Well wall deformation observation simulation test device and test method in coal rock gas drilling process

Abstract

The invention provides a well wall deformation observation simulation test device and method in the coal rock gas drilling process, and belongs to the technical field of coal rock gas drilling. The device comprises a base, a hydraulic oil cylinder I, a hydraulic oil cylinder II, a test box body, a coal rock sample for test, a drilling fluid box, a controller, an elevator and an ultrasonic imaging control system; the test coal rock sample is positioned in the test box body; a simulated drilling well is arranged in the test coal rock sample; a simulation drilling rod is arranged in the simulation drilling well, an ultrasonic probe assembly is arranged in the simulation drilling rod, and the ultrasonic probe assembly is electrically connected with an ultrasonic imaging control system outside the test box body; the upper end of the ultrasonic probe assembly is connected with an elevator outside the test box body; the simulated drilling well is provided with a gyrator, and the elevator and the gyrator are both in electric signal connection with the controller. The device truly simulates the drilling process, tests the deformation of the surrounding rock of the well wall, and provides certain theoretical support for prediction of the collapse period of the well wall and optimization design of the drilling fluid.

Description

Technical Field

[0001] This invention belongs to the technical field of downhole tools used for sealing during drilling and completion in the petroleum industry, specifically relating to a simulation test device and test method for wellbore deformation observation during coal and rock gas drilling. Background Technology

[0002] With the increasing development of coal and rock gas, deep and complex well drilling projects are becoming more and more common. During the drilling process, drilling fluid is injected from the center of the drill pipe and returned to the surface through the annular gap between the drill pipe and the wellbore, serving to carry rock cuttings, cool the drill bit, and protect the borehole wall. As the drilling fluid circulates within the wellbore, it penetrates the wellbore wall under pressure. When the surrounding rock contains many water-absorbing minerals, the wellbore wall will expand and deform after absorbing water. Especially when the surrounding rock has certain fissures, the intrusion of drilling fluid can cause significant deformation of the wellbore wall, potentially leading to wellbore collapse and resulting in well accidents. Wellbore collapse severely impacts drilling efficiency and causes significant losses of manpower and resources. The deformation of the wellbore wall under the action of drilling fluid is continuous, and the deformation varies depending on the type of drilling fluid. Therefore, selecting an appropriate drilling fluid based on the characteristics of the surrounding rock is crucial to minimizing wellbore deformation and preventing wellbore collapse.

[0003] According to CN115014971A, a test device and method for a geostress-head adjustable vertical shaft freezing model are disclosed. This invention relates to the field of model testing of artificial freezing processes, specifically a geostress-head adjustable vertical shaft freezing model test device and method. The device includes: a model test chamber, a water source tank with adjustable water head, a small spiral freezer, and a bidirectional loading device. The specific steps are as follows: S1, connecting the test device; S2, layering samples in the model test chamber and simultaneously burying the monitoring system; S3, installing the small spiral freezer; S4, adjusting the bidirectional loading device; S5, providing a water source; S6, starting the freezing test; S7, applying external load; S8, stopping the test when the vertical shaft wall deformation is too large or damage occurs. This invention simulates the deformation characteristics of the frozen well wall during the vertical shaft freezing construction process in sandy soil strata through indoor model testing, realizing the simulation of geostress and water head pressure under different stratum depths.

[0004] Existing devices are relatively simple and cannot accurately evaluate wellbore deformation during drilling, nor can they simulate real drilling conditions. To address this, this invention designs an indoor testing device capable of realistically simulating wellbore deformation under drilling conditions, thereby obtaining the relationship between wellbore deformation and time, predicting the wellbore collapse cycle, and optimizing a suitable drilling fluid system to reduce wellbore deformation. Summary of the Invention

[0005] To overcome the limitations of existing devices, which are relatively simple and cannot accurately evaluate wellbore deformation during drilling or simulate real drilling conditions, this invention provides a simulation test device and method for observing wellbore deformation during coal and rock gas drilling. This invention uses the test device to realistically simulate the drilling process, test the deformation of the surrounding rock of the wellbore, and provide theoretical support for predicting the wellbore collapse cycle and optimizing the design of drilling fluid.

