High-confining-pressure visual PDC drill bit rock breaking experiment device and method

Abstract

The invention discloses a high confining pressure visual PDC drill bit rock breaking experiment device and method.The device comprises an environment system, a support system and a rock cutting system, the support system is used for supporting the rock cutting system, and the environment system is used for providing drilling fluid and drilling pressure for the rock cutting system; the rock cutting system comprises a high-pressure sealing cavity and a drill column system, the high-pressure sealing cavity (7) is of a cylinder structure with a hollow hole, the high-pressure sealing cavity is sleeved with a rock peeping device which can move along the peripheral face of the high-pressure sealing cavity and is provided with an annular inner hole, and the rock peeping device and the high-pressure sealing cavity are kept in sliding sealing; a through hole is formed between the wall face of the rock peeping device and the annular inner hole of the rock peeping device to serve as an observation window, and sealing glass is arranged on the observation window. A corresponding method is provided, the confining pressure borne by a rock sample under a deep stratum can be simulated, and the effect of a rock breaking experiment is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas development, in particular to the technical field of drilling experiment, and specifically relates to a high confining pressure visual PDC drill bit rock breaking experiment device and method. BACKGROUND

[0002] As an indispensable raw material and fuel for modern life, the demand for oil and natural gas is increasing year by year. In order to meet the global demand for oil and natural gas, it is necessary to improve the exploration and development efficiency and reduce the input cost. With the gradual progress of drilling in China to deep / ultra-deep layers, the problems of high rock hardness, poor rock drillability, high pressure and high temperature of rock are becoming more and more serious. In order to explore the cutting conditions of deep / ultra-deep rock and further research more suitable drilling tools and drilling speed increasing devices, an experiment device capable of simulating the rock breaking conditions of deep / ultra-deep layers is needed. In recent years, many rock breaking experiment devices under triaxial pressure have appeared on the market, but most of these devices are fully enclosed structures, which cannot directly observe the rock cutting conditions in the experiment. Moreover, the structure of these triaxial pressure devices is complex, the cost is high, and the experiment time is long. Therefore, finding a structure that can be more convenient to observe and install will have great significance to improve the experiment effect. SUMMARY

[0003] In view of the above problems, the present application provides a high confining pressure visual PDC drill bit rock breaking experiment device and method, which can simulate the confining pressure of rock samples in deep formations, directly observe the rock breaking conditions of the drill bit in the drilling process, and facilitate the improvement of the rock breaking experiment effect.

[0004] A high confining pressure visual PDC drill bit rock breaking experiment device, comprising an environment system, a support system and a rock cutting system, the support system is used for supporting the rock cutting system, the environment system is used for providing drilling fluid and drilling pressure for the rock cutting system, the rock cutting system comprises a high-pressure sealing cavity and a drill string system, the high-pressure sealing cavity is a cylindrical structure with a hollow hole, a section of radially penetrating structure is arranged in the middle of the high-pressure sealing cavity as a sealing cavity, a rock viewing device with an annular inner hole is arranged outside the high-pressure sealing cavity and can move along the outer peripheral surface of the high-pressure sealing cavity, and the rock viewing device and the high-pressure sealing cavity are in sliding sealing, cavity sealing rings are arranged on the outer peripheral surface of the high-pressure sealing cavity above and below the corresponding sealing cavity, and the cavity sealing rings are used for realizing sealing with the externally sleeved rock viewing device; a through hole is arranged between the wall surface of the rock viewing device and the annular inner hole as an observation window, and a sealing glass is arranged on the observation window.

[0005] Further, the environment system comprises a plurality of drilling fluid pipes, an intermediate container, a back pressure device, a drilling fluid pool and a drilling fluid pump connected by the drilling fluid pipes, a static liquid pressure sensor is arranged in the intermediate container; and the environment system further comprises a gas pump group composed of a drilling pressure gas pump and a back drilling gas pump.

[0006] Further, the support system comprises a test bench bottom plate, two corresponding test bench side plates are arranged on the sides of the test bench bottom plate, a test bench top plate is arranged on the top of the test bench side plates, and a drill string working plate and a reducer mounting plate are arranged on the upper side and the lower side of the middle part of the test bench side plates respectively.

[0007] Further, the high-pressure sealing cavity and the rock viewing device are installed between the drill string working plate and the reducer mounting plate, a longitudinal through hole is arranged in the middle of the reducer mounting plate, a rotary drive mechanism is arranged below the reducer mounting plate, the rotary drive mechanism comprises a reducer and a servo motor, the reducer is fixed below the reducer mounting plate through reducer mounting studs, and the servo motor is connected with the reducer; a rock sample clamping device is arranged on the drive mechanism and passes through the longitudinal through hole of the reducer mounting plate, the rock sample clamping device is used for fixing a rock sample, and the rock sample clamping device comprises a rock sample clamping body, the upper part of the rock sample clamping body extends into the high-pressure sealing cavity, and the top part of the rock sample clamping body is larger in size than other parts; the bottom part of the high-pressure sealing cavity is mounted on the upper part of the reducer mounting plate; a deep groove ball bearing, a sealing gasket and a high-pressure sealing ring are arranged at the position where the middle part of the rock sample clamping body is in contact with the top part of the reducer mounting plate, the deep groove ball bearing is fixed through a bearing limiting device, a thrust ball bearing and a clamping body rubber ring are arranged at the position where the lower side of the top part of the rock sample clamping body is in contact with the high-pressure sealing cavity, and a component that is connected with the rotary drive mechanism is arranged at the bottom part of the rock sample clamping body, the rock sample clamping body is connected and driven to rotate through the rotary drive mechanism, and the rock sample placed in the rock sample clamping body is driven to rotate.

[0008] Further, a drill string self-balancing device is arranged above the drill string system, the drill string self-balancing device is provided with a balance cavity for being connected to the test bench top plate, a counterforce rod, a dynamic sealing ring group and a sealing disc; the inside of the balance cavity is a hollow structure, the sealing disc is connected to the bottom part of the balance cavity through cavity body sealing bolts, the counterforce rod extends into the balance cavity through the middle part of the sealing disc, and the inside of the balance cavity is sealed through the dynamic sealing ring group.

[0009] The drill string system comprises a torque sensor, a sensor connecting disc and a drill string, a buoyancy plate is connected to the top of the torque sensor through sensor upper mounting bolts, the sensor connecting disc is connected to the bottom of the torque sensor through sensor mounting bolts, the sensor connecting disc is connected to the drill string through threads, and a PDC cutter is arranged at the bottom of the drill string.

