A rock burst drilling tool and a rock breaking method for rock burst

Abstract

The present invention relates to the field of drilling engineering. More specifically, the present invention relates to a rock burst drilling tool and a rock burst rock breaking method. The rock burst drilling tool mainly includes a bypass valve assembly, a liquid distribution valve assembly, a metal motor assembly, a torque limiter assembly, a drive shaft assembly and a rock burst drill bit. The rock burst drilling tool adopts an all-metal structure and is heat-resistant. During the drilling process at a depth of ten thousand meters, under the condition of high in-situ stress, the in-situ stress of the rock directly below the drill bit is periodically unloaded through the rock burst drilling tool, inducing the rock to release energy, causing tensile failure of the rock and resulting in the rock burst phenomenon, thereby improving the rock breaking efficiency. The deeper the well, the greater the rock burst energy, making the critical geothermal drilling easier.

Description

Technical Field

[0001] The present invention relates to the field of drilling engineering. More specifically, the present invention relates to a rock burst drilling tool and a rock burst rock breaking method. Background Art

[0002] Geothermal energy is gradually formed after the decay of the earth's molten lava and radioactive substances. It is clean, renewable, and extremely abundant. Moreover, the geothermal energy deep in the earth at a depth of 10,000 meters gradually tends to be evenly distributed, with a temperature as high as 200 - 500 °C, which is very suitable for large-scale power generation. Critical geothermal energy is the key to replacing fossil fuels. Water is a supercritical fluid when the pressure exceeds 22 MPa and the temperature is higher than 374 °C. Compared with non-supercritical power plants, power plants using supercritical water as the working fluid can extract up to 10 times more useful energy from each drop of water. Currently, the parameters of the subcritical units of thermal power plants reach 538 °C. Using critical geothermal energy to supply heat to power plants, according to the geothermal gradient of 3 °C per 100 meters, critical geothermal drilling requires more than 18,000 meters.

[0003] Low-cost drilling and extraction of 10,000-meter geothermal energy and critical geothermal energy are the keys to realizing carbon-free energy to replace fossil fuels. The high cost of geothermal development is almost all included in the upfront investment, especially the drilling cost of 10,000-meter deep wells accounts for more than half of the entire project. Conventional rotary drilling rock breaking methods and drilling tools cannot solve the problems of critical geothermal drilling.

[0004] First of all, for conventional drilling rock breaking methods, the deeper the well, the more difficult it is to drill. As the well depth increases, the rocks in the deep formations become harder and more plastic, and the drillability of the formations is poor. During the drilling process in hard and brittle formations, the stick-slip phenomenon is more serious, accelerating the wear of the drill bit and even causing tooth breakage. In addition, the higher the formation temperature, the greater the reduction in the hardness of the drill bit, the worse the wear resistance of the drill bit, and the significant decrease in the drill bit life; the wellbore structure size of ultra-deep wells is larger, the drilling efficiency is lower, and the mechanical drilling speed is slow. The well deviation problem in deep wells is also becoming increasingly prominent. The deeper the well, the more difficult it is to drill, seriously restricting the exploration and development process, and there is an urgent need for a new rock breaking method to significantly improve the rock breaking efficiency.

[0005] Secondly, the existing downhole power tools are no longer applicable. Currently, the stator rubber of conventional positive displacement motors is not heat-resistant, and the working environment temperature is less than 120 °C; even if the stator rubber is modified, it can only work in an environment with a temperature lower than 180 °C, and the life is very short. As the drilling depth increases and the downhole temperature continues to rise, when the bottom hole temperature > 180 °C, the temperature resistance limitation of the elastic rubber causes the positive displacement motor to be unable to meet the drilling requirements. However, currently, China is trying to break through 10,000 meters in drilling, and it is predicted that the temperature will exceed 180 °C, and there are no available power drilling tools. The downhole temperature of critical geothermal wells reaches 600 °C, and there is an urgent need for high-temperature resistant power drilling tools.

[0006] In summary, with the progress of global drilling technology and the increasing demand for mineral resources, exploring deep-earth resources has become an important direction for global mineral exploration. Currently, worldwide, ultra-deep drilling of 10,000 meters and critical geothermal development are still in the experimental and demonstration project stage and far from achieving large-scale application. China is attempting to break through the 10,000-meter ultra-deep drilling and has not yet carried out exploration research on critical geothermal drilling and production. Therefore, it is necessary to develop rockburst drilling equipment and rockburst rock-breaking methods for ultra-deep drilling of 10,000 meters and critical geothermal development to address the current bottleneck in critical geothermal drilling and production technology. Summary of the Invention

[0007] The purpose of the present invention is to provide a rockburst drilling tool and a rockburst rock-breaking method for the above problems.

[0008] To achieve these and other advantages in accordance with the present invention, there is provided a rockburst drilling tool, including a bypass valve assembly, a metal motor assembly, a drive shaft assembly, and a rockburst drill bit sequentially arranged from top to bottom. The metal motor assembly includes a housing. The bypass valve assembly is connected to the upper end of the housing. Inside the housing, N metal motors connected in series by rotors are sequentially arranged from top to bottom, where N ≥ 3. A liquid distribution valve assembly connected to the first metal motor is provided inside the housing. There is a liquid inlet channel between each metal motor and the housing. The liquid distribution valve assembly evenly distributes the drilling fluid to each metal motor. The Nth metal motor is connected to the drive shaft assembly through a torque limiter assembly, and the rockburst drill bit is connected to the drive shaft assembly.

[0009] The beneficial effect of the present invention is that the rockburst drilling tool of the present invention uses a liquid distribution valve assembly to evenly distribute the drilling fluid to each of the metal motors connected in series, reducing the displacement of each motor, thereby achieving a significant reduction in the length of a single-stage rotor and reducing the rotational speed output by the power tool to within the engineering and technical requirements.

[0010] Based on the above technical solutions, the present invention can be further improved as follows:

[0011] Further, the metal motor includes a stator and a rotor. Two adjacent stators are hermetically connected. The rotor is coaxially arranged inside the stator and there is a cavity between them. Upper and lower seals corresponding to the cavity are respectively provided at the upper and lower ends of the rotor. Two stator symmetric holes are provided on the inner side of the stator. A large sealing cylinder is vertically arranged in the stator symmetric holes. Two rotor symmetric holes are provided on the outer side of the rotor. A small sealing cylinder is vertically arranged in the rotor symmetric holes. The large sealing cylinder and the small sealing cylinder divide the cavity into two independent high-pressure chambers and two low-pressure chambers. The stator symmetric holes and the rotor symmetric holes of each metal motor are arranged in a circumferential staggered manner. N groups of vertical grooves are evenly distributed along the circumference on the outer side of the first stator. Each group of vertical grooves includes two oppositely arranged vertical grooves. The outer side of the i-th stator is provided with N-(i - 1) groups of vertical grooves, where i is a positive integer between 2 and N. There is a vertical groove communicating with each vertical groove above it, so as to form N liquid inlet channels between the housing and the multiple stators. A plurality of stator inner holes are vertically and evenly distributed on the inner wall of the lowermost vertical groove of each liquid inlet channel. The rotor is hollow inside, and a plurality of rotor inner holes equal in number to and corresponding one-to-one with the stator inner holes are provided on it.

[0012] The beneficial effects of adopting the above further scheme are as follows: In this further scheme, two adjacent stators are hermetically connected, making each cavity independent. The upper ends of the N liquid inlet channels are evenly distributed along the circumference and correspond to each metal motor. The liquid distribution valve assembly evenly distributes the drilling fluid to each liquid inlet channel. The drilling fluid in each liquid inlet channel enters the corresponding cavity through a plurality of stator inner holes on the inner wall of the lowermost vertical groove. Two large sealing cylinders and two small sealing cylinders are arranged between the rotor and the stator, and the cavity between the rotor and the stator is sequentially divided into a high-pressure chamber, a low-pressure chamber, a high-pressure chamber and a low-pressure chamber. The pressure of the drilling fluid in the high-pressure chamber is greater than the pressure of the drilling fluid in the low-pressure chamber, making one side of the rotor high-pressure and the other side low-pressure, generating a torque that causes the rotor to rotate clockwise. The drilling fluid in the cavity enters the inside of the rotor through a plurality of rotor inner holes on the rotor, and finally falls into the rock burst drill bit and is discharged.

