A method for monitoring leaks in a gathering pipeline

Abstract

This invention discloses a leakage monitoring method for gathering and transportation pipelines, relating to the field of pipeline safety monitoring technology. The method includes the following steps: S1, performing integration processing based on the rheological characteristics of the fluid within the gathering and transportation pipeline to obtain the theoretical flow rate of the cross-section; S2, using the ultrasonic signal received by the gathering and transportation pipeline, performing inversion to obtain the radial true flow velocity, and performing integration processing to obtain the actual flow rate of the cross-section; S3, determining whether the theoretical flow rate and the actual flow rate of the cross-section meet the deviation condition. If they do, a leak has occurred in the gathering and transportation pipeline; otherwise, no leak has occurred. This invention employs a two-term coupling of ultrasonic pressure radial gradient and pressure time partial derivative to construct a radial true flow velocity inversion, identifying weak velocity and flow rate changes caused by minor leaks, thereby improving detection sensitivity.

Description

Technical Field

[0001] This invention relates to the field of pipeline safety monitoring technology, specifically to a method for monitoring leaks in gathering and transportation pipelines. Background Technology

[0002] Gathering and transportation pipelines are core equipment in the extraction, gathering, transportation, and storage of oil and gas. They undertake the long-distance, continuous transportation of crude oil, heavy oil, and oil-gas mixtures, and are widely laid in deserts, swamps, buried areas, and near-shore areas, serving as the lifeblood of energy gathering and transportation systems. Due to the complex operating conditions of high-pressure transportation, soil corrosion, geological subsidence, external disturbances, and media erosion, pipelines are highly susceptible to media leakage accidents caused by pipe wall corrosion perforation, weld cracking, and third-party damage. Leaks not only result in the significant loss of energy resources such as crude oil and natural gas but also cause ecological damage such as soil and water pollution. In severe cases, they can lead to major safety accidents such as fires and explosions, threatening the lives and property of on-site maintenance personnel. Therefore, continuous, accurate, and stable leakage monitoring of gathering and transportation pipelines is a core element in ensuring the safe operation of energy gathering and transportation systems.

[0003] Currently, leakage monitoring technologies for gathering and transportation pipelines are mainly divided into several categories: flow balance method, pressure wave analysis method, traditional ultrasonic time-of-flight method, fiber optic sensing monitoring method, and infrared imaging monitoring method. All of these methods have significant technical shortcomings in practical engineering applications and cannot meet the high-precision monitoring requirements under complex operating conditions. Firstly, the flow balance method and pressure wave method rely on fixed thresholds for judgment, identifying leaks only through the difference in inlet and outlet flow rates and the amplitude of pressure fluctuations in the pipeline section. They do not consider the rheological characteristics of non-Newtonian fluids such as crude oil and heavy oil in the gathering and transportation pipeline, and cannot eliminate the interference from operating condition fluctuations caused by medium temperature, pressure, and flow rate scheduling. Small leakage signals are easily masked by operating condition fluctuations, resulting in high false alarm rates and frequent missed detections. Furthermore, these methods can only determine that a leak has occurred, but cannot achieve accurate quantification of the leak, making them extremely unsuitable for various applications. Secondly, traditional ultrasonic time-of-flight and Doppler ultrasonic methods are extremely sensitive to two-phase media. In gathering and transportation pipelines, there are often oil and gas mixed transportation conditions. Gas bubbles will cause ultrasonic signal scattering and attenuation, resulting in distortion of flow velocity measurement and a significant increase in flow rate calculation error. Therefore, they cannot be applied to the transportation of oil and gas mixed media with fluctuating gas content. Summary of the Invention

[0004] To address the above problems, this invention proposes a leakage monitoring method for gathering and transportation pipelines.

