Definition
A Riser is a pipe carrying up the subsea oil and gas from the wellheads on the seabed to the floating unit on the surface.
The risers may be used for drilling or production purposes.
Comments
Drilling risers are categorised into two types:
– Marine drilling risers used with subsea blow out preventer (BOP) and generally used by floating drilling vessels
– Tie-back drilling risers used with a surface BOP and generally deployed from fixed platform or very stable floating platforms like a SPAR or Tension Leg Platform (TLP)
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 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.
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.
