Oil string connecting thread sealing reliability digital intelligent analysis method and system and electronic equipment

Abstract

The invention relates to a tubing string connecting thread sealing reliability digital intelligent analysis method and system and electronic equipment. The method comprises the steps of establishing a finite element control equation based on a mechanical theory; constructing a three-dimensional simulation model and verifying the accuracy of the model; analyzing the influence of make-up torque, wear parameters (depth / opening) and borehole curvature on the thread performance; and evaluating the contact pressure change of the sealing surface and judging the sealing reliability. By means of the method and device, the technical problem that in the prior art, a quantitative analysis method for the three-dimensional mechanical behavior and sealing performance of the tubing string connecting thread under the complex working condition is lacked, and consequently the reliability of the tubing string connecting thread cannot be accurately evaluated is solved, and the technical effect that the reliability and safety of tubing string connecting sealing are remarkably improved is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wellbore engineering, and particularly relates to a method and system for analyzing sealing reliability of tubing string connection thread and an electronic device. BACKGROUND

[0002] With the rapid development of oil and gas exploration and development, wellbore engineering technology is the core technology. The engineering status of tubing string connection thread strength and sealing performance is extremely complex in mechanical properties. At present, high-angle directional wells and horizontal wells are relatively common, especially with the rapid development of shale gas development, horizontal well completion is more common, and gas storage injection and production wells are all high-angle directional wells. Natural gas flow in the tubing string induces tubing string vibration, which leads to longitudinal vibration stress concentration of the tubing string, mainly in the connection. At the same time, when radial vibration occurs, the tubing string and the tubing string collide and grind, which causes the tubing string and the tubing string to be in lateral contact, and the tubing string connection thread wear problem caused by the lateral contact force is increasingly prominent, which will increase the stress concentration of the tubing string and increase the safety risk of the tubing string. In recent years, many scholars have conducted a lot of research on the tubing string wear problem, but they are all focused on the non-connection part of the tubing string, and there is no research on the strength calculation of the connection area thread due to the collision and grinding of the tubing string and the three-dimensional mechanical behavior of the worn tubing string connection thread in injection and production wells. Specific problems include: the stress distribution and sealing performance of the tubing string connection thread under complex working conditions lack quantitative evaluation methods; the influence mechanism of the wear depth and the wear opening on the stress state of the thread is not clear; the influence law of the wellbore curvature on the thread sealing performance has not been systematically studied; and there is a lack of dynamic evaluation means for the thread sealing reliability combined with injection and production conditions. SUMMARY

[0003] The present application aims to at least solve the technical problems in the prior art, and provide a method and system for analyzing sealing reliability of tubing string connection thread and an electronic device.

[0004] In a first aspect, the present application provides a method for analyzing sealing reliability of tubing string connection thread, comprising: based on the virtual work principle, the yield criterion and the contact nonlinear theory, establishing a finite element control equation of the tubing string connection thread sealing, the finite element control equation is used to describe the complex stress state through the Cauchy stress tensor, the virtual strain, the virtual displacement and the unit surface force load vector; constructing a three-dimensional numerical simulation model according to the geometric parameters and material properties of the tubing string, and verifying the three-dimensional numerical simulation model; based on the verified three-dimensional numerical simulation model, using the finite element control equation to analyze the influence of the makeup characteristics on the stress distribution, the influence of the wear parameters on the mechanical properties of the thread and the influence of the wellbore curvature on the sealing performance; combining the analysis results, using the finite element control equation to dynamically solve the distribution and variation trend of the sealing surface contact pressure under the conditions of gas injection and gas production, and judging the reliability of the sealing performance of the tubing string connection thread.

[0005] Optionally, the finite element governing equation is constructed based on Cauchy stress tensor, virtual strain, virtual displacement and unit surface force load vector, and is specifically: ∫∫∫ V δ ij δζ ij dV=∫∫ A F i δμ i dA, wherein σ ij represents Cauchy stress tensor, δζ ij represents virtual strain, F i represents unit surface force load vector, δμ i represents virtual displacement, V represents volume in the present configuration, A represents surface area in the present configuration, and i, j represent matrix coordinates.

[0006] Optionally, a three-dimensional numerical simulation model is constructed according to geometric parameters and material properties of the tubing string, including: the three-dimensional numerical simulation model is constructed by three-dimensional solid modeling based on the geometric parameters of the tubing string, the material properties and the friction coefficient affected by the thread compound; wherein the geometric parameters of the tubing string include outer diameter, wall thickness and thread specification, and the material properties include elastic modulus, Poisson's ratio and yield strength.

[0007] Optionally, the influence of makeup characteristics on stress distribution is analyzed by using the finite element governing equation, including: the equivalent stress distribution of the tubing string connection thread under the action of the optimal makeup torque is simulated and analyzed by the finite element governing equation, and the stress concentration area and the corresponding maximum stress value are determined.

[0008] Optionally, when the wear parameter is wear depth, the influence of the wear parameter on the mechanical properties of the thread is analyzed by using the finite element governing equation, including: the mechanical properties of the tubing string connection thread under different wear depths are simulated and analyzed by the finite element governing equation, the influence law of the wear depth on the stress concentration degree and the average stress level of the thread is determined, and the maximum allowable wear depth is calculated.

[0009] Optionally, when the wear parameter is wear opening, the influence of the wear parameter on the mechanical properties of the thread is analyzed by using the finite element governing equation, including: the mechanical properties of the tubing string connection thread under different wear openings are simulated and analyzed by the finite element governing equation, the influence law of the wear opening on the stress distribution of the thread is determined, and the influence degree of the wear opening on the sealing performance of the thread is determined.

[0010] Optionally, the finite element control equation is used to analyze the influence of the wellbore curvature on the sealing performance, including: simulating and analyzing the mechanical properties of the worn tubing string connecting thread under different wellbore curvatures by the finite element control equation, determining the influence law of the wellbore curvature on the thread stress distribution, contact pressure distribution and sealing performance, and calculating the maximum allowable axial tensile load of the tubing string connecting thread under different wear degrees.

