Submarine pipeline anchoring part installation distance calculation method

Abstract

The invention discloses a submarine pipeline anchoring part installation distance calculation method, which belongs to the technical field of ocean oil and gas field development, and comprises the following steps: carrying out numerical simulation on an integral pipeline system, and establishing an integral model; calculating a subsea pipeline outlet logistics operation temperature; the joint of the vertical pipe and the horizontal pipe is taken as a starting point, a certain point, which is a certain distance away from the starting point, of the horizontal pipe is taken as a terminal point, and the total heat transfer coefficient of the subsea pipe section is increased due to failure of a heat insulation material of the subsea pipe; based on the total heat transfer coefficient of the enlarged pipe section, simulating and calculating the operation temperature of the logistics at the outlet of the subsea pipeline again; and determining the failure length of the total heat transfer coefficient as the mounting spacing distance of the anchoring parts. The installation distance calculated through the calculation method is more accurate and better conforms to the actual site situation, a large number of tests are not needed, and a large number of offshore construction resources are saved.

Description

Technical Field

[0001] The invention belongs to the technical field of marine oil and gas field development, and in particular relates to a method for calculating the installation distance of anchor pieces for submarine pipelines. Background Art

[0002] At present, the development of offshore oil and gas fields in the Bohai Sea area of ​​my country is rapid, and the Bohai Oilfield has become the largest crude oil production base in the country. The oil and gas fields within and between the oilfield blocks are connected by submarine pipelines to ensure that the produced oil and gas can be smoothly transported, processed and shipped. However, the pipeline transportation of some high-condensation and high-viscosity crude oils can easily cause flow assurance problems such as high condensation pipe pressure due to heat loss during transportation, affecting the normal production of oil and gas fields. Therefore, the use of double-layer insulated pipes can effectively utilize the insulation effect of the insulation layer to reduce the heat loss of the fluid inside the pipeline.

[0003] However, if an accident occurs and the insulation layer of the pipeline fails, causing the fluid outlet temperature to be lower than the freezing point, the pipeline will be shut down, resulting in loss of oilfield revenue. To avoid this phenomenon, it is necessary to install an anchor at a certain distance on the horizontal pipe section on the seabed to physically isolate the insulation material. Even if the insulation material of a certain section of the pipeline fails, it will not affect the normal operation of the entire pipeline. The advantage of installing anchors is that it can extend the service life of the pipeline after the insulation layer fails, and buy time for online maintenance of the pipeline without stopping. In addition, reasonably determining the installation interval of anchors and avoiding too dense installation of anchors can not only save material costs, but also greatly reduce offshore construction costs and reduce the number of ship days for laying pipes. However, there is no known and recognized calculation method in China for how to accurately determine the installation interval of anchors, and innovative design is needed.

[0004] Therefore, it is urgent to design a method for calculating the installation distance of submarine pipeline anchors to solve the above-mentioned problems. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the installation distance of submarine pipeline anchors, which has the advantage of being able to determine the installation interval distance of submarine pipeline anchors and solves the problems solved in the background technology.

[0006] To achieve the above purpose, a specific technical solution of a method for calculating the installation distance of a submarine pipeline anchor of the present invention is as follows: A method for calculating the installation distance of a submarine pipeline anchor comprises the following steps: S1. Perform numerical simulation on the overall pipeline system and establish an overall model; S2. Calculate the operating temperature of the sea pipeline outlet logistics, which must be at least 5°C higher than the freezing point of crude oil; S3, with the connection between the vertical pipe and the horizontal pipe as the starting point and a point on the horizontal pipe at a certain distance from the starting point as the end point, the total heat transfer coefficient of this section of the sea pipe becomes larger due to the failure of the insulation material of this pipeline; S4. Based on the total heat transfer coefficient of the enlarged pipe section, the specification parameters and total heat transfer coefficient of other pipelines remain unchanged, and the operating temperature of the sea pipeline outlet logistics is re-simulated and calculated so that the temperature is reduced to 5°C above the freezing point of crude oil; S5. Determine the length at which the total heat transfer coefficient fails as the anchor installation spacing distance.

[0007] Furthermore, in S1, the internationally used flow assurance static simulation software PIPEFLO is used to perform numerical simulation on the overall pipeline system.

