Method for evaluating adaptability of on-service oil and gas pipeline to transfer hydrogen

Abstract

The invention provides an evaluation method for hydrogen transportation of an active-service oil-gas pipeline, which considers the difference between a hydrogen transportation pipeline and the oil-gas pipeline and comprises feasibility evaluation for hydrogen transportation of the oil-gas pipeline and adaptability evaluation for hydrogen transportation of the oil-gas pipeline. The former is mainly used for evaluating whether the oil and gas pipeline has the capacity of changing and transporting hydrogen, and judging from pipe evaluation and structural strength evaluation based on material parameters, design parameters and defect conditions of the current state of the oil and gas pipeline; and on the basis of the feasibility evaluation of the hydrogen retransportation of the oil and gas pipeline, the hydrogen retransportation degree of the pipeline is judged from strength evaluation, flow evaluation, crack arrest toughness evaluation and service life evaluation. According to the method, the oil and gas pipeline which is stopped or planned to be stopped can be evaluated, and after it is confirmed that the oil and gas pipeline has recycling value, transformation is carried out for hydrogen conveying. According to the scheme, resources and cost can be remarkably saved, construction risks are reduced, the construction period is shortened, and the comprehensive utilization efficiency of a pipe network is improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline assessment technology, specifically to an assessment method for converting existing oil and gas pipelines to transport hydrogen. Background Technology

[0002] In large-scale hydrogen transportation, pipeline transport is a more efficient and safer method. Hydrogen pipeline transport methods include using existing natural gas pipelines for hydrogen blending, converting existing natural gas pipelines into dedicated hydrogen pipelines, or constructing new pure hydrogen pipelines. All these methods can support long-distance hydrogen transportation. Currently, domestic and international hydrogen pipeline construction mainly focuses on new projects. Approximately 6,000 kilometers of hydrogen pipelines have been built abroad, primarily for pure hydrogen transportation systems between chemical plants, but the cost of such construction is relatively high. How to rationally utilize existing natural gas pipelines for hydrogen transportation has become a hot topic in the industry. Considering the relatively limited hydrogen supply and low transmission pressure, many regions abroad have adopted the conversion of natural gas pipelines for hydrogen transportation as a feasible method. Related calculations show that the investment in building new hydrogen pipelines is typically more than twice that of converting existing pipelines.

[0003] Against the backdrop of the "dual carbon" goal, utilizing existing pipelines for hydrogen transportation not only achieves energy substitution but also efficiently utilizes existing assets, offering significant economic and environmental advantages. Some European and American countries and organizations have already identified converting natural gas pipelines for hydrogen transportation as a key development direction and have deployed related plans. It is worth noting that China has not yet issued national or industry standards regarding the conversion of in-service oil and gas pipelines for hydrogen transportation.

[0004] Therefore, it is necessary to establish targeted design and operation methods for pipeline hydrogen transfer systems based on engineering practice, and to develop a feasibility assessment system for pipeline hydrogen transfer from the dual perspectives of pipeline hydrogen transfer safety and external environmental safety to fill the gap in domestic oil and gas pipeline hydrogen transfer technology and guide subsequent engineering practices. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for evaluating the conversion of existing oil and gas pipelines to hydrogen transportation. This method includes a feasibility assessment and an adaptability assessment. The former determines whether a pipeline has the capability for conversion based on pipe material and structural strength assessments, while the latter assesses the degree of adaptability based on strength, flow rate, crack arrest toughness, and lifespan assessments. This method can reliably assess the feasibility and adaptability of existing pipelines for conversion.

[0006] To achieve the above objectives, the method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport, as described in this invention, includes the following steps:

[0007] 1) Obtain the pipeline design parameters and current pipe material performance data required for the feasibility assessment of converting oil and gas pipelines to hydrogen transportation, evaluate the pipe materials, and determine whether they are feasible for hydrogen transportation.

[0008] 2) Collect information on the actual types and dimensions of defects related to the conversion of oil and gas pipelines to hydrogen transportation, assess the structural strength of the pipelines, and determine whether they can be safely converted to hydrogen transportation.

[0009] 3) Construct a strength assessment calculation model, and determine the safe transmission pressure after the pipeline is converted to transport hydrogen by combining the pipeline's defect type, defect size information and design coefficients;

[0010] 4) Construct a flow assessment calculation model. Based on the safe transport pressure, the initially planned pipeline temperature, and other influencing factors, determine the optimal transport flow rate of the modified pipeline through a hydrogen hydraulic calculation model.

[0011] 5) Construct a crack arrest toughness assessment calculation model. Based on the pipeline's safe transport pressure, wall thickness, outer diameter, and other dimensional parameters, and combined with the crack arrest toughness model, assess whether the pipe's toughness is sufficient to prevent crack propagation.

