Drill string drag reduction experiment device, experiment method and friction resistance coefficient correction method

Abstract

The invention belongs to the technical field of oil and gas well drill string dynamics, and particularly relates to a drill string drag reduction experiment device and method and a friction resistance coefficient correction method.The drill string drag reduction experiment device comprises a simulation drill string, a sleeve and a vibrator, the simulation drill string is slidably connected with the bottom wall of the sleeve under the action of gravity, and the two ends of the simulation drill string extend out of the two ends of the sleeve respectively; the two ends of the simulation drill column are connected with the pushing motor and the sliding block through the first tension-compression sensor and the second tension-compression sensor respectively. The vibrator is arranged on the simulation drill column and used for exciting the simulation drill column to move in a reciprocating mode. Static friction before resistance reduction and dynamic friction after resistance reduction are collected through the resistance reduction device for the drill string experiment, the resistance reduction effect can be evaluated more objectively and rationally by calculating the resistance reduction efficiency, and evaluation does not depend on experience of engineers any more. The method can also be used for verifying and correcting a theoretical model, so that the structure, parameters and the like of the vibration resistance reduction tool are better optimized and improved, and the vibration resistance reduction effect is more fully exerted.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas well drill string dynamics, and in particular relates to a drill string drag reduction experimental device, an experimental method and a friction coefficient correction method. Background Art

[0002] As the exploration and development of oil and gas resources develops towards deep layers, deep waters and unconventional areas, the objective conditions on the ground and underground facing drilling and completion projects are becoming more complex, which puts forward higher requirements on the level of drilling and completion technology. Complex well technologies such as horizontal wells and extended reach wells can effectively overcome the limitations of ground conditions, develop various complex oil and gas resources economically and efficiently, and minimize the negative impact on the natural environment. However, during the drilling of high-angle sections of horizontal wells and extended reach wells, problems such as high friction, frequent pressure relief, and drill string buckling are prominent, and the wellbore extension capacity is severely limited, affecting the efficiency and safety of drilling and completion operations. Field practice shows that installing a vibration drag reduction tool on the drill string can effectively reduce the friction of the drill string, alleviate the frequent pressure relief problem during drilling, improve drilling efficiency, and increase the wellbore extension limit of horizontal wells and extended reach wells.

[0003] Research on vibration drag reduction tools at home and abroad mainly focuses on tool development, theoretical models and field applications. However, the research on the evaluation method of vibration drag reduction effect of vibration drag reduction tools is still insufficient, especially for the evaluation of the drag reduction effect of drill strings with vibration drag reduction tools. Field application mainly relies on the experience of engineers and lacks relevant indoor experimental simulation devices. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and to provide a drill string drag reduction experimental device.

[0005] The present invention is realized through the following technical scheme: a drill string drag reduction experimental device, comprising a simulated drill string, a casing and a vibrator, wherein the outer diameter of the simulated drill string is smaller than the inner diameter of the casing, the simulated drill string is slidably connected to the bottom wall of the casing under the action of gravity, and the two ends of the simulated drill string extend out of the two ends of the casing respectively; the two ends of the simulated drill string are respectively connected to a driving motor and a slider through a first tension and compression sensor and a second tension and compression sensor; the vibrator is arranged on the simulated drill string and is used to excite the reciprocating motion of the simulated drill string.

[0006] Furthermore, the vibrator is a pneumatic vibrator, and the vibration frequency and amplitude can be adjusted by controlling the air volume of the air compressor.

[0007] Furthermore, a computer for monitoring the sensor data is also included.

[0008] Furthermore, it also includes a base provided with a guide rail, the sleeve is fixedly supported on the base by a clip, the push motor is fixedly connected to the base, and the slider is slidably connected to the guide rail.

[0009] Furthermore, the two ends of the simulated drill string are respectively connected to the first tension and compression sensor and the second tension and compression sensor through a connecting assembly; the connecting assembly includes an adapter, a connecting rod and a chuck; the simulated drill string is connected to the first tension and compression sensor or the second tension and compression sensor through the adapter, the tension and compression sensor is connected to the connecting rod, and the connecting rod is connected to the pushing motor or the slider through the chuck.

[0010] Furthermore, a displacement sensor device is provided at either end of the simulated drill string.

[0011] Furthermore, the displacement sensing device includes a reflective plate and a laser ranging sensor, wherein the reflective plate is vertically and fixedly connected to the simulated drill string, and the laser ranging sensor is facing the reflective plate and fixedly connected to the casing.