[0010] A mounting thread hole is formed in the middle of the buoyancy plate, the buoyancy plate is connected to the sensor through bolts, and through holes are formed at both ends of the buoyancy plate, the through holes are connected to linear bearings and guide rods.

[0011] A counterforce rod connecting hole is formed in the counterforce rod, the counterforce rod is connected to the torque sensor through bolts, and the drill string system can be fixed below the drill string self-balancing device.

[0012] Further, the drill string workboard includes a drill string workboard body, a longitudinal through hole is arranged on the drill string workboard body, the drill string passes through the through hole of the drill string workboard and contacts the rock sample; a drilling pressure gas hole and a reaming gas hole connected to the through hole are further arranged on the drill string workboard body, a piston section is arranged in the middle of the drill string, the connection positions of the drilling pressure gas hole and the reaming gas hole with the through hole are located on the upper and lower sides of the piston section respectively, the drilling pressure gas hole and the reaming gas hole are connected to a drilling pressure gas pump and a reaming gas pump respectively, so as to realize the drilling pressure adjustment of the drill string; a step of an expanded hole below is arranged in the through hole of the drill string workboard body, the drill string is provided with a step matched with the through hole of the drill string workboard body, and an upper rubber ring is arranged on the step of the drill string; a drill string upper sealing ring is arranged at a position higher than the drilling pressure gas hole, and a sealing body is arranged at a position lower than the reaming gas hole, the sealing body is fixed through a sealing body fixing body, and a sealing ring group is arranged below the sealing body fixing body; a PDC cutter is threadedly connected to the bottom of the drill string;

[0013] The PDC cutter is a sandglass-shaped structure, a PDC pressing sheet is arranged on the side surface of the PDC cutter through pressing disc bolts, pressing disc nuts and gaskets, and the bottom of the PDC cutting tooth below the PDC pressing sheet protrudes downward relative to the PDC cutter;

[0014] A high-pressure inner sealing ring, a high-pressure outer sealing ring, a high-pressure outer rubber ring and a high-pressure inner rubber ring are arranged on the sealing ring group.

[0015] Further, at least two guide rod fixators are arranged above the top plate of the experimental bench, a guide rod is arranged above the rock peeping device, and the guide rod is connected into the guide rod fixator and moves up and down through the guide rod;

[0016] The guide rod fixator is hollow inside, an opening is arranged below, a longitudinal through hole is arranged on the experimental bench top plate corresponding to the opening, a protruding end with a guide rod rubber ring is arranged on the top of the guide rod, the protruding end is attached to the inner wall of the guide rod fixator to realize the up-and-down sealing of the guide rod fixator, and a guide rod thread is arranged on the lower end of the guide rod to connect the rock peeping device;

[0017] An overflow valve is arranged below the guide rod fixator, and then connected to a gas pump through a gas pipe, so as to realize the up-and-down movement of the guide rod through suction and injection, and then drive the rock peeping device to move to the required height;

[0018] The rock peeping device is a hollow column structure, a high-pressure sealing cavity is arranged inside, a window is arranged on the surface to pass through the center of the device, and the cutting condition can be clearly observed through the installation of the acrylic glass on the window.

[0019] Further, the two side plates of the experimental bench are provided with drilling fluid pipe through holes, the drilling fluid pump is connected to the top of the balance cavity and one drilling fluid pipe through hole through a drilling fluid pipe, and the other drilling fluid pipe through hole is connected to the intermediate container; the other end of the drilling fluid pipe through hole connected to the drilling fluid pump is connected to the drilling fluid path arranged on the side of the sealing cavity through another drilling fluid pipe, so that the drilling fluid is delivered into the sealing cavity.

[0020] Further, the top of the rock sample clamping body is provided with a rectangular cavity as a rock sample clamping cavity for accommodating the rock sample, half-circular grooves are arranged on two adjacent side surfaces of the rock sample clamping cavity, lock pressing plate mounting bolt holes are arranged in the wall surfaces of the rock sample clamping cavity on both sides of the half-circular grooves, and a matching rock pressing plate is further arranged, the number of which is not less than two, two rock pressing plates are placed, the rock sample is fixed on the front surface of the rock pressing plate, a single inclined surface locking column is inserted into the half-circular groove to press the rock pressing plate and compress the rock sample, and one locking pressing plate is covered on the top to fix the rock pressing plate downward, the locking pressing plate mounting bolt hole is inserted into the pressing plate fixing bolt, and the pressing plate fixing bolt is used to fix the locking pressing plate.

[0021] A matching rock debris collecting blanket is further arranged to be laid in the rock sample clamping cavity.

[0022] The rock debris collecting blanket is a racetrack shape, a rectangular through hole with a side length of 100 mm*100 mm is arranged in the center, and a racetrack hole is arranged on one adjacent side of the rectangular hole for passing through the locking pressing plate, and the device is used to collect the flying rock debris when the rock sample is cut.

[0023] A visual experimental method for rock cutting under confining pressure based on the above device, comprising the following steps:

[0024] Step 1, before testing, if the rock viewing device blocks the sealing cavity, the rock viewing device is lowered to expose the sealing cavity, the pressing plate fixing bolt on the single inclined surface locking column, the single inclined surface locking column, the locking column pressing plate and the rock pressing plate are sequentially removed, the inside is cleaned, the rock sample is placed in the appropriate position of the rock sample clamping body, the lower surface of the rock sample is close to the rock sample clamping body, the two side surfaces are close to the inner surface of the rock sample clamping body, then the previous locking pressing plate, single inclined surface locking column and rock pressing plate are restored to the original state, that is, the rock pressing plate is close to the side surface of the rock sample, the inclined surface of the single inclined surface locking column is in contact with the inclined surface of the rock pressing plate, the two through holes of the locking pressing plate are aligned with the corresponding threaded holes on the rock sample clamping body, and the pressing plate fixing bolt is installed, the same measures are taken for the other locking part, and then the rock viewing device is restored to the position that the viewing window is opposite to the PDC cutting tooth, and the rock debris collecting blanket is installed.