[0013] Further, in the described rock burst drilling tool, a spline sleeve and a sliding bearing are sequentially provided at the lower end of the lower seal. Communication grooves corresponding to the liquid inlet channels are provided on the outer sides of the lower seal body, the spline sleeve and the sliding bearing. The upper and lower stators are respectively in contact with the lower seal body and the sliding bearing. The upper rotor passes downward through the lower seal body, and the lower rotor passes upward through the sliding bearing and is connected to it. The upper and lower rotors are connected through the spline sleeve.

[0014] The beneficial effects of adopting the above further scheme are as follows: In this further scheme, communication grooves corresponding to the liquid inlet channels are provided on the outer sides of the lower seal body, the spline sleeve and the sliding bearing, ensuring the penetration of each liquid inlet channel.

[0015] Further, in the rock burst drilling tool, the liquid distribution valve assembly includes an upper valve plate and a lower valve body. The lower valve body is connected to the stator of the first metal motor. A stepped hole is coaxially provided on the lower valve body. The rotor of the first metal motor extends upward into the stepped hole and is rotatably fitted with the lower valve body. There are 2N vertically penetrating flow guiding grooves evenly distributed along the circumference of the lower valve body. Two opposite flow guiding grooves form a group. The N groups of flow guiding grooves correspond to the N groups of vertical grooves on the outside of the first stator one by one. A retaining piece is provided on the upper valve plate. The lower end of the upper valve plate extends into the stepped hole and is connected to the rotor of the first metal motor. The retaining piece is slidably fitted with the upper end of the lower valve body. When the upper valve plate rotates with the rotor, the two blades can simultaneously seal any group of flow guiding grooves.

[0016] The beneficial effect of adopting the above further scheme is as follows: In this further scheme, during the rotation of the rotor, there is a point where the inner holes of multiple stators and the inner holes of multiple rotors are in one-to-one correspondence and overlap on the same straight line. At this time, the drilling fluid entering the cavity at the inner hole of the stator directly flows out from the inner hole of the rotor and enters the inside of the rotor. No torque is generated on the rotor by the drilling fluid, and this part of the drilling fluid is wasted. At this time, if the corresponding flow guiding grooves can be sealed, no drilling fluid will enter the liquid inlet channel, and this part of the drilling fluid leakage can be avoided. When the drilling fluid drives the motor to rotate, the rotor drives the upper valve plate to rotate together. During the rotation of the two blades on the upper valve plate, each group of flow guiding grooves is sequentially sealed, so that each group of flow guiding grooves of the upper valve plate is periodically closed. Ensure that when the blade seals the upper opening of a certain group of flow guiding grooves, at this time, the inner holes of multiple stators and the inner holes of multiple rotors of the corresponding metal motor are exactly on the same straight line and overlap. At this time, the flow guiding grooves are closed, and the drilling fluid enters other metal motors through other flow guiding groove holes on the lower valve body, thereby reducing the leakage of the drilling fluid.

[0017] Further, in the rock burst drilling tool, an internal spline nut, a preloading spring and a nut are provided in the stepped hole. The internal spline nut is connected to the rotor of the first metal motor. The upper valve plate slidably penetrates through the internal spline nut. The nut is arranged at the lower end of the upper valve plate. The preloading spring is sleeved on the upper valve plate, and its two ends respectively abut against the internal spline nut and the nut.

[0018] The beneficial effect of adopting the above further scheme is as follows: In this further scheme, by sleeving a preloading spring on the upper valve plate, the preloading spring is compressed. Since the height of the internal spline nut is certain, the preloading spring will exert a downward force on the nut and the upper valve plate, so as to ensure that the two blades on the upper valve plate are closely fitted with the upper end of the lower valve body during the sliding process, and ensure the sealing effect of the blades on the flow guiding grooves.

[0019] Further, in the rockburst drilling tool, the torque limiter assembly includes a spline shaft, a spring, an overload actuator, a ball, and a threaded shaft. The spline shaft is connected to the lower end of the Nth rotor. The threaded shaft is tightly connected to the spline shaft through the ball. The spring and the overload actuator are arranged on the spline shaft, and the spring applies a force towards the ball to the overload actuator.

[0020] The beneficial effect of adopting the above further scheme is as follows: In this further scheme, the torque limiter connects the rotor and the transmission shaft, and its main function is overload protection. When the rockburst drill bit gets stuck or there is a mechanical failure, resulting in the required torque exceeding the set value, the steel ball will leave the pit, causing slippage between the driving end component and the driven end component. After the overload situation disappears, it will resume connection automatically, avoiding damage and loss of equipment parts.

[0021] Further, in the rockburst drilling tool, the transmission shaft assembly includes a housing and a core shaft. Upper and lower TC outer sleeves are respectively provided at the openings at the upper and lower ends of the housing. The core shaft is hollow inside, passes through the housing, and is connected to the upper and lower TC outer sleeves through the upper TC inner sleeve and the lower TC inner sleeve respectively. Both ends of the core shaft are connected to the torque limiter assembly and the rockburst drill bit respectively. A plurality of receiving holes are evenly distributed in the circumferential direction at the lower end of the lower TC outer sleeve, and cylindrical rollers are rotatably arranged in the receiving holes.

[0022] The beneficial effect of adopting the above further scheme is as follows: In this further scheme, the core shaft is hollow inside and is connected to the inside of the rotor. The drilling fluid inside the rotor flows through the inside of the core shaft and finally enters the rockburst drill bit. The upper end of the core shaft extends into the torque limiter and is fixed to it through an upper fixing nut. Its lower end is fixed to the lower TC inner sleeve through a lower fixing nut. End caps are respectively arranged at the lower end of the upper TC outer sleeve and the upper end of the lower fixing nut. A plurality of inner rings and outer rings sleeved on the core shaft are arranged in a staggered manner up and down between the two end caps, and a spacer sleeve is sleeved on the inner ring.

[0023] Further, in the rockburst drilling tool, the rockburst drill bit includes an annular drill bit, a core drill bit, and a water eye nozzle. The annular drill bit is hollow inside, and its upper end corresponds to the lower end of the lower TC outer sleeve. An arc surface corresponding to a plurality of cylindrical rollers is provided at the upper end of the annular drill bit. The core drill bit is slidably arranged up and down inside the annular drill bit, and its upper end is connected to the lower end of the core shaft. The water eye nozzle is arranged on the core drill bit.

[0024] The beneficial effects of adopting the above further solution are as follows: In this further solution, the core bit and the annular bit can slide relatively up and down. The core bit is connected to the core shaft and rotates together during the drilling process, driving the annular bit to rotate at the same time. Meanwhile, a high-frequency reciprocating motion occurs between the annular bit and the core bit. The multiple arc surfaces at the upper end of the annular bit form a wavy surface. During the rotation of the annular bit, the cylindrical rollers at the lower end of the lower TC jacket do not rotate. When the upper end of the annular bit moves upward to contact the multiple cylindrical rollers at the lower end of the lower TC jacket, controlled by the wavy surface, when the annular bit moves downward, the drilling pressure gradually increases, and at the same time, the core bit moves upward, and the drilling pressure is gradually unloaded to zero; when the annular bit moves upward, the drilling pressure rapidly decreases and is gradually unloaded to zero, and at the same time, the core bit moves downward, and the drilling pressure gradually increases to the maximum value; during the drilling process, the annular bit and the core bit unload alternately. When the annular bit has the maximum drilling pressure, the drilling pressure of the core bit is zero; when the core bit has the maximum drilling pressure, the drilling pressure of the annular bit is zero; when the drilling pressure is unloaded and decreased, the rock follows and is rapidly unloaded. When unloaded in one direction, the rock undergoes elastic bulging deformation, showing tensile failure. Rocks are not resistant to tension but only to compression, and the tensile strength is only 1 / 8 of the compressive strength, making the rock easier to break; deep rocks are stressed in three axes and six directions and store a large amount of elastic strain energy. When a single-sided load is suddenly unloaded, after the one-way expansion deformation occurs, the stresses in other directions will also be unloaded successively, accelerating the bulging deformation in the one-way unloading direction, and the rock is instantaneously damaged by the excess energy, resulting in rock burst, making deep drilling easier. When the drilling pressure is unloaded so that the compression energy of the rock is equal to the tensile failure energy, only damage occurs; when the stress of the rock compression deformation is much greater than the tensile strength and the rock is rapidly unloaded, the rock undergoes tensile deformation, the rock is instantaneously damaged, and the stored excess elastic strain energy is released, resulting in rock burst, making deep drilling easier. The annular bit and the core bit are connected through keyway fit. A plurality of strip-shaped grooves are evenly distributed along the circumference on the inner wall of the annular bit, and splines are arranged to slide up and down in the strip-shaped grooves. The splines are connected to the core bit, realizing the connection between the annular bit and the core bit through keyway fit.

