Drill column torsional pendulum drilling control method for tight gas well and medium
By carefully describing the method of drill string torsional pendulum movement, calculating the optimal control parameters and applying periodic rotation torque, the problem of precise acquisition of drill string torsional pendulum movement parameters in tight gas well development is solved, and the effect of effectively reducing friction resistance and maintaining the stability of the tool surface at the bottom of the well is achieved.
Patent Information
- Application Number
- CN202311745685.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-18
- Publication Date
- 2025-06-20
AI Technical Summary
The prior art lacks a detailed description of the torsional pendulum movement of the drill string under the conditions of tight gas well development, and cannot obtain accurate torsional pendulum system parameters, making it difficult to effectively reduce friction resistance and not affect the bottom-hole tool surface.
By calculating friction and friction torque based on the torsional swing of the drill string, drilling fluid performance data under safe drilling conditions is obtained, the stress model and differential equation of the overall and micro-corresponding torque movement of the drill string are constructed, and the optimal control parameters are calculated using the finite difference method to realize the periodic rotation torque control of the drill string.
The fine control of the torsional movement of the drill string is achieved, the axial friction resistance of the drill string is reduced, the stability of the bottom-hole tool surface is ensured, and the drilling efficiency and effect are improved.
Smart Images
Figure CN120175307A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of drilling control, and particularly relates to a drill string torsional oscillation drilling control method and medium for tight gas wells. Background Art
[0002] During the drilling process of horizontal wells in the long horizontal section of tight gas, reducing friction and drag enables the drilling operation to apply a greater bit weight, which is beneficial to the rapid drilling of the horizontal section. Wellbore cleaning can further reduce the friction torque in the horizontal section. At present, on-site, more consideration is given to the torsional oscillation movement of the drill string, and a supporting drill string control system is adopted for drilling operations.
[0003] Drill string torsional oscillation drilling combines two methods of rotary drilling and sliding drilling. On the one hand, it can effectively reduce the friction during sliding drilling in extended reach wells, etc. On the other hand, it can increase the effective bit weight and maintain the stability of the tool face. When the drill string undergoes torsional oscillation, it is particularly crucial to calculate the positions where the forward and reverse torques of the surface top drive are transmitted to the drill string, and the position where the screw reverse torque is transmitted to the pipe string. When these two positions do not intersect, the screw is not affected by the torque of the upper drill string, and thus the tool face can be maintained stable. However, if the surface torque is too small, it will not play a role in reducing friction. Therefore, in order to effectively reduce friction without affecting the bottom hole tool face, reasonable surface torque and other parameters must be determined. In the prior art, there is a lack of a refined description scheme for the torsional oscillation movement of the drill string under the development conditions of tight gas wells, and accurate torsional oscillation system parameters cannot be obtained. Summary of the Invention
[0004] To solve the above problems, the present invention provides a drill string torsional oscillation drilling control method for tight gas wells. The specific technical solutions are as follows:
[0005] S1: Calculate the drill string friction force and drill string friction torque for tight gas wells based on the drill string torsional oscillation drag reduction mechanism;
[0006] S2: Obtain the drilling fluid performance data under safe drilling conditions;
[0007] S3: Construct a force model of the upper drill string during the overall torsional oscillation movement of the drill string;
[0008] S4: Construct a differential equation for the micro-element torsional oscillation movement of the drill string, set the initial conditions and boundary conditions of the drill string torsional oscillation torque and the axial mechanical penetration rate, and calculate the optimal control parameters based on the force model through the finite difference method;
[0009] S5: Obtain the output torque according to the optimal control parameters, and calculate the reverse torque transmission length;
[0010] S6: Apply a periodic rotational torque to the drill string to drive the drill string to rotate forward and backward alternately.
[0011] Furthermore, the drill string friction force is the sum of the axial friction force of the drill string under the action of bristle deformation and the axial friction force of the drill string under the viscous action of the drilling fluid, and the drill string friction torque is the sum of the drill string friction torque under the action of bristle deformation and the drill string friction torque under the viscous action of the drilling fluid.