[0025] Step 2, the opening of the drilling fluid path on the high-pressure sealed cavity is connected with the corresponding drilling fluid pipe, the drilling fluid pipe installed on the threaded hole of the drill string balancing device is connected with the corresponding drilling fluid pipe, the drilling fluid pressure pump is opened to inject the drilling fluid, and the rock sample is subjected to a certain hydraulic pressure, so that the pressure borne by the drill string system reaches a balanced state;

[0026] Step 3, the drilling pressure gas hole on the drill string working plate is connected with the corresponding gas pipe, the drilling pressure gas pump is opened to make the drill string system drill down, and the PDC cutting tooth contacts the upper surface of the rock sample;

[0027] Step 4, the servo motor is started, so that the rock sample clamping body rotates, the air pressure of the drilling pressure gas pump is increased to a set value, the PDC cutting tooth is pre-scraped to a certain extent on the rock sample, and the servo motor is closed after the PDC cutting tooth contacts the surface of the rock sample to a certain area;

[0028] Step 5, the back pressure device is started and the pressure value is preset;

[0029] Step 6, after the static liquid pressure sensor of the intermediate container reaches the target value, the rock sample is subjected to the experimental confining pressure, the servo motor is started, the torque of the drill string is observed in real time through the data collector connected with the torque sensor, the drill string is drilled to the predetermined depth after the servo motor is closed, and the drill string system is raised to the initial height through the drill string working plate, and the gas pump is closed;

[0030] Step 7, after the drill string system is raised to the initial height, the pressure value of the back pressure device is slowly returned to zero;

[0031] Step 8, when the static liquid pressure sensor of the intermediate container displays zero, the hydraulic pump is closed to eliminate the pressure of the rock sample 22;

[0032] Step 9, the rock viewing device is lowered to the lowest position, and the rock debris collecting blanket is used to collect the rock debris;

[0033] Step 10, if a new round of experiment is needed, steps 1-9 can be repeated.

[0034] The beneficial effects of the present application are:

[0035] 1, the present application can truly simulate the confining pressure of the rock sample in the drilling process, and the mechanical drilling speed and drilling pressure of the PDC cutting tooth during rock breaking can be conveniently adjusted during the experiment, and the torque borne by the drill string during the drilling process can be monitored in real time; the existing true triaxial experimental device often adopts a rotary torque sensor relying on the rotation of the drill string, the present application adopts a static torque sensor relying on the rotation of the rock sample, the static torque sensor is stable, has high precision, low cost and is convenient to install;

[0036] 2. This invention uses a drill string balancing device to balance the pressure at the upper and lower ends of the drill string system, suppressing the axial runout of the drill string, making the experimental process more realistic, and improving the safety and success rate of the experiment.

[0037] 3. The device of the present invention can directly observe the condition of rock samples under the influence of confining pressure during PDC cutting. The observation effect is achieved through the observation window of the rock viewing device. The position design of the observation window is combined with the position of the PDC cutting teeth on the cutter head to facilitate observation.

[0038] 4. The upper end of the rock viewing device is threaded to the guide rod. The vertical position is changed by moving the guide rod vertically so that the observation window is directly facing the PDC cutting rock sample, making it easy to observe the state during cutting. Attached Figure Description

[0039] The present invention will now be described in further detail with reference to the accompanying drawings.

[0040] Figure 1 This is a schematic diagram of a visual experimental setup used for rock cutting under confining pressure.

[0041] Figure 2 Left view of the experimental setup;

[0042] Figure 3 for Figure 2 Cross-sectional view of section AA;

[0043] Figure 4 for Figure 3 A magnified view of the area circled above;

[0044] Figure 5 for Figure 3 A magnified view of the center circle;

[0045] Figure 6 This is a schematic diagram of the locking pressure plate structure;

[0046] Figure 7 A schematic diagram of the structure of the rock debris collection blanket;

[0047] Figure 8 for Figure 3 A magnified view of the lower circle;

[0048] Figure 9 for Figure 2 Schematic diagram of the cross-sectional structure of the middle BB section;

[0049] Figure 10 This is a schematic diagram of the drill string system assembly structure;

[0050] Figure 11 This is a schematic diagram of the assembly structure of the cutting tool section in a drill string system;

[0051] Figure 12 Fig. 2 is a cross-sectional view of the sensor connection plate;

[0052] Figure 13 Fig. 3 is a cross-sectional view of the sealing ring set;

[0053] Figure 14 Fig. 4 is a partial cross-sectional view of the guide rod and guide rod holder assembly structure;

[0054] Figure 15 Fig. 5 is a bottom view of the guide rod holder sealing plate;

[0055] Figure 16 Fig. 6 is a semi-cross-sectional view of the drill string self-balancing device;

[0056] Figure 17 Fig. 7 is a cross-sectional view of the high-pressure sealing cavity structure;

[0057] Figure 18 Fig. 8 is a structural view of the rock sample clamping body;

[0058] Figure 19 Fig. 9 is a structural view of the rock sample clamping body assembly after installing the rock sample;

[0059] Figure 20 Fig. 10 is a structural view of the experimental bench top plate;

[0060] Figure 21 Fig. 11 is a structural view of the experimental bench side plate;

[0061] Figure 22 Fig. 12 is a structural view of the buoyancy plate.

[0062] In the drawings:

[0063] 1. guide rod holder; 2. drill string self-balancing device; 3. experimental bench top plate; 4. experimental bench side plate; 5. drill string system; 6. drill string working plate; 7. high-pressure sealing cavity; 8. rock debris collection blanket; 9. rock sample clamping device; 10. rock viewing device; 11. speed reducer mounting plate; 12. drilling fluid pipe; 13. air pipe; 14. air pump; 15. experimental bench bottom plate; 16. rotary drive mechanism; 17. intermediate container; 18. back pressure device; 19. drilling fluid pool; 20. drilling fluid pump; 21. guide rod; 22. rock sample; 23. side boss;

