Abstract: The present invention provides methods for forming multiple wellbores from a single location. A relatively large diameter main wellbore is drilled to a known depth. A plurality of spaced apart wellbores are formed from the bottom of the main wellbore, wherein at least one such wellbore is a production wellbore for producing hydrocarbons from subsurface formations. Wellhead equipment for each production wellbore is installed at main wellbore bottom. Additional devices or equipment are also placed in the main wellbore, preferably near the bottom.

Abstract: Junctions in multilateral well structures are sealed by employing a variety of degrees of premachined components and a variety of sealing embodiments, including casing segments having premachined windows, side pocket members which are adapted to reside within the string during run in and move laterally to the deployed position, woven members, cement filled ECPs, etc. Also disclosed is a downhole milling device which cuts a window in a casing segment or other material based upon a predetermined geometric pattern imposed upon the cutting tool by an integral template.