| 摘要 |
<p>A disaster valve in a well prodn. string above a packer has a valve sleeve whose central passage is closed by a removable plug allowing the sleeve to be urged upwards to a closed position by prodn. fluids acting against a pressurized liquid column above the plug. A pilot valve responsive to prodn. press. and to the control pressure maintained on the liquid column acts to remove the control pressure, when it is exceeded by the prodn. press. thereby allowing the sleeve to move to its closed position.</p> |