[0064] 101. guide rod holder sealing disc; 201. balance cavity; 202. counterforce rod; 203. dynamic sealing ring set; 204 cavity sealing bolt; 205. sealing disc; 301. holder mounting threaded hole; 302. guide rod limiting hole; 303. balance cavity mounting hole; 401. drilling fluid pipe through hole; 402. experimental bench right side plate; 403. experimental bench left side plate; 404. driving mechanism mounting cavity; 501. torque sensor; 502. sensor lower mounting bolt; 503. sensor connecting disc; 504. drill string; 505. drill string upper section rubber ring; 506. drill string upper section sealing ring; 507 piston section; 508. sealing body; 509. sealing body fixing body; 510. sealing ring set; 511. PDC cutter head; 512. PDC cutting tooth; 513. PDC pressing sheet; 514. pressing disc bolt; 515. pressing disc nut; 516. washer; 517. sensor upper mounting bolt; 518. buoyancy plate; 519. linear bearing; 601. high pressure sealing cavity; 702. cavity sealing ring; 703. drilling fluid path; 704. sealing body limiting hole; 705. sealing cavity; 706. rock sample clamping device mounting hole; 901. rock sample clamping body; 902. thrust ball bearing; 903. sealing gasket; 904. high pressure sealing ring; 905. clamping body rubber ring; 906. single inclined surface locking column; 907. rock pressing plate; 908. locking pressing plate; 909. pressing plate fixing bolt; 910. deep groove ball bearing; 911. bearing limiting device; 912. bearing fixing ring; 1401. drilling pressure air pump; 1402. back drilling air pump; 1601. speed reducer; 1602. speed reducer mounting nut; 1603. speed reducer mounting stud; 1604. servo motor; 2101. guide rod rubber ring; 2102. guide rod thread; 101a. guide rod holder light hole; 101b. air pipe mounting hole; 201a. drilling fluid pipe mounting threaded hole; 201b. balance cavity mounting thread; 201c. cavity sealing bolt hole; 202a. counterforce rod connecting hole; 503a. sensor connecting threaded hole; 503b. drill string connecting hole; 510a. high pressure inner sealing ring; 510b. high pressure outer sealing ring; 510c. high pressure outer rubber ring; 510d. high pressure inner rubber ring; 511a. cutter head mounting thread; 511b. PDC pressing sheet mounting threaded hole; 518a buoyancy plate mounting threaded hole; 518b buoyancy plate movable hole; 901a. rock sample clamping cavity; 901b. locking pressing plate mounting bolt hole; 901c. key groove. DETAILED DESCRIPTION

[0065] The application is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in this document, words such as "upper", "lower", and the like are used only to facilitate the description of the drawings, and do not limit the actual direction in use, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover inclusive rather than exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or inherent to such process, method, article or device.

[0066] Referring to Figures 1-22 As shown in the figure, the application provides a high confining pressure visual PDC bit rock breaking experimental device, which comprises a drilling fluid pipe 12, an air pipe 13, an air pump 14, an intermediate container 17, a back pressure device 18, a drilling fluid pool 19, a drilling fluid pump 20, and an experimental rack 23. The plurality of drilling fluid pipes 12 are respectively connected to the intermediate container 17, the back pressure device 18, the drilling fluid pool 19, the drilling fluid pump 20, and the air pipe 13 is connected to the air pump 14 and the experimental rack 23. The back pressure device 18 is further provided with a hydrostatic pressure sensor.

[0067] As Figure 1 shown, the air pump 14, the intermediate container 17, the back pressure device 18, the drilling fluid pool 19, and the experimental rack 23 are placed on the same horizontal plane and can be placed on the ground. The drilling fluid pump 20 is placed on the extension table extending outward from the drilling fluid pool 19, thereby improving the efficiency of the pump.

[0068] The experimental rack is a frame structure, which comprises, from top to bottom, a guide rod fixer 1, a drill string self-balancing device 2, an experimental rack top plate 3, an experimental rack side plate 4, a drill string system 5, a drill string working plate 6, a high-pressure sealing cavity 7, a rock sample clamping device 9, a rock viewing device 10, a speed reducer mounting plate 11, a rotary drive mechanism 16, and an experimental rack bottom plate 15. The experimental rack side plate 4 fixes the experimental rack top plate 3 and the speed reducer mounting plate 11 through the protruding side boss 23 in the middle.

[0069] The rock viewing device 10 is a hollow cylindrical structure, the inside of which is used to install the high-pressure sealing cavity 7. A window straight-through device is opened on the surface, and its size can be processed and set according to the set experimental object. In the preferred scheme of the embodiment, the window diameter is 50 mm, the window center is 108 mm away from the upper surface of the rock viewing device 10, and 245 mm away from the right contour line. The window is installed with acrylic glass, and the cutting condition can be clearly observed. The device wall is relatively thick, such as not less than 100 mm, to avoid deformation caused by the internal and external pressure difference.

[0070] As Figure 15As shown, the bottom of the guide rod holder 1 is provided with an outward flange as a guide rod holder sealing disc 101, the guide rod holder sealing disc 101 is provided with a guide rod holder light hole 101a and an air pipe mounting hole 101b, and is fixed on the 3 experimental bench top plate by bolts and connected with the air pump 14 through the air pipe mounting hole 101b and the air pump 14, so as to inject gas into the guide rod holder 1 through the air pump 14, and then adjust and maintain the position of the rock peeping device 10.

[0071] As shown in the figure, Figure 16 The drill string self-balancing device 2 includes, from top to bottom, a balance cavity 201, a counterforce rod 202, a dynamic sealing ring group 203, a cavity sealing bolt 204, and a sealing disc 205. The dynamic sealing ring group 203 is installed in the balance cavity 201. The balance cavity 201 is provided with a drilling fluid pipe mounting threaded hole 201a at the upper end, which is connected with the drilling fluid pipe 12 and is connected with the drilling fluid. The balance cavity 201 is connected with the sealing disc 205 through the cavity sealing bolt 204. The sealing disc 205 has a through hole for limiting the counterforce rod 202. The counterforce rod 202 is provided with a counterforce rod connecting hole 202a, which is connected with the torque sensor 501 of the drill string system 5 through the sensor upper mounting bolt 521.

[0072] The balance cavity 201 of the drill string self-balancing device is communicated with the sealing cavity 705 through the drilling fluid pipe 12 and is connected with the drilling fluid, so that the pressures at the upper and lower ends of the drill string system 5 are balanced, and an upward force of the drill string system 5 caused by the large pressure in the sealing cavity is avoided, which aggravates the jumping during work.

[0073] As shown in the figure, Figures 10-11 The drill string system 5 includes, from top to bottom, a torque sensor 501, a sensor connecting disc 503, a drill string 504, a PDC cutter 511, and a PDC cutting tooth 512. The torque sensor 501 is connected with the sensor connecting disc 503 through the sensor lower mounting bolt 502. The sensor connecting disc 503 is connected with the drill string 504 through bolts. The drill string 503 is provided with a drill string upper segment rubber ring 505, a drill string upper segment sealing ring 506, a drill string middle segment sealing ring 507, and a sealing body 508. The sealing body 508 is fixed through the sealing body fixing body 509. The drill string 504 is connected with the PDC cutter 511 through threads. The PDC cutter 511 is provided with the PDC cutting tooth 512 through the pressure disc bolt 514, the pressure disc nut 515, and the gasket 516.

