Method for detecting blockage in a subsea natural gas pipeline based on pressure gradient

Abstract

The present application relates to a kind of submarine natural gas pipeline blockage discrimination methods based on pressure gradient, comprising the following steps: collecting the parameters of submarine gas pipeline;The pressure gradient line equation before and after submarine gas pipeline blockage is combined and operated, and the calculation model for discriminating the blockage degree and blockage position of submarine gas pipeline is obtained;In the calculation model, the start pressure and end pressure of submarine gas pipeline in unblocked state are selected from the parameters, and the start pressure and end pressure of submarine gas pipeline under the current condition to be judged are input, and the blockage degree factor is calculated;Judge whether the blockage degree factor value is greater than a certain value;When less than the certain value, it is considered that pipeline does not occur blockage, when greater than or equal to the certain value, it is considered that pipeline will have blockage;In the calculation model, the total length of pipeline is input, and the position of blockage occurring on pipeline is calculated.

Description

Technical Field

[0001] This invention relates to a method for identifying blockages in subsea natural gas pipelines based on pressure gradient, belonging to the field of marine natural gas development technology. Background Technology

[0002] Subsea pipelines play a crucial role in the development and transportation of offshore oil and gas resources. During operation, subsea natural gas pipelines are prone to blockages due to changes in operating conditions and the composition of the transported fluid. For example, if the transported natural gas contains water, hydrates can easily form under the high pressure and low temperature conditions inside the subsea pipeline, causing blockages. Pipeline blockages not only increase the risks of oil and gas extraction, severely impacting production and causing huge economic losses, but also threaten personnel safety. Therefore, the ability to identify and mitigate pipeline blockages is of great significance for the timely detection and mitigation of operational risks, ensuring pipeline flow safety, and maintaining energy security.

[0003] Common methods for identifying pipeline blockages include: (1) Pressure wave method, which involves artificially creating pressure waves within the pipeline, collecting and analyzing the rebound pressure wave response signals to obtain pipeline blockage information. The disadvantage of this method is that it requires pausing pipeline operation and has low positioning accuracy. (2) Acoustic wave method, which uses the acoustic response signals obtained by sound waves reflecting off obstacles in the pipeline to determine blockages. The disadvantage of this method is that it is easily affected by environmental noise, the blockage signal features are difficult to extract, and the sound waves attenuate quickly, making it unsuitable for long-distance pipelines.

[0004] One existing technology proposes a pipe blockage acoustic signature recognition model based on refined composite multi-scale scattering entropy and a Gaussian mixture hidden Markov model. It extracts and identifies the acoustic pressure signal using a single-parameter dual-threshold endpoint detection algorithm, applying acoustic signature recognition principles to pipe acoustic pressure signal processing. This method is currently in the experimental stage, and no engineering applications have been observed.

[0005] A second existing technology proposes a blockage identification method based on component signal feature extraction using local mean decomposition combined with support vector machines. However, this method is still immature, the identification indicators used are not obvious enough, and the identification accuracy is not high.

[0006] Blockage monitoring and identification of onshore gas pipelines can be achieved through methods such as deploying multiple sensors along the pipeline and manual inspections, making the identification and location of blockages relatively easy. However, due to limitations such as the seabed environment and technology, monitoring and sensors for subsea gas pipelines are concentrated at the wellhead and platform (the pipeline's inlet and outlet), and sensors are generally not installed along the pipeline route. Manual inspections are also difficult to implement. Therefore, the identification of blockages in subsea natural gas pipelines is unique and challenging. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for identifying blockages in subsea natural gas pipelines based on pressure gradient. This method combines and mathematically calculates the pressure gradient equations before and after a blockage in the subsea gas pipeline to obtain a computational model for determining the degree and location of the blockage. This method is applicable to identifying blockages in long-distance subsea gas pipelines and offers advantages such as simple calculation, rapid location, strong versatility, and no need to halt production.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for detecting blockages in subsea natural gas pipelines based on pressure gradient includes the following steps:

[0010] Collect various parameters of the subsea gas pipeline;

[0011] By combining and calculating the pressure gradient equations before and after blockage of the subsea gas pipeline, a calculation model is obtained to determine the degree and location of blockage in the subsea gas pipeline.

