Well Control Technologies for HTHP Gas Wells in the C Block of the South China Sea

To ensure well control safety in drilling HTHP gas wells in the C Block of the South China Sea,and solve the problems of high and complicated formation pressures,high formation temperatures,a narrow safety window for drilling fluid,difficulties in maintaining of desirable properties of high density drilling fluids,several measures have been developed,including real time kick detection,overflow volume control,gradual increase of killing fluid density during killing,lost circulation prevention,drilling fluid temperature control and performance maintenance,management of coexisted kicks and lost circulation,etc.The technical measures to prevent lost circulation include improving pressure bearing capacities of formations and the plugging property of drilling fluids,modifying casing programs,controlling bottom hole circulation equivalent density,adopting staged pumping,simplifying drilling tool assemblies and controlling trip-in speed,etc.The proposed well control technologies have been used in 30 HTHP wells in the C Block of South China Sea,without an occurrence of well control incidents,which indicates that the relevant well control technologies can effectively guarantee well control safety in drilling of HTHP gas wells in the C Block of South China Sea.