[0012] The present invention also provides a drill string drag reduction test method, which uses the drill string drag reduction test device described in the present invention to collect static friction before drag reduction and dynamic friction after drag reduction, and calculates drag reduction efficiency based on the static friction and dynamic friction. The drag reduction efficiency is equal to the difference between static friction and dynamic friction divided by static friction.

[0013] Furthermore, the static friction collection process is as follows: the driving motor continuously increases the axial force acting on the simulated drill string. Under the premise of ensuring that the simulated drill string does not move, the maximum pressure difference between the first tension and compression sensor and the second tension and compression sensor is the static friction before drag reduction.

[0014] Furthermore, the dynamic friction collection process is as follows: start the vibrator, simulate the static friction between the drill string and the casing, which will be converted into dynamic friction under the excitation of the vibrator, and simulate the reciprocating vibration of the casing. The pressure difference between the first tension and compression sensor and the second tension and compression sensor at both ends of the simulated drill string after vibration is similar to a sinusoidal change form, and then the equivalent pressure difference is obtained by integral calculation, which is the dynamic friction after drag reduction.

[0015] The present invention also provides a friction coefficient correction method, which establishes a drill string axial vibration control model, sets initial boundary conditions, and uses finite element method to solve the drill string displacement and friction force in the axial vibration control model under different friction coefficients as model calculation results; uses the drill string drag reduction experimental device described in the present invention to collect the displacement and friction force of the simulated drill string under the same initial boundary conditions as simulation experiment results; compares the model calculation results and the simulation experiment results, and uses the friction coefficient corresponding to the model calculation result with the smallest error and the error within a threshold range as the corrected friction coefficient.

[0016] Furthermore, the drill string axial vibration control model is as follows:

[0017]

[0018] Where E is the elastic modulus of the drill string, A is the cross-sectional area of ​​the drill string microelement, u is the axial displacement of the drill string microelement, s is the arc length of the drill string microelement, t is the time, μ is the friction coefficient between the drill string and the well wall, and ρ is s represents the buoyancy of the drill string, F represents the contact positive pressure between the drill string and the well wall, T represents the axial force of the drill string, k b represents the wellbore curvature, k α Well inclination change rate, represents the rate of change of well inclination azimuth, α represents the average well inclination angle, and c represents the drilling fluid damping coefficient.

[0019] Compared with the prior art, the beneficial effects of the present invention include:

[0020] 1. The drill string drag reduction experimental device of the present invention takes into account the nonlinearity of friction force, adds the function of vibration drag reduction tool to the simulated drill string, makes the movement of the simulated drill string conform to the bilinear hysteresis friction model as much as possible, adjusts the vibration frequency and amplitude by controlling the air volume of the air compressor, strives to be as close to the actual working conditions as possible, and the experimental results are highly credible.

[0021] 2. By collecting the static friction before drag reduction and the dynamic friction after drag reduction through the drill string experimental drag reduction device of the present invention, the drag reduction efficiency can be calculated to evaluate the drag reduction effect more objectively and rationally, instead of relying on the experience of engineers for evaluation.

[0022] 3. The present invention can also be used to verify and correct theoretical models, so as to better optimize and improve the structure and parameters of vibration drag reduction tools and give full play to the vibration drag reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the overall structure of the simulation experimental device;

[0024] Figure 2 A partial schematic diagram of the simulation experimental device.

[0025] Explanation of the reference numerals: 1-base, 2-support leg, 3-pushing motor, 4-chuck, 5-first tension and compression sensor, 6-conversion joint, 7-casing, 8-simulated drill string, 9-expansion sleeve, 10-first laser ranging sensor, 11-clip, 12-guide rail, 13-vibrator, 14-reflection plate, 15-second laser ranging sensor, 16-second tension and compression sensor, 17-connecting rod, 18-slider, 19-distribution cabinet, 20-computer, 21-air compressor, 22-control cabinet. DETAILED DESCRIPTION

[0026] Example 1

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0028] refer to Figure 1 and Figure 2 As shown, a drill string drag reduction experimental device includes a simulated drill string 8, a casing 7 and a vibrator 13. The outer diameter of the simulated drill string 8 is smaller than the inner diameter of the casing 7. The simulated drill string 8 is slidably connected to the bottom wall of the casing 7 under the action of gravity, and the two ends of the simulated drill string 8 extend out of the two ends of the casing 7 respectively; the two ends of the simulated drill string 8 are respectively connected to the driving motor 3 and the slider 18 through the first tension and compression sensor 5 and the second tension and compression sensor 15; the vibrator 13 is arranged on the simulated drill string 8 and is used to excite the simulated drill string 8 to reciprocate.