[0008] Furthermore, the overall model includes an inlet logistics source and an overall pipeline system, the overall pipeline system includes a first riser, a second riser and a horizontal pipe, both ends of the horizontal pipe are respectively connected to the first riser and the second riser, and the first riser and the second riser are respectively connected to the corresponding inlet logistics source.

[0009] Furthermore, the inlet logistics source information parameters include the allocated production of oil, gas and water, the relative density of oil, gas and water, the viscosity data of crude oil emulsion at different temperatures and water contents, and the starting temperature of the inlet logistics.

[0010] Furthermore, the physical properties of the inlet stream source include the viscosity of the crude oil at different temperatures and cover the temperature range experienced by the entire pipeline.

[0011] Furthermore, in S1, an overall model is established according to the development mode and basic parameters of the target oil and gas field.

[0012] Furthermore, in S2, the operating temperature of the sea pipeline outlet logistics is calculated based on parameters such as the physical properties of the inlet logistics source, the allocated production and the starting temperature, the sea pipeline outlet pressure, the minimum ambient temperature, and the total heat transfer coefficient.

[0013] Furthermore, the lowest environmental temperature is the extremely low temperature of the air, the extremely low temperature of the sea water, and the extremely low temperature of the soil deep inside the horizontal pipe burial.

[0014] Furthermore, the viscosity data of crude oil emulsions at different temperatures and water contents cover the logistics temperature along the pipeline during transportation.

[0015] Furthermore, the total heat transfer coefficient remains consistent throughout the entire pipeline, and when the insulation layer fails, the total heat transfer coefficient of the failed section will surge.

[0016] The present invention has the following advantages: a double-layer insulated submarine pipeline model between full-process platforms is established by using the static simulation software PIPEFLO, and the failure length of the submarine pipeline insulation layer, that is, the interval distance of the anchor installation, is simulated by changing the total heat transfer coefficient of the horizontal pipe, so as to ensure that the entire submarine pipeline can continue to operate safely after a certain pipe section fails. The installation distance calculated by the calculation method of the present invention is more accurate and more in line with the actual situation on site, and a large number of tests do not need to be carried out, thereby saving a large number of offshore construction resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the overall model of the present invention; Figure 2 This is a schematic diagram of the connection structure between the anchor and the sea pipe of the present invention; Explanation of the markings in the figure: 1. first riser; 11. first inlet logistics source; 12. second inlet logistics source; 2. horizontal pipe; 21. outer pipe; 22. inner pipe; 3. second riser; 4. anchor. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0019] Those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0020] Please refer to the attached Figure 1 To Attachment Figure 2 The present invention describes a method for calculating the installation distance of a submarine pipeline anchor.

[0021] At present, if an accident occurs and the insulation layer of the pipeline fails, the fluid outlet temperature will be lower than the freezing point, which will cause the pipeline to stop transmitting and result in loss of oilfield revenue. To avoid this phenomenon, an anchor needs to be installed at a certain interval on the horizontal pipe section on the seabed. However, there is no known and recognized calculation method in China for accurately determining the installation interval of the anchors, so innovative design is needed.

[0022] Therefore, the method for calculating the installation distance of the submarine pipeline anchor includes the following steps: S1. Perform numerical simulation on the overall pipeline system and establish an overall model; Preferably, the overall pipeline system is numerically simulated using the internationally used flow assurance static simulation software PIPEFLO.

[0023] The overall model includes an inlet logistics source and an overall pipeline system. The overall pipeline system includes a first riser 1, a second riser 3 and a horizontal pipe 2. Both ends of the horizontal pipe 2 are respectively connected to the first riser 1 and the second riser 3. The first riser 1 and the second riser 3 are respectively connected to the corresponding inlet logistics sources.

[0024] The inlet logistics source comprises a first inlet logistics source 11 and a second inlet logistics source 12 . The first inlet logistics source 11 is connected to the first riser 1 , and the second inlet logistics source 12 is connected to the second riser 3 .

[0025] Furthermore, the inlet logistics source information parameters include the allocated production of oil, gas and water, the relative density of oil, gas and water, the viscosity data of crude oil emulsion at different temperatures and water contents, and the starting temperature of the inlet logistics.

