| 摘要 |
<p>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 (34) between two plugs (18, 26). The chamber is filled with a fluid at a known pressure. Thus, the pressure required to release the first plug (18) 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 (26) is released upon application of a lesser pressure. The blow out sub may additionally comprise a tube (152) forming a channel through the first plug (118), the chamber (134), and the second plug (126), with a means (154, 156) 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 (118). <IMAGE></p> |
