Quantitative evaluation method for offset protection effectiveness of submarine pipeline

Abstract

The invention relates to the technical field of ocean engineering, and provides a submarine pipeline offset protection effectiveness quantitative evaluation method. Comprising the steps that the maximum effective displacement UO and the maximum effective stress SO after the pipeline deviates are obtained, the effective displacement UR and the effective stress SR of the pipeline after prevention and treatment are obtained, and treatment effect indexes are calculated through the four parameters; the treatment effect indexes comprise a displacement treatment effect index DU and a stress treatment effect index DS, and the larger the treatment effect index value is, the better the treatment effect is; the method is simple and easy to use, and facilitates screening and evaluation of governance schemes.

Description

Technical Field

[0001] The present invention relates to the technical field of marine engineering and provides a method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection. Background Art

[0002] Submarine pipelines are sealed pipes that continuously transport large quantities of oil (gas) on the seabed. They are a major component of offshore oil (gas) field development and production systems and are the fastest, safest, most economical and reliable means of offshore oil and gas transportation. As the lifeline of offshore oil fields, they undertake important tasks such as the gathering, transportation, storage and transportation of offshore oil, gas and water. Their structural safety affects the stable operation of the production system.

[0003] The advantage of submarine pipelines is that they enable continuous oil transportation, virtually unaffected by environmental conditions. They prevent oilfield production cuts or shutdowns due to capacity limitations at offshore storage facilities or delayed shuttle tanker pickups. This results in high oil transportation efficiency and a large capacity. Furthermore, submarine pipelines shorten construction times, enable rapid commissioning, are easy to manage, and have low operating costs.

[0004] Disadvantages include: pipelines located on the seabed, and most need to be buried at a certain depth, making inspection and maintenance difficult. Pipe sections (especially risers) located in tidal zones or wave-breaking zones are significantly affected by wind, waves, currents, and ice, and can sometimes be damaged by floating debris, ship impacts, or anchorage. Long-term erosion by waves and currents can easily expose these sections, leading to long, exposed sections. These sections, under the continuous influence of waves and currents, can experience significant lateral deflection, up to tens of meters, leading to a sharp increase in stress and strain in the pipeline structure, a reduction in load-bearing capacity, and even potential pipeline ruptures.

[0005] Certain preventive measures must be taken for large-scale deviation sections of submarine pipelines to avoid further deviations. However, the industry is more concerned about how to implement the treatment of deviated pipelines, and has little confidence in the effectiveness of the selected treatment measures. There is an extreme lack of scientific and reasonable quantitative evaluation methods for the effectiveness of treatment measures to quantitatively evaluate and select more effective preventive measures. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the existing technology and to propose a quantitative evaluation method for the effectiveness of submarine pipeline deviation protection.

[0007] Solve the technical problems of how to quantitatively evaluate the effectiveness of submarine pipeline deviation prevention measures and obtain effective prevention measures through scientific screening, evaluate the effectiveness of submarine pipeline deviation prevention measures and meet the needs of protection measures screening projects.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A quantitative evaluation method for the effectiveness of submarine pipeline deviation protection includes obtaining the maximum effective displacement U after pipeline deviation. O and the maximum effective stress S O , obtain the effective displacement U of the pipeline after prevention and control R and effective stress S R , the treatment effect index is calculated by the above four parameters; the treatment effect index includes the displacement treatment effect index D U and stress management effect index D S The larger the value of the governance effect index is, the better the governance effect is.

[0010] Furthermore, the displacement management effect index DU = (UO-UR) / UO*100%.

[0011] Furthermore, the stress management effect index DS = (SO - SR) / SO * 100%.

[0012] Furthermore, the maximum effective displacement UO and the maximum effective stress SO of the pipeline after deflection are obtained by the following steps:

[0013] Obtain the actual route, pipeline parameters, soil parameters, and wave and current load data of the submarine pipeline before it is offset;

[0014] Establish a submarine pipeline model controlled by soil spring constraint load;

[0015] Assign pipe diameter, material, and wall thickness attributes;

[0016] Calculate soil spring stiffness and set soil spring constraints based on pipeline burial status and soil type according to ASCE guidelines;

[0017] Added the maximum wave and current depth, current and wave parameters in the transverse direction of the pipeline;

[0018] Apply the maximum wave and current in the transverse direction of the pipeline as loads through the subroutine;

[0019] By analyzing the influence of different lengths on the results, the constraint lengths on both sides of the submarine pipeline offset section are selected. The constraint lengths are continuously increased until a sufficient length is selected to ensure that the calculated displacement results change very little.