[0029] The drill string drag reduction experimental device also includes a base 1 with a guide rail 12, a computer 20, a power distribution cabinet 19, an air compressor 21 and a control cabinet 22. The casing 7 is fixedly supported on the base 1 by a clip 11, the push motor 3 is fixedly connected to the base 1, and the slider 18 is slidably connected to the guide rail 12; the base 1 is fixedly supported by the support leg 2 below.

[0030] The two ends of the simulated drill string are respectively connected to the first tension and compression sensor and the second tension and compression sensor through a connecting assembly; the connecting assembly includes an adapter, a connecting rod and a chuck; the simulated drill string is connected to the first tension and compression sensor or the second tension and compression sensor through the adapter, the tension and compression sensor is connected to the connecting rod, and the connecting rod is connected to the pushing motor or the slider through the chuck.

[0031] The computer 20 can display the measurement data of the first tension and compression sensor 5 and the tension and compression sensor 16 .

[0032] The driving motor 3 can provide different axial forces to the simulated drill string 8 .

[0033] The vibrator 13 is a pneumatic vibrator. The air compressor 21 provides an excitation force for the vibrator 13 and is adjusted through a control cabinet 22: the vibration frequency and amplitude are adjusted by controlling the air volume of the air compressor.

[0034] The excitation of the vibrator causes the simulated drill string to vibrate. Within the range of the vibration wave, the friction force changes from static friction to dynamic friction, thereby greatly reducing the friction force and achieving a drag reduction effect.

[0035] Relying on the reciprocating excitation motion of the vibrator, assuming that the vibrator starts to vibrate to the left first, the bilinear motion law is that the speed changes from zero to the maximum and then decreases to zero, then changes direction from zero to increase and then decreases, and continues to reciprocate after changing direction, similar to the pendulum of an alarm clock. Hysteresis mainly refers to the mechanical phenomenon of damping energy consumption generated during the motion process, such as strain lagging behind stress.

[0036] Example 2

[0037] A drill string drag reduction test method is disclosed. The drill string drag reduction test device of Example 1 is used to collect static friction before drag reduction and dynamic friction after drag reduction, respectively, and the drag reduction efficiency is calculated based on the static friction and dynamic friction. The drag reduction efficiency is equal to the difference between the static friction and the dynamic friction divided by the static friction.

[0038] The static friction collection process is as follows: the driving motor continuously increases the axial force acting on the simulated drill string. Under the premise of ensuring that the simulated drill string does not move, the maximum pressure difference between the first tension and compression sensor and the second tension and compression sensor is the static friction before drag reduction.

[0039] The dynamic friction collection process is as follows: start the vibrator, simulate the static friction between the drill string and the casing, which will be converted into dynamic friction under the excitation of the vibrator, and simulate the reciprocating vibration of the casing. The pressure difference between the first tension and compression sensor and the second tension and compression sensor at both ends of the simulated drill string after vibration is similar to a sinusoidal change form, and then the equivalent pressure difference is obtained by integral calculation, which is the dynamic friction after drag reduction.

[0040] The experimental process is as follows:

[0041] When conducting a drill string simulation experiment indoors, assemble all the devices, check the safety of each connection, especially the connection between the air compressor 21, the control cabinet 22 and the pneumatic vibrator 13, to prevent gas leakage and avoid potential safety hazards; open the power distribution cabinet 19 to start working, start the control cabinet 22, debug the computer 20, and set the transmission data accuracy; start the air compressor 21, and after all the machines are running normally, observe the data transmission of the tension and compression sensor 5 and the tension and compression sensor 16, the displacement sensor 10 and the displacement sensor 15 in the computer 20, and start to obtain the stored data when the data is in a stable state, and continuously adjust the air intake of the air compressor 21 to control the excitation force of the pneumatic vibrator 13. The frequency of the pneumatic vibrator 13 can be adjusted on the control cabinet 22, and the gears of 1 to 10 Hz are set respectively. Observe and record the changes of the tension and compression sensor 5 and the tension and compression sensor 16, the displacement sensor 10 and the displacement sensor 15, and the axial force and axial displacement of the simulated drill string 8 at the corresponding position can be obtained. Establish a theoretical model of the same scale, compare the calculation results with the measurement results, and perform fitting.

