Gas pipeline pigging period determination method based on pigging dirt generation rate

Abstract

The invention discloses a gas pipeline pigging period determination method based on pigging dirt generation rate, which comprises the following steps: firstly, acquiring the dirt formation rate of a pipeline in a certain period by collecting gas pipeline data, then calculating the critical dirt amount of the pipeline by constructing a pipeline pigging model and combining three common pigging scheme determination methods, and finally determining the pigging period of the pipeline according to the critical dirt amount. And finally, according to the pipeline dirt forming rate and the critical dirt amount, the pipe cleaning period of the pipeline is calculated and determined, the site is guided to conduct pipe cleaning operation on the pipeline regularly according to the pipe cleaning period, various dirt existing in the gas conveying pipeline is removed, and therefore safe and stable operation of the pipeline and related equipment such as valves and flow meters along the pipeline is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas pipeline operation and maintenance, and in particular relates to a method for determining a gas pipeline cleaning cycle based on a cleaning waste generation rate, and is mainly used to determine a target natural gas pipeline cleaning cycle. Background Art

[0002] During the operation of a gas pipeline, a large amount of dirt usually accumulates in the pipeline due to the precipitation and collection of hydrocarbons and water in the natural gas, condensation and precipitation of solid impurities carried in the natural gas, corrosion of the inner wall of the pipeline, and production of hydrates.

[0003] When there is a lot of dirt in the pipeline, the roughness of the inner wall of the pipeline increases, the flow resistance increases, and the effective flow area of ​​the pipeline decreases, which will seriously affect the gas transmission efficiency, cause low compression efficiency of the compressor, and damage valves, pressure regulating skids, flow meters and other related equipment along the line. In addition, this will also cause the pipeline to fail to meet the high-precision requirements of internal inspection, affecting the development of internal inspection work. Some powder accumulation occurs in the separator, and inspection and maintenance operations may even cause spontaneous combustion, posing a huge safety hazard.

[0004] The common method to remove dirt from gas pipelines is regular cleaning. At present, there is no complete and unified standard for determining the cleaning cycle of pipelines at home and abroad. For example, the standards Q / SY GD 1003-2014 "Oil and Gas Pipeline Cleaning Operation Manual" and Q / SYGD0225-2013 "Oil and Gas Pipeline Cleaning Operation Technical Regulations" only stipulate that the basis for determining the cleaning cycle is the change in pipeline flow, oil quality and transportation process, which can only give operators a qualitative guidance. Ultimately, it is necessary to comprehensively analyze many factors such as the properties of the pipeline medium, process conditions, and environmental conditions to comprehensively judge whether cleaning is needed. In practical engineering applications, most of the cleaning plans are determined by three methods: minimum allowable transmission efficiency, maximum allowable liquid accumulation, and maximum allowable pressure drop. However, it is found that the calculation method has certain limitations during the application process and cannot be effectively applied and cannot be used to guide field practice. For example, the minimum gas transmission efficiency method is not applicable to conditions where the pipeline flow exceeds the design flow.

[0005] The present invention calculates the dirt formation rate of the pipeline, constructs a pipeline cleaning model, combines three cleaning scheme determination methods, calculates the critical dirt volume of the pipeline, and thus obtains the pipeline cleaning cycle. Summary of the invention

[0006] The present invention provides a method for determining the cleaning cycle of a gas pipeline based on the generation rate of cleaning dirt in the pipeline to determine the cleaning cycle of a gas pipeline, regularly remove dirt in the pipeline, and ensure safe and stable operation of the pipeline.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] S1: Collect the operating parameters of the pipeline within a certain period and the cumulative amount of pollutants removed, and preliminarily calculate the pollutant formation rate;

[0009] S2: Construct a pipeline cleaning model based on professional simulation software or fluid mechanics and deposition theory, and calculate the critical amount of dirt in the pipeline in combination with the method for determining the cleaning scheme;

[0010] S3: Determine the pipeline cleaning cycle based on the pipeline dirt formation rate and critical dirt volume.

[0011] In constructing the pipeline pigging model, the required pipeline operating parameters include but are not limited to the actual pipeline output, the designed pipeline output, the operating temperature, the operating pressure, the upstream pressure of the pipeline, and the downstream pressure of the pipeline; the parameters are the flow parameters under pigging; the parameters are the parameters during the pigging process; and all parameters are transient parameters.

[0012] The combined pigging scheme determination methods are: Determined according to the minimum allowable transmission efficiency. When the pipeline transmission efficiency is less than 80%, pigging operations should be implemented. The calculation formula is: It is determined based on the maximum allowable liquid accumulation, and the criterion is that the liquid accumulation in the pipeline does not exceed the processing capacity of the downstream liquid collector; it is determined based on the maximum allowable pressure drop. In production, the sharp change in pipeline pressure drop caused by abnormal factors can be used as an early warning signal for pipe cleaning. When the pipeline has a maximum allowable pressure drop requirement, the pipe cleaning cycle can be determined according to the allowable pressure drop of the pipeline. When dirt accumulates in the pipeline, the pipeline friction coefficient becomes larger, and the upstream and downstream pressure difference increases. In actual production, some units use 0.7MPa as the maximum allowable pressure difference, and use this as the basis for judging whether pipe cleaning operations are needed.

