Real-time identification of the bottomhole gas invasion state is the key to well control during managed pressure drilling( MPD),which is directly related to the selection of follow-up operations involving the gas circulation exhaust based on standpipe pressure control or the conventional shut-in procedure.In viewof the factors of gas migration expansion and dissolution,it is pointed out here that the equilibrium between outlet flowand inlet flowdoes not directly mean the stop of bottomhole gas invasion,and ...