[0042] After the work is completed, the device cannot be disassembled immediately. The measurement data of the computer 20 should be saved for backup. The start buttons of the control cabinet 22 and the air compressor 21 should be turned off. After the air compressor 21 is completely depressurized, the power supply of the distribution cabinet 19 should be turned off to complete the entire experimental operation.

[0043] The experimental results of the present invention can be directly used to explore relevant laws, such as analyzing the vibration characteristics of the drill string under the excitation forces of different amplitudes, frequencies, vibration modes, etc. generated by the vibration drag reduction tool, so as to evaluate the friction and drag reduction effects of vibration drag reduction tools with different parameters.

[0044] Example 3

[0045] refer to Figure 1 and Figure 2 As shown, a drill string drag reduction experimental device includes a simulated drill string 8, a casing 7 and a vibrator 13. The simulated drill string 8 is slidably connected to the casing 7, and two ends of the simulated drill string 8 extend out of two ends of the casing 7 respectively; the two ends of the simulated drill string 8 are respectively connected to the driving motor 3 and the slider 18 through a first tension and compression sensor 5 and a second tension and compression sensor 15; the vibrator 13 is arranged on the simulated drill string 8 and is used to excite the simulated drill string 8 to reciprocate.

[0046] The drill string drag reduction experimental device also includes a base 1 with a guide rail 12, a computer 20, a power distribution cabinet 19, an air compressor 21 and a control cabinet 22. The casing 7 is fixedly supported on the base 1 by a clip 11, the push motor 3 is fixedly connected to the base 1, and the slider 18 is slidably connected to the guide rail 12; the base 1 is fixedly supported by the support leg 2 below.

[0047] The two ends of the simulated drill string are respectively connected to the first tension and compression sensor and the second tension and compression sensor through a connecting assembly; the connecting assembly includes an adapter, a connecting rod and a chuck; the simulated drill string is connected to the first tension and compression sensor or the second tension and compression sensor through the adapter, the tension and compression sensor is connected to the connecting rod, and the connecting rod is connected to the pushing motor or the slider through the chuck.

[0048] A displacement sensor device is provided at either end of the simulated drill string to achieve displacement measurement of the simulated drill string. However, this specific implementation has a redundant design, and displacement sensors are provided at both ends of the simulated drill string. The displacement sensor device includes a reflector and a laser ranging sensor. The reflector is vertically and fixedly connected to the simulated drill string, and the laser ranging sensor is directly opposite to the reflector and fixedly connected to the casing.

[0049] The first laser ranging sensor 10 and the second laser ranging sensor 15 are installed at both ends of the sleeve respectively, specifically at the connection between the expansion sleeve 9 and the sleeve 7. The diameter of the expansion sleeve is larger than that of the sleeve to provide space for the reflector. The laser ranging sensor and the reflector 14 are combined to measure the displacement change at this location.

[0050] The computer 20 can display the measurement data of the first tension and compression sensor 5 , the tension and compression sensor 16 , the first laser distance measuring sensor 10 and the second laser distance measuring sensor 15 .

[0051] The vibrator 13 is a pneumatic vibrator. The air compressor 21 provides an excitation force for the vibrator 13 and is adjusted through a control cabinet 22: the vibration frequency and amplitude are adjusted by controlling the air volume of the air compressor.

[0052] The driving motor 3 can provide different axial forces to the simulated drill string 8 .

[0053] Example 4

[0054] The experimental results of the drill string drag reduction experimental device of Example 3 can also be used to verify and correct relevant theoretical models.

[0055] A friction coefficient correction method is disclosed. The method comprises the following steps: establishing a drill string axial vibration control model, setting initial boundary conditions, using finite element method to solve the drill string displacement and friction force in the axial vibration control model under different friction coefficients as model calculation results; using the drill string drag reduction experimental device of Example 3 to collect the displacement and friction force of the simulated drill string under the same initial boundary conditions as simulation experimental results; comparing the model calculation results with the simulation experimental results, and taking the friction coefficient corresponding to the model calculation result with the smallest error and within a threshold range as the corrected friction coefficient.

