| 摘要 |
<p>A seal is formed in a tubular casing (132.1) by means of a mandrel (134.1) comprising two axially displaceable sections (136) and (138) and an annular sealing sleeve (158.1) monted thereon. The upper section (138) is locked to the tubular member by segmented slips (140) and the lower mandrel section (136) is then raised to provide an axial compressive force on the sleeve (158.1), thus causing radial expansion of the sleeve to provide a desired sealing engagement with the inner surface of the tubular member (132.1). To prevent extrusion of the sleeve (158.1) into the gap between the mandrel sections and the tubular member, the sleeve is fitted at each end with an anti-extrusion member in the form of a helical member (111) and the axial compression of the sleeve causes radial expansion of the helical members (111) so that they come into abutment with the inner surface of the tubular member (132.1), thereby sealing the annular gap between the mandrel sections (136) and (138) and the inner surface of the tubular member (132.1) and thus preventing axial extrusion of the sleeve. This permits recovery and multiple re-use of the apparatus without requiring replacement of the sleeve.</p> |
