A flexible uprighting and lateral vibration reduction method for ultra-deep wells with large annulus

Abstract

This invention provides a flexible centering lateral vibration reduction method for ultra-deep wells with large annulus, belonging to the field of drilling and exploration technology. It involves inputting pre-drilling engineering information, calculating the vibration distribution pattern of the drill string throughout the well based on an established finite element dynamic model of the drill string, designing the placement location 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. Real-time vibration data is compared with the predicted vibration distribution pattern to conduct a real-time risk assessment, and the initial vibration reduction scheme is dynamically optimized accordingly, adjusting the placement location, number of flexible stabilizers, number of leaf spring layers, and compression space to generate an optimized real-time vibration reduction scheme. Flexible stabilizers are placed at designated locations on 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 springs to produce radial elastic deformation, converting part of the radial impact kinetic energy into the elastic potential energy of the leaf springs for storage, thus achieving radial vibration reduction.

Description

Technical Field

[0001] This invention belongs to the field of drilling and exploration technology, and relates to a flexible uprighting and lateral vibration reduction method for large annulus in ultra-deep wells. Background Technology

[0002] Currently, oil and gas reservoirs exhibit a significant, regular distribution of enrichment in deeper formations, with the proportion of deep-seated resources in proven reserves increasing year by year. Developing deep and ultra-deep wells has become an inevitable trend in resource development. Increased well depth means larger wellbore size, but this significantly increases the annular space between the drill string and the wellbore, inducing severe lateral vibration and alternating stress, and greatly increasing the risk of drill string fatigue failure. Secondly, the cumulative effect of the gravity load on ultra-long drill pipes causes uncontrollable helical buckling of the bottom drill string assembly, leading to a sharp drop in drilling pressure transmission efficiency and instability of downhole tools, severely restricting the efficiency and safety of deep well operations. The systemic risks resulting from the coupling of these mechanical behaviors urgently need to be mitigated through structural innovation and breakthroughs in dynamic control technologies. In conventional drilling operations, stabilizers (centralizers) are often used to constrain the lateral displacement of the drill string at a specific location to achieve the centering effect of the drill string. However, the continuous hard contact between the rigid damping interface and the well wall causes high-frequency impacts, leading to a surge in the risk of composite stress concentration in the drill string and casing damage, which is difficult to meet the needs of ultra-deep wells with large annulus conditions.

[0003] Lateral vibration of the drill string is a particularly prominent problem during actual drilling of deep and ultra-deep wells. It not only affects construction efficiency but also poses serious safety risks. Frequent and severe vibrations lead to alternating stress in the drill string, causing fatigue failure and increasing construction costs, resulting in significant economic losses. Existing methods to mitigate lateral vibration use stabilizers to constrain the lateral displacement of the drill string at specific locations, achieving centering of the drill string within the casing. However, the continuous hard contact between the rigid damping interface and the wellbore causes high-frequency impacts, leading to stress concentration in the drill string and a surge in casing damage risk, making it unsuitable for the demands of ultra-deep wells with large annulus conditions. In view of these factors, the inventors have proposed an integrated drill string vibration reduction method for deep and ultra-deep wells. This method utilizes the drill string vibration energy to convert it into the elastic potential energy of a leaf spring and axial pressure in the drill string, achieving a vibration reduction and limiting effect. A flexible stabilizer for bottom-hole drill string vibration reduction is designed to redirect this potentially destructive energy towards deep well acceleration, turning a potential hazard into a benefit, with the aim of achieving a new breakthrough in deep and ultra-deep well acceleration. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a flexible uprighting and lateral vibration reduction method for ultra-deep wells with large annulus, comprising the following steps:

[0005] S1. The computer system inputs drilling engineering information and 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. According to the vibration distribution pattern, the placement position and number of flexible stabilizers, as well as the number of leaf spring layers and compression space in each flexible stabilizer, are designed to generate an initial vibration reduction scheme.

[0006] 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.

