A method for designing a subsea pipeline anti-hammer

Abstract

The application relates to a kind of submarine pipeline water hammer prevention design methods, comprising the following steps: S1. according to the average density calculated by the mixed proportion of oil, gas and water in the conveying pipeline;S2. the pressure in the conveying pipeline at the fluid receiving station and the pressure in the conveying pipeline at the buffer device needed to be installed are calculated, and the conveying distance from the buffer device to the receiving station is measured;S3. the volume of the buffer bin is calculated according to the pressure in step S2, the seawater pressure at the buffer device, the fluid flow in the conveying pipeline and the conveying distance in step S2;S4. the diameter of the buffer port from the conveying pipeline to the buffer bin is calculated according to the volume of the buffer bin in step S3, the fluid inertia force and the gas precipitation rate;S5. the valve opening pressure of the air pressure reducing valve at the top of the buffer bin is calculated according to the pressure in the conveying pipeline at the buffer device in step S2. The application mainly explores the application of the buffer device in submarine pipeline water hammer prevention, and provides a reference for designing the buffer device in submarine pipeline.

Description

Technical Field

[0001] This invention relates to the field of subsea pipeline technology, and in particular to a design method for waterproof hammer prevention in subsea pipelines. Background Technology

[0002] Subsea pipelines are a type of closed pipeline that continuously transports large quantities of oil (gas) across the seabed. They are a major component of offshore oil (gas) development and production systems.

[0003] Water hammer refers to the sudden change in fluid velocity and subsequent large fluctuations in pressure during fluid transportation caused by factors such as the sudden opening or closing of valves or the sudden shutdown of pumps. Water hammer poses numerous hazards and has a significant impact. Currently, water hammer protection devices for long-distance subsea pipelines mainly include air tanks and pressure regulating towers, but the application of buffer devices in subsea pipelines is relatively limited.

[0004] Therefore, those skilled in the art are dedicated to developing a design method for waterproof hammers in subsea pipelines, mainly exploring the application of buffer devices in waterproof hammers in subsea pipelines, and providing a reference for the design of buffer devices in subsea pipelines. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a design method for waterproof hammer in subsea pipelines. It mainly explores the application of buffer devices in waterproof hammer in subsea pipelines and provides a reference for the design of buffer devices in subsea pipelines.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for designing waterproof hammers for subsea pipelines, comprising the following steps:

[0007] S1. Calculate the average density based on the mixing ratio of oil, gas and water in the pipeline;

[0008] S2. Calculate the pressure in the conveying pipeline where the buffer device needs to be installed and the pressure in the conveying pipeline at the fluid receiving station, and measure the conveying distance from the buffer device to the receiving station;

[0009] S3. Calculate the volume of the buffer chamber based on the pressures in step S2, the seawater pressure at the buffer device, the fluid flow rate in the conveying pipeline, and the conveying distance in step S2.

[0010] S4. Calculate the diameter of the buffer inlet from the delivery pipeline to the buffer chamber based on the volume of the buffer chamber, the fluid inertial force, and the gas evolution rate in step S3.

[0011] S5. Calculate the opening pressure of the air pressure reducing valve at the top of the buffer chamber based on the pressure in the conveying pipeline at the buffer device in step S2.

[0012] The beneficial effects of this invention are: by calculating the volume of the buffer chamber, the diameter of the buffer port, and the opening pressure of the pressure reducing valve that need to be added to the pipeline based on the pressure and the transportation distance at various points in the submarine pipeline, when the fluid in the pipeline suddenly changes, the buffer chamber and the air pressure reducing valve work together to eliminate the water hammer generated in the pipeline, thereby avoiding damage to the pipeline and its accessories caused by the water hammer.

[0013] Based on the above technical solution, the present invention can be further improved as follows.

[0014] Furthermore, in step S2, the formula for calculating the volume of the buffer chamber is as follows:

[0015]

[0016] Among them, V 仓 This refers to the volume of the buffer compartment;

[0017] P0 is the seawater pressure at the buffer device;

[0018] P1 is the pressure inside the delivery pipeline at the buffer device;

[0019] P2 is the pressure inside the pipeline at the fluid receiving station;

[0020] Q represents the fluid flow rate;

[0021] L is the conveying distance from the buffer device to the receiving station;

[0022] k1 is the medium constant.

[0023] The advantage of adopting the above-mentioned further solution is that it allows for the calculation of the required volume of the buffer chamber and reduces the water hammer effect in the delivery pipeline.

