Page 59 - Air and gas Drilling Field Guide 3rd Edition

50 CHAPTER 3 Surface Equipment

FIGURE 3-11. Typical twin ram-type blowout preventer (courtesy of Bowen Tools,
Incorporated).

the well. These rams can be actuated manually or hydraulically. Figure 3-11 shows
the blind rams on the bottom that are set up to be actuated manually.
This twin ram-type blowout preventer is flange connected (made up) to the
top of the well casing. The bottom of the casing spool is threaded (or welded)
to the top of the casing. The top of the spool is flange connected to the bottom
flange fitting of the twin ram-type blowout preventer.
Figure 3-7 shows a Type 1 BOP stack that utilizes only the twin ram-type blow-
out preventer for well control. This BOP stack is fitted with a rotating head flange
connected to the top of the twin ram blowout preventer. This is the standard well
control setup for air or gas drilling operations directed toward the recovery of oil
and natural gas deposits with static bottom hole pressures of the order of 3000
2
psi (2069 N/cm ) or less. Figure 3-7 shows a Type 2 BOP stack that utilizes three
ram-type blowout preventers for well control. This BOP stack is configured with
two pipe rams on the top and a blind ram on the bottom. The two pipe rams allow
some flexibility in carrying out well control when drilling deep wells with a
tapered drill string and when placing a liner string in an air- or gas-drilled well. This
BOP stack is fitted with a rotating head flange connected to the top pipe ram blow-
out preventer. This stack can be configured for the recovery of oil and natural gas
2
deposits with static bottom hole pressures of up to 5000 psi (3449 N/cm ).
The annular-type blowout preventer can also be used in a BOP stack (see Type 3
in Figure 3-7). An annular preventer is operated hydraulically. Figure 3-12 shows
a cutaway view of a typical annular preventer. The closing of the preventer is
actuated by hydraulic pressure. This hydraulic pressure forces the operating pis-
ton upward against a pusher plate (see Figure 3-12). The pusher plate in turn
displaces (compresses) an elastomer donut inward to close and seal on the
outer surface of drill pipe, drill collar, casing, or liner. Utilizing an annular pre-
venter in conjunction with ram blowout preventers greatly increases well