# US 4,400,110 A · Flexible riser underwater buoy

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- Number: US 4,400,110 A
- Document ID: US4400110A
- Status: Granted
- Kind: A
- Application number: 06/318,497
- Filed: 1981-11-05
- Granted: 1983-08-23
- Earliest claimed: 1981-11-05
- Assignees: Standard Oil Company (Indiana)
- Inventors: Pierre A. Beynet; Sam A. Billington
- Web page: https://patentgrep.com/patent/US4400110A

## CPC

- E21B 17/015: {Non-vertical risers, e.g. articulated or catenary-type}
- B63B 22/021: {and for transferring fluids, e.g. liquids (container type buoys having means to selectively release contents, not adapted for mooring a vessel B63B22/26)}
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- B63B: SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING (arrangements of vessel ventilation, heating, cooling, or air-conditioning B63J2/00; floating substructures as supports of dredgers or soil-shifting machines E02F9/06)

## Abstract

This invention relates to a floating production system for offshore development of oil and gas wells which employs an underwater buoy to decrease tension on flexible riser pipes used to connect a subsea pipeline to the floating vessel. The underwater buoy utilizes a cradle assembly having a drag balancing tail assembly to counteract the twisting moment applied to the cradle by current drag forces.

## Claims

### Claim 1

An underwater structure for supporting a flexible riser extending from the bottom of the body of water to a floating vessel comprising:
(a) a cradle assembly having:
(i) a cradle having a receiving surface over which said riser may extend;
(ii) a buoy attached to said cradle
(b) a drag balancing tail assembly attached to said cradle assembly to counteract the twisting moment applied to said cradle assembly by current drag forces.

### Claim 2 (depends on 1)

The structure as defined in claim 1 in which said drag balancing tail assembly has a neutral buoyancy in water.

### Claim 3 (depends on 1)

The structure as defined in claim 1 in which said drag balancing tail assembly includes a vertical open-ended cylinder having perforations in the walls thereof and an arm member connecting said cylinder to said cradle assembly.

### Claim 4 (depends on 3)

A structure as defined in claim 3 including means to sense the vertical orientation of said cylinder and the azimuth of said arm.

### Claim 5 (depends on 4)

A structure as defined in claim 4 including means to move said cylinder along said arm.

### Claim 6 (depends on 4, 5)

A structure as defined in claim 5 including transmitting means to transmit signals indicative of the vertical orientation and azimuth obtained in claim 4 to a remote spot and to control the activation of said cylinder from such spot.