Patent attributes
A piston initiator is used on an assembly having a milling tool and a whipstock for creating a sidetrack in a wellbore. A piston disposed in an uphole position in a bore of the milling tool seals the bore from communicating with the port. A line from the port can communicate pressure to components on the whipstock for initiating their activation. The piston is movable from the uphole position, but is held by a releasable connection configured to release the piston in response to a predetermined force from fluid flow in a downhole direction against an exposed surface area of the piston. An uphole shoulder in the milling tool prevents movement of the piston in an uphole direction so the piston does not stress the releasable connection in response to reverse fluid flow through the milling tool.
