Delayed opening port assembly

A port assembly usable in a port sub having a wall with an inner surface defining an inner bore, an outer surface, and a flow port defined in the wall and extending between the inner surface and the outer surface, the port assembly comprising:

• a first burst disk for placement adjacent to the inner surface and having a first burst disk outer surface facing away from the inner bore;
• a dissolvable barrier adjacent to but spaced apart from the first burst disk outer surface to define a cavity therebetween, the dissolvable barrier having defined therein a plurality of thinner areas in the dissolvable barrier,
• wherein at least a portion of the port assembly is positionable in the flow port to block fluid flow therethrough when the first burst disk and dissolvable barrier are intact, and when the first burst disk is ruptured and the dissolvable barrier is broken through at at least one of the plurality of thinner areas, fluid is permitted to flow through the ruptured first burst disk and broken dissolvable barrier.