[0007] 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 produce 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. At the same time, during the compression and rebound of the leaf spring, part of the radial impact force is converted into a downward axial impact force, which acts on the drill string, thereby achieving axial pressure stabilization.

[0008] Further, 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 size, and drill string assembly. These are then substituted into the dynamic equations, and combined with boundary conditions and loads, the dynamic equations are solved using the Newmark-β numerical algorithm to obtain the displacement U and velocity of each node on the drill string at each moment during the future drilling process. and acceleration .

[0009] Furthermore, the finite element dynamic model of the drill string is established using the finite element method, specifically: the drill string is discretized 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 equation, and the overall mass matrix M and overall stiffness matrix K of the system are assembled; the dynamic equation of the system is expressed as:

[0010] ;

[0011] 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, and the Newmark-β method is used to solve them numerically to obtain the vibration distribution pattern of the drill string throughout the well section.

[0012] Furthermore, after establishing the aforementioned dynamic model, the linear stiffness matrix of the two-node three-dimensional Timoshenko beam element is... The following energy integral formula is derived:

[0013] ;

[0014] 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.

[0015] Furthermore, 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 the buffer block and leaf spring in the middle.

[0016] Furthermore, 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.

[0017] Furthermore, when solving the dynamic equation in step S1, it is necessary to define the boundary conditions of the drill string system, which include the upper boundary conditions of the drill string, the lower boundary conditions, and the wellbore contact conditions.

[0018] Furthermore, 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.

[0019] Furthermore, the boundary conditions at the lower end of the drill string are: applying a drilling pressure WOB(t) and a frictional torque T that dynamically vary with time. 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:

[0020] ;

[0021] 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.

[0022] 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:

[0023] ;

[0024] 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.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] 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.

[0027] 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.

[0028] 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

[0029] Figure 1 Flowchart of discretizing the drill string into a two-node three-dimensional Timoshenko beam element;

[0030] Figure 2 This is a schematic diagram of the contact between the drill string and the well wall;

[0031] Figure 3 For friction model;

[0032] Figure 4 This is a schematic diagram illustrating the working principle of a flexible straightening lateral vibration damping device.

[0033] Figure 5 Here is the flowchart of the simulation algorithm;

[0034] Figure 6 Schematic diagram of vibration reduction and voltage stabilization principle for flexible modules;

[0035] Figure 7 A schematic diagram of a flexible straightening transverse vibration damping device;

[0036] Figure 8 This is a schematic diagram of the external spiral guide channel of the flexible straightening transverse vibration damping device.

[0037] Reference numerals: 1. Upper tool connector (mandrel); 2. Upper buffer sleeve; 3. Buffer block; 4. Lower buffer sleeve; 5. Hex bolt; 6. Rigid straightening element; 7. Lower tool connector; 8. Leaf spring. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0039] Example 1

[0040] The deep well drill string vibration control system includes: a drill string vibration prediction module, a logging instrument, a logging instrument connection device, a central processing computer, and a client computer.

[0041] The drill string vibration prediction module inputs drilling engineering information, calculates the vibration distribution pattern of the drill string throughout the well section, designs the placement and quantity of the straightening and vibration reduction tools, and inputs the data into the central processing computer.

[0042] The drill string vibration prediction method is advanced because it can simultaneously couple axial, torsional and lateral vibrations to comprehensively evaluate the vibration intensity of the entire well section.

[0043] The finite element dynamic model of the drill string is constructed using the energy method: first, the general formula of the displacement field of the drill string element is obtained using the nodal displacement boundary conditions, and then it is rewritten as the objective form of multiplying the nodal displacement vector with the modal function matrix; substituting this displacement field into the general expression of kinetic energy and potential energy, the complete formula of the drill string element energy is obtained, and finally the fully coupled dynamic equation of the drill string is derived by using the Lagrange equation to form the element mass matrix and the element stiffness matrix.

[0044] ;

[0045] in, This represents the total kinetic energy of the system; This represents the total potential energy of the system; This represents the work done by external forces on the system.

