Abstract: A subsea drilling method for controlling the bottom hole annular pressure and downward injection rate during mud cap drilling operations from a mobile offshore drilling unit with a low pressure marine riser and subsea blowout preventer. The method called controlled mud cap drilling uses the hydrostatic head of a heavy annular mud (fluid) managed or observed in order to balance the highest pore pressure in the well and to control the injection rate, by using a subsea mud lift pump and a control system to regulate the process.

Abstract: A subsea drilling method for controlling the bottom hole annular pressure and downward injection rate during mud cap drilling operations from a mobile offshore drilling unit with a low pressure marine riser and subsea blowout preventer. The method called controlled mud cap drilling uses the hydrostatic head of a heavy annular mud (fluid) managed or observed in order to balance the highest pore pressure in the well and to control the injection rate, by using a subsea mud lift pump and a control system to regulate the process.

Abstract: A subsea drilling method for controlling the bottom hole annular pressure and downward injection rate during mud cap drilling operations from a mobile offshore drilling unit with a low pressure marine riser and subsea blowout preventer. The method called controlled mud cap drilling uses the hydrostatic head of a heavy annular mud (fluid) managed or observed in order to balance the highest pore pressure in the well and to control the injection rate, by using a subsea mud lift pump and a control system to regulate the process.

Abstract: A subsea drilling method for controlling the bottom hole annular pressure and downward injection rate during mud cap drilling operations from a mobile offshore drilling unit with a low pressure marine riser and subsea blowout preventer. The method called controlled mud cap drilling uses the hydrostatic head of a heavy annular mud (fluid) managed or observed in order to balance the highest pore pressure in the well and to control the injection rate, by using a subsea mud lift pump and a control system to regulate the process.

Abstract: A subsea drilling method and system for controlling the drilling fluid pressure, where drilling fluid is pumped down into the borehole through a drill string and returned back through the annulus between the drill string and the well bore. The drilling fluid pressure is controlled by draining drilling fluid out of the drilling riser (8) or BOP (6) at a level between the seabed and the sea water in order to adjust the hydrostatic head of drilling fluid. The drained drilling fluid and gas is separated in a subsea separator (28) where the gas is vented to surface through a vent line (39), and the fluid is pumped to surface via pump (40).

Abstract: A subsea mud pump can be used to return heavy drilling fluid to the surface. In order to provide a less stringent requirement for such a pump and to better manage the bottom hole pressure in the case of a gas kick or well control event, the gas should be separated from the drilling fluid before the drilling fluid enters the subsea mud pump and the pressure within the separating chamber. The mud pump suction should be controlled and kept equal or lower than the ambient seawater pressure. This can be achieved within the cavities of the subsea BOP by a system arrangement and methods explained. This function can be used with or without a drilling riser connecting the subsea BOP to a drilling unit above the body of water.