| 摘要 |
<p>A dual flapper valve assembly permits a well logging operation to be carried out after a gravel pack has been deposited without losing a large amount of completion fluid into the formation. The dual flapper valves can be closed and fractured independently of each other and selectively to accommodate a gravel pack operation, a well logging operation and a completion fluid recovery operation. The closure plate of the lower flapper valve is propped open by the wash pipe during the gravel pack operation. The lower closure plate is fractured to accommodate a well logging operation, while the closure plate of the upper flapper valve is held open by a prop sleeve. Upon completion of the well logging operation, the prop sleeve is retracted out of engagement with the closure plate of the upper flapper valve, thereby permitting the upper flapper valve to close. The heavy completion fluid remaining in the casing annulus is thereby conserved and can be recovered to the surface, while the gravel pack and the formation are protected from the pressure of the heavy completion fluid. After recovery of the completion fluid, the closure plate of the upper flapper valve is fractured to accommodate production operations.</p> |
