A drilling riser is a conduit that provides a temporary extension of a subsea oil well to a surface drilling facility. Drilling risers are categorized into two types: marine drilling risers used with subsea blowout preventer (BOP) and generally used by floating drilling vessels; and tie-back drilling risers used with a surface BOP and generally deployed from fixed platforms or very stable floating platforms like a spar or tension leg platform .
Marine Drilling Riser
A marine drilling riser has a large diameter, low pressure main tube with external auxiliary lines that include high pressure choke and kill lines for circulating fluids to the subsea blowout preventer (BOP), and usually power and control lines for the BOP. The design and operation of marine drilling risers is complex, and the requirement for high reliability means an extensive amount of engineering analysis is required.
Tie-back drilling rise
A tie-back riser can be either a single large-diameter high pressure pipe, or a set of concentric pipes extending the casing strings in the well up to a surface BOP.