The Prediction of Hydrate Formation Regions in the Wellbore during Supercritical Carbon Dioxide Drilling

In order to improve the safety and efficiency of SC-CO2 drilling (supercritical carbon dioxide drilling), it is necessary to deal with the formation of CO2 hydrate in the wellbores. Based on the hydrate formation mechanism analysis, a model for predicting the formation region of CO2 hydrate in the wellbore was built up, and the definite conditions and numerical resolution methods were proposed. Computational analysis was carried out by designing examples. It was shown that hydrate formation in the annulus decreased non-linearly in quadratic polynomial relations with the increasing of injection temperature or inhibitor dosage. And with the increasing of wellhead back pressure, hydrate formation increased with increasing rate reducing gradually (first in logarithmic relations and then in quadratic polynomial relations). The research achievements could provide a theoretical reference for hydrate prevention during SC-CO2 drilling.