[0005] The technical solution of this invention is: a leakage monitoring method for gathering and transportation pipelines, comprising the following steps: S1. Based on the rheological characteristics of the fluid in the gathering and transportation pipeline, perform integral processing to obtain the theoretical flow rate of the cross section; S2. Using the ultrasonic signals received by the gathering and transportation pipeline, the radial true flow velocity is obtained by inversion, and then integrated to obtain the actual cross-sectional flow rate. S3. Determine whether the theoretical flow rate and the actual flow rate of the cross-section meet the deviation condition. If they do, the gathering and transportation pipeline is leaking; otherwise, no leak has occurred.

[0006] Furthermore, S1 includes the following sub-steps: S11. Construct constitutive relation functions based on the shear stress of the gathering and transportation pipeline; S12. Integrate the constitutive function from the radial position to the pipe wall to obtain the cumulative velocity distribution at the radial position; S13. Based on the cumulative velocity distribution at the radial position, the area integral of the gathering and transportation pipeline is performed to obtain the theoretical flow rate of the cross section.

[0007] The beneficial effects of the above-mentioned further scheme are as follows: In this invention, the gathering and transportation pipeline is a circular straight pipe structure, and the fluid flow inside the pipe is a typical laminar flow in a circular pipe. The driving force of the fluid flow is provided by the pipe wall and radial shear stress. By adopting the principle of laminar flow integration in circular pipes, the local shear rate is integrated radially to obtain the spatial velocity distribution. Then, by integrating the cross-sectional area of ​​the circular pipe, the theoretical cross-sectional flow rate driven by pure rheology without leakage can be calculated. This flow rate is determined only by the pipe geometry and the rheological properties of the medium, and is not affected by external vibration, gas content, or ambient temperature. It serves as the benchmark for leakage monitoring of the gathering and transportation pipeline.

[0008] Furthermore, in S12, the cumulative velocity distribution at the radial position... The expression is: ; ; in, The constitutive relation function representing the fluid within the gathering and transportation pipeline. Indicates the radial position of the gathering and transportation pipeline. The shear stress experienced by the fluid element at that point. Indicates the radial distance from the pipe wall. Indicates flow rate.

[0009] The beneficial effect of the above-mentioned further solution is that, in the present invention, at the radial position of the circular tube... At that point, the shear stress experienced by the fluid element is The rate of change of flow velocity along the radial direction (referred to as shear rate) and shear stress The relationship is determined by the rheological properties of the fluid, and can be written as a structural relationship function. The negative sign is due to the flow velocity. radial distance Increase and decrease, pipe center The flow velocity is highest at the pipe wall. The flow velocity is 0 at that point, therefore Negative, It is a positive shear rate. Radial position. The flow velocity at that point is equal to that from to the pipe wall Integrating the shear rate at all points between the points, since the shear rate is the rate of change of flow velocity, yields the cumulative value of the flow velocity. Theoretical flow rate at the cross-section. The expression is .

[0010] Furthermore, S2 includes the following sub-steps: S21. Use ultrasonic transmitting transducers and receiving transducers installed on the outer wall of the gathering and transportation pipeline to transmit ultrasonic signals into the inside of the gathering and transportation pipeline and collect ultrasonic pressure fields. S22. Calculate the equivalent density of the two-phase mixed medium; S23. Based on the ultrasonic pressure field and the equivalent density of the two-phase mixed medium, inversion is performed to obtain the true radial flow velocity; S24. Integrate the radial true velocity over the area to obtain the actual flow rate of the cross section.

[0011] The beneficial effects of the above-mentioned further solutions are as follows: In this invention, the gathering and transportation pipeline operates under the condition of mixed oil and gas transport. Traditional contact flowmeters will experience measurement distortion, blockage, and wear problems in gas-containing, high-viscosity media. Ultrasonic signals can penetrate the pipe wall of the gathering and transportation pipeline and the oil and gas mixed medium, realizing non-contact acoustic field signal acquisition. By acquiring the ultrasonic pressure field and combining it with the density of the two-phase medium, the radial true flow velocity obtained by this invention is not affected by the phase state of the medium. At the same time, the actual flow rate adopts the same cross-sectional integral form as the theoretical flow rate, ensuring the consistency of the calculation scope and integration dimension of the two flow rates. By acquiring the spatial pressure gradient and time pressure change by ultrasound, combined with the two-phase flow density correction, the true flow velocity is inverted, and the actual flow rate including leakage, two-phase flow, and disturbance is obtained by integration.

