An Analytical Model for Predicting Temperature Fields during Fluid Circulation in a Deep-Sea Well

Abstract

Summary Accurate prediction of temperatures along a well during deep-sea drilling (DSD) is significant for wellbore stability analysis. In this paper, an analytical model is developed to study the thermal behavior around wellbore during DSD. The analytical solutions for temperatures in the tubing, annulus, and formation are obtained in Laplace space, and their values in time domains are obtained by the numerical Stehfest method. A sensitivity study of temperature distribution under different injection temperature and rate, seawater depth, and wellbore length is carried out, and a comparison is made for the thermal behavior between onshore drilling and DSD. It is found that injection rate plays a dominate role in the bottomhole temperature (BHT), which decreases by more than 40°C after 6 months when it varies from 2 to 20 kg/s. Injection temperature only affects the temperature along wellbore at a depth less than 2000 m. There is large difference in the temperatures along the wellbore between DSD and onshore drilling. The difference in the temperature at the depth of seabed and bottomhole between the two cases reaches 80 and 70°C, respectively, after 1 day. In addition, the analytical model can work as a benchmark for other models predicting the thermal behaviors during DSD.