Ultra-deep well large-annulus flexible righting transverse vibration reduction method

Abstract

The invention provides an ultra-deep well large annulus flexible righting transverse vibration reduction method, which belongs to the technical field of well drilling and drilling, and comprises the following steps of: inputting pre-drilling well drilling engineering information, and calculating a whole well section drill string vibration distribution form based on an established drill string finite element dynamic model; the tripping-in positions and the number of the flexible stabilizers and the layer number and the compression space of plate springs in the flexible stabilizers are designed, and an initial vibration reduction scheme is generated; comparing the real-time vibration data with the predicted vibration distribution pattern, carrying out real-time risk assessment, carrying out dynamic optimization on the initial vibration reduction scheme according to the real-time risk assessment, adjusting the tripping-in position and number of flexible stabilizers, the number of plate spring layers and the compression space, and generating an optimized real-time vibration reduction scheme; a flexible stabilizer is put in the designated position of the drill column; when the drill column transversely vibrates and collides with the well wall, the buffer block of the flexible stabilizer is pressed, the plate spring is driven to generate radial elastic deformation, part of radial impact kinetic energy is converted into elastic potential energy of the plate spring to be stored, and radial vibration reduction is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of drilling and prospecting technology, and relates to a flexible centralizing transverse vibration reduction method for large annulus of ultra-deep well. BACKGROUND

[0002] The current oil and gas reservoir occurrence characteristics are regularly distributed in deep strata, and the proportion of deep strata resources in proven reserves is increasing year by year. Developing deep wells and ultra-deep wells has become an inevitable trend of resource development. The increase in well depth means the increase in wellbore size, but the large annular space between the drill string and the well wall caused by large-size wellbore leads to severe transverse vibration and alternating stress, greatly increasing the risk of drill string fatigue failure. Secondly, the cumulative effect of ultra-long drill pipe gravity load causes uncontrollable spiral buckling of the bottom hole assembly, resulting in a sharp drop in drilling pressure transmission efficiency and instability of downhole tool function, which seriously restricts the efficiency and safety of deep well operation. The system-level risk caused by the coupling of the above mechanical behaviors needs to be resolved through structural innovation and dynamic control technology breakthrough. In conventional drilling operations, stabilizers (centralizers) are often used to constrain the transverse displacement of the drill string at a specific position, achieving the centralizing effect of the drill string. However, the continuous hard contact between the rigid damping interface and the well wall causes high-frequency impact, leading to a sharp increase in drill string composite stress concentration and casing damage risk, making it difficult to meet the needs of large annulus working conditions in ultra-deep wells.

[0003] The problem of drill string transverse vibration is particularly prominent in deep and ultra-deep wells during actual drilling. Not only does it affect the construction efficiency, but it also poses a serious safety risk. Frequent and severe vibration leads to alternating stress of the drill string, causing fatigue failure of the drill string, thereby increasing the construction cost and causing significant economic losses. The existing method to reduce transverse vibration is to use stabilizers to constrain the transverse displacement of the drill string at a specific position, achieving the centralizing effect of the drill string in the casing. However, the continuous hard contact between the rigid damping interface and the well wall causes high-frequency impact, leading to a sharp increase in drill string composite stress concentration and casing damage risk, making it difficult to meet the needs of large annulus working conditions in ultra-deep wells. In view of the above factors, the inventors propose an integrated drill string damping method for deep and ultra-deep wells, which converts drill string vibration energy into elastic potential energy of leaf springs and drill string axial pressure, achieving the effect of limiting the drill string in deep and ultra-deep wells, and designing a flexible stabilizer for the drill string at the bottom of the well to utilize this part of destructive energy in the field of deep well speed-up, turning harm into benefit, in order to make new breakthroughs in the field of deep well speed-up. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application proposes a flexible centralizing transverse vibration reduction method for large annulus of ultra-deep well, comprising the following steps: S1, the computer system inputs drilling engineering information, calculates the vibration distribution pattern of the whole well section drill string based on the established drill string finite element dynamics model, designs the running position, number of flexible stabilizers, and the number of leaf springs and compression space in each flexible stabilizer according to the vibration distribution pattern, and generates an initial vibration reduction scheme; S2, in the drilling operation process, the drilling string vibration data is collected in real time by the logging instrument and transmitted to the computer system; the computer system compares the real-time vibration data with the vibration distribution pattern predicted in step S1, performs real-time risk assessment, and dynamically optimizes the initial vibration reduction scheme according to the real-time vibration reduction scheme, adjusts the running position, number, number of leaf springs and compression space of the flexible stabilizer, and generates an optimized real-time vibration reduction scheme; S3, according to the real-time vibration reduction scheme, the flexible stabilizer is run at the specified position of the drill string; when the drill string occurs lateral vibration and collides with the well wall, the buffer block of the flexible stabilizer is pressed, the leaf spring is driven to produce radial elastic deformation, part of the radial impact kinetic energy is converted into the elastic potential energy of the leaf spring, and radial vibration reduction is realized; at the same time, in the compression and rebound process of the leaf spring, part of the radial impact force is converted into downward axial impact force, which acts on the drill string, and axial pressure stabilization is realized at the same time.

