Actuator for multilateral wellbore system

A well system, comprising:

• a primary wellbore that defines a casing exit;
• a secondary wellbore extending from the casing exit;
• and
• an isolation window assembly positioned within the primary wellbore, the isolation window including:
• a completion sleeve having a longitudinal axis, a bore, and a window extending at least partially along the longitudinal axis to provide access to the bore;
• an isolation sleeve positioned within the bore of the completion sleeve, the isolation sleeve being longitudinally movable within the bore to adjust a position of the isolation sleeve relative to the completion sleeve window for permitting or blocking access through the window into the bore;
• and
• an actuator operatively coupled to the isolation sleeve to longitudinally move the isolation sleeve within the bore.

A method, comprising:

• providing a casing that defines a casing exit and has a secondary wellbore extending from the casing exit;
• providing a completion sleeve having a longitudinal axis, a bore, and a window aligned with the casing exit, the window at least partially along the longitudinal axis to provide access to the bore;
• and
• moving an isolation sleeve axially within the completion sleeve to adjust a position of the isolation sleeve relative to the completion sleeve window for permitting or blocking access through the window into the bore via an actuator disposed within the wellbore.