[0056] The drill string axial vibration control model is as follows:

[0057]

[0058] Where E is the elastic modulus of the drill string, A is the cross-sectional area of ​​the drill string microelement, u is the axial displacement of the drill string microelement, s is the arc length of the drill string microelement, t is the time, μ is the friction coefficient between the drill string and the well wall, and ρ is s represents the buoyancy of the drill string, F represents the contact positive pressure between the drill string and the well wall, T represents the axial force of the drill string, k b represents the wellbore curvature, k α Well inclination change rate, represents the rate of change of well inclination azimuth, α represents the average well inclination angle, and c represents the drilling fluid damping coefficient.

[0059] In addition to being parameters of unknown quantities, the above parameters can all be set with initial boundary conditions, that is, given initial values. F represents the contact normal pressure between the drill string and the well wall. When the drill string is simulated to be horizontal, F is its gravity.

[0060] The derivation process of the drill string axial vibration control model is as follows:

[0061] Examples of theoretical models involved are as follows:

[0062] Take any micro-element segment on the drill string and regard it as a rigid body. Consider only the dynamic effect in the axial direction of the drill string, and establish the dynamic model of the micro-element segment in the axial direction and the equilibrium model in the direction of the principal normal and the secondary normal respectively:

[0063]

[0064] Where:

[0065] T——axial force on drill string microelement, N;

[0066] s——arc length of drill string micro-element segment, m;

[0067] f——friction between drill string microelement and well wall, N;

[0068] c——drilling fluid damping coefficient, dimensionless;

[0069] u——axial displacement of the drill string micro-element section, m;

[0070] t——time, s;

[0071] ρ s ——buoyant weight of drill string, N / m;

[0072] A——microelement cross-sectional area of ​​drill string, m 2 ;

[0073] α——average well inclination angle, degrees;

[0074] k α ——Rate of change of well inclination angle;

[0075] ——the rate of change of well inclination azimuth;

[0076] k b — wellbore curvature;

[0077] F n 、F b ——The components of the normal contact pressure F between the drill string and the wellbore wall in the main normal and sub-normal directions, N. The following relationship is satisfied:

[0078] F 2 =F n 2 +F b 2 (2)

[0079] The friction force f adopts the Coulomb friction calculation model, and different friction factors can be selected according to actual conditions. The calculation formula of friction force is:

[0080] f=Fμ (3)

[0081] μ——Friction coefficient between drill string and well wall.

[0082] According to the material mechanics, the stress-strain formula of the tie rod is:

[0083]

[0084] Where:

[0085] E is the elastic modulus of the drill string.

[0086] Substituting the above formula, we can get the complete drill string axial vibration control model:

[0087]

[0088] For the convenience of research, the vibration drag reduction tool is regarded as a point on the drill string, and the excitation force form of the vibration drag reduction tool is simplified to sinusoidal excitation:

[0089] F tool =F a |sin(wt)| (6)

[0090] Where:

[0091] F tool ——excitation force generated by the vibration drag reduction tool, N;

[0092] F a ——Amplitude of the excitation force generated by the vibration drag reduction tool, N;

[0093] w is the frequency of the excitation force generated by the vibration drag reduction tool, Hz.

[0094] Incorporating model (6) into the continuity condition of model (5), the initial conditions, boundary conditions and other continuity conditions under different circumstances can be combined to perform numerical solutions. Under the condition of known excitation force, the displacement, axial force, friction force, etc. of the drill string at different positions and times under different friction coefficients can be solved.

[0095] The above embodiments are examples for illustrating the present invention. Other different forms of changes or modifications may be made based on the above embodiments, including but not limited to using a casing with a certain curvature to simulate the actual wellbore trajectory (achieved by changing the curvature of the casing), applying axial force at both ends of the simulated drill string to simulate different drill string axial forces, pre-treating the inner wall of the casing to simulate different well wall conditions, etc., so as to more accurately simulate the actual conditions of the drilling wellbore and drill string.

[0096] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0097] The above-mentioned technical solutions are only several implementation methods of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the principles disclosed in the present invention, and they are not limited to the technical solutions described in the above-mentioned specific embodiments of the present invention. Therefore, the above description is only preferred and does not have a restrictive meaning.

