A method for identifying high-risk hydrate formation areas of a submarine pipeline

Abstract

The application discloses a method for identifying a high-risk hydrate formation area of a submarine pipeline, and the method comprises the following steps: performing three-dimensional multiphase flow simulation on the submarine pipeline to obtain flow parameters along the pipeline; combining hydrate formation temperature, pressure and liquid holdup of the pipeline during pipeline flow to determine the hydrate formation condition; constructing hydrate formation risk evaluation matrices I and II; and identifying the high-risk hydrate formation area of the submarine pipeline, so as to provide an effective means for guaranteeing safe operation of the submarine pipeline.

Description

Technical Field

[0001] This invention relates to a method for identifying high-risk hydrate formation areas in subsea pipelines, specifically for identifying hydrate formation risk areas in subsea pipelines. Background Technology

[0002] In the field of offshore oil and gas resource development, subsea pipelines serve as critical infrastructure for oil and gas transportation, and their safe and stable operation is of paramount importance. However, the formation of hydrates has always been one of the major challenges affecting the normal operation of subsea pipelines.

[0003] With the continued growth of global energy demand, offshore oil and gas resources are being gradually exploited. Hydrates are ice-like crystalline compounds formed from natural gas and water under certain temperature and pressure conditions. If hydrates form in large quantities in subsea pipelines, they can easily cause blockages, leading to obstructed fluid flow, abnormally high pressure, and even pipeline ruptures, posing serious safety hazards to offshore oil and gas extraction and transportation.

[0004] Currently, identifying risk areas for hydrate formation in subsea pipelines presents numerous challenges. Firstly, the complex and variable subsea environment, with the interaction of factors such as temperature, pressure, fluid composition, and flow velocity, means that the mechanism of hydrate formation is not fully understood, making it difficult to accurately determine its location and conditions. Secondly, the significant differences in geological conditions and seawater properties across different sea areas further complicate the identification process.

[0005] On the other hand, existing identification technologies and methods still have limitations. Some traditional detection methods, such as those based on temperature and pressure monitoring, can only provide macroscopic environmental parameters and cannot accurately determine the specific areas where hydrates are formed. While some detection technologies based on acoustic and optical principles can detect hydrates to a certain extent, their accuracy and reliability need to be improved due to interference from the complex seabed environment.

[0006] Furthermore, with the continuous expansion of subsea oil and gas pipelines, how to efficiently and comprehensively identify risk areas along these pipelines is a pressing issue. Existing methods are often inefficient when dealing with large-scale data and complex pipeline systems, making it difficult to meet the needs of practical engineering projects.

[0007] This invention establishes a method for identifying high-risk hydrate formation areas in subsea pipelines based on numerical simulation, which has important practical significance for ensuring the safe and stable development of marine oil and gas resources. Summary of the Invention

[0008] This invention proposes a method for identifying high-risk hydrate formation areas in subsea pipelines in order to identify risk areas for hydrate formation and reduce pipeline blockage and rupture accidents caused by hydrate formation.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] S1: Establish a full-size model of the subsea pipeline, conduct multiphase flow simulation, calculate flow parameters along the pipeline, and collect data;

[0011] S2: Based on multiphase flow simulation parameters and data, clarify the hydrate formation model in the pipeline;

[0012] S3: By studying the hydrate formation model, determine the hydrate formation temperature and pressure under pipeline flow conditions;

[0013] S4: Calculate the liquid holdup in the pipeline and determine the hydrate formation in the pipeline;

[0014] S5: Based on the calculation results of the difference between hydrate formation temperature and pipeline flow temperature ΔT and the difference between pipeline flow pressure and hydrate formation pressure ΔP, establish hydrate formation risk assessment matrix I and hydrate formation risk assessment matrix II.

[0015] S6: When the liquid holdup in the pipeline is >0, determine the critical temperature based on the trend of the hydrate phase equilibrium curve without the addition of any hydrate inhibitor, taking a slope of 1 as the critical point. T l ;

[0016] S7: Compare pipe flow temperatures T m and critical temperature T l The size of the matrix determines the risk assessment matrix for hydrate formation.