[0025] The present invention also provides another rock burst drilling tool, including a bypass valve assembly, a screw motor assembly, a universal shaft assembly, a transmission shaft assembly, and a rock burst bit connected in sequence from top to bottom.

[0026] The beneficial effects of adopting the above further solution are as follows: In this further solution, the screw motor assembly and the universal shaft assembly are used to replace the metal motor assembly and the torque limiter assembly. The existing screw motor assembly is used as a power source to drive the rock burst bit to rotate, mainly for accelerating the drilling speed in conventional drilling with a temperature lower than 150°C.

[0027] The present invention also provides a rock burst rock breaking method, using any one of the above-mentioned rock burst drilling tools, including the following steps:

[0028] S1. Lower the rock burst drilling tool to the bottom of the well and connect the bypass valve assembly to the drilling pump.

[0029] S2. Start the drilling pump and inject high-pressure drilling fluid into the rock burst drilling tool. After passing through the liquid distribution valve assembly, the drilling fluid is evenly distributed into the liquid inlet channels of each metal motor of the metal motor assembly. Each metal motor starts to rotate and drives the rock burst bit to rotate through the torque limiter assembly and the drive shaft assembly. After the pump starts normally, record the displacement and pump pressure.

[0030] S3. Further lower the drill string. After the rock burst bit contacts the bottom of the well, gradually apply pressure and adjust to the expected mechanical drilling rate, and record the pump pressure.

[0031] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and will also be understood by those skilled in the art through the research and practice of the present invention. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the rock burst drilling tool described in an embodiment of the present invention;

[0033] Figure 2 is Figure 1 Cross-sectional views at A-A, B-B, C-C and D-D in

[0034] Figure 3 It is a schematic structural diagram of the metal motor described in the present invention;

[0035] Figure 4 It is a schematic structural diagram of the stator described in the present invention;

[0036] Figure 5 It is a cross-sectional view of the stator described in the present invention;

[0037] Figure 6 It is a schematic structural diagram of the rotor described in the present invention;

[0038] Figure 7 It is a cross-sectional view of the rotor described in the present invention;

[0039] Figure 8 It is a cross-sectional view of the liquid distribution valve assembly described in the present invention;

[0040] Figure 9 It is a schematic structural diagram of the upper valve plate described in the present invention;

[0041] Figure 10 It is a schematic structural diagram of the lower valve body described in the present invention;

[0042] Figure 11 It is a top view of the lower valve body described in the present invention;

[0043] Figure 12 Schematic connection diagram of the torque limiter assembly, drive shaft assembly and rock burst bit described in the present invention;

[0044] Figure 13 Three-dimensional structural schematic diagram of the contact state between the lower TC outer sleeve of the drive shaft, cylindrical roller and the waveform surface on the upper end face of the ring bit described in the present invention;

[0045] Figure 14 Structural schematic diagram of the rock burst bit described in the present invention;

[0046] Figure 15 Side view of the rock burst bit described in the present invention;

[0047] Figure 16 Structural schematic diagram of the ring bit described in the present invention;

[0048] Figure 17 Structural schematic diagram of the core bit described in the present invention;

[0049] Figure 18 Schematic connection diagram of the ring bit and the core bit described in the present invention;

[0050] Figure 19 Structural schematic diagram of the rock burst drilling tool in another embodiment of the present invention.

[0051] Among them, the reference numerals are represented as:

[0052] 1. Bypass valve assembly; 2. Liquid distribution valve assembly; 201. Upper valve plate; 202. Lower valve body; 203. Internal spline nut; 204. Preloading spring; 205. Nut; 3. Metal motor assembly; 301. Compression spring; 302. Upper seal; 303. Housing; 304. Stator; 305. Rotor; 306. Large sealing cylinder; 307. Small sealing cylinder; 308. Lower seal body; 309. Spline sleeve; 310. Sliding bearing; 4. Torque limiter assembly; 401. Spline shaft; 402. Spring; 403. Overload action body; 404. Ball; 405. Threaded shaft; 5. Drive shaft assembly; 501. Upper fixing nut; 502. Upper TC inner sleeve; 503. Upper TC outer sleeve; 504. Housing; 505. End cover; 506. Outer spacer sleeve; 507. Inner ring; 508. Outer ring; 509. Inner spacer sleeve; 510. Support sleeve; 511. Lower fixing nut; 512. Lower TC inner sleeve; 513. Lower TC outer sleeve; 514. Cylindrical roller; 515. Core shaft; 6. Rock burst bit; 601. Ring bit; 602. Core bit; 603. Water eye nozzle; 7. Screw motor; 8. Cardan shaft assembly. Detailed implementation manners

[0053] The following further elaborates on the present invention in conjunction with embodiments, so that those skilled in the art can implement it with reference to the text of the specification.

[0054] It should be noted that in the description of the present invention, the orientation or positional relationship indicated by terms such as "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0055] As Figure 1 shown, an embodiment of the present invention provides a rockburst drilling tool, which includes a bypass valve assembly, a metal motor assembly, a drive shaft assembly, and a rockburst drill bit arranged in sequence from top to bottom. The metal motor assembly includes a housing. The bypass valve assembly is connected to the upper end of the housing. Inside the housing, 4 rotors in series are arranged from top to bottom. A liquid distribution valve assembly connected to the first metal motor is provided inside the housing. There is a liquid inlet channel between each metal motor and the housing. The liquid distribution valve assembly evenly distributes the drilling fluid to each metal motor. The fourth metal motor is connected to the drive shaft assembly through a torque limiter assembly, and the rockburst drill bit is connected to the drive shaft assembly.

