A method for calculating the rebound of oil and gas pipelines after a pipe break

Abstract

This invention discloses a method for calculating the rebound of broken oil and gas pipelines. It relates to the field of oil and gas pipeline maintenance technology and aims to address the problem that complex geological environments and limited working space in pipeline replacement sites significantly increase the difficulty of pipe breaking operations and weld assembly, thus greatly increasing the risks during pipeline replacement and repair. The key technical solution involves the following steps: S1: Customize the pipeline trajectory line, pipe diameter, and material model information, and obtain information on soil constitutive model and pipeline burial depth; S2: Perform pipeline load analysis and calculate the magnitude and direction of the rebound displacement at the pipeline cut; S3: Establish a three-dimensional solid analysis model of the soil and a pipeline shell analysis model; S4: Solve for the boundary conditions of the external loads on the pipeline, and based on these boundary conditions, calculate the rebound displacement and direction of the pipeline, providing technical support and preventative control measures for pipeline replacement. This achieves the effect of providing technical support and preventative control measures for pipeline replacement.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline maintenance technology, and in particular to a method for calculating the rebound of broken oil and gas pipelines. Background Technology

[0002] Due to their inherent characteristics, long-distance oil and gas pipelines are characterized by their long length, wide geographical span, complex surrounding geology and environment, and varied and complex terrain. They are also subject to significant environmental and human-induced impacts. These characteristics lead to additional stress on the pipelines during construction and operation.

[0003] Additional stress on pipelines is often difficult to trace, difficult to predict, and has complex causes. This leads to significant hidden dangers and uncertainties in the safe operation of pipelines. The presence of additional stress on pipelines is not only one of the main causes of pipeline failure, but also has a significant impact on the pipeline replacement process. At best, it can cause the pipeline to shift or form a bevel after cutting. At worst, it can cause the pipeline to break apart during the cutting process, damage the cutting equipment, and endanger the personal safety of on-site operators.

[0004] The existing technical solutions mentioned above have the following drawbacks: Pipeline replacement and repair construction involves a variety of construction methods, including earthwork excavation, loading and unloading, replacement of media inside the pipeline, pipeline cutting, pipe segment prefabrication, pipeline welding and corrosion protection. The replacement site often has a complex geological environment and limited working space. When these factors are superimposed on the additional stress of the pipeline, the difficulty of pipe cutting and weld assembly is greatly increased, which greatly increases the risk in the pipeline replacement and repair process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the rebound of oil and gas pipelines after pipe breakage, which can predict the release deformation after pipe breakage, effectively guide the construction process of pipeline replacement, and avoid injury to personnel and equipment damage during pipe cutting.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for calculating the rebound of oil and gas pipelines after pipe breakage, the calculation steps of which are as follows:

[0008] S1: Review the pipeline installation details, customize the pipeline trajectory line, pipe diameter, and material model information, and review the surrounding soil conditions to obtain information on soil constitutive structure and pipeline burial depth.

[0009] S2: Stress measurements are used to obtain the circumferential stress at the pipe locations. Pipe load analysis is performed, and the magnitude and direction of the pipe cut-out springback displacement are calculated. This applies to the three concentrated forces on the pipe. and three torques Solve the problem and give the boundary conditions for the external loads on the pipeline:

[0010] A1: When a portion of the buried pipeline is excavated, the stress at the cutting end can be summarized into three concentrated forces. and three torques The combination of three forces Corresponding shear deformation force, Corresponding to tensile and compressive deformation forces, among the three concentrated moments Corresponding to bending deformation force, Corresponding torsional deformation force of the cross section;

[0011] S3: Based on pipeline soil parameters, trench structure parameters, and pipeline specifications, establish a three-dimensional solid analysis model of the soil and a pipeline shell analysis model.

[0012] B1: Three-dimensional solid modeling, the calculation and analysis formula based on displacement is as follows:

[0013]

[0014] in The stress component in the soil, For the displacement variation, where:

[0015]

[0016] and

[0017]

[0018] They represent the displacement variation. and Along and The derivative of the direction, This represents the stress component in the soil.