[0013] Where: Q r ——Actual pipeline capacity, m 3 / s; Q is the designed flow rate of the pipeline, m 3 / s.

[0014] The calculation of pipeline flow parameters is as follows:

[0015] 201: Modeling the rate of sewage production in pipes

[0016] 202: Establish a pipeline cleaning model, substitute the pipeline operating parameters to calculate the critical amount of dirt Mc in the pipeline,

[0017] 203: Calculate and determine the cleaning cycle

[0018] Where: V t ——Sewage production rate, Kg / month; M t ——Cumulative amount of dirt removed, Kg; Tt ——certain cleaning cycle, month; M c ——critical amount of dirt, Kg; T c ——Pipe cleaning cycle, month. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic flow chart of a method for determining a gas pipeline pigging cycle based on a pigging waste generation rate according to the present invention;

[0020] Figure 2 This is a flow chart of calculating the cleaning cycle of the present invention;

[0021] Figure 3 A pipeline model constructed using OLGA software for the present invention;

[0022] Figure 4 The critical dirt volume result of the pipeline is calculated for the present invention. DETAILED DESCRIPTION

[0023] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0024] The first step is to collect the operating parameters of the pipeline within a certain period and the cumulative amount of dirt removed. The operating parameters of the pipeline are shown in Table 1: Table 1 Pipeline parameters

[0025] The pigging data of each pipeline are shown in Table 2: Table 2 Pipeline pigging data Pipeline Name Cleaning time Cumulative cleaning times Cumulative amount of dirt removed / kg Pipeline 1 2021.05-2024.05.14 4 3802 Pipeline 2 2021.05.16-2024.06 5 1229.6 Pipeline 3 2015.05.07-2022.05.24 3 2000 Pipeline 4 2014.07.09-2024.08.19 11 2301.8 Pipeline 5 2016.04.17-2024.06.28 22 4856

[0026] The dirt formation rate was calculated and the results are shown in Table 3: Table 3 Pipeline dirt formation rate Pipeline Name Pipeline 1 Pipeline 2 Pipeline 3 Pipeline 4 Pipeline 5 Fouling rate (kg / month) 104.259 33.718 23.650 18.971 49.366

[0027] Construct a pipeline pigging model, such as Figure 3 shown.

[0028] Combined with the method for determining the pigging plan, calculate the critical amount of dirt in each pipeline, such as Figure 4 shown.

[0029] Calculate the cleaning cycle of each pipeline according to the formula:

[0030]

[0031] Where: V t ——Sewage production rate, Kg / month; M c ——critical amount of dirt, Kg; T c——Pipe cleaning cycle, month.

Claims

1. A method for determining a gas pipeline pigging cycle based on pigging waste generation rate, characterized in that: The process includes the following (Figure 1): S1: Collect the operating parameters of the pipeline within a certain period and the cumulative amount of pollutants removed, and preliminarily calculate the pollutant formation rate; S2: Construct a pipeline cleaning model based on professional simulation software or fluid mechanics and deposition theory, and calculate the critical amount of dirt in the pipeline in combination with the method for determining the cleaning scheme; S3: Determine the pipeline cleaning cycle based on the pipeline dirt formation rate and critical dirt volume.

2. The pipeline pigging model according to claim 1, characterized in that: In constructing the pipeline pigging model: ① The required collection pipeline operating parameters include but are not limited to the actual pipeline output, pipeline design output, operating temperature, operating pressure, pipeline upstream pressure, and pipeline downstream pressure; ② are flow parameters under pigging; ③ are parameters during the pig movement process; ④ all parameters are transient parameters.

3. The method for determining a pigging scheme according to claim 1, characterized in that: The determination methods are: ① According to the minimum allowable transmission efficiency, when the pipeline transmission efficiency is less than 80%, it is advisable to implement the pipeline cleaning operation. The calculation formula is: ② Determined according to the maximum allowable liquid accumulation, the criterion for determination is that the amount of liquid accumulated in the pipeline does not exceed the processing capacity of the downstream liquid collector; ③ Determined according to the maximum allowable pressure drop. In production, the rapid change caused by abnormal factors in the pipeline pressure drop can be used as an early warning signal for cleaning. When the pipeline has a maximum allowable pressure drop requirement, the cleaning cycle can be determined according to the allowable pressure drop of the pipeline. When the pipeline is contaminated, the friction coefficient of the pipeline increases, and the upstream and downstream pressure difference increases. In actual production, some units use 0.7MPa as the maximum allowable pressure difference, and use this as a basis to determine whether cleaning operations are needed. Where: Q r ——Actual pipeline capacity, m 3 / s; Q is the designed flow rate of the pipeline, m 3 / s.

4. A method for determining a gas pipeline pigging cycle based on pigging waste generation rate according to claim 1, characterized in that: The calculation pipeline flow parameters are calculated according to the following steps (Figure 2): 201: Modeling the rate of sewage generation in pipes 202: Establish a pipeline cleaning model, substitute the pipeline operating parameters to calculate the critical amount of dirt Mc in the pipeline, 203: Calculate and determine the cleaning cycle Where: V t ——Sewage production rate, Kg / month; M t ——Cumulative amount of dirt removed, Kg; T t ——certain cleaning cycle, month; M c ——critical amount of dirt, Kg; T c ——Pipe cleaning cycle, month.

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