[0005] Further, in step S1, the computer calculates the mass matrix M, stiffness matrix K and damping matrix C of the whole well drill string according to the input well depth, borehole size, drill string combination, substitutes into the dynamics equation, and combines the boundary conditions and load to solve the dynamics equation by Newmark-β method numerical algorithm to obtain the displacement U, velocity and acceleration of each node on the drill string at each time in the future drilling process.

[0006] Further, the drill string finite element dynamics model is established by finite element method, specifically: the drill string is discretized into multiple double-node three-dimensional Timoshenko beam elements, each node has six degrees of freedom; the mass matrix and stiffness matrix of each element are derived based on Lagrange equation, and the total mass matrix M and total stiffness matrix K of the system are integrated; the dynamics equation of the system is represented as: ; wherein, , , and are the generalized acceleration, velocity, displacement and external force matrix of all nodes of the whole well drill string. , and The total mass matrix, the total damping matrix and the total stiffness matrix of the assembled full-hole drilling string respectively, and the Newmark-beta method is used for numerical solution to obtain the vibration distribution pattern of the full-hole drilling string.

[0007] Further, after the dynamic model is established, the linear stiffness matrix of the double-node three-dimensional Timoshenko beam element is The linear stiffness matrix is derived by the following energy integral formula: ; E is the Young's modulus, G is the shear modulus, A is the cross-sectional area, I x and I yz are the torsional and bending inertia respectively, L x is the element length, is the node displacement vector.

[0008] Further, in step S3, the flexible stabilizer is connected in series in the drilling string, and rigid centralizing elements are arranged at both ends of the flexible stabilizer, and the middle part is a flexible damping module containing the buffer block and the leaf spring.

[0009] Further, the upper end of the leaf spring has a floating space in the upper buffer sleeve of the flexible stabilizer, and the lower end is fixed to the lower buffer sleeve through a connecting piece, so that the leaf spring can produce radial deformation and accompany downward axial displacement when compressed.

[0010] Further, when solving the dynamic equation in step S1, the boundary conditions of the drilling string system need to be defined, and the boundary conditions include the upper end boundary condition, the lower end boundary condition and the well wall contact condition of the drilling string.

[0011] Further, the upper end boundary condition of the drilling string is that the lateral displacement and the rotation freedom degrees around the y and z axes of the node are constrained, only the axial displacement and the torsional motion around the x axis are allowed, and the axial tension from the hook and the driving torque from the rotary table are applied.

[0012] Further, the lower end boundary condition of the drilling string is that the dynamic drilling pressure WOB(t) and the friction torque T f (t) that dynamically change with time are applied; wherein the drilling pressure WOB(t) is dynamically updated according to the contact model of the drill bit and the formation, and the expression is: ; wherein, is the drill bit-formation contact stiffness, is the damping coefficient, is the external excitation created, is the drill bit displacement, D p (t) is the formation boundary displacement, R p (t) is the drilling rate.

