Abstract
In permafrost regions, long distance buried pipelines are widely used to transport oil and natural gas resources. However, pipeline problems occur frequently due to the complicated surrounding environment and transportation requirement of positive temperature. In this study, a thermal insulation layer was applied to mitigate permafrost degeneration around the buried oil-gas pipelines. Based on engineering background of the Sebei-Xining-Lanzhou natural gas pipeline in China, an indoor model test was designed and carried out in which many key indices, such as the temperature regime, vertical displacement, pipeline wall stress, and water content, were closely monitored. The test results indicate that the large heat loss of the buried pipeline produces a rapid increase in ground temperatures which seriously reduces the bearing capacity of the permafrost foundation. The buried oil-gas pipelines with a thermal insulation layer can effectively reduce the thawing range and vertical displacement of the permafrost foundation around the buried pipelines, so as to control the stress of the pipeline wall in the normal range and protect the safe and stable operation of the buried oil-gas pipelines. The experimental results can serve as a reference for the construction, operation, and maintenance of buried oil-gas pipelines in permafrost regions.
Highlights
Permafrost is defined as ground with a temperature at or below 0°C over at least two consecutive years [1]
The foundation soil of the surface layer within 20 cm is greatly influenced by the environmental temperature in the model box; it thaws in the positive temperature stage and freezes in the negative temperature stage
Due to the continuous heat release of the bare pipeline model, the temperature of the surface soil above the pipeline is higher than 0°C at the end of the third cycle, which leads to the formation of a thaw channel above the bare pipeline, which gradually increases with the freezethaw cycles
Summary
Permafrost is defined as ground (soil or rock including ice) with a temperature at or below 0°C over at least two consecutive years [1]. Permafrost regions account for approximately 25% of Earth’s land surface in which there are abundant oil and gas resources [2]. Long distance pipelines are one of the most efficient and economical transmission ways; a large number of oil-gas pipeline projects have been built to develop and transport oil and natural gas resources in permafrost regions [3,4,5]. The above wellknown oil-gas pipelines play an important role in the effective exploitation and utilisation of oil and gas resources in permafrost regions. Due to the complicated surrounding environment and special transportation requirements of oil and gas, pipeline disease occurs frequently in permafrost regions
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