[0006] The technical solution adopted in this invention is as follows: A simulation test device for observing wellbore deformation during coal and rock gas drilling includes a base, hydraulic cylinder one, hydraulic cylinder two, a test chamber, a coal and rock sample for testing, a drilling fluid tank, a controller, a hoist, and an ultrasonic imaging control system; the coal and rock sample for testing is located inside the test chamber; the test coal and rock sample contains a simulated drilling operation; The simulated drilling system includes a simulated drill pipe, which contains an ultrasonic probe assembly. The ultrasonic probe assembly is electrically connected to an ultrasonic imaging control system outside the test chamber. The upper end of the ultrasonic probe assembly is connected to an elevator outside the test chamber. The simulated drilling system includes a rotary head, and both the elevator and the rotary head are electrically connected to the controller. The annulus between the simulated drill pipe and the ultrasonic probe assembly, as well as the annulus between the simulated drill pipe and the simulated drilling system, are connected to the drilling fluid tank. The test chamber is located above the base. The two adjacent sides and the bottom of the test coal and rock sample are respectively provided with horizontal pressure plates and vertical pressure plates. The horizontal pressure plates and vertical pressure plates are respectively connected to the base through hydraulic cylinder one and hydraulic cylinder two located outside the test chamber. The other surfaces of the test coal and rock sample are provided with fixing plates. The base is connected and fixed to the fixing plates inside the test chamber through fixing plate brackets. The ultrasonic probe assembly includes an ultrasonic probe connecting column and an ultrasonic probe. The ultrasonic probe is located at the bottom of the ultrasonic probe connecting column and is electrically connected to the ultrasonic imaging control system outside the test chamber via an ultrasonic probe cable located inside the ultrasonic probe connecting column.

[0007] The ultrasonic probe connecting column is equipped with a lifting ring at the top, and the lifting ring is connected to a lift outside the test chamber. The rotary head is located above the coal and rock sample used in the experiment and is fixed to the top fixed plate by the rotary head bracket; a second bearing is provided on the contact surface between the simulated drill rod and the top fixed plate, and a first bearing is provided between the top of the simulated drill rod and the ultrasonic probe connecting pipe.

[0008] The test chamber is equipped with a heating device, which is electrically connected to a temperature controller located inside the test chamber.

[0009] The ultrasonic probe assembly and the annulus of the simulated drill pipe are connected to the drilling fluid tank through a drilling fluid injection pipeline; the simulated drilling and the annulus of the simulated drill pipe are connected to the drilling fluid tank through a flushing fluid outflow pipeline; a pump is installed on the drilling fluid injection pipeline, and a control valve is installed on the flushing fluid outflow pipeline.

[0010] A simulation test method for observing wellbore deformation during coal and rock drilling, characterized by the following specific steps: Step 1: Process the coal and rock used for the test into standard specifications that meet the test requirements. Drill a simulated borehole in the top of the sample to form a simulated well. The simulated borehole does not penetrate the coal and rock sample used for the test. Step 2: Place the coal and rock sample for testing inside the pressure plate of the test chamber, set the pressure of the horizontal and vertical pressure plates according to the actual force, and lower the simulated drill rod equipped with the ultrasonic probe assembly into the simulated well of the coal and rock sample. Step 3: Prepare the drilling fluid for the test in the drilling fluid tank and connect the drilling fluid injection line and the flushing fluid outflow line; start the heating device to make the temperature inside the test chamber the same as the temperature of the original coal and rock strata. Step 4: Turn on the pump to circulate the drilling fluid, turn on the rotary head to drive the simulated drill pipe to rotate and simulate the drilling process, and at the same time adjust the opening of the control valve to adjust the drilling fluid circulation pressure and simulate different drilling fluid pressures. Step 5: After the simulated drilling process has been set for a certain time, the simulated drill pipe stops rotating, the drilling fluid stops circulating, and the elevator starts to lift the simulated drill pipe and ultrasonic probe assembly into the well. During the lifting process, ultrasonic imaging of the surrounding rock of the well wall is completed. After being lifted to the position, imaging of the entire well section is completed, and then it is lowered back to the initial position. Step 6: Restart the pump to circulate the drilling fluid, and start the rotary head to drive the drill pipe to rotate, simulating the drilling process. Step 7: Repeat the experimental process of Step 5 and Step 6 to obtain ultrasonic imaging data of the well wall at set time intervals. Step 8: After the experiment, export the data for post-processing to obtain the relationship between the deformation of the surrounding rock of the well wall and time, which is used to predict the well wall collapse cycle.

[0011] By using drilling fluids with different performance parameters to conduct experiments on the relationship between wellbore surrounding rock deformation and time, the influence of drilling fluid performance parameters on wellbore deformation was obtained, which can be used to optimize drilling fluid performance parameters.

[0012] By applying different geostresses to test the relationship between wellbore surrounding rock deformation and time, the relationship between wellbore surrounding rock deformation and time under different pressures is obtained, and the method of testing the influence of stress magnitude on wellbore deformation is obtained. The above-mentioned test on the influence of geostress magnitude on wellbore deformation is used to optimize drilling design.

[0013] By setting different temperatures inside the experimental chamber, the relationship between the deformation of the surrounding rock of the well wall and time was tested, and the experimental method for obtaining the influence law of temperature on well wall deformation was obtained.