[0013] Furthermore, the wellbore contact condition is: when the radial displacement of the drill string node... Larger than half the gap between the drill string and the wellbore At that time, the node is subjected to a normal contact force F from the well wall. N and tangential friction force F f The function of the normal contact force F; N Represented as: ; in, The diameter of the wellbore. The diameter of the drill string; The radial velocity of the drill string; This represents the radial displacement of the drill string; For well wall stiffness; and These represent the node velocities before and after the collision.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The ultra-deep well large annulus flexible centralizing and vibration damping device of the present invention can realize flexible adjustment and precise control of the stiffness of the flexible centralizing and vibration damping device. The core feature of the structure is that it uses a leaf spring assembly as an elastic element. By adjusting the parameters such as the number of layers, thickness, width, curvature and material of the leaf springs, the stiffness of the centralizer can be flexibly and precisely controlled so as to accurately match the vibration damping requirements of the drill string, thereby achieving the optimal vibration suppression effect.

[0015] The device is divided into rigid and flexible modules, forming a vibration reduction mechanism that combines rigidity and flexibility: the rigid part provides stable structural support, improves the overall strength of the tool, and ensures overall positioning accuracy, ensuring the alignment of the drill string in the wellbore and reducing the risk of jamming; the flexible module is responsible for absorbing impact and vibration energy, reducing the lateral fluctuation load transmitted to the drill string, reducing stress concentration through leaf spring deformation, extending service life, and adapting to irregular wellbore conditions and dogleg variations; in addition, when the flexible module fails due to extreme working conditions, the rigid module can still play a certain role in alignment, ensuring the normal operation of drilling.

[0016] Modular design can reduce maintenance costs, achieve fault isolation, and flexibly respond to different working conditions: the modular design of the structure allows for the replacement of damaged rigid or flexible components without scrapping the entire device, reducing maintenance costs; and materials or structures can be adjusted according to needs to flexibly respond to different well depths, temperatures, or corrosive environments; it can also achieve fault isolation, so that local failures will not cause overall failures, improving the reliability of the device. Attached Figure Description

[0017] Figure 1The flow chart for discretizing the drill string into a two-node three-dimensional Timoshenko beam element is shown in the figure; Figure 2 The schematic diagram of the drill string contacting the well wall is shown in the figure; Figure 3 The friction model is shown in the figure; Figure 4 The action principle diagram of the flexible centralizing lateral vibration damping device is shown in the figure; Figure 5 The flow chart of the simulation algorithm is shown in the figure; Figure 6 The pressure stabilizing principle diagram of the flexible module damping is shown in the figure; Figure 7 The structural schematic diagram of the flexible centralizing lateral vibration damping device is shown in the figure; Figure 8 The outer spiral flow guide channel schematic diagram of the flexible centralizing lateral vibration damping device is shown in the figure.

[0018] Reference signs: 1, tool upper joint (mandrel); 2, upper buffer sleeve; 3, buffer block; 4, lower buffer sleeve; 5, hexagonal bolt; 6, rigid centralizing element; 7, tool lower joint; 8, leaf spring. DETAILED DESCRIPTION

[0019] The application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the application. These are within the scope of protection of the application.

[0020] Example 1 The deep well drill string vibration whole chain management system comprises a drill string vibration prediction module, a logging instrument, a logging instrument connection device, a central processing computer and a client computer.

[0021] The drill string vibration prediction module inputs drilling engineering information, calculates the drill string vibration distribution pattern of the whole well section, designs the running position and number of the centralizing and damping tool, and inputs the central processing computer. The drill string vibration prediction is performed by the following method, which is advanced in that it can simultaneously couple axial, torsional and lateral vibrations to comprehensively evaluate the vibration intensity of the whole well section.

[0022] The drill string finite element dynamics model is constructed by using the energy method: first, the displacement field general formula of the drill string element is solved by using the node displacement boundary condition, and then it is rewritten into the target form of the node displacement vector multiplied by the modal function matrix; the displacement field is substituted into the general expression of kinetic energy and potential energy to obtain the complete calculation formula of the drill string element energy, and finally the element mass matrix and element stiffness matrix are derived through the Lagrange equation to form the full coupling dynamics equation of the drill string.

[0023] ; wherein, represents total kinetic energy of the system; represents total potential energy of the system; represents external work done on the system.

[0024] The drill string comprises a drill pipe, a drill collar, a stabilizer and a drill bit, and behaves as a beam structure with lateral constraints at both ends in a three-dimensional wellbore; in the present application, a finite element method is adopted to establish a drill string finite element dynamics model, the drill string is discretized into a plurality of units, each unit adopts a double-node three-dimensional Timoshenko beam element model, as shown in the drawing, the drill string is discretized into a double-node three-dimensional Timoshenko beam element process, each unit contains two nodes, each node contains six degrees of freedom: three translational degrees of freedom Figure 1 , two lateral rotational degrees of freedom and one torsional degree of freedom . .

