Gas well tubular column flow-induced vibration additional stress quantitative evaluation method

Abstract

The invention relates to a gas well tubular column flow-induced vibration additional stress quantitative evaluation method, which belongs to the technical field of oil and gas industrial exploitation, and comprises the following steps of: quantitatively calculating and determining a flow-induced vibration excitation load acting on a tubular column based on actual production parameters of a gas well; the excitation load at least comprises narrow-band random excitation generated by vortex-induced vibration and wide-band random excitation generated by turbulence buffeting, establishing a three-dimensional finite element model considering the contact nonlinearity of the tubular column and a wellbore based on an actual wellbore trajectory and tubular column combination, and obtaining dynamic displacement and dynamic stress of each node of the tubular column, all links from an excitation source, structural response to stress evaluation adopt mathematical model quantitative calculation, empirical and qualitative limitations of a traditional method are avoided, the result is more accurate and reliable, an established tubular column system dynamic model fully considers a well track and contact nonlinearity, an excitation load comprises a main flow-induced vibration mechanism, and the flow-induced vibration is more accurate and reliable. And the analysis result can more truly reflect the actual working state of the tubular column.

Description

Technical Field

[0001] This invention relates to a method for quantitatively evaluating the additional stress caused by flow-induced vibration in gas well tubing, belonging to the field of oil and gas industry extraction technology. Background Technology

[0002] In the field of oil and gas extraction, the well string (including tubing, casing, and other key downhole components) serves as the core channel connecting the formation and the surface. Its long-term safe and stable operation directly determines the gas well extraction efficiency and operational safety. During gas well production, high-speed natural gas continuously flows through the inside of the string. This high-speed fluid flow generates complex fluid-structure interaction with the string structure, thereby inducing flow-induced vibration. This type of vibration mainly includes three core types: first, vortex-induced vibration, caused by alternating vortices detaching as the fluid flows around the string; second, turbulent buffeting, originating from the turbulent pulsation characteristics of the fluid itself; and third, acoustic resonance occurring under special operating conditions, formed by the coupling of the natural acoustic frequency of the gas column within the string and the vortex shedding frequency.

[0003] The dynamic additional stress generated by flow-induced vibration will superimpose with the static stress borne by the tubing during service (such as the tubing's own weight, internal and external pressure differences, thermal stress caused by temperature changes, and residual stress from manufacturing and installation), making stress concentration points in the tubing high-risk areas for fatigue failure. This superposition effect will accelerate the initiation and propagation of fatigue cracks, ultimately easily leading to serious accidents such as thread punctures, tubing fractures, and natural gas leaks. This will not only cause huge economic losses but also bring great safety hazards and environmental risks, severely restricting the efficient development and long-term stable production of gas wells.

[0004] Currently, the mechanical analysis methods used in the industry for gas well tubing have significant limitations, making it difficult to meet the accurate safety assessment requirements of engineering projects. These limitations are mainly reflected in the following three aspects: First, the simplified models are out of touch with actual working conditions. Existing analyses often simplify the tubing string in complex wellbore trajectories as a two-dimensional beam or rod model, ignoring the three-dimensional wellbore trajectory characteristics of different well types such as vertical, directional, and horizontal wells, and failing to accurately characterize the complex nonlinear contact between the tubing string and casing. Furthermore, the simulation of the actual operating mechanisms of the tool string, such as the elastic support of the centralizer and the fixed constraint of the packer, is insufficient, resulting in the model failing to reflect the true stress state of the tubing string downhole.

[0005] Secondly, the excitation loads are not comprehensively considered and lack quantitative characterization. Most existing technologies only focus on the steady flow field forces under average flow velocity, while the essence of flow-induced vibration is dynamic excitation. Key dynamic load parameters such as eddy shedding frequency and turbulent pulsating pressure are not systematically incorporated into the analysis. Even in some studies that involve relevant excitations, they are mostly qualitative descriptions without quantitative quantification through mathematical models. This leads to a large deviation between the vibration excitation and actual working conditions, making it impossible to provide reliable input for subsequent stress analysis.