[0012] Furthermore, the calculation methods for the axial friction force and the friction torque of the drill string under the action of bristle deformation are as follows:
[0013] F d = [σ1z(t + Δt) + σ2z′(t + Δt)]cosβ
[0014] t d = [σ1z(t + Δt) + σ2z′(t + Δt)]Rsinβ
[0015] where σ1 represents the bristle deformation stiffness coefficient, σ2 represents the bristle deformation damping coefficient, z(t + Δt) represents the bristle deformation amount, z′(t + Δt) represents the bristle deformation rate, R represents the drill string radius, and β represents the angle between the bristles after deformation and the wellbore axis;
[0016] The bristles refer to the micro - protrusions on the wellbore wall surface.
[0017] Furthermore, the calculation methods for the axial friction force and the friction torque of the drill string under the viscous action of the drilling fluid are as follows:
[0018]
[0019]
[0020] where τ represents the structural force of the drilling fluid, v represents the axial movement speed of the drill string, ω represents the drill string rotation speed, D w represents the wellbore diameter, and dx represents the drill string length.
[0021] Furthermore, the force model of the upper drill string is expressed as follows:
[0022]
[0023]
[0024] where, represents the axial force of the drill string element, represents the moment of the drill string element, represents the normal contact force between the drill string element and the wellbore wall, ρ sIt represents the floating weight of the drill string in the drilling fluid. A represents the cross-sectional area of the drill string, ds represents an infinitesimal element of the drill string, s represents the length of the drill string from the bit at the bottom of the well, f represents the axial friction force of the drill string, f1 represents the axial friction force component of the viscous effect of the drilling fluid, f2 represents the circumferential friction force component of the viscous effect of the drilling fluid, t represents the frictional torque of the drill string, μ represents the axial displacement, and θ represents the rotation angle.
[0025] Furthermore, the differential equation of the torsional pendulum motion of the infinitesimal element of the drill string is expressed as follows:
[0026]
[0027]
[0028] In the formula: G represents the shear modulus of the drill string, E represents the elastic modulus of the drill string, I p represents the polar moment of inertia of the drill string, D represents the outer diameter of the drill string, μ a represents the axial component of the friction coefficient μ, μ t represents the circumferential component of the friction coefficient μ, and ρ represents the density of the drill string.
[0029] Furthermore, the axial and circumferential components of the friction coefficient μ are calculated as follows:
[0030]
[0031]
[0032] Among them, v a represents the axial movement rate of the contact point between the drill string and the wellbore, v t represents the torsional rate of the contact point between the drill string and the wellbore in the circumferential direction.
[0033] Furthermore, the specific implementation process of applying a periodic rotational torque to the drill string to drive the drill string to rotate forward and backward alternately is as follows:
[0034] A1: Drive the main shaft to rotate forward through the top drive system to generate a positive torque until the positive torque reaches the peak value, and then stop the forward rotation;
[0035] A2: Drive the main shaft to rotate backward to release the positive torque. After the positive torque is released, output to establish a negative torque until the negative torque reaches the peak value, and then stop the backward rotation;
[0036] A3: Drive the main shaft to rotate forward to release the negative torque, and return to step A1, then apply a periodic rotational torque to the rotating column to drive the drill string to rotate forward and backward alternately.
[0037] Furthermore, the set peak value of the rotational torque is such that the torsional pendulum effect on the drill string does not break through the static friction zone.
[0038] The present invention also provides a computer storage medium, on which a control program for drill string torsional oscillation drilling in a tight gas well is stored. When the control program for drill string torsional oscillation drilling in a tight gas well is executed by a processor, the steps of the control method for drill string torsional oscillation drilling in a tight gas well as described above are implemented.
[0039] The beneficial effects of the present invention are as follows:
[0040] The present invention applies positive and negative torques to the drill string through a top drive to achieve the repeated clockwise and counterclockwise torsional movements of the drill string. At the same time, parameters such as screw torque transmission are obtained by monitoring the torsional oscillation movement of the drill string, and the torque distribution at different positions is analyzed and calculated to obtain optimal control parameters, so as to control the top drive torque to be transmitted only to a certain position of the drill string without affecting the stability of the tool face. Description of the Drawings
[0041] Figure 1 It is a schematic diagram of the overall process flow of the method of the present invention.
[0042] Figure 2 It is a diagram showing the changes in static friction and dynamic friction before and after the movement of the drill string.
[0043] Figure 3 It is a schematic diagram showing the influence of different rotational speeds on the axial friction force of the drill string.
[0044] Figure 4 It is a schematic diagram of the force analysis of a drill string microelement.