[0025] The drill string motion can be represented by the node displacement vector of the beam element as follows: ; The first and seventh terms of the displacement field are taken as the axial displacement difference mode of the unit, and the boundary conditions of the unit nodes are: ; The second, third, eighth and ninth terms of the displacement field are taken as the lateral displacement difference mode of the unit, and the boundary conditions of the unit nodes are: ; The kinetic energy of the double-node three-dimensional Timoshenko beam element contains two parts: translational kinetic energy and rotational kinetic energy. The total kinetic energy expression of the beam element is obtained by bringing the displacement field expression in each direction into the general expression of the kinetic energy, and finally the unit mass matrix is obtained by means of the Lagrange equation.

[0026] The translational kinetic energy is: ; The rotational kinetic energy is: ; The total kinetic energy of the integrated translational kinetic energy and rotational kinetic energy of the beam element used in the present application is: ; The unit mass matrix can be obtained by Lagrange equation, for the convenience of expression, the unit mass matrix is divided into two parts, wherein represents the inertia mass including three translations and rotation around axis, represents the inertia mass including rotation around axis, wherein, is the polar moment of inertia: , unit .

[0027] ; ; ; The unit mass matrix is spliced into the total mass matrix through the coincident nodes of the adjacent two units.

[0028] The stiffness matrix is an important matrix for describing the deformation resistance of the drill string unit, which reflects the relationship between the force and deformation of the unit in different directions. In the application, the stiffness matrix is derived by establishing the total strain energy of the beam unit, which not only includes the linear stiffness part, but also considers the nonlinear stiffness part under the coupling action of axial force and bending moment, axial force and torque, torque and bending moment, etc. The linear stiffness matrix is independent of the node displacement, mainly reflecting the basic bearing capacity of the drill string unit; and the nonlinear stiffness matrix is related to the node displacement of the unit, which is used to describe the mechanical response of the drill string under complex working conditions such as large deformation, which is crucial for accurately simulating the vibration behavior of the drill string in ultra-deep wells.

[0029] The general expression form of the potential energy of the two-node beam unit is: ; The strain expression is: ; ; ; ; The displacement field expression is: ; ; ; Among them, , and are the displacements of any point on the cross section of the drill string in the , and directions, , , are the deformation angles around the x, y, z coordinate axes respectively. In addition, according to the generalized Hooke's law, the following equation can be obtained: ; The strain expression, displacement field expression and generalized Hooke's law expression are brought into the potential energy formula to obtain the total strain energy of the beam element : ; The element stiffness matrix is obtained through the Lagrange equation as follows: ; wherein is the element linear stiffness matrix, which is independent of the node displacement.

[0030] ; , , is the element nonlinear stiffness matrix, which is related to the element node displacement. respectively represent the generalized displacement in the three directions corresponding to the last time in the iterative solution. represents the nonlinear stiffness matrix affecting the axial deformation of the drill string under the coupling action of the axial force and the bending moment, represents the nonlinear stiffness matrix affecting the bending deformation of the drill string under the coupling action of the axial force and the torque; represents the nonlinear stiffness matrix under the coupling action of the torque and the bending moment.

[0031] ; ; ; The assembly of the mass matrix is the same as that of the element stiffness matrix, and the element stiffness matrix is spliced into the overall stiffness matrix through the coincident nodes of the adjacent two elements.

[0032] The damping of the drill string vibration is represented by Rayleigh damping C as follows: ; wherein: and are damping coefficients, which can be determined by the natural frequency of the drill string system and the corresponding damping ratio. In general, the equivalent damping of the drilling fluid can be included, is the overall mass matrix, is the overall stiffness matrix.

