Experimental study on the low-temperature distribution characteristics of leaks in buried supercritical/dense-phase CO2 pipelines

In the industrial application of carbon capture, utilization, and storage (CCUS) technology, long-distance buried pipelines are responsible for safely and economically transporting captured CO 2 to storage or utilization sites. However, the complexity of the soil environment exposes these pipelines to a high risk of leakage. Currently, research on temperature fields after leakage in buried CO 2 pipelines remains limited. This study carried out large-scale leakage experiments on buried supercritical/dense-phase CO 2 pipelines under multiple working conditions, including different leak aperture sizes, leak hole shapes, pipeline internal pressures, pipeline internal temperatures, burial depths, and leak hole orientations, to explore the leakage law in soil, soil temperature changes, low-temperature distribution on the pipe wall, and the influence range of the low-temperature zone on the pipeline. The results show that the maximum soil temperature drop increases with the increase of leak aperture, internal pipe pressure and burial depth, but decreases as the internal pipe temperature rises. Under all test conditions, the lowest soil temperature usually occurs 100–150 mm away from the leak port, instead of near the leak port; the minimum soil temperature can reach −87.19 °C, and the 0 °C isotherm extends beyond the test area to the ground surface. The lowest pipe wall temperature mostly appears in the middle and lower parts of the pipe, and can drop to −69.62 °C. The −60 °C and 0 °C isotherms extend up to 1 m and 1.6 m away from the pipe wall, respectively. The experimental data can provide reference for engineering pipeline operation and provide verification data for numerical simulation research.