[0074] The torque sensor 501 is a flange type static torque sensor. The upper end is limited in rotation by the buoyancy plate 518. After the rock sample 22 rotates and contacts the PDC cutting tooth 512, a force is applied to the cutting tooth. The force is transmitted to the sensor through the PDC cutter 511 and the drill string 504. One end of the sensor applies a driving force, and the other end is fixed through the buoyancy plate 518.

[0075] The sealing ring group 510 is provided with a high-pressure inner sealing ring 510a, a high-pressure outer sealing ring 510b, a high-pressure outer rubber ring 510c, and a high-pressure inner rubber ring 510d.

[0076] In particular, the drill string 504 can be divided into three shafts, which can be referred to as an upper drill string shaft, a piston section, and a lower drill string shaft from top to bottom. The upper drill string shaft is provided with four threaded holes at the top for connecting the torque sensor 501, and is also provided with multiple grooves for installing sealing rings and rubber rings. The piston section is also provided with grooves for installing sealing rings to form the piston section 507. The lower drill string shaft is provided with a reverse tapered threaded hole for connecting the PDC cutter head 511. Preferably, the upper drill string shaft and the lower drill string shaft have the same diameter, and the middle drill string shaft has a larger diameter than the other two shafts.

[0077] The drill string working plate 6 is designed with a drilling pressure air hole 601 for drilling and a back-off air hole 602 for back-off, and the air tightness is ensured by the piston section 507 and the sealing body 510 of the middle drill string section. The drilling pressure air hole 601 and the back-off air hole 602 are connected to the external drilling pressure air pump 14, which includes a drilling pressure air pump 1401 and a back-off air pump 1402.

[0078] As shown in Figure 17 The high-pressure sealing cavity 7 includes a high-pressure sealing cavity body 701, a cavity sealing ring 702, a drilling fluid path 703, a sealing body limiting hole 704, a sealing cavity 705, and a rock sample clamping device mounting hole 706. The outer surface of the high-pressure sealing cavity body 701 is provided with multiple grooves for installing the cavity sealing ring 702. A special drilling fluid path 703 is designed inside the high-pressure sealing cavity body 701. The drilling fluid enters the sealing cavity 705 through the opening of the drilling fluid path 703 to generate pressure on the rock sample 22. The rock sample clamping device mounting hole 706 is provided with a thrust ball bearing 902, a sealing gasket 903, a sealing ring 904, a clamping body rubber ring 905, and a deep groove ball bearing 910 to ensure the air tightness of the sealing cavity 705 and bear the forces generated during the working process.

[0079] As shown in Figures 3-6 and Figure 8As shown, the rock sample clamping device 9 includes a rock sample clamping body 901, a thrust ball bearing 902, a sealing gasket 903, a high-pressure sealing ring 904, a clamping body rubber ring 905, a single-sloping locking column 906, a rock pressure plate 907, a locking pressure plate 908, a pressure plate fixing bolt 909, a deep groove ball bearing 910, a bearing limiting device 911, and a bearing fixing ring 912. The rock sample clamping body 901 is installed in the rock sample clamping device mounting hole 706, which fixes the rock sample 22 in the sealed cavity 705, subjecting it to pressure. A rock cuttings collection blanket 8 can also be laid, ensuring that the rock cuttings collection blanket 8 is in close contact with the rock sample 22. The rock sample holder 901 is designed to collect rock debris effectively. The part of the rock sample holder 901 that holds the rock sample 22 is not exactly the same size as the rock sample 22. It holds the rock sample 22 by combining the rock pressure plate 907 and the single-inclined locking column 906. The rock sample holder 901 is equipped with a pressure plate fixing bolt 909 and a locking pressure plate 908 to secure the rock pressure plate 907 and the single-inclined locking column 906. There are two deep groove ball bearings 910. One is sandwiched between the bearing limiting device 911 and the bearing fixing ring 912. The other is installed between the bearing limiting device 911 and the sealing gasket 903. There is also a high-pressure sealing ring 904 on the sealing gasket 903.

[0080] like Figure 18 As shown, the rock sample holder 901 is used to hold the rock sample 22 and transmit motion. The rock sample holder 901 can be divided into three sections. The first section is the rock sample 22 installation section. This section has the largest diameter and contains a rock sample holding cavity 901a for installing the rock sample 22. Locking pressure plate mounting bolt holes 901b are opened on two adjacent sides of the rock sample holding cavity 901a for installing pressure plate fixing bolts 909. The second section has a step to assist in the installation of the bearing. The third section has a keyway 901c for key connection with the reducer 1601. The high-pressure sealing ring 904, sealing gasket 903, deep groove ball bearing 910, bearing limiting device 911, and bearing retaining ring 912 are installed in the mounting positions set in the high-pressure sealing cavity 701 and the reducer mounting plate 11.

[0081] The rotary drive mechanism 16 includes a reducer 1601, a reducer mounting nut 1602, a reducer mounting stud 1603, and a servo motor 1604. The reducer 1601 is connected and mounted on the reducer mounting plate 11 through the stud and transmits motion through the servo motor 1604.

[0082] The guide rod 21 includes a rubber ring 2101 and a guide rod body. The upper section of the guide rod body has a groove for installing the rubber ring 2101. The rubber ring 2101 is used to increase the friction force when the guide rod 21 is connected to the guide rod retainer 1. The lower end of the guide rod body is provided with a guide rod thread 2102 for connection with the rock viewing device 10.

[0083] Drilling fluid is drawn from drilling fluid pool 19 by drilling fluid pump 20, and connected by drilling fluid pipe 12. According to the flow direction, a portion of the drilling fluid is separated at the branch point of the drilling fluid pipe and enters the balance chamber 201 through the drilling fluid pipe installation thread hole 201a to achieve the effect of balancing the pressure of drill string system 5. The other portion follows the drilling fluid pipe 12 through the drilling fluid pipe through hole 401 of the left side plate 403 of the experimental stand, the drilling fluid passage 703 on the left side, the sealing chamber 705, the rock sample 22, the drilling fluid passage 703 on the right side, the drilling fluid pipe through hole 401 of the right side plate of the experimental stand, the intermediate container 17, the back pressure device 18, and the drilling fluid pool 19.

