Method and system for evaluating influence of drilling tool vibration on borehole wall stability

Abstract

The invention discloses a method and system for evaluating the influence of vibration of a drilling tool on the stability of a well wall, and the method comprises the steps: obtaining a vibration signal of the surface of the drilling tool in a drilling process, and calculating the contact force between a drilling rod and the well wall based on the vibration signal in combination with a current drilling parameter through a downhole drilling tool kinetic model; according to the contact force, collision stress representing the collision strength between the drill rod and the well wall is calculated; and quantitatively evaluating the stability of the current well wall according to the dynamic collision stress in the drilling process. According to the well wall stability evaluation result, the safety risk is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of drilling risk analysis technology, and in particular to a method and system for assessing the impact of drill string vibration on wellbore stability. Background Technology

[0002] During drilling, various factors frequently cause wellbore collapse, leading to leakage and stuck pipe, thus affecting on-site construction progress. Current research primarily analyzes the impact of drilling fluid on wellbore stability, neglecting the influence of drill string vibration. During drilling, continuous vibrations occur due to gravity, well inclination, and other factors. The drill string experiences lateral, torsional, and axial vibrations, resulting in buckling deformation. The drill string constantly collides with and contacts the wellbore rock mass, while the drilling fluid further impacts the rock mass, leading to wellbore instability.

[0003] Although existing technologies provide experimental analysis and mathematical model simulation methods for analyzing wellbore stability, the following problems still exist:

[0004] (1) The experimental study mainly focuses on the single impact of the drill string on the well wall. However, in reality, the drill string repeatedly impacts the surrounding well wall rocks with different lateral vibration velocities, ignoring the influence of subsequent impacts.

[0005] (2) The mathematical model used to predict the dynamic behavior of drill string vibration cannot be guaranteed in all cases. The drill string vibration model is too simple and cannot accurately predict the dynamic behavior of the drill string during the drilling process. Moreover, the assumptions made when verifying the influence of drill string vibration on wellbore stability only apply to a single impact caused by drill string vibration collision when the stress is greater than the rock strength.

[0006] (3) The similarity of some features between wells is too great, which can easily lead to misunderstandings when analyzing the well walls;

[0007] (4) The applicability of the solution is limited, and the installation environment of other tools such as vibration damping and vibration absorption tools needs to be considered.

[0008] In summary, the existing technology needs to provide a wellbore stability analysis scheme that can take into account the vibration effect after the drill string and drill tool continuously collide and contact with the wellbore rock mass, in order to solve one or more of the above-mentioned technical problems. Summary of the Invention

[0009] The purpose of this invention is to provide a wellbore stability analysis scheme that can take into account the vibration effect after continuous collision and contact between the drill string and the wellbore rock mass, so as to solve one or more technical problems in the prior art.

[0010] To address the aforementioned technical problems, embodiments of the present invention provide a method for evaluating the impact of drill string vibration on wellbore stability, comprising: obtaining vibration signals on the drill string surface during drilling; calculating the contact force between the drill string and the wellbore based on the vibration signals and current drilling parameters using a downhole drill string dynamics model; calculating the collision stress characterizing the collision intensity between the drill string and the wellbore based on the contact force; and quantitatively evaluating the stability of the current wellbore based on the dynamic collision stress during drilling.

[0011] Preferably, the step of calculating the contact force between the drill pipe and the wellbore based on the vibration signal and the current drilling parameters using a downhole drilling tool dynamics model includes: solving the downhole drilling tool dynamics model based on the vibration signal and the current drilling parameters to obtain the characteristics of the drill string's motion. These characteristics include contact force characteristics between the drill pipe and the wellbore, torque exerted by the wellbore on the drill pipe, axial force exerted by the rock mass on the drill bit, and torque exerted by the rock mass on the drill bit. The downhole drilling tool dynamics model is a constraint relationship model characterizing the contact forces between the drill pipe and the wellbore and the collision forces between the drill bit and the rock mass. Based on the contact force characteristics between the drill pipe and the wellbore, the radial contact force is obtained by calculating the tangential friction force between the drill pipe and the wellbore, and this radial contact force is used as the current contact force calculation result.

[0012] Preferably, the downhole drilling tool dynamics model is represented by the following expression:

[0013]

[0014] Where m1 represents the mass of the drill pipe as the first mass body, m2 represents the mass of the drill bit and drill collar as the second mass body, J1 and J2 represent the moments of inertia, φ1 and φ2 represent the angular displacements of the drill pipe and drill assembly, and x1 and x2 represent the displacements of the drill pipe and drill assembly in the X-axis direction. These represent the velocities of the drill pipe and drill string assembly in the X-axis direction, respectively. y1 and y2 represent the accelerations of the drill pipe and drill string assembly in the X-axis direction, respectively, and the displacements of the drill pipe and drill string assembly in the Y-axis direction, respectively. These represent the velocities of the drill pipe and drill string assembly in the Y-axis direction, respectively. Zi and Zj represent the accelerations of the drill pipe and drill string assembly in the Y-axis direction, respectively, and Zi and Zj represent the displacements of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the velocities of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the speeds of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the angular velocities of the drill pipe and the drill string assembly, respectively. V represents the angular acceleration of the drill pipe and the drill string assembly, respectively. o The axial velocity at the drill pipe is represented by Ω, time is represented by t, and the rotational speed at the drill pipe is represented by C. a C t They represent the damping coefficients, k and k, respectively. a k represents the axial stiffness of the drill string. t F0 represents the torsional stiffness, and F0 represents the axial tensile force applied to the drill pipe from the top. 1x F 1y W represents the components of the contact force characteristic parameter F1 in the X-axis and Y-axis directions, respectively. b T represents the axial force exerted by the rock mass on the drill bit. fb T1 represents the torque exerted by the rock mass on the drill bit, and T2 represents the torque exerted by the well wall on the drill pipe. The contact force characteristic parameter is expressed by the following expression:

[0015]

[0016] Where ψ represents the angle between the centroid of the drill pipe section and the X-axis, and F r F represents the radial contact force between the drill pipe and the wellbore. t This represents the tangential frictional force between the drill pipe and the well wall.

[0017] Preferably, the method further includes: optimizing the downhole drilling tool dynamics model based on measured vibration signals and drilling parameters of the drilled well or drilled section, so as to calculate the contact force using the optimized model, including: calculating the simulated contact force using the downhole drilling tool dynamics model to be optimized based on the drilling parameters of the drilled well or drilled section; comparing the measured vibration signals of the drilled well or drilled section with the simulated contact force, and optimizing the model coefficients in the downhole drilling tool dynamics model based on the comparison results.

[0018] Preferably, the step of calculating the collision stress, which characterizes the collision intensity between the drill pipe and the well wall, based on the contact force includes: calculating the coupled elastic modulus after the drill pipe contacts the well wall, based on the elastic modulus and Poisson's ratio of the drill pipe obtained during real-time drilling, and the elastic modulus and Poisson's ratio of the well wall; and calculating the collision stress based on the coupled elastic modulus, the contact radius between the drill pipe and the well wall, and the contact force, wherein the collision stress is expressed using the following expression:

[0019]

[0020] Where p0 represents the collision stress, F r E represents radial contact force. * R represents the coupled elastic modulus, and R represents the contact radius between the drill pipe and the well wall.

[0021] Preferably, the coupled elastic modulus is calculated using the following expression:

[0022]

[0023] Where υ1 and υ2 represent the Poisson's ratios of the drill pipe and the well wall, respectively, and E1 and E2 represent the elastic moduli of the drill pipe and the well wall, respectively; the contact radius between the drill pipe and the well wall is calculated using the following expression:

[0024]

[0025] Where, r o Indicates the drill pipe radius, r d Indicates the radius of the well wall.

[0026] Preferably, the step of quantitatively evaluating the rock strength of the current wellbore based on the dynamic collision stress during the drilling process includes: counting the number of times the collision stress exceeds a preset stress threshold based on the dynamic collision stress, and recording it as the number of collisions; and calculating the stability of the current wellbore based on the dynamic collision stress and the number of collisions.

[0027] Preferably, when the impact stress exceeds a preset wellbore ultimate stress threshold, it indicates wellbore rock failure, and the wellbore stability calculation result is obtained using a first safety quantification level expression, which is: σ represents the rock mass strength, p o Let represent the collision stress, and n represent the safety factor. The ultimate stress threshold of the well wall is greater than the preset stress threshold. If the collision stress does not exceed the preset ultimate stress threshold of the well wall and the number of collisions exceeds the first threshold, it indicates that the strength of the well wall rock mass has decreased and failure has occurred. Therefore, the well wall stability calculation result is obtained using the second safety quantification level expression, which is: If the collision stress does not exceed the preset wellbore ultimate stress threshold and the number of collisions exceeds the second threshold, it indicates that the wellbore rock mass strength has decreased and is affecting the wall thickness. Therefore, the wellbore stability calculation result is obtained using the third safety quantification level expression, which is: The second number threshold is less than the first number threshold, wherein the second number threshold is one percent of the first number threshold.

[0028] On the other hand, embodiments of the present invention provide a system for evaluating the impact of drill string vibration on wellbore stability, characterized by comprising: a basic data acquisition module configured to acquire vibration signals of the drill string surface during drilling; a contact force analysis module configured to calculate the contact force between the drill string and the wellbore based on the vibration signals, combined with current drilling parameters, and using a downhole drill string dynamics model; a collision stress generation module configured to calculate the collision stress characterizing the collision intensity between the drill string and the wellbore based on the contact force; and a rock mass stability calculation module configured to quantitatively evaluate the stability of the current wellbore based on the dynamic collision stress during drilling.

[0029] In addition, embodiments of the present invention also provide a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the method described above.

[0030] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0031] This invention proposes a method and system for evaluating the impact of drill string vibration on wellbore stability. This method and system improve upon existing wellbore stability assessment methods by considering the influence of drill pipe vibration on wellbore stability. By establishing a bottom drill string dynamics model, the relationship between the drill string and the wellbore is measured, providing a strong basis for drilling optimization. The wellbore stability assessment results provided by this invention can effectively reduce safety risks, ensure the safety of drilling personnel, avoid additional reinforcement measures and the use of more drilling materials, improve the efficiency of oil and gas exploration and development, shorten the development cycle, reduce development costs, and simultaneously increase oil and gas recovery and production while reducing drilling costs and improving economic efficiency. It addresses potential wellbore collapse and blockage problems caused by wellbore instability during drilling, avoids drill bit burial and stuck drill bit accidents, significantly improves drilling progress and success rate, and thus significantly increases drilling success rate and reduces accidents.

