Application of the Darcy-Stefan model to investigate the thawing subsidence around the wellbore in the permafrost region

A key challenge in Exploring oil and gas resources in permafrost regions is to predict the thawing subsidence frozen soil around the wellbore. At present, the traditional thermo-hydro-mechanic (THM) model calculat thawing subsidence without actually considering the spatial-temporal evolution of the thawed-frozen boundat The Darcy-Stefan model is used to describe the internal mobile interface problems in the heat transfer of turated porous media due to ice/water phase transitions. In this paper, we established the coupling model of t Darcy-Stefan model and the elastic theory of porous media, including boundary conditions of heat transfer ai Darcy flow on the moving boundary. The new model was validated through a series of small-scale examples a: a test well in the Arctic region, which demonstrated the predicted subsidence amount of ground surface arou: the wellhead was in good agreement with the field test data. Further research indicated that with the increase the thawing zone, the accuracy of calculation for the thawing subsidence could be significantly improved using the THM model and considering the internal moving boundary. The models and conclusions in this pap can help design more reliable wellbore in permafrost regions throughout the expected life.