[0014] The beneficial effects of this invention are: In this invention, during the simulated drilling process, the drill pipe rotates while the internal ultrasonic probe connecting the tubing remains stationary. The drilling fluid circulates and rotates upwards within the wellbore, simulating the actual drilling process. The ultrasonic wellbore imaging process begins by activating the ultrasonic imaging control system. The tubing (including bearing one, simulated drill pipe, and ultrasonic probe connecting tubing, all three components being an integrated structure) is slowly lifted using a lifting ring. During this lifting process, the ultrasonic probe continuously emits and receives ultrasonic waves, completing the acoustic imaging of the wellbore.

[0015] By alternating between the drilling process and ultrasonic wellbore imaging, three-dimensional images of the wellbore can be obtained intermittently. This process can be automatically carried out at intervals by a control system. After the experiment, the wellbore images can be exported, and image processing software can be used to analyze the deformation characteristics of the wellbore, revealing the variation of wellbore deformation with drilling fluid circulation time.

[0016] This invention can simulate the rotation of the drill string and the circulation of drilling fluid during the test. The drilling fluid is not static during the test, but circulates positively while simulating the rotation of the drill string, which is consistent with the drilling conditions in actual engineering.

[0017] This invention intermittently performs three-dimensional ultrasonic imaging of the wellbore to obtain wellbore deformation characteristic parameters after different drilling fluid circulation times. This has important guiding significance for predicting the wellbore collapse cycle and optimizing the performance parameters of the drilling fluid. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the experimental device of the present invention.

[0019] Figure 2 This is an enlarged schematic diagram of the structure of the coal and rock sample used in the experiment of this invention.

[0020] Figure 3 This is a schematic diagram of the coal and rock test sample of the present invention. Figure 4 This is a schematic diagram of the simulated drilling process and ultrasonic wellbore imaging process of the present invention.

[0021] Figure 5 This is a schematic diagram of the drilling and internal tubing structure of the present invention.

[0022] The present invention will now be described in further detail with reference to the accompanying drawings.

[0023] In the figure, the attached figures are labeled as follows: 1. Base; 2. Test chamber support; 3. Hydraulic cylinder one; 4. Hydraulic cylinder two; 5. Test chamber; 6. Coal and rock sample for testing; 7. Drilling fluid tank; 8. Control valve; 9. Fluid outlet pipeline; 10. Pump; 11. Drilling fluid injection pipeline; 12. Controller; 13. Elevator; 14. Ultrasonic imaging control system; 15. Temperature controller; 16. Heating device; 17. Lifting ring; 18. Bearing one; 19. Rotary head; 20. Bearing two; 21. Drilling; 22. Simulated drill pipe; 23. Horizontal pressure plate; 24. Vertical pressure plate; 25. Ultrasonic probe; 26. Ultrasonic probe cable; 27. Ultrasonic probe connecting string; 28. Fixing plate. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0026] Example 1: To overcome the shortcomings of existing devices, which are relatively simple, cannot accurately evaluate wellbore deformation during drilling, and cannot simulate real drilling conditions, this invention provides... Figures 1-5 The invention presents a simulation test device and method for observing wellbore deformation during coal and rock gas drilling. The test device realistically simulates the drilling process and tests the deformation of the surrounding rock of the wellbore, providing theoretical support for the prediction of wellbore collapse cycle and the optimization design of drilling fluid.

[0027] A simulation test device for observing wellbore deformation during coal and rock gas drilling includes a base 1, a hydraulic cylinder 3, a hydraulic cylinder 4, a test chamber 5, a coal and rock sample 6 for testing, a drilling fluid tank 7, a controller 12, a hoist 13, and an ultrasonic imaging control system 14; the coal and rock sample 6 for testing is located inside the test chamber 5; a simulated drilling 21 is installed inside the coal and rock sample 6 for testing. The simulated drilling 21 is equipped with a simulated drill pipe 22, and an ultrasonic probe assembly is installed inside the simulated drill pipe 22. The ultrasonic probe assembly is electrically connected to the ultrasonic imaging control system 14 outside the test chamber 5. The upper end of the ultrasonic probe assembly is connected to the elevator 13 outside the test chamber 5. The simulated drilling 21 is equipped with a rotary head 19. Both the elevator 13 and the rotary head 19 are electrically connected to the controller 12. The annulus between the simulated drill pipe 22 and the ultrasonic probe assembly, as well as the annulus between the simulated drill pipe 22 and the simulated drilling 21, are connected to the drilling fluid tank 7. The test chamber 5 is located above the base 1. The two adjacent sides and the bottom of the test coal and rock sample 6 are respectively provided with a horizontal pressure plate 23 and a vertical pressure plate 24. The horizontal pressure plate 23 and the vertical pressure plate 24 are respectively connected to the base 1 through a hydraulic cylinder 3 and a hydraulic cylinder 4 located outside the test chamber 5. The other surfaces of the test coal and rock sample 6 are provided with a fixing plate 28. The base 1 is connected and fixed to the fixing plate 28 inside the test chamber 5 through a fixing plate bracket. like Figure 1 As shown, in this invention, the test chamber support 2 connects the test chamber 5 to the base 1, and the first hydraulic cylinder 3 applies simulated vertical formation pressure to the test coal and rock sample 6; the second hydraulic cylinder 4 consists of two sets, arranged vertically in the horizontal direction, and applies simulated horizontal formation pressure to the test coal and rock sample 6 in two horizontal directions. The test process of this invention is completed inside the test chamber 5, which has certain thermal insulation properties.