[0024] Furthermore, in step S1, the formula for calculating the average density of oil, water, and gas is as follows:

[0025]

[0026] Where, ρ 平 This is the average density, expressed in kg / m³. 3

[0027] ρ1 is the density of the oil at the bottom of the delivery pipe;

[0028] v1 is the unit volume of oil in the bottom of the delivery pipe;

[0029] ρ2 is the density of the water at the bottom of the conveying pipe;

[0030] v2 is the unit volume of water at the bottom of the conveying pipe;

[0031] ρ3 is the density of the gas at the bottom of the delivery pipe;

[0032] v3 is the unit volume of gas at the bottom of the delivery pipe.

[0033] The advantage of adopting the above-mentioned further scheme is that the average density is used to calculate the volume of the subsequent buffer chamber.

[0034] Furthermore, in step S2, the formula for calculating the pressure P2 in the conveying pipeline at the fluid receiving station is as follows:

[0035] P2=ρ 平 *V 流 *k2

[0036] Wherein, P2 is the pressure inside the conveying pipeline at the fluid receiving station;

[0037] ρ 平 Average density;

[0038] V 流 The fluid velocity;

[0039] k2 is the medium constant.

[0040] The advantage of adopting the above-mentioned further scheme is that it allows for the calculation of the pressure in the conveying pipeline at the receiving station, which can then be used to calculate the volume of the buffer chamber and the diameter of the buffer opening.

[0041] Furthermore, in step S2, the formula for calculating the pressure P1 in the conveying pipe at the buffer device is as follows:

[0042] P1=P2+ρ 平 *g*L / J

[0043] Where L is the conveying distance from the buffer device to the receiving station;

[0044] J represents the slope.

[0045] The advantage of adopting the above-mentioned further scheme is that it allows for the calculation of the pressure in the conveying pipeline at the buffer device, which is then used to calculate the volume of the buffer chamber and the diameter of the buffer opening.

[0046] Furthermore, in step S4, the formula for calculating the diameter R of the buffer opening is as follows:

[0047]

[0048] υ t =ρ 平 *υ k *k3

[0049] Among them, υ 析 The gas evolution rate;

[0050] k3 is a characteristic constant;

[0051] υ k This refers to the velocity at which the fluid enters the buffer chamber.

[0052] The beneficial effect of adopting the above-mentioned further scheme is that the diameter of the buffer port can be calculated, and when the fluid motion state changes, some fluid can enter the buffer chamber in a timely manner.

[0053] Furthermore, in step S5, the opening pressure P of the air pressure reducing valve... 启 The calculation formula is:

[0054] P 启 = (P0-P1)*K4

[0055] Where k4 is the valve opening constant.

[0056] The advantage of adopting the above-mentioned further solution is that the valve opening pressure is calculated and used to discharge the gas in the buffer chamber in stages, thereby reducing water hammer.

[0057] Furthermore, in step S5, the closing pressure P of the air pressure reducing valve... 闭 The calculation formula is:

[0058] P 闭 =(P0-P1)*K5

[0059] Where k5 is the valve closing constant.

[0060] The advantage of adopting the above-mentioned further solution is that it avoids excessive gas discharge from the buffer chamber, which would aggravate the water hammer phenomenon. Attached Figure Description

[0061] Figure 1 This is a flowchart illustrating the steps of a specific embodiment of the present invention;

[0062] Figure 2 This is a schematic diagram of the installation of the buffer chamber and air pressure reducing valve of the present invention;

[0063] Figure 3 This is a schematic diagram of a simulation test for the present invention.

[0064] The attached diagram lists the components represented by each number as follows:

[0065] 1. Buffer chamber; 2. Buffer port; 3. Air pressure reducing valve; 4. Fluid receiving station; 5. Buffer device. Detailed Implementation

[0066] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0067] In the description of this invention, it should be understood that the terms "center," "length," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "inner," "outer," "circumferential," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0068] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0069] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0070] like Figure 1 As shown, since subsea pipelines mainly transport crude oil, which contains small amounts of seawater and natural gas forming a gas-liquid two-phase mixture, water hammer can easily occur during the transport of this mixed fluid when the fluid's motion state suddenly changes. Currently, there are few design methods for adding buffer chambers to subsea pipelines to cope with the water hammer effect. Therefore, those skilled in the art have developed a design method for preventing water hammer in subsea pipelines, mainly exploring the application of buffer devices in preventing water hammer in subsea pipelines, and providing a reference for designing buffer devices in subsea pipelines. The method includes the following steps:

[0071] S1. Calculate the average density based on the mixing ratio of oil, gas, and water in the pipeline. Specifically, the formula for calculating the average density of oil, water, and gas is as follows:

[0072]

[0073] Where, ρ 平 This is the average density, expressed in kg / m³. 3

[0074] ρ1 is the density of the oil at the bottom of the delivery pipe;

[0075] v1 is the unit volume of oil in the bottom of the delivery pipe;

[0076] ρ2 is the density of the water at the bottom of the conveying pipe;

[0077] v2 is the unit volume of water at the bottom of the conveying pipe;

[0078] ρ3 is the density of the gas at the bottom of the delivery pipe;

[0079] v3 is the unit volume of gas at the bottom of the delivery pipe.

[0080] Calculating the average density of the fluid is helpful for subsequent calculations of the buffer chamber volume and the diameter of the buffer inlet, ensuring timely adaptation and handling when the fluid's motion state changes.

[0081] S2. Calculate the pressure in the delivery pipeline where the buffer device needs to be installed and the pressure in the delivery pipeline at the fluid receiving station, and measure the delivery distance from the buffer device to the receiving station. Specifically, the formula for calculating the pressure P2 in the delivery pipeline at the fluid receiving station is as follows:

[0082] P2=ρ 平 *V 流 *k2

[0083] Wherein, P2 is the pressure inside the conveying pipeline at the fluid receiving station;

[0084] ρ 平 Average density;

[0085] V 流 The fluid velocity;

[0086] k2 is the medium constant.

[0087] Fluid receiving stations are typically crude oil storage tanks or crude oil transport ships.

[0088] The formula for calculating the pressure P1 in the conveying pipeline at the buffer device is as follows:

[0089] P1=P2+ρ 平 *g*L / J

[0090] Where L is the conveying distance from the buffer device to the receiving station;

[0091] J represents the slope.

[0092] Buffer devices are typically installed on the seabed near the delivery pump. They are mainly used to buffer the fluid and prevent water hammer from damaging the delivery pump and other auxiliary equipment.

[0093] S3. Calculate the volume of the buffer tank based on the pressures in step S2, the seawater pressure at the buffer device, the fluid flow rate in the delivery pipeline, and the delivery distance in step S2. Specifically, the formula for calculating the volume of the buffer tank is as follows:

[0094]

[0095] Among them, V仓 This refers to the volume of the buffer compartment;

[0096] P0 is the seawater pressure at the buffer device;

[0097] P1 is the pressure inside the delivery pipeline at the buffer device;

[0098] P2 is the pressure inside the pipeline at the fluid receiving station;

[0099] Q represents the fluid flow rate;

[0100] L is the conveying distance from the buffer device to the receiving station;

[0101] k1 is the medium constant.

[0102] During fluid transport, some gas will be released and enter the buffer chamber. When water hammer occurs and the fluid rapidly enters the buffer chamber, the gas in the buffer chamber is compressed, thus playing a buffering role.

[0103] S4. Calculate the diameter of the buffer inlet from the delivery pipeline to the buffer chamber based on the volume of the buffer chamber, the fluid inertial force, and the gas evolution rate obtained in step S3. Specifically, the formula for calculating the buffer inlet diameter R is as follows:

[0104]

[0105] υ t =ρ 平 *υ k *k3

[0106] Among them, υ 析 The gas evolution rate;

[0107] k3 is a characteristic constant;

[0108] υ k This refers to the velocity at which the fluid enters the buffer chamber.

[0109] S5. Calculate the opening pressure of the air pressure reducing valve at the top of the buffer chamber based on the pressure in the delivery pipeline at the buffer device in step S2. Specifically, the opening pressure P of the air pressure reducing valve... 启 The calculation formula is:

[0110] P 启 = (P0-P1)*K4

[0111] Where k4 is the valve opening constant.

[0112] The closing pressure P of the air pressure reducing valve 闭 The calculation formula is:

[0113] P 闭 =(P0-P1)*K5

[0114] Where k5 is the valve closing constant.

[0115] When too much fluid enters the buffer chamber from the delivery pipeline, causing the gas in the buffer chamber to be continuously compressed and exceed the opening pressure of the air pressure reducing valve, the air pressure reducing valve will gradually release the compressed gas in the buffer chamber to prevent excessive pressure from damaging the delivery pipeline or buffer chamber.

