Abstract

The time required for establishing a multilateral well is reduced by enlarging a section of a wellbore and running a multilateral tool into the enlarged wellbore section. The multilateral tool, which is suitable for running into a wellbore on a primary casing string, includes a preassembled combination of casing sections that are used to form dual casings strings extending from the primary casing. The multilateral tool incorporates three casing sections, which maintain the diameter of the primary casing, including: a carrier section, a lateral section, and a main section. In use, the tool is run with the lateral section releasably held in coaxial alignment within the carrier section, and with the main casing section fixed to the lower end of the carrier section. Once in place in the enlarged section of the wellbore, the lateral section is released and diverted out of a preformed window in the lower end of the carrier section and runs generally parallel to the main casing section. In this manner a lateral junction is formed at the carrier casing window in which dual casing strings are connected to the primary casing. A second window, which is preformed in the upper end of the lateral section is aligned with the bore of the primary casing when the lateral casing section is fully extended out of the carrier section window, thus permitting recovery of a diverting device incorporated in the carrier casing section through the second window. The dual strings are then individually drilled and completed to target locations with pressure integrity between the dual strings maintained by using straddle equipment across the lateral junction.