[0028] In this invention, the test coal and rock sample 6 is cubic in shape with a side length of 500 mm. Before the test, a simulated well 21 is prefabricated on its top. A horizontal pressure plate 23 is used to apply a horizontal force to the test coal and rock sample 6; a vertical pressure plate 24 is used to apply a vertical force to the test coal and rock sample 6. A fixing plate 28 provides a reaction force and, in conjunction with other pressure plates, provides pressure to the test coal and rock sample 6.

[0029] In this invention, an ultrasonic probe assembly is installed inside the simulated drill pipe 22 to form a simulated drilling tool; the controller 12 is used to control the rotary head 19 that drives the simulated drill pipe 22 to rotate and the elevator 13 that lifts the simulated drilling tool, and has logic control functions. The elevator 13 is mainly used to lift and lower the simulated drilling tool. During the lifting process, ultrasonic imaging of the well wall is performed. After the imaging is completed, the drilling tool is lowered to the initial position; the ultrasonic imaging control system 14 is used to control the ultrasonic imaging instrument to image the well wall.

[0030] The ultrasonic imaging control system 14 and controller 12 in this invention are both existing technologies, and will not be further described in this invention.

[0031] In this invention, the heating device 16 is located on the inner wall of the test chamber 5, and the heating device 16 controls the temperature inside the test chamber 5. The heating device 16 is prior art and will not be further described in this invention.

[0032] This invention can accurately simulate the triaxial stress state of coal and rock and the actual formation temperature, ensuring that the temperature and pressure experienced by the coal and rock sample 6 during the experiment remain consistent with those at the original formation. The experiment can simulate the rotation of the drill string and the circulation of drilling fluid. The drilling fluid is not stationary during the experiment but circulates positively while simulating the rotation of the drill pipe 22, thus maintaining consistency with actual drilling conditions in engineering.

[0033] Example 2: Based on Embodiment 1, in this embodiment, preferably, the ultrasonic probe assembly includes an ultrasonic probe connecting column 27 and an ultrasonic probe 25. The ultrasonic probe 25 is located at the bottom of the ultrasonic probe connecting column 27, and the ultrasonic probe 25 is electrically connected to the ultrasonic imaging control system 14 outside the test chamber 5 through an ultrasonic probe cable 26 located inside the ultrasonic probe connecting column 27.

[0034] Preferably, the top of the ultrasonic probe connecting column 27 is provided with a lifting ring 17, which is connected to the elevator 13 outside the test chamber 5. like Figure 2 As shown, in this invention, the ultrasonic probe 25 is used to perform ultrasonic imaging of the well wall; the ultrasonic probe cable 26 is used to power the ultrasonic probe 25 and transmit signals.

[0035] Preferably, the rotary device 19 is located above the test coal and rock sample 6 and is fixed to the top fixing plate 28 by the rotary device bracket; a bearing 20 is provided on the contact surface between the simulated drill rod 22 and the top fixing plate 28, and a bearing 18 is provided between the top of the simulated drill rod 22 and the ultrasonic probe connecting column 27.

[0036] like Figure 2 As shown, in this invention, bearing 18 ensures that the ultrasonic probe connecting pipe 27 inside the simulated drill rod 22 does not rotate during rotation, achieving single-action. Rotator 19 is used to drive the simulated drill rod 22 to rotate and can adjust the rotation speed; bearing 20 is installed on the pressure plate of the top fixing plate 28 to ensure the normal rotation of the simulated drill rod 22.

[0037] Preferably, the test chamber 5 is equipped with a heating device 16, which is electrically connected to a temperature controller 15 located in the test chamber 5.

[0038] In this invention, the temperature controller 15 can control the temperature inside the test chamber 5; the heating device 16 is preferably a heater, used to heat the test chamber 5 to simulate the actual formation temperature.

[0039] Preferably, the annulus between the ultrasonic probe assembly and the simulated drill pipe 22 is connected to the drilling fluid tank 7 via the drilling fluid injection pipeline 11; the annulus between the simulated drilling 21 and the simulated drill pipe 22 is connected to the drilling fluid tank 7 via the flushing fluid outflow pipeline 9; a pump 10 is provided on the drilling fluid injection pipeline 11, and a control valve 8 is provided on the flushing fluid outflow pipeline 9.