[0011] Optionally, the finite element control equation is used to dynamically solve the distribution and variation trend of the sealing surface contact pressure under the gas injection and gas production conditions, and judge the reliability of the sealing performance of the tubing string connecting thread, including: simulating and analyzing the contact pressure distribution and variation law on the sealing surface of the tubing string connecting thread under the gas injection and gas production conditions by the finite element control equation, determining the sealing performance variation trend under the gas injection and gas production conditions; based on the sealing performance variation trend under the gas injection and gas production conditions, evaluating the reliability of the sealing performance of the tubing string connecting thread under the gas injection and gas production conditions.

[0012] In a second aspect, the present application provides an oil tubing string connecting thread sealing reliability intelligent analysis system, including: a first processing module, configured to establish a finite element control equation of the oil tubing string connecting thread sealing based on the virtual work principle, the yield criterion and the contact nonlinear theory, the finite element control equation being used to describe a complex stress state through the Cauchy stress tensor, the virtual strain, the virtual displacement and the unit surface force load vector; a second processing module, configured to construct a three-dimensional numerical simulation model according to the geometric parameters and material properties of the oil tubing string, and verify the three-dimensional numerical simulation model; a third processing module, configured to analyze the influence of the makeup characteristics on the stress distribution, the influence of the wear parameters on the thread mechanical properties and the influence of the wellbore curvature on the sealing performance based on the verified three-dimensional numerical simulation model and the finite element control equation; and a fourth processing module, configured to combine the analysis results, dynamically solve the distribution and variation trend of the sealing surface contact pressure under the gas injection and gas production conditions by the finite element control equation, and judge the reliability of the sealing performance of the oil tubing string connecting thread.

[0013] In a third aspect, the present application provides an electronic device, including: at least one processor; and a memory communicatively connected with the at least one processor; wherein the memory stores a computer program which can be executed by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to execute the oil tubing string connecting thread sealing reliability intelligent analysis method described in the above.

[0014] In the embodiment of the present application, by establishing a three-dimensional mechanical model of the tubing string connecting thread and a quantitative analysis method, the influence of the wear depth, wear opening and wellbore curvature is accurately evaluated for the first time, thereby solving the technical problem that the prior art lacks a quantitative analysis method for the three-dimensional mechanical behavior and sealing performance of the tubing string connecting thread under complex working conditions, resulting in the inability to accurately evaluate its reliability, and achieving the technical effect of significantly improving the sealing reliability and safety of the tubing string connection. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a flowchart of a tubing string connecting thread sealing reliability numerical analysis method provided by the present application;

[0016] Figure 2(a) is a schematic diagram of a three-dimensional model of a tubing string connecting area provided by the present application;

[0017] Figure 2(b) is a schematic diagram of a tubing string and coupling unit analysis grid model provided by the present application;

[0018] Figure 3 is a schematic diagram of a simulation result and an experimental result provided by the present application;

[0019] Figure 4 is a schematic diagram of a tubing string connecting thread loading mode and stress provided by the present application;

[0020] Figure 5 is a schematic diagram of the Von Mises equivalent stress distribution of a tubing string connecting thread under the action of a makeup torque provided by the present application;

[0021] Figure 6 is a schematic diagram of a high-yield gas well downhole television logging situation provided by the present application;

[0022] Figure 7 is a schematic diagram of tubing string and tubing string joint eccentric wear of XCL1 well provided by the present application;

[0023] Figure 8 is a schematic diagram of the maximum Mises equivalent stress of the thread tooth at different wear depths provided by the present application;

[0024] Figure 9 is a schematic diagram of the maximum Mises equivalent stress of the thread tooth at different wear openings provided by the present application;

[0025] Figure 10 is a schematic diagram of the tubing string first tooth circumferential stress distribution at different wellbore curvatures provided by the present application;

[0026] Figure 11 is a schematic diagram of the tubing string first tooth circumferential contact pressure distribution at different wellbore curvatures provided by the present application;

[0027] Figure 12 It is a schematic diagram of the critical load-bearing of the connecting thread of the oil pipe string with different curved wellbores provided by the present invention;

[0028] Figure 13 This is a schematic diagram of the contact pressure distribution on the sealing surface during gas injection provided by the present invention;

[0029] Figure 14 This is a schematic diagram of the contact pressure distribution on the sealing surface during gas extraction provided by the present invention;

[0030] Figure 15 Schematic diagram of a digital intelligence analysis system for oil pipe string connection thread sealing reliability provided by the present invention;

[0031] Figure 16 It is a structural schematic diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0032] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0033] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0034] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal communication between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0035] The execution subject of the oil string connection thread sealing reliability intelligent analysis method includes but is not limited to at least one of electronic devices such as a server and a terminal that can be configured to execute the method provided by the embodiment of the present application. In other words, the oil string connection thread sealing reliability intelligent analysis method can be executed by software or hardware installed in a terminal device or a server device, and the software can be a blockchain platform. The server includes but is not limited to a single server, a server cluster, a cloud server, or a cloud server cluster, etc. The server can be a stand-alone server, or a cloud server providing cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDN), and basic cloud computing services such as big data and artificial intelligence platforms.

[0036] According to an aspect of an embodiment of the present application, an oil string connection thread sealing reliability intelligent analysis method is provided. Figure 1 is a flowchart of an oil string connection thread sealing reliability intelligent analysis method provided by the present application, as shown in Figure 1 The method includes the following steps:

[0037] Step S102, based on the virtual work principle, the yield criterion and the contact nonlinear theory, the finite element control equation of the oil string connection thread sealing is established. The finite element control equation is described by the Cauchy stress tensor, the virtual strain, the virtual displacement and the unit surface force load vector to describe the complex stress state; for example, based on the virtual work principle, the yield criterion and the contact nonlinear theory, the control equation describing the behavior of the oil string connection thread sealing is constructed, and the Cauchy stress tensor, the virtual strain and other parameters are introduced to accurately characterize the complex stress state.

[0038] Step S104, a three-dimensional numerical simulation model is constructed according to the geometric parameters and material properties of the oil string, and the three-dimensional numerical simulation model is verified; for example, according to the geometric parameters (such as outer diameter, wall thickness) and material properties (such as elastic modulus, yield strength) of the oil string, a high-precision model is established, and a hexahedral non-conforming element is used to refine the grid to ensure the calculation efficiency and accuracy. The three-dimensional numerical simulation model is verified by finite element numerical simulation, and the simulation results are compared with the actual experimental data; for example, the accuracy of the model is verified by comparing the simulation results with the actual experimental data (such as the change of the stress at the outer edge of the coupling).