[0045] Figure 5 It is a schematic diagram of the execution process of the forward and reverse alternating rotation of the drill string. Detailed Embodiments
[0046] In the following description, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.
[0047] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art, or the orientation or positional relationship in which the product of the invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.
[0048] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "arrangement" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0049] Embodiment 1
[0050] Embodiment 1 of the present invention discloses a control method for drill string torsional oscillation drilling in tight gas wells. Specifically, in drill string torsional oscillation drilling, positive and negative torques are applied to the drill string through the top drive to achieve the repeated clockwise and counterclockwise torsional movement of the drill string. At the same time, the top drive torque is controlled to be transmitted only to a certain position of the drill string, and this position will not affect the stability of the tool face, so that the static friction of the upper drill string is transformed into dynamic friction, reducing the axial friction resistance of the drill string.
[0051] During the drilling process, this torsional oscillation movement divides the downhole drill string into three regions: the drill string torsional oscillation region of the surface torque (abbreviated as the S region), the static friction region where the pipe string does not rotate (abbreviated as the F region), and the counter-torque action region of the downhole motor (abbreviated as the R region).
[0052] Among the above three action regions, the S region represents the diffusion range of the positive and negative torques applied by the top drive in the downhole drill string. The torsional oscillation movement of the drill string in this region changes the relative movement form between the drill string and the wellbore wall, transforming static friction into dynamic friction and greatly reducing the axial friction resistance of the drill string; the F region is the static friction region, and there is an optimal length to maintain the stability of the downhole steering motor tool face, which is conducive to realizing the control and adjustment of the drilling azimuth; the R region represents the influence range of the counter-torque of the downhole power drill on the lower drill string, reflecting the output torque of the screw corresponding to the friction between the drill string and the wellbore wall.
[0053] As Figure 1 shown, specifically as follows:
[0054] S1: Calculate the drill string friction force and drill string friction torque in tight gas wells based on the drill string torsional oscillation drag reduction mechanism.
[0055] Based on the contact process between the drill string and the wellbore wall, the following explanations are made for the calculation of the drill string friction force under the drilling and production conditions of tight gas wells:
[0056] 1. At the microscopic level, there are a large number of micro-protrusions on the wellbore wall surface, and the micro-protrusions are called "bristles";
[0057] 2. The bristles on the wellbore wall surface satisfy elastic deformation;
[0058] 3. The curved arc surface between the drill string and the wellbore wall is simplified to a plane contact at the microscopic level;
[0059] 4. The drill string only experiences sliding friction with the wellbore wall.
[0060] Based on this, according to the LuGre friction model, the deformation of the bristles on the wellbore wall is related to the relative velocity between the drill string and the wellbore wall and the stiffness of the bristles. Under the action of the rotation and sliding of the drill string, the bristle deformation can be represented by an elastic-damping element. The deformation amount z is obtained by superimposing the axial movement and tangential movement of the drill string. The axial friction force and friction torque of the drill string under the action of bristle deformation at any moment are calculated as follows:
[0061] F d = [σ1z(t + Δt) + σ2z′(t + Δt)]cosβ
[0062] t d = [σ1z(t + Δt) + σ2z′(t + Δt)]Rsinβ
[0063] Where σ1 represents the bristle deformation stiffness coefficient, σ2 represents the bristle deformation damping coefficient, z(t + Δt) represents the bristle deformation amount, z′(t + Δt) represents the bristle deformation rate, R represents the drill string radius, and β represents the angle between the deformed bristles and the wellbore axis.
[0064] When the properties of the drilling fluid, wellbore size, and drill string are fixed, the axial viscous resistance and circumferential friction torque acting on the drill string during its movement in the drilling fluid only depend on the relative velocity between the two. Assuming that the flow of the drilling fluid in the annulus is laminar, the axial friction force and drill string friction torque under the action of the drilling fluid viscosity are calculated as follows:
[0065]
[0066]
[0067] Where τ represents the structural force of the drilling fluid, v represents the axial movement velocity of the drill string, ω represents the drill string rotation speed, D w represents the wellbore diameter, and dx represents the drill string length.
[0068] Based on the above calculations, for the drill string during periodic motion, the average axial friction force and friction torque acting on the drill string within one period are calculated as follows:
[0069]
[0070]
[0071] Where F f represents the average axial friction force of the drill string, T f represents the average friction torque of the drill string, n represents the number of samples, and t i represents the sampling time.
