Migration laws of petroleum in silty clay under freeze-thaw action

Petroleum extraction and transportation in cold regions often result in leakage accidents, which can cause severe environmental pollution. The prevalent freeze-thaw cycles in these areas significantly influence the migration and dispersion of petroleum. Therefore, understanding these processes is essential for effective environmental protection. The experimental results indicate that capillary action, liquid pressure, and particle adsorption primarily influence petroleum migration in the unfrozen zone. Under freeze-thaw cycles, proper temperature gradients facilitate petroleum migration from unfrozen to frozen zone, while extreme temperature gradients impede this migration. The migration processes of water and petroleum are interdependent and mutually restrictive. An increase in initial moisture content promotes petroleum migration. However, when the moisture content exceeds a certain threshold, a significant amount of pore water (or ice) occupies the pore space, which hinders petroleum migration. Additionally, as the number of freeze-thaw cycles increases, the capability of petroleum to migrate into the frozen zone significantly improves. These findings provide experimental methods and scientific evidence for further exploration of petroleum migration mechanisms in cold regions and the development of effective soil contamination remediation strategies.