The extension of the wellbore from the subsea BOP stack to the drilling vessel. The riser provides for fluid returns to the drilling vessel, supports the choke, kill, and control lines, guides tools into the well, and serves as a running string for the BOP stack.

Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global Standards



Vertical pipe intended to move fluid to either a higher or a lower elevation, such as from the ocean floor to a platform.

Source: IADC UBO / MPD Glossary, December 2011. Global Standards



Piping connecting the process facilities or drilling equipment on the floating structure with the subsea facilities or pipelines, or reservoir. NOTE 1 Possible functions include drilling and well intervention, production, injection, subsea systems control and export of produced fluids. NOTE 2 Adapted from ISO 19900:2002, definition 2.29.

Source: ISO 19901-7:2013, Petroleum and natural gas industries – Specific requirements for offshore structures – Part 7: Stationkeeping systems for floating offshore structures and mobile offshore units. Global Standards



tubular used for the transport of fluids between the sea floor and a termination point on the platform

Note 1 to entry: For a fixed structure, the termination point is usually the topsides. For floating structures, the riser can terminate at other locations of the platform.

Source: ISO 19900:2013, Petroleum and natural gas industries – General requirements for offshore structures. Global Standards 



A subsea flexible hose or rigid pipe leading down from the connection on the unit to a sea bed termination structure. Risers may have a variety of functions including liquid and gas export, water injection, chemical injection and controls, etc.

Source: Rules and Regulations for the Classification of Mobile Offshore Units, Part 3, Functional Unit Types and Special Features, June 2013, Lloyd’s Register, Global Standards

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