[0046] The drill string includes drill pipe, drill collars, stabilizers, and drill bit. In a three-dimensional wellbore, it is represented as a beam structure with lateral constraints at both ends. In this invention, the finite element method is used to establish a finite element dynamic model of the drill string. The drill string is discretized into several elements, and each element adopts a two-node three-dimensional Timoshenko beam model, such as... Figure 1 As shown, the drill string is discretized into a two-node three-dimensional Timoshenko beam element flow. Each element contains two nodes, and each node contains six degrees of freedom: three translational degrees of freedom. Two lateral rotational degrees of freedom and a torsional degree of freedom .

[0047] The drill string motion can be transmitted via the nodal displacement vectors of the beam elements. The following representation is made:

[0048] ;

[0049] Taking the first and seventh terms of the displacement field as the axial displacement difference mode of this element, the boundary conditions of its element nodes are as follows:

[0050] ;

[0051] Taking the 2nd, 3rd, 8th, and 9th terms of the displacement field as the lateral displacement difference mode of this element, the boundary conditions of its element nodes are as follows:

[0052] ;

[0053] The kinetic energy of a two-node 3D Timoshenko beam element consists of two parts: translational kinetic energy and rotational kinetic energy. The overall kinetic energy expression of the beam element is obtained by substituting the displacement field expressions in each direction into the general expression for kinetic energy. Finally, the element mass matrix is ​​obtained using the Lagrange equation.

[0054] Among them, translational kinetic energy for:

[0055] ;

[0056] rotational kinetic energy for:

[0057] ;

[0058] By differentiating the displacement field expressions in each direction with respect to time and substituting them into the kinetic energy expression, we obtain the total kinetic energy of the beam element used in this invention, which integrates translational and rotational kinetic energies. for:

[0059] ;

[0060] The element mass matrix can be obtained using the Lagrange equation. For ease of representation, the element mass matrix is ​​divided into two parts, where... This indicates that it includes three translational and orbital movements. The inertial mass of the axis during rotation. Indicates including around The inertial mass of the axis of rotation, where, For the torsional polar moment of inertia: ,unit .

[0061] ;

[0062] ;

[0063] ;

[0064] The derived element mass matrix is ​​used as a medium to splice the element mass matrices into the overall mass matrix.

[0065] The stiffness matrix is ​​a crucial matrix describing the deformation resistance of a drill string element, reflecting the relationship between force and deformation in different directions. In this invention, the stiffness matrix is ​​derived by establishing the total strain energy of the beam element, encompassing both linear stiffness components and nonlinear stiffness components under coupled effects such as axial force and bending moment, axial force and torque, and torque and bending moment. The linear stiffness matrix is ​​independent of nodal displacements and primarily reflects the basic load-bearing capacity of the drill string element; while the nonlinear stiffness matrix is ​​related to nodal displacements and is used to describe the mechanical response of the drill string under complex conditions such as large deformations, which is essential for accurately simulating the vibration behavior of drill strings in ultra-deep wells.

[0066] The general form of the potential energy of a two-node beam element is:

[0067] ;

[0068] The strain expression is:

[0069] ;

[0070] ;

[0071] ;

[0072] ;

[0073] The expression for the displacement field is:

[0074] ;

[0075] ;

[0076] ;

[0077] in, , and It is any point on the cross-section of the drill string. , and Displacement in the direction, , , These are the deformation angles around the x, y, and z coordinate axes, respectively. Furthermore, according to the generalized Hooke's law, we can obtain:

[0078] ;

[0079] Substituting the strain expression, displacement field expression, and generalized Hooke's law expression into the potential energy formula yields the total strain energy of the beam element. for:

[0080] ;

[0081] The element stiffness matrix can be obtained using the Lagrange equation. for:

[0082] ;

[0083] in It is the linear stiffness matrix of the element, which is independent of nodal displacements.