[0032] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0033] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0034] Figure 1This is a schematic diagram illustrating the steps of a method for evaluating the impact of drill string vibration on wellbore stability, as described in an embodiment of this application.

[0035] Figure 2 This is a schematic flowchart illustrating the method for evaluating the impact of drill string vibration on wellbore stability, as described in an embodiment of this application.

[0036] Figure 3 This is a simplified schematic diagram of a downhole drilling assembly used in a method for evaluating the impact of drill string vibration on wellbore stability, as described in an embodiment of this application.

[0037] Figure 4 This is a schematic diagram illustrating the decomposition principle of the interaction force between the drill pipe and the well wall in the method for evaluating the influence of drill string vibration on well wall stability, as described in an embodiment of this application.

[0038] Figure 5 This is a schematic diagram illustrating the principle of drill pipe contact with the well wall in a method for evaluating the impact of drill string vibration on well wall stability, as described in an embodiment of this application.

[0039] Figure 6 This is a schematic diagram of a system for evaluating the impact of drill string vibration on wellbore stability, according to an embodiment of this application. Detailed Implementation

[0040] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0041] Furthermore, the steps illustrated in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in a different order than that shown here.

[0042] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms “a” and “an” as used herein are also intended to include the plural. It should also be understood that the terms “comprising” and / or “including” as used herein specify the presence of the stated features, integers, steps, operations, units, and / or components, without excluding the presence or addition of one or more other features, integers, steps, operations, units, components, and / or combinations thereof.

[0043] To address one or more technical problems mentioned in the background, this application proposes a method and system for evaluating the impact of drill string vibration on wellbore stability. By establishing a bottom drill string dynamic model and measuring the vibration acceleration of the bottom drill string using a high-frequency measurement sub, the method studies the collision between the drill string and the wellbore, calculates the magnitude of the collision force, and analyzes the stress conditions on the wellbore to quantitatively measure its stability. This invention provides a new perspective for analyzing wellbore instability, offers a scientific theoretical basis for studying the impact of drill string vibration on wellbore stability, further improves existing wellbore stability assessment schemes, optimizes drilling parameters, and reduces the probability of serious drilling risks such as wellbore collapse and lost circulation.

[0044] Figure 1 This is a schematic diagram illustrating the steps of a method for evaluating the impact of drill string vibration on wellbore stability, as described in an embodiment of this application. Figure 2 This is a schematic flowchart illustrating a method for evaluating the impact of drill string vibration on wellbore stability, as described in an embodiment of this application. The following is a detailed explanation of the method. Figure 1 and Figure 2 The specific steps of the method for evaluating the impact of drill string vibration on wellbore stability (hereinafter referred to as the "wellbore stability evaluation method") described in the embodiments of the present invention will be explained.

[0045] Step S110 obtains the dynamic vibration signal of the drill string surface during the real-time drilling process.

[0046] In step S110, a downhole vibration measurement sub installed near the drill bit is used to collect high-frequency vibration signals in real time, characterizing the collision between the drill string and the well wall during the drilling process, thus forming a dynamic vibration signal.

[0047] Step S120 calculates the contact force between the drill pipe and the well wall based on the (dynamic) vibration signal obtained in step S110, combined with the current drilling parameters, using the downhole drilling tool dynamics model.

[0048] In this embodiment of the invention, the downhole drilling tool dynamics model is used to simulate the vibration motion law of the drilling tool under different drilling conditions. This model can directly simulate the characteristics of the drilling tool motion law under the corresponding drilling conditions by inputting real-time drilling parameters.

[0049] It should be noted that a downhole drilling tool dynamics model needs to be constructed before implementing the wellbore stability assessment method described in this invention.

[0050] In this embodiment of the invention, based on the drill string assembly structure, the constraint relationship between the drill bit and the rock, and the constraint management between the wellbore and the drill string, the motion mechanism of the downhole drill string is analyzed, and the interaction between the drill bit and the rock mass, and between the drill string and the wellbore, is studied, thereby constructing a downhole drill string dynamic model. Drilling is the main method of oil extraction. Axial force and torque are provided by the top drilling rig to drive the drill string to break through the rock mass, enabling continuous drilling. The overall length of the drill string can reach several kilometers. Under the condition of top power drive, the drill string continuously rotates and drills. Although many wells are currently vertical, due to factors such as well inclination and gravity, the drill string generates various vibrations, including axial, lateral, and torsional vibrations. The drill string and the wellbore continuously contact and collide with each other, and the wellbore exerts tangential and radial forces on the drill string, affecting the rotation of the drill string. The interaction between the drill bit and the rock mass breaks the rock mass encountered during drilling, and the rock mass exerts axial force and shear stress on the drill string.

[0051] In practical applications, drilling rigs typically consist of drill pipe, drill collars, and drill bits. For example... Figure 3 As shown, this invention simplifies the bottom-hole drill string assembly (BHA) by treating the assembly as two concentrated mass blocks (the drill pipe as the first mass body 1, and the drill bit and drill collar as the second mass body 2). It analyzes the axial, lateral, and torsional vibrations of the upper first mass body 1, and the axial and torsional vibrations of the lower second mass body 2. For a simplified model of the downhole drill string, see [link to model]. Figure 3 .

