in between outer wall surface 39 of expandable casing and the inner wall surfaces of upper and lower retainer rings 56 58 defined by the inner diameters of upper and lower retainer rings 56 58 due to the compression of sealing element 51 between outer wall surface 39 of expandable casing 30 and the inner wall surfaces of upper and lower retainer rings 56 58 the center portion of sealing element 51 is extruded outwardly in between upper and lower retainer rings 56 58 upper end 52 of sealing element 51 is extruded outwardly above upper retainer ring 56 and lower end 54 of sealing element 51 is extruded outwardly below lower retainer ring 58 until all three portions of sealing element 51 form a seal against inner wall surface 22 of well 20 the distance between the outer diameter of upper and lower retainer rings 56 58 and inner wall surface 22 of well 20 is referred to as the extrusion gap referring now to fig2 3 in another embodiment expandable casing 130 has upper end 132 lower end 134 bore 136 defined by inner wall surface 138 outer wall surface 139 and axis 140 expandable casing 30 includes run in diameter defined by run in radius 142 fig2 and set diameter defined by set radius 144 fig3 run in radius 142 and thus the run in diameter is less than set radius 144 and thus the set diameter expandable casing 130 is radially expanded using a cone not shown or other device used to expand expandable casing 130 from the run in diameter defined by run in radius 142 to the set diameter defined by set radius 144 in the same manner as the embodiment discussed above with respect to.