[0012] In the calculation model, the starting pressure and ending pressure of the subsea gas pipeline under the unblocked state and the starting pressure and ending pressure of the subsea gas pipeline under the current condition to be judged are selected from various parameters to calculate the blockage degree factor.

[0013] The system determines whether the blockage level factor value is greater than a certain threshold. If the value is less than the threshold, the pipeline is considered to be unblocked; if the value is greater than or equal to the threshold, the pipeline is considered to be about to become blocked.

[0014] In the computational model, the total length of the pipeline is input, and the location of the blockage in the pipeline is calculated.

[0015] The aforementioned method for detecting blockages in subsea natural gas pipelines based on pressure gradient is preferably based on the following assumptions in establishing its calculation model:

[0016] Assuming the natural gas transported by the subsea gas pipeline has a volumetric water content of no more than 5%, and the flow pattern in the pipeline is annular mist flow;

[0017] Assume that the pressure drop of the subsea gas pipeline is equal to its friction drop, and ignore the pipeline elevation difference and local pressure drop caused by pipe fittings;

[0018] Assume that the volumetric flow rate of the medium remains constant during the process of incomplete blockage in the subsea gas pipeline.

[0019] The aforementioned method for identifying blockages in subsea natural gas pipelines based on pressure gradient preferably uses the following formula to calculate the blockage severity factor:

[0020]

[0021] In the formula, p Q p Z These represent the starting and ending pressures of the subsea pipeline in its unblocked state; p DQ p DZ These are the starting pressure and ending pressure of the subsea pipeline under the current conditions to be determined.

[0022] The aforementioned method for identifying blockages in subsea natural gas pipelines based on pressure gradient preferably calculates the location x of the blockage on the pipeline. L The specific formula is as follows:

[0023]

[0024] In the formula, L is the total length of the pipeline.

[0025] The aforementioned method for determining blockage in subsea natural gas pipelines based on pressure gradient preferably involves determining whether the blockage degree factor value is greater than 1.2; when the value is less than 1.2, the pipeline is considered not to be blocked, and when the value is greater than or equal to 1.2, the pipeline is considered to be about to be blocked.

[0026] A second aspect of the present invention provides a device for detecting blockages in subsea natural gas pipelines based on pressure gradient, comprising:

[0027] The first processing unit is used to collect various parameters of the subsea gas pipeline;

[0028] The second processing unit is used to combine and calculate the pressure gradient equations before and after the blockage of the subsea gas pipeline, and obtain a calculation model to determine the degree and location of the blockage of the subsea gas pipeline.

[0029] The third processing unit is used to select the starting pressure and ending pressure of the subsea gas pipeline under the unblocked state and the starting pressure and ending pressure of the subsea gas pipeline under the current judgment condition from various parameters in the calculation model, and calculate the blockage degree factor.

[0030] The fourth processing unit is used to determine whether the blockage degree factor value is greater than a certain value; when it is less than the certain value, it is considered that the pipeline is not blocked, and when it is greater than or equal to the certain value, it is considered that the pipeline is about to be blocked.

[0031] The fifth processing unit is used to input the total length of the pipeline into the calculation model and calculate the location of the blockage in the pipeline.

[0032] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described method for determining blockages in subsea natural gas pipelines based on pressure gradient.

[0033] A fourth aspect of the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method for determining blockage of subsea natural gas pipelines based on pressure gradient.

[0034] The present invention has the following advantages due to the adoption of the above technical solutions:

[0035] 1. The discrimination method of the present invention obtains a calculation model for judging the degree and location of blockage of the subsea gas pipeline by combining and mathematically calculating the pressure gradient equations before and after the blockage of the subsea gas pipeline, and then judges the location of the blockage by the calculation model.

[0036] 2. The discrimination method of the present invention requires fewer calculation parameters for the discrimination of blockage in subsea natural gas pipelines, and the calculation is simple. This helps on-site operators to make a faster and more accurate prediction of pipeline blockage, thereby improving the safety and efficiency of pipeline operation.