[0033] ​The gravity component of the beam element in x, y, z directions can be expressed as: ; where G is the equivalent gravity of the drill string per unit length, is the angle between the beam element axis and the vertical direction. Thus, the equivalent node force of the gravity vector can be written as: ; The eccentricity problem often occurs in the drill pipe due to manufacturing problems, so a certain centrifugal force will be generated during operation. The centrifugal force of the beam element in x, y, z directions caused by self-rotation is expressed as: ; where e is the eccentricity, is the initial eccentric angle. Similarly, the equivalent node force of the centrifugal force vector is written as: ; In the dynamic analysis of the drill string, the boundary conditions are crucial. They mainly include the upper end boundary condition, the lower end boundary condition and the well wall contact condition.

[0034] The upper end boundary of the drill string is connected with the rotary table or the top drive, and at the connection position, it is subjected to the upward tension of the hook (i.e. the hook load) and the driving force from the rotary table, which are the axial boundary and the torsional boundary of the upper end of the drill string, respectively. This boundary condition corresponds to the freedom constraint of the first node at the uppermost end of the drill string, allowing only axial displacement and torsional motion around the x-axis, reducing the original six degrees of freedom to two degrees of freedom.

[0035] The lower end boundary condition of the drill string is the constraint condition of the rock layer on the drill bit during drilling, including the axial weight on bit (WOB) and the friction torque of the rock layer on the drill bit in the torsional direction . During drilling, the lower end of the drill string is subjected to the unstable weight on bit generated by the interaction between the drill bit and the rock layer. First, an initial weight on bit value is set, which is placed in the time step loop, and the weight on bit will be dynamically adjusted with the drill bit displacement and the stratum response. The subsequent weight on bit update is determined by the drill bit-formation contact model. The size of the weight on bit at the next time depends on the rock boundary displacement and the drilling rate , and the weight on bit expression is: ; where is the drill bit-formation contact stiffness, is the damping coefficient, is the external excitation created, is the drill bit displacement. The drilling rate and the stratum displacement is expressed as: ; ; wherein, , are empirical coefficients of drilling rate, is real-time WOB, is bit torsional angular velocity.

[0036] When the drill bit rotates, frictional torque is generated between the drill bit and the rock formation, and the frictional torque is expressed as: ; wherein, is a rotational speed direction sign function, is an equivalent friction radius, is a friction coefficient.

[0037] When the radial displacement of the drill string is greater than the gap between the drill string and the wellbore, the drill string will be constrained by the well wall.

[0038] As shown in Figure 2 , the drill string is discretized into multiple units, and only the contact between the nodes and the well wall is considered. When the nodes come into contact with the well wall, the drill string will be subjected to the action of the normal force, the tangential friction force and the additional friction torque. When the well wall elastically deforms and recovers, the drill string will be bounced back, and the nodes will become free again. The normal force can be expressed as: ; wherein, is the wellbore diameter, is the drill string diameter; is the radial velocity of the drill string; is the radial displacement of the drill string; is the stiffness of the well wall; and are the velocities of the nodes before and after the collision, respectively.

[0039] The existing drill string model usually only considers the tangential friction, as shown in Figure 3 , the drill string model in the present application comprehensively considers the axial friction and the tangential friction, and the total friction force is solved by calculating the radial pressure, and then it is decomposed into the axial friction force and the tangential friction force. This calculation scheme is more in line with the actual friction effect generated by the contact between the drill string and the well wall.

[0040] ; ; ; Example 2 AsFigure 4 As shown in the drill string vibration model, the vibration reduction centralizer mainly plays a role by changing the local stiffness of the drill string and optimizing the contact force distribution. The essence is to regard the vibration reduction centralizer as a short section with large size but short length added to the drill string model, and to suppress the lateral motion of the drill string through stiffness regulation and boundary constraint.

[0041] By constructing the overall mass matrix, stiffness matrix, damping matrix and force matrix, the dynamic equation of the entire drill string model is formed: ; Wherein, , , and are the generalized acceleration, velocity, displacement and external force matrix of all nodes of the full borehole drill string; , and are the overall mass matrix, overall damping matrix and overall stiffness matrix of the assembled full borehole drill string.

