CN103217457A - Method for predicting hydrates in natural gas pipeline running and cleaning processes - Google Patents
Method for predicting hydrates in natural gas pipeline running and cleaning processes Download PDFInfo
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- CN103217457A CN103217457A CN2012100164604A CN201210016460A CN103217457A CN 103217457 A CN103217457 A CN 103217457A CN 2012100164604 A CN2012100164604 A CN 2012100164604A CN 201210016460 A CN201210016460 A CN 201210016460A CN 103217457 A CN103217457 A CN 103217457A
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Abstract
The invention relates to a method for predicting hydrates in natural gas pipeline running and cleaning processes. The method comprises the following steps: 1, monitoring the gas quality parameters of a natural gas pipeline; 2, calculating through a water dew point and a water content conversion model to obtain the water dew points of a gas under different pressures; 3, calculating through the water dew point and water content conversion model and a measured normal-pressure water dew point to obtain the practical water dew point of the gas under a pipeline pressure, wherein the hydrates are generated only on the premise that liquid water exists; 4, calculating through a hydrate generating model to obtain the hydrate generating temperature of the gas under the pipeline pressure, wherein a hydrate generating condition is not reached if the temperature of the gas is lower than the hydrate generating temperature; and 5, determining whether the hydrates are generated or not through the temperature of the gas, the water dew point of the water and the hydrate generating temperature. The method can realize the accurate prediction of a case that whether the hydrate generating condition is reached in the technological zones and the main lines of a natural gas pipeline station or not, and provides a technical support for the safe running and the cleaning work of natural gas pipelines.
Description
Technical field
The present invention is a kind of natural gas line operation and pigging process hydrate Forecasting Methodology.Relate to test not to be covered of other class and piping system technical field.
Background technology
At present, the hydrate Study on Generation Model Program has been a mature technology, but is used for theoretical research or laboratory experiment more.In the operation and pigging operation of natural gas line, because the polytrope and the complicacy of makings parameter only can accurately not dope whether have the stifled generation of ice with the hydrate generation model.In service at natural gas line, because the influence of factors such as gas flow at high speed, stirring, high-pressure pulsating in the pipeline, locate to form easily the obstruction that hydrate causes pipeline, separation equipment and instrument at channel bend, pressure regulator valve etc., simultaneously, pressure, temperature and the water cut of gas are constantly to change in the pipeline, therefore hydrate generation zone also is constantly to change in pipeline, does not also have the special hydrate forecasting techniques at natural gas line at present.
In gas pipe line operation and pigging operation, mainly be to rely on operation personnel's self experience to be judged at present, also do not have special moving and the stifled Forecasting Methodology of pigging operation ice at gas pipe line by pressure reduction, fluctuations in discharge to whether icing stifled.
Rely on self experience of pipe operations personnel to judge whether to ice in gas pipe line operation and the pigging operation and block up some drawbacks of existence.Owing to judge and just roughly judge by presentation and experience, there are not theoretical direction and calculating, simultaneously because operating personnel are different with the understanding of pigging to the pipeline operation, the experience level difference, cause judged result may have bigger error, thereby influence gas pipe line safe operation and pigging operation.
Existing a kind of technology " suppresses the method that conduits by gas hydrates stops up ", and this method suppresses the generation of hydrate by the method at pipeline interpolation inhibitor in service, thereby it is stifled to avoid pipeline that ice takes place.This method only provides anti-stagnant ice stifled a solution, hydrate in the pipeline is not generated and makes a prediction, and corresponding adding technology is not provided yet.
Summary of the invention
The objective of the invention is to invent natural gas line operation and pigging process hydrate Forecasting Methodology that whether a kind of accurate prediction natural gas line station field process island and main line reach the hydrate formation condition, technical support is provided for natural gas line safe operation and pigging operation.
The present invention is in conjunction with the practical operation situation of gas pipe line, the actual water dew point of pipeline and hydrate generate temperature when obtaining gas pipe line operation and pigging operation by Model Calculation, again by with pipeline in the gas actual temperature relatively judge whether to have hydrate and generate, technical support is provided for control ice in safe operation and the pigging operation is stifled.