[0017] S8: Identify high-risk hydrate formation areas for subsea pipelines using a hydrate formation risk assessment matrix.

[0018] Furthermore, the calculation formula for the hydrate formation model in the pipeline is as follows:

[0019]

[0020] In the formula, p Pressure, Pa; R Let J be the gas constant, J / (mol·K); T Temperature, K; V m is the molar volume. 3 / mol; a The energy parameter of the equation of state is Pa·m. 6 / mol 2 b is the volume parameter in the equation of state, m 3 / mol; c is the volume correction parameter for the equation of state, m 3 / mol.

[0021] Furthermore, the formation of hydrates in the pipeline is determined according to the following steps;

[0022] 201: When the liquid holdup is <0, it is determined that hydrates will not form in the pipeline;

[0023] 202: When the liquid holdup is >0, it is determined that hydrates may be generated in the pipeline.

[0024] Furthermore, the hydrate formation risk assessment matrix I is established according to the following steps;

[0025] 301: When ΔP < 0 bara, if ΔT < 0℃, the risk level of hydrate formation is "None";

[0026] 302: When ΔP < 0 bara, if 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is "Low";

[0027] 303: When 0 bara < ΔP ≤ 0.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is “Low”.

[0028] 304: When 0.5 bara < ΔP ≤ 1.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, and 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Low".

[0029] 305: When 0.5 bara < ΔP ≤ 1.5 bara, if ΔT > 5℃, the risk level of hydrate formation is "Medium";

[0030] 306: When ΔP > 1.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, or 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is “Medium”.

[0031] 307: When ΔP > 1.5 bara, if ΔT > 5℃, the risk level of hydrate formation is "High".

[0032] Furthermore, the hydrate formation risk assessment matrix II is established according to the following steps;

[0033] 401: When ΔP < 0 bara, if ΔT < 0℃, the risk level of hydrate formation is "None";

[0034] 402: When ΔP < 0 bara, if 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk of hydrate formation is "Low";

[0035] 403: When 0 bara < ΔP ≤ 38 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is "Low".

[0036] 404: When 38 bara < ΔP ≤ 63 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, and 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Low".

[0037] 405: When 38 bara < ΔP ≤ 63 bara, if ΔT > 5℃, the risk level of hydrate formation is "Medium";

[0038] 406: When ΔP > 63 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, or 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is “Medium”.

[0039] 407: When ΔP > 63 bara, if ΔT > 5℃, the risk level of hydrate formation is "High".

[0040] Furthermore, the determination of the hydrate formation risk assessment matrix in step S7 is calculated according to the following steps:

[0041] 501: When T m < T l Select hydrate formation risk assessment matrix I;

[0042] 502: When T m > T l Select the hydrate formation risk assessment matrix II.

[0043] Furthermore, in step S8, the high-risk hydrate formation area of ​​the subsea pipeline is determined as "High" by calculating the hydrate formation risk assessment matrix. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the identification process for high-risk hydrate areas along subsea pipelines according to the present invention.

[0045] Figure 2 This is a map showing the risk zone for hydrate formation in the subsea pipeline according to the present invention. Detailed Implementation

[0046] A method for identifying high-risk hydrate formation areas along subsea pipelines, characterized by comprising the following steps:

[0047] S1: Establish a full-size model of the subsea pipeline, conduct multiphase flow simulation, calculate flow parameters along the pipeline, and collect data;

[0048] S2: Based on multiphase flow simulation parameters and data, clarify the hydrate formation model in the pipeline;

[0049] S3: By studying the hydrate formation model, determine the hydrate formation temperature and pressure under pipeline flow conditions;

[0050] S4: Calculate the liquid holdup in the pipeline and determine the hydrate formation in the pipeline;

[0051] S5: Based on the calculation results of the difference between hydrate formation temperature and pipeline flow temperature ΔT and the difference between pipeline flow pressure and hydrate formation pressure ΔP, establish hydrate formation risk assessment matrix I and hydrate formation risk assessment matrix II.

