Research on heat transfer law of multiphase flow in wellbore under coexistence of overflow and lost circulation in deepwater drilling

Abstract

A reliable and accurate wellbore heat transfer model is essential for making critical decisions during deepwater drilling operations. This study develops a transient coupled flow model for the coexistence of overflow and lost circulation simulation in deepwater drilling. Through the established theoretical model, this paper studies the influence of gas influx, lost circulation, and coexistence of gas influx and lost circulation on wellbore temperature distribution and gas migration and analyzes the development of gas influx and lost circulation under different engineering parameters. The results show that the gas expansion after gas influx mainly occurs at the depth of 200 m and above. The gas void fraction is reduced with the increase of wellhead casing pressure, but the change range is gradually reduced. After the lost circulation occurs, the wellhead temperature, bottom hole temperature, and bottom hole pressure decrease obviously. The influence of the coexistence of gas influx and lost circulation on the change of wellbore temperature and pressure is greater than that of the two alone. The wellbore temperature under upper gas influx and lower lost circulation is generally higher than that under upper lost circulation and lower gas influx. However, the bottom hole pressure under upper gas influx and lower lost circulation is slightly smaller than that under upper lost circulation and lower gas influx.

Keywords

• Deepwater drilling
• Multiphase flow
• Heat transfer model
• Co-existence of gas influx and lost circulation