Method and device for pressure regulation of a well

Abstract

A method for the pressure regulation of a well (1) extending into a well formation (2) and being drilled from a drilling vessel at sea, the well (1) including a blowout preventer (10) on the seabed (12) and a riser (14) extending from the blowout preventer (10) up to the vessel, and the return path (8, 14, 20) of a drilling fluid (24) being provided with a rotatable surface seal (22) sealingly surrounding a drill string (4), the rotatable surface seal (22) being arranged to seal against a pressure difference between the surroundings and the return path (8, 14, 20), and there being arranged, at the rotating surface seal (22), a closable drilling-fluid outlet (28), the method including: arranging a pump inlet (32) from the return path (8, 14, 20) under water; connecting a pump (30) to the return path (8, 14, 20), the pump (30) being connected to a pressure pipe (34) discharging on the vessel; monitoring the drilling-fluid pressure; and controlling the pumping rate through the pump (30) to maintain a substantially constant drilling-fluid pressure at the well formation (2), both when drilling fluid (24) is flowing and when it has been stopped.

Dependencies are inferred from the claim text.