METHOD OF FORMING A BORE

摘要

A method of forming a supported subterranean well bore in which, in one disclosed embodiment, a first drill bit is mounted on a first string of casing tubulars via a steerable tool, and the drill bit is used to form a first bore. Upon reaching the required depth the casing string is cemented in place to support the formed bore and a second drill bit is mounted on a second casing string and is inserted into the first casing string. The second drill bit is used to drill through the wall of the first casing string and proceed to form a second, deeper bore. Once the second drill bit has reached the required depth, the second casing string is cemented in place to support the second bore.

主权项

1. A method of forming a supported bore, said method comprising the steps of:
locating a first drill bit on a first expandable tubular member having an upper portion of a first diameter and a lower portion of a second, larger diameter, drilling a bore with the drill bit mounted on the first expandable tubular member, pumping cement into an annulus formed between the expandable tubular member and the wall of the bore; and expanding the upper portion of the tubular member to a third diameter, greater than the first diameter.