[0037] 3. This invention can detect blockages in subsea natural gas pipelines using existing pipeline equipment at the pipeline inlet and outlet, without requiring additional detection equipment. The detection method is applicable to the detection of blockages in long-distance subsea gas pipelines and has advantages such as simple calculation, rapid location, strong versatility, and no need to stop production. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method for identifying blockages in subsea natural gas pipelines based on pressure gradient, provided in an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of the equivalent replacement of the blocked pipe segment provided in this embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of blockage location provided in this embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] To overcome the shortcomings of existing pipeline blockage detection methods, such as low positioning accuracy, difficulty in feature extraction, immature technology, and limited applicability to special subsea conditions, this invention proposes a pressure gradient-based method for detecting blockages in subsea natural gas pipelines. This method combines and mathematically calculates the pressure gradient equations before and after blockage in the subsea gas pipeline to obtain a computational model for determining the degree and location of blockage. This invention is applicable to the detection of blockages in long-distance subsea gas pipelines and offers advantages such as simple calculation, rapid positioning, strong versatility, and no need to halt production.

[0043] The technical solution of the present invention will be explained in detail below with reference to specific calculation processes and application examples.

[0044] This invention relates to a method for detecting blockages in subsea natural gas pipelines based on pressure gradient, characterized by the following steps:

[0045] Step 1: Collect various parameters of the subsea gas pipeline.

[0046] Step 2: Combine and calculate the pressure gradient equations before and after the blockage of the subsea gas pipeline to obtain a calculation model for judging the degree and location of the blockage.

[0047] The computational model is based on the following assumptions about the subsea gas pipeline:

[0048] Assumption 1: Assume that the volumetric water content of the natural gas transported by the subsea pipeline is no more than 5%, and the flow pattern in the pipeline is annular mist flow;

[0049] Assumption 2: It is assumed that the pressure drop of the subsea pipeline is equal to its friction drop, and the local pressure drop caused by the pipeline elevation difference and fittings is ignored;

[0050] Assumption 3: It is assumed that the volumetric flow rate of the medium remains constant during the process of incomplete blockage of the subsea pipeline.

[0051] Step 3: In the calculation model, select the starting pressure p of the subsea pipeline under unblocked conditions from the various parameters. Q Endpoint pressure p Z The starting pressure p of the subsea pipeline under the current conditions to be determined. DQ Endpoint pressure p DZ The congestion factor σ is calculated using the following formula:

[0052]

[0053] Step 4: Determine if the blockage factor value is greater than 1.2; if the value is less than 1.2, the pipeline is considered not to be blocked; if the value is greater than or equal to 1.2, the pipeline is considered to be about to be blocked.

[0054] Step 5: Input the total pipeline length L, and calculate the location x of the blockage in the pipeline according to the following formula. L .

[0055]

[0056] The calculation method of the present invention will be described in detail below with reference to its specific working principle.

[0057] For subsea gas pipelines, according to the classic Bernoulli equation, the pressure drop mainly consists of frictional losses along the pipeline, pressure differences caused by elevation differences, and local frictional losses caused by valves, bends, and other pipe fittings, as shown in the following equation:

[0058]

[0059] In the formula, dp is the pressure difference between the inlet and outlet of the micro-element pipe, ρ is the density of the fluid in the pipe at the current temperature and pressure, λ is the friction coefficient along the pipe, dx is the length of the micro-element pipe segment, D is the inner diameter of the pipe, w is the flow velocity of the fluid in the pipe, g is the acceleration due to gravity, ds is the elevation difference of the micro-element pipe segment, and dw is the flow velocity of the micro-element segment.

[0060] In this equation, the first term on the right side represents frictional resistance along the pipeline, the second term represents the pressure difference caused by the elevation difference, and the third term represents local frictional losses. The vertical elevation difference of subsea gas pipelines is generally less than 200m. Furthermore, the riser height connecting the subsea gas pipeline to the platform does not exceed 2000m. Due to the low gas density, the pressure difference caused by the elevation difference of the gas column in the riser is small (not exceeding 0.025MPa) and can be ignored. Subsea pipelines also have few bends, valves, and other fittings that cause local pressure drops; therefore, local pressure drops can be ignored, and the pressure drop of the gas pipeline can be approximated as equal to the frictional pressure drop along the pipeline.