[0012] 6) Construct a remaining life calculation model, calculate the fatigue life and corrosion life of the pipeline based on the safe transmission pressure, and determine the remaining service life of the pipeline after switching to hydrogen transmission.

[0013] Step 1) The pipe material evaluation includes:

[0014] Considering the differences between oil and gas and hydrogen, the evaluation from four aspects—conventional physical and chemical properties, brittle fracture control, crack arrest fracture, and impact toughness—must meet the requirements of ASME B31.12-2019 and CGA G-5.6—2005 (R2013) standards and specifications.

[0015] Step 2) The structural strength assessment shall be conducted based on corrosion defects, dents, cracks and weld defects, and shall meet the requirements of GB / T 36701-2018 and SY / T 6649-2018 standards.

[0016] Step 3) The strength assessment requires calculating the safe delivery pressure under corrosion defects, dents, cracks, and weld defects. Considering its conservatism, the minimum value among them is taken as the final safe delivery pressure.

[0017] The hydraulic calculation model for flow assessment described in step 4) is constructed in accordance with the T / CSPSTC 103-2022 standard specification for hydrogen pipeline engineering design.

[0018] The crack arrest toughness assessment model described in step 5) was constructed with reference to the ASME B31.12-2019 standard specification.

[0019] Step 6) describes two remaining life calculation models: a fatigue life calculation model and a corrosion life calculation model. The fatigue life calculation model is constructed based on fatigue tests in a hydrogen environment and AIP / ASME failure assessment charts, while the corrosion remaining life calculation model is constructed according to the TSG D7003-2010 standard.

[0020] The present invention has the following beneficial effects:

[0021] This invention provides an assessment method for converting existing oil and gas pipelines to hydrogen transport, fully considering the differences between oil and gas and hydrogen. The method first conducts a feasibility assessment of converting oil and gas pipelines to hydrogen transport, determining whether the pipeline is capable of doing so based on pipeline materials and structural strength. If feasible, an adaptability assessment is further conducted to determine the degree of adaptability for hydrogen transport; if the conditions for conversion are not met, the pipeline needs to be repaired or replaced, and a new assessment must be performed. This method can ensure the smooth conversion of existing oil and gas pipelines to hydrogen transport, effectively solving the problem of some domestic oil and gas pipelines facing obsolescence, promoting the efficient utilization of hydrogen energy, filling the technological gap in domestic oil and gas pipeline hydrogen transport, and providing guidance for subsequent engineering practices. Attached Figure Description

[0022] Figure 1 This is a flowchart of the feasibility assessment for converting oil and gas pipelines to transport hydrogen, as described in this invention embodiment.

[0023] Figure 2 This is a flowchart of the adaptability assessment for converting oil and gas pipelines to hydrogen transportation in an embodiment of the present invention; Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0025] The method for assessing the adaptability of existing pipelines for hydrogen conversion as described in this invention includes the following steps:

[0026] 1) Obtain the pipeline design parameters and current pipe material performance data required for the feasibility assessment of converting oil and gas pipelines to hydrogen transportation, evaluate the pipe materials, and determine whether they are feasible for hydrogen transportation.

[0027] 2) Collect information on the actual types and dimensions of defects related to the conversion of oil and gas pipelines to hydrogen transportation, assess the structural strength of the pipelines, and determine whether they can be safely converted to hydrogen transportation.

[0028] 3) Construct a strength assessment calculation model, and determine the safe transmission pressure after the pipeline is converted to transport hydrogen by combining the pipeline's defect type, defect size information and design coefficients;

[0029] 4) Construct a flow assessment calculation model. Based on the safe transport pressure, the initially planned pipeline temperature, and other influencing factors, determine the optimal transport flow rate of the modified pipeline through a hydrogen hydraulic calculation model.

[0030] 5) Construct a crack arrest toughness assessment calculation model. Based on the pipeline's safe transport pressure, wall thickness, outer diameter, and other dimensional parameters, and combined with the crack arrest toughness model, assess whether the pipe's toughness is sufficient to prevent crack propagation.

[0031] 6) Construct a remaining life calculation model, calculate the fatigue life and corrosion life of the pipeline based on the safe transmission pressure, and determine the remaining service life of the pipeline after switching to hydrogen transmission.

[0032] Example

[0033] In this embodiment, an oil pipeline is used as the object of evaluation to assess the feasibility and adaptability of converting an existing pipeline to transport hydrogen. The basic parameter information of the pipeline is shown in Table 1.

