| 摘要 |
A restrictor device (6) for controlling a return flow of drilling fluid from a borehole (51) where drilling fluid is provided from a surface installation (3) via a drill string (4) to a bottom-hole assembly (45), drill pipes (41) forming the drill string (4) being provided with pipe joints (42) including enlarged-diameter pipe portions (43), and where an annulus (22) is formed between a pipe, for example a marine riser (1), and the drill string (4), and where the annulus (22) is in fluid communication with or forms parts of a drilling-fluid flow path (23), and where the restrictor device (6) is arranged in the annulus (22), the restrictor device (6) being formed of a restrictor pipe (61) anchored to said riser (1) and surrounding at least one restrictor element (64) placed on an intermediate pipe portion (44) that connects two enlarged-diameter pipe portions (43), and the length (L) of the restrictor device (6) exceeding the largest distance (M) between two consecutive restrictor elements (64), the restrictor element (64) being a drill-pipe/casing protector (DPP) with an external diameter larger than a diameter of the pipe joints (42). |
