METHOD OF CREATING A BOREHOLE IN AN EARTH FORMATION

摘要

An expansion assembly is provided for use in a method of creating a borehole in an earth formation, the method comprising the steps of a) drilling a section of the borehole and lowering an expandable tubular element into the borehole whereby a lower portion of the tubular element extends into the drilled borehole section, b) radially expanding said lower portion of the tubular element so as to form a casing in the drilled borehole section, and c)separating an upper portion of the tubular element from said lower portion so as to allow the separated upper portion to be moved relative to said lower portion. The expansion assembly is operable between a radially expanded mode in which the expansion assembly has a diameter larger than the inner diameter of the tubular element when unexpanded, and a radially retracted mode in which the expansion assembly has a diameter smaller than the inner diameter of the tubular element when unexpanded, and wherein the expansion assembly comprises actuating means for actuating the expansion assembly from the radially retracted mode to the radially expanded mode thereof so as to expand the tubular element when the expansion assembly is positioned in the tubular element.