High pressure interventionless borehole tool setting force

A high pressure compressed gas source is separated from an actuation piston by a pilot valve that is selectively operated with raising annulus pressure to break a rupture disc to provide access to a shuttle type valve. Movement of the shuttle valve using pressure applied to opposing pistons of different sizes connected to a common shaft translates the shaft against a spring bias to open the valve on the high pressure source. This allows the high pressure to reach the actuating piston to operate the tool. One application can be setting a packer without well intervention.