Simulated Calculation of Bullheading Method When the Well is Empty

In the case of drilling mud completely erupted out of wellbore in high pressure gas wells, a series of fluid flowing governing equations are established in the consideration of coupling relationship between gas in well bore and formation. The change in casing pressure and bottom hole pressure with time was numerically simulated during shut in and well killing process. The results show that casing pressure and bottom hole pressure can achieve stable value quickly after shut in. The casing pressure increases rapidly first and then decreases to zero in well killing process. The earlier a well killing is performed, the smaller the peak value of casing pressure will occur under the same kill rate. A high kill rate can generate a small peak value of casing pressure after the well killing starts.