Claims

1. A drill string drag reduction test device, characterized in that: The invention comprises a simulated drill string, a casing and a vibrator. The outer diameter of the simulated drill string is smaller than the inner diameter of the casing. The simulated drill string is slidably connected to the bottom wall of the casing under the action of gravity, and two ends of the simulated drill string extend out of two ends of the casing respectively. The two ends of the simulated drill string are respectively connected to a driving motor and a slider through a first tension and compression sensor and a second tension and compression sensor. The vibrator is arranged on the simulated drill string and is used to excite the reciprocating motion of the simulated drill string.

2. The drill string drag reduction experimental device according to claim 1, characterized in that: The vibrator is a pneumatic vibrator, and the vibration frequency and amplitude can be adjusted by controlling the air volume of the air compressor.

3. The drill string drag reduction experimental device according to claim 1, characterized in that: A computer for monitoring the sensor data is also included.

4. The drill string drag reduction experimental device according to claim 1, characterized in that: It also includes a base provided with a guide rail, the sleeve is fixedly supported on the base through a clip, the push motor is fixedly connected to the base, and the slide block is slidably connected to the guide rail.

5. The drill string drag reduction experimental device according to claim 1, characterized in that: The two ends of the simulated drill string are respectively connected to the first tension and compression sensor and the second tension and compression sensor through a connecting assembly; the connecting assembly includes an adapter, a connecting rod and a chuck; the simulated drill string is connected to the first tension and compression sensor or the second tension and compression sensor through the adapter, the tension and compression sensor is connected to the connecting rod, and the connecting rod is connected to the pushing motor or the slider through the chuck.

6. The drill string drag reduction experimental device according to any one of claims 1 to 5, characterized in that: A displacement sensor is provided at any end of the simulated drill string.

7. The drill string drag reduction test device according to claim 6, characterized in that: The displacement sensing device comprises a reflective plate and a laser distance measuring sensor. The reflective plate is vertically and fixedly connected to the simulated drill string, and the laser distance measuring sensor is directly opposite to the reflective plate and fixedly connected to the casing.

8. A drill string drag reduction test method, characterized in that: The drill string drag reduction experimental device as described in any one of claims 1 to 5 is used to collect the static friction before drag reduction and the dynamic friction after drag reduction, respectively, and the drag reduction efficiency is calculated based on the static friction and the dynamic friction. The drag reduction efficiency is equal to the difference between the static friction and the dynamic friction divided by the static friction.

9. The drill string drag reduction test method according to claim 8, characterized in that: The static friction collection process is as follows: the driving motor continuously increases the axial force acting on the simulated drill string. Under the premise of ensuring that the simulated drill string does not move, the maximum pressure difference between the first tension and compression sensor and the second tension and compression sensor is the static friction before drag reduction.

10. The drill string drag reduction test method according to claim 8, characterized in that: The dynamic friction collection process is as follows: start the vibrator, simulate the static friction between the drill string and the casing, which will be converted into dynamic friction under the excitation of the vibrator, and simulate the reciprocating vibration of the casing. The pressure difference between the first tension and compression sensor and the second tension and compression sensor at both ends of the simulated drill string after vibration is similar to a sinusoidal change form, and then the equivalent pressure difference is obtained by integral calculation, which is the dynamic friction after drag reduction.

11. A friction coefficient correction method, characterized in that: A drill string axial vibration control model is established, initial boundary conditions are set, and finite element method is used to solve the drill string displacement and friction force in the axial vibration control model under different friction coefficients as model calculation results; the drill string drag reduction experimental device as described in claim 6 is used to collect the displacement and friction force of the simulated drill string under the same initial boundary conditions as simulation experimental results; the model calculation results and the simulation experimental results are compared, and the friction coefficient corresponding to the model calculation result with the smallest error and the error within the threshold range is used as the corrected friction coefficient.

12. The friction coefficient correction method according to claim 11, characterized in that: The drill string axial vibration control model is as follows: Where E is the elastic modulus of the drill string, A is the cross-sectional area of ​​the drill string microelement, u is the axial displacement of the drill string microelement, s is the arc length of the drill string microelement, t is the time, μ is the friction coefficient between the drill string and the well wall, and ρ is s represents the buoyancy of the drill string, F represents the contact positive pressure between the drill string and the well wall, T represents the axial force of the drill string, k b represents the wellbore curvature, k α Well inclination change rate, represents the rate of change of well inclination azimuth, α represents the average well inclination angle, and c represents the drilling fluid damping coefficient.

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