-voltage electrodes and four grounding electrodes are provided. In the working state, there is a voltage difference between the high-voltage electrode and the low-voltage electrode, and an arc is generated by discharge, thereby breaking the rock.

[0071] like Figure 5 As shown in the figure, it is a schematic diagram of electrode crushing. It can be seen from the figure that when the electric arc generated by the high-voltage electrode and the grounding electrode passes through the rock formation, internal stress will be generated, and then part of the rock will be directly broken under the action of the internal stress. At the same time, the internal stress will produce more cracks inside the rock formation.

[0072] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pulse discharge pre-splitting rock composite mechanical rotary drilling method, It is characterized in that The following steps are involved: Output low voltage AC power; Convert low voltage AC into high voltage DC, and perform peak superposition of the output voltage to obtain high voltage pulses, and increase the rising steepness of the high voltage pulses; Based on the energy of high-voltage pulses, several electrode discharges are performed to generate cracks inside the rock in contact with the electrodes; The cracked rock is mechanically crushed several times, and the rock fragments are discharged through mud circulation; The process of electrode discharge crushing and mechanical crushing is repeated until the drilling target conditions are met.

2. A pulse discharge pre-splitting rock composite mechanical rotary drilling method according to claim 1, It is characterized in that The drilling target conditions include: The drilling wellbore is 216-311 mm and the depth is 5000m-8000m.

3. A pulse discharge pre-splitting rock composite mechanical rotary drilling system, It is characterized in that include: A generator unit for outputting low voltage alternating current; The voltage superposition boost unit is used to convert low-voltage AC power into high-voltage DC power and perform peak superposition of the output voltage to obtain a high-voltage pulse; A high-voltage pulse steepening unit, used to increase the rising steepness of the high-voltage pulse; A high voltage pulse transmission unit, used for transmitting high voltage to the crushing electrode unit; The crushing electrode unit is used to perform several times of electrode discharge crushing based on the energy of the high-voltage pulse, so as to generate cracks inside the rock in contact with the electrode; A mechanical rotary crushing unit for mechanically crushing the cracked rock several times; Liquid circulation unit, used to circulate rock debris out of the wellbore and perform mud circulation during electrode crushing and mechanical crushing; The process of electrode discharge crushing by the crushing electrode unit and mechanical crushing by the mechanical rotation crushing unit is repeated until the drilling target conditions are met.

4. A pulse discharge pre-splitting rock composite mechanical rotary drilling system according to claim 3, It is characterized in that The crushing electrode unit comprises an annular body, a high voltage electrode and a grounding electrode; A plurality of the high-voltage electrodes and the grounding electrodes are alternately installed on the annular body along the circumferential direction. During operation, a plurality of electric arcs are formed between the high-voltage electrodes and the grounding electrodes.

5. A pulse discharge pre-splitting rock composite mechanical rotary drilling system according to claim 4, It is characterized in that The diameter of the annular body is 60-72 mm.

6. A pulse discharge pre-splitting rock composite mechanical rotary drilling system according to claim 5, It is characterized in that The diameter of the annular body is 72 mm.

7. A pulse discharge pre-splitting rock composite mechanical rotary drilling system according to claim 4, It is characterized in that The number of the high voltage electrodes and the grounding electrodes is 2n, where n≥2.

8. A pulse discharge pre-splitting rock composite mechanical rotary drilling system according to claim 4, It is characterized in that The voltage superposition boost unit comprises: There are several energy storage elements, which are used to receive high-voltage direct current and perform peak superposition of the output voltage to obtain high-voltage pulses.

9. A pulse discharge pre-splitting rock composite mechanical rotary drilling system according to claim 8, It is characterized in that The parameters of the energy storage element are set based on the drilling target conditions; When the drilling wellbore is 216-311mm and the depth is 5000m-8000m, the number of the energy storage elements is 5-8, the capacity of a single energy storage element is 15-25nF, the output voltage of a single energy storage power supply is 20-30kV, and the number of discharges N is 40-60 times.

10. A pulse discharge pre-splitting rock composite mechanical rotary drilling system according to claim 9, It is characterized in that When the drilling well is 216 mm and the depth is 5000 m, the number of energy storage elements is 7, the capacity of a single energy storage element is 20 nF, the output voltage of a single energy storage power supply is 25 kV, and the number of discharges N is 50 times.

Images