| 摘要 |
In common with conventional testing tools for this purpose, the present tool incorporates a central mandrel carrying a pair of vertically spaced packers which are expandable by fluid pressure, which mandrel forms a longitudinal bore having an outlet communicating with the annular space between the packers. In contradistinction to the prior tools, the bow spring and slips suspending assembly of the prior tools has been eliminated. Instead, the packers themselves are relied on to suspend or fix the tool in the tubing. To achieve this end, a novel valve assembly has been provided to control the admittance and bleeding off of pressurized fluid into the annular space. The valve assembly is adapted to first admit pressurized fluid into the annular space to set the packers and pressure test the tubing wall between the packers at relatively high pressure, for example 5000 psi. The valve assembly is further adapted to cooperate in bleeding off the pressure from the annular space until it just exceeds that amount required to hold the packers set, say 600 psi; the valve assembly then automatically closes, to trap the 600 psi pressure in the annular space so that the packers maintain the tool in a suspended state. A second stand of tubing can then be added to the tested stand and lowered into the well bore until the second stand's upper end seats in the wellhead. A cable overshot is then used to open the valve assembly, to bleed off the 600 psi, following which the packers collapse and the tool can be retrieved.
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