[0084] ;

[0085] , , This is the nonlinear stiffness matrix of the element, which is related to the nodal displacements of the element. These represent the corresponding time values ​​in the previous time step during iterative solution. Generalized displacement in three directions. This represents the nonlinear stiffness matrix that influences the axial deformation of the drill string under the coupled action of axial force and bending moment. The nonlinear stiffness matrix representing the effect of the coupling of axial force and torque on the bending deformation of the drill string; Nonlinear stiffness matrix under the coupling of torque and bending moment.

[0086] ;

[0087] ;

[0088] ;

[0089] Similar to the assembly of the mass matrix, the derived element stiffness matrix is ​​spliced ​​together to form the global stiffness matrix by using the coincident nodes of two adjacent elements as the medium.

[0090] The damping of drill string vibration is expressed using Rayleigh damping C as follows:

[0091] ;

[0092] in: and The damping coefficient can be determined by the natural frequency of the drill string system and the corresponding damping ratio. Generally, it can include the equivalent damping of the drilling fluid. For the overall quality matrix, This is the overall stiffness matrix.

[0093] Defining nodal forces, the gravitational components of a beam element in the x, y, and z directions can be expressed as:

[0094] ;

[0095] Where G is the equivalent gravity per unit length of the drill string. Let be the angle between the beam element axis and the vertical direction. Therefore, the equivalent nodal force of the gravity vector can be written as:

[0096] ;

[0097] Due to manufacturing defects, drill pipes often exhibit eccentricity, thus generating centrifugal force during operation. The centrifugal force caused by the rotation of a beam element in the x, y, and z directions is expressed as:

[0098] ;

[0099] Where e is the eccentricity. This is the initial eccentricity angle. Similarly, the equivalent nodal force of the centrifugal force vector... Written as:

[0100] ;

[0101] Boundary conditions are crucial in drill string dynamics analysis. They mainly include upper boundary conditions, lower boundary conditions, and wellbore contact conditions.

[0102] The upper boundary of the drill string is connected to the rotary table or top drive. At the connection point, it is subjected to an upward pulling force from the hook (i.e., hook load) and a driving force from the rotary table. These two forces are the axial boundary and torsional boundary of the upper end of the drill string, respectively. This boundary condition also corresponds to the first node at the top of the drill string, which constrains the degree of freedom, allowing only axial displacement and torsional motion around the x-axis, thus reducing the original six degrees of freedom to two degrees of freedom.

[0103] The lower boundary conditions of the drill string are the constraints imposed on the drill bit by the rock formation during drilling, including axial weight on drill bit (WOB) and torsional friction torque exerted on the drill bit by the rock formation. During drilling, the lower end of the drill string experiences unstable drill pressure generated by the interaction between the drill bit and the rock formation. An initial drill pressure value is first set and placed within the time step cycle. The drill pressure is dynamically adjusted based on drill bit displacement and formation response. Subsequent drill pressure updates are determined by the drill bit-formation contact model. The magnitude of the drill pressure at the next moment depends on the rock formation boundary displacement. With drilling rate Drilling pressure The expression is:

[0104] ;

[0105] in, For drill bit-formation contact stiffness, The damping coefficient is... For the creation of external incentives, This represents drill bit displacement. Drilling rate. With stratum displacement Represented as:

[0106] ;

[0107] ;

[0108] in, , All of these are empirical coefficients for drilling rate. For real-time drilling pressure, ω represents the angular velocity of the drill bit's torsion.

[0109] When the drill bit rotates and drills, friction with the rock formation generates a reverse torque, which is called frictional torque. Represented as:

[0110] ;

[0111] in, The sign function for rotational speed direction. The equivalent friction radius, is the coefficient of friction.

[0112] 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.

[0113] like Figure 2 As shown, the drill string is discretized into multiple elements, considering only the contact between the nodes and the wellbore. When a node contacts the wellbore, the drill string is subjected to normal force, tangential friction force, and additional frictional torque. When the wellbore recovers from elastic deformation, the drill string rebounds, and the node returns to a free state. (Normal force...) It can be represented as:

[0114] ;

[0115] 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.