[0039] In step S106, based on the verified three-dimensional numerical simulation model, the influence of makeup characteristics on stress distribution, the influence of wear parameters on thread mechanical characteristics, and the influence of wellbore curvature on sealing performance are analyzed by using finite element control equation; for example, stress distribution under the optimal makeup torque is simulated to identify the stress concentration area (such as the first effective thread root). The influence of wear depth on thread stress concentration and average stress is analyzed to calculate the maximum allowable wear depth (such as 4.3 mm for XCL-1 well). The influence of wear opening on stress distribution is analyzed to find that the maximum stress change is not more than 8%, which has a small influence. By using the additional bending stress formula and the contact stress model, the law that the increase of wellbore curvature leads to uneven stress distribution and the decline of sealing performance is revealed, and the critical load is calculated to guide the design.

[0040] In step S108, the distribution and variation trend of the sealing surface contact pressure under the conditions of gas injection and gas production are dynamically solved by using the finite element control equation combined with the analysis results to judge the reliability of the tubing string connection thread sealing performance; for example, the distribution and variation trend of the sealing surface contact pressure under the conditions of gas injection and gas production are analyzed to judge the sealing reliability.

[0041] In the embodiments of the present application, the three-dimensional mechanical model and quantitative analysis method of the tubing string connection thread are established, the influence of wear depth, wear opening, and wellbore curvature is accurately evaluated for the first time, thereby solving the technical problem that the prior art lacks a quantitative analysis method for the three-dimensional mechanical behavior and sealing performance of the tubing string connection thread under complex working conditions, which leads to the inability to accurately evaluate the reliability, and achieving the technical effect of significantly improving the sealing reliability and safety of the tubing string connection.

[0042] It should be noted that the three-dimensional numerical simulation model of the worn tubing string connection thread is established by using the virtual work principle, yield criterion, and contact nonlinear theory, and the influence of the makeup characteristics of the tubing string in the injection and production well and the wear depth, wear opening, and wellbore curvature on the tubing string connection thread under the cementing condition is analyzed. In addition, the wear and wellbore curvature have a great influence on the stress state of the tubing string connection thread, and some common working conditions can lead to the reduction of the connection performance and sealing performance of the tubing string thread. Considering the pressure fluctuation during the production of the injection and production, the influence of wear and wellbore curvature on the design and selection of the tubing string connection thread in the curved section of the high-deviation well should be considered.

[0043] The present application first proposes a quantitative analysis method for wear depth and wear opening, and determines that the maximum allowable wear depth of XCL-1 well is 4.3 mm, and the average stress increases by 99.5% when the wear depth increases by 1 time. The critical load criterion (such as the maximum allowable axial tensile load under different curvatures) is provided for the tubing string selection and wellbore trajectory design.

[0044] The present application discloses the significant influence of wellbore curvature on thread stress state (stress close to yield limit when 10° / 30m), which guides the targeted design of high-risk well section. Through dynamic analysis of injection-production conditions, the contact pressure change trend of sealing surface (maximum pressure decreases with cycle) is predicted to prevent sealing failure in advance.

[0045] As an optional embodiment, the finite element control equation is constructed based on Cauchy stress tensor, virtual strain, virtual displacement and unit surface force load vector, specifically: ∫∫∫ V σ ij δζ ij dV=∫∫ A F i δμ i dA, wherein σ ij represents Cauchy stress tensor, δζ ij represents virtual strain, F i represents unit surface force load vector, δμ i represents virtual displacement, V represents volume in present configuration, and A represents surface area in present configuration.

[0046] The tubing string running process is generally within the elastic range, and the mechanical analysis of tubing string connection thread under various complex conditions is a complex spatial elastic problem. According to the actual situation of the tubing string, the virtual work principle can be used to obtain the finite element control equation of the tubing string connection thread sealing. The parameters of the finite element control equation are described in detail below.

[0047] Further, σ ij is the Euler stress tensor (i.e. Cauchy stress tensor) which is a second-order symmetric tensor describing the stress state of a point inside the object after deformation (present configuration), directly reflecting the real stress distribution. Its components include normal stress and shear stress, satisfying the momentum conservation equation, and being suitable for large deformation problem analysis.

[0048] Mathematical representation:

[0049]

[0050] The strain after deformation is measured by strain gauges or optical methods (such as digital image correlation technology), and the stress is calculated by combining the constitutive equation (such as Hooke's law). The momentum conservation equation is solved in finite element analysis, and the boundary conditions are iteratively calculated.

[0051] Further, δζ ij is the virtual strain; the strain field corresponding to the virtual displacement is calculated by the virtual displacement gradient:

[0052]

[0053] Coupled with true stress in virtual work equation, used for energy conservation analysis.

[0054] Further, F i is the unit surface force load vector, N; the surface force per unit area (such as external force or contact force) in the current configuration. The boundary force data is obtained by pressure sensor or load sensor. Combined with the momentum conservation equation and stress tensor, it is applied as natural boundary condition in finite element model.

[0055] Further, δu i is the virtual displacement, m; the imaginary, small displacement field (denoted as δu) that satisfies the kinematic constraint conditions, used for virtual work principle analysis. The virtual work equation is constructed to derive the equilibrium condition and weak form governing equation. The displacement boundary conditions need to be satisfied, usually generated by mathematical construction or finite element interpolation function.

[0056] Further, V is the volume in the current configuration, m 3 ; V represents the spatial volume occupied by the deformed object, used for mass conservation and energy integration.

[0057] Further, A is the surface area in the current configuration, m 2 ; A represents the area of the object surface after deformation, used for boundary condition application and surface force integration. The Jacobian determinant J = det(F) is calculated by the deformation gradient tensor F, and the initial volume V0 is transformed into V = JV0. In finite element analysis, the element volume and area are calculated by node coordinate interpolation.

[0058] Further, i, j are matrix coordinates. The components of stress / strain tensor in different coordinate systems are represented. The principal stress and principal direction are obtained by solving the characteristic equation. The conversion between local coordinates and global coordinates is automatically handled in finite element software.