[0040] In this invention, the drilling fluid tank 7 is used to hold the drilling fluid, the control valve 8 is used to control the drilling fluid pressure to simulate the drilling well wall being subjected to the liquid column pressure of the drilling fluid, and the pump 10 is used to drive the drilling fluid circulation, drawing the drilling fluid from the drilling fluid tank 7 and injecting it into the simulated drill pipe 22.

[0041] This device can realistically simulate the triaxial stress state of coal and rock and the actual formation temperature, so that the temperature and pressure experienced by the sample during the test are consistent with those in the original formation.

[0042] like Figure 3 and Figure 5 As shown, the sample in this invention is a test coal and rock sample 6, which is cubic in shape with a side length of 500 mm. Before the test, a simulated well 21 is prefabricated on its top.

[0043] The experimental device provided by this invention can simulate the drilling process of the drill string assembly in the formation, realistically reproduce the circulation process of drilling fluid in the wellbore, intermittently image the simulated wellbore during the simulated drilling process, and finally export the imaging data and perform post-processing to obtain the deformation characteristics of the surrounding rock of the wellbore during the simulated drilling process.

[0044] To achieve the above, the experimental apparatus provided by this invention operates as follows: First, the coal and rock test sample 6 collected in the field is processed into a cube shape required by the test apparatus. A simulated well is drilled at the center of the top, without penetrating the coal and rock test sample 6. The processed sample is placed inside the test chamber 5, which is equipped with a heating device 16. The temperature can be set to simulate the actual formation temperature. Inside the test chamber 5, three mutually perpendicular hydraulic cylinders apply pressure to the coal and rock test sample 6 in three directions. The pressure in these three directions can be precisely adjusted, and the magnitude of the pressure can be referenced to the actual in-situ stress borne by the coal and rock, so that the coal and rock test sample 6 is under triaxial compression, realistically simulating the actual stress situation of the sample in the real formation. A schematic diagram of the coal and rock test sample 6 is shown below. Figure 4 As shown.

[0045] Second, the upper part of sample 6 used in the coal and rock test is equipped with a simulated well 21. A simulated drill pipe 22 is inserted into the simulated well 21. An ultrasonic probe connecting string 27 is installed inside the simulated drill pipe 22. An ultrasonic probe 25 is connected to the lower part of the ultrasonic probe connecting string 27 and extends out from the bottom of the simulated drill pipe 22. The ultrasonic probe 25 is used to observe the well wall and image the well wall. During the test, the rotary head 19 is started, and the simulated drill pipe 22 begins to rotate. Drilling fluid is injected into the simulated drill pipe 22 through pump 10. The drilling fluid returns from the annular space between the simulated drill pipe 22 and the well wall, simulating the flow of drilling fluid during the actual drilling process. A schematic diagram of the simulated well 21 and its internal string is shown below. Figure 5 As shown.

[0046] Third, during the circulation of drilling fluid in the simulated drilling 21, the well wall is scourted by the flow of drilling fluid and continuously absorbs water, causing deformation of the well wall. After the drilling fluid circulates for a set time (e.g., 10 minutes), the pump is stopped and the rotary valve 19 is stopped, the drilling fluid circulation stops, and the simulated drill pipe 22 stops rotating.

[0047] Fourth, activate the ultrasonic imaging control system 14, and slowly raise the simulated drill pipe 22 and its internal ultrasonic probe 25 inside the well. During the raising of the ultrasonic probe 25, the ultrasonic imaging control system 14 controls the ultrasonic probe 25 to image the well wall, obtaining a three-dimensional image of the surrounding rock. After imaging is completed, lower the simulated drill pipe 22 and its internal ultrasonic probe 25 back to their initial positions, and restart the rotary head 19 and pump 10 to simulate the drilling process. The drilling fluid is circulated again for 10 minutes, and the well wall imaging is repeated once. By following the above steps, three-dimensional images of the well wall can be obtained intermittently (at 10-minute intervals). This process can be automatically carried out at intervals by the control system.

[0048] Fifth, after the experiment, wellbore images can be exported, and image processing software can be used to analyze the deformation characteristics of the wellbore and obtain the variation law of wellbore deformation with drilling fluid circulation time.

[0049] In this invention, the simulated drilling process and ultrasonic wellbore imaging process are as follows: Figure 4 As shown, during the simulated drilling process, the simulated drill pipe 22 rotates, while the ultrasonic probe connecting string 27 inside remains stationary. The drilling fluid circulates and rotates upwards within the well wall, simulating the real drilling process. The ultrasonic well wall imaging process first activates the ultrasonic imaging control system 14, and the well string (including bearing 18, simulated drill pipe 22, and ultrasonic probe connecting string 27, which are three components integrated into one unit) is slowly lifted up via the lifting ring 17. During the lifting process, the ultrasonic probe 25 continuously emits and receives ultrasonic waves to complete the acoustic imaging of the well wall.