[0116] Existing drill string models typically only consider tangential friction, such as Figure 3As shown, the drill string model in this invention comprehensively considers axial and tangential friction. The total friction force is calculated by determining the radial pressure, and then decomposed into axial and tangential friction forces. This calculation scheme better reflects the actual frictional effects generated by the contact between the drill string and the wellbore.

[0117] ;

[0118] ;

[0119] ;

[0120] Example 2

[0121] like Figure 4 As shown, in the drill string vibration model, the vibration damping stabilizer mainly functions by changing the local stiffness of the drill string and optimizing the contact force distribution. Essentially, the vibration damping stabilizer is regarded as a short section with a larger size but shorter length added to the drill string model, and the lateral movement of the drill string is suppressed by stiffness control and boundary constraints.

[0122] By constructing the overall mass matrix, stiffness matrix, damping matrix, and force matrix, the dynamic equations of the entire drill string model are formed:

[0123] ;

[0124] in, , , and These are the generalized acceleration, velocity, displacement, and external force matrices for all nodes of the entire wellbore drill string; , and These are the overall mass matrix, overall damping matrix, and overall stiffness matrix of the assembled full-bore drill string, respectively.

[0125] like Figure 5 As shown, the basic parameters of the drill string are first set, the drill string is discretized, and the mass, stiffness, and damping matrices of the elements are calculated. Then, the element matrices are assembled into a global matrix according to the nodal degrees of freedom, and the stiffness matrix is ​​corrected according to the number, position, and additional stiffness of the centralizers. Next, the boundary conditions are processed, and a load system is constructed, including gravity, centrifugal force, wellbore contact force, and dynamic drilling pressure, etc. Then, the Newmark-β method (β=1 / 4, γ=1 / 2) is used for iterative calculation, with each time step being 0.1ms. The drilling model and contact state are updated synchronously, and the dynamic equations are solved, saving the displacement, velocity, and acceleration of the nodes. Before each iteration, the external forces at each node of the drill string are updated to ensure the accuracy of its physical state. Finally, it is determined whether to continue the iteration. If so, the parameter update step is returned; if the simulation is complete, the solution ends.

[0126] The logging instrument is connected to the central processing computer to conduct real-time drill string vibration risk assessment, specify vibration reduction schemes, compare them with the predicted drill string vibration, and optimize the deployment plan of vibration reduction tools.

[0127] The working principle of the ultra-deep well large annulus flexible straightening and vibration reduction device is as follows: The lateral vibration reduction and straightening device passes through... Figure 7 The upper tool connector 1 connects to the upper drill string assembly. The lower tool connector 7 is used to connect the rigid centralizing element and the flexible damping module in series, and provides the required strength for the overall tool. The flexible damping module is installed in the middle of the two rigid centralizing elements. 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 to absorb the energy generated by radial collision with the well wall. The leaf spring 8 has a reserved space for movement in the upper buffer sleeve 2, allowing its upper end to be free, while its lower end is fixed to the lower buffer sleeve 4 by hexagonal bolts 5. This structural design allows the leaf spring to generate a downward impact force while damping vibration, achieving a certain axial pressure stabilization effect. Furthermore, rigid centralizing elements are added to both sides of the flexible damping module. This design ensures that even under harsh working conditions where the flexible damping part fails, a certain degree of drill string alignment can still be maintained. Figure 6 As shown. The upper rigid centralizing element and the lower tool connector 7 are integrated, while the rigid centralizing element 6 is threaded to the lower end of the lower tool connector 7. Finally, the entire device is connected to the drill bit via the lower tool connector. It possesses strong flow guiding capacity and optimizes the drilling fluid flow field: the inclined gaps between the five flow guiding channels of the rigid module and the five vibration damping buffer blocks of the flexible module are connected in a near-linear shape, such as... Figure 8 As shown, the sides of the vibration damping buffer block are all designed as smooth inclined surfaces with an inclination angle of 30°, without vertical dead angles. The fluid has a strong flushing ability, which can significantly reduce the mud bag occurrence rate and avoid energy loss caused by right-angle impact of the fluid. It maintains a stable laminar flow state, can guide the drilling fluid to flow smoothly, reduce eddies and energy loss, and make the drilling fluid flow more smoothly.