[0020] Calculate the maximum effective displacement U after pipeline offset O and the maximum effective stress S O .

[0021] Furthermore, the effective displacement U of the pipeline after the prevention and control R and effective stress S R Obtain it through the following steps:

[0022] Based on the soil spring constraint load control submarine pipeline model, the displacement prevention method is incorporated into the model as a constraint, and the effective displacement U of the pipeline after prevention is calculated. R and effective stress S R .

[0023] Furthermore, it also includes the displacement management economic index ED U , used to illustrate the displacement treatment effect and economy of the scheme.

[0024] Furthermore, the displacement management economic index ED U The larger the index value is, the better the displacement control effect and the superior economic efficiency of the scheme are.

[0025] Furthermore, the displacement management economic index ED U Calculated by the following formula:

[0026] ED U =D U / (B A / B T ).

[0027] Furthermore, it also includes stress management economic index ED S , used to illustrate the stress control effect and economy of the scheme.

[0028] Furthermore, the stress management economic index ED S Calculated by the following formula:

[0029] ED S =D S / (B A / B T ).

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) The quantitative evaluation method for protection effectiveness described in the present invention provides a clear and easy-to-use evaluation method for the protection engineering needs of submarine offset pipelines, filling the relevant technical gap in this technical field.

[0032] (2) The quantitative evaluation method for protection effectiveness described in the present invention provides a standard approach for screening prevention methods and predicting prevention effects for submarine offset pipelines in the field of this technology, which facilitates personnel in this field to first screen and evaluate and then implement prevention to ensure prevention effects.

[0033] (3) The quantitative evaluation method for the effectiveness of submarine pipeline deviation protection described in the present invention proposes a submarine pipeline model controlled by soil spring constraint load that can be used to analyze the structural stress and strain conditions of submarine pipelines before and after prevention and control, providing a submarine pipeline modeling and analysis method for personnel in this technical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the quantitative evaluation method for submarine pipeline deviation protection effectiveness of the present invention;

[0035] Figure 2 Schematic diagram of the soil spring constraint load control model of the present invention;

[0036] Figure 3 This is a schematic diagram of an example of incorporating preventive measures into the soil spring constraint load control model of the present invention. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0038] Example 1:

[0039] A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection includes the following steps:

[0040] 1) Based on the actual route of the submarine pipeline before displacement, pipeline parameters, soil parameters, and wave and current loads, a soil spring constraint load control submarine pipeline model is established, and the model reliability is verified;

[0041] 2) Calculate the maximum effective displacement UO and maximum effective stress SO of the pipeline after displacement based on the soil spring constraint load control submarine pipeline model established in step 1);

[0042] 3) Based on the soil spring constraint load control submarine pipeline model established in step 1), the displacement prevention method is incorporated into the model as a constraint to calculate the effective displacement UR and effective stress SR of the pipeline after prevention;

[0043] 4) The maximum effective displacement UO of the submarine pipeline before prevention and control obtained in 2) and the effective displacement UR after prevention and control obtained in 3) are used to calculate the displacement control effect index DU. The larger the index value, the better the effect of preventing and controlling the displacement increase caused by pipeline deviation.

[0044] 5) The maximum effective stress SO of the submarine pipeline before prevention and control obtained in 2) and the effective displacement SR after prevention and control obtained in 3) are used to calculate the stress control effect index DS. The larger the index value, the better the effect of preventing the stress increase caused by pipeline deviation.

[0045] 6) Introducing the planned total budget for governance, BT, and the corresponding implementation amount, BA, of a governance plan, the displacement governance effect index, DU, calculated in 4) is divided by BA / BT to calculate the displacement governance economic index, EDU. The larger the index value, the better the displacement governance effect and the superior economic efficiency of the scheme.

[0046] 7) The stress control effect index DS calculated in 5) is divided by BA / BT to calculate the stress control economic index EDS. The larger the index value, the better the stress control effect and the superior economic efficiency of the scheme.

[0047] 8) Comprehensively evaluate the treatment effect by taking into account the displacement treatment effect index DU, the stress treatment effect index DS, the displacement treatment effect economic index EDU and the stress treatment effect economic index EDS.