[0012] Furthermore, S22 includes the following sub-steps: S221. The sum of the mass of the oil phase medium and the mass of the gas phase medium in the gathering and transportation pipeline shall be taken as the total mass of the two-phase medium. S222. The ratio between the mass of the oil phase medium and the intrinsic density of the pure oil phase medium and the ratio between the mass of the gas phase medium and the intrinsic density of the natural gas phase medium are added together to obtain the total volume of the two phase media. S223. The ratio between the total mass of the two-phase medium and the total volume of the two-phase medium is taken as the equivalent density of the two-phase mixed medium.

[0013] The beneficial effects of the above-mentioned further scheme are as follows: In this invention, the medium transported by the gathering and transportation pipeline is a two-phase mixture of oil phase, continuous phase, and gas phase, and the density of the mixed medium is not the density of a single medium, but is determined by the weighted sum of the mass and volume of the oil phase and the gas phase. Therefore, this invention adopts a two-phase flow density calculation method, using the intrinsic density and mass of the oil phase and the gas phase as basic parameters, to calculate the equivalent density of the real mixed medium in the gathering and transportation pipeline, providing accurate medium physical parameters for subsequent ultrasonic sound field inversion of flow velocity.

[0014] Furthermore, in S23, the radial true flow velocity The expression is: ; in, This represents the equivalent density of a two-phase mixed medium. Represents the ultrasonic pressure field Spatial gradient operator, This represents the reference sound velocity in a pure oil phase medium. Indicates the ultrasonic excitation time. Indicates radial position, This indicates the distance from the radial position to the pipe wall.

[0015] The beneficial effects of the above-mentioned further solutions are as follows: In this invention, when a leak occurs in the gathering and transportation pipeline, both steady-state spatial pressure distribution distortion and transient temporal pressure fluctuations will occur simultaneously. A single spatial or temporal signal cannot accurately capture minute leaks; therefore, the ultrasonic pressure radial gradient term of this invention... Reflects the steady-state spatial distribution of pressure within the pipeline and the basic flow state for normal transport in the gathering and transportation pipeline; ultrasonic pressure time partial derivative term It reflects the transient pressure changes caused by leakage and media disturbance, and captures the non-steady-state signals of minor leaks in the gathering and transportation pipeline; the two are coupled by order correction of sound velocity, and the inverted flow velocity closely matches the actual flow state of the gathering and transportation pipeline.

[0016] It is the ultrasonic pressure gradient and the first-order correction of the sound velocity, corresponding to the fluid momentum convection term, and the flow velocity is driven by the ultrasonic spatial field. The corresponding spatial position change indicates the rate of pressure change at different locations in the pipe, describing the spatial distribution pattern of the ultrasonic field, which is a steady-state distribution characteristic.

[0017] kg / (m 2 ·s 2 ). m 3 / kg. Therefore, the unit of the first term is [m / s].

[0018] It is the time-varying rate of ultrasonic pressure and the second-order correction of sound velocity, corresponding to the fluid wave propagation term. Corresponding to transient changes in time, the rate of pressure change at the same location at different times describes the transient fluctuations of the ultrasonic field, which is a dynamic change characteristic.

[0019] , m / s. kg / (m·s) 3 Therefore, the unit of the second term is [m / s].

[0020] Furthermore, in S3, the deviation condition is specifically as follows: ,in, Indicates the actual flow rate at the cross-section. Indicates the theoretical flow rate of the cross-section. This indicates the set relative deviation rate of the flow rate.

