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Figure 2.30 - Drilling from a floater. (Courtesy Vetco)
WELLHEAD SYSTEM
The subsea wellhead system run by the drilling vessel prior
to installing the TLP is an 18-in., 10,000-psi WP system (Fig.
2.31), modified to accommodate the tieback system. The wellhead
housing is a standard extra- long type except that the landing ring
has been moved down so more of the housing is exposed when it
lands inside the 30-in. housing. The 18-in. x 13-in. casing hanger
inner profile is the same as a standard 163/4-in. x 13-in. casing
hanger, which allows the same running tool to be used for both the
183/4-in. floater-drilled and 16-in. TLP-drilled wells.
DRILLING RISER SYSTEM
Drilling with a surface BOP and high-pressure riser is a
reversal of the standard techniques used in drilling from a floating
drilling vessel. With this arrangement, a smaller, less complex
BOP at the surface can be maintained and operated more easily.
The high-pressure drilling riser assembly is essentially an
extension of the BOP, designed to withstand the maximum
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