[0052] Assuming the well is a vertical well with a diameter equal to the drill bit diameter, the downhole drilling conditions are analyzed. First, based on Lagrange theory, a low-dimensional dynamic equation for the bottom drilling tool is established. This low-dimensional dynamic equation considers the collisions between the drill tool and the wellbore, the contact between the drill bit and the rock mass, and the frictional effects of the drilling fluid during drilling.

[0053] In one embodiment, the low-dimensional dynamic equations are expressed using the following expression:

[0054]

[0055] Where L represents the Lagrange function, L = TV, T represents the drill pipe kinetic energy (in MPa), V represents the drill pipe potential energy (in MPa), and q j This represents the angular displacement or displacement of the drill string, where j represents q. j The index of the variable element in the matrix. Let F represent the angular velocity or speed of the drill string, D represent the dissipation function, t represent time, and F represent the time. j This represents the resultant force state of the drill string under the j-th variable state.

[0056] The expression for calculating the generalized force F is:

[0057] [F]=[F o]+[F b ]+[F s ]+[F g (2)

[0058] Among them, [F o [F] indicates the active force applied to the drill pipe. s ] represents the interaction force between the drill pipe (first mass body 1) and the well wall, [F b [F] represents the force exerted by the rock mass on the drill bit (second mass body 2). g [] indicates the weight of the drill string assembly.

[0059] First, the contact force between the drill string and the wellbore [F] s The rotation of the drill string is affected; therefore, when establishing the drill string dynamics model, it is necessary to consider the contact state between the drill pipe and the well wall, simulate the collision law between the drill pipe and the well wall, and calculate the radial contact force F when the drill pipe collides with the well wall. r Tangential friction force F t This will reduce the radial contact force F r With tangential friction force F t After coupling, the contact force characteristic parameter F1 is formed in the Z-axis direction between the drill pipe and the well wall.

[0060] Secondly, in this embodiment of the invention, the contact force between the drill pipe and the well wall [F] s Includes: through radial contact force F r With tangential friction force F t The contact force characteristic parameter F1 formed by the coupling (see Figure 4 ) and the contact torque T1 between the wellbore and the drill pipe.

[0061] During the drilling process, the drill pipe becomes eccentric with the wellbore axis, and torsional buckling and lateral vibration occur during drill pipe rotation. When the drill pipe experiences severe lateral vibration, the drill pipe (first mass body 1) continuously contacts and collides with the well wall. Due to the lateral vibration of the drill pipe and the frictional resistance between the drill pipe and the well wall, a radial contact force F is generated between the drill pipe and the well wall. r .

[0062] The radial contact force F r This can be represented by the following expression:

[0063]

[0064] Where s represents the distance between the center of mass of the first mass body, the drill pipe, and the wellbore axis at time t. x and y represent the displacements of the drill pipe along the X-axis and Y-axis (in the drill pipe cross-section), respectively. F r The radial contact force r represents the force between the drill string and the wellbore. dThe radius of the well wall, r o K represents the drill pipe radius. h This indicates the stiffness of the well wall.

[0065] The tangential frictional force F between the drill pipe and the well wall t This can be represented by the following expression:

[0066]

[0067] Among them, F t μ represents the tangential frictional force between the drill string and the wellbore. r χ represents the coefficient of friction between the drill pipe and the wellbore, χ represents the steepness coefficient of friction, and tanh() represents the hyperbolic tangent function. These represent the speeds of the drill pipe along the X-axis and Y-axis, respectively. The angular velocity (rotation speed) of the drill pipe is represented by ψ, and ψ represents the angle between the centroid of the drill pipe section and the X-axis.

[0068] Furthermore, the torque T1 exerted by the wellbore on the drill pipe is expressed by the following expression:

[0069]

[0070] The axial force F1 between the drill pipe and the well wall, in its components along the X-axis and Y-axis of the drill pipe, is expressed by the following expression:

[0071]

[0072] Among them, F 1x F 1y These represent the components of the contact force characteristic parameter F1 in the X-axis and Y-axis directions, respectively.

[0073] Furthermore, in this embodiment of the invention, the interaction force [F] between the drill bit and the rock mass b This includes: the frictional torque T between the drill bit and the formation rock mass. fb And the axial force W between the drill bit and the formation rock mass b .

[0074] The interaction force between the drill bit and the rock mass [F] b Stick-slip vibration is one of the main factors causing drill bit vibration. The vibration of drill bits varies when drilling into different rock masses. When the hardness and plasticity of the rock increase, the drillability decreases, the mechanical drilling speed decreases, and the drill bit is prone to stick-slip vibration.

[0075] Furthermore, the frictional torque T between the drill bit and the formation rock mass fb This can be represented using the following expression:

[0076]

[0077] Among them, T fb This represents the frictional torque between the drill bit and the formation rock mass. Let be the state vector of the system. T represents the angular displacement at the tip of the drill string assembly, the angular velocity (rotation speed) at the tip of the drill string assembly, the angular displacement at the drill bit, and the angular velocity (rotation speed) at the drill bit, respectively. sb T represents the maximum static friction torque between the drill bit and the formation. sb =μ sb W ob R b R b W represents the drill bit radius. ob Indicates drilling pressure. μ represents the coefficient of dry friction between the drill bit and the formation during rotation. sb μ cb γ represents the static friction coefficient and the kinetic friction coefficient, respectively. b Represents a positive integer.

