Page 56 - Air and gas Drilling Field Guide 3rd Edition
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3.3 Wellhead Equipment 47
BEARING & SEALS
FIGURE 3-10. Cutaway view of a rotating head with dual stripper rubbers (courtesy of
Weatherford International Ltd).
These are deep water well, deep monitoring well, deep mining borehole, and
deep geotechnical borehole drilling operations where double and triple drilling
rigs are required. These rotating heads are used to keep air or gas (in this case
nitrogen) flow with entrained rock cuttings from flowing to the rig floor (for
direct circulation). However, many of these non-oil, natural gas, or geothermal
recovery drilling operations utilize reverse circulation. Reverse circulation
requires that the compressed air or gas be injected into the “outlet” of the rotat-
ing head to the annulus space of the borehole (see Figure 3-10). In this situation
the rotating head still keeps the air or gas from flowing to the rig floor.
