Research on Wellbore Temperature Field with Helical Flow of Non-Newtonian Fluids in Drilling Operation

Understanding wellbore temperature and its changing regularity is very critical for drilling safely and efficiently.According to the first law of thermodynamics and heat transfer theory,a complete temperature field mathematical model for drilling circulation was established.The heat transfer mechanism in spiral flow of non-Newtonian fluid in wellbore and the effect of hydraulic energy and mechanical energy on wellbore temperature field were analyzed.A preliminary discussion was conducted regarding calculation of ECD under high temperature and high pressure and control over wellbore temperature.The model results matched well with field experimental data.Numerical simulation indicated bottomhole temperature increased by 4.5 ℃ at the depth of 2 000 m,and 7.8 ℃ at 5 000 m respectively when the rotary speed of drillstring rose from 0 r/min to 200 r/min.The bottomhole temperature increased exponentially with the increase of rotary speed,the drill string rotary speed had much higher effects on bottomhole temperature with the increase of well depth.This model can provide a theoretical reference for hydraulic design of drilling in HTHP formation and temperature control during field operations.