[0059] Considering the safety of the tubing string in the well, the elastic-plastic limit in numerical simulation uses the V yield criterion. When the equivalent stress σ is greater than or equal to the yield limit σ s of the material in uniaxial tension, it is considered as yield failure. Assuming that the entire force process is continuous and stable, the connecting thread of the tubing string is considered as an isotropic homogeneous body, and the constitutive equation of the elastic strain increment of the connecting thread is obtained by applying the generalized Hooke's law:

[0060]

[0061] where G is the shear modulus, Pa; the shear modulus represents the ability of the material to resist shear deformation, and is the linear proportional coefficient of stress and shear strain in the elastic stage. It is used to describe the relationship between deviatoric stress and deviatoric strain in the generalized Hooke's law. The elastic modulus E and Poisson's ratio v are measured by uniaxial tension test of the material, and G is calculated as:

[0062]

[0063] Further, S ij is the Kirchhoff stress tensor, Pa; the Kirchhoff stress tensor is a pseudo stress tensor in Lagrangian description, which is related to the Cauchy stress tensor σ by the deformation gradient F, formula:

[0064] S ij = J · σ

[0065] where J is the determinant of the deformation gradient (volume change rate). The Kirchhoff stress tensor is suitable for large deformation problems, and it is convenient to establish conservation equations in the reference configuration, especially in the finite element method for energy calculation. In numerical simulation, it is calculated by the deformation gradient tensor F and the Cauchy stress, which needs to be updated in real time.

[0066] Further, σ m is the hydrostatic pressure, Pa; the hydrostatic pressure represents the isotropic component of the stress tensor. It reflects the influence of volumetric deformation on the yield of the material, especially in rock or porous materials, the hydrostatic pressure significantly affects the yield behavior. It is calculated directly from the stress tensor and is an intermediate variable in simulation.

[0067] Further, K is the bulk modulus, Pa; the bulk modulus represents the ability of the material to resist uniform compression, and the relationship with the elastic modulus E and the Poisson's ratio v is:

[0068]

[0069] The bulk modulus is related to the hydrostatic pressure in the generalized Hooke's law. It is calculated after E and v are measured by material testing.

[0070] Further, δ ij is the Kronecker symbol. δ ij represents the component of the unit tensor, which satisfies:

[0071]

[0072] δ ij is used for tensor decomposition, for example, the stress tensor is decomposed into deviatoric stress and hydrostatic pressure: σ ij = S ij - pδ ij , where S ij is the deviatoric stress tensor.

[0073] As an optional embodiment, a three-dimensional numerical simulation model is constructed according to the geometric parameters and material properties of the tubing string, and the three-dimensional numerical simulation model is meshed, including: based on the geometric parameters, material properties and the friction coefficient affected by the thread grease of the tubing string, a three-dimensional numerical simulation model is constructed through three-dimensional entity modeling; wherein the geometric parameters of the tubing string include the outer diameter, the wall thickness and the thread specification, the material properties include the elastic modulus, the Poisson's ratio and the yield strength; hexahedral incoherent elements are used to divide the mesh, and the mesh of the threaded connection area is refined.

[0074] Optionally, a model is established taking a well of the gas storage as an example, and the tubing string of the well of the gas storage is taken as an example The thread is of VM80S tubing string steel grade, the elastic modulus is 2.1*10 5 MPa, the Poisson's ratio is 0.29, the yield strength is 758 MPa, the tensile strength is 862 MPa, the friction coefficient is generally 0.015-0.025, and the friction coefficient is 0.02 when the influence of the thread grease is considered. A three-dimensional numerical simulation model of the threaded connection of the tubing string is established through three-dimensional entity modeling.

[0075] In order to improve the calculation efficiency and accuracy, the model is simplified and assumed as follows:

[0076] ① The model is regarded as an isotropic homogeneous body;

[0077] ② The influence of plastic hardening is not considered;

[0078] ③ C3D8I hexahedral incoherent elements are used to divide the mesh of the model, and the mesh of the threaded connection part is refined.

[0079] Fig. 2(a) is a schematic diagram of a three-dimensional model of a tubing string connection area provided by the application, as shown in Fig. 2(a), the sealing structure in the model includes a sealing surface, a shoulder and a thread. The entire model is divided into 245600 meshes, including 116640 meshes of the tubing string and 128960 meshes of the coupling, and the mesh element division is shown in Fig. 2(b).

[0080] In order to ensure the reliability of the analysis results, the same specification of the tubing string threaded mechanical model is used by the application, and the stress variation law of the coupling outer edge under the actual working condition (axial tension 1200.96kN) is first studied through finite element numerical simulation. The simulation results and experimental results of the tubing string coupling outer edge stress variation are compared as shown in Fig. 3. Figure 3 As can be seen from Figure 3 , the numerical simulation results and the experimental results have basically the same trend, and the numerical difference is very small, which verifies that the model built by the application has high calculation accuracy.

[0081] As an optional embodiment, the finite element control equation is used to analyze the influence of makeup characteristics on stress distribution, including: the equivalent stress distribution of the tubing string connecting thread under the action of the optimal makeup torque is simulated and analyzed by the finite element control equation, and the stress concentration area and the corresponding maximum stress value are determined.

[0082] In order to ensure that the connection strength and sealing performance of the tubing string are reliable, safe and controllable under the actual production conditions in the well, the tubing string must be pre-tightened before being lowered. The equivalent loading and stress characteristics of the three-dimensional model of the tubing string connecting thread under the action of the composite load are as shown in Figure 4 Figure 4 In the formula, T is the torque, N·m; F is the axial tension, N; M is the bending moment, N·m; θ is the helix angle, (°); τ is the shear stress, Pa; σ is the normal stress, Pa; P is the combined stress of the shear stress and the normal stress, Pa; P x , P y are the stress components of the combined stress P along the x and y directions, Pa.

[0083] The Abaqus / Explicit explicit algorithm is used to simulate the makeup characteristics of the tubing string connecting thread according to the pre-set optimal makeup torque (9992 N·m). Figure 5 is a schematic diagram of the Von Mises equivalent stress distribution of the tubing string connecting thread under the action of the makeup torque provided by the application, as shown in Figure 5 The stress distribution of the tubing string connecting thread under the action of the makeup torque is very uneven, and the stress level at the first effective engagement thread tooth is much higher than that of other engagement thread teeth; the maximum Mises equivalent stress of the tubing string and the coupling all occurs at the first effective engagement thread tooth root, and the values are 41.11 MPa and 35.38 MPa, respectively.