[0034] Table 1 Basic Parameter Information of Oil Pipelines

[0035] Parameter name numerical values Parameter name numerical values Parameter name numerical values Material grade X52 Pipe length 282km SMYS 450MPa Pipe diameter 426mm Design pressure 6.3MPa SUTS 630MPa Pipe wall thickness 7mm Design output 500*104t / a Year of completion 1988

[0036] Through experiments and testing, the evaluation parameters required for assessing the adaptability of existing oil and gas pipelines to hydrogen transportation were determined, as shown below.

[0037] Table 2. Information on defects in oil pipelines.

[0038] Defect types depth length width Corrosion defects 4mm 86mm 53mm dent 3.8mm 124mm 61mm crack 2.5mm 71mm 2mm weld defects 3mm 4.1mm 44mm

[0039] Based on the aforementioned oil pipeline information, the suitability assessment method for converting existing oil and gas pipelines to hydrogen transport is used to determine whether the oil pipeline has the capability for conversion and the extent of such conversion. First, a feasibility assessment for converting oil and gas pipelines to hydrogen transport is conducted, including pipe material assessment and structural strength assessment, such as... Figure 1 As shown.

[0040] Pipe Material Assessment

[0041] Based on the basic information of the oil pipeline and the current mechanical performance parameters of the pipeline material, the pipeline material was evaluated. Judging from the conventional physical and chemical properties, brittle fracture control, crack arrest fracture, and impact toughness of the pipe material, the oil pipeline is feasible for conversion to transport hydrogen.

[0042] Structural strength assessment

[0043] Structural strength assessment indicators include corrosion depth, dent depth, crack depth, and weld defect depth. If the pipeline parameters are within the assessment standard range, it indicates that the pipeline is structurally feasible for relocation. The relevant parameters for this oil pipeline are: corrosion defect depth 4mm, dent depth 3.8mm, crack depth 2.5mm, and weld defect depth 3mm. The defects are within the assessment range, indicating that the pipeline is structurally feasible for relocation.

[0044] In summary, in the first part of the assessment of whether the pipeline can be converted to transport hydrogen, the parameters of the oil pipeline meet the requirements of the pipe material assessment and structural strength assessment, indicating that the pipeline has the capability to be converted to transport hydrogen.

[0045] The feasibility assessment for pipeline-to-hydrogen conversion determines that the pipeline has the capability for conversion. The adaptability assessment for pipeline-to-hydrogen conversion aims to evaluate the extent of pipeline conversion, such as... Figure 2 As shown.

[0046] Strength assessment

[0047] Using the residual strength calculation model for corrosion defects, combined with design coefficients and hydrogen reduction coefficients, and based on the corrosion length of 86 mm and corrosion depth of 4 mm in the oil pipeline, the safe transport pressure P1 under corrosion defects is determined to be 7.1 MPa.

[0048] Using the residual strength calculation model for the depression combined with the design coefficient, based on the depression depth of 3.8 mm and the yield strength of 450 MPa in the oil pipeline, the safe transport pressure P2 under the depression is determined to be 2.74 MPa.

[0049] Using the crack failure assessment diagram, the fracture toughness of the pipe in a hydrogen environment was tested to determine the pipe material parameters, internal pressure, and yield strength under hydrogen conditions. It was determined whether the assessment point was within the area enclosed by the assessment curve and the coordinate axis. Based on the crack depth of 2.5 mm, crack length of 71 mm, and preset safe delivery pressure of 4.3 MPa in the oil pipeline, the assessment point was calculated to be within the area enclosed by the assessment curve and the coordinate axis. The safe delivery pressure P3 under the crack defect was determined to be 4.3 MPa.

[0050] Using a residual strength calculation model for weld defects combined with design coefficients, and based on the fracture toughness of the weld material under hydrogen conditions, the parameters of the pipeline weld material, the yield strength under internal pressure and hydrogen conditions were determined. A failure assessment diagram was then used to evaluate the safety of the weld defects. Based on the weld defect length of 4.1 mm, width of 44 mm, and depth of 3 mm in this oil pipeline, the safe transport pressure P4 under the weld defect was determined to be 5.96 MPa.

[0051] Based on the residual strength model, the safe transmission pressures P1 7.1 MPa, P2 2.74 MPa, P3 4.3 MPa, and P4 5.96 MPa under each defect type are calculated. Considering the long-term operation of the pipeline, the minimum of P1 to P4 is taken as the final safe transmission pressure for strength evaluation, which is 2.74 MPa.

[0052] Traffic assessment

[0053] Based on the safe transport pressure in the strength assessment, and the preliminary estimates of influencing factors such as pipeline temperature, combined with the hydrogen transport hydraulic calculation model, the optimal transport flow rate of the modified pipeline was determined to be 3452.7 m³ / h. 3 / h.