[0050] By alternating between the drilling process and ultrasonic wellbore imaging, three-dimensional images of the wellbore can be obtained intermittently. This process can be automatically carried out at intervals by a control system. After the experiment, the wellbore images can be exported, and image processing software can be used to analyze the deformation characteristics of the wellbore, revealing the variation of wellbore deformation with drilling fluid circulation time.

[0051] This invention simulates the drill string rotation and drilling fluid circulation process during testing. The drilling fluid is not stationary during the test but circulates positively while simulating the rotation of the drill pipe 22, consistent with actual drilling conditions in engineering. The invention intermittently performs three-dimensional ultrasonic imaging of the wellbore to obtain wellbore deformation characteristic parameters after different drilling fluid circulation times. This has significant guiding significance for predicting the wellbore collapse cycle and optimizing the performance parameters of the drilling fluid.

[0052] Example 3: Based on Example 1 or 2, this example provides a simulation test method for observing wellbore deformation during coal and rock drilling. The specific steps are as follows: Step 1: The coal and rock used for the test are processed into a standard specification test coal and rock sample 6 that meets the test requirements. A simulated borehole is drilled in the top of the sample to form a simulated well 21. The simulated borehole does not penetrate the test coal and rock sample 6. Step 2: Place the test coal and rock sample 6 inside the pressure plate of the test chamber 5, set the pressure of the horizontal pressure plate 23 and the vertical pressure plate 24 according to the actual force, and lower the simulated drill rod 22 equipped with the ultrasonic probe assembly into the simulated well 21 of the coal and rock sample. Step 3: Prepare the drilling fluid for the test in the drilling fluid tank 7 and connect the drilling fluid injection line 11 to the flushing fluid outflow line 9; start the heating device 16 so that the temperature inside the test chamber 5 is the same as the temperature of the original coal and rock strata. Step 4: Turn on pump 10 to circulate drilling fluid, turn on rotary head 19 to drive simulated drill pipe 22 to rotate to simulate drilling process, and at the same time adjust the opening of control valve 8 to adjust drilling fluid circulation pressure to simulate different drilling fluid pressures. Step 5: After the simulated drilling process is set for a certain time, the simulated drill pipe 22 stops rotating, the drilling fluid stops circulating, and the elevator 13 starts to lift the simulated drill pipe 22 and the ultrasonic probe assembly into the well. During the lifting process, ultrasonic imaging of the surrounding rock of the well wall is completed. After being lifted to the position, imaging of the entire well section is completed, and then it is lowered to the initial position. Step 6: Restart pump 10 to circulate drilling fluid, and start rotary head 19 to drive drill pipe rotation to simulate the drilling process; Step 7: Repeat the experimental process of Step 5 and Step 6 to obtain ultrasonic imaging data of the well wall at set time intervals. Step 8: After the experiment, export the data for post-processing to obtain the relationship between the deformation of the surrounding rock of the well wall and time, which is used to predict the well wall collapse cycle.

[0053] The above experimental method is Experiment 1: Experiment on the relationship between well wall deformation and time, used to predict the well wall collapse cycle.

[0054] In this invention, preferably, experiments are conducted using drilling fluids with different performance parameters to investigate the relationship between wellbore surrounding rock deformation and time, thereby obtaining an experiment on the influence of drilling fluid performance parameters on wellbore deformation, which is used to optimize drilling fluid performance parameters.

[0055] Preferably, the method involves conducting experiments on the relationship between wellbore surrounding rock deformation and time by applying different in-situ stresses, obtaining the relationship between wellbore surrounding rock deformation and time under different pressures, and obtaining the experimental law of the influence of stress magnitude on wellbore deformation. The above-mentioned experimental law of the influence of in-situ stress magnitude on wellbore deformation can be used to optimize drilling design.

[0056] Preferably, by setting different temperatures inside the experimental chamber 5, the relationship between the deformation of the surrounding rock of the well wall and time is tested, and the experimental method for obtaining the influence law of temperature on the deformation of the well wall is obtained.

[0057] For different purposes, the present invention can conduct various experiments: Based on Experiment 1, the following experiments are conducted: Experiment 2, the effect of drilling fluid performance parameters on wellbore deformation, was conducted to optimize drilling fluid performance parameters.

[0058] In this invention, the specific process of Experiment 2 is as follows: The experiment is divided into multiple groups, each using drilling fluids with different performance parameters to carry out Experiment 1. The specific experimental process is as follows: Experiment 1 was conducted using drilling fluid A to obtain the relationship between the deformation of the surrounding rock of the wellbore and time under the condition of drilling fluid A.

[0059] Experiment 1 was conducted again using drilling fluid B to obtain the relationship between the deformation of the surrounding rock of the wellbore and time under the condition of drilling fluid B.