[0084] As an optional embodiment, when the wear parameter is the wear depth, the finite element control equation is used to analyze the influence of the wear parameter on the mechanical characteristics of the thread, including: the mechanical characteristics of the tubing string connecting thread under different wear depths are simulated and analyzed by the finite element control equation, the influence law of the wear depth on the stress concentration degree and the average stress level of the thread is determined, and the maximum allowable wear depth is calculated.

[0085] Figure 6 is a schematic diagram of the downhole television logging situation of a high-yield gas well provided by the application, as shown in Figure 6 Among the field-recovered worn tubing strings, about 50% are crescent-shaped wear, and the crescent-shaped wear is the most serious. Therefore, the tubing string connecting thread of the XCL1 well with the crescent-shaped wear is analyzed in depth. In the injection and production process, the tubing string joint and the tubing string are eccentrically worn, and the actual wear condition is as shown in Figure 7 Figure 7 ​​In the formula, a is the outer diameter of the tubing string joint, mm; b is the outer diameter of the tubing string, mm; e is the eccentricity, mm; t is the wear depth, mm; h is the wall thickness of the tubing string, mm; and γ is the wear opening, (°).

[0086] After the tubing string is lowered into the well, the axial tensile load of the tubing string becomes larger and larger. According to the steel and steel friction test and the tubing string surface roughness Ra of 6.3-12.5, the friction coefficient is taken as 0.75 when the tubing string axial tensile load is calculated. Through calculation, the maximum borehole curvature of the build-up section of Xiangcun 1 well is 4.5° / 10m, and the numerical simulation model length is 500mm, so the equivalent calculation is made to obtain the bending displacement load Δy=0.35mm and the axial tensile load of 1250kN. The mechanical behavior analysis is made on the tubing string connection thread after the makeup, and the working stress characteristics are shown in Figure 8 Figure 8 The variation law of the maximum Mises equivalent stress of each effective engagement thread tooth with the wear depth is given. It can be seen from Figure 8 that the wear causes local stress concentration, and the peak stress is located at the first effective engagement thread tooth or the internal wear area; the maximum Mises equivalent stress when the wear is 4.3mm appears in the tubing string wear area, at this time, the maximum equivalent stress is almost equal to the yield limit of the material, and the maximum allowable wear depth of the tubing string connection thread of the build-up section of Xiangcun 1 well is about 4.3mm through calculation; the average stress level on the thread tooth increases rapidly with the increase of the wear depth; the average stress level when the wear is 4.3mm is increased by more than 99.5% compared with that when there is no wear, and is as high as 550MPa, which will greatly reduce the fatigue life of the tubing string connection thread. Therefore, the influence of the wear depth must be considered when the safety of the tubing string of Xiangcun 1 well is analyzed.

[0087] As an optional embodiment, when the wear parameter is the wear opening, the influence of the wear parameter on the mechanical characteristics of the thread is analyzed by using the finite element control equation, including: the mechanical characteristics of the tubing string connection thread under different wear openings are simulated and analyzed by using the finite element control equation, the influence law of the wear opening on the stress distribution of the thread is determined, and the influence degree of the wear opening on the sealing performance of the thread is determined.

[0088] The variation law formula of the maximum Mises equivalent stress with the wear opening is:

[0089] σ m =σ0+k·γ

[0090] wherein σ m is the maximum Mises equivalent stress; σ0 is the static stress value; γ is the wear opening; and k is the influence coefficient (the coefficient value is given according to the wear depth, the axial tensile load and the displacement load, and the range is 0.72-0.98).

[0091] ​Wear opening is the included angle between the two sides of the wear area and the center of the circle, denoted by symbol γ, as shown in Figure 7 The mechanical properties of the tubing string connection thread with a wear depth of 2mm are analyzed under the axial tensile load of 1250kN and the bending displacement load of Δy ≈ 0.3mm, and the calculation results are shown in Figure 9 . Figure 9 The variation of the maximum Mises equivalent stress of each effective thread tooth with the wear opening is given. Figure 9 It can be seen from the above table that the smaller the wear opening, the more obvious the stress concentration phenomenon, and the greater the maximum Mises stress; the Mises stress on the thread tooth at both ends increases with the decrease of the wear opening, and the Mises stress on the thread tooth in the middle decreases with the decrease of the wear opening; the maximum stress change caused by the wear opening does not exceed 8%, so the wear opening has little effect on the tubing string connection thread.

[0092] As an optional embodiment, the influence of the wellbore curvature on the sealing performance is analyzed by using the finite element control equation, including: the mechanical properties of the worn tubing string connection thread under different wellbore curvatures are simulated and analyzed by using the finite element control equation, the influence of the wellbore curvature on the stress distribution of the thread, the contact pressure distribution and the sealing performance is determined, and the maximum allowable axial tensile load of the tubing string connection thread under different wear degrees is calculated.

[0093] According to the wellbore structure of XCL1 well, the wear of the tubing string is theoretically analyzed, and the wear is most serious in the build-up section, the distortion is prominent, and the leakage risk is the highest. In order to understand the stress distribution rule of the worn tubing string connection thread in the build-up section, the mechanical properties of the worn tubing string connection thread under different wellbore curvatures are studied.

[0094] The wellbore curvature (K) directly affects the bending strain of the tubing string, and the additional bending stress caused by the wellbore curvature can be expressed as:

[0095]

[0096] Wherein, σ b is the bending stress; E is the elastic modulus of the pipe material; D is the outer diameter of the tubing string; K is the wellbore curvature.

[0097] The thread sealing performance is directly related to the contact stress. When the wear causes the gap between the sealing surfaces to increase, the contact stress σ c can be approximately expressed as:

[0098] σ c = (σ0+ σ b )·e -β·h

[0099] Wherein, σ0 is the initial contact stress; σ bis the bending stress; β is the attenuation coefficient (related to the sealing structure and material); h is the wear depth.

