| 摘要 |
A downhole wellbore tool has been developed which has a lower movable valve apparatus which, when it contacts a member in a wellbore or in a tubular in a wellbore, is moved to close off fluid flow through the item to which the valve apparatus is attached. In one aspect, such a valve apparatus is used below a mill above which is positioned a downhole motor which rotates the mill for milling. Actuation of the valve apparatus results in a cessation of the circulation of the motive fluid flowing to and through the motor so that milling stops. In one aspect the valve is selectively operable so that milling may be resumed. In another aspect such a tool is useful for indicating a known location in a wellbore when a decrease or cessation in fluid flow or a decrease in pressure is noticed at the surface.
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