[0019]

[0020] For stress gradient,

[0021]

[0022] For displacement variation and stress The gradient of the product,

[0023] The stress-strain constitutive relation in soil can be expressed as the formula... ,in Let be the fourth-order tensor of the soil's elastic constant. For strain components;

[0024] B2: The shell analysis model follows the basic assumptions of thin shell theory, and its displacement interpolation function is as follows: Its stiffness matrix is ​​expressed by the formula The remaining parts are handled in accordance with the conventional finite element model method; among which... For displacement components, For unit shape functions, For the degrees of freedom of the integration nodes, The element stiffness matrix, and The unit gradient matrix, The integral of the node.

[0025] S4: By conducting on-site stress tests, the boundary conditions of the external loads on the pipeline are determined. Based on the boundary conditions of the external loads, the rebound displacement and rebound direction of the pipeline can be calculated through pipe-soil coupling modeling, providing technical support and preventive control measures for pipeline replacement.

[0026] Furthermore, the load analysis method in S2 includes two types: a straight pipe section load analysis method and a pipe section containing bends load analysis method.

[0027] Furthermore, the straight pipe section load analysis method uses A and O as the stress test interfaces for the straight pipe section, with section O as the tangent point. Stress tests are performed at four symmetrically distributed points on each section, with a distance L between any two sections. Therefore, the expression for the straight pipe section load can be obtained as follows:

[0028]

[0029]

[0030]

[0031]

[0032]

[0033] .

[0034] in These represent the stress values ​​at different measurement points. D is the pipe diameter, L is the distance between the two sections, and I is the moment of inertia of the pipe section. These represent the resultant forces along the cross sections in the x, y, and z directions, respectively. These represent the resultant moments of the cross sections along the x, y, and z directions, respectively.

[0035] Furthermore, the method for analyzing the load on a pipe section containing a bend uses point O as the tangent point and three cross-sections (A, B, and O) as the stress test points. Stress tests are performed at four symmetrically distributed points on each cross-section. This yields the expression for the load on the pipe section containing the bend:

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042] in , where represent the stress values ​​at different measurement points, D is the pipe diameter, L is the distance between the two sections, and I is the moment of inertia of the pipe section. These represent the resultant forces along the cross sections in the x, y, and z directions, respectively. These represent the resultant moments of the cross sections along the x, y, and z directions, respectively. For the bend angle, Let be the section moment in the y direction. To measure the maximum distance of the x-projection, The effective bending moment length is in the x-direction.

[0043] In summary, the beneficial technical effects of the present invention are as follows:

[0044] 1. The method for calculating the rebound of broken oil and gas pipelines can analyze pipeline load based on the results of on-site stress tests and, combined with the pipe-soil interaction model, calculate the rebound direction and rebound displacement after the pipeline breaks, thus effectively predicting pipeline rebound and providing technical support for pipeline replacement.

[0045] 2. The method for calculating the rebound of broken oil and gas pipelines, based on the pipeline rebound displacement calculation model of the pipe-soil interaction, can calculate the rebound displacement and rebound direction of the pipeline, thus achieving the effect of providing preventive and control measures for pipeline replacement. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the workflow of the present invention;

[0047] Figure 2 This is a schematic diagram of the stress state of the pipe cross-section according to the present invention;

[0048] Figure 3This is a schematic diagram showing the location of the stress measurement points on the outer wall of the pipe according to the present invention;

[0049] Figure 4 This is an exploded schematic diagram of the pipe bending moment of the present invention;

[0050] Figure 5 This is a schematic diagram showing the distribution of the internal bend points of the pipeline according to the present invention. Detailed Implementation

[0051] The method of the present invention will be further described in detail below with reference to the accompanying drawings.