[0100] According to the situation of the oil tubing in the wellbore of Well No. 1, the maximum inclination rate of the wellbore is 5.11° / 30m. According to statistical data analysis, the average wear depth of Well No. 1 is about 2mm. Therefore, a tensile-bending composite load (tensile load of 1250kN, wellbore curvatures of 0° / 30m, 2° / 30m, 4° / 30m, 6° / 30m, 8° / 30m and 10° / 30m) was applied to the oil tubing connection thread that was worn 2mm after tightening. The mechanical characteristics were analyzed using finite element method. The results are as follows Figure 10 、 Figure 11 shown.

[0101] Figure 10 The variation law of the circumferential Mises equivalent stress of the first effective meshing thread of the oil pipe string with the wellbore curvature is given. Figure 10 As can be seen from the data, when the wellbore curvature is 0° / 30m, the circumferential Mises stress distribution of the first effective meshing thread is relatively uniform, with slight fluctuations caused by wear and helix angle. The wellbore curvature (bending load) causes tension on one side of the tubing string connection thread and compression on the other. As the wellbore curvature increases, the Mises stress gradually increases, and the strength of the tubing string thread connection gradually decreases. When the wellbore curvature reaches 10° / 30m, the maximum Mises stress approaches the yield strength. Although the axial load is greatly reduced after cementing, the larger wellbore curvature will significantly reduce the strength of the tubing string thread connection. The greater the wellbore curvature, the more severe the fluctuations in the circumferential Mises stress distribution of the thread teeth, with the tensile stress gradually increasing and the compressive stress gradually decreasing. The maximum Mises stress occurs near the mid-axis on the tensile side. The uneven circumferential stress distribution significantly reduces the tubing string's anti-collapse capability. Therefore, wellbore curvature has a significant impact on the stress state of the tubing string connection thread.

[0102] Figure 11 The variation law of the circumferential contact pressure of the first effective meshing thread of the oil pipe string with the wellbore curvature is given. Figure 11 It can be seen that as the wellbore curvature increases, the circumferential contact pressure distribution becomes more uneven. Excessive non-uniformity in the circumferential contact pressure may cause loss of thread sealing ability and caulking failure. The maximum contact pressure is located near the center axis of the tensile side. To avoid caulking failure, the maximum contact pressure should be controlled within the yield strength as much as possible. Figure 11 The corresponding minimum contact pressure is 122.5 MPa, which is much greater than the wellbore pressure in the deflection section. As long as the thread grease has good sealing properties, it will not cause the sealing failure of the oil pipe string connection thread.

[0103] Figure 12is a schematic diagram of critical load bearing of a worn tubing string connection thread in a different curved wellbore provided by the present application, Figure 12 The maximum allowable axial tensile load (referred to as critical load bearing) of the tubing string connection thread in the different curved wellbores is given when the wear depth is 0-4 mm. Figure 12 As can be seen from the table, the running depth of the tubing string below the build-up point can be calculated by the critical load bearing; the critical load bearing gradually decreases with the increase of the wellbore curvature, especially for the tubing string connection thread with 4 mm wear.

[0104] As an optional embodiment, the distribution and variation trend of the contact pressure on the sealing surface under the gas injection and gas production conditions are dynamically solved by using the finite element control equation to judge the reliability of the sealing performance of the tubing string connection thread, including: the distribution and variation law of the contact pressure on the sealing surface of the tubing string connection thread under the gas injection and gas production conditions are simulated and analyzed by using the finite element control equation to determine the variation trend of the sealing performance under the gas injection and gas production conditions; based on the variation trend of the sealing performance under the gas injection and gas production conditions, the reliability of the sealing performance of the tubing string connection thread under the gas injection and gas production conditions is evaluated.

[0105] Through the foregoing analysis of the tubing string connection region, the running condition of the entire tubing string is mastered, and in the case that the two tubing string connection threads are in contact, the surface thread sealing performance meets the running requirements.

[0106] During gas injection, the special thread joint at the most dangerous section of the tubing string is subjected to tensile load. The contact pressure distribution on the sealing surface of the thread joint during the gas injection process is as shown in Figure 13 .

[0107] During each cycle of gas injection, the contact pressure curve on the sealing surface of the thread joint along the contact surface presents an arch shape with the middle high and the two sides low. With the increase of the cycle, the top end of the curve presents a gradually downward trend, and the edge of the curve presents a gradually upward trend, that is, with the increase of the cycle, the maximum contact pressure on the sealing surface gradually decreases, and the contact pressure at the edge of the sealing surface gradually increases. This shows that during the gas injection process, the contact pressure on the sealing surface of the thread joint under the action of the tensile load is redistributed, and the maximum contact pressure on the sealing surface gradually decreases with the increase of the cycle.

[0108] During gas production, the special thread joint at the most dangerous section of the tubing string is subjected to compression load. The contact pressure distribution on the sealing surface of the thread joint during the gas production process is as shown in Figure 14 .

[0109] During the gas production of each cycle, the contact pressure curve on the sealing surface of the threaded joint presents an arch shape with high middle and low edges along the contact surface. With the increase of the cycle, the top of the curve presents a gradually downward trend, and the edge of the curve presents a gradually upward trend, that is, with the increase of the cycle, the maximum contact pressure on the sealing surface gradually decreases, and the contact pressure of the edge of the sealing surface gradually increases. Therefore, it is illustrated that, under the compression load during the gas production, the sealing surface of the three special threaded joints is deformed to become smoother, and the maximum contact pressure on the sealing surface gradually decreases with the increase of the cycle.

[0110] In summary, in the embodiments of the present application, quantitative calculation can be realized according to actual measurement. The wear depth has a great influence on the stress state of the tubing string connection thread. For XCL-1 well, the average stress level of the tubing string connection thread with 4.0 mm wear is 1 time higher than that without wear. Through numerical simulation, the maximum allowable wear depth of the bending section of XCL-1 well is calculated. The maximum stress change caused by the wear opening degree does not exceed 8%, and has a small influence on the stress state of the tubing string connection thread.

[0111] In addition, the present application can correct the composite of design and actuality, and provide a theoretical basis for standard revision. The wellbore curvature significantly increases the stress level of the tubing string connection thread, and has a great influence on the stress state. Through calculation, the maximum allowable axial tensile load (critical load bearing) of the tubing string connection thread with different wear degrees in different curvature wellbores is obtained. For a given design wellbore length, the critical load bearing can be used as a criterion for selecting the connection thread, and also can be used as one of the criteria for wellbore trajectory design.