[0084] The intermediate container 17 includes an automatic pump and a hydrostatic pressure sensor. The hydrostatic pressure sensor and the back pressure device 18 ensure the pressure in the high-pressure sealed chamber 9 and the drill string self-balancing device 2. The back pressure device 18 maintains the pressure in the rock sample pressure chamber to the required value. When the pressure in the experimental setup exceeds the required value, the valve of the back pressure device 18 opens so that the injection flow rate is less than the discharge flow rate, and vice versa. Specific parameters can be set according to the pressure value required during the experiment.

[0085] After completing a set of PDC cutting experiments, the drill string system 5 is retracted by the air pump 1402 connected to the air pipe 13, and the cuttings collection blanket 8 is replaced at the same time.

[0086] A visual experimental method for rock cutting under confining pressure based on the aforementioned device includes the following steps:

[0087] Step 1. Lower the rock inspection device 10 to its lowest position to expose the high-pressure sealing cavity 701. Remove the pressure plate fixing bolt 909 on the single-bevel locking column 906. Then remove the locking column pressure plate 908, the single-bevel locking column 906, and the rock pressure plate 907. Place the rock sample 22 in a suitable position on the rock sample holder 901, ensuring that the lower surface of the rock sample 22 is in close contact with the rock sample holder 901, with two sides in close contact with the inner surface of the rock sample holder 901. Then tighten the previously used locking pressure plate 908 and the single-bevel locking plate. The column 906 and rock pressure plate 907 are restored to their original state, that is, the rock pressure plate 907 is close to the side of the rock sample 22, the inclined surface of the single inclined locking column 906 is in contact with the inclined surface of the rock pressure plate 907, the two through holes of the locking pressure plate 908 are aligned with the corresponding threaded holes on the rock sample holder 901 and the pressure plate fixing bolts 909 are installed. The same measures are taken for the other locking point. Then the rock viewing device 10 is restored to the position where the viewing window faces the PDC cutting tooth 512 and the rock cutting collection blanket 8 is installed.

[0088] Step 2. Connect the opening of the drilling fluid passage 703 on the high-pressure sealing cavity 701 to the corresponding drilling fluid pipe 12, connect the drilling fluid pipe installation thread hole 201a on the drill string balance device 2 to the corresponding drilling fluid pipe 12, turn on the drilling hydraulic pump 20 to inject drilling fluid, so that the rock sample 22 is subjected to a certain hydraulic pressure, so that the pressure on the drill string system 5 reaches a balanced state.

[0089] Step 3. Connect the drill pressure air hole 601 on the drill string working plate 6 to the corresponding air pipe 13, turn on the drill pressure air pump 1401 to allow the drill string system 5 to drill down, and let the PDC cutting teeth 512 contact the upper surface of the rock sample 22.

[0090] Step 4. Start the servo motor 1604 and increase the air pressure of the air pump 1401 to allow the PDC cutting teeth 512 to pre-scrape the rock sample 22 to a certain extent. After the PDC cutting teeth 512 have a certain contact area with the surface of the rock sample 22, turn off the servo motor 1604.

[0091] Step 5. Start the back pressure unit 18 and preset the pressure value;

[0092] Step 6. After the hydrostatic pressure sensor of the intermediate container 17 reaches the target value, the rock sample 22 is under the experimental confining pressure. Start the servo motor 1604, and observe the torque of the drill string 504 in real time through the data acquisition device connected to the torque sensor 501. After drilling to the predetermined depth, turn off the servo motor 1604, and raise the drill string system 5 to the initial height through the drill retraction air hole 602 on the drill string working plate 6. Turn off the air pump 1402.

[0093] Step 7. After the drill string system 5 has risen to the initial height of the cutter, slowly reduce the pressure value set by the back pressure device 18 to zero.

[0094] Step 8. When the hydrostatic pressure sensor attached to the intermediate container 17 displays a value of 0, turn off the hydraulic pump 20 to relieve the pressure on the rock sample 22;

[0095] Step 9. Lower the rock viewing device 10 to the lowest position and take out the rock cuttings collection blanket (8) to collect the rock cuttings;

[0096] Step 10. Repeat steps 1-9 for the next round of experiments.

[0097] During the above steps, after the device is assembled, when the upper surface of the rock inspection device 10 contacts the lower surface of the drill string working plate 6, the air pump 14 continuously supplies gas from below, causing the guide rod to move upward in a manner similar to pushing a piston. This, in turn, drives the rock inspection device 10 to reach and stabilize at the set observation position, such as... Figure 14 As shown, this facilitates observation during the experiment;

[0098] Similarly, after the experiment, the air pump 14 is turned off, and the rock viewing device 10 uses its own weight to push the gas downward. With the effect of the overflow valve slowing down the exhaust speed, it slowly descends until it reaches the limit, thereby protecting the safety of the device.

[0099] In step 1, rock clamping plates 907 are used to clamp the rock sample on one side, while rock clamping plates 907 are not used on the other two sides. This is mainly to reduce the number of moving parts, which makes clamping easier. Since the rock sample clamping device is a moving part, reducing the number of rock clamping plates 907 used can reduce the probability of loosening and prevent the rock from shaking during the experiment.

[0100] In step 6, by changing relevant variables using a static torque sensor during operation, the torque sensed by the sensor will change, and this change in torque will be observed through an external data display. Combined with observations through the observation window during the process, the torque of the drill pipe during rock breaking under different confining pressures at different rotational speeds can be investigated.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-confining-pressure visualized PDC drill bit rock-breaking experimental device, characterized in that, The system includes an environmental system, a support system, and a rock cutting system. The support system supports the rock cutting system, and the environmental system provides drilling fluid and drilling pressure to the rock cutting system. The rock cutting system includes a high-pressure sealing cavity (7) and a drill string system (5). The high-pressure sealing cavity (7) is a cylindrical structure with a hollow hole. A radially penetrating structure is provided in the middle of its high-pressure sealing cavity (701) as a sealing cavity (705). A rock viewing device (10) with an annular inner hole is fitted on the outside of the high-pressure sealing cavity (7) and can move along the outer circumference of the high-pressure sealing cavity (7). The rock viewing device (10) and the high-pressure sealing cavity (7) maintain a sliding seal. The high-pressure sealing cavity (7) is provided with cavity sealing rings (702) on the upper and lower outer circumferences of the corresponding sealing cavity (705). The cavity sealing rings (702) are used to seal with the externally fitted rock viewing device (10). A through hole is provided between the wall of the rock viewing device (10) and its annular inner hole as an observation window, and a sealing glass is provided on the observation window.