[0072] The average axial frictional force of the drill string due to bristle deformation and the viscous effect of the drilling fluid is calculated as follows:
[0073]
[0074]
[0075] Similarly, the calculation of the average frictional torque of the drill string due to bristle deformation and the viscous effect of the drilling fluid is as follows:
[0076]
[0077]
[0078] Where, F fx represents the axial frictional force of the drill string caused by bristle deformation, and F vx represents the axial frictional force of the drill string caused by the viscous effect of the drilling fluid. T d represents the circumferential frictional torque of the drill string caused by bristle deformation, and T v represents the circumferential frictional torque of the drill string caused by the viscous effect of the drilling fluid.
[0079] When the drill string reaches the critical state from the stationary state to start moving, the force applied to the drill string is equal in magnitude to the static frictional force it receives. When the force applied to the drill string overcomes the maximum static frictional force, the frictional force received by the drill string immediately changes to dynamic frictional force. As Figure 2 shown, the static frictional force is 25% higher than the dynamic frictional force.
[0080] S2: Obtain the performance data of the drilling fluid under safe drilling conditions.
[0081] As Figure 3 shown, the percentage of the axial frictional force of the drill string in the Coulomb frictional force decreases rapidly and gradually stabilizes with the increase of the rotation speed under the rotating state, indicating that keeping the drill string rotating can effectively reduce the axial frictional force of the drill string. When the drill string starts to rotate, the axial frictional force drops rapidly, but as the rotation speed of the drill string increases and reaches a certain value, the axial frictional force gradually stabilizes. At the same time, the faster the mechanical drilling rate, the higher the axial frictional force of the drill string, because the axial speed of the drill string is high, the deformation amount of the bristles in the axial direction increases, resulting in an increase in the axial frictional force component.
[0082] Under the condition of ensuring safe drilling, reducing the positive bottomhole pressure difference can effectively improve the mechanical drilling rate. By appropriately reducing the density of the drilling fluid, reducing the yield value and plastic viscosity of the drilling fluid can effectively reduce the positive bottomhole pressure difference and improve the mechanical drilling rate.
[0083] Therefore, during the directional drilling process of tight gas wells, the density of the drilling fluid and the yield value of the drilling fluid can be appropriately reduced in stages according to the actual situation.
[0084] S3: Construct the force model of the upper drill string during the overall torsional oscillation motion of the drill string;
[0085] When a certain amount of positive and negative torques are applied to the drill string to perform periodic torsional oscillation motion, the force condition of the upper drill string is different from that under normal working conditions. In this embodiment, the relationship between the torsional oscillation motion and the drill string is analyzed through the force model to determine the optimal ground torsional oscillation motion parameters.
[0086] As Figure 4 shown, the force model, that is, the force and moment balance equations of the drill string micro-elements are expressed as follows:
[0087]
[0088]
[0089] Among them, represents the axial force of the drill string micro-element, represents the moment of the drill string micro-element, represents the normal contact force between the drill string micro-element and the wellbore wall, ρ s represents the buoyant weight of the drill string in the drilling fluid, A represents the cross-sectional area of the drill string, ds represents the drill string micro-element, s represents the length of the drill string from the bottom hole bit, f represents the axial friction force of the drill string, f1 represents the friction force component of the drilling fluid viscosity in the axial direction, f2 represents the friction force component of the drilling fluid viscosity in the circumferential direction, t represents the friction torque of the drill string, μ represents the axial displacement, and θ represents the rotation angle.
[0090] For the unit vectors in the above formula
[0091]
[0092] Among them, α represents the well inclination angle, represents the well inclination azimuth angle, represents the average well inclination angle, k α represents the well inclination angle change rate, represents the well inclination azimuth angle change rate, k b represents the wellbore curvature.
[0093] For the normal contact force of the drill string micro-element:
[0094]
[0095] Among them, F t represents the component of the axial force of the drill string micro-element in the direction, and μ t represents the circumferential component of the friction coefficient μ.
[0096] S4: Establish the differential equation for the torsional pendulum motion of the drill string element, the initial conditions and boundary conditions of the torsional pendulum torque and the axial mechanical drilling rate of the drill string. Based on the force model, calculate the optimal control parameters by the finite difference method.