[0021] The beneficial effects of this invention are: (1) The present invention constructs a rheological constitutive relationship based on the shear stress of the medium in the gathering and transportation pipeline, and obtains the theoretical flow velocity distribution through radial integration. It is compatible with the rheological characteristics of various crude oil and heavy oil media. At the same time, by correcting the equivalent density of the oil-gas two-phase mixed medium, it eliminates the attenuation and scattering interference of gas phase bubbles on the ultrasonic signal, perfectly adapting to the complex medium working conditions of oil and gas mixed transportation and gas content fluctuation in gathering and transportation pipelines. Its applicable scope covers various gathering and transportation pipelines on land, buried, and over long distances.

[0022] (2) The present invention uses the dual coupling of ultrasonic pressure radial gradient and pressure time partial derivative to construct radial true flow velocity inversion, identify weak flow velocity and weak flow rate changes caused by micro-leakage, and improve detection sensitivity. Attached Figure Description

[0023] Figure 1 This is a flowchart of a leakage monitoring method for gathering and transportation pipelines. Detailed Implementation

[0024] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0025] like Figure 1 As shown, the present invention provides a leakage monitoring method for gathering and transportation pipelines, comprising the following steps: S1. Based on the rheological characteristics of the fluid in the gathering and transportation pipeline, perform integral processing to obtain the theoretical flow rate of the cross section; S2. Using the ultrasonic signals received by the gathering and transportation pipeline, the radial true flow velocity is obtained by inversion, and then integrated to obtain the actual cross-sectional flow rate. S3. Determine whether the theoretical flow rate and the actual flow rate of the cross-section meet the deviation condition. If they do, the gathering and transportation pipeline is leaking; otherwise, no leak has occurred.

[0026] In this embodiment of the invention, S1 includes the following sub-steps: S11. Construct constitutive relation functions based on the shear stress of the gathering and transportation pipeline; S12. Integrate the constitutive function from the radial position to the pipe wall to obtain the cumulative velocity distribution at the radial position; S13. Based on the cumulative velocity distribution at the radial position, the area integral of the gathering and transportation pipeline is performed to obtain the theoretical flow rate of the cross section.

[0027] In this invention, the gathering and transportation pipeline is a circular straight pipe structure, and the fluid flow inside the pipe is a typical laminar flow in a circular pipe. The driving force of the fluid flow is provided by the pipe wall and radial shear stress. Using the principle of laminar flow integration in circular pipes, the local shear rate is integrated radially to obtain the spatial velocity distribution. Then, through cross-sectional integration of the circular pipe, the theoretical cross-sectional flow rate driven purely by rheology and without leakage can be calculated. This flow rate is determined only by the pipe geometry and the rheological properties of the medium, and is not affected by external vibration, gas content, or ambient temperature. It serves as the benchmark for leakage monitoring of the gathering and transportation pipeline.

[0028] In this embodiment of the invention, in S12, the cumulative velocity distribution at the radial position... The expression is: ; ; in, The constitutive relation function representing the fluid within the gathering and transportation pipeline. Indicates the radial position of the gathering and transportation pipeline. The shear stress experienced by the fluid element at that point. Indicates the radial distance from the pipe wall. Indicates flow rate.

[0029] In this invention, at the radial position of the circular tube At that point, the shear stress experienced by the fluid element is The rate of change of flow velocity along the radial direction (referred to as shear rate) and shear stress The relationship is determined by the rheological properties of the fluid, and can be written as a structural relationship function. The negative sign is due to the flow velocity. radial distance Increase and decrease, pipe center The flow velocity is highest at the pipe wall. The flow velocity is 0 at that point, therefore Negative, It is a positive shear rate. Radial position. The flow velocity at that point is equal to that from to the pipe wall Integrating the shear rate at all points between the points, since the shear rate is the rate of change of flow velocity, yields the cumulative value of the flow velocity. Theoretical flow rate at the cross-section. The expression is .

[0030] In this embodiment of the invention, S2 includes the following sub-steps: S21. Use ultrasonic transmitting transducers and receiving transducers installed on the outer wall of the gathering and transportation pipeline to transmit ultrasonic signals into the inside of the gathering and transportation pipeline and collect ultrasonic pressure fields. S22. Calculate the equivalent density of the two-phase mixed medium; S23. Based on the ultrasonic pressure field and the equivalent density of the two-phase mixed medium, inversion is performed to obtain the true radial flow velocity; S24. Integrate the radial true velocity over the area to obtain the actual flow rate of the cross section.

