| 摘要 |
An apparatus and method for cementing a well using concentric drill string, e.g., concentric drill pipe, concentric coiled tubing and the like is disclosed. Concentric drill string comprises an inner string and an outer string, formi ng an annular conduit therebetween. Cementing apparatus comprises an isolation cementing tool and a cementing flow control means. The isolation cementing tool has a center tube and an outer casing forming an annular conduit therebetween, and an expandable packer means surrounding the outer casing. The cementing flow control means has a center tube and an outer casing formi ng an annular conduit therebetween, and a plurality of check valves positioned in either the center tube, within the annular conduit between the inner tube an d the outer casing, or both.
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