[0061] The hydraulic gradient equation for pressure variation along the pipeline length is quite complex. To facilitate mathematical transformation and calculation, the pressure is squared. According to "Gas Transmission Pipeline Design and Management (Second Edition)," the pipeline characteristic equation for pressure distribution along the gas transmission pipeline is as follows:

[0062]

[0063] Where, p Q p is the initial pressure of the pipeline. Z Let L be the pressure at the pipeline endpoint, L be the total length of the pipeline, Q be the volumetric flow rate of the gas being transported, and the characteristic coefficient C be calculated using the following formula:

[0064]

[0065] Where λ is the friction coefficient along the pipeline, Z is the compressibility factor of the pipeline gas, Δ is the relative density of the pipeline gas, T is the temperature, C0 is an empirical constant with a value of 0.03843, and D is the inner diameter of the pipeline.

[0066] Deposits in gas pipelines can reduce the cross-sectional area for gas flow. In cases of incomplete blockage, it can be analogous to connecting a narrowed constrictor (smaller in diameter than the unblocked pipe) in series with the original pipeline. Figure 2 As shown. The characteristic equation of the gas pipeline at this point becomes:

[0067]

[0068] Where C1 is the pipe characteristic coefficient of the unblocked section, C2 is the pipe characteristic coefficient of the blocked section, and x is the length of the blocked section. For ease of subsequent mathematical calculations and derivations, the friction caused by the blockage can be equivalent to a longer pipe L' of the same diameter as the original pipe, i.e.:

[0069] C1(Lx)+C2x=CL' (5)

[0070] The degree of blockage in a pipeline refers to the ratio of the cross-sectional area of ​​the pipeline before and after blockage, which can be characterized by the blockage degree factor σ. For ease of subsequent calculation and derivation, the blockage degree factor is defined as the ratio of the length of the pipeline after blockage to the original length of the pipeline, i.e.:

[0071]

[0072] Combining equations (2) and (6), we can obtain:

[0073]

[0074] Based on experience in petroleum industry engineering, the acceptable normal local resistance of a gas pipeline can be equivalent to 5%-10% of the pipeline length. Here, it is considered that when the local resistance is greater than 20% of the pipeline length, that is, when the blockage factor is 1.2, it means that blockage has begun to occur in the pipeline and measures need to be taken to unblock it.

[0075] Once a blockage is identified in the subsea gas pipeline, it needs to be located. The location of the blockage can be determined by the intersection of the curves showing the square of the pressure before and after the blockage as a function of the pipeline length. For example... Figure 2 As shown, the intersection of the characteristic curves of the two gas pipelines before and after the blockage indicates the location of the blockage. The location of the blockage is x. L The result can be obtained by combining the characteristic equations of the two gas pipelines before and after the blockage:

[0076]

[0077] A second aspect of the present invention provides a device for detecting blockages in subsea natural gas pipelines based on pressure gradient, comprising:

[0078] The first processing unit is used to collect various parameters of the subsea gas pipeline;

[0079] The second processing unit is used to combine and calculate the pressure gradient equations before and after the blockage of the subsea gas pipeline, and obtain a calculation model to determine the degree and location of the blockage of the subsea gas pipeline.

[0080] The third processing unit is used to select the starting pressure and ending pressure of the subsea gas pipeline under the unblocked state and the starting pressure and ending pressure of the subsea gas pipeline under the current judgment condition from various parameters in the calculation model, and calculate the blockage degree factor.

[0081] The fourth processing unit is used to determine whether the blockage degree factor value is greater than a certain value; when it is less than the certain value, it is considered that the pipeline is not blocked, and when it is greater than or equal to the certain value, it is considered that the pipeline is about to be blocked.

[0082] The fifth processing unit is used to input the total length of the pipeline into the calculation model and calculate the location of the blockage in the pipeline.

[0083] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described method for determining blockages in subsea natural gas pipelines based on pressure gradient.

[0084] A fourth aspect of the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method for determining blockage of subsea natural gas pipelines based on pressure gradient.