[0006] Third, the analysis process is fragmented and lacks a closed-loop system. Currently, fluid dynamics analysis, structural dynamics response calculation, and fatigue strength assessment are independent of each other, lacking a complete, systematic, and quantitative evaluation process. For example, vibration parameters obtained from fluid dynamics analysis are difficult to directly apply to structural stress calculation, and fatigue assessment does not accurately calculate the additional stress caused by actual flow-induced vibration. Ultimately, this leads to significant deviations between the analysis results and actual engineering conditions, failing to provide scientific and effective technical support for tubing life prediction, risk warning, and well workover decisions.

[0007] Therefore, the industry urgently needs a closed-loop quantitative analysis method that can overcome the limitations of existing technologies and realize the entire process from the quantification of gas flow dynamic excitation and the calculation of tubing vibration response to the extraction of additional stress and fatigue life assessment. This method would accurately evaluate the additional stress of flow-induced vibration in gas well tubing and provide reliable technical support for the formulation of gas well safety production systems, proactive risk prevention and control, and optimized tubing design. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a systematic, accurate, and engineering-applicable quantitative evaluation method for the additional stress of flow-induced vibration in gas well tubing. This method enables closed-loop quantitative analysis of the entire process, from quantifying dynamic gas flow excitation and calculating tubing vibration response to extracting additional stress and assessing fatigue life, thereby providing a scientific basis for the formulation of safety production systems and risk warnings for gas wells.

[0009] This invention achieves the above objective through the following technical solution: a method for quantitatively evaluating the additional stress caused by flow-induced vibration in gas well tubing, comprising the following sequential steps: S1. Based on the actual production parameters of the gas well, quantitatively calculate and determine the flow-induced vibration excitation load acting on the tubing string. The excitation load includes at least a narrow-band random excitation generated by vortex-induced vibration and a broadband random excitation generated by turbulent buffeting. S2. Based on the actual well trajectory and tubing combination, a three-dimensional finite element model considering the nonlinearity of the contact between the tubing and the wellbore is established, and modal analysis is performed to obtain the dynamic characteristics of the tubing in water. S3. The flow-induced vibration excitation load quantitatively characterized in step S1 is applied to the three-dimensional finite element model established in step S2 as input conditions. The vibration response of the pipe column is calculated by dynamic analysis method to obtain the dynamic displacement and dynamic stress of each node of the pipe column. S4. Extract the dynamic stress calculated in step S3 as the additional stress of flow-induced vibration, and synthesize it with the static stress of the tubing. Based on the synthesized stress, evaluate the fatigue life of key parts of the tubing.

[0010] Preferably, in step S1, the specific process of quantitatively calculating the flow-induced vibration excitation load includes: S1.1. Based on the fluid velocity V and the characteristic diameter D of the tubing, the vortex shedding frequency f_v is calculated using the Strouhal number St. The formula is f_v = St V / D; S1.2 Determine the power spectral density of vortex-induced force using an empirical model of vortex-induced vibration; S1.3. The power spectral density of turbulent pressure fluctuations is determined using the empirical spectrum model of turbulent buffeting.

[0011] Preferably, the empirical spectrum model for turbulent buffeting is a Liepmann spectrum or a Modified API Spectrum.

[0012] Preferably, in step S1, the excitation load further includes acoustic resonance excitation; when the acoustic natural frequency of the gas column in the tubing is coupled with the vortex shedding frequency f_v, the acoustic resonance excitation needs to be quantitatively characterized.

[0013] Preferably, the three-dimensional finite element model uses three-dimensional beam elements to simulate the pipe column, and accurately sets the contact pairs between the pipe column and the casing to simulate the constraint effect of the centralizer and packer on the pipe column.