[0052] S6: When the liquid holdup in the pipeline is >0, determine the critical temperature based on the trend of the hydrate phase equilibrium curve without the addition of any hydrate inhibitor, taking a slope of 1 as the critical point. T l ;

[0053] S7: Compare pipe flow temperatures T m and critical temperature T l The size of the matrix determines the risk assessment matrix for hydrate formation.

[0054] S8: Identify high-risk hydrate formation areas for subsea pipelines using a hydrate formation risk assessment matrix.

[0055] The calculation formula for the hydrate formation model in the pipeline is as follows:

[0056]

[0057] In the formula, p Pressure, Pa; R Let J be the gas constant, J / (mol·K); T Temperature, K; V m is the molar volume. 3 / mol; a The energy parameter of the equation of state is Pa·m. 6 / mol 2 b is the volume parameter in the equation of state, m 3 / mol; c is the volume correction parameter for the equation of state, m 3 / mol.

[0058] The formation of hydrates in the pipeline is determined according to the following steps:

[0059] 201: When the liquid holdup is <0, it is determined that hydrates will not form in the pipeline;

[0060] 202: When the liquid holdup is >0, it is determined that hydrates may be generated in the pipeline.

[0061] The hydrate formation risk assessment matrix I is established according to the following steps:

[0062] 301: When ΔP < 0 bara, if ΔT < 0℃, the risk level of hydrate formation is "None";

[0063] 302: When ΔP < 0 bara, if 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is "Low";

[0064] 303: When 0 bara < ΔP ≤ 0.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is “Low”.

[0065] 304: When 0.5 bara < ΔP ≤ 1.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, and 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Low".

[0066] 305: When 0.5 bara < ΔP ≤ 1.5 bara, if ΔT > 5℃, the risk level of hydrate formation is "Medium";

[0067] 306: When ΔP > 1.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, or 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is “Medium”.

[0068] 307: When ΔP > 1.5 bara, if ΔT > 5℃, the risk level of hydrate formation is "High".

[0069] The hydrate formation risk assessment matrix II is established according to the following steps:

[0070] 401: When ΔP < 0 bara, if ΔT < 0℃, the risk level of hydrate formation is "None";

[0071] 402: When ΔP < 0 bara, if 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk of hydrate formation is "Low";

[0072] 403: When 0 bara < ΔP ≤ 38 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is “Low”.

[0073] 404: When 38 bara < ΔP ≤ 63 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, and 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Low".

[0074] 405: When 38 bara < ΔP ≤ 63 bara, if ΔT > 5℃, the risk level of hydrate formation is "Medium";

[0075] 406: When ΔP > 63 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, or 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is “Medium”.

[0076] 407: When ΔP > 63 bara, if ΔT > 5℃, the risk level of hydrate formation is "High".

[0077] The determination of the hydrate formation risk assessment matrix in step S7 is calculated according to the following steps:

[0078] 501: When T m < T l Select hydrate formation risk assessment matrix I;

[0079] 502: When T m > T l Select the hydrate formation risk assessment matrix II.

[0080] In step S8, the high-risk hydrate formation area of ​​the subsea pipeline is determined as "High" by calculating the hydrate formation risk assessment matrix.