[0042] As shown in Figure 5 , first, the basic parameters of the drill string are set, the drill string is discretized, and the mass, stiffness and damping matrix of the unit are calculated, then the unit matrix is assembled into a global matrix according to the node freedom degree, and the stiffness matrix is corrected according to the number, action position and additional stiffness of the centralizer; Then the boundary conditions are processed, and the load system is constructed, including gravity, centrifugal force, well wall contact force and dynamic drilling pressure, etc.; Then the Newmark-β method (β=1 / 4, γ=1 / 2) is used for iterative calculation, each time step is 0.1 ms, the drilling model and the contact state are updated synchronously, and the dynamic equation is solved, and the node displacement, velocity and acceleration are saved. Before the next cycle, update the external force of each node of the drill string to ensure the accuracy of its physical state. Finally, it is judged whether it needs to continue to cycle. If it needs, return to the parameter update step; if the simulation is completed, end the solution.

[0043] The mud logging instrument is connected to the central processing computer to perform real-time drill string vibration risk assessment, specify the vibration reduction scheme, and compare with the predicted drill string vibration situation to optimize the running scheme of the vibration reduction tool.

[0044] The working principle of the flexible centralizing and vibration reduction device for super deep well large annulus is as follows: the lateral vibration reduction and centralizing device reduces the lateral vibration of the drill string through Figure 7The tool upper joint 1 is connected to the upper drilling tool assembly. The tool lower joint 7 is used for connecting the rigid centralizer and the flexible damping module in series, and provides the required strength of the tool assembly. The flexible damping module is installed in the middle part between the two rigid centralizers, and the buffer block 3 and the leaf spring 8 are inserted into the limiting groove between the upper buffer sleeve 2 and the lower buffer sleeve 4, and are used to absorb the energy generated by the radial collision with the well wall. The leaf spring 8 is provided with a floating space in the upper buffer sleeve 2, and the upper end part is free, and the lower end part is fixed to the lower buffer sleeve 4 through the hexagonal bolt 5. The structure design enables the leaf spring to generate downward impact force while damping, and realizes certain axial pressure stabilizing effect. In addition, the tool is provided with the rigid centralizer on both sides of the flexible damping module, and the design enables the flexible damping part to fail even in severe working conditions, and still ensures certain centralizing of the drill string, as shown in Figure 6 The upper rigid centralizer is integrated with the tool lower joint 7, and the rigid centralizer 6 is connected to the lower end part of the tool lower joint 7 through the thread. Finally, the whole device is connected to the drill bit through the tool lower joint. The device has strong flow guiding capacity, and optimizes the drilling fluid flow field: the inclined gaps between the five flow guiding grooves of the rigid module and the five damping buffer blocks of the flexible module are nearly in the shape of a straight line, as shown in Figure 8 The side surface of the damping buffer block is designed as a smooth inclined surface with an inclination angle of 30°, and there is no vertical dead angle. The fluid scouring capacity is strong, the occurrence rate of the mud cake can be significantly reduced, the energy loss of the fluid due to the right angle impact can be avoided, the stable laminar flow state can be maintained, the drilling fluid can be guided to flow smoothly, the vortex and the energy loss can be reduced, and the drilling fluid flows more smoothly.

[0045] The central processing computer transmits the generated drill string damping scheme and the tool lowering scheme to the client computer in real time, and the tool construction scheme of the drilling site is used for the drill string damping operation.

[0046] The specific embodiments of the application are described above. It should be understood that the application is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essential content of the application. The embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other without conflict.

Claims

1. A method for lateral vibration reduction with flexible straightening in a large annulus of ultra-deep wells, characterized in that, Includes the following steps: S1. The computer system inputs pre-drilling engineering information, calculates the vibration distribution pattern of the drill string throughout the well section based on the established finite element dynamic model of the drill string, and designs the placement position and number of flexible stabilizers, as well as the number of leaf spring layers and compression space in each flexible stabilizer, to generate an initial vibration reduction scheme. S2. During drilling operations, the drilling string vibration data is collected in real time by the logging instrument and transmitted to the computer system. The computer system compares the real-time vibration data with the vibration distribution pattern predicted in step S1, performs real-time risk assessment, and dynamically optimizes the initial vibration reduction scheme accordingly. It adjusts the insertion position, quantity, number of leaf spring layers, and compression space of the flexible stabilizer to generate an optimized real-time vibration reduction scheme. S3. According to the real-time vibration reduction scheme, the flexible stabilizer is inserted at the designated position of the drill string; when the drill string vibrates laterally and collides with the well wall, the buffer block of the flexible stabilizer is compressed, driving the leaf spring to generate radial elastic deformation, converting part of the radial impact kinetic energy into the elastic potential energy of the leaf spring for storage, thereby achieving radial vibration reduction.

