Heavy seas influence riser designs

Journal Article · Tue Dec 01 04:00:00 EST 1981 · Offshore; (United States)

OSTI ID:5844180

Wolgamott, J; Steddum, R

The marine riser is the direct link betwen the drilling vessel and the ocean floor. With the expanded economic and political incentives for exploration, the search for hydrocarbons has been extended into increasingly hostile environments. These environments are imposing stresses that may exceed the design limits of an existing marine riser system. One situation that results in high stress is the storm hangoff of the riser and the lower marine riser package (LMRP). To prevent riser failure, the LMRP is unlatched and the riser is hungoff to ride out the storm. If a severe storm coincides with a high-velocity current, the resulting stresses could part the riser. The ideal solution to this problem is to avoid the costly purchase of an improved riser system, yet ensure the survival of the existing system subject to the severe environment loading. There are a few methods to reduce the stress level. One such method is to utilize the advantages of a variable buoyancy system. The two basic riser buoyancy systems are the fixed and variable concepts. Each concept is described. The marine riser is subjected to two stresses: axial compression and moonpool loadings. A variable buoyancy system on the bottom of the riser is the most desirable for the prevention of axial compression. To prevent moonpool loading, the riser's hanging weight should be increased, the hydrodynamic drag reduced, the riser physically restrained from contacting the side of the moonpool, and the riser dropped below the moonpool. A variable air-can buoyancy system remains the most practical method to increase the hanging weight of the riser. (DP)

• Research Organization: Offshore Co., Houston, TX
• OSTI ID: 5844180
• Journal Information: Offshore; (United States), Journal Name: Offshore; (United States) Vol. 41:14; ISSN OFSHA
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
423000* -- Engineering-- Marine Engineering-- (1980-)
COMPRESSION
DESIGN
ENVIRONMENTAL EFFECTS
MARINE RISERS
OFFSHORE OPERATIONS
PIPES
SEAS
STRESSES
SURFACE WATERS