[0097] In this embodiment, the differential equation for the torsional pendulum motion of the drill string element is expressed as follows:
[0098]
[0099]
[0100] In the formula: G represents the shear modulus of the drill string, E represents the elastic modulus of the drill string, I p represents the polar moment of inertia of the drill string, D represents the outer diameter of the drill string, μ a represents the axial component of the friction coefficient μ, μ t represents the circumferential component of the friction coefficient μ, and ρ represents the density of the drill string.
[0101] The axial and circumferential components of the friction coefficient μ are calculated as follows:
[0102]
[0103]
[0104] Among them, v a represents the axial movement rate of the contact point between the drill string and the wellbore wall, and v t represents the torsional rate of the contact point between the drill string and the wellbore wall in the circumferential direction.
[0105] After giving the initial conditions and boundary conditions of the torsional pendulum torque and the axial mechanical drilling rate of the drill string, the above equation is solved by the finite difference method to analyze the mechanical characteristics of the torsional pendulum drilling of the drill string, and the optimal control parameters can be determined.
[0106] S5: Obtain the output torque according to the optimal control parameters and calculate the reverse torque transmission length.
[0107] The positive displacement motor converts the hydraulic energy of the drilling fluid into the mechanical energy for the drill bit to break rock by rotation, and its output torque is proportional to the pressure difference generated by the positive displacement motor:
[0108]
[0109] Among them, T t represents the output torque of the positive displacement motor, Δp represents the working pressure drop of the positive displacement motor, and q represents the displacement per revolution of the positive displacement motor.
[0110] During the drilling process, the positive displacement motor outputs torque through the rotor and transmits it to the drill bit. At the same time, a reaction torque of equal magnitude and opposite direction acts on the stator. During sliding drilling, the reaction torque of the positive displacement motor is transmitted upward along the bottomhole drill string to a certain point where it becomes zero. Above this point, the drill string does not rotate, and below this point is the influence range of the reaction torque of the downhole motor on the lower drill string. During the upward transmission of the reaction torque along the drill string, it cancels out the frictional torque of the drill string. At the same time, since the lower drill string can only twist by a small angle, it is called the reaction angle of the downhole motor, and its calculation formula is:
[0111]
[0112] Among them, L represents the transmission length of the reaction torque.
[0113] S6: Apply a periodic rotational torque to the drill string to drive the drill string to rotate forward and backward alternately.
[0114] As Figure 5 shown, the specific implementation process is as follows:
[0115] Drive the main shaft to rotate forward through the top drive system to generate a positive torque until the positive torque reaches the peak value, and then stop the forward rotation;
[0116] Drive the main shaft to rotate backward to release the positive torque. After the positive torque is released, output to establish a reverse torque until the reverse torque reaches the peak value, and then stop the reverse rotation;
[0117] Drive the main shaft to rotate forward to release the reverse torque, and return to step A1, then apply a periodic rotational torque to the rotating column to drive the drill string to rotate forward and backward alternately.
[0118] In this embodiment, the set peak value of the rotational torque enables the torsional pendulum effect on the drill string not to break through the static friction zone, realizing the stability of the directional tool face and ensuring the sliding directional effect.
[0119] In this embodiment, the rotation angle can also be controlled by setting the forward and reverse angles or the number of turns of the top drive.
[0120] Embodiment 2
[0121] Embodiment 2 of the present invention discloses a computer storage medium, on which a control program for drill string torsional pendulum drilling for tight gas wells is stored. When the control program for drill string torsional pendulum drilling for tight gas wells is executed by a processor, it realizes the steps of the control method for drill string torsional pendulum drilling for tight gas wells described in the above Embodiment 1.
[0122] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new method or process step or any new combination disclosed.
Claims
1. A drilling string torsional oscillation drilling control method for tight gas wells, characterized in that, Including: S1: Calculate the drill string friction force and drill string friction torque in tight gas wells based on the drill string torsional oscillation drag reduction mechanism; S2: Obtain the drilling fluid performance data under safe drilling conditions; S3: Construct the force model of the upper drill string during the overall torsional oscillation movement of the drill string; S4: Construct the differential equation of the drill string micro-element torsional oscillation movement, set the initial conditions and boundary conditions of the drill string torsional oscillation torque and axial mechanical drilling rate, and calculate the optimal control parameters by the finite difference method based on the force model; S5: Obtain the output torque according to the optimal control parameters and calculate the reverse torque transmission length; S6: Apply a periodic rotational torque to the drill string to drive the drill string to rotate forward and backward alternately.
