Transient flows in a wellbore during killing of an empty well

Failure to adequately equipping the wellhead with appropriate well control equipment may result in a high pressure in the gas drilling when it reaches a high-yield gas layer. This would require the execution of a well killing operation to facilitate follow-up drilling and well completion. An empty well of gas-phase brings implementation of a gas-liquid two-phase transient flow, filling with killing mud. The operation may also entail coupling of the transient seepage from the formation with the gas-liquid two-phase transient flow through the wellbore. In this study, a mathematical model and a numerical method for coupling the transient gas flow through the formation with the gas-liquid two-phase transient flow in the wellbore were developed. The numerical simulation results showed that successful killing of an empty gas-drilled well required proper co-ordination of several key parameters among which the wellhead backpressure is particularly crucial to the operation. The findings of this study promise to facilitate the pro-cess design and parameter optimization for the killing of empty gas-drilled wells.