Patent EA-001687-B1 (EA)
Title: Method for creating a zonal isolation in underground well system
Inventor: CUMMING FRANSIS ALEXANDER
IPC: E21B41/00
Filed: 1998-07-31
Abstract: 1. A method of creating zonal isolation in an underground well system (1) between an uncased section (6,18) which is located adjacent to a well section in which a well casing (3,10/16) is present, the method comprising the steps of inserting an expandable steel tubular (5,12,21) through the existing well casing (3,10,16) into said uncased section (6,18) of the underground well system such that one end of the expandable tubular protrudes beyond the well casing into the uncased section of the well system and another end of the expandable tubular is located inside the well casing (3,10,16), wherein the method further comprising the step of expanding the expandable tubular (5,12,21) using an expansion mandrel (7,22) having a conical surface, characterised in that the expandable tubular (5,12,21) is made of a formable steel grade and is expanded by an expansion mandrel (7,22) having a conical ceramic surface such that said one end is pressed towards the wall of the uncased section (6,18) of the well system (1) and the outer surface of said other end is pressed against the inner surface of the well casing (3,10,16) thereby creating an interference fit capable of achieving a shear bond and a hydraulic seal between said surrounding surfaces. 2. The method of claim 1, wherein a gasket material is inserted between said surrounding surfaces before expanding the tubular (5,12,21). 3. The method of claim 1, wherein the uncased section (6) of the underground well system (1) is formed by an  extension of a wellbore which extends axially beyond the well section in which the well casing is present (3,10). 4. The method of claim 1, wherein the uncased section of the underground well system is formed by a lateral borehole (18) that extends laterally from the well section (15) in which the well casing (16) is present through an opening (20) in the tubular wall of the well casing (16) and one end of the expandable tubular (21) is inserted through said opening (20) into the lateral borehole (18) such that the other end of the expandable tubular still extends into the well section (15) in which the well casing (16) is present such that said other end is substantially co-axial to the well casing (16) and the expandable tubular (21) is subsequently expanded such that said one end is pressed towards the wall of the lateral borehole (18) and said other end is pressed against the inner surface of the well casing (16). 5. The method of claim 4, wherein after expansion of the tubular (21) an opening is created in the wall of the expanded tubular (21) to provide fluid communication between the parts of the well section (15) in which the well casing (16) is present above and below the lateral borehole (18). 6. The method of claim 5, wherein said opening is created by milling a window in the wall of the expanded tubular (18). 7. The method of claim 1, wherein the tubular (5,12/21) is made of a high-strength low-alloy (HSLA) steel having a yield strength-tensile strength ratio which is lower than 0.8 and a yield strength of at least 275 MPa. 8. The method of claim 1, wherein the conical ceramic surface of the expansion mandrel (7,22) has a semi-top angle (A) between 20 degree  and 30 degree .