2. The visual experimental apparatus for rock cutting under confining pressure according to claim 1, characterized in that, The environmental system includes multiple drilling fluid pipes (12), and an intermediate container (17), a back pressure device (18), a drilling fluid pool (19), and a drilling fluid pump (20) connected by the drilling fluid pipes (12). The intermediate container (17) is equipped with a hydrostatic pressure sensor. It also includes an air pump group (14) consisting of a drilling pressure air pump (1401) and a drill retraction air pump (1402).

3. The visual experimental apparatus for rock cutting under confining pressure according to claim 2, characterized in that, The support system includes an experimental bench base plate (15), two corresponding experimental bench side plates (4) are provided on the side of the experimental bench base plate (15), an experimental bench top plate (3) is provided on the top of the experimental bench side plate (4), and a drill column working plate (6) and a reducer mounting plate (11) are provided on the upper and lower sides of the middle part of the experimental bench side plate (4), respectively.

4. The visual experimental device for rock cutting under confining pressure according to claim 3, characterized in that, The high-pressure sealing cavity (7) and the rock inspection device (10) are installed between the drill string working plate (6) and the reducer mounting plate. The reducer mounting plate (11) has a longitudinal through hole in the middle. A rotary drive mechanism (16) is provided below the reducer mounting plate (11). The rotary drive mechanism (16) includes a reducer (1601) and a servo motor (1604). The reducer (1601) is fixed below the reducer mounting plate (11) by a reducer mounting stud (1603). The servo motor (1604) is connected to the reducer (1601). A rock sample clamping device (9) is provided on the drive mechanism (16) through the longitudinal through hole of the reducer mounting plate (11). The rock sample clamping device (9) is used to fix the rock sample (22). The rock sample clamping device (9) includes a rock sample clamping body (901). The upper part of the rock sample clamping body (901) extends into the high-pressure sealing cavity (7). The top dimension of the rock sample holder (901) is larger than that of other parts; the bottom of the high pressure sealing cavity (7) is installed on the upper part of the reducer mounting plate (11); the rock sample holder (901) is provided with a deep groove ball bearing (910), a sealing gasket (903), and a high pressure sealing ring (904) at the position where it contacts the top of the reducer mounting plate (11) in the middle, and the deep groove ball bearing (910) is fixed by the bearing limiting device (911). The rock sample holder (901) is provided with a thrust ball bearing (902), a holder rubber ring (905), and a sealing gasket (903-2) at the position where it contacts the high pressure sealing cavity (7) on the lower side of the top. The rock sample holder (901) is provided with a component that docks with the rotary drive mechanism (16) at the bottom, and the rock sample holder (901) is connected and driven to rotate through the rotary drive mechanism (16), thereby driving the rock sample placed in the rock sample holder (901) to rotate.

5. The visual experimental apparatus for rock cutting under confining pressure according to claim 2, characterized in that, A drill string self-balancing device (2) is provided above the drill string system (5). The drill string self-balancing device (2) is provided with a balance cavity (201), a reaction rod (202), a dynamic sealing ring group (203), and a sealing plate (205) for connecting to the top plate (3) of the experimental bench. The inner side of the balance cavity (201) is a hollow structure. The sealing plate (205) is connected to the bottom of the balance cavity (201) through the cavity sealing bolt (204). The reaction rod (202) passes through the middle of the sealing plate (205) and extends into the balance cavity (201). The dynamic sealing ring group (203) is used to seal the inside of the balance cavity (201). The drill string system (5) includes a torque sensor (501), a sensor connection plate (503), and a drill string (504). A buoyancy plate (518) is connected above the torque sensor via a sensor mounting bolt (517), and a sensor connection plate (503) is connected below the torque sensor via a sensor mounting bolt (502). The sensor connection plate (503) is connected to the drill string (504) via a thread below. A PDC cutterhead (511) is provided at the bottom of the drill string (504). The buoyancy plate (518) has a threaded hole (518a) in the middle, which is connected to the sensor by a mounting bolt on the sensor. The buoyancy plate (518) has through holes (518a) at both ends, which are connected to the linear bearing (519) and the guide rod (21). The reaction rod has a reaction rod connection hole (202a) and is connected to the torque sensor (501) by bolts, so that the drill string system (5) can be fixed below the drill string self-balancing device (2).

6. The visual experimental apparatus for rock cutting under confining pressure according to claim 5, characterized in that, The drill string working plate (6) includes a drill string working plate body (603), on which a longitudinal through hole is provided. The drill string (504) passes through the through hole of the drill string working plate (6) and contacts the rock sample (22). The drill string working plate body (603) is also provided with a drill pressure air hole (601) and a drill retraction air hole (602) connected to the through hole. A piston section (507) is provided in the middle of the drill string (504). The connection points of the drill pressure air hole (601) and the drill retraction air hole (602) with the through hole are located on the upper and lower sides of the piston section, respectively. The drill pressure air hole (601) and the drill retraction air hole (602) are connected to the drill pressure air pump (1401) and the drill retraction air pump (1402), respectively, to realize the control of the drill string. (504) Drill pressure adjustment; the drill string working plate body (603) has a step with a lower enlarged hole in the through hole, the drill string (504) has a step that adapts to the through hole of the drill string working plate body (603), and an upper rubber ring (505) is provided on the step of the drill string (504). The drill string (504) has an upper sealing ring (506) at a position higher than the drill pressure air hole (601), and a sealing body (508) at a position lower than the drill withdrawal air hole (602). The sealing body (508) is fixed by a sealing body fixing body (509), and a sealing ring assembly (510) is provided below the sealing body fixing body (509). The bottom of the drill string (504) is connected to the PDC cutter head (511) by a thread. The PDC cutter head (511) has an hourglass-shaped structure. PDC pressure plates (513) are installed on its side by pressure plate bolts (514), pressure plate nuts (515) and washers (516). The bottom of the PDC cutting teeth (512) is located below the PDC pressure plates (513) and protrudes downward compared to the PDC cutter head (511). The sealing ring assembly (510) is equipped with a high-pressure inner sealing ring (510a), a high-pressure outer sealing ring (510b), a high-pressure outer rubber ring (510c), and a high-pressure inner rubber ring (510d).