[0056] Among them, as Figure 3 shown, the metal motor is composed of a compression spring, an upper seal, a stator, a rotor, a large seal cylinder, a small seal cylinder, a lower seal body, a spline sleeve, and a sliding bearing. Sliding bearings and a lower seal body are arranged on both sides of the stator. Inside the stator is the rotor. The lower seal body supports the lower shaft of the first rotor. The first rotor is connected to the second rotor through a spline sleeve. In turn, the second rotor is connected to the third rotor through a spline sleeve, and the third-stage rotor is connected to the fourth-stage rotor through a spline sleeve. The stator and the rotor, and two adjacent stators are hermetically connected. The rotor is coaxially arranged inside the stator and there is a cavity between them. The rotor structure is as Figures 6 - 7 shown. Upper and lower seals corresponding to the cavity are respectively provided at the upper and lower ends of the rotor. As Figure 2As shown in the figure, two stator symmetric holes are provided on the inner side of the stator. A large sealing cylinder is vertically provided in the stator symmetric holes. Two rotor symmetric holes are provided on the outer side of the rotor. A small sealing cylinder is vertically provided in the rotor symmetric holes. The large sealing cylinder and the small sealing cylinder divide the cavity into two independent high-pressure cavities and two low-pressure cavities. The stator symmetric holes and the rotor symmetric holes of each metal motor are arranged in a circumferential staggered manner. The adjacent two stators are hermetically connected, so that each cavity is independent. The upper ends of the 8 liquid inlet channels are evenly distributed in the circumferential direction and correspond to each metal motor. The liquid distribution valve assembly evenly distributes the drilling fluid to each liquid inlet channel. The drilling fluid in each liquid inlet channel enters the corresponding cavity through a plurality of stator inner holes on the inner wall of the vertical groove at the bottom. Two large sealing cylinders and two small sealing cylinders are arranged between the rotor and the stator, and the cavity between the rotor and the stator is sequentially divided into a high-pressure cavity, a low-pressure cavity, a high-pressure cavity and a low-pressure cavity. The pressure of the drilling fluid in the high-pressure cavity is greater than the pressure of the drilling fluid in the low-pressure cavity, so that one side of the rotor is high-pressure and the other side is low-pressure, generating a torque that makes the rotor rotate clockwise. The drilling fluid in the cavity enters the rotor through a plurality of rotor inner holes on the rotor and finally falls into the rock burst bit and is discharged. The lower end of the lower seal is sequentially provided with a spline sleeve and a sliding bearing. Communication grooves corresponding to the liquid inlet channels are provided on the outer sides of the lower seal body, the spline sleeve and the sliding bearing. The upper and lower stators are respectively in contact with the lower seal body and the sliding bearing. The upper rotor passes downward through the lower seal body, and the lower rotor passes upward through the sliding bearing and is connected thereto. The upper and lower rotors are connected by a spline sleeve. Communication grooves corresponding to the liquid inlet channels are provided on the outer sides of the lower seal body, the spline sleeve and the sliding bearing to ensure the penetration of each liquid inlet channel.

[0057] As Figure 5 (1) As shown, 4 groups of vertical grooves are evenly distributed in the circumferential direction on the outer side of the first stator, which are groove a1, groove b1, groove c1, groove d1, groove a2, groove b2, groove c2 and groove d2 in sequence. Among them, groove a1 and groove a2 are communicated with the inside of the first stator through a plurality of stator inner holes; As Figure 5 (2) As shown, 3 groups of vertical grooves are provided on the outer side of the second stator, which are groove b1, groove c1, groove d1, groove b2, groove c2 and groove d2 in sequence. Groove b1 and groove b2 are communicated with the inside of the second stator through a plurality of stator inner holes; As Figure 5 (3) As shown, 2 groups of vertical grooves are provided on the outer side of the third stator in the circumferential direction, which are groove c1, groove d1, groove c2 and groove d2 in sequence. Groove c1 and groove c2 are communicated with the inside of the third stator through a plurality of stator inner holes; As Figure 5As shown in (4), one set of vertical grooves is provided on the outside of the fourth stator, namely groove d1 and groove d2 in sequence. The two are connected to the inside of the fourth stator through a number of stator inner holes; the groove d1 and groove d2 on the four stators are located on the same straight line in the vertical direction. After being connected, two liquid inlet channels of the fourth stator are formed. By analogy, after all the groove c1 and groove c2 are connected, two liquid inlet channels of the third stator are formed. After all the groove b1 and groove b2 are connected, two liquid inlet channels of the second stator are formed. Groove a1 and groove a2 form two liquid inlet channels of the first stator.

[0058] As Figures 8 - 11 shown, the liquid distribution valve assembly mainly includes an upper valve plate, a lower valve body, an internal spline nut, a pre-tightening spring and a nut. The upper part of the upper valve plate is a diversion structure, the middle part is two symmetric fan-shaped baffle plates, and the lower part is a central shaft. The middle and lower part of the central shaft is a spline, and the end is a thread; the upper end face of the lower valve body is a porous structure. The upper end face of the lower valve body is provided with 8 fan-shaped liquid distribution valve holes evenly distributed along the circumference. As Figure 11 shown, they are hole A1, hole B1, hole C1, hole D1, hole A2, hole B2, hole C2, hole D2 in sequence. At the same time, communication grooves corresponding to the above eight liquid distribution valve holes one by one are evenly distributed on the outside of the lower valve body, and the communication grooves extend downward to the lower end of the lower valve body. The eight liquid distribution valve holes correspond to the eight vertical grooves on the first stator one by one. The liquid distribution valve holes are connected to the corresponding communication grooves to form a flow guiding groove. The flow guiding groove and the corresponding communication groove together form a flow guiding groove. The flow guiding groove is connected to the corresponding vertical groove, so that groove a1 is correspondingly connected to hole A1, groove b1 is correspondingly connected to hole B1, groove c1 is connected to hole C1, groove d1 is correspondingly connected to hole D1, groove a2 is correspondingly connected to hole A2, groove b2 is correspondingly connected to hole B2, groove c2 is connected to hole C2, and groove d2 is correspondingly connected to hole D2. A stepped hole is provided in the center of the lower valve body, and the inner surface is a hard alloy layer. The central shaft of the upper valve plate passes through the central hole and the internal spline nut of the lower valve body. A pre-tightening spring is provided on the central shaft of the upper valve plate, and a nut is used on the central shaft of the upper valve plate. The baffle plate of the upper valve plate is closely attached to the porous upper surface of the lower valve body. When the upper valve plate rotates with the rotor, the two blades can simultaneously seal any group of flow guiding grooves.

[0059] In the above embodiments, during the rotation of the rotor, there is a point where multiple stator inner holes and multiple rotor inner holes correspond to each other one by one and overlap on the same straight line. At this time, the drilling fluid entering the cavity at the stator inner hole directly flows out from the rotor inner hole and enters the inside of the rotor, and no torque is generated on the rotor by the drilling fluid, and this part of the drilling fluid is wasted. At this time, if the corresponding fluid conduction grooves can be sealed, no drilling fluid will enter the liquid inlet passage, and the leakage of this part of the drilling fluid can be avoided. When the drilling fluid drives the motor to rotate, the rotor drives the upper valve plate to rotate together. During the rotation of the two blades on the upper valve plate, each group of fluid conduction grooves is sealed in turn, so as to periodically close each group of fluid conduction grooves of the upper valve plate. Ensure that when the blade seals the upper end opening of a certain group of fluid conduction grooves, at this time, the multiple stator inner holes and multiple rotor inner holes of the corresponding metal motor are exactly overlapped on the same straight line. At this time, the fluid conduction grooves are closed, and the drilling fluid enters other metal motors through other fluid conduction groove holes on the lower valve body, so as to reduce the leakage of the drilling fluid. Taking a 172mm four-stage metal motor as an example, the drilling fluid displacement is 32L / s, and the drilling fluid flow rate allocated to each stage of the metal motor is 8L / s, which is only 1 / 4 of the total flow rate. When the rotational speed output by the power tool is still 200 revolutions per minute, the length of the single-stage rotor is only 750mm, and the output torque is more stable, thus greatly improving the service life of the rotor.

[0060] Preferably, as another embodiment of the present invention, as Figure 12 shown, the torque limiter assembly includes a spline shaft, a spring, an overload actuator, a ball and a threaded shaft. The spline shaft is connected to the lower end of the lowermost rotor. The threaded shaft is tightly connected to the spline shaft through the ball. The spring and the overload actuator are arranged on the spline shaft, and the spring applies a force towards the ball to the overload actuator.

[0061] In the above embodiments, the torque limiter connects the rotor and the transmission shaft, and its main function is overload protection: when the rock burst drill bit gets stuck or there is a mechanical failure, resulting in the required torque exceeding the set value, the steel ball will leave the pit, causing slippage between the driving end component and the driven end component, that is, slippage between the rotor and the core shaft of the transmission shaft assembly. When the overload situation disappears, it will automatically resume connection to avoid damage and loss of equipment parts.

