Downhole riser assembly

Patent · Tue Dec 23 04:00:00 EST 1980

OSTI ID:6569892

Dareing, D W

A downhole riser assembly includes a tubular casing embedded in the ocean floor, said casing having a constant internal diameter and an upper end extending above said ocean floor. A tubular riser pipe is disposed in the casing and has an upper end connected to a floating vessel which may be a tension leg platform. The casing and riser are rigidly connected at a considerable distance below the ocean floor, said distance being on the order of 100 feet. When the floating structure is laterally displaced from a position directly above the casing, the riser pipe contacts the upper end of the casing. This contact limits the lateral deflection of the riser at the ocean floor and thereby limits the stresses in the riser. The distance between the upper end of the casing and the downhole connection between the casing and the riser, and the diameter of the casing are such that the riser has a rotational stiffness, adjacent the upper end of the casing, within a range such that both a maximum design maximum stress and a maximum design bottom slope of said riser are not exceeded when said riser is subjected to maximum design loading conditions. An alternative embodiment of the present invention provides a lateral support means for connecting the riser and the casing adjacent the upper end of the casing for restricting lateral movement of the riser.

• Assignee: Conoco Inc
• Patent Number(s): US 4240506
• OSTI ID: 6569892
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420206* -- Engineering-- Mining & Drilling Equipment & Facilities-- (1980-1989)
423000 -- Engineering-- Marine Engineering-- (1980-)
DESIGN
LEVELS
MARINE RISERS
OFFSHORE PLATFORMS
PIPES
TUBES
UNDERWATER