Patent ID: 9631447
Date: 2017-04-25
CPC Classifications: E21B

Claim:
1. A method of removing casing from a well, in which an annulus between the outside of the casing and the inside of a surrounding downhole body is at least partially filled by a viscous and/or solid mass, the method comprising: (A) setting a first sealing element into fluid-sealing engagement with the inside of the casing at a first depth in the well; (B) lowering a string into the well, a cutting tool and a second, reversibly expandable sealing element being connected to the string, and the string being arranged to carry a fluid; (C) forming perforations into the casing with said cutting tool at a second depth in the well which is smaller than the first depth at which the first sealing element is set into fluid-sealing engagement; (D) expanding the second, expandable sealing element into fluid-sealing engagement with the inside of the casing at a third depth in the well which is smaller than the second depth at which the perforations were formed, so that the perforations will be located between the first and second sealing elements in the well; (E) passing the fluid at high pressure through the string and into the annulus via the perforations so that the viscous and/or solid mass is displaced up the annulus, circulated out of the well and substantially replaced by the fluid, the fluid having a lower specific weight than the viscous and/or solid mass; (F) cutting the casing around its entire circumference at a fourth depth, down to which the surrounding viscous and/or solid mass has substantially been replaced by the fluid; and (G) pulling a length of the casing up from the well.