Study on Non-Isothermal Three-Phase Flow Characteristics in Large-Diameter Drilling Annular

As oil and gas exploration extends into ultra-deep land and sea environments, developing accurate and efficient hydraulic computation models is essential for improving safe and effective drilling techniques. This paper presents a non-isothermal transient hydraulic computational model developed in MATLAB, which integrates the wellbore temperature and flow fields to simulate temperature, pressure, and phase distributions during gas-liquid-solid three-phase flow in deep wells with large annular ratios. Through example calculations, we examine the effects of the annular ratio and convective heat transfer coefficient on wellbore flow. Results indicate that increasing the annular ratio decreases bottom-hole temperature and pressure; specifically, increasing the annular ratio from 1.5 to 3.5 results in approximately a 10% reduction in pressure and a temperature drop of over 50 K. Additionally, when considering convective heat transfer in the drilling fluid, wellbore temperature increases gradually with depth, peaking at about 1/8 of the total well depth. These findings provide theoretical guidance for designing drilling programs and selecting well control strategies for ultra-deep wells.