Radial expansion of tubular elements has been applied, for example, in wellbores whereby a tubular casing is lowered into the wellbore in unexpanded state through one or more previously installed casings. After the casing is set at the required depth, an expander is moved through the casing to radially expand the casing to an inner diameter which is about equal to the inner diameter of the previously installed casing. In this manner it is achieved that the inner diameters of subsequent casings are about equal as opposed to conventional casing schemes which have stepwise decreasing casing diameters in downward direction. For example, WO-A-93/25800 teaches expansion of a casing in a wellbore by a solid expansion mandrel, the mandrel being pulled through the tubular or hydraulically pushed through the casing.
Expansion of tubulars is discussed in, for example, U.S. Pat. No. 6,557,640, and published U.S. patent application Ser. No. 10/382,325, the disclosures of which are incorporated herein by reference.
Expandable expansion cones are suggested, for example, in U.S. Pat. No. 6,460,615 the disclosure of which is incorporated herein by reference. Expansion of a cone within a casing requires that the casing be expanded as the expansion cone is expanded. This requires considerably more force than the force needed to pull a mandrel through the casing once the cone has been expanded. Further, if the lower casing is to overlap the previously installed casing and the inside diameter of the final casing is to remain constant through the overlap section, then the overlap section of the upper casing needs to be expanded by more than the remainder of the casing. Some provision for this greater expansion also needs to be provided.
USPTO Backgrounds
USPTO Backgrounds