[0062] Preferably, as another embodiment of the present invention, as Figures 13 - 14 shown, the transmission shaft assembly includes a housing and a core shaft. Upper TC outer sleeves and lower TC outer sleeves are respectively provided at the upper and lower openings of the housing. The inside of the core shaft is hollow. It penetrates the housing and is respectively connected to the upper TC outer sleeve and the lower TC outer sleeve through the upper TC inner sleeve and the lower TC inner sleeve. Both ends of the core shaft are respectively connected to the torque limiter assembly and the rock burst drill bit. 18 receiving holes are evenly distributed along the circumferential direction at the lower end of the lower TC outer sleeve, and cylindrical rollers are rotatably arranged in the receiving holes and contact the upper wave surface of the annular drill bit.

[0063] In the above embodiments, the mandrel is hollow inside and is in communication with the inside of the rotor. The drilling fluid inside the rotor flows through the inside of the mandrel and finally enters the rock burst bit. The upper end of the mandrel extends into the torque limiter and is fixed thereto by an upper fixing nut, and its lower end is fixed to the lower TC inner sleeve by a lower fixing nut; end caps are respectively provided at the lower end of the upper TC outer sleeve and the upper end of the lower fixing nut, and a plurality of inner rings and outer rings sleeved on the mandrel are arranged in a vertically staggered manner between the two end caps, and a spacer sleeve is sleeved on the inner ring.

[0064] Preferably, as another embodiment of the present invention, as Figures 14 - 18 shown, the rock burst bit includes an annular bit, a core bit and a water eye nozzle. The annular bit is hollow inside, and its upper end corresponds to the lower end of the upper TC outer sleeve. The core bit is slidably arranged up and down inside the annular bit, its upper end is connected to the lower end of the mandrel, and the water eye nozzle is arranged on the core bit. The annular bit and the core bit are connected by keyway fit. A plurality of strip-shaped grooves are uniformly distributed in the circumferential direction on the inner wall of the annular bit, and splines are slidably arranged in the strip-shaped grooves. The splines are connected to the core bit, so as to realize the connection between the annular bit and the core bit by keyway fit.

[0065] The beneficial effects of adopting the above further solution are as follows: In this further solution, the core bit and the annular bit can slide relatively up and down. The core bit is connected to the core shaft and rotates together during the drilling process. At this time, it drives the annular bit to rotate together. At the same time, a high-frequency reciprocating motion up and down occurs between the annular bit and the core bit. The multiple arc surfaces at the upper end of the annular bit form a wavy surface. During the rotation of the annular bit, the cylindrical rollers at the lower end of the lower TC jacket do not rotate. When the upper end of the annular bit moves upward to contact the multiple cylindrical rollers at the lower end of the lower TC jacket by the wavy surface, controlled by the wavy surface, when the annular bit moves downward, the drilling pressure gradually increases, and at the same time, the core bit moves upward, and the drilling pressure is gradually unloaded to zero; when the annular bit moves upward, the drilling pressure rapidly decreases, and the drilling pressure is gradually unloaded to zero. At the same time, the core bit moves downward, and the drilling pressure gradually increases to the maximum value; during the drilling process, the annular bit and the core bit unload alternately. When the annular bit has the maximum drilling pressure, the drilling pressure of the core bit is zero; when the core bit has the maximum drilling pressure and the annular bit has zero drilling pressure; when the drilling pressure is unloaded and decreased, the rock follows and is rapidly unloaded. When unloading in one direction, the rock undergoes elastic bulging deformation, showing tensile failure. Rocks are not resistant to tension but only to compression, and the tensile strength is only 1 / 8 of the compressive strength, so the rock is easier to break; deep rocks are stressed in three axes and six directions and store a large amount of elastic strain energy. When a single-sided load is suddenly unloaded, after the one-way expansion deformation occurs, the stresses in other directions will also be unloaded successively, accelerating the bulging deformation in the one-way unloading direction, and the rock is instantaneously destroyed by the excess energy, resulting in rock burst, making deep drilling easier. When the drilling pressure is unloaded so that the compression energy of the rock is equal to the tensile failure energy, only failure occurs; when the stress of the rock compression deformation is much greater than the tensile strength and the rock is rapidly unloaded, the rock undergoes tensile deformation, the rock is instantaneously destroyed, and the stored excess elastic strain energy is released, resulting in rock burst, making deep drilling easier.

[0066] The present invention also provides a rock blasting method, which adopts the above-mentioned rock burst drilling tool, and includes the following steps:

[0067] Step 1: Set the output speed of the motor:

[0068] According to the rotor torque strength requirement, set the single-stage rotor length within a certain range; then according to the speed requirement of the rock burst bit, select the number of motor stages, and use the liquid distribution valve assembly to evenly distribute the drilling fluid to each stage of the metal motor, reduce the displacement of each stage of the motor, and reduce the output speed of the power tool to the range required by engineering technology.

[0069] Step 2: Set the parameters of the rock burst bit:

[0070] According to the fact that the shorter the unloading time is, the more rapid the transformation of compressive stress into tensile stress is, and the greater the peak value is; when the bit frequency is close to the natural frequency of the rock, the formation absorbs the most external energy, the alternating unloading frequency of the rock burst bit is set above 40 Hz; and then according to the requirement of the mechanical drilling rate, the penetration of the bit for each unloading is converted, and the amplitude of the reciprocating movement of the annular bit and the core bit up and down is set.

[0071] Step 3. Rock burst drilling operation:

[0072] Lower the rock burst drilling tool to the bottom of the well and connect the bypass valve assembly to the drilling pump;

[0073] Start the drilling pump and inject high-pressure drilling fluid into the rock burst drilling tool. After the drilling fluid passes through the liquid distribution valve assembly, it is evenly distributed into the liquid inlet channels of each metal motor of the metal motor assembly. When the high-pressure drilling fluid enters the cavity between the stator and the rotor through the liquid distribution valve assembly. The large sealing cylinder in the symmetric groove of the stator and the small sealing cylinder in the symmetric groove of the rotor divide the cavity between the stator and the rotor into four chambers, which are the high-pressure chamber, the low-pressure chamber, the high-pressure chamber, and the low-pressure chamber in sequence. One side of the rotor is high-pressure and the other side is low-pressure, generating a torque that causes the rotor to rotate clockwise. The rotor transmits the torque to the core bit through the torque limiter assembly and the core shaft. The core bit transmits the torque to the annular bit through the keyway fit at the bottom of the annular bit, causing the annular bit and the core bit to rotate synchronously. At the same time, during the relative rotational movement of the annular bit with respect to the lower TC outer sleeve, under the control of the wave surface at the upper end of the annular bit, along the axial direction, the annular bit reciprocates up and down relative to the core bit;

[0074] Each metal motor starts to rotate and drives the rock burst bit to rotate through the torque limiter assembly and the drive shaft assembly. After the pump is started normally, record the displacement and pump pressure;

[0075] Step 4. Rock burst rock drilling:

[0076] Further lower the drill string. After the rock burst bit contacts the bottom of the well, gradually apply pressure and adjust to the expected mechanical drilling rate, and record the pump pressure.

[0077] During the drilling process, high-frequency reciprocating movement occurs between the annular bit and the core bit. When controlled by the wave surface and the annular bit moves downward, the drilling pressure gradually increases, and at the same time the core bit moves upward, and the drilling pressure is gradually unloaded to zero; when the annular bit moves upward, the drilling pressure rapidly decreases, the drilling pressure is gradually unloaded to zero, and at the same time the core bit moves downward, and the drilling pressure gradually increases to the maximum value;

[0078] During the drilling process, the annular bit and the core bit are alternately unloaded. When the annular bit has the maximum drilling pressure, the drilling pressure of the core bit is zero; when the core bit has the maximum drilling pressure, the drilling pressure of the annular bit is zero;

[0079] When the WOB (weight on bit) is unloaded and decreases, the rock follows the rapid unloading. When unloaded unidirectionally, the rock undergoes elastic bulging deformation, showing tensile failure. Rocks are resistant to compression but not to tension, and the tensile strength is only 1 / 8 of the compressive strength. Thus, rocks are more prone to fragmentation. Deep rocks are under triaxial and six-directional stress, storing a large amount of elastic strain energy. When a single-sided load is suddenly unloaded, after the unidirectional expansion deformation occurs, the stresses in other directions will also be unloaded successively, accelerating the bulging deformation in the unidirectional unloading direction. The rock is instantaneously damaged by the excess energy, resulting in rockburst, making deep drilling easier.

