Diseases Of Buried Gas Pipelines In Permafrost Regions Research On Prevention Measures

As the space for human activities expands and the demand for resources increases,humans gradually turn their attention to remote areas such as space,oceans,and cold regions.In the past four to fifty years,many countries have stepped up the development of oil and gas resources in the Arctic and cold regions to resolve the crisis caused by the energy shortage.However,the cold area with permafrost has its own unique environmental characteristics.It is a very fragile environmental system that cannot be recovered once it is destroyed.The area of permafrost in China is about 2.148 million square kilometers,accounting for 22.4% of the country's land area.Seasonal permafrost is distributed in provinces and municipalities north of the Yangtze River in China,and its area accounts for 54% of China's territory.These permafrost areas contain A large amount of oil and natural gas energy,how to transport energy without damaging the unique natural environmental conditions of frozen soil has become a difficult problem,and buried pipelines,as the main transportation method for oil and natural gas,have been used in energy transportation and other fields.With a decisive role,pipeline transportation has the advantages of high efficiency,good safety,and low cost.With the exploitation of a large number of frozen soil resources,the laying length of oil and gas pipelines is also increasing.The terrain and environment of the frozen soil area passing by It will also become more complicated,facing the problems of frost heaving and thawing of permafrost.Due to the direct contact between the buried pipeline and the frozen soil,it is inevitable to be affected by the heat release of the positive temperature medium in the pipeline,making the soil around the pipeline It is more susceptible to diseases such as melting collapse,collapse,and pipe warping.As a result,the pipeline has a large displacement,and even has problems such as pipe breakage and liquid leakage that endanger the safety of the pipeline operation and damage the natural environment.In response to the various diseases that have occurred above,how to prevent and control the diseases of oil and gas pipelines in cold areas has become a top priority.This paper focuses on the related disease problems caused by the gas pipeline passing through the frozen soil area,combined with the on-site disease investigation of the Lajishan section of a gas pipeline in Qinghai,taking the frozen soil environment on the site and the pipeline embedding conditions as the research objects,and combining the frozen soil of the Lajishan section The characteristics of the soil,and considering the impact of climate warming in the Qinghai-Tibet Plateau in the future,on-site monitoring of typical locations and the establishment of thermal insulation measures for disease management,the main content and conclusions of the paper are as follows:(1)Through long-term monitoring and data collection of the soil temperature field around the pipeline,the frozen soil in this area is an island-shaped permafrost with poor thermal stability.The positive temperature gas pipeline has a great impact on the surrounding frozen soil.It causes the melting of the soil near the pipeline and the formation of collapse and other diseases;the upper limit of permafrost in the natural state changes in the range of 1.5 to 2.0m,and the heat release of the positive temperature gas pipeline without thermal insulation affects the horizontal range of the surrounding soil in the range of 1.0 to About 1.5m,the melting depth directly under the pipeline is about 5.47 m,the freezing period is 5 months,and the melting period is 7 months;after treatment with thermal insulation materials,the horizontal melting range is reduced by about 0.5m,and the melting depth under the pipe bottom is reduced About 3.04 m,indicating that the laying of thermal insulation material has a better effect on suppressing the heat release of the pipeline and reducing the disturbance of the surrounding frozen soil.(2)According to the theory of heat transfer and considering the effect of phase change,a two-dimensional unsteady temperature field equation is established.The ANSYS thermal analysis module is used to simulate the changing state of the pipeline during 30 years of operation.The pipeline melts in the early stage of operation(in the first 10 years)The rate is faster,and then gradually stabilizes,indicating that pipeline monitoring and maintenance should be strengthened in the previous decade.(3)Three types of polyurethane insulation materials with different thicknesses are used as the insulation measures of the pipeline,and the combined measures of insulation layer,insulation layer-pipe bottom insulation board and insulation layer-U-type insulation board are used to suppress the heat release effect of the pipe and protect the pipe In the surrounding frozen soil,the insulation layer greatly reduces the melting depth of the bottom of the pipe and reduces the disturbance of permafrost;the insulation layer-the bottom insulation board can further reduce the melting depth of the bottom of the pipe;the combined measures of the insulation layer-U-shaped insulation board The melting range of the bottom of the pipe is controlled,and the horizontal melting distance is also taken into account.It is suitable for pipelines with high medium temperature and high temperature frozen soil sections.(4)Four different depths were discussed for the reasonable buried depth of the gas pipeline,and the melting range under different years was compared to obtain a reasonable buried depth distance,which can provide a reference for future engineering construction.