| 摘要 |
A downhole centraliser apparatus comprises a swellable member 12 which expands upon contact with at least one predetermined fluid and a rigid assembly 14. In a first condition of the apparatus, before expansion of the swellable member, the rigid assembly defines a maximum outer diameter of the apparatus. In a second condition after expansion of the swellable member, the swellable member defines a maximum outer diameter of the apparatus. The maximum outer diameter defined by the rigid assembly may be selected to be not less than the drift diameter of a borehole in which the apparatus is to be located. In this arrangement the rigid assembly provides maximum stand-off, and the swellable member may provide isolation after expansion. In a preferred embodiment the rigid assembly is designed to flex or deform under an axial or radial load. |