Claims

1. A method for identifying high-risk hydrate formation areas along subsea pipelines, characterized in that, Includes the following steps: S1: Establish a full-size model of the subsea pipeline, conduct multiphase flow simulation, calculate flow parameters along the pipeline, and collect data; S2: Based on multiphase flow simulation parameters and data, clarify the hydrate formation model in the pipeline; S3: By studying the hydrate formation model, determine the hydrate formation temperature and pressure under pipeline flow conditions; S4: Calculate the liquid holdup in the pipeline and determine the hydrate formation in the pipeline; S5: Based on the calculation results of the difference between hydrate formation temperature and pipeline flow temperature ΔT and the difference between pipeline flow pressure and hydrate formation pressure ΔP, establish hydrate formation risk assessment matrix I and hydrate formation risk assessment matrix II. S6: When the liquid holdup in the pipeline is >0, determine the critical temperature based on the trend of the hydrate phase equilibrium curve without the addition of any hydrate inhibitor, taking a slope of 1 as the critical point. T l ; S7: Compare pipe flow temperatures T m and critical temperature T l The size of the matrix determines the risk assessment matrix for hydrate formation. S8: Identify high-risk hydrate formation areas for subsea pipelines using a hydrate formation risk assessment matrix.

2. The method for identifying high-risk hydrate formation areas in subsea pipelines as described in claim 1, characterized in that, The calculation formula for the hydrate formation model in the pipeline is as follows: In the formula, Pressure, Pa; Let J be the gas constant, J / (mol·K); Temperature, K; m is the molar volume. 3 / mol; The energy parameter of the equation of state is Pa·m. 6 / mol 2 ; Let m be the volume parameter in the equation of state. 3 / mol; m is the volume correction parameter for the equation of state. 3 / mol.

3. The method for identifying high-risk hydrate formation areas in subsea pipelines as described in claim 1, characterized in that, The formation of hydrates in the pipeline is determined according to the following steps: 201: When the liquid holdup is <0, it is determined that hydrates will not form in the pipeline; 202: When the liquid holdup is >0, it is determined that hydrates may be generated in the pipeline.

4. The method for identifying high-risk hydrate formation areas in subsea pipelines as described in claim 1, characterized in that, The hydrate formation risk assessment matrix I is established according to the following steps: 301: When ΔP < 0 bara, if ΔT < 0℃, the risk level of hydrate formation is "None"; 302: When ΔP < 0 bara, if 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is "Low"; 303: When 0 bara < ΔP ≤ 0.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is "Low". 304: When 0.5 bara < ΔP ≤ 1.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, and 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Low". 305: When 0.5 bara < ΔP ≤ 1.5 bara, if ΔT > 5℃, the risk level of hydrate formation is "Medium"; 306: When ΔP > 1.5 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, or 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Medium". 307: When ΔP > 1.5 bara, if ΔT > 5℃, the risk level of hydrate formation is "High".

5. The method for identifying high-risk hydrate formation areas in subsea pipelines as described in claim 1, characterized in that, The hydrate formation risk assessment matrix II is established according to the following steps: 401: When ΔP < 0 bara, if ΔT < 0℃, the risk level of hydrate formation is "None"; 402: When ΔP < 0 bara, if 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk of hydrate formation is "Low"; 403: When 0 bara < ΔP ≤ 38 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, 3℃ < ΔT ≤ 5℃, or ΔT > 5℃, the risk level of hydrate formation is "Low". 404: When 38 bara < ΔP ≤ 63 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, and 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Low". 405: When 38 bara < ΔP ≤ 63 bara, if ΔT > 5℃, the risk level of hydrate formation is "Medium"; 406: When ΔP > 63 bara, if ΔT < 0℃, 0℃ < ΔT ≤ 3℃, or 3℃ < ΔT ≤ 5℃, the risk level of hydrate formation is "Medium". 407: When ΔP > 63 bara, if ΔT > 5℃, the risk level of hydrate formation is "High".

6. The method for identifying high-risk hydrate formation areas in subsea pipelines as described in claim 1, characterized in that, The determination of the hydrate formation risk assessment matrix in step S7 is calculated according to the following steps: 501: When T m < T l Select hydrate formation risk assessment matrix I; 502: When T m > T l Select the hydrate formation risk assessment matrix II.

7. The method for identifying high-risk hydrate formation areas in subsea pipelines as described in claim 1, characterized in that, In step S8, the high-risk hydrate formation area of ​​the subsea pipeline is determined as "High" by calculating the hydrate formation risk assessment matrix.

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