Page 164 - Well Control for Completions and Interventions

156 Well Control for Completions and Interventions

Figure 4.12 Check valve.

the figure shown). Flow towards the well lifts the valve off seat. When
pumping stops, or if the direction of flow is reversed, the valve seats,
stopping backflow from the well. Modern valves normally have metal-to-
metal seats (Fig. 4.12).

4.7 ANNULAR PREVENTERS

The annular preventer, also called the bag preventer, or simply “the
bag,” is normally the first device to be closed in the event of a kick. The
principal advantage of the annular preventer is that it is designed to close
around any size of pipe, and can create a seal around some irregular and odd
shaped completion component. However, annular preventers have their lim-
its and will not seal around any of these items of completion equipment:
• Spent hollow carrier perforating guns.
• Slotted or pre-drilled liners.
• Sand control screens of any type.
• Completion tubing with external control lines or electric submersible
pump (ESP) cable.
• Severely corroded (holed) pipes.
Most annular preventers will seal even if no pipe is in the well,
although in some cases, this is not recommended by the manufacturers.
Typically, an annular preventer will hold about 50% of the working pres-
sure when closed on open hole. Annular preventers also allow pipe to be
stripped into the well under pressure.