Patent ID: 8220538
Filing Date: 2012-07-17
Classification: E21B

Abstract:
1. A plug comprising: a housing; at least two discs carried by the housing and of a brittle material that can be destroyed by mechanical stress; a gas-filled cavity between the at least two discs; wherein the gas-filled cavity is connected to a drainage channel and a closing device which is set up to open to release gas from the gas-filled cavity; wherein the gas-filled cavity comprises at least one break bar or at least one break bushing that is set up to crush at least one of the at least two discs; a shear pin that keeps the at least two discs apart, wherein the shear pin is adapted to be broken when a pressure difference across at least one of the at least two discs exceeds a certain value; and wherein, responsive to the shear pin breaking, a first disc of the at least two discs moves towards a second disc of the at least two discs.