[0048] Example 2:

[0049] like Figure 1 As shown, the present invention provides a method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection, which is characterized by comprising the following steps:

[0050] 1) Finite element software is used to establish a soil spring constraint load control submarine pipeline model based on the actual route of the submarine pipeline before displacement, pipeline parameters, soil parameters, and wave and current loads (such as Figure 2 ), assigning pipe diameter, material, and wall thickness attributes, calculating soil spring stiffness and setting soil spring constraints based on the ASCE guideline method according to the pipeline burial state and soil type, adding the maximum wave and current depth, current, and wave parameters in the transverse direction of the pipeline, applying the maximum wave and current in the transverse direction of the pipeline as loads through a subroutine, and applying the same current and wave analysis results using a simplified straight-line route simply-supported pipeline model. The results are compared with the theoretical calculation results of the Morrison equation and verified to be reliable, indicating that the soil spring constraint load control of the submarine pipeline model using the same loading method is also reliable. By analyzing the degree of influence of different lengths on the results, the constraint lengths on both sides of the submarine pipeline offset section are determined, and the constraint lengths are continuously increased until a sufficient length is selected to ensure that the calculated displacement results change very little.

[0051] 2) Based on the soil spring constraint load control submarine pipeline model established in step 1), the maximum effective displacement U after the pipeline is offset is calculated. O and the maximum effective stress S O ;

[0052] 3) Based on the soil spring constraint load control submarine pipeline model established in step 1), the displacement prevention method is incorporated into the model as a constraint, and the effective displacement U of the pipeline after prevention is calculated. R and effective stress S R ,For example Figure 3 A three-point sand throwing prevention measure is simplified into a model with constraints incorporated;

[0053] 4) The maximum effective displacement U of the submarine pipeline before prevention and control obtained in 2) is O and 3) the effective displacement U obtained after prevention R Calculate the displacement treatment effect index D based on formula (1)U , the larger the index value is, the better the effect of preventing and controlling the displacement increase caused by pipeline deviation is;

[0054] D U =(U O -U R ) / U O *100% (1)

[0055] 5) Using the maximum effective displacement S of the submarine pipeline before prevention and control obtained in 2) O and 3) the effective displacement S after prevention and control R Calculate the stress control effect index D based on formula (2) S , the larger the index value is, the better the effect of preventing and controlling the stress increase caused by pipeline deviation is;

[0056] D S =(S O -S R ) / S O *100% (2)

[0057] 6) Introduce the total budget of planned governance B T And the implementation amount B corresponding to a certain governance plan A , using the displacement treatment effect index D calculated in 4) U and B A / B T Calculate the displacement management economic index ED based on formula (3) U ,The larger the index value is, the better the displacement control effect and the superior economic efficiency of the scheme;

[0058] ED U =D U / (B A / B T ) (3)

[0059] 7) Using the stress control effect index D calculated in 5) S and B A / B T Calculate the stress management economic index ED based on formula (4) S ,The larger the index value is, the better the stress control effect of the scheme is and the superior economic efficiency is;

[0060] ED S =D S / (B A / B T ) (4)

[0061] 8) Comprehensive displacement control effect index D U , stress control effect index D S , Economic index of displacement treatment effect EDU and stress control effect economic index ED S , the evaluation conclusion of the treatment effect is given according to the following Table 1. In the table, the first treatment effect is the best, the 2nd to 4th treatment effects are good but the economic efficiency is slightly worse, the 5th to 11th treatment effects are poor, and the 12th treatment effect is the worst.

[0062] Table 1 Comprehensive management effect evaluation table

[0063]

[0064]

[0065] The following uses a certain oil pipeline as an example to illustrate the specific steps of the method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to the present invention:

[0066] (1) Finite element software was used to establish a soil spring constraint load control submarine pipeline model based on the actual route, pipeline parameters, soil parameters, and wave and current loads before the submarine pipeline was offset, and the model reliability was verified. The exposed section of the oil pipeline is 120m long, the pipeline diameter is 273mm, the wall thickness is 11mm, and the material is X56 pipe with an elastic modulus of 210GPa, a Poisson's ratio of 0.3, a yield strength of 418MPa, and a tensile strength of 515MPa. According to the soil type and burial depth, the ASCE guide method was used to calculate the maximum soil resistance and corresponding displacement on both sides of the offset section. The lateral resistance on one side is 3982.3N / m, corresponding to a maximum displacement of 0.011m, and the axial resistance is 802N / m, corresponding to a maximum displacement of 0.003m. The lateral resistance on the other side is 15860N / m, corresponding to a maximum displacement of 0.023m, and the axial resistance is 2570N / m, corresponding to a maximum displacement of 0.003m. ; Wave and current loads in the direction of maximum deformation are applied through commands and subroutines. The water depth is 9.1m, the wave height is 4.98m, the surface velocity is 1.16m / s, the middle velocity is 1.09m / s, and the bottom velocity is 1.0m / s. The calculation results of the simplified straight line route simply supported submarine pipeline model applied with the same current and wave are compared with the results calculated by the Morrison equation theory, which is reliable. This means that the soil spring constraint load controlling the submarine pipeline model with the same loading method is also reliable; the constraint length on both sides of the submarine pipeline offset section is determined by analyzing the influence of different lengths on the results. The result of the calculation with increasing the constraint length to more than 250m shows very little change and tends to be stable. Therefore, the length of the constraint soil spring length section on both sides is 250m. Based on the actual route, pipeline parameters, soil parameters, and wave and current loads, a pipeline model with an overall length of 620 m was established. The exposed section in the middle was 120 m long, and the soil spring constraint sections on both sides were 250 m long each. The water depth was 9.1 m. The applied loads were a wave height of 4.98 m, a surface flow velocity of 1.16 m / s, a middle flow velocity of 1.09 m / s, and a bottom flow velocity of 1.0 m / s. A submarine pipeline model controlled by the soil spring constraint load was established.

[0067] (2) Based on the soil spring constraint load control submarine pipeline model established in step (1), the displacement of the submarine pipeline under the load of 9.1m water depth, 4.98m wave height, 1.16m / s surface velocity, 1.09m / s middle velocity and 1.0m / s bottom velocity is calculated. The maximum effective displacement U O =14.810m and maximum effective stress S O =425.786MPa;

[0068] (3) Sand throwing is used to prevent and control the above-mentioned pipeline exposure deviation problem. There are five sand throwing schemes, namely one-point sand throwing, two-point sand throwing, three-point sand throwing, four-point sand throwing and five-point sand throwing. The prevention and control length of each sand throwing point is 2m, and the sand throwing coverage should reach the coverage thickness of the larger constraint side. One-point sand throwing refers to throwing sand at the midpoint of the exposed section. Other schemes perform sand throwing at equidistant positions on the exposed section. For example, two-point sand throwing refers to throwing sand at the two dividing points of the exposed section into three sections. Based on the soil spring constraint load control submarine pipeline model established in step (1), the prevention and control method is simplified to incorporating soil spring constraints into the model. The soil spring constraint stiffness is consistent with the other side in (1). The effective displacement U of the pipeline after the implementation of each prevention and control scheme is calculated respectively. R and effective stress S R After one-point sand throwing, two-point sand throwing, three-point sand throwing, four-point sand throwing and five-point sand throwing, the effective displacement of the pipeline is U R are 4.600m, 2.770m, 1.411m, 0.362m, and 0.301m, and the effective stresses are U R They are 419.144MPa, 323.550MPa, 227.543MPa, 213.670MPa and 96.220MPa.

[0069] (4) The maximum effective displacement U of the submarine pipeline before prevention and control obtained by (2) O and (3) the effective displacement U after prevention and control R Calculate the displacement treatment effect index D based on formula (1) U , (3) The displacement control effect index D of the five prevention and control schemes U They are 69.27%, 83.11%, 91.43%, 97.56% and 97.97% respectively. The larger the index value, the better the effect of preventing and controlling the increase in displacement caused by pipeline deviation. The five prevention and control schemes are effective in preventing and controlling deviation displacement. As the number of prevention and control points increases, the displacement prevention effect increases, but the improvement effect increases more and more slowly.

[0070] (5) The maximum effective displacement S of the submarine pipeline before prevention and control obtained by (2) O and (3) the effective displacement S after prevention and control R Calculate the stress control effect index D based on formula (2) S , (3) The stress control effect index D of the five prevention and control schemes S They are 1.50%, 24.02%, 46.55%, 49.81% and 77.40% respectively. The larger the index value, the better the effect of preventing and controlling the stress increase caused by pipeline deviation. The stress control effect of the one-point sand throwing scheme is relatively poor. As the number of sand throwing points increases, the stress prevention and control effect increases.