[0031] In this invention, the gathering and transportation pipeline operates under two-phase mixed oil and gas conditions. Traditional contact flowmeters suffer from measurement distortion, blockage, and wear problems in gas-containing, high-viscosity media. Ultrasonic signals can penetrate the pipeline wall and mix with the oil and gas medium, enabling non-contact acoustic signal acquisition. By combining the acquired ultrasonic pressure field with the two-phase medium density, the radial true flow velocity obtained by this invention is unaffected by the medium's phase state. Furthermore, the actual flow rate uses the same cross-sectional integral form as the theoretical flow rate, ensuring consistency in the calculation scope and integration dimension for both flow rates. By acquiring spatial pressure gradients and temporal pressure changes using ultrasound, combined with two-phase flow density correction, the true flow velocity is inverted, and the actual flow rate, including leakage, two-phase flow, and disturbances, is obtained through integration.

[0032] In this embodiment of the invention, S22 includes the following sub-steps: S221. The sum of the mass of the oil phase medium and the mass of the gas phase medium in the gathering and transportation pipeline shall be taken as the total mass of the two-phase medium. S222. The ratio between the mass of the oil phase medium and the intrinsic density of the pure oil phase medium and the ratio between the mass of the gas phase medium and the intrinsic density of the natural gas phase medium are added together to obtain the total volume of the two phase media. S223. The ratio between the total mass of the two-phase medium and the total volume of the two-phase medium is taken as the equivalent density of the two-phase mixed medium.

[0033] In this invention, the medium transported by the gathering and transportation pipeline is a two-phase mixture of oil phase, continuous phase, and gas phase, and dispersed phase. The density of the mixed medium is not the density of a single medium, but is determined by the weighted sum of the mass and volume of the oil phase and the gas phase. Therefore, this invention adopts a two-phase flow density calculation method, using the intrinsic density and mass of the oil phase and the gas phase as basic parameters, to calculate the equivalent density of the real mixed medium in the gathering and transportation pipeline, providing accurate medium physical parameters for subsequent ultrasonic sound field inversion of flow velocity.

[0034] In this embodiment of the invention, in S23, the radial true flow velocity... The expression is: ; in, This represents the equivalent density of a two-phase mixed medium. Represents the ultrasonic pressure field Spatial gradient operator, This represents the reference sound velocity in a pure oil phase medium. Indicates the ultrasonic excitation time. Indicates radial position, This indicates the distance from the radial position to the pipe wall.

[0035] In this invention, when a leak occurs in the gathering and transportation pipeline, both steady-state spatial pressure distribution distortion and transient temporal pressure fluctuations are generated simultaneously. A single spatial or temporal signal cannot accurately capture minute leaks; therefore, the ultrasonic pressure radial gradient term in this invention... Reflects the steady-state spatial distribution of pressure within the pipeline and the basic flow state for normal transport in the gathering and transportation pipeline; ultrasonic pressure time partial derivative term It reflects the transient pressure changes caused by leakage and media disturbance, and captures the non-steady-state signals of minor leaks in the gathering and transportation pipeline; the two are coupled by order correction of sound velocity, and the inverted flow velocity closely matches the actual flow state of the gathering and transportation pipeline.

[0036] It is the ultrasonic pressure gradient and the first-order correction of the sound velocity, corresponding to the fluid momentum convection term, and the flow velocity is driven by the ultrasonic spatial field. The corresponding spatial position change indicates the rate of pressure change at different locations in the pipe, describing the spatial distribution pattern of the ultrasonic field, which is a steady-state distribution characteristic.

[0037] kg / (m 2 ·s 2 ). m 3 / kg. Therefore, the unit of the first term is [m / s].