[0116] Example 1

[0117] like Figure 2 As shown, taking an offshore drilling platform located north of Beiwei Shoal in the Dongsha Islands at a water depth of approximately 120 to 175 meters as an example, to prevent water hammer in the pipelines used for crude oil extraction and transportation to crude oil tankers, a subsea pipeline water hammer prevention design method has been developed, which specifically includes the following steps:

[0118] S1. Calculate the average density based on the mixing ratio of oil, gas, and water in the pipeline. Specifically, the formula for calculating the average density of oil, water, and gas is as follows:

[0119]

[0120] Where, ρ 平 This is the average density, expressed in kg / m³. 3

[0121] ρ1 is the density of the oil at the bottom of the delivery pipe;

[0122] v1 is the unit volume of oil in the bottom of the delivery pipe;

[0123] ρ2 is the density of the water at the bottom of the conveying pipe;

[0124] v2 is the unit volume of water at the bottom of the conveying pipe;

[0125] ρ3 is the density of the gas at the bottom of the delivery pipe;

[0126] v3 is the unit volume of gas at the bottom of the delivery pipe.

[0127] In this embodiment, based on the analysis of crude oil samples, the content of natural gas in the crude oil is approximately 0.2%, the seawater content is 1.3%, and the crude oil contains 98.5% natural gas. The density of the natural gas in the sample analysis is 0.71 kg / m³. 3 Seawater density is 1050 kg / m³ 3 The density of crude oil is 875 kg / m³. 3 The average density of the fluid, calculated using the above formula, is 875.52 kg / m³. 3 .

[0128] S2. Calculate the pressure in the conveying pipeline at the location where the buffer device 5 needs to be installed and the pressure in the conveying pipeline at the fluid receiving station 4, and measure the conveying distance from the buffer device 5 to the fluid receiving station 4. Specifically, the formula for calculating the pressure P2 in the conveying pipeline at the fluid receiving station 4 is as follows:

[0129] P2=ρ 平 *V 流 *k2

[0130] Wherein, P2 is the pressure inside the conveying pipeline at the fluid receiving station;

[0131] ρ 平 Average density;

[0132] V 流 The fluid velocity;

[0133] k2 is the medium constant.

[0134] Fluid receiving station 4 is generally a crude oil storage tank or a crude oil transport ship.

[0135] The formula for calculating the pressure P1 in the conveying pipeline at the 5th location of the buffer device is as follows:

[0136] P1=P2+ρ 平 *g*L / J

[0137] Where L is the conveying distance from the buffer device 5 to the fluid receiving station 4;

[0138] J represents the slope.

[0139] The buffer device 5 is generally installed on the seabed and close to the delivery pump. It is mainly used to buffer the fluid and prevent water hammer from damaging the delivery pump and other auxiliary equipment.

[0140] In this embodiment, the fluid velocity is 2.5 m / s, the value of k2 is 0.1, the slope is 60°, the length of the conveying distance is 175 m, the pressure P2 of the conveying pipeline at the fluid receiving station is 0.2 MPa, and the pressure P1 of the conveying pipeline at the buffer device 5 is 1.5 MPa.

[0141] S3. Calculate the volume of buffer tank 1 based on the pressures in step S2, the seawater pressure at buffer device 5, the fluid flow rate in the conveying pipeline, and the conveying distance in step S2. Specifically, the formula for calculating the volume of buffer tank 1 is as follows:

[0142]

[0143] Among them, V 仓 Let this be the volume of buffer chamber 1;

[0144] P0 is the seawater pressure at buffer device 5;

[0145] P1 represents the pressure inside the conveying pipe at point 5 of the buffer device;

[0146] P2 is the pressure inside the four conveying pipelines at the fluid receiving station;

[0147] Q represents the fluid flow rate;

[0148] L is the conveying distance from buffer device 5 to receiving station 4;

[0149] k1 is the medium constant.

[0150] In this embodiment, the fluid velocity is 2.5 m / s, k1 is 0.01, the conveying distance is 175 m, the pressure P2 in the conveying pipeline at fluid receiving station 4 is 0.2 MPa, the pressure P1 in the conveying pipeline at buffer device 5 is 1.5 MPa, and the conveying flow rate is 3.5 m³ / s. 3 The seawater pressure P0 at the buffer device is 1.75 MPa per hour, and the calculated volume of buffer chamber 1 is 8.24 m³. 3 Since the required buffer chamber 1 has a large volume, the specific design of the buffer chamber 1 may involve 2 to 3 buffer chambers 1.