[0112] The present application can provide a theoretical basis for wellbore integrity discrimination and production measure formulation. Considering the pressure fluctuation during production to middle and late production, the influence of wear and wellbore curvature on the sealing and safety of the tubing string connection thread of the bending section of XCL-1 well is considered, and through numerical analysis, the foreseeable wear of the tubing string is calculated in detail to ensure its safe work.

[0113] According to another aspect of the embodiments of the present application, there is provided a tubing string connection thread sealing reliability intelligent analysis system. Figure 15 It is a schematic diagram of the tubing string connection thread sealing reliability intelligent analysis system provided by the present application, as shown in Figure 15 The tubing string connection thread sealing reliability intelligent analysis system includes a first processing module 1502, a second processing module 1504, a third processing module 1506 and a fourth processing module 1508. The tubing string connection thread sealing reliability intelligent analysis system will be described in detail below.

[0114] The first processing module 1502 is configured to establish a finite element control equation of the tubing string connection thread seal based on a virtual work principle, a yield criterion and a contact nonlinear theory, and the finite element control equation is used to describe a complex stress state by using a Cauchy stress tensor, a virtual strain, a virtual displacement and a unit surface force load vector.

[0115] The second processing module 1504 is connected with the first processing module 1502 and is configured to construct a three-dimensional numerical simulation model according to geometric parameters and material properties of the tubing string, and verify the three-dimensional numerical simulation model.

[0116] The third processing module 1506 is connected with the second processing module 1504 and is configured to analyze, based on the verified three-dimensional numerical simulation model, influences of makeup characteristics on stress distribution, influences of wear parameters on thread mechanical characteristics and influences of a wellbore curvature on sealing performance by using the finite element control equation.

[0117] The fourth processing module 1508 is connected with the third processing module 1506 and is configured to dynamically solve, by using the finite element control equation, a distribution and a variation trend of a contact pressure of a sealing surface under gas injection and gas production conditions in combination with analysis results, and determine reliability of the tubing string connection thread seal.

[0118] It should be noted that the first processing module 1502, the second processing module 1504, the third processing module 1506 and the fourth processing module 1508 correspond to steps S102 to S108 in the method embodiment, and the modules and the corresponding steps have the same examples and application scenarios, but are not limited to the contents disclosed in the above method embodiment.

[0119] In the embodiment of the present application, the system establishes a three-dimensional mechanical model of the tubing string connection thread and a quantitative analysis method, and for the first time, accurately evaluates influences of the wear depth, the wear opening and the wellbore curvature, and further solves the technical problem that the prior art lacks a quantitative analysis method for three-dimensional mechanical behaviors and sealing performance of the tubing string connection thread under complex working conditions, and thus cannot accurately evaluate the reliability, and achieves the technical effect of significantly improving the sealing reliability and safety of the tubing string connection.

[0120] According to another aspect of the embodiment of the present application, an electronic device is provided, which includes at least one processor and a memory connected with the at least one processor in communication, and the memory stores a computer program that can be executed by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to execute the above-mentioned tubing string connection thread seal reliability numerical analysis method.

[0121] As Figure 16As shown is a structural schematic diagram of an electronic device of an oil string connection thread sealing reliability numerical analysis method provided by an embodiment of the application. The electronic device can include a processor 10, a memory 11, a communication bus 12, and a communication interface 13, and can further include a computer program stored in the memory 11 and executable on the processor 10, such as an oil string connection thread sealing reliability numerical analysis method program.

[0122] In some embodiments, the processor 10 can be composed of an integrated circuit, for example, a single packaged integrated circuit, or a plurality of packaged integrated circuits with the same function or different functions, including one or more combinations of a central processing unit (CPU), a microprocessor, a digital processing chip, a graphics processor, and various control chips. The processor 10 is the control unit of the electronic device, connects various components of the electronic device through various interfaces and lines, executes programs or modules stored in the memory 11 (such as executing an oil string connection thread sealing reliability numerical analysis method, etc.), and calls data stored in the memory 11 to perform various functions of the electronic device and process data.

[0123] The memory 11 includes at least one type of readable storage medium, including a flash memory, a mobile hard disk, a multimedia card, a card-type memory (such as an SD or DX memory, etc.), a magnetic memory, a magnetic disk, an optical disk, etc. In some embodiments, the memory 11 can be an internal storage unit of the electronic device, such as a mobile hard disk of the electronic device. In other embodiments, the memory 11 can also be an external storage device of the electronic device, such as a plug-in mobile hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the memory 11 can include both an internal storage unit and an external storage device of the electronic device. The memory 11 can be used not only to store application software and various data installed in the electronic device, such as the code of an oil string connection thread sealing reliability numerical analysis method program, but also to temporarily store data that has been output or will be output.

[0124] The communication bus 12 can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The bus is configured to enable connection and communication between the memory 11, the at least one processor 10, etc.

[0125] The communication interface 13 is configured to enable communication between the electronic device and other devices, including a network interface and a user interface. Optionally, the network interface can include a wired interface and / or a wireless interface (such as a WI-FI interface, a Bluetooth interface, etc.), and is typically configured to establish a communication connection between the electronic device and other electronic devices. The user interface can be a display, an input unit (such as a keyboard), and optionally, the user interface can also be a standard wired interface, a wireless interface. Optionally, in some embodiments, the display can be an LED display, a liquid crystal display, a touch liquid crystal display, an OLED (Organic Light-Emitting Diode) touch screen, etc. The display can also be appropriately referred to as a display screen or a display unit, and is configured to display information processed in the electronic device and to display a visualized user interface.

[0126] Figure 16 Only the electronic device with components is shown, and those skilled in the art can understand that, Figure 16 The structure shown does not constitute a limitation on the electronic device, and can include fewer or more components than shown, or combine certain components, or different component arrangements.

