Study on the leakage morphology and temperature variations in the soil zone during large-scale buried CO2 pipeline leakage

In the CCUS technology chain, buried CO2 pipelines are inevitable under special terrain conditions. Due to the concealment and the complexity of the soil, they have a higher possibility of leakage. However, there is limited research on buried CO2 pipeline leakage processes. In this study, authors used existing industrial-scale pipelines as CO2 storage containers and constructed a large-scale buried CO2 pipeline experimental system. The leakage hole size and direction were considered to investigate the leakage morphology and temperature changes in the soil. The results showed that during the small-hole leakage, dry ice spheres were formed, which adhered to the pipeline. According to the change of temperature field, the dry ice spheres expanded towards weak areas in the soil, rather than strictly along the jet direction. The volume of dry ice spheres generated in the upward leakage process was the largest, while the volume was the smallest in the downward leakage process. Due to the soil resistance, the volume of dry ice spheres generated in the 3 mm leakage process was always greater than 9 times that of the 1 mm leakage process. The experimental results provide important references for optimizing leakage detection systems and conducting leakage risk assessments.