[0071] (6) For the five prevention and control plans in (3), the total budget for planned treatment is B T The sand throwing project volume is 10m, and the implementation volume of the sand throwing program is B A The implementation amount of the two-point sand throwing scheme is 2m. A The implementation amount of the three-point sand throwing scheme is 4m. A The implementation amount of the four-point sand throwing scheme is 6m. A 8m, five-point sand throwing program implementation volume B A =10m, and the displacement control effect index D obtained by calculating the five control schemes is calculated using (4). U and the corresponding B A / B T Calculate the economic index ED of displacement treatment based on formula (3) U , five prevention and control schemes displacement control economic indicators ED U They are 346.35%, 207.77%, 152.39%, 121.94% and 97.97% respectively. The larger the index value, the better the displacement control effect and the superior economy of the scheme. It is easy to know that the displacement control effects of the first few schemes are good and the economy is superior.

[0072] (7) Using (5) to calculate the stress control effect index D of the five prevention and control schemes S and the corresponding B A / B T Calculate the stress management economic index ED based on formula (4) S , five prevention and control schemes stress management economic indicators ED U They are 7.50%, 60.06%, 77.58%, 62.26% and 77.40% respectively. The larger the index value, the better the stress control effect of the scheme and its superior economy. It is easy to know that the stress control effect of the latter several schemes is good and the economy is superior, among which the third scheme is particularly outstanding.

[0073] (8) Comprehensive displacement control effect index D U , stress management effect index D S , Economic index of displacement treatment effect ED U and stress control effect economic index ED S According to Table 1, the evaluation conclusions of the treatment effects of the five prevention and control schemes are given in Table 2. Among them, the three-point sand throwing scheme and the four-point sand throwing scheme have good overall treatment effects and good economy. Compared with the two, the three-point sand throwing scheme is more economical.

[0074] Table 2 Evaluation results of comprehensive treatment effects of five sand throwing schemes

[0075]

[0076]

[0077] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A quantitative evaluation method for the effectiveness of submarine pipeline deviation protection, including obtaining the maximum effective displacement U after pipeline deviation O and the maximum effective stress S O , obtain the effective displacement U of the pipeline after prevention and control R and effective stress S R , characterized in that, The treatment effect index is calculated by the above four parameters; the treatment effect index includes the displacement treatment effect index D U and stress management effect index D S The larger the value of the governance effect index is, the better the governance effect is.

2. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 1, characterized in that: The displacement treatment effect index DU=(UO-UR) / UO*100%.

3. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 1, characterized in that: The stress management effect index DS=(SO-SR) / SO*100%.

4. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 2 or 3, characterized in that: The maximum effective displacement UO and the maximum effective stress SO after the pipeline is deflected are obtained by the following steps: Obtain the actual route, pipeline parameters, soil parameters, and wave and current load data of the submarine pipeline before it is offset; Establish a submarine pipeline model controlled by soil spring constraint load; Assign pipe diameter, material, and wall thickness attributes; Calculate soil spring stiffness and set soil spring constraints based on pipeline burial status and soil type according to ASCE guidelines; Added the maximum wave and current depth, current and wave parameters in the transverse direction of the pipeline; Apply the maximum wave and current in the transverse direction of the pipeline as loads through the subroutine; By analyzing the influence of different lengths on the results, the constraint lengths on both sides of the submarine pipeline offset section are selected. The constraint lengths are continuously increased until a sufficient length is selected to ensure that the calculated displacement results change very little. Calculate the maximum effective displacement U after pipeline offset O and the maximum effective stress S O .

5. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 4, characterized in that: The effective displacement U of the pipeline after prevention and control R and effective stress S R Obtain it through the following steps: Based on the soil spring constraint load control submarine pipeline model, the displacement prevention method is incorporated into the model as a constraint, and the effective displacement U of the pipeline after prevention is calculated. R and effective stress S R .

6. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 5, characterized in that: It also includes the displacement management economic index ED U , used to illustrate the displacement treatment effect and economy of the scheme.

7. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 6, characterized in that: The displacement treatment economic index ED U The larger the index value is, the better the displacement control effect and the superior economic efficiency of the scheme are.

8. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 7, characterized in that: The displacement treatment economic index ED U Calculated by the following formula: ED U =D U / (B A / B T )。 9. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 5, characterized in that: Also includes stress management economic index ED S , used to illustrate the stress control effect and economy of the scheme.

10. A method for quantitatively evaluating the effectiveness of submarine pipeline deviation protection according to claim 9, characterized in that: The stress management economic index ED S Calculated by the following formula: ED S =D S / (B A / B T )。

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