[0080] When the WOB is unloaded and the compressive energy of the rock equals the tensile failure energy, only failure occurs. When the stress of the rock's compressive deformation is much greater than the tensile strength and the rock is rapidly unloaded, the rock undergoes tensile deformation and instantaneously fails, releasing the stored excess elastic strain energy and resulting in rockburst, making deep drilling easier.

[0081] Taking the rockburst rock-breaking method design at a well depth of 15,000 meters as an example, an 8 1 / 2 rockburst bit is used, with a resonance frequency of 45 Hz, a rock density of 3.0, a mud density of 1.6, and a WOB of 8 tons. That is, when the maximum WOB of the annular bit is 8 tons, the WOB of the core bit is zero; when the maximum WOB of the annular bit is zero, the WOB of the core bit is 8 tons.

[0082] Criterion for generating rockburst rock-breaking: The elastic strain energy released by the rock is greater than the energy required for rock tensile failure, that is:

[0083] ΔE = (∫σ0dε - ∫σ y dε - ∫σ z dε) - ∫σ L dε > 0

[0084] In the formula, ΔE is the energy released by rockburst; σ0 is the elastic strain energy stored in the rock; σ y is the hydraulic energy generated by the drilling fluid; σ z is the pressure energy generated by the bit teeth; σ L is the energy required to overcome rock tensile failure.

[0085] After arrangement, we get:

[0086] σ z < σ0 - σ y - σ L

[0087] According to the design parameters: σ0 = 450 MPa, σ y = 240 MPa, σ L = 30 MPa, substituting into the above formula, we get:

[0088] σ z < 180 (MPa)

[0089] Therefore, when the ring bit moves downward, the drilling pressure gradually increases. At the same time, the core bit moves upward and the drilling pressure is gradually unloaded. When the compressive stress of the formation rock directly below the bit is less than 180 MPa, the rock undergoes stress release and rock burst failure occurs. When the core bit moves downward and the drilling pressure gradually increases to the maximum value while the ring bit moves upward, the drilling pressure rapidly decreases and is unloaded. When the compressive stress of the bit on the formation rock is less than 180 MPa, the rock undergoes stress release and rock burst failure occurs. In short, during the deep drilling process at 15,000 meters, the ring bit and the core bit alternate in unloading, and rock burst is certain to occur. Moreover, the deeper the formation, the more elastic energy the rock stores, the greater the released elastic energy, and the easier the drilling.

[0090] In summary, the present invention has the following advantages:

[0091] 1. The rock burst drilling tool has an all-metal structure, is heat-resistant, has a good rotational speed range, good matching with the rock burst bit, high efficiency, and large torque, and can be used for ten-thousand-meter deep wells and critical geothermal drilling.

[0092] Downhole motor drills need to improve the mechanical drilling rate of the bit on the one hand to reduce the drilling cost, and on the other hand need to be all-metal, heat-resistant, have large torque and long life to complete the ultra-deep well drilling project. In recent decades, there has been no breakthrough development in downhole motor drills. At present, the widely used downhole motor drills are mainly positive displacement motor drills, whose stator is a rubber part and has poor heat resistance, and cannot adapt to the high temperature and high pressure drilling of ultra-deep wells; while turbine drills have low efficiency, high pressure loss, high rotational speed, and there is no suitable PDC bit. Traditional downhole motor drills can no longer adapt to ultra-deep wells and critical geothermal wells in terms of operability, reliability and working environment adaptability. Now there is no available power tool for ten-thousand-meter drilling and critical geothermal drilling.

[0093] 2. Compared with the conventional drilling method, the deeper the well, the higher the elastic energy stored in the formation, the higher the efficiency of the rock burst rock breaking method, and the mechanical drilling rate is significantly improved, thus greatly reducing the drilling cost of ten-thousand-meter wells.

[0094] Obtaining supercritical geothermal energy at low cost is the key to realizing the large-scale application of carbon-free energy. The deeper the well, the higher the cost of the drilling project. Efficient rock breaking technology is one of the important factors to improve the rock breaking efficiency, reduce the drilling time and safely and quickly reduce the drilling cost; conventional drilling practice shows that if the drilling efficiency is doubled, the total drilling cost can be reduced by about 1 / 4. The quality of the rock breaking efficiency directly determines the drilling speed and cost, and more importantly, the economic benefits of the drilling project. Improving the drilling efficiency is the best way to reduce the exploration and development cost.

[0095] For conventional rock-breaking methods in drilling, the deeper the well, the more difficult the drilling becomes. As the well depth increases, the rocks in deep formations become harder and more plastic, resulting in poor drillability of the formations. During the drilling process in hard and brittle formations, stick-slip phenomena are more severe, accelerating bit wear and even causing bit teeth to break. Additionally, the higher the formation temperature, the significantly lower the bit hardness, the poorer the bit wear resistance, and the significantly shorter the bit life. The wellbore structure dimensions of ultra-deep wells are larger, the drilling efficiency is lower, and the rate of penetration is slow. The problem of well deviation in deep wells is also becoming increasingly prominent. The deeper the well, the more difficult it is to drill, severely restricting the exploration and development process.

[0096] Rockburst is a common dynamic failure phenomenon in the construction of deep underground engineering. Rockburst often causes severe damage to the excavation face, equipment damage, and casualties, and has become a worldwide problem in the fields of rock underground engineering and rock mechanics.

[0097] A large number of practices have shown that whether it is granite, sandstone, or shale, when the burial depth reaches certain conditions, sufficient elastic strain energy is stored in the rock mass, and rockburst is likely to occur. For different projects, the conditions for rockburst occurrence are different, mainly because the strengths of different rocks are different. Additionally, the overlying strata vary greatly, and the in-situ stress distributions at the same burial depth are different. Due to the different strengths of different rocks, the critical depths for rockburst occurrence are different.

[0098] The mechanical mechanism of rockburst is extremely complex, and the relevant research in the theory of rockburst mostly remains at the stage of hypotheses and experience. Currently, most research focuses on the study of the deep in-situ stress field, the physical and mechanical properties of deep rock masses and their constitutive relations, the prediction and forecasting theories and methods of rockburst incubation mechanisms and their tendencies, and the control and support methods of rock strata under high stress, etc.

[0099] Currently, this failure process is still not well understood, which is a challenging problem faced by rock mechanics researchers. It is even difficult to reach a consensus on the definition of rockburst. Currently, many research centers around the world are conducting research to explain rockburst problems, and its progress will represent the development and major breakthrough of this discipline of rock mechanics.

[0100] Inducing conditions of rockburst: Conditions for rockburst occurrence:

[0101] (1) Internal factors: A large amount of elastic strain energy is stored in the rock mass;

[0102] Considering three factors: the elastic deformation energy E stored in the rock mass, the drilling depth h, and the compressive strength σ of the rock, a formula for the strain energy stored in the rock is established. It can be seen that different rock compressive strengths and burial depths result in different stored elastic strain energies.

[0103] (2) There must be an external inducing factor for rockburst to occur, such as the induction of certain additional loads.

[0104] During the air drilling process, it is typically a process of continuously inducing rock bursts: The drill bit opens a new rock formation. With a low air density, the rock directly beneath the drill bit suddenly undergoes unidirectional unloading, releasing elastic strain energy, making it easier for the drill bit to break the rock and resulting in a high mechanical drilling rate. Air drilling is 3 - 10 times faster than conventional drilling machinery, but air drilling is only applicable to shallow formations that do not produce water and do not contain hydrogen sulfide, and it cannot be widely applied, let alone used for drilling at a depth of 10,000 meters.

