Apparatus and method for temporarily plugging a tubular

摘要

An apparatus and method for controlling the pressure at which a fluid is introduced into a well penetrating a subterranean formation. The apparatus comprises a blow out sub having a sealed chamber between two plugs. The chamber is filled with a fluid at a known pressure. Thus, the pressure required to release the first plug is independent of the pressure in the well below the sub. The sub is attached to a tubular and positioned within the well. The first plug is then released upon application of a predetermined pressure fluid pressure, and the second plug is released upon application of a lesser pressure. The blow out sub may additionally comprise a tube forming a channel through the first plug, the chamber, and the second plug, with a means for controlling fluid flow through the channel. A first fluid may be introduced into the well via the channel prior to releasing the first plug.