[0038] It is the time-varying rate of ultrasonic pressure and the second-order correction of sound velocity, corresponding to the fluid wave propagation term. Corresponding to transient changes in time, the rate of pressure change at the same location at different times describes the transient fluctuations of the ultrasonic field, which is a dynamic change characteristic.

[0039] , m / s. kg / (m·s) 3 Therefore, the unit of the second term is [m / s].

[0040] In this embodiment of the invention, in S3, the deviation condition is specifically as follows: ,in, Indicates the actual flow rate at the cross-section. Indicates the theoretical flow rate of the cross-section. This indicates the set relative deviation rate of the flow rate.

[0041] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method of monitoring a leak in a gathering pipeline, the method comprising: Includes the following steps: S1. Based on the rheological characteristics of the fluid in the gathering and transportation pipeline, perform integral processing to obtain the theoretical flow rate of the cross section; S2. Using the ultrasonic signals received by the gathering and transportation pipeline, the radial true flow velocity is obtained by inversion, and then integrated to obtain the actual cross-sectional flow rate. S3. Determine whether the theoretical flow rate and the actual flow rate of the cross-section meet the deviation condition. If they do, the gathering and transportation pipeline is leaking; otherwise, no leak has occurred.

2. The method of leak monitoring of a gathering pipeline as claimed in claim 1, wherein, S1 includes the following sub-steps: S11. Construct constitutive relation functions based on the shear stress of the gathering and transportation pipeline; S12. Integrate the constitutive function from the radial position to the pipe wall to obtain the cumulative velocity distribution at the radial position; S13. Based on the cumulative velocity distribution at the radial position, the area integral of the gathering and transportation pipeline is performed to obtain the theoretical flow rate of the cross section.

3. The leakage monitoring method for gathering and transportation pipelines according to claim 2, characterized in that, In the S12, the cumulative distribution of the flow rate at the radial position The expression is: ； ； wherein, represents a constitutive relation function of the fluid in the gathering pipeline, represents the shear stress experienced by a fluid element at a radial position in the gathering pipeline, represents the distance from the radial position to the pipe wall, represents the flow velocity.

4. The leakage monitoring method for gathering and transportation pipelines according to claim 1, characterized in that, S2 includes the following sub-steps: S21. Use ultrasonic transmitting transducers and receiving transducers installed on the outer wall of the gathering and transportation pipeline to transmit ultrasonic signals into the inside of the gathering and transportation pipeline and collect ultrasonic pressure fields. S22. Calculate the equivalent density of the two-phase mixed medium; S23. Based on the ultrasonic pressure field and the equivalent density of the two-phase mixed medium, inversion is performed to obtain the true radial flow velocity; S24. Integrate the radial true velocity over the area to obtain the actual flow rate of the cross section.

5. The leakage monitoring method for gathering and transportation pipelines according to claim 4, characterized in that, S22 includes the following sub-steps: S221. The sum of the mass of the oil phase medium and the mass of the gas phase medium in the gathering and transportation pipeline shall be taken as the total mass of the two-phase medium. S222. The ratio between the mass of the oil phase medium and the intrinsic density of the pure oil phase medium and the ratio between the mass of the gas phase medium and the intrinsic density of the natural gas phase medium are added together to obtain the total volume of the two phase media. S223. The ratio between the total mass of the two-phase medium and the total volume of the two-phase medium is taken as the equivalent density of the two-phase mixed medium.

6. The leakage monitoring method for gathering and transportation pipelines according to claim 4, characterized in that, In S23, the radial true flow velocity The expression is: ； in, This represents the equivalent density of a two-phase mixed medium. Indicates ultrasonic pressure field Spatial gradient operator, This represents the reference sound velocity in a pure oil phase medium. Indicates the ultrasonic excitation time. Indicates radial position, This indicates the distance from the radial position to the pipe wall.

7. The leakage monitoring method for gathering and transportation pipelines according to claim 1, characterized in that, In S3, the deviation condition is specifically as follows: ,in, Indicates the actual flow rate at the cross-section. Indicates the theoretical flow rate of the cross-section. This indicates the set relative deviation rate of the flow rate.

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