[0026] Furthermore, the physical properties of the inlet stream source include the viscosity of the crude oil at different temperatures and cover the temperature range experienced by the entire pipeline.

[0027] Furthermore, an overall model is established based on the development mode and basic parameters of the target oil and gas fields.

[0028] The operating temperature of the sea pipeline outlet logistics is calculated based on the physical properties of the inlet logistics source, the allocated production and starting temperature, the sea pipeline outlet pressure, the minimum ambient temperature, the total heat transfer coefficient and other parameters.

[0029] Furthermore, the lowest ambient temperature is the extremely low temperature of the air, the extremely low temperature of the seawater, and the extremely low temperature of the soil at the depth where the horizontal pipe 2 is buried.

[0030] Furthermore, the viscosity data of crude oil emulsions at different temperatures and water contents cover the logistics temperature along the pipeline during transportation.

[0031] Furthermore, the total heat transfer coefficient remains consistent throughout the entire pipeline, and when the insulation layer fails, the total heat transfer coefficient of the failed section will surge.

[0032] S2. Calculate the operating temperature of the sea pipeline outlet logistics, which must be at least 5°C higher than the freezing point of crude oil; S3, taking the connection between the vertical pipe and the horizontal pipe 2 as the starting point and a certain point of the horizontal pipe 2 at a certain distance from the starting point as the end point, the total heat transfer coefficient of this section of the sea pipe becomes larger due to the failure of the insulation material of this pipeline; The pipe section with total heat transfer coefficient failure is the front end, middle section or tail end of the horizontal pipe 2. Conservatively considering the shortest failure length, it is the installation interval length of the anchor 4.

[0033] S4. Based on the total heat transfer coefficient of the enlarged pipe section, the specification parameters and total heat transfer coefficient of other pipelines remain unchanged, and the operating temperature of the sea pipeline outlet logistics is re-simulated and calculated so that the temperature is reduced to 5°C above the freezing point of crude oil; S5. Determine the length at which the total heat transfer coefficient fails as the installation spacing distance of the anchor 4.

[0034] The horizontal tube 2 includes an inner tube 22 and an outer tube 21 . The anchor 4 is in an I-shape. The long side end of the anchor 4 is connected to the inner tube 22 , and the short side end of the anchor 4 is connected to the outer tube 21 .

[0035] Specific implementation of the present invention: The first inlet logistics source 11 is connected to the horizontal pipe 2 through the first riser 1, and then the end of the horizontal pipe 2 away from the first riser 1 is connected back to the second inlet logistics source 12 through the second riser 3. The model and equation of the PIPEFLO software are selected, and the operating temperature of the sea pipeline outlet logistics is calculated to be 42°C based on the physical properties of the inlet logistics source, the specific gravity of each material, the allocated production, the viscosity-temperature data of the crude oil and the starting temperature, the sea pipeline outlet pressure, the lowest temperature of the air, sea cement and soil environment, the total heat transfer coefficient, the specifications of the pipeline and other parameters. It is at least 5°C higher than the freezing point of crude oil of 31°C to ensure the normal flow of logistics.

[0036] The length of the submarine horizontal pipe 2 is 31.5 km. It starts from the connection between the first riser 1 and the horizontal pipe 2 and ends at a point of the horizontal pipe 2 at a certain distance from the starting point. The total heat transfer coefficient of this section of the submarine pipeline increases sharply from 14 W / (m2•°C) to 80 W / (m2•°C) due to the failure of the insulation material of this section.

[0037] Based on the total heat transfer coefficient of the enlarged pipe section, the specification parameters and total heat transfer coefficient of other pipelines remain unchanged. The logistics operating temperature of the offshore pipeline outlet is re-simulated and calculated, so that this temperature is reduced to 36°C, which is 5°C above the crude oil freezing point of 31°C.

[0038] The length of the pipe section at which the total heat transfer coefficient fails at the starting end is determined to be the installation interval distance of the anchor 4, 1001m.

[0039] Assuming that the failed pipe section occurs in the middle of horizontal pipe 2, taking the connection between the first riser 1 and horizontal pipe 2 as the starting point, about 15.5 km from the seabed horizontal pipe 2, the length of the pipe section where the total heat transfer coefficient fails is determined to be 1055 m.