[0078] T eb (x) represents the torque accumulated in the drill string due to torsion caused by the rotary table when the drill bit sticks. When this torque T eb When (x) is greater than the maximum static friction torque, the drill bit breaks free from sticking, at which point T eb (x) satisfies the following condition:

[0079]

[0080] Among them, c t This represents the damping coefficient.

[0081] Furthermore, the axial force W between the drill bit and the formation rock mass b The instantaneous value can be calculated from the contact conditions at the drill bit:

[0082]

[0083] Where, x o Denotes the random coefficient, x z k represents the axial displacement of the drill bit. c W represents the rock mass stiffness. b This represents the axial force exerted by the rock mass on the drill bit (in the Z-axis direction).

[0084] Substituting the above expressions (2), (6), (7), (8), and (11) into expression (1) yields the motion equation of the bottom drill string, i.e., the downhole drill string dynamic model. This downhole drill string dynamic model is represented by the following expression:

[0085]

[0086] Where m1 represents the mass of the drill pipe as the first mass body, m2 represents the mass of the drill bit and drill collar as the second mass body, J1 and J2 represent the moments of inertia, φ1 and φ2 represent the angular displacements of the drill pipe and drill assembly (drill bit and drill collar), and x1 and x2 represent the displacements of the drill pipe and drill assembly in the X-axis direction. These represent the velocities of the drill pipe and drill string assembly in the X-axis direction, respectively. y1 and y2 represent the accelerations of the drill pipe and drill string assembly in the X-axis direction, respectively, and the displacements of the drill pipe and drill string assembly in the Y-axis direction, respectively. These represent the velocities of the drill pipe and drill string assembly in the Y-axis direction, respectively. Zi and Zj represent the accelerations of the drill pipe and drill string assembly in the Y-axis direction, respectively, and Zi and Zj represent the displacements of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the speeds of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the speeds of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the angular velocities of the drill pipe and the drill string assembly, respectively. V represents the angular acceleration of the drill pipe and the drill string assembly, respectively. o Ω represents the axial velocity at the drill pipe, and C represents the rotational speed at the drill pipe. a C t They represent the damping coefficients, k and k, respectively. a k represents the axial stiffness of the drill string. t This indicates torsional stiffness.

[0087] Thus, the downhole drilling dynamics model was constructed using the above expressions (1) to (12). As can be seen from the above expression (12), the downhole drilling dynamics model can identify the characteristics of the drilling motion law, which includes: the contact force characteristics between the drill pipe and the well wall, the torque of the well wall on the drill pipe, the axial force of the rock mass on the drill bit, and the torque of the rock mass on the drill bit.

[0088] Furthermore, in this embodiment of the invention, the downhole drilling tool dynamics model is used to characterize the contact force between the drill pipe and the wellbore [F]. s ] and the collision force between the drill bit and the rock mass [F b The constraint relationship model between ].

[0089] In addition, to ensure the accuracy of the downhole drilling tool dynamics model, the wellbore stability assessment method described in this embodiment of the invention further includes: optimizing the downhole drilling tool dynamics model based on the measured vibration signals of the drilled well or drilled section and the corresponding drilling parameters, so as to use the optimized model to calculate the contact force between the drill pipe and the wellbore in step S120.

[0090] like Figure 2 As shown, the optimization process for the downhole drilling tool dynamics model includes: First, based on the drilling parameters of the drilled well or drilled section, the simulated drilling tool motion characteristics are calculated using the downhole drilling tool dynamics model to be optimized, and the contact force between the drill pipe and the well wall is calculated from the simulated drilling tool motion characteristics; then, the simulated contact force between the drill pipe and the well wall is compared with the contact force corresponding to the measured vibration signal of the drilled well or drilled section, and the model coefficients in the downhole drilling tool dynamics model are optimized based on the comparison results to obtain the optimized downhole drilling tool dynamics model.

[0091] By analyzing the measured vibration data and the drill string motion law output by simulation, and comparing the differences between the simulation and the field vibration data, the relevant parameters in the model are corrected when the current deviation difference does not meet the preset conditions, and the downhole drill string dynamic model is optimized so that the optimized downhole drill string dynamic model can be output when the preset conditions are met.

[0092] More specifically, in step S120, firstly, based on the measured vibration signal obtained in step S110 and the current drilling parameters, the downhole drill string dynamics model is solved to obtain the corresponding drill string motion characteristics.

[0093] In this embodiment of the invention, combined with the on-site drilling parameters, the downhole drill string dynamics model is adjusted and optimized, initial parameters are set, relevant drilling parameters are input, and the downhole drill string dynamics model is solved using, for example, the Newmark method, thereby simulating and analyzing the characteristics of the drill string motion during the bottom drill string drilling process within 0-t minutes.

[0094] During the drilling process, the drilling parameters of the drill string vary at different drilling stages, and the overall structure of the drill string is constantly adjusted. Using the optimized downhole drill string dynamics model, the vibration law and the collision law between the drill string and the well wall during the drilling process are analyzed and calculated.

[0095] Then, based on the contact force characteristics between the drill pipe and the well wall obtained from the drill string motion characteristics obtained after solving the downhole drilling dynamics model, the tangential friction force F between the drill pipe and the well wall is calculated. t To obtain the radial contact force F between the drill pipe and the well wall r To use the currently calculated radial contact force F r As the result of the current contact force calculation, the process proceeds to step S130.

