Fully transient coupled prediction model of wellbore temperature and pressure for multi-phase flow during underbalanced drilling

Abstract

Considering gas-liquid-solid three-phase flow and heat transfer, the accurate simulation of wellbore temperature and pressure profile while underbalanced drilling (UBD) has been predicted significantly in deep well drilling. Firstly, the research presents a fully transient coupled prediction model of wellbore temperature and pressure field and the thermophysical properties of circulating fluid are taken into consideration, and a double-cycle iterative algorithm for the axial and radial coupled solution of wellbore temperature and pressure is proposed. The model is discretized by using the finite volume method and is verified by the two-phase flow temperature and pressure data from the Louisiana full-size experiments. Then, qualitatively and quantitatively comparisons with water-based mud (WBM) and oil-based mud (OBM) to analyze the coupled variation of transient wellbore temperature and pressure. The sensitivity analysis between WBM and OBM is carried out and WBM is more sensitive to the thermophysical properties compared with OBM. Finally, the feasibility study of calculating bottom-hole pressure according to simple linear temperature is launched. It is found that the average of formation temperature and linear cyclic temperature (AFLT) model that a simplification of the temperature model due to the approximate method is more accurate and convenient between WBM and OBM. This research on wellbore temperature and pressure profile intuitively understands the complex problems of wellbore multi-phase flow, and further provides a theoretical reference for controlling well kick and extending to horizontal, highly deviated well and geothermal wells.