Multiple casing segment cementing system

摘要

A system including method and apparatus for placing and cementing a plurality of scab liners as well as a surface liner in a well with one placement. A duplex assembly is created using a lower duplex tool having a duplex shoe with a valve assembly positioned in the duplex tool. A scab casing is fixed to the duplex tool and drill pipe extends into the scab casing to mate with the valve assembly. A ratchet insures locking of the drill string. The valve assembly includes elements to control flow of cement to outwardly of the scab casing and the flow of flushing fluid inwardly of the scab casing. A locking mechanism using floating dogs controlled by a locking sleeve allows unlocking of the valve assembly from the duplex tool upon completion of the cementing and flushing operation. Similar operations are conducted in succeeding duplex assemblies upwardly along the string, each succeeding scab casing being cemented in turn. Once the cementing is complete, the string and valve assemblies are withdrawn from the well leaving liner segments cemented in place with drill-out duplex elements remaining.