7. The visual experimental apparatus for rock cutting under confining pressure according to claim 6, characterized in that, At least two guide rod holders (1) are provided above the top plate (3) of the experimental bench, and a guide rod (21) is provided above the rock viewing device (10). The guide rod (21) is connected to the guide rod holder (1) and can move up and down. The guide rod holder (1) is hollow inside and has an opening at the bottom. The corresponding experimental bench top plate (3) has a longitudinal through hole. The top of the guide rod (21) has a protruding end with a guide rod rubber ring (2101). The protruding end fits against the inner wall of the guide rod holder (1) to achieve upper and lower sealing inside the guide rod holder (1). The lower end of the guide rod (21) has a guide rod thread (2102) to connect with the rock viewing device (10). An overflow valve is installed at the bottom of the guide rod holder (1), and an air pipe is provided at the bottom to connect to the air pump (14). By pumping air, the guide rod (21) can be moved up and down, thereby driving the rock viewing device (10) to the required height. The rock observation device (10) is a hollow cylindrical structure. The interior is used to install a high-pressure sealed cavity (7). A window is opened on the surface that leads directly to the center of the device. The window is fitted with acrylic glass so that the cutting situation can be clearly observed.

8. The visual experimental apparatus for rock cutting under confining pressure according to claim 7, characterized in that, Both of the experimental bench side plates (4) are provided with drilling fluid pipe through holes (401). The drilling fluid pump (20) is connected to the top of the balance chamber (201) and a drilling fluid pipe through hole (401) respectively through a drilling fluid pipe (12). The other drilling fluid pipe through hole (401) is connected to the intermediate container (17). The other end of the drilling fluid pipe through hole (401) connected to the drilling fluid pump (20) is connected to the drilling fluid passage (703) set on the side of the sealing chamber (705) through another section of drilling fluid pipe (12), so as to transport the drilling fluid into the sealing chamber (705).

9. A visual experimental apparatus for rock cutting under confining pressure according to claim 8, characterized in that, The top center of the rock sample holder (901) is provided with a rectangular cavity as a rock sample holding cavity (901a) to accommodate the rock sample (22). Semicircular grooves are provided on two adjacent sides of the rock sample holding cavity (901a). Locking plate mounting bolt holes (901b) are provided in the wall surface of the rock sample holding cavity (901a) on both sides of the semicircular grooves. Matching rock pressure plates (907) are also provided, with no less than two. Two rock pressure plates (907) are placed. After the rock sample (22) is fixed on the front of the rock pressure plate (907), a single inclined locking pin (906) is inserted into the semi-circular groove to squeeze the rock pressure plate (907) and press the rock sample (22). A locking plate (908) is placed on top to fix the rock pressure plate (907) downward. A plate fixing bolt (909) is inserted into the bolt hole (901b) of the locking plate to allow the plate fixing bolt (909) to pass through the locking plate (908) and fix the locking plate. It is also equipped with a matching rock cuttings collection blanket (8) for lining the rock sample clamping cavity (901a); The rock cuttings collection blanket (8) has a racetrack-shaped structure with a rectangular through hole in the center with a side length of 100mm×100mm. Two racetrack-shaped holes are located on two adjacent sides of the rectangular hole for passing through the locking plate (908). This device is used to collect rock cuttings splashed during the cutting of rock samples (22).

10. A visual experimental method for rock cutting under confining pressure, employing the apparatus as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Before testing, if the rock inspection device (10) blocks the sealing cavity (705), lower the rock inspection device (10) to expose the sealing cavity (705). Remove the pressure plate fixing bolt (909), single-slope locking column (906), locking column pressure plate (908), and rock pressure plate (907) on the single-slope locking column (906) in sequence. After cleaning the inside, place the rock sample (22) in a suitable position on the rock sample holder (901) with the lower surface of the rock sample (22) close to the rock sample holder (901) and two sides close to the inner surface of the rock sample holder (901). Then, remove the previously locked pressure plate (909). 08) The single-slope locking column (906) and rock pressure plate (907) are restored to their original state, that is, the rock pressure plate (907) is close to the side of the rock sample (22), the slope of the single-slope locking column (906) is in contact with the slope of the rock pressure plate (907), the locking pressure plate (908) is a racetrack-shaped structure, with two through holes at the center of both ends and aligned with the corresponding threaded holes on the rock sample holder (901) and the pressure plate fixing bolts (909) are installed. The same measures are taken for another locking point. Then the rock viewing device (10) is restored to the position where the viewing window faces the PDC cutting tooth (512), and the rock cutting collection blanket (8) is installed. Step 2: Connect the opening of the drilling fluid passage (703) on the high-pressure sealing cavity (701) to the corresponding drilling fluid pipe (12), connect the drilling fluid pipe installation thread hole (201a) on the drill string balance device (2) to the corresponding drilling fluid pipe (12), turn on the drilling hydraulic pump (20) to inject drilling fluid, so that the rock sample (22) is subjected to a certain hydraulic pressure, so that the pressure on the drill string system (5) reaches a balanced state; Step 3: Connect the drill pressure air hole (601) on the drill string working plate (6) to the corresponding air pipe (13), turn on the drill pressure air pump (1401) to allow the drill string system (5) to drill down, and let the PDC cutting teeth (512) contact the upper surface of the rock sample (22); Step 4: Start the servo motor (1604) to rotate the rock sample holder (901), increase the air pressure of the drilling air pump (1401) to the set value, and let the PDC cutting teeth (512) pre-scrape the rock sample (22) to a certain extent. After the PDC cutting teeth (512) have a certain contact area with the surface of the rock sample (22), turn off the servo motor (1604). Step 5: Start the back pressure unit (18) and preset the pressure value; Step 6: After the hydrostatic pressure sensor in the intermediate container (17) reaches the target value, the rock sample (22) is under the experimental confining pressure. Start the servo motor (1604), and observe the torque of the drill string (504) in real time through the data acquisition device connected to the torque sensor (501). After drilling to the predetermined depth, turn off the servo motor (1604), and raise the drill string system (5) to the initial height through the drill retraction air hole (602) on the drill string working plate (6). Turn off the air pump (1402). Step 7: After the drill string system (5) rises to the initial height, slowly reduce the pressure value set by the back pressure device (18) to zero. Step 8: When the hydrostatic pressure sensor attached to the intermediate container (17) shows zero, turn off the hydraulic pump (20) to eliminate the pressure on the rock sample (22); Step 9: Lower the rock viewing device (10) to the lowest point and take out the rock cuttings collection blanket (8) to collect the rock cuttings; Step 10: If a new round of experiments is required, repeat steps 1-9.

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