[0040] Assuming that the failed pipe section occurs at the tail end of horizontal pipe 2, with the connection between the first riser 1 and horizontal pipe 2 as the starting point, about 30.5 km from the seabed horizontal pipe 2, the length of the pipe section where the total heat transfer coefficient fails is determined to be 1101 m.

[0041] The three insulation layer failure lengths are compared, and the shortest length of the three, 1001 m, is taken as the final installation spacing distance of the anchor 4 and implemented on the entire horizontal pipe 2.

[0042] If the entire submarine pipeline is not installed with anchors 4, once the outer pipe 21 is damaged due to an accident, seawater enters the insulation layer, causing the insulation to fail, and the logistics temperature at the outlet of the submarine pipeline is lower than the freezing point, the submarine pipeline will not be able to transport normally, causing immeasurable economic losses. If the anchors 4 are installed at the calculated appropriate distance, the extension of the insulation failure length can be effectively prevented, the submarine pipeline can be ensured to be used normally, and time can be saved for pipeline maintenance.

[0043] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for calculating the installation distance of submarine pipeline anchors, characterized in that: The following steps are involved: S1. Perform numerical simulation on the overall pipeline system and establish an overall model; S2. Calculate the operating temperature of the sea pipeline outlet logistics, which must be at least 5°C higher than the freezing point of crude oil; S3, with the connection between the vertical pipe and the horizontal pipe as the starting point and a point on the horizontal pipe at a certain distance from the starting point as the end point, the total heat transfer coefficient of this section of the sea pipe becomes larger due to the failure of the insulation material of this pipeline; S4. Based on the total heat transfer coefficient of the enlarged pipe section, the specification parameters and total heat transfer coefficient of other pipelines remain unchanged, and the operating temperature of the sea pipeline outlet logistics is re-simulated and calculated so that the temperature is reduced to 5°C above the freezing point of crude oil; S5. Determine the length at which the total heat transfer coefficient fails as the anchor installation spacing.

2. The method for calculating the installation distance of submarine pipeline anchors according to claim 1, characterized in that: In S1, the internationally used flow assurance static simulation software PIPEFLO is used to perform numerical simulation of the entire pipeline system.

3. The method for calculating the installation distance of submarine pipeline anchors according to claim 2 is characterized in that: The overall model includes an inlet logistics source and an overall pipeline system. The overall pipeline system includes a first riser, a second riser and a horizontal pipe. Both ends of the horizontal pipe are respectively connected to the first riser and the second riser. The first riser and the second riser are respectively connected to the corresponding inlet logistics source.

4. The method for calculating the installation distance of submarine pipeline anchors according to claim 3 is characterized in that: The inlet logistics source information parameters include the allocated production of oil, gas and water, the relative density of oil, gas and water, the viscosity data of crude oil emulsion at different temperatures and water contents, and the starting temperature of the inlet logistics.

5. The method for calculating the installation distance of submarine pipeline anchors according to claim 4 is characterized in that: The physical properties of the inlet stream include the viscosity of the crude oil at different temperatures and cover the temperature range experienced by the entire pipeline.

6. The method for calculating the installation distance of submarine pipeline anchors according to claim 1, characterized in that: In S1, an overall model is established based on the development mode and basic parameters of the target oil and gas fields.

7. The method for calculating the installation distance of submarine pipeline anchors according to claim 1, characterized in that: In S2, the operating temperature of the sea pipeline outlet logistics is calculated based on the physical properties of the inlet logistics source, the allocated production and starting temperature, the sea pipeline outlet pressure, the minimum ambient temperature, the total heat transfer coefficient and other parameters.

8. The method for calculating the installation distance of submarine pipeline anchors according to claim 7, characterized in that: The lowest ambient temperature is the extremely low temperature of the air, the extremely low temperature of the sea water, and the extremely low temperature of the soil deep inside the horizontal pipe burial.

9. The method for calculating the installation distance of submarine pipeline anchors according to claim 1, characterized in that: The viscosity data of crude oil emulsions at different temperatures and water contents cover the logistics temperature along the pipeline during transportation.

10. The method for calculating the installation distance of submarine pipeline anchors according to claim 1, characterized in that: The total heat transfer coefficient remains consistent throughout the entire pipeline. When the insulation layer fails, the total heat transfer coefficient of the failed section will surge.

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