Wellbore heat transfer law of carbon dioxide coiled tubing drilling

Key words:  carbon dioxide  coiled tube  wellbore heat transfer  pressure loss

Abstract:

Based on heat transfer process of carbon dioxide wellbore flow, the heat and pressure transfer mechanism of carbon dioxide in the wellbore, as well as the carbon dioxide property variation and phase change were investigated. The wellbore heat transfer model of carbon dioxide was developed, through which the wellbore temperature and pressure profiles were analyzed using alternate direction method. The results show that heat transfer efficiency is relatively high in wellbore. The increase extent of temperature for carbon dioxide reduces with the well depth gradually. Annular temperature of carbon dioxide decreases along the flow, and the temperature decreases significantly near the wellhead. The phase of carbon dioxide changes from liquid to supercritical state along the flow, then to liquid phase in the annular area. It changes to liquid-gas state at last.