| 摘要 |
<p>Preferably installed in the well head, the valve incorporates a differential pressure-operated piston exposed to a fluid pressure supply on one side for maintaining the valve in an open condition when desired and exposed to subterranean pressures on the opposite side, so that when the subterranean pressure rises above a predetermined amount the valve closes. The valve may be economically installed in existing wells, e.g. offshore dual wells on multiple well platforms to provide internal blowout and anti-fire protection for wells which presently have no effective positive closure for shutting in the well in an emergency, such as an incipient blowout or a fire.</p> |
