Clamp for control umbilical and workstring for offshore oil well

A clamp 1 clamps a first conduit, for example a workstring, pipe or guidewire, to a second conduit, for example a control umbilical. Clamp 1 has a first bore 20 gripping the first conduit, preferably parallel to a second bore 60 gripping the second conduit. Bores 20, 60 may be internally grooved (70, Figure 8a). Clamp 1 comprises at least two releasably securable parts 30, 40 gripping at least one conduit. Preferably a hinge 100 connects parts 30, 40. Centralising fins 140, which may have handle recesses 190, may be provided to allow alignment of clamp 1 within a riser. Clamp 1 is preferably buoyant and manufactured from a polymeric material. Inserts (160, Figure 8a) may be provided to adjust the diameters of bores 20, 60. End portions 170, 180 of the clamp may have truncated dome-shaped tapered sections. A conduit system and method of use are also provided.