[0127] For example, although not shown, the electronic device can also include a power supply (such as a battery) for powering the various components. Preferably, the power supply can be logically connected to the at least one processor 10 through a power management device, so that the power management device can implement functions such as charge management, discharge management, and power consumption management. The power supply can also include one or more direct current or alternating current power supplies, recharging devices, power supply fault detection circuits, power supply converters or inverters, power supply status indicators, etc. The electronic device can also include various sensors, Bluetooth modules, Wi-Fi modules, etc., which are not described here.

[0128] It should be understood that the embodiments are for illustration only and do not limit the scope of the patent application.

[0129] Further, the modules / units integrated in the electronic device, if realized in the form of software function units and sold or used as independent products, can be stored in a computer readable storage medium. The computer readable storage medium can be volatile or non-volatile. For example, the computer readable medium can include any entity or device capable of carrying the computer program code, a recording medium, a U disk, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM).

[0130] The application further discloses a computer program product comprising computer programs / instructions, which, when executed by a processor, implement the steps of the oil pipe string connecting thread sealing reliability intelligent analysis method provided by the application. The computer program product should be understood as a software product mainly realizing the solution of the application, such as a program product integrated in the cloud or a software library.

[0131] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", "an implementation", "a preferred implementation" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0132] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A digital intelligence analysis method for the reliability of oil pipe connection thread seal, characterized by: include: Based on the principle of virtual work, yield criterion and contact nonlinear theory, a finite element governing equation for threaded sealing of tubing string connections is established. The finite element governing equation describes the complex stress state using the Cauchy stress tensor, virtual strain, virtual displacement and unit surface force load vector. Constructing a three-dimensional numerical simulation model based on geometric parameters and material properties of the oil tubing string, and verifying the three-dimensional numerical simulation model; Based on the verified three-dimensional numerical simulation model, the finite element control equation is used to analyze the influence of make-up characteristics on stress distribution, the influence of wear parameters on thread mechanical properties, and the influence of wellbore curvature on sealing performance; Combined with the analysis results, the finite element control equation is used to dynamically solve the distribution and change trend of the sealing surface contact pressure under gas injection and gas production conditions to determine the reliability of the sealing performance of the oil pipe string connection thread.

2. The method according to claim 1, characterized in that The finite element governing equation is constructed based on the Cauchy stress tensor, virtual strain, virtual displacement and unit surface force load vector, specifically: Among them, σ ij represents the Cauchy stress tensor, δζ ij represents virtual strain, F i represents the unit surface force load vector, δμ i Represents virtual displacement, V represents the volume in the current configuration, A represents the surface area in the current configuration, and i, j represent matrix coordinates.

3. The method according to claim 1, characterized in that A 3D numerical simulation model is constructed based on the geometric parameters and material properties of the tubing string, including: The three-dimensional numerical simulation model is obtained by constructing a three-dimensional solid model based on the geometric parameters of the tubing string, the material properties, and the friction coefficient affected by the thread compound; wherein the geometric parameters of the tubing string include outer diameter, wall thickness, and thread specification, and the material properties include elastic modulus, Poisson's ratio, and yield strength.

4. The method according to claim 1, wherein The finite element governing equation is used to analyze the effect of make-up characteristics on stress distribution, including: The equivalent stress distribution of the tubing string connection thread under the action of the optimal make-up torque is analyzed by finite element control equation simulation to determine the stress concentration area and its corresponding maximum stress value.

5. The method according to claim 1, wherein When the wear parameter is the wear depth, the influence of the wear parameter on the mechanical properties of the thread is analyzed using the finite element control equation, including: The mechanical properties of the tubing string connection threads at different wear depths are simulated and analyzed using the finite element control equation to determine the influence of the wear depth on the stress concentration degree and average stress level of the threads, and to calculate the maximum allowable wear depth.

6. The method according to claim 1, characterized in that When the wear parameter is the wear opening, the influence of the wear parameter on the mechanical properties of the thread is analyzed using the finite element control equation, including: The mechanical properties of the oil pipe string connection thread under different wear openings are simulated and analyzed by the finite element control equation to determine the influence of the wear opening on the thread stress distribution and the degree of influence of the wear opening on the thread sealing performance.

7. The method according to claim 1, characterized in that The finite element governing equation is used to analyze the effect of wellbore curvature on sealing performance, including: The mechanical properties of the worn tubing string connection threads under different wellbore curvatures are simulated and analyzed by the finite element control equation, the influence of wellbore curvature on thread stress distribution, contact pressure distribution and sealing performance is determined, and the maximum allowable axial tensile load of the tubing string connection threads under different wear degrees is calculated.

8. The method according to any one of claims 1 to 7, characterized in that The finite element control equation is used to dynamically solve the distribution and change trend of the sealing surface contact pressure under gas injection and gas production conditions to determine the reliability of the sealing performance of the tubing string connection thread, including: The contact pressure distribution and variation pattern on the sealing surface of the threaded connection of the tubing string under gas injection and gas production conditions are analyzed by simulating the finite element control equation to determine the variation trend of the sealing performance under gas injection and gas production; Based on the sealing performance change trend under gas injection and gas production conditions, the reliability of the sealing performance of the oil pipe string connection threads under gas injection and gas production conditions is evaluated.

9. A digital intelligence analysis system for the reliability of oil pipe connection thread seal, characterized in that: include: The first processing module is used to establish a finite element control equation for the thread seal of the oil pipe connection based on the principle of virtual work, yield criterion and contact nonlinear theory. The finite element control equation describes the complex stress state through the Cauchy stress tensor, virtual strain, virtual displacement and unit surface force load vector; A second processing module is used to construct a three-dimensional numerical simulation model based on the geometric parameters and material properties of the oil tubing string, and verify the three-dimensional numerical simulation model; A third processing module is used to analyze the influence of make-up characteristics on stress distribution, the influence of wear parameters on thread mechanical properties, and the influence of wellbore curvature on sealing performance using the finite element control equation based on the verified three-dimensional numerical simulation model; The fourth processing module is used to combine the analysis results and use the finite element control equation to dynamically solve the distribution and change trend of the sealing surface contact pressure under gas injection and gas production conditions to determine the reliability of the sealing performance of the oil pipe string connection thread.

10. An electronic device, characterized in that: The electronic device comprises: at least one processor; and, A memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to execute the method for numerically analyzing the reliability of threaded sealing of oil pipe string connections as described in any one of claims 1 to 8.

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