[0052] See attached document Figure 1 A method for calculating the rebound of oil and gas pipelines after a pipe break, the calculation steps of which are as follows:

[0053] S1: Check the pipeline laying information, customize the pipeline trajectory line, pipe diameter, and material model information, check the surrounding soil conditions, obtain soil constitutive and pipeline burial depth information, and define the pipeline characteristics as: pipeline trajectory definition, pipe diameter, wall thickness, pipe material constitutive definition, whether excavation is required and whether cutting is required, and define the soil as: pipeline burial depth definition, soil constitutive definition and macroscopic constitutive equivalence.

[0054] S2: Stress measurements are used to obtain the circumferential stress at the pipe locations. Pipe load analysis is performed, and the magnitude and direction of the pipe cut-out springback displacement are calculated. This applies to the three concentrated forces on the pipe. and three torques The solution provides the boundary conditions for the external loads on the pipeline, applicable to pipelines with diameters ranging from 508mm to 1422mm, steel grades from X60 to X80, varying wall thicknesses, and straight or curved sections.

[0055] A1: When part of the buried pipeline is excavated, such as Figure 2 As shown, the in-situ stress at the cutting end can be summarized into three concentrated forces. and three torques The combination of three forces Corresponding shear deformation force, Corresponding to tensile and compressive deformation forces, among the three concentrated moments Corresponding to bending deformation force, Corresponding torsional deformation force of the cross section;

[0056] Load analysis methods include two types: load analysis methods for straight pipe sections and load analysis methods for pipe sections containing bends.

[0057] like Figure 3As shown, the method for analyzing the load on a straight pipe section involves taking the stress test interfaces A and O as the tangent point, section O as the tangent point, and performing stress tests at four symmetrically distributed points on each section, corresponding to points ①-⑧. The distance between two sections is L. Therefore, the expression for the load on the straight pipe section can be obtained as follows:

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064] in These represent the stress values ​​at different measurement points, where D is the pipe diameter, L is the distance between the two sections, and I is the moment of inertia of the pipe section. These represent the resultant forces along the cross sections in the x, y, and z directions, respectively. These represent the resultant moments of the cross section along the x, y, and z directions, respectively.

[0065] like Figures 4-5 As shown, the load analysis method for a pipe section containing a bend is as follows: the tangent point is point O, and the stress test points are located at three sections: A, B, and O. Stress tests are performed at four symmetrically distributed points on each section, with test points ①-⑫. Therefore, the expression for the load on the pipe section containing the bend can be obtained as follows:

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] in , where represent the stress values ​​at different measurement points, D is the pipe diameter, L is the distance between the two sections, and I is the moment of inertia of the pipe section. These represent the resultant forces along the cross sections in the x, y, and z directions, respectively. These represent the resultant moments of the cross sections along the x, y, and z directions, respectively. For the bend angle, The section moment in the y direction, To measure the maximum distance of the x-projection, The effective bending moment length in the x-direction;

[0073] S3: Based on pipeline soil parameters, trench structure parameters, and pipeline specifications, establish a three-dimensional solid analysis model of the soil and a pipeline shell analysis model.

[0074] B1: Three-dimensional solid modeling, the calculation and analysis formula based on displacement is as follows:

[0075]

[0076] in The stress component in the soil, For the displacement variation, where: and They represent the displacement variation. and Along and The derivative of the direction, The stress component in the soil, For stress gradient, For displacement variation and stress The gradient of the product can be expressed by the formula for the stress-strain constitutive relation in soil. ,in The elastic constant is a fourth-order tensor;

[0077] B2: The shell analysis model follows the basic assumptions of thin shell theory, and its displacement interpolation function is as follows: Its stiffness matrix is ​​expressed by the formula The remaining parts are handled in accordance with the conventional finite element model method, among which... For displacement components, For unit shape functions, For the degrees of freedom of the integration nodes, The element stiffness matrix, and The unit gradient matrix, The integral of a node;

[0078] S4: By conducting on-site stress tests, the boundary conditions of the external loads on the pipeline are determined. Based on the boundary conditions of the external loads, the rebound displacement and rebound direction of the pipeline can be calculated through pipe-soil coupling modeling, providing technical support and preventive control measures for pipeline replacement.

