Abstract: A protective arrangement or "junk bonnet" (30) for preventing debris entering a downhole tool assembly (14) employed in the drilling of a well. The junk bonnet (30) is in the form of an annular seal which fits around a tube (18) and inside a sleeve (24) which are relatively movable to operate a downhole tool assembly (14) of which they form part. The junk bonnet (30) is provided with sliding fluid seals (42, 44, 48, 50) which seal against the external surface (19) of the tube (18), and against the bore (25) of the sleeve (24). A longitudinal fluid passage (52) links opposite ends (54, 56) of the junk bonnet (30). The passage (52) is sealed in use by a plug (60) or other suitable valve. An annular volume ("C") below the junk bonnet (30), between the tube (18) and the sleeve (24), and above a seal (26) forming part of the downhole tool assembly (14) is filled through the passage (52) with hydraulic oil during setting-up and prior to closure of the passage (52) by the plug (60).

Abstract: A multi-string packer for anchoring two or more non-concentric through tubes inside a larger pipe or casing (e.g. in an oil well). The packer can be deployed downhole, set, unset, and reset at least once without being withdrawn to the surface, despite the shearing of shear elements on each such operation. A lost-motion mechanism isolates the shear elements for the first packer resetting (the second setting) from packer-setting shear forces applied to the shear elements for the first packer setting, to preserve the second setting shear elements until the packer is actually required to be set for a second time. Similarly, another lost-motion mechanism isolates to shear elements for the second packer unsetting from the packer-unsetting shear forces applied to the shear elements for the first packet unsetting, to preserve the second unsetting shear elements until the packer is actually required to be unset for a second time.