[0060] Experiment 1 was conducted again using drilling fluid C to obtain the relationship between the deformation of the surrounding rock of the wellbore and time under the condition of drilling fluid C.

[0061] Drilling fluid A, drilling fluid B, and drilling fluid C are three different drilling fluids. After the test, the curves of well wall deformation over time under the three drilling fluid conditions were compared. The drilling fluid with the smallest well wall deformation was selected as the optimal drilling fluid. In actual drilling, it can ensure a small well wall deformation, which is most beneficial for maintaining well wall stability.

[0062] Experiment 3: Experiment on the influence of geostress on wellbore deformation, used to optimize drilling design.

[0063] In this invention, the specific process of Experiment 3 is as follows: combining the in-situ stress of the drilled coal and rock in the actual engineering drilling process, firstly, the pressure of the pressure plate in this test device is set using in-situ stress A, and Experiment 1 is carried out to obtain the relationship between the deformation of the well wall surrounding rock and time under in-situ stress A.

[0064] The pressure of the pressure plate in the test device was set using the geostress B, and the first test was conducted to obtain the relationship between the deformation of the well wall surrounding rock and time under the geostress B condition.

[0065] The pressure of the pressure plate in the test device was set using the geostress C, and the first test was conducted to obtain the relationship between the deformation of the well wall surrounding rock and time under the geostress C condition.

[0066] In-situ stress A, in-situ stress B, and in-situ stress C are three different in-situ stresses. After the test, the curves of well wall deformation over time under the three in-situ stress conditions are compared to show the relationship between well wall deformation and in-situ stress at the same moment.

[0067] Experiment 4: Experiment on the influence of temperature on wellbore deformation.

[0068] In this invention, the specific process of Experiment 4 is as follows: First, the temperature of the heater was controlled by a temperature controller at temperature A, and Experiment 1 was conducted to obtain the relationship between the deformation of the surrounding rock of the wellbore and time under temperature A.

[0069] The temperature of the heater was controlled by a temperature controller set to temperature B. Experiment 1 was conducted to obtain the relationship between the deformation of the surrounding rock of the wellbore and time under temperature B.

[0070] The temperature of the heater was controlled by a temperature controller set at temperature C, and Experiment 1 was conducted to obtain the relationship between the deformation of the surrounding rock of the wellbore and time under temperature C.

[0071] Temperatures A, B, and C are three different temperatures. After the experiment, the curves of well wall deformation over time under the three temperature conditions are compared to show the relationship between well wall deformation and temperature at the same moment.

[0072] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0073] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0074] The examples above are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention fall within the scope of protection of the present invention. Device structures and method steps not described in detail in this invention are prior art and will not be further described in this invention.

Claims

1. A simulation test device for observing wellbore deformation during coal and rock gas drilling, characterized in that: It includes a base (1), a hydraulic cylinder one (3), a hydraulic cylinder two (4), a test chamber (5), a test coal and rock sample (6), a drilling fluid tank (7), a controller (12), a lift (13), and an ultrasonic imaging control system (14); the test coal and rock sample (6) is located inside the test chamber (5); the test coal and rock sample (6) is equipped with a simulated drilling (21); The simulated drilling (21) is equipped with a simulated drill pipe (22), and an ultrasonic probe assembly is installed inside the simulated drill pipe (22). The ultrasonic probe assembly is electrically connected to the ultrasonic imaging control system (14) outside the test chamber (5). The upper end of the ultrasonic probe assembly is connected to the elevator (13) outside the test chamber (5). The simulated drilling (21) is equipped with a rotary head (19). Both the elevator (13) and the rotary head (19) are electrically connected to the controller (12). The annulus between the simulated drill pipe (22) and the ultrasonic probe assembly, as well as the annulus between the simulated drill pipe (22) and the simulated drilling (21), are connected to the drilling fluid tank (7). The test chamber (5) is located above the base (1). The two adjacent sides and the bottom of the test coal and rock sample (6) are respectively provided with a horizontal pressure plate (23) and a vertical pressure plate (24). The horizontal pressure plate (23) and the vertical pressure plate (24) are respectively connected to the base (1) through the corresponding hydraulic cylinder one (3) and hydraulic cylinder two (4) located outside the test chamber (5). The other surfaces of the test coal and rock sample (6) are provided with a fixing plate (28). The base (1) is connected and fixed to the fixing plate (28) inside the test chamber (5) through the fixing plate bracket.

2. The simulation test device for observing wellbore deformation during coal and rock gas drilling process according to claim 1, characterized in that: The ultrasonic probe assembly includes an ultrasonic probe connecting column (27) and an ultrasonic probe (25). The ultrasonic probe (25) is located at the bottom of the ultrasonic probe connecting column (27). The ultrasonic probe (25) is electrically connected to the ultrasonic imaging control system (14) outside the test chamber (5) through an ultrasonic probe cable (26) located inside the ultrasonic probe connecting column (27).