2. The drilling string torsional oscillation drilling control method for tight gas wells according to claim 1, characterized in that, The drill string friction force is the sum of the axial friction force of the drill string under the action of bristle deformation and the axial friction force of the drill string under the viscous action of the drilling fluid, and the drill string friction torque is the sum of the drill string friction torque under the action of bristle deformation and the drill string friction torque under the viscous action of the drilling fluid.
3. The drilling string torsional oscillation drilling control method for tight gas wells according to claim 2, characterized in that, The calculation of the axial friction force and drill string friction torque of the drill string under the action of bristle deformation is as follows: F d = [σ1z(t + Δt) + σ2z′(t + Δt)] cosβ t d = [σ1z(t + Δt) + σ2z′(t + Δt)]Rsinβ Wherein, σ1 represents the bristle deformation stiffness coefficient, σ2 represents the bristle deformation damping coefficient, z(t + Δt) represents the bristle deformation amount, z′(t + Δt) represents the bristle deformation rate, R represents the drill string radius, and β represents the angle between the bristle deformation and the wellbore axis; The bristles refer to the micro-convex bodies on the wellbore surface.
4. The drilling string torsional oscillation drilling control method for tight gas wells according to claim 2, characterized in that, The calculation of the axial friction force and drill string friction torque of the drill string under the viscous action of the drilling fluid is as follows: Among them, τ represents the structural force of the drilling fluid, v represents the axial movement speed of the drill string, ω represents the rotational speed of the drill string, D w represents the wellbore diameter, and dx represents the drill string length.
5. The drilling string torsional oscillation drilling control method for tight gas wells according to claim 1, characterized in that, The force model of the upper drill string is expressed as follows: Among them, represents the axial force of the drill string element, represents the moment of the drill string element, represents the normal contact force between the drill string element and the wellbore wall, ρ s represents the buoyant weight of the drill string in the drilling fluid, A represents the cross-sectional area of the drill string, ds represents the drill string element, s represents the length of the drill string from the bottom hole bit, f represents the axial friction force of the drill string, f1 represents the friction force component in the axial direction due to the viscosity of the drilling fluid, f2 represents the friction force component in the circumferential direction due to the viscosity of the drilling fluid, t represents the friction torque of the drill string, μ represents the axial displacement, and θ represents the rotation angle.
6. The drilling string torsional oscillation drilling control method for tight gas wells according to claim 5, characterized in that, The differential equation of the drill string micro-element torsional oscillation movement is expressed as follows: Where: G represents the shear modulus of the drill string, E represents the elastic modulus of the drill string, I p represents the polar moment of inertia of the drill string, D represents the outer diameter of the drill string, μ a represents the axial component of the friction coefficient μ, μ t represents the circumferential component of the friction coefficient μ, and ρ represents the density of the drill string.
7. The drilling string torsional oscillation drilling control method for tight gas wells according to claim 6, characterized in that, The calculation of the components of the friction coefficient μ in the axial and circumferential directions is as follows: Among them, v a represents the axial movement rate of the contact point between the drill string and the wellbore wall, and v t represents the torsional rate of the contact point between the drill string and the wellbore wall in the circumferential direction.
8. The drill string torsional oscillation drilling control method for tight gas wells according to claim 1, wherein, The specific execution process of applying a periodic rotational torque to the drill string to drive the drill string to rotate forward and backward alternately is as follows: A1: Drive the main shaft to rotate forward through the top drive system to generate a positive torque until the positive torque reaches the peak value, and then stop rotating forward; A2: Drive the main shaft to rotate backward to release the positive torque. After the positive torque is released, output and establish a reverse torque until the reverse torque reaches the peak value, and then stop rotating backward; A3: Drive the main shaft to rotate forward to release the reverse torque, and return to step A1, and then apply a periodic rotational torque to the rotating column to drive the drill string to rotate forward and backward alternately.
9. The drill string torsional oscillation drilling control method for tight gas wells according to claim 8, wherein, The set peak value of the rotational torque is such that the torsional oscillation effect on the drill string does not break through the static friction zone.
10. A computer storage medium, wherein, A drill string torsional oscillation drilling control program for tight gas wells is stored on the computer storage medium. When the drill string torsional oscillation drilling control program for tight gas wells is executed by a processor, the steps of the drill string torsional oscillation drilling control method according to any one of claims 1-9 are implemented.