Minimum Displacement Calculation Method of Killing Well Control Technology by Bullheading

Abstract

After gas invasion and shut-in, the displacement which can completely remove the gas in the wellbore is called the minimum displacement. This paper studies how to calculate the minimum displacement. By analyzing the characteristics of fluid flow in closed wellbore after shut-in, the conditions for complete removal of gas are obtained, and the minimum displacement calculation method is obtained according to the removal conditions. The upward slippage of bubbles and the downward flow of liquid phase around the gas are the reasons why the gas cannot be completely removed under too small displacement; According to the characteristics of Bullheading, bubbles will slip upward in the form of small bubbles in the process of Bullheading; Based on the phenomenon of water seal, a formula for calculating the minimum velocity to avoid the flow around liquid phase is deduced; By comparing the minimum downward velocity of killing fluid and bubble slippage velocity, the minimum displacement is obtained by taking the larger values of the two as the calculation basis.