[0128] The central processing computer generates a drill string vibration reduction plan and a tool lowering plan, which are then transmitted to the client computer in real time. The drilling site tool construction plan is then used to carry out drill string vibration reduction operations.

[0129] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A flexible centralizer transverse vibration damping method for ultra-deep well large annulus, characterized in that, The method comprises the following steps: S1, a computer system inputs pre-drilling engineering information, calculates the vibration distribution pattern of the whole wellbore 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 a 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 in 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; the flexible stabilizer is connected in series in the drill string, and rigid centralizing elements are arranged at both ends of the flexible stabilizer, and the middle part is a flexible vibration reduction module containing a buffer block and a leaf spring; 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 on the lower buffer sleeve through a connecting piece, so that the leaf spring can produce radial deformation and axial displacement downward when it is pressed.

2. The flexible centralizer transverse vibration damping method for ultra-deep well large annulus according to claim 1, characterized in that, In step S1, the computer calculates the total mass matrix M, the total damping matrix C and the total stiffness matrix K of the whole wellbore drill string according to the input well depth, wellbore trajectory and drill string assembly, substitutes them into the drill string finite element dynamics equation, combines boundary conditions and load conditions, solves the dynamics equation through the Newmark-β numerical algorithm, and obtains the displacement U, velocity and acceleration 3. The method of claim 2, wherein the method is used in an ultra-deep well with a large annulus. The drill string finite element dynamics model is established by the finite element method, and the drill string is discretized into multiple double-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 equation, and the total mass matrix M and the total stiffness matrix K of the whole wellbore drill string are integrated; the dynamics equation is: wherein, U and F are acceleration, velocity, displacement and external force matrix of all nodes of the full hole drilling string, respectively; M, C and K are total mass matrix, total damping matrix and total stiffness matrix of the full hole drilling string, respectively, and the Newmark-beta numerical algorithm is used for numerical solution to obtain the vibration distribution pattern of the full hole drilling string.

4. The method of claim 3, wherein the method is a method of flexible centralizer transverse vibration reduction in an ultra-deep well large annulus, characterized in that, After the dynamic model is established, the linear stiffness matrix of the double-node three-dimensional Timoshenko beam element The derivation is performed by the following energy integration 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 moments, respectively, L x is the element length, (q x , q y , q z , q θx ) are the nodal displacement vectors.

5. The method of claim 1, wherein the method is used in an ultra-deep well with a large annulus. In step S1, the load and boundary conditions of the drill string system are defined, and the boundary conditions include the upper end boundary condition, the lower end boundary condition and the well wall contact condition of the drill string.

6. The method of claim 5, wherein, The upper end boundary condition of the drill string is: the lateral displacement and the rotation freedom around y and z axes of the node are constrained, only axial displacement and torsional motion around x axis are allowed, and axial tension from the hook and driving torque from the rotary table are applied.

7. The method of claim 5, wherein, The lower end boundary condition of the drill string is that a dynamic drilling pressure WOB(t) and a friction torque T are applied over time f (t); wherein the drilling pressure WOB(t) is dynamically updated according to a contact model of the drill bit and the formation, and the expression is: Among them, K r Let η be the drill bit-formation contact stiffness, ξ(t) be the damping coefficient, ξ(t) be the external excitation, x(t) be the drill bit displacement, and D be the external excitation. p (t) represents the geological boundary displacement, R p (t) represents the drilling rate.

8. The method of claim 5, wherein, The wellbore contact condition is: when the radial displacement u of the drill string node... r Greater than the half-clearance between the drill string and the wellbore (d) o -d i When the value is 1 / 2, 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: where d o is the borehole diameter, d i is the drill string diameter; v r is the radial velocity of the drill string; u r is the radial displacement of the drill string; k h is the borehole stiffness; v2 and v1 are the nodal velocities before and after the impact, respectively.

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