The invention discloses a kind of natural gas line operation and pigging process hydrate Forecasting Methodology, may further comprise the steps:
1, monitoring natural gas line makings parameter mainly comprises gas composition, gaseous tension, range of temperature, gas water dew point;
2, calculate the water dew point of gas under different pressures by water dew point and liquid water content transformation model, water dew point and liquid water content transformation model are based on the fugacity that the P-R state equation calculates vaporous water and aqueous water, try to achieve conversion relation between rock gas water cut and the water dew point according to the principle that balances each other;
3, by water dew point and liquid water content transformation model and the water at atmospheric pressure dew point that records, can calculate the actual water dew point of gas under the pipeline pressure,, then show to have aqueous water if gas temperature is lower than actual water dew point, if gas temperature is higher than actual water dew point, then show not have aqueous water; Have only under the prerequisite that has aqueous water, could generate hydrate;
4, calculate the hydrate of gas under pipeline pressure by the hydrate generation model and generate temperature, if being lower than hydrate, gas temperature generates temperature, then show to reach the hydrate formation condition, generate temperature, then show not reach the hydrate formation condition if gas temperature is higher than hydrate;
5, generate temperature by gas temperature and gas water dew point, hydrate and can judge whether to have the hydrate generation, judged result is as shown in table 1.
Hydrate generates to be judged: when gas temperature＞hydrate generates temperature, if gas temperature＞actual water dew point does not then have aqueous water, no hydrate; If gas temperature＜actual water dew point then has aqueous water, no hydrate;
When gas temperature＜hydrate generates temperature, if gas temperature＞actual water dew point does not then have aqueous water, no hydrate; If gas temperature＜actual water dew point then has aqueous water, hydrate is arranged.
Table 1 hydrate generates judges table
Water dew point and water cut conversion Calculation flow process be as shown in Figure 1:
1) initial value of supposition is as dewpoint temperature Td;
2) the new mixed system to dry gas and water vapor composition carries out component calculating;
3) consult the critical temperature Tc of i component, be mainly the critical temperature of water vapor herein;
4) calculate αHan Shuo by correlation, and calculate ai, the bi of i component and a, the b of mixed system;
5) utilize state equation to obtain rub the ear volume V and the compressibility coefficient z under P, Td condition of mixed system;
6) fugacity coefficient and the phase equilibrium constant Ki of calculating water vapor and water;
7) judge whether IYi/Ki-1I＜0? if then Td is the dewpoint temperature of calculating; If not, then turn back to the first step.
Described hydrate generation model calculation process is as shown in Figure 2:
1) supposes the hydrate structure type;
2) calculate gas dew point temperature T d;
3) the supposition hydrate generates initial value Th;
4) do you judge whether Th＞Td? if, then there is not the hydrocarbon liquid phase, given dried composition calculates fugacity fi; If not, the hydrocarbon liquid phase is arranged then, the flash calculation that exposes gas phase fugacity fi;
5) fugacity and the mole fraction xi of hydrate in the calculating mixed gas;
6) judge whether | ∑ xi-1|≤ε? if, preserve result of calculation, change the structure type of hydrate, rotate back into the first step; If not, then forwarded for the 3rd step to.
The present invention can be applicable to gas pipe line, in natural gas line operation and pigging process, under the present situation, whether there is hydrate to generate by gas in data acquisition and the Model Calculation prediction pipeline and made prediction, accurate, science predict the outcome, tally with the actual situation, it is on-the-spot actual that this method can be applied to, for gas pipe line safe operation and pigging operation provide technical support.
Description of drawings
Fig. 1 water dew point and water cut are calculated process flow diagram
Fig. 2 hydrate generates calculation flow chart
Embodiment
Embodiment. also the present invention is further illustrated with this example the specific embodiment of the present invention to be described.
Qinhuangdao-Shenyang rock gas tracheae line run duration after certain station is by portable dew point hygrometer monitoring pressure regulator valve under the gas normal pressure water dew point be-26.9 to spend, calculating the rock gas water cut by water dew point and water cut transformation model is 416.731mg/Nm3, pipeline pressure (2.31MPa) its water dew point down is 7.89 degree, be higher than in gas actual temperature (1.0 degree), result of calculation shows has aqueous water to exist; By the hydrate generation model calculate pipeline pressure (2.31MPa) down its hydrate to generate temperature is that 0.69 degree and gas actual temperature (1.0 degree) are approaching, drop to along with the gas actual temperature below 0 degree at night, can reach the hydrate formation condition in the pipeline.The hydrate blockage problem often appears in the pressure regulator valve place in actual moving process, discharges a certain amount of water in blowdown, on-the-spot result verification the accuracy of the method.