[0054] Crack arrest toughness assessment

[0055] Based on the safe transport pressure in the strength assessment, the minimum required crack arrest toughness value for the current pipeline is determined to be 2.05J using the crack arrest toughness calculation model. The actual crack arrest toughness value of the pipe is greater than 2.05J, which meets the requirements.

[0056] Life assessment

[0057] For fatigue life assessment, based on fatigue tests in a hydrogen environment and AIP / ASME failure assessment charts, the initial defects were detected, and the crack propagation rate was assessed from the crack propagation of the defect according to the relationship between the measured driving force and the fatigue crack propagation rate. Based on the crack defects of the oil pipeline and the basic information of the pipe material, the fatigue life under hydrogen transportation was determined to be 22 years.

[0058] For corrosion life assessment, based on the safe transport pressure in the strength assessment and the corrosion rate obtained through detection or other means, a pipeline remaining life prediction model is used to determine the remaining years after the oil and gas pipeline is converted to transport hydrogen. The remaining life prediction model calculates the remaining years after the pipeline is converted to transport hydrogen to be 16.4 years.

[0059] Considering the special characteristics of hydrogen, the minimum lifespan assessment value of 16.4 years is taken as the remaining lifespan of the pipeline relocation.

[0060] Based on the above assessment, the oil pipeline can be converted to transport hydrogen, with a safe transport pressure of 2.74 MPa and an optimal transport flow rate of 3452.7 m³ / h. 3 / h, the pipeline has a remaining life of 16.4 years.

[0061] The above are merely some embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. For those skilled in the art, any obvious modifications or alternatives within the scope of the disclosed technical content of the present invention should be considered part of the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope described in the claims.

Claims

1. A method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport, characterized in that, Includes the following steps: 1) To assess the feasibility of converting oil and gas pipelines to hydrogen transportation, the pipeline design parameters and current performance parameters of the pipelines are required for the pipeline material assessment to determine whether the pipeline material is feasible for conversion. 2) Obtain information on the actual types and sizes of pipeline defects required for the structural strength assessment of the feasibility assessment of converting oil and gas pipelines to hydrogen transportation, and evaluate whether the pipeline structure has the feasibility for conversion. 3) Based on the type of pipeline defect, combined with defect size information and design coefficients, construct a strength assessment safety pressure calculation model for each defect to determine the safe transmission pressure for pipeline conversion to hydrogen transport; 4) Establish a flow rate assessment calculation model. Based on the safe transport pressure in the intensity assessment and the preliminary determination of the magnitude of influencing factors such as pipeline temperature, and in conjunction with the hydrogen hydraulic calculation model, determine the optimal transport flow rate of the modified pipeline. 5) Establish a crack arrest toughness calculation model. Based on the safe delivery pressure in the strength assessment, the pipe wall thickness, pipe outer diameter and other dimensional parameters, and combined with the crack arrest toughness model, determine whether the toughness of the pipe is sufficient to prevent long-range crack propagation. 6) Establish a remaining life calculation model, and calculate the pipeline fatigue life and corrosion life based on the safe transmission pressure in the strength assessment to determine the remaining years after the oil and gas pipeline is rerouted.

2. The method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport according to claim 1, characterized in that, Pipe evaluation includes routine physical and chemical property evaluation, brittle fracture control evaluation, crack arrest fracture evaluation, and impact toughness evaluation.

3. The method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport according to claim 1, characterized in that, The types of defects assessed for structural strength include corrosion defects, dents, cracks, and weld defects, which must meet the requirements of GB / T 36701-2018 Guidelines for Repairing Defects in Buried Steel Pipelines and SY / T 6649-2018 Technical Specifications for Repairing Defects in Oil and Gas Pipelines.

4. The method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport according to claim 1, characterized in that, Strength assessment requires calculating the safe delivery pressure under corrosion defects, dents, cracks, and weld defects. Considering conservatism, the minimum value among these should be taken as the final safe delivery pressure.

5. The method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport according to claim 1, characterized in that, The hydraulic calculation model for flow assessment was constructed in accordance with the T / CSPSTC 103-2022 Hydrogen Pipeline Engineering Design Specification.

6. The method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport according to claim 1, characterized in that, The crack arrest toughness assessment model was constructed with reference to ASME B31.12-2019.

7. The method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport according to claim 1, characterized in that, The fatigue remaining life calculation model is constructed based on the AIP / ASME failure assessment chart and the relationship between the measured driving force and the fatigue crack propagation rate.

8. The method for evaluating the conversion of existing oil and gas pipelines to hydrogen transport according to claim 1, characterized in that, The fatigue life calculation model was constructed based on fatigue tests in a hydrogen environment and AIP / ASME failure assessment diagrams, while the corrosion remaining life calculation model was constructed in accordance with the TSG D7003-2010 standard.

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