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US 4,176,986 AGranted
Subsea riser and flotation means therefor
AssigneeExxon Production Research Company
InventorsDaniel G. Taft, Joe K. Heilhecker
Life of this patent
Estimating the term…
Abstract
A marine drilling riser is provided with a plurality of buoyancy cans having fail safe dump valves operative to vent compressed gas from the buoyancy cans and thereby cause rapid loss of buoyancy.
Claims22
A buoyancy can for use on a self-standing riser at subsea depths having a slip joint in the upper portion thereof, said buoyancy can comprising:
- (a) a housing defining a buoyancy chamber adapted to receive a compressed gas, said housing having a port formed in an upper portion thereof providing fluid communication between said buoyancy chamber and the exterior of said housing, said port having a flow area of sufficient size to enable venting of compressed gas from said chamber upon disconnection of said riser before the buoyancy of said can extends said slip joint to its upper limit;
- (b) a fail-safe valve member positioned within said housing, said valve member having a biasing means to bias said valve to a first position wherein said port is open and said valve being movable to a second position wherein said port is closed, said valve member in the open position permitting the equalization of pressure between said chamber and ambient pressure opposite said port;
- and
- (c) a closing means capable of moving said valve to said second position, said closing means becoming inoperable upon disconnection of said riser to enable said biasing means to move said valve to said first position.
1 more element
A riser system for conducting offshore drilling operations from a drilling vessel, said riser system comprising
- (a) a riser which extends from the vessel to a wellhead on the seafloor;
- (b) a plurality of buoyancy cans spaced along said riser, each of said buoyancy cans having a port formed therein and including
- (i) a gas inlet for receiving gas into each buoyancy can,
- (ii) a valve member for closing said port, said valve member biased away from said port, a hydraulic pilot valve connected to said dump valve and being operative to move said valve member to close said port in response to the delivery of a predetermined hydraulic pressure to said pilot valve, said valve member being moveable to its normally open position in response to loss of said predetermined pressure delivered to said pilot valve;
- (c) a gas line extending from said vessel to each gas inlet for introducing gas into each of said buoyancy cans;
- and
- (d) a hydraulic line extending from said vessel to each buoyancy can for delivery of hydraulic pressure to each of said pilot valves.
4 more elements
A marine riser having a buoyancy can mounted at a subsea depth, the improvement wherein said buoyancy can comprises:
- (a) a housing secured to said riser and defining a buoyancy chamber therein and having a port formed therein for venting gas from said buoyancy chamber;
- (b) means for introducing compressed gas into said can;
- (c) a valve member mounted in said chamber adjacent to said port, said valve member having first position wherein said port is closed and a second position wherein said port is open;
- and
- (d) a pilot valve having a first position where said pilot valve cooperates with said valve member to close said port and a second position where said valve member is movable to the second position wherein said port is open, said pilot valve having a hydraulic line with hydraulic pressure therein extending from the surface to said pilot valve, said hydraulic pressure being operative to move said pilot valve to said first position, said pilot valve having a biasing means to move said pilot valve to said second position when said hydraulic pressure is removed from said hydraulic line.
2 more elements
A buoyancy can for use at subsea depths which comprises:
- (a) a housing defining an internal gas buoyancy chamber;
- said housing having a port formed therein for venting gas from said buoyancy chamber;
- (b) a valve member mounted on an upper portion of said chamber adjacent to said port, said valve member being movable to close said port to retain gas in said chamber and being movable to open said port to vent gas from said chamber through said port into the surrounding sea;
- and
- (c) a pilot valve having a piston connected to said valve member and a hydraulic line having hydraulic pressure therein and extending from the surface to said piston, said pilot valve having biasing means for biasing said piston away from said valve member, said hydraulic pressure in said line urging said piston towards said valve member to cause said valve member to be moved to said closed position, said biasing means moving said piston away from said valve member with the loss of hydraulic pressure to enable said valve member to be moved to said open position.
2 more elements
A riser system for use in marine drilling, which comprises:
- (a) a riser;
- (b) a plurality of compressed gas buoyancy cans secured to the riser to provide a net positive buoyancy on the riser;
- (c) a normally open valve member mounted in each of said cans for releasing gas therefrom;
- and
- (