[0096] Step S130: The contact force F between the drill pipe and the wellbore calculated in step S120. r The collision stress, which characterizes the collision intensity between the drill pipe and the well wall, is calculated.

[0097] Specifically, in step S130, firstly, based on the elastic modulus and Poisson's ratio of the drill pipe obtained during real-time drilling, and the elastic modulus and Poisson's ratio of the well wall, the coupled elastic modulus E after the drill pipe comes into contact with the well wall is calculated. * Then, based on the coupled elastic modulus E * The contact radius R between the drill pipe and the well wall and the contact force F between the drill pipe and the well wall r The corresponding collision stress is calculated.

[0098] In this embodiment of the invention, based on Hertzian contact theory and its contact rules, the corresponding collision stress is calculated by calculating the contact area between the drill pipe and the well wall. The contact and collision principle between the drill pipe and the well wall is as follows: Figure 5 As shown. At the same time, the drill pipe also generates impact force and shear stress on the rock mass. When the intensity of the impact force and shear stress exceeds the rock mass's bearing limit, it leads to damage to the wellbore rock mass.

[0099] If the two objects in contact (drill pipe and well wall) are both elastic, then the equivalent coupled elastic modulus E * Then it can be represented by the following expression:

[0100]

[0101] Where υ1 and υ2 represent the Poisson's ratios of the drill pipe and the well wall, respectively, and E1 and E2 represent the elastic moduli of the drill pipe and the well wall, respectively.

[0102] Furthermore, the contact radius R between the drill pipe and the well wall is expressed by the following expression:

[0103]

[0104] Where R represents the contact radius between the drill pipe and the well wall, r o Indicates the drill pipe radius, r d Indicates the radius of the well wall.

[0105] Furthermore, the pressure at the center of the contact area is taken as the collision stress p. o The collision stress is expressed by the following expression:

[0106]

[0107] Where p0 represents the collision stress.

[0108] After the collision stress calculation is completed, proceed to step S140.

[0109] Step S140 involves a quantitative evaluation of the rock mass strength of the current wellbore based on the dynamic collision stress obtained in step S130 during the drilling process.

[0110] In this embodiment of the invention, dynamic collision stress represents the collision stress at different times within a specified time period during the drilling process. This allows for a quantitative evaluation of the rock mass strength at the corresponding drilling time based on the collision stress at different times.

[0111] Specifically, in step S140, firstly, based on the dynamic collision stress, the number of times the collision stress exceeds the preset stress threshold is counted and recorded as the number of collisions; then, based on the dynamic collision stress and the number of collisions, the stability of the current well wall is calculated.

[0112] After calculating the collision stress amplitude, the rainflow counting method is used to count the number of times the collision stress between the drill string and the well wall exceeds the preset stress threshold within a specified time period. This number is recorded as the number of collisions. The recorded number of collisions and the maximum collision stress value of the dynamic collision stress within the specified time period are then used to calculate the current well wall stability (i.e., rock mass stability).

[0113] In the first embodiment, the drill string collides with the well wall, and the collision stress is large, exceeding the bearing capacity of the well wall rock mass, resulting in the destruction of the well wall rock mass.

[0114] Therefore, when the collision stress exceeds the preset ultimate stress threshold of the well wall, it indicates that the well wall rock mass has failed, and the rock mass stability calculation result is obtained using the first safety quantification level expression. In this embodiment of the invention, the ultimate stress threshold of the well wall is greater than the aforementioned preset stress threshold. This ultimate stress threshold of the well wall is the maximum stress capacity that the well wall rock mass can withstand to cause rock mass failure.

[0115] More specifically, when the maximum collision stress within a specified time period exceeds the preset wellbore ultimate stress threshold, the wellbore stability calculation result is obtained using the first safety quantification level expression.

[0116] Specifically, the expression for the first security quantification level is:

[0117]

[0118] Where σ represents the rock mass strength (this rock mass strength data can be obtained from adjacent well data); n is the wellbore stability calculation result, i.e., the safety factor.

[0119] In the second embodiment, the drill string collides with the well wall, and the collision stress is small and does not exceed the bearing capacity of the well wall rock mass. However, multiple collisions occur between the drill string and the well wall (e.g., more than 10,000 collisions), which leads to a decrease in the strength of the well wall rock mass and damage.

[0120] Therefore, if the collision stress does not exceed the preset well wall ultimate stress threshold and the number of collisions exceeds the first threshold, it indicates that the strength of the well wall rock mass has decreased and it has been damaged. Thus, the well wall stability calculation result is obtained by using the second safety quantification level expression.

[0121] More specifically, when the maximum collision stress within a specified time period does not exceed the preset wellbore ultimate stress threshold and the number of collisions exceeds the first threshold, the rock mass stability calculation result is obtained using the second safety quantification level expression.

[0122] Specifically, the expression for the second security quantification level is:

[0123]

[0124] In the third embodiment, the drill string collides with the well wall, and the collision stress is small and does not exceed the bearing capacity of the well wall rock mass. However, multiple collisions occur between the drill string and the well wall (e.g., the number of collisions exceeds 100), which leads to a decrease in the strength of the well wall rock mass and causes damage. Thick-walled hollow cylinder cyclic loading (fatigue) test.

