| 摘要 |
A collar (500) for injecting fluid, such as a formation treating fluid, into a wellbore, and a method for using same. The collar is disposed between the upper and lower packing elements (40, 41) of a pack-off system during the treatment of an area of interest within a wellbore. The collar first comprises an inner mandrel (550) running essentially the length of the collar. The inner bore of the collar is in fluid communication with the annular region between the collar and the surrounding perforated casing by a set of actuation ports (552). A second set of ports (554), known as frac ports, is disposed within the mandrel. In accordance with one aspect of the invention, the collar further comprises a tubular case which substantially seals the frac ports in a first position, and slidably moves along the outer surface of the mandrel in order to expose the frac ports in a second position. In operation, the upper and lower packing elements are set at a first fluid pressure level. Upon application of a second greater fluid pressure level, the upper and lower packing elements are further separated in accordance with a designed stroke length, thereby exposing the frac ports.
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