When puckery peaceful blue multiple line pigging, record certain station and enter the station that water dew point is-40.2 degree under the normal pressure by portable dew point hygrometer, calculating the rock gas water cut by water dew point and water cut transformation model is 99.224mg/Nm3, pipeline pressure (2.72MPa) its water dew point down is-7.30 degree, be lower than gas actual temperature (10.48 degree), result of calculation shows does not have aqueous water to exist; Generating temperature by hydrate generation model calculating its hydrate under pipeline pressure (2.72MPa) is 2.76 degree, is lower than gas actual temperature (10.48 degree), so does not reach the hydrate formation condition in the pipeline, no hydrate generation.When taking out rabbit, no aqueous water and hydrate in the impurity that rabbit is released, on-the-spot result verification the accuracy of the method.
Present embodiment shows, natural gas line operation and pigging process hydrate Forecasting Methodology can have been made prediction to whether having hydrate to generate in gas pipe line operation and the pigging operation process, accurate, science predict the outcome, tally with the actual situation, it is on-the-spot actual that this method can be applied to, for natural gas line safe operation and pigging operation provide technical support.
Claims (4)
1. a natural gas line moves and pigging process hydrate Forecasting Methodology, it is characterized in that may further comprise the steps:
1) monitoring natural gas line makings parameter mainly comprises gas composition, gaseous tension, range of temperature, gas water dew point;
2) calculate the water dew point of gas under different pressures by water dew point and liquid water content transformation model, water dew point and liquid water content transformation model are based on the fugacity that the P-R state equation calculates vaporous water and aqueous water, try to achieve conversion relation between rock gas water cut and the water dew point according to the principle that balances each other;
3) by water dew point and liquid water content transformation model and the water at atmospheric pressure dew point that records, calculate the actual water dew point of gas under the pipeline pressure,, then show to have aqueous water if gas temperature is lower than actual water dew point, if gas temperature is higher than actual water dew point, then show not have aqueous water; Have only under the prerequisite that has aqueous water, could generate hydrate;
4) calculate the hydrate of gas under pipeline pressure by the hydrate generation model and generate temperature, if being lower than hydrate, gas temperature generates temperature, then show to reach the hydrate formation condition, generate temperature, then show not reach the hydrate formation condition if gas temperature is higher than hydrate;
5) generate temperature by gas temperature and gas water dew point, hydrate and judge whether to have the hydrate generation.
2. natural gas line operation according to claim 1 and pigging process hydrate Forecasting Methodology is characterized in that the hydrate generation is judged as: when gas temperature＞hydrate generates temperature, if gas temperature＞actual water dew point does not then have aqueous water, no hydrate; If gas temperature＜actual water dew point then has aqueous water, no hydrate;
When gas temperature＜hydrate generates temperature, if gas temperature＞actual water dew point does not then have aqueous water, no hydrate; If gas temperature＜actual water dew point then has aqueous water, hydrate is arranged.
3. natural gas line operation according to claim 1 and pigging process hydrate Forecasting Methodology is characterized in that described water dew point and water cut conversion Calculation flow process are:
1) initial value of supposition is as dewpoint temperature Td;
2) the new mixed system to dry gas and water vapor composition carries out component calculating;
3) consult the critical temperature Tc of i component, be mainly the critical temperature of water vapor herein;
4) calculate αHan Shuo by correlation, and calculate ai, the bi of i component and a, the b of mixed system;
5) utilize state equation to obtain rub the ear volume V and the compressibility coefficient z under P, Td condition of mixed system;
6) fugacity coefficient and the phase equilibrium constant Ki of calculating water vapor and water;
7) judge whether IYi/Ki-1I＜0? if then Td is the dewpoint temperature of calculating; If not, then turn back to the first step.
