Simulation Study Of Dynamic Well Killing When Gas Drilling Meets High Pressure Gas Formation

The advantages of gas drilling in improving rate of penetration,prolonging bit life,reducing formation damage and effectively protecting oil and gas reservoir have been widely recognized,and it is an important technology to realize "excellent and fast" drilling.However,in the case of unknown high-pressure gas reservoir,the blowout accident may be caused by the high-pressure gas flowing up to the wellhead caused by the formation gas flowing up to the wellhead.At present,when gas drilling encountering unknown high pressure gas reservoir,there is no effective control method to ensure wellhead safety and quickly balance bottom hole pressure in a short time.In this paper,four common gas drilling well control methods are analyzed,and the dynamic well killing method is selected as a well control method to deal with the above-mentioned well conditions.By considering the wellbore temperature field,gas-liquid two-phase flow friction and gas slippage velocity,and applying the continuity equation,momentum equation and gas production equation,we established an annular gas-liquid two-phase flow model suitable for dynamic well killing after gas drilling encountering high-pressure gas reservoir.Based on the established two-phase flow model,the method of installing pressure gauge on the relief pipe line can improve the performance of gas-liquid two-phase flow Based on the relationship between gas production and formation pressure,we propose a method to quickly determine the pressure of high-pressure gas reservoir when the well cannot be shut in.Through the study of the conditions for the establishment of annular liquid column and the constraints of well killing process parameters in the process of dynamic well killing,the principle of quick response on site,quick implementation of well killing operation and formation pressure as soon as possible,and the matching of well killing parameters On the basis of the two-phase flow model,we have developed a simulation software,which can be used for well killing simulation and well killing parameter design.Finally,a set of well killing parameters optimization design process which can guide the field implementation of dynamic well killing method is formed.