| 摘要 |
<p>A dual flapper valve assembly (10A, 10B) 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 (10A, 10B) can be closed and have frangible closure plates 70A and 70B which can be fracture 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 (70B) of the lower flapper valve (10B) is propped open by a wash pipe (46T) during the gravel pack operation. The lower closure plate (70B) is fractured to accommodate a well logging operation, while the closure plate (70A) of the upper flapper valve (10A) is held open by a prop sleeve (100). Upon completion of the well logging operation, the prop sleeve (100) is retracted out of engagement with the closure plate (70A) of the upper flapper valve (10A), thereby permitting the upper flapper valve to close. The heavy completion fluid remaining in the upper well bore annulus (42) is thereby conserved and can be recovered to the surface, while the gravel pack and the formation (48) are protected from the pressure of the heavy completion fluid. After recovery of the completion fluid, the closure plate (70A) of the upper flapper valve (10A) is fractured to accommodate production operations. <IMAGE></p> |
