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US 6,276,456 B1Granted
Riser system for sub-sea wells and method of operation
OwnerPhilip Headinventor
Life of this patent
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OwnerPhilip Headinventor
Estimating the term…
A riser system connecting a oil or gas well head and a surface vessel comprises a first riser section maintained substantially vertically under tension, attached for example by a tension cable to a constant load tensioner means mounted on the vessel, and a flexible second riser section arranged above the first riser, the second riser being able to flex to accommodate movements in the surface vessel. The second riser section includes a curvature limiter, achieved for example by making the riser from a material of variable stiffness along the riser's length. An emergency disconnect valve is provided between the lower riser section and the upper flexible section. An alternative curvature limiter comprises a plurality of discrete collars which are connected together and surround the outer diameter of the second riser.
An offshore oil or gas well riser system which forms a connection between the well head and a surface vessel, the riser system comprising a first riser section which extends substantially vertically and is maintained vertically under tension, and a second riser section which is flexible and is arranged above the first riser section and flexes to accommodate movements in the surface vessel, the second riser section including a plurality of curvature limitation means to limit the extent of the curvature of the second riser section, the curvature limitation means having two states, a first state in which the second riser section is permitted to bend to be wound on a reel and a second state in which the second riser section is permitted to bend to a lesser extent and within its elastic limit.
A method of installation of a well riser system which comprises the steps of;
A method of passing long objects through a riser system which comprises a connection between a well head and a surface vessel, the riser system comprising a first riser section which extends substantially vertically and is maintained vertically under tension, and a second riser section which is flexible and is arranged above the first riser section and flexes to accommodate movements in the surface vessel, the second riser section including a curvature limitation means which limits the extent of the curvature of the second riser section, the curvature limitation means having two states, a first state in which the second riser section is permitted to bend to be wound on a reel and a second state in which the second riser section is permitted to bend to a lesser extent and within its elastic limit, the method comprising the steps of:
Dependencies are inferred from the claim text.