[0105] The rock burst rock breaking method refers to the process of drilling in medium - deep formations. When sufficient elastic strain energy is stored in the rock mass, through a rock burst drilling tool, resonance is induced in a local area of the rock beneath the drill bit, causing the in - situ stress near the drill bit to undergo periodic unloading. When unloading and rebounding, tensile forces are formed, inducing the rock to release energy and undergo rock bursts. The rock strength rapidly decreases, thereby improving the rock breaking efficiency and making drilling at a depth of 10,000 meters easier. It is a new method that is expected to significantly increase the mechanical drilling rate.

[0106] The rock breaking principle of rock burst drilling is as follows: During the drilling process, the drilling fluid drives the rock burst power tool, enabling high - frequency reciprocating up - and - down motion between the annular drill bit and the core drill bit. When the core drill bit moves downward, the drilling pressure gradually increases, while the annular drill bit moves upward and the drilling pressure gradually unloads to zero; when the core drill bit moves upward, the drilling pressure rapidly decreases, the rock rapidly unloads, and bulging deformation occurs. Since the tensile strength is only 1 / 8 of the compressive strength, these bulging areas rapidly release the stored elastic strain energy. When the compressive energy is equal to the tensile failure energy, only failure occurs; when the compressive energy is greater than the tensile failure energy. For example, when the compressive stress is between the tensile strength and the compressive strength, and the stress of the compressive deformation is much greater than the tensile strength, when the rock rapidly unloads, the rock undergoes tensile deformation and instantaneously fails, releasing the excess stored elastic strain energy and resulting in a rock burst. If the energy stored in the rock mass is large enough, but the unloading of the drilling pressure is insufficient and cannot reach the critical condition for inducing a rock burst, the rock mass will not undergo a rock burst. Only when the unidirectional unloading is sufficient and the released energy is greater than the tensile failure energy will the rock mass undergo a rock burst.

[0107] Rock bursts experience a stress evolution process: Under triaxial six - direction stress, elastic strain energy is stored. When unidirectional unloading occurs, the rock undergoes elastic bulging deformation, manifested as tensile failure. The rock resists compression but not tension. When enough energy is released, the tensile stress in the rock is much greater than the tensile failure strength, and the rock undergoes bursting failure.

[0108] Furthermore, under the triaxial six - face stress state, when σ1 suddenly undergoes unidirectional unloading, assuming that the other two - direction stresses σ2 and σ3 remain unchanged, expansion deformation occurs in the σ1 direction; at this time, the stresses in the three directions are unbalanced, and subsequently, the other two - direction stresses σ2 and σ3 will unload successively, causing a certain degree of recovery in σ1 and accelerating the bulging deformation in the σ1 direction; then the above - mentioned unloading process starts to repeat until the elastic strain of the rock in the three directions is completely released and a rock burst occurs.

[0109] According to the theory of rock burst in rock blasting, contrary to the conventional drilling method, during the drilling process, as the drilling depth increases, the elastic strain energy stored in the formation is higher, it is easier to induce rock burst in the rock, the greater the elastic energy released, the more violent the rock burst phenomenon, the easier the drilling, the higher the mechanical drilling rate, and the lower the drilling cost.

[0110] In short, the critical geothermal drilling and production cost must be significantly reduced to have a practical resource with the same economic value as fossil energy.

[0111] 3. Rock burst drilling tools and rock blasting methods for rock breaking promote the energy revolution and change the world economic and political pattern.

[0112] In September 2005, the US Department of Energy established an 18-member assessment team to conduct a detailed assessment of the deep geothermal development system and the corresponding key technologies and economic feasibility, and believed that "whoever solves the economic problem of deep geothermal exploitation will gain the upper hand in carbon-free energy and affect the world energy and economic pattern."

[0113] Rock burst drilling tools and rock blasting methods for rock breaking are the key technologies to realize critical geothermal development. It is expected to achieve low-cost drilling and production of critical geothermal within 3 to 5 years, providing rich and stable carbon-free energy for coal-fired thermal power plants, etc.

[0114] The development of critical geothermal has strategic significance and completely subverts the energy pattern. The era of fossil energy will soon pass. The energy that renewable energy such as hydropower, solar energy, and wind energy can provide for humans will be extremely limited and difficult to replace the gap left by fossil energy. The large-scale use of nuclear energy will also be restricted in various ways. In the future, the critical geothermal energy deep in the earth's ten-thousand-meter depth is a renewable energy source that is clean, carbon-free, rich, extensive, safe, high-quality, and has high power generation efficiency. It is expected to become the main source of the basic load power generation capacity in China by 2050 and is the correct direction to solve the long-term future energy needs of mankind.

[0115] (1) The reserves of critical geothermal resources are very rich and extensive.

[0116] According to calculations, the temperature in the deep part of the Earth at a depth of 15,000 to 25,000 meters generally exceeds 374°C and even reaches 700°C. Based on the calculated results of the deep temperature in the land area of our country, the volume method is adopted to estimate the dry hot rock resource reserves in the land area of our country in relevant GIS software. Calculate the dry hot rock resource potential at a depth of 10 km. The results are shown in Table 2. For the dry hot rock reserves and their distribution areas at a depth of 10,000 meters in the land area of our country, it can be seen from the figure that there are huge dry hot rock reserves only between a depth of 9 - 10 km with a temperature ranging from 150°C to 350°C, approximately 5.3×10²⁴ J. Even if only 2% of its reserves are developed, 1.06×10²³ J of thermal energy will be obtained. It can be estimated that the total dry hot rock resources at a depth of 10.0 - 20.0 km in the inland area of our country are 5.3×10²⁵ J, equivalent to 180×10⁵ million tons of standard coal. According to the plan, the total energy consumption in our country in 2025 is 4.6 billion tons of standard coal. Calculated according to 2% of the exploitable resource volume, it is equivalent to 390,000 times the total energy consumption planned in our country in 2025.

[0117] (2) High energy utilization coefficient and power generation efficiency

[0118] Critical geothermal energy is the thermal energy buried deep at a depth of 10,000 meters, which is relatively stable and not easily affected by time and climate changes. The energy utilization coefficient (or capacity factor) of geothermal energy is above 0.70, about 5 times that of photovoltaic power generation, 4 times that of wind power generation, and 1.5 times that of biomass power generation. Compared with wind power and photovoltaic power generation technologies, the energy utilization coefficient of geothermal power generation technology is high. Critical geothermal energy directly provides critical state water for the generator set, and the power generation efficiency is high.

[0119] (3) Carbon-free energy power generation, with little environmental impact

[0120] Almost no pollution to the environment is caused during the process of geothermal power generation, and it is more competitive compared to technologies such as hydroelectric power generation and thermal power generation. When the pressure pump pumps water into the dry hot rock reservoir tens of thousands of meters deep underground, the formation temperature is close to 500°C, and the water will be heated and pressurized in the casing container to reach the critical state, and then be transported through pipelines to the ground heat exchanger to drive the steam turbine generator to convert thermal energy into electric energy. The hot water extracted by pipeline pressurization can be input underground for heat exchange again after doing work. The geothermal power generation system at a depth of 10,000 meters does not produce industrial wastewater and waste gas generated during thermal power generation. It is a truly carbon-free energy source, which can reduce greenhouse gas emissions and improve the ecological environment. Therefore, it is expected that the critical geothermal energy power generation at a depth of 10,000 meters in China will develop rapidly in the future, becoming an important force in optimizing the energy structure, coping with climate change, and winning the battle to defend the blue sky, and making greater contributions to high-quality green development and ecological civilization construction.

[0121] (4) The energy security of our country will be completely solved, and clean energy can be obtained more conveniently and at low cost for various demand sides in our country; it will no longer be threatened by the security of international energy transportation lines;

[0122] Energy security has entered a critical period, and low-carbon transformation has entered an important window period. The 10,000-meter critical geothermal energy can be used as a baseload energy source, which is stable and flexible in operation and can provide a series of basic services to ensure the stability and flexibility of the national power grid.