2. The method for flexible uprighting and lateral vibration reduction in a large annulus of an ultra-deep well according to claim 1, characterized in that, In step S1, the computer calculates the mass matrix M, stiffness matrix K, and damping matrix C of the entire drill string based on the input well depth, wellbore trajectory, and drill string assembly. These are then substituted into the finite element dynamics equations of the drill string. Combining the boundary conditions and load conditions, the Newmark-β numerical algorithm is used to solve the dynamics equations, obtaining the displacement U and velocity of each node on the drill string at each moment during the drilling process. and acceleration .

3. The method for flexible uprighting and lateral vibration reduction in a large annulus of an ultra-deep well according to claim 2, characterized in that, The finite element dynamic model of the drill string is established using the finite element method, discretizing the drill string into multiple two-node three-dimensional Timoshenko beam elements, each node having six degrees of freedom. The mass matrix and stiffness matrix of each element are derived based on the Lagrange equations, and the overall mass matrix M and overall stiffness matrix K of the system are then assembled. The dynamic equations are: ； in, , , and These are the generalized acceleration, velocity, displacement, and external force matrices for all nodes of the entire wellbore drill string; , and The overall mass matrix, overall damping matrix, and overall stiffness matrix of the assembled full-bore drill string are respectively obtained by numerically solving the Newmark-β numerical algorithm to obtain the vibration distribution pattern of the drill string throughout the well section.

4. The method for flexible uprighting and lateral vibration reduction in a large annulus of an ultra-deep well according to claim 3, characterized in that, After establishing the dynamic model, the linear stiffness matrix of the two-node three-dimensional Timoshenko beam element is... The following energy integral formula is derived: ； E is Young's modulus, G is shear modulus, A is cross-sectional area, and I is... x and I yz These are the torsional and bending moments of inertia, L, respectively. x For the unit length, is the nodal displacement vector.

5. The method for flexible uprighting and lateral vibration reduction in a large annulus of an ultra-deep well according to claim 1, characterized in that, In step S3, the flexible stabilizer is connected in series in the drill string, with rigid straightening elements at both ends and a flexible vibration damping module containing a buffer block and a leaf spring in the middle.

6. The method for flexible uprighting and lateral vibration reduction in a large annulus of an ultra-deep well according to claim 5, characterized in that, The upper end of the leaf spring has a free space within the upper buffer sleeve of the flexible stabilizer, and the lower end is fixed to the lower buffer sleeve by a connector, so that the leaf spring can produce radial deformation and downward axial displacement when compressed.

7. The method for flexible uprighting and lateral vibration reduction in a large annulus of an ultra-deep well according to claim 6, characterized in that, When solving the dynamic equations in step S1, the loads and boundary conditions of the drill string system are defined. The boundary conditions include the upper boundary conditions of the drill string, the lower boundary conditions, and the wellbore contact conditions.

8. The method according to claim 7, characterized in that, The boundary conditions at the upper end of the drill string are as follows: the lateral displacement and rotational degrees of freedom of the node are constrained, only axial displacement and torsional motion about the x-axis are allowed, and an axial tensile force from the hook and a driving torque from the turntable are applied.

9. The method according to claim 7, characterized in that, The boundary conditions at the lower end of the drill string are: applying a drilling pressure WOB(t) that dynamically varies with time and a frictional torque T. f (t); where the drilling pressure WOB(t) is dynamically updated based on the contact model between the drill bit and the formation, and its expression is: ； in, For drill bit-formation contact stiffness, The damping coefficient is... For the creation of external incentives, D represents the drill bit displacement. p (t) represents the geological boundary displacement, R p (t) represents the drilling rate.

10. The method according to claim 7, characterized in that, The wellbore contact condition is: when the radial displacement of the drill string node... Larger than half the gap between the drill string and the wellbore At that time, the drill string node is subjected to a normal contact force F from the wellbore. N and tangential friction force F f The function of the normal contact force F N Represented as: ； in, The diameter of the wellbore. The diameter of the drill string; The radial velocity of the drill string; This represents the radial displacement of the drill string; For well wall stiffness; and These represent the node velocities before and after the collision.

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