SEGMENTED COLLAPSIBLE BALL SEAT ALLOWING BALL RECOVERY

摘要

A series of ball seat assemblies preferably used to open a series of sliding sleeves for formation access to a zone that is to be fractured allows sequential shifting of the sleeves with a single ball. The ball is guided by a tapered member with a lower outlet larger than the ball. The ball lands on the segments that are initially supported. Some leakage occurs between the segments but not enough to prevent pressure buildup to shift the sleeves. The tapered member closely fits to the segments to minimize leakage. Shifting the segments axially allows them to retract so the ball passes to eventually land on a non-leaking seat so that the zone can be fractured. The ball is recovered at the surface after passing the retracted segments and going through the undistorted opening in the tapered member.