[0079] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for calculating springback of a severed pipe of an oil and gas pipeline, characterized by, The calculation steps are as follows: S1: Check the pipeline burying condition, customize the pipeline trajectory line, pipe diameter, material model information, and check the surrounding soil condition to obtain the soil constitutive, pipeline burying depth information; S2: Obtain the circumferential point stress of the pipeline by stress measurement method, analyze the pipeline load, and calculate the size and direction of the pipeline cutback springback displacement, solve the three concentrated forces and three moments of the pipeline, and give the boundary conditions of the external load on the pipeline: A1: When a section of buried pipeline is excavated, the in-situ stresses at the cut end are summarized as a combination of three concentrated forces and three moments The three concentrated forces correspond to shear deformation forces, tension-compression deformation forces, and the three concentrated moments correspond to bending deformation forces, and cross-sectional torsion deformation forces; S3: According to the pipeline soil parameters, trench structure parameters and pipeline specification pipeline burying factors, a soil three-dimensional entity analysis model and a pipeline shell analysis model are established; B1: Three-dimensional entity modeling, the calculation analysis formula based on displacement mode is ； where is the stress component in the soil, is the displacement variation, where: and denote the displacement variation and derivative along the and directions, is the stress component in the soil, is the gradient of stress , is the gradient of the displacement variation and stress product, which for the stress-strain constitutive relation in the soil can be expressed as the formula where is the elastic constant fourth-order tensor; B2: The shell analysis model complies with the basic assumption of thin shell theory, and the displacement shape function is constructed as follows: The stiffness matrix is expressed as formula The rest of the processing is consistent with the conventional finite element model, wherein is the displacement component, is the element shape function, is the integral node degree of freedom, is the element stiffness matrix, and is the element gradient matrix, is the node integral quantity; S4: Through field stress testing, the boundary conditions of the external load borne by the pipeline are solved, based on the boundary conditions of the external load, the pipeline rebound displacement and rebound direction are calculated through the pipe-soil coupling modeling, which provides technical support and preventive control measures for pipeline replacement.

2. A method of calculating springback for a pipeline girth weld according to claim 1, wherein: The load analysis method in S2 includes straight pipe section pipeline load analysis method and bend pipe section pipeline load analysis method.

3. The method of claim 2, wherein: The straight pipe section pipeline load analysis method is that the stress test interface of the straight pipe section pipeline is A and O, the tangent point is O section, four clock point stress tests are carried out on each section, the distance between two sections is L, and the expression of the straight pipe section pipeline load can be obtained as follows: ； ； ； ； ； ； wherein respectively represent the stress values of different measuring points; D is the pipe diameter, L is the distance between two sections, I is the pipe section inertia moment, respectively represent the section resultant forces along the x, y, z three directions, respectively represent the section resultant moments along the x, y, z three directions.

4. The method of claim 2, wherein: The bend pipe section pipeline load analysis method is that the tangent point is O point, the stress test point position section is A, B and O three sections, four clock point stress tests are carried out on each section, and the expression of the bend pipe section pipeline load can be obtained as follows: The bend pipe section pipeline load analysis method is that the tangent point is O point, the stress test point position section is A, B and O three sections, four clock point stress tests are carried out on each section, and the expression of the bend pipe section pipeline load can be obtained as follows: ； ； ； ； ； ； wherein , respectively, represent the stress values of different measuring points, D is the pipe diameter, L is the distance between two sections, I is the pipe section inertia moment, respectively, represent the section resultant forces along the x, y, z three directions, respectively, represent the section resultant moments along the x, y, z three directions; is the bend angle, is the y-direction section moment, is the maximum distance of the x projection, is the effective bending moment length in the x direction.

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