[0125] Therefore, if the collision stress does not exceed the preset limit stress threshold of the well wall and the number of collisions exceeds the second threshold, it indicates that the strength of the well wall rock mass has decreased and the wall thickness is affected by fatigue. Thus, the third safety quantification level expression is used to obtain the well wall stability calculation result.

[0126] In this embodiment of the invention, the second counting threshold is preferably one percent of the first counting threshold. For example, the first counting threshold is 10000, and the second counting threshold is 100.

[0127] Specifically, the expression for the third security quantification level is:

[0128]

[0129] On the other hand, based on the above-mentioned wellbore stability assessment method, this embodiment of the invention also provides a system for assessing the impact of drill string vibration on wellbore stability (also referred to as a "wellbore stability assessment system"). This wellbore stability assessment system is used to implement the above-mentioned wellbore stability assessment method.

[0130] Figure 6 This is a schematic diagram of a system for evaluating the impact of drill string vibration on wellbore stability, according to an embodiment of this application. Figure 6 As shown, the wellbore stability assessment system of this invention includes: a basic data acquisition module 601, a contact force analysis module 602, a collision stress generation module 603, and a rock mass stability calculation module 604.

[0131] Specifically, the basic data acquisition module 601 is implemented according to the method described in step S110 above, and is configured to acquire the vibration signal of the drill string surface during real-time drilling; the contact force analysis module 602 is implemented according to the method described in step S120 above, and is configured to calculate the contact force between the drill string and the well wall based on the current vibration signal, combined with the current drilling parameters, and using the downhole drill string dynamics model; the collision stress generation module 603 is implemented according to the method described in step S130 above, and is configured to calculate the collision stress characterizing the collision intensity between the drill string and the well wall based on the contact force; the rock mass stability calculation module 604 is implemented according to the method described in step S140 above, and is configured to quantitatively evaluate the stability of the current well wall based on the dynamic collision stress during drilling.

[0132] Furthermore, based on the aforementioned wellbore stability assessment method, this invention provides a computer-readable storage medium. This storage medium stores a computer program, which is executed to run a method for assessing the impact of drill string vibration on wellbore stability. The computer program is capable of executing computer instructions, which include computer program code. The computer program code can be in the form of source code, object code, executable files, or some intermediate form.

[0133] Computer-readable storage media can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0134] It should be noted that the contents of computer-readable storage media may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, the contents may be appropriately increased or decreased according to the requirements of legislation and patent practice. In other jurisdictions, computer-readable storage media may not include electrical carrier signals and telecommunication signals.

[0135] This invention discloses a method and system for evaluating the impact of drill string vibration on wellbore stability. This method and system improve upon existing wellbore stability assessment methods, considering the influence of drill string vibration on wellbore stability. By establishing a bottom drill string dynamics model, the relationship between the drill string and the wellbore is measured, providing a strong basis for drilling optimization. The wellbore stability assessment results provided by this invention can effectively reduce safety risks, ensure the safety of drilling personnel, avoid additional reinforcement measures and the use of more drilling materials, improve the efficiency of oil and gas exploration and development, shorten the development cycle, reduce development costs, and simultaneously increase oil and gas recovery and production while reducing drilling costs and improving economic efficiency. It addresses potential wellbore collapse and blockage problems caused by wellbore instability during drilling, avoids drill bit burial and stuck drill bit accidents, significantly improves drilling progress and success rate, and thus significantly increases drilling success rate and reduces accidents.

[0136] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0137] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0138] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0139] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0140] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0141] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for evaluating the impact of drill string vibration on wellbore stability, characterized in that, include: Obtain vibration signals from the drill string surface during the drilling process; Based on the vibration signal and the current drilling parameters, the contact force between the drill pipe and the well wall is calculated using the downhole drilling tool dynamics model. Based on the contact force, calculate the collision stress that characterizes the collision intensity between the drill pipe and the well wall; The stability of the wellbore is quantitatively evaluated based on the dynamic collision stress during the drilling process.

2. The method according to claim 1, characterized in that, The step of calculating the contact force between the drill pipe and the wellbore based on the vibration signal, combined with the current drilling parameters, and using a downhole drilling tool dynamics model includes: Based on the vibration signal and current drilling parameters, the downhole drilling tool dynamics model is solved to obtain the characteristics of the drilling tool motion law. The characteristics of the drilling tool motion law include the contact force characteristics between the drill pipe and the well wall, the torque of the well wall on the drill pipe, the axial force of the rock mass on the drill bit, and the torque of the rock mass on the drill bit. The downhole drilling tool dynamics model is a constraint relationship model that characterizes the contact force between the drill pipe and the well wall and the collision force between the drill bit and the rock mass. Based on the contact force characteristics between the drill pipe and the well wall, the radial contact force is obtained by calculating the tangential friction between the drill pipe and the well wall, and the radial contact force is used as the current contact force calculation result.

