Drillable window assembly for controlling the geometry of a multilateral wellbore junction

A method for forming a multilateral well, comprising:

• placing a drillable window assembly within a main wellbore located in a subterranean formation, the drillable window assembly including;
• a first precut casing joint, the first precut casing joint including a first casing tubular having two or more radially offset slots along an interior surface thereof, wherein the two or more radially offset slots are positioned equidistance around the first casing tubular;
• a second precut casing joint coupled to the first precut casing joint, the second precut casing joint including a second casing tubular having a sidewall opening formed therein;
• and
• an outer sleeve surrounding the sidewall opening in the second casing tubular;
• running an exit assembly downhole toward the drillable window assembly, the exit assembly including a tubular defining a central axis, two or more radially offset keys along an exterior thereof and a drill bit coupled to a downhole end thereof;
• rotating the exit assembly within the drillable window assembly until the two or more radially offset keys latch with the two or more radially offset slots in the first casing tubular;
• and
• rotating the drill bit of the exit assembly along the sidewall opening in the second casing tubular while the two or more radially offset keys are latched with the two or more radially offset slots to form a lateral wellbore in the subterranean formation.

A multilateral well, comprising:

• a main wellbore;
• a lateral wellbore extending from the main wellbore;
• and
• a drillable window assembly positioned at a junction between the main wellbore and the lateral wellbore, the drillable window assembly including;
• a first precut casing joint, the first precut casing joint including a first casing tubular having two or more radially offset slots along an interior surface thereof, wherein the two or more radially offset slots are positioned equidistance around the first casing tubular;
• a second precut casing joint coupled to the first precut casing joint, the second precut casing joint including a second casing tubular having a sidewall opening formed therein;
• and
• an outer sleeve surrounding the sidewall opening in the second casing tubular.