Patent ID: 7958948

Claim:
Method for use and return of drilling fluid/cuttings from a well, which is drilled on the ocean floor in connection with the offshore related oil production and gas production, where a drilling stem ( 12 ) runs from a drilling rig or drilling vessel ( 10 ) down into a drilling hole and where a blowout preventer (BOP) ( 14 ) is arranged on said well, comprising the following steps, without a riser being arranged between the rig or vessel and said blowout preventer ( 14 ): a) pumping drilling fluid down the drill stem ( 12 ) in the well, whereby drilling fluid is returned on the outside of the drill stem in an annular space in the drilling hole and up to said blowout preventer ( 14 ) for discharge therefrom at a predetermined outlet pressure; and b) leading the drilling fluid from the blowout preventer ( 14 ) to and through a sealing and pressure-regulating device ( 16 ) arranged on said blowout preventer and further to pump module ( 18 ) arranged adjacent to the well, said sealing and pressure-regulating device ( 16 ) having an outlet passage and means to regulate the level of the drilling fluid and the outlet pressure thereof, wherein regulating the level of the drilling fluid, and the outlet pressure of the drilling fluid, in said sealing and pressure-regulating device 16 , is accomplished by conducting the drilling fluid through said outlet passage in said sealing and pressure-regulating device ( 16 ) to said pump module ( 18 ), and that the outlet pressure in said outlet passage is regulated on the basis of specific gravity of the drilling fluid and pressure effects from the surrounding seawater on the level of the drilling fluid, and pumping the drilling fluid up to the sea surface with the help of said pump module via an external return pipe ( 20 ).