Rapid permafrost thaw under buried oil pipeline and effective solution using a novel mitigative technique based on field and laboratory results

The China–Russia crude oil pipeline (CRCOP) has been in operation for over 10 years. In order to obtain the necessary data for pipeline research and provide real-time warning for pipeline operation, an in-situ composite monitoring system of pipeline–permafrost interaction along the CRCOP was established. Monitoring results has shown that a thaw bulb develops around the CRCOP, urging consolidation in strongly thawed segments. The key to maintaining the stability of warm-oil pipelines buried in permafrost is to mitigate permafrost thaw and keep the differential settlement of the pipeline in its allowable strain range. To maintain the stability of CRCOP, a novel technique is proposed to mitigate thaw settlement of underlying permafrost, preventing pipeline failure and oil spills and in turn environmental disaster. Its cooling performance is evaluated based on indoor model testing platform using in-situ monitoring data including oil temperature, ground temperature and air temperature. The initiation and development of a thaw bulb was observed around the CRCOP, urging consolidation in strongly thawed segments. Additionally, an indoor model test is conducted to verify the cooling effect of a U-shaped air ventilation duct (U-AVD). The results show that the U-AVD is conducive to mitigating permafrost thaw and removing the thaw bulb around the buried pipeline in the cold season. The findings in this article can provide a reference for studies on the CRCOP and other pipeline engineering in permafrost regions.