Study On Diffusion And Distribution Of Oil Leaked In Buried Piping Near The Sea

With the rapid growth of the coastal city’s economy and population,the development of the coastal city has reached saturation.The contradiction between supply and demand of land,and the growing expansion of the city space development both lead to the demand of sea reclamation.The new land is unavoidable to put into the new urbanization and industrialization construction.Buried oil piping,as the underground lifeline in the industrial construction,its operation safety has attracted much attention.The buried oil piping has the characteristics of high operation pressure,large transportation and large diameter.It will not only cause economic property losses and casualties,but also pollute the environment once it leaks.The oil leakage of buried piping,especially in the coastal area,may pollute the sea area and cause serious water pollution.Therefore,it is significant to study on oil leakage properties of typical buried piping in coastal area and the seepage flow properties of the leaked oil in the soil,determine the pollution range of the oil and the amount of oil leakage,and delineate the dangerous area for the pipe leakage.The studies can accurately evaluate the influence of leakage accident in oil pipeline to the public and the environment,and providing a theoretical basis for reducing the loss of leakage accidents in buried pipeline.This paper pointed at the leakage accident of buried oil piping in the artificial land reclamation and coastal areas in China.Through constructing a model of buried oil piping,the multiphase flow theory of porous media was used to simulate the seepage and diffusion law of the leakage oil in the artificial geology in a detail.First,the simulation software was used to analyze the flow process of oil in the initial state of leakage and the state of oil products after the leakage was stopped.Because of the complexity of the leakage environment,the porosity of the soil was measured;and UDF program was used to define the porosity of the soil model,so the diffusion range of the leakage oil was calculated.Finally,the area and thickness of the leaked oil was verified by a drilling test in the actual leakage area.It was founded that the range of the leaked oil of the measured results was consistent with that of the simulation results.At the same time,the quantity of leaked oil was calculated by mathematical theory and simulation results,and results showed that the leaked oil was consistent with the actual project.The diffusion and percolation of the leaked oil in the soil were different where the soil environment near the sea,the operation of the oil pipeline and the leakage factors were different.Selecting soil porosity,water content,leakage hole size,leakage rate and other factors.And the effects on the process of oil leakage and the range-of leakage were analyzed.The simulation results showed that the size of soil porosity had a great influence on the diffusion range of the leaked oil.The water content in the soil had little effect on the percolation diffusion,and only had an influence on the range of oil-in-water.The leakage port size,leakage velocity and leakage time of the oil pipeline had some influence on the leakage diffusion.Through the related factors affecting the leakage and diffusion of the buried oil pipeline,the corresponding formula for predicting the leakage and diffusion range was obtained by fitting the data.In this paper,we studied the leakage of buried oil pipelines in the coastal area.By constructing the corresponding model to simulate the change of groundwater level,the influence of the change of underground water level caused by the alternation tide on the leakage and diffusion of the leaked oil in the soil under special geological environment of the coastal area was studied.The results showed that the tide risen and fallen would affect the leakage and diffusion of oil.Finally,the membership function matrix of various factors was constructed through the fuzzy mathematics comprehensive evaluation method,and the safety evaluation of the leakage events were carried out according to the maximum membership degree principle.According to the leakage range and safety evaluation results,the dangerous area and the risk level were defined,which could provide theoretical and technological support for the leakage accident of buried oil piping near the sea.