Coupled thermal model of wellbore and permafrost in Arctic regions

During drilling operations in the Arctic permafrost region, drilling mud with a higher temperature flowing in the wellbore can lead to thawing of the permafrost. Unpredictable thawing of the permafrost results in severe settling of the wellhead. In addition, the wellbore and permafrost interact as a result of the permafrost thaw. At present, researches on heat and mass transfer in permafrost around the well bore are very limited. The traditional thermal models for wellbore and formation cannot actual simulate the temperature fields without considering the effect of permafrost thaw. In this regard, a coupled thermal model of the wellbore and permafrost is established considering the latent heat of fusion, water migration, and the change in thermal parameters. In order to reveal the interactions between wellbore and permafrost in Arctic permafrost regions, comparisons between the new model and traditional model are made through a series of numerical simulations. The temperature fields and water content are thoroughly analyzed through a case study. In addition, numerical simulations are carried out to evaluate the effect of cement thermal conductivity on the wellhead stability. The conclusions and suggestions in this paper can provide safety guidance for oil and gas exploration in Arctic regions. (C) 2017 Elsevier Ltd. All rights reserved.