[0151] S4. Calculate the diameter of the buffer inlet 2 from the delivery pipeline to the buffer chamber 1 based on the volume of buffer chamber 1, fluid inertial force, and gas evolution rate obtained in step S3. Specifically, the formula for calculating the diameter R of the buffer inlet 2 is as follows:

[0152]

[0153] υ t =ρ 平 *υ k *k3

[0154] Among them, υ 析 The gas evolution rate;

[0155] k3 is a characteristic constant;

[0156] υ k This refers to the velocity at which the fluid enters the buffer chamber.

[0157] In this embodiment, υ k It is 1.5 m / s, υ 析 It is 0.0002m 3 / h, k3 is 650, and the buffer port diameter R is calculated to be approximately 0.5m according to the above formula.

[0158] S5. Calculate the opening pressure of the air pressure reducing valve 3 at the top of the buffer chamber 1 based on the pressure in the conveying pipe at the buffer device 5 in step S2. Specifically, the opening pressure P of the air pressure reducing valve 3 is... 启 The calculation formula is:

[0159] P 启 = (P0-P1)*K4

[0160] Where k4 is the valve opening constant.

[0161] The closing pressure P of air pressure reducing valve 3 闭 The calculation formula is:

[0162] P 闭 =(P0-P1)*K5

[0163] Where k5 is the valve closing constant.

[0164] In this embodiment, k4 is 10 and k5 is 8. According to the above formula, the valve opening pressure is 2.5MPa and the valve closing pressure is 2MPa.

[0165] like Figure 3 As shown, with time as the horizontal axis (in seconds) and the vibration amplitude of the conveying pipeline as the vertical axis (in 0.1 mm), the maximum amplitude of the conveying pipeline after the water hammer effect occurs is 7 cm, and it returns to normal in about 60 seconds. Therefore, adding a buffer chamber to the conveying pipeline to alleviate the water hammer effect has a positive effect.

[0166] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0167] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for designing waterproof hammers for subsea pipelines, characterized in that, Includes the following steps: S1. Calculate the average density based on the mixing ratio of oil, gas and water in the pipeline; S2. Calculate the pressure in the conveying pipeline where the buffer device needs to be installed and the pressure in the conveying pipeline at the fluid receiving station, and measure the conveying distance from the buffer device to the receiving station; S3. Calculate the volume of the buffer chamber based on the pressures in step S2, the seawater pressure at the buffer device, the fluid flow rate in the conveying pipeline, and the conveying distance in step S2. S4. Calculate the diameter of the buffer inlet from the delivery pipeline to the buffer chamber based on the volume of the buffer chamber, the fluid inertial force, and the gas evolution rate in step S3. S5. Calculate the opening pressure of the air pressure reducing valve at the top of the buffer chamber based on the pressure in the conveying pipeline at the buffer device in step S2. In step S2, the formula for calculating the volume of the buffer chamber is: ； in, V 仓 This refers to the volume of the buffer compartment; P 0 represents the seawater pressure at the buffer device; P 1 represents the pressure inside the delivery pipeline at the buffer device; P 2 represents the pressure inside the pipeline at the fluid receiving station; Q For fluid flow rate; L The conveying distance from the buffer device to the receiving station; k 1 is the dielectric constant; In step S1, the formula for calculating the average density of oil, water, and gas is as follows: ； in, ρ 平 This is the average density, expressed in kg / m³. 3 ρ 1 represents the density of the oil at the bottom of the delivery pipe; v 1 represents the unit volume of oil at the bottom of the delivery pipe; ρ 2 represents the density of the water at the bottom of the conveying pipe; v 2 represents the unit volume of water at the bottom of the conveying pipe; ρ 3 represents the density of the gas at the bottom of the delivery pipe; v 3 represents the unit volume of gas at the bottom of the delivery pipe; In step S2, the pressure of the conveying pipeline at the fluid receiving station P 2. The calculation formula is as follows ； in, ρ 平 Average density; V 流 The fluid velocity; k 2 is the dielectric constant; In step S2, the pressure in the conveying pipe at the buffer device P 1. The calculation formula is: ； in, L The conveying distance from the buffer device to the receiving station; J Slope; In step S4, the diameter of the buffer opening R The calculation formula is: ； ； in, υ 析 The gas evolution rate; k 3 is the characteristic constant; υ k The velocity at which the fluid enters the buffer chamber; In step S5, the opening pressure of the air pressure reducing valve... P 启 The calculation formula is: ； in, k 4 represents the valve opening constant; In step S5, the closing pressure of the air pressure reducing valve... P 闭 The calculation formula is: ； in, k 5 is the valve closing constant.

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