4. natural gas line operation according to claim 1 and pigging process hydrate Forecasting Methodology is characterized in that described hydrate generation model calculation process is:
1) supposes the hydrate structure type;
2) calculate gas dew point temperature T d;
3) the supposition hydrate generates initial value Th;
4) do you judge whether Th＞Td? if, then there is not the hydrocarbon liquid phase, given dried composition calculates fugacity fi; If not, the hydrocarbon liquid phase is arranged then, the flash calculation that exposes gas phase fugacity fi;
5) fugacity and the mole fraction xi of hydrate in the calculating mixed gas;
6) judge whether | ∑ xi-1|≤ε? if, preserve result of calculation, change the structure type of hydrate, rotate back into the first step; If not, then forwarded for the 3rd step to.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105403673A (en) * | 2015-12-04 | 2016-03-16 | 中国石油大学(华东) | Device and method for natural gas hydrate control technical research in oil and gas conveying pipeline |
| CN105510529A (en) * | 2015-12-04 | 2016-04-20 | 中国石油大学(华东) | Oil-gas mixed transportation pipeline device and method for simulating formation, blocking and melting of hydrates |
| CN110196958A (en) * | 2019-04-16 | 2019-09-03 | 中国石油天然气股份有限公司 | A method of judging that moisture gathering line encrypts pigging |
| CN110348105A (en) * | 2019-07-05 | 2019-10-18 | 中石化石油工程技术服务有限公司 | A kind of gas hydrates generate prediction technique, forecasting system, computer readable storage medium and the electric terminal of temperature |
| CN110378075A (en) * | 2019-08-19 | 2019-10-25 | 西南石油大学 | A kind of acid and nonacid natural gas water content amount prediction technique |
| CN113484365A (en) * | 2021-07-14 | 2021-10-08 | 上海市计量测试技术研究院 | High-stability dew point fixing device |
| CN113806904A (en) * | 2020-06-15 | 2021-12-17 | 中国石油天然气股份有限公司 | Method and device for acquiring low-lying accumulated water volume of gas pipeline |
| CN115825373A (en) * | 2022-10-10 | 2023-03-21 | 中国地质大学（武汉） | Prediction method and device of natural gas hydrate, storage medium and computer equipment |
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2012
- 2012-01-18 CN CN2012100164604A patent/CN103217457A/en active Pending
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Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105510529A (en) * | 2015-12-04 | 2016-04-20 | 中国石油大学(华东) | Oil-gas mixed transportation pipeline device and method for simulating formation, blocking and melting of hydrates |
| CN105403673B (en) * | 2015-12-04 | 2017-12-08 | 中国石油大学(华东) | Device and method for preventing and controlling natural gas hydrate technical research in pipe-line |
| CN105510529B (en) * | 2015-12-04 | 2018-03-09 | 中国石油大学(华东) | Multiphase transportation pipeline device and hydrate generation, the analogy method for blocking and melting |
| CN105403673A (en) * | 2015-12-04 | 2016-03-16 | 中国石油大学(华东) | Device and method for natural gas hydrate control technical research in oil and gas conveying pipeline |
| CN110196958B (en) * | 2019-04-16 | 2022-11-01 | 中国石油天然气股份有限公司 | Method for judging encrypted pigging of wet gas gathering and transportation pipeline |
| CN110196958A (en) * | 2019-04-16 | 2019-09-03 | 中国石油天然气股份有限公司 | A method of judging that moisture gathering line encrypts pigging |
| CN110348105A (en) * | 2019-07-05 | 2019-10-18 | 中石化石油工程技术服务有限公司 | A kind of gas hydrates generate prediction technique, forecasting system, computer readable storage medium and the electric terminal of temperature |
| CN110378075A (en) * | 2019-08-19 | 2019-10-25 | 西南石油大学 | A kind of acid and nonacid natural gas water content amount prediction technique |
| CN110378075B (en) * | 2019-08-19 | 2022-02-25 | 西南石油大学 | Method for predicting water content of acidic and non-acidic natural gas |
| CN113806904A (en) * | 2020-06-15 | 2021-12-17 | 中国石油天然气股份有限公司 | Method and device for acquiring low-lying accumulated water volume of gas pipeline |
| CN113484365A (en) * | 2021-07-14 | 2021-10-08 | 上海市计量测试技术研究院 | High-stability dew point fixing device |
| CN115825373A (en) * | 2022-10-10 | 2023-03-21 | 中国地质大学（武汉） | Prediction method and device of natural gas hydrate, storage medium and computer equipment |
| CN115825373B (en) * | 2022-10-10 | 2023-08-22 | 中国地质大学（武汉） | Method and device for predicting natural gas hydrate, storage medium and computer equipment |
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Application publication date: 20130724 |