[0014] Preferably, in step S3, the kinetic analysis method is power spectral density analysis, used to calculate the root mean square value of the dynamic response of the tubing.

[0015] Preferably, in step S3, the dynamic analysis method is transient dynamic analysis, used to calculate the time history curve of the dynamic response of the tubing.

[0016] Preferably, the fatigue life assessment adopts Miner's linear cumulative damage rule and combines it with the SN curve of the tubular material for prediction.

[0017] Preferably, the gas well production parameters include gas production, wellhead pressure, wellhead temperature, fluid composition, and tubing assembly structure.

[0018] The beneficial effects of this invention are: 1. From the excitation source and structural response to stress assessment, each link is quantitatively calculated using mathematical models, avoiding the empirical and qualitative limitations of traditional methods. The results are more accurate and reliable. The established dynamic model of the tubing system fully considers the wellbore trajectory and contact nonlinearity. The excitation load includes the main flow-induced vibration mechanism, making the analysis results more realistically reflect the actual working state of the tubing.

[0019] 2. The core advantage of this method is that it can quantitatively predict the fatigue life of the tubing string, thereby providing key data support for the optimization of gas well production, risk warning and scientific well workover decision-making, and realizing proactive safety management. The method has a clear principle and can be applied to various well types such as vertical wells, directional wells and horizontal wells, as well as the flow-induced vibration assessment of different tubing string combinations such as conventional production tubing strings and velocity tubing strings. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the quantitative evaluation process for the additional stress caused by flow-induced vibration in gas well tubing, as described in this invention.

[0021] Figure 2 This is a flowchart of the sub-process for quantitative calculation of flow-induced vibration excitation load in this invention.

[0022] Figure 3 This is a flowchart of the three-dimensional finite element model establishment and modal analysis of the present invention.

[0023] Figure 4 This is a flowchart of the sub-process for calculating the vibration response of the tubular column in this invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figures 1-4 As shown, the quantitative evaluation method for additional stress caused by flow-induced vibration in gas well tubing includes the following sequential steps: S1. Based on the actual production parameters of the gas well, quantitatively calculate and determine the flow-induced vibration excitation load acting on the tubing string. The excitation load includes at least a narrow-band random excitation generated by vortex-induced vibration and a broadband random excitation generated by turbulent buffeting. S2. Based on the actual well trajectory and tubing combination, a three-dimensional finite element model considering the nonlinearity of the contact between the tubing and the wellbore is established, and modal analysis is performed to obtain the dynamic characteristics of the tubing in water. S3. The flow-induced vibration excitation load quantitatively characterized in step S1 is applied to the three-dimensional finite element model established in step S2 as input conditions. The vibration response of the pipe column is calculated by dynamic analysis method to obtain the dynamic displacement and dynamic stress of each node of the pipe column. S4. Extract the dynamic stress calculated in step S3 as the additional stress of flow-induced vibration, and synthesize it with the static stress of the tubing. Based on the synthesized stress, evaluate the fatigue life of key parts of the tubing.

[0026] Example 1: Quantitative evaluation of additional stress caused by flow-induced vibration in conventional production tubing of vertical wells Suitable for conventional production tubing strings, tubing and casing assemblies, tool strings including centralizers and packers, for vertical wellbore structures, ensuring stable gas production (10×10). 4 m 3 / d), wellhead pressure 15MPa, wellhead temperature 80℃, the main components of the fluid are 95% methane and a small amount of 5% ethane, and there is no obvious acoustic resonance coupling phenomenon.

[0027] S1: Quantitative Calculation of Flow-Induced Vibration Excitation Load S1.1: Given the characteristic diameter of the tubing D = 73 mm, the average fluid velocity V = 12 m / s, and the Stroha number St = 0.2, the vortex shedding frequency fᵥ = 0.2 × 12 / 0.073 ≈ 32.88 Hz is calculated using the formula fᵥ = St × V / D.