[0085] This invention is described based on flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to specific embodiments. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the flowcharts and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0087] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for identifying blockages in subsea natural gas pipelines based on pressure gradient, characterized in that, Includes the following steps: Collect various parameters of the subsea gas pipeline; By combining and calculating the pressure gradient equations before and after blockage of the subsea gas pipeline, a calculation model is obtained to determine the degree and location of blockage. The calculation model includes a mathematical model for calculating the degree of blockage and a mathematical model for calculating the location of blockage. In the mathematical model for calculating the blockage factor, the starting and ending pressures of the subsea gas pipeline under unblocked conditions and the starting and ending pressures of the subsea gas pipeline under the current conditions to be judged are selected from various parameters to calculate the blockage factor. The system determines whether the blockage level factor value is greater than a certain threshold. If the value is less than the threshold, the pipeline is considered to be unblocked; if the value is greater than or equal to the threshold, the pipeline is considered to be about to become blocked. In the mathematical model for calculating the location of blockages, the total length of the pipeline is input, and the location of the blockage on the pipeline is calculated. The mathematical formula for calculating the congestion level factor is as follows: In the formula, , These represent the starting and ending pressures of the subsea pipeline in an unblocked state. , These are the starting pressure and ending pressure of the subsea pipeline under the current conditions to be determined; The specific formula for the mathematical model to calculate the location of the blockage is as follows: In the formula, L This represents the total length of the pipeline. This indicates the location where the blockage occurs in the pipeline.

2. The method for identifying blockages in subsea natural gas pipelines based on pressure gradient according to claim 1, characterized in that, The computational model is based on the following assumptions: Assuming the natural gas transported by the subsea gas pipeline has a volumetric water content of no more than 5%, and the flow pattern in the pipeline is annular mist flow; Assume that the pressure drop of the subsea gas pipeline is equal to its pressure drop along the pipeline, and ignore the elevation difference and local pressure drop caused by the pipe fittings; Assume that the volumetric flow rate of the medium remains constant during the process of incomplete blockage in the subsea gas pipeline.

3. The method for identifying blockages in subsea natural gas pipelines based on pressure gradient according to claim 1, characterized in that, Determine if the blockage level factor value is greater than 1.2; if the value is less than 1.2, the pipeline is considered not blocked; if the value is greater than or equal to 1.2, the pipeline is considered to be about to be blocked.

4. A device for detecting blockages in subsea natural gas pipelines based on pressure gradient, characterized in that, include: The first processing unit is used to collect various parameters of the subsea gas pipeline; The second processing unit is used to combine and calculate the pressure gradient equations before and after the blockage of the subsea gas pipeline to obtain a calculation model for judging the degree and location of the blockage. The calculation model includes a mathematical model for calculating the degree of blockage factor and a mathematical model for calculating the location of the blockage. The third processing unit is used to select the starting pressure and ending pressure of the subsea gas pipeline under the unblocked state and the starting pressure and ending pressure of the subsea gas pipeline under the current condition to be judged from various parameters in the mathematical model for calculating the blockage degree factor, and to calculate the blockage degree factor. The fourth processing unit is used to determine whether the blockage degree factor value is greater than a certain value; when it is less than the certain value, it is considered that the pipeline is not blocked, and when it is greater than or equal to the certain value, it is considered that the pipeline is about to be blocked. The fifth processing unit is used to input the total pipeline length into the mathematical model for calculating the location of the blockage and to calculate the location of the blockage on the pipeline. The mathematical formula for calculating the congestion level factor is as follows: In the formula, , These represent the starting and ending pressures of the subsea pipeline in an unblocked state. , These are the starting pressure and ending pressure of the subsea pipeline under the current conditions to be determined; The specific formula for the mathematical model to calculate the location of the blockage is as follows: In the formula, L This represents the total length of the pipeline. The location where the blockage occurred in the pipeline; p Q This is the gauge pressure displayed at the starting point of the subsea pipeline when it is not blocked, representing the normal force exerted by the fluid on the pipe wall surface at that point. p DQ This is the gauge pressure displayed at the starting point of the subsea pipeline under the current conditions to be determined, representing the normal force exerted by the fluid on the pipe wall surface at that point; p DZ This is the gauge pressure displayed at the end of the subsea pipeline under the current conditions to be determined, representing the normal force exerted by the fluid on the pipe wall surface at that point. p Z This is the gauge pressure displayed at the end of the subsea pipeline in an unblocked state, representing the normal force exerted by the fluid on the pipe wall surface at that point.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for detecting blockages in subsea natural gas pipelines based on pressure gradient as described in any one of claims 1-3.

6. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for detecting blockages in subsea natural gas pipelines based on pressure gradient as described in any one of claims 1-3.

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