[0123] (5) Comprehensively enhance my country’s international competitiveness and influence the international economic and political landscape.

[0124] Critical geothermal power generation does not require fuel in the later stage, and the daily maintenance cost is low. It is expected to significantly reduce the production and living costs of power generation, industry, transportation and life, thereby systematically improving my country's industrial competitiveness in the world. When conditions are ripe, it can provide carbon-free energy and carbon-free energy services to friendly neighboring countries around my country, which will not only increase international trade and promote economic prosperity, but also increase friendly exchanges with my country, creating a more friendly external environment for my country's development.

[0125] In short, global climate governance is entering a new phase, and the energy system and development model are entering a new stage dominated by non-fossil energy.

[0126] The embodiment of the present invention also provides another rock burst drilling tool, such as Figure 19 As shown, it includes a bypass valve assembly, a screw motor assembly, a universal shaft assembly, a transmission shaft assembly and a rock burst drill bit which are sequentially connected from top to bottom.

[0127] The beneficial effect of adopting the above further scheme is: in this further scheme, a screw motor assembly and a universal shaft assembly are used to replace the metal motor assembly and the torque limiter assembly, and the existing screw motor assembly is used as a power source to drive the rockburst drill bit to rotate, which is mainly used for speeding up conventional drilling at temperatures below 150°C.

[0128] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A rock burst drilling tool, characterized in that, It includes a bypass valve assembly, a metal motor assembly, a drive shaft assembly, and a rock burst bit arranged sequentially from top to bottom. The metal motor assembly includes a housing. The bypass valve assembly is connected to the upper end of the housing. Inside the housing, N metal motors with rotors connected in series are arranged sequentially from top to bottom, where N≥3. A liquid distribution valve assembly connected to the first metal motor is provided inside the housing. There is a liquid inlet channel between each metal motor and the housing. The liquid distribution valve assembly evenly distributes the drilling fluid to each metal motor. The Nth metal motor is connected to the drive shaft assembly through a torque limiter assembly, and the rock burst bit is connected to the drive shaft assembly; Among them, the metal motor includes a stator and a rotor. Two adjacent stators are hermetically connected. The rotor is coaxially arranged inside the stator and there is a cavity between them. Upper and lower seals corresponding to the cavity are provided at the upper and lower ends of the rotor respectively. Two stator symmetric holes are provided on the inner side of the stator. A large sealing cylinder is vertically provided in the stator symmetric hole. Two rotor symmetric holes are provided on the outer side of the rotor. A small sealing cylinder is vertically provided in the rotor symmetric hole. The large sealing cylinder and the small sealing cylinder divide the cavity into two independent high-pressure chambers and two low-pressure chambers. The stator symmetric holes and rotor symmetric holes of each metal motor are arranged circumferentially staggered. N groups of vertical grooves are evenly distributed circumferentially on the outer side of the first stator. Each group of vertical grooves includes two oppositely arranged vertical grooves. The outer side of the ith stator is provided with N-(i-1) groups of vertical grooves, where i is a positive integer between 2 and N. There is a vertical groove communicating with it above any vertical groove, so as to form N liquid inlet channels between the housing and the multiple stators. Multiple stator inner holes are vertically and evenly distributed on the inner wall of the vertical groove at the bottom of each liquid inlet channel. The rotor is hollow inside, and it is provided with multiple rotor inner holes equal in number to and corresponding one by one with the stator inner holes.

2. The rock burst drilling tool according to claim 1, wherein A spline sleeve and a sliding bearing are sequentially provided at the lower end of the lower seal. Communication grooves corresponding to the liquid inlet channels are provided on the outer sides of the lower seal body, the spline sleeve, and the sliding bearing. The upper and lower stators are in contact with the lower seal body and the sliding bearing respectively. The upper rotor passes downward through the lower seal body, and the lower rotor passes upward through the sliding bearing and is connected to it. The upper and lower rotors are connected through the spline sleeve.

3. A rock burst drilling tool as claimed in claim 1, wherein, The liquid distribution valve assembly includes an upper valve plate and a lower valve body. The lower valve body is connected to the stator of the first metal motor. A stepped hole is coaxially provided on the lower valve body. The rotor of the first metal motor extends upward into the stepped hole and is rotatably fitted with the lower valve body. 2N vertically penetrating guide flow grooves are evenly distributed circumferentially on the lower valve body. Two opposite guide flow grooves form a group. The N groups of guide flow grooves correspond one by one to the N groups of vertical grooves on the outer side of the first stator. A retaining piece is provided on the upper valve plate. The lower end of the upper valve plate extends into the stepped hole and is connected to the rotor of the first metal motor. The retaining piece is slidably fitted with the upper end of the lower valve body. When the upper valve plate rotates with the rotor, the two blades can simultaneously block any group of guide flow grooves.

4. A rock burst drilling tool according to claim 3, characterized in that, An internal spline nut, a pre-tightening spring, and a nut are provided in the stepped hole. The internal spline nut is connected to the rotor of the first metal motor. The upper valve plate slidably penetrates through the internal spline nut. The nut is provided at the lower end of the upper valve plate. The pre-tightening spring is sleeved on the upper valve plate, and its two ends are respectively in contact with the internal spline nut and the nut.

5. The rock burst drilling tool according to claim 1, wherein, The torque limiter assembly includes a spline shaft, a spring, an overload actuator, a ball, and a threaded shaft. The spline shaft is connected to the lower end of the Nth rotor. The threaded shaft is tightly connected to the spline shaft through the ball. The spring and the overload actuator are arranged on the spline shaft, and the spring applies a force towards the ball to the overload actuator.

6. The rockburst drilling tool according to claim 1, characterized in that, The drive shaft assembly includes a housing and a core shaft. Upper and lower TC outer sleeves are respectively provided at the openings at the upper and lower ends of the housing. The core shaft is hollow inside, passes through the housing, and is connected to the upper and lower TC outer sleeves through an upper TC inner sleeve and a lower TC inner sleeve respectively. Both ends of the core shaft are respectively connected to the torque limiter assembly and the rock burst drill bit. A plurality of receiving holes are evenly distributed in the circumferential direction at the lower end of the lower TC outer sleeve, and cylindrical rollers are rotatably arranged in the receiving holes.

7. The rock burst drilling tool according to claim 6, wherein, The rock burst drill bit includes an annular drill bit, a core drill bit, and a water eye nozzle. The annular drill bit is hollow inside, and its upper end corresponds to the lower end of the lower TC outer sleeve. An arc surface corresponding to the plurality of cylindrical rollers is provided at the upper end of the annular drill bit. The core drill bit is slidably arranged up and down in the annular drill bit, and its upper end is connected to the lower end of the core shaft. The water eye nozzle is arranged on the core drill bit.

8. A method for blasting rock, characterized in that, It includes the following steps: S1. Lower the rock burst drilling tool according to any one of claims 1-7 to the bottom of the well, and connect the bypass valve assembly to the drilling pump. S2. Start the drilling pump, inject high-pressure drilling fluid into the rock burst drilling tool, and the rock burst drilling tool starts to work. Rock breaking operation is carried out by the rotation of the rock burst drill bit at its lower end. When the rock burst drill bit rotates, the annular drill bit on it makes high-frequency up and down reciprocating movements relative to the core drill bit: when the annular drill bit moves downward relative to the core drill bit, the drilling pressure of the annular drill bit gradually increases, and the drilling pressure of the core drill bit gradually decreases. When the drilling pressure of the annular drill bit is at its maximum value, the drilling pressure of the core drill bit is zero; when the annular drill bit moves upward relative to the core drill bit, the drilling pressure of the annular drill bit gradually decreases, and the drilling pressure of the core drill bit gradually increases. When the drilling pressure of the annular drill bit is zero, the drilling pressure of the core drill bit is at its maximum value. After the pump is running normally, record the displacement and pump pressure. S3. Further lower the drill string. After the rock burst drill bit contacts the bottom of the well, gradually apply pressure and adjust to the expected rate of penetration, and record the pump pressure.

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