[0028] S1.2: Using the API-recommended empirical model of vortex-induced vibration, combined with the surface roughness of the tubing (0.05 mm) and the fluid density (18 kg / m³), the power spectral density of the vortex-induced force was determined to be 5 × 10⁻⁶. -3 N 2 / Hz.

[0029] S1.3: The empirical spectral model for turbulent buffeting was Modified API Spectrum. Inputting the fluid turbulence intensity (8%) and characteristic length parameters, the power spectral density of the turbulent pressure fluctuation was obtained as 3 × 10⁻⁶. -4 Pa 2 / Hz.

[0030] S2: Three-dimensional finite element model establishment and modal analysis Based on the vertical well trajectory (vertical depth 2000m, no well deviation) and tubing string combination (N80 tubing and P110 casing, centralizer spacing 50m, packer located at a depth of 1500m), a three-dimensional finite element model was established using ANSYS software.

[0031] The tubing was simulated using BEAM188 3D beam elements, with precise settings for the contact pairs between the tubing and the casing, and a normal contact stiffness of 1×10⁻⁶. 8 The coefficient of friction is N / m and tangential friction is 0.15, which characterizes the supporting constraint of the centralizer and the fixing constraint of the packer.

[0032] Modal analysis was performed, and the first five natural frequencies of the tubing in water were found to be 12Hz, 28Hz, 35Hz, 52Hz, and 68Hz, with a damping ratio of 0.02.

[0033] S3: Vibration Response Calculation The power spectral density analysis method is used to apply the vortex-induced force power spectral density and turbulent pressure fluctuation power spectral density obtained in S1 as input loads to the fluid contact surface of the tubular column.

[0034] By solving the dynamics, the root mean square value of dynamic displacement (maximum 1.2 mm) and the root mean square value of dynamic stress (maximum 85 MPa) of each node of the tubing were obtained.

[0035] S4: Additional Stress Synthesis and Fatigue Life Assessment The dynamic stress (maximum 85 MPa) in S3 is extracted as the additional stress of flow-induced vibration, and superimposed with the static stress of the tubing (maximum 120 MPa combined from self-weight, internal and external pressure, and thermal stress) to obtain a maximum combined stress of 205 MPa.

[0036] The tubing material is N80 steel, and its SN curve is taken according to the API 5C3 standard. Using the Miner linear cumulative damage rule and combined with the planned production cycle of 20 years for the gas well, the fatigue life of the key parts of the tubing (centralizer contact point and threaded joint) is calculated to be 18.5 years, which meets the requirements for safe production.

[0037] Example 2: Quantitative Evaluation of Additional Stress Caused by Flow-Induced Vibration in Horizontal Well Velocity Strings A velocity string (φ50.8mm coiled tubing, no packer, centralizer spacing 30m) suitable for horizontal wells (3° / 100m build-up rate, 800m horizontal section length) with relatively small fluctuations in gas production (8×10). 4 -12×10 4 m 3 / d), wellhead pressure 20MPa, wellhead temperature 90℃, fluid contains 92% methane, 6% propane, and 2% hydrogen sulfide, with slight turbulent oscillations dominating the vibration.

[0038] S1: Quantitative Calculation of Flow-Induced Vibration Excitation Load S1.1: Characteristic diameter of tubing D = 50.8 mm, average fluid velocity V = 18 m / s (horizontal section velocity amplification), St is taken as 0.22, and the surface roughness correction value of coiled tubing is used to calculate the vortex shedding frequency fᵥ = 0.22 × 18 / 0.0508 ≈ 78.74 Hz.

[0039] S1.2: The Sarpkaya vortex-induced vibration empirical model is adopted, considering the surface roughness of the tubing (0.1 mm) and fluid density (22 kg / m³) caused by hydrogen sulfide corrosion. 3 The power spectral density of the vortex-induced force was determined to be 8 × 10⁻⁶. -3 N 2 / Hz.