3. The simulation test device for observing wellbore deformation during coal and rock gas drilling process according to claim 2, characterized in that: The ultrasonic probe connecting column (27) is provided with a lifting ring (17) at the top, and the lifting ring (17) is connected to the elevator (13) outside the test chamber (5).

4. The simulation test device for observing wellbore deformation during coal and rock gas drilling process according to claim 1, characterized in that: The rotary device (19) is located above the test coal and rock sample (6) and is fixed on the top fixed plate (28) by the rotary device bracket; the simulated drill rod (22) is provided with a bearing two (20) on the contact surface with the top fixed plate (28), and a bearing one (18) is provided between the top of the simulated drill rod (22) and the ultrasonic probe connecting pipe column (27).

5. The simulation test device for observing wellbore deformation during coal and rock gas drilling process according to claim 1, characterized in that: The test chamber (5) is equipped with a heating device (16), which is electrically connected to a temperature controller (15) located in the test chamber (5).

6. The simulation test device for observing wellbore deformation during coal and rock gas drilling process according to claim 1, characterized in that: The annulus of the ultrasonic probe assembly and the simulated drill pipe (22) is connected to the drilling fluid tank (7) through the drilling fluid injection pipeline (11); the annulus of the simulated drilling (21) and the simulated drill pipe (22) is connected to the drilling fluid tank (7) through the flushing fluid outflow pipeline (9); a pump (10) is provided on the drilling fluid injection pipeline (11), and a control valve (8) is provided on the flushing fluid outflow pipeline (9).

7. The test method for any of the wellbore deformation observation simulation test devices for coal and rock gas drilling processes according to claims 1-6, characterized in that: The specific steps are as follows: Step 1: The coal and rock used for the test are processed into a standard specification test coal and rock sample (6) that meets the test requirements. A simulated borehole is drilled on the top of the sample to form a simulated well (21). The simulated borehole does not penetrate the test coal and rock sample (6). Step 2: Place the test coal and rock sample (6) inside the pressure plate of the test chamber (5), set the pressure of the horizontal pressure plate (23) and the vertical pressure plate (24) according to the actual force, and lower the simulated drill rod (22) equipped with the ultrasonic probe assembly into the simulated well (21) of the coal and rock sample. Step 3: Prepare the drilling fluid for the test in the drilling fluid tank (7) and connect the drilling fluid injection pipeline (11) and the flushing fluid outflow pipeline (9); start the heating device (16) so that the temperature inside the test chamber (5) is the same as the temperature of the original coal and rock strata; Step 4: Turn on the pump (10) to circulate the drilling fluid, turn on the rotary head (19) to drive the simulated drill pipe (22) to rotate and simulate the drilling process, and at the same time adjust the opening of the control valve (8) to adjust the drilling fluid circulation pressure and simulate different drilling fluid pressures. Step 5: After the simulated drilling process is set for a certain time, the simulated drill pipe (22) stops rotating, the drilling fluid stops circulating, and the elevator (13) starts to lift the simulated drill pipe (22) and ultrasonic probe assembly in the well. During the lifting process, ultrasonic imaging of the surrounding rock of the well wall is completed. After being lifted to the position, imaging of the entire well section is completed, and then it is lowered to the initial position. Step 6: Start the pump (10) again to circulate the drilling fluid, and start the rotary head (19) to drive the drill pipe to rotate, simulating the drilling process; Step 7: Repeat the experimental process of Step 5 and Step 6 to obtain ultrasonic imaging data of the well wall at set time intervals. Step 8: After the experiment, export the data for post-processing to obtain the relationship between the deformation of the surrounding rock of the well wall and time, which is used to predict the well wall collapse cycle.

8. The simulation test method for observing wellbore deformation during coal and rock drilling according to claim 7, characterized in that: By using drilling fluids with different performance parameters to conduct experiments on the relationship between wellbore surrounding rock deformation and time, the influence of drilling fluid performance parameters on wellbore deformation was obtained, which can be used to optimize drilling fluid performance parameters.

9. The simulation test method for observing wellbore deformation during coal and rock drilling according to claim 7, characterized in that: By applying different geostresses to test the relationship between wellbore surrounding rock deformation and time, the relationship between wellbore surrounding rock deformation and time under different pressures is obtained, and the method of testing the influence of stress magnitude on wellbore deformation is obtained. The above-mentioned test on the influence of geostress magnitude on wellbore deformation is used to optimize drilling design.

10. The simulation test method for observing wellbore deformation during coal and rock drilling according to claim 7, characterized in that: By setting different temperatures inside the experimental chamber (5), the relationship between the deformation of the surrounding rock of the well wall and time is tested, and the experimental method for the influence of temperature on the deformation of the well wall is obtained.

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