3. The method according to claim 1 or 2, characterized in that, The downhole drilling tool dynamics model is represented by the following expression: Where m1 represents the mass of the drill pipe as the first mass body, m2 represents the mass of the drill bit and drill collar as the second mass body, J1 and J2 represent the moments of inertia, φ1 and φ2 represent the angular displacements of the drill pipe and drill assembly, and x1 and x2 represent the displacements of the drill pipe and drill assembly in the X-axis direction. These represent the velocities of the drill pipe and drill string assembly in the X-axis direction, respectively. y1 and y2 represent the accelerations of the drill pipe and drill string assembly in the X-axis direction, respectively, and the displacements of the drill pipe and drill string assembly in the Y-axis direction, respectively. These represent the velocities of the drill pipe and drill string assembly in the Y-axis direction, respectively. Zi and Zj represent the accelerations of the drill pipe and drill string assembly in the Y-axis direction, respectively, and Zi and Zj represent the displacements of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the speeds of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the speeds of the drill pipe and drill string assembly in the Z-axis direction, respectively. These represent the angular velocities of the drill pipe and the drill string assembly, respectively. V represents the angular acceleration of the drill pipe and the drill string assembly, respectively. o The axial velocity at the drill pipe is represented by Ω, time is represented by t, and the rotational speed at the drill pipe is represented by C. a C t They represent the damping coefficients, k and k, respectively. a k represents the axial stiffness of the drill string. t F0 represents the torsional stiffness, and F0 represents the axial tensile force applied to the drill pipe from the top. 1x F 1y W represents the components of the contact force characteristic parameter F1 in the X-axis and Y-axis directions, respectively. b T represents the axial force exerted by the rock mass on the drill bit. fb T1 represents the torque exerted by the rock mass on the drill bit, and T2 represents the torque exerted by the well wall on the drill pipe. The contact force characteristic parameter is expressed by the following expression: Where ψ represents the angle between the centroid of the drill pipe section and the X-axis, and F r F represents the radial contact force between the drill pipe and the wellbore. t This represents the tangential frictional force between the drill pipe and the well wall.

4. The method according to any one of claims 1 to 3, characterized in that, The method further includes: optimizing the downhole drill string dynamics model based on measured vibration signals and drilling parameters from the drilled well or drilled section, so as to use the optimized model to calculate the contact force, including: Based on the drilling parameters of the drilled well or drilled section, the contact force for simulation is calculated using the downhole drill string dynamics model to be optimized; The measured vibration signals of the drilled well or drilled section are compared with the simulated contact force, and the model coefficients in the downhole drilling tool dynamics model are optimized based on the comparison results.

5. The method according to any one of claims 1 to 4, characterized in that, The step of calculating the collision stress, which characterizes the collision intensity between the drill pipe and the wellbore, based on the contact force includes: Based on the elastic modulus and Poisson's ratio of the drill pipe and the well wall obtained during real-time drilling, the coupled elastic modulus after the drill pipe comes into contact with the well wall is calculated. The collision stress is calculated based on the coupled elastic modulus, the contact radius between the drill pipe and the well wall, and the contact force, wherein the collision stress is expressed by the following expression: Where p0 represents the collision stress, F r E represents radial contact force. * R represents the coupled elastic modulus, and R represents the contact radius between the drill pipe and the well wall.

6. The method according to claim 5, characterized in that, The coupled elastic modulus is calculated using the following expression: Where υ1 and υ2 represent the Poisson's ratios of the drill pipe and the well wall, respectively, and E1 and E2 represent the elastic moduli of the drill pipe and the well wall, respectively. The contact radius between the drill pipe and the well wall is calculated using the following expression: Where, r o Indicates the drill pipe radius, r d Indicates the radius of the well wall.

7. The method according to any one of claims 1 to 6, characterized in that, The step of quantitatively evaluating the rock mass strength of the current wellbore based on the dynamic collision stress during drilling includes: Based on the dynamic collision stress, the number of times the collision stress exceeds a preset stress threshold is counted and recorded as the collision count; The stability of the current wellbore is calculated based on the dynamic collision stress and the number of collisions.

8. The method according to claim 7, characterized in that, When the collision stress exceeds a preset wellbore ultimate stress threshold, it indicates wellbore rock failure. Therefore, the wellbore stability calculation result is obtained using a first safety quantification level expression, which is: σ represents the rock mass strength, p o The value represents the collision stress, and n represents the safety factor. The ultimate stress threshold of the well wall is greater than the preset stress threshold. If the collision stress does not exceed the preset wellbore ultimate stress threshold and the number of collisions exceeds the first threshold, it indicates that the wellbore rock mass strength has decreased and failure has occurred. Therefore, the wellbore stability calculation result is obtained using the second safety quantification level expression, which is: If the collision stress does not exceed the preset wellbore ultimate stress threshold and the number of collisions exceeds the second threshold, it indicates that the wellbore rock mass strength has decreased and is affecting the wall thickness. Therefore, the wellbore stability calculation result is obtained using the third safety quantification level expression, which is: The second threshold number is less than the first threshold number, wherein, The second number threshold is one percent of the first number threshold.

9. A system for evaluating the impact of drill string vibration on wellbore stability, characterized in that, include: The basic data acquisition module is configured to acquire vibration signals on the surface of the drill bit during the drilling process; The contact force analysis module is configured to calculate the contact force between the drill pipe and the well wall based on the vibration signal, combined with the current drilling parameters, and using the downhole drilling tool dynamics model. The collision stress generation module is configured to calculate the collision stress, which characterizes the collision intensity between the drill pipe and the well wall, based on the contact force. The rock mass stability calculation module is configured to quantitatively evaluate the stability of the current wellbore based on the dynamic collision stress during the drilling process.

10. A computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the method as described in any one of claims 1 to 8.

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