[0040] S1.3: The empirical spectral model for turbulent buffeting uses the Liepmann spectrum. With an input fluid turbulence intensity of 12%, the power spectral density of the turbulent pressure fluctuation is 6 × 10⁻⁶. -4 Pa 2 / Hz.

[0041] S2: Three-dimensional finite element model establishment and modal analysis Based on actual wellbore trajectory data (vertical section depth 1500m, build-up section 300m, horizontal section 800m) and velocity string combination, a three-dimensional finite element model was established using ABAQUS software.

[0042] The tubing column was simulated using B31 beam elements, and the contact pairs between the tubing column and the casing were set (normal contact stiffness 8×10). 7 (N / m, tangential friction coefficient 0.12), accurately simulating the elastic support effect of the horizontal section centralizer.

[0043] Modal analysis results show that the first five natural frequencies of the tubing in water are 25Hz, 48Hz, 72Hz, 95Hz, and 110Hz, with a damping ratio of 0.025.

[0044] S3: Vibration Response Calculation Transient dynamic analysis was employed, with a time step set to 1×10⁻⁶. -4 s, simulation duration 10s, input dynamic excitation load in S1.

[0045] The dynamic displacement time history curve of the horizontal section of the tubing was calculated, with a maximum peak value of 2.1 mm, and the dynamic stress time history curve had a maximum peak value of 110 MPa.

[0046] S4: Additional Stress Synthesis and Fatigue Life Assessment The dynamic stress peak of 110 MPa was extracted as additional stress and superimposed with the static stress (the maximum combined stress of the horizontal section's self-weight bending stress and internal and external pressure stress, which is 135 MPa), resulting in a maximum combined stress of 245 MPa.

[0047] The velocity tubing material is Q345 steel. Its actual SN curve (corrected by hydrogen sulfide stress corrosion test) was obtained. Using Miner's rule, the fatigue life was calculated to be 12.3 years. It is recommended to carry out flaw detection of the tubing every 10 years.

[0048] Example 3: Quantitative Evaluation of Additional Stress Caused by Flow-Induced Vibration in Acoustic Resonance Tubing of Directional Wells Suitable for directional wells with a build-up rate of 2° / 100m (well inclination angle 45°, depth 2500m), the tubing string assembly consists of tubing (φ89mm), casing (φ139.7mm), packer (1000m depth), and centralizers (spaced 40m), with a gas well production rate of 15×10⁻⁶ m. 4 m 3 / d, wellhead pressure 25MPa, wellhead temperature 95℃, fluid composition 90% methane, 6% ethane and 4% nitrogen. It was predicted that there is coupling between the acoustic natural frequency and vortex shedding frequency of the gas column in the tubing. The acoustic natural frequency is 33Hz and the vortex shedding frequency is 32.5Hz.

[0049] S1: Quantitative Calculation of Flow-Induced Vibration Excitation Load S1.1: Characteristic diameter of the tubing D=89mm, fluid velocity V=15m / s, St is taken as 0.21, the calculated vortex shedding frequency fᵥ=0.21×15 / 0.089≈35.62Hz.

[0050] S1.2: An empirical model of vortex-induced vibration is adopted, considering an acoustic resonance correction factor of 1.3, and a fluid density of 22 kg / m³. 3 The power spectral density of the vortex-induced force was determined to be 9 × 10⁻⁶. -3 N 2 / Hz.

[0051] S1.3: The empirical spectrum of turbulent buffeting was obtained using Modified API Spectrum, with an input turbulence intensity of 10%, resulting in a power spectral density of 4 × 10⁻⁶ for turbulent pressure fluctuations. -4 Pa 2 / Hz.

[0052] S1.4: Quantitative Characterization of Acoustic Resonance Excitation: Based on the Natural Acoustic Frequency f of the Air Column a =33Hz, the acoustic resonance pressure amplitude ΔP = 0.1 × P_wellhead (P_wellhead = 25MPa) is calculated, resulting in ΔP = 2.5MPa. Its power spectral density is determined to be 1.2 × 10^-3 Hz according to the empirical acoustic resonance model. 6 Pa 2 / Hz (concentrated in the 32-34Hz frequency band).

[0053] S2: Three-dimensional finite element model establishment and modal analysis Based on the actual trajectory data of the directional well (vertical section 1000m, build-up section 500m, stabilization section 1000m), a three-dimensional finite element model was established using ANSYS Workbench, and the tubing was simulated using BEAM189 elements.

[0054] Precisely set the contact pairs between the tubing string and the casing (fixed constraint at the packer, normal contact stiffness of 1.5 × 10⁻⁶ at the centralizer). 8 (N / m, tangential friction coefficient 0.18), simulating the constraint effect of the tool string.

[0055] Modal analysis revealed that the first five natural frequencies of the tubing in water were 18Hz, 33Hz, 49Hz, 65Hz, and 82Hz, with a damping ratio of 0.03.

[0056] S3: Vibration Response Calculation The power spectral density analysis method is used to superimpose the power spectral densities of vortex-induced force, turbulent pressure fluctuation, and acoustic resonance excitation as input loads, which are then applied to the contact area between the inner and outer walls of the tubing.

[0057] The calculated root mean square value of dynamic displacement of the inclined section of the tubular column is 1.8 mm, and the root mean square value of dynamic stress is 130 MPa.

[0058] S4: Additional Stress Synthesis and Fatigue Life Assessment The additional stress is taken as 130 MPa, which is combined with the static stress (maximum 150 MPa) to obtain a combined stress of up to 280 MPa.

[0059] The tubing material is P110 steel. Its SN curve, after being corrected by high temperature and high pressure, is calculated using Miner's linear cumulative damage law. The fatigue life is 8.7 years. It is recommended to optimize the centralizer spacing to 30m and adjust the production cycle to 8 years for tubing replacement.

[0060] Example 4: Quantitative evaluation of additional stress caused by flow-induced vibration in low-gas-production vertical well tubing Suitable for low-gas-production vertical wells (gas production 3×10 4 m 3 / d), the tubing string is a simple assembly (only tubing and basic casing, no packer, centralizer spacing 80m), the wellhead pressure is 8MPa, the wellhead temperature is 60℃, the fluid is mainly methane 98%, the flow-induced vibration is mainly turbulent buffeting, and the influence of vortex-induced vibration is relatively weak.

[0061] S1: Quantitative Calculation of Flow-Induced Vibration Excitation Load S1.1: Characteristic diameter of the tubing D = 60.3 mm, fluid velocity V = 6 m / s, St is taken as 0.19, and the calculated vortex shedding frequency fᵥ = 0.19 × 6 / 0.0603 ≈ 18.91 Hz.

[0062] S1.2: Using a simplified empirical model of vortex-induced vibration, the power spectral density of the vortex-induced force is determined to be 1×10⁻⁶. -3 N 2 / Hz.

[0063] S1.3: The Liepmann spectrum was selected as the empirical spectrum for turbulent buffeting. With an input turbulence intensity of 6%, the power spectral density of the turbulent pressure fluctuation was obtained as 1.5 × 10⁻⁶. -4 Pa 2 / Hz.

[0064] S2: Three-dimensional finite element model establishment and modal analysis Based on the vertical well trajectory (depth 1800m, vertical and without well deviation), a three-dimensional finite element model was established using HyperMesh. The tubing string was simulated using beam elements, and elastic support constraints (normal contact stiffness 5×10⁻⁶) were set at the centralizer.7 N / m, tangential friction coefficient 0.1).

[0065] Modal analysis revealed that the first five natural frequencies of the tubing in water were 10Hz, 19Hz, 32Hz, 45Hz, and 58Hz, with a damping ratio of 0.018.

[0066] S3: Vibration Response Calculation The power spectral density analysis method is adopted, focusing on the contribution of turbulent buffeting load, and the power spectral density of the two types of excitations is calculated by inputting S1.

[0067] The calculated maximum dynamic displacement root mean square value of each node of the tubing is 0.8 mm, and the maximum dynamic stress root mean square value is 45 MPa.

[0068] S4: Additional Stress Synthesis and Fatigue Life Assessment The additional stress is taken as 45 MPa, which is combined with the static stress (maximum 90 MPa) to obtain a combined stress of up to 135 MPa.

[0069] The tubing material is J55 steel. Based on its standard SN curve and using Miner's rule, the fatigue life is calculated to be 35 years, which far exceeds the 20-year design production cycle of the gas well. The risk of flow-induced vibration in the tubing is negligible.

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0071] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for quantitatively evaluating the additional stress caused by flow-induced vibration in a gas well tubing, characterized in that, Includes the following sequential steps: S1. Based on the actual production parameters of the gas well, quantitatively calculate and determine the flow-induced vibration excitation load acting on the tubing string. The excitation load includes at least a narrow-band random excitation generated by vortex-induced vibration and a broadband random excitation generated by turbulent buffeting. S2. Based on the actual well trajectory and tubing combination, a three-dimensional finite element model considering the nonlinearity of the contact between the tubing and the wellbore is established, and modal analysis is performed to obtain the dynamic characteristics of the tubing in water. S3. The flow-induced vibration excitation load quantitatively characterized in step S1 is applied to the three-dimensional finite element model established in step S2 as input conditions. The vibration response of the pipe column is calculated by dynamic analysis method to obtain the dynamic displacement and dynamic stress of each node of the pipe column. S4. Extract the dynamic stress calculated in step S3 as the additional stress of flow-induced vibration, and synthesize it with the static stress of the tubing. Based on the synthesized stress, evaluate the fatigue life of key parts of the tubing.

2. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 1, characterized in that, In step S1, the specific process of quantitatively calculating the flow-induced vibration excitation load includes: S1.

1. Based on the fluid velocity V and the characteristic diameter D of the tubing, the vortex shedding frequency f_v is calculated using the Strouhal number St. The formula is f_v = St V / D; S1.2 Determine the power spectral density of vortex-induced force using an empirical model of vortex-induced vibration; S1.

3. The power spectral density of turbulent pressure fluctuations is determined using the empirical spectrum model of turbulent buffeting.

3. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 2, characterized in that, The empirical spectrum model for turbulent buffeting is either the Liepmann spectrum or the Modified API Spectrum.

4. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 1, characterized in that, In step S1, the excitation load also includes acoustic resonance excitation; when the acoustic natural frequency of the gas column in the tubing is coupled with the vortex shedding frequency f_v, the acoustic resonance excitation needs to be quantitatively characterized.

5. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 1, characterized in that, In step S2, the three-dimensional finite element model uses three-dimensional beam elements to simulate the pipe column and precisely sets the contact pairs between the pipe column and the casing to simulate the constraint effect of the centralizer and packer on the pipe column.

6. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 1, characterized in that, In step S3, the kinetic analysis method is power spectral density analysis, which is used to calculate the root mean square value of the dynamic response of the tubing.

7. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 1, characterized in that, In step S3, the dynamic analysis method is transient dynamic analysis, which is used to calculate the time history curve of the dynamic response of the tubing.

8. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 1, characterized in that, In step S4, the fatigue life assessment uses Miner's linear cumulative damage rule and combines it with the SN curve of the tubular material for prediction.

9. The method for quantitatively evaluating the additional stress caused by flow-induced vibration of a gas well tubing according to claim 1, characterized in that, The gas well production parameters include gas production, wellhead pressure, wellhead temperature, fluid composition, and tubing assembly structure.

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