| 摘要 |
Blowout preventers (BOP) include a tubular shell which is insertable within, and thus contained by, an upper portion of the well casing. The tubular shell includes a removable inner sealing/pressure-reducing (SPR) assembly which provides for a high-pressure seal against the exterior surface of the drill stem as well as reducing the pressure of rising subterranean gas. The SPR assembly includes a channel passageway for the rising subterranean gas in which a series of longitudinally separated transverse orificed baffles is disposed. In this manner, the pressure of the subterranean gas flowing upwardly through the channel passageways will be reduced as the gas encounters the orificed baffles. A longitudinally separated pair of split sealing blocks is also preferably disposed within the sealing/pressure-reducing assembly. The SPR assembly also most preferably includes sealing blocks are mounted for reciprocal transverse movements towards and away from the central bore of the BOP so as to be capable of movements into and out of sealing relationship with an exterior surface of a well stem. A rotary actuator system operatively coacts with the sealing blocks in such a manner that rotary motion of the actuator system is controllably translated into reciprocal lateral movements of the sealing blocks. As a result of such sealing, subterranean gas will be caused to flow through the channels and thereby pressure-reduced.
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