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from the well under all drilling conditions. When the drill string is
in the hole, movement of the pipe without releasing the well
pressure should be allowed to occur. In addition, the BOP stack
should allow fluid circulation through the well annulus under
pressure. These objectives usually are accomplished by using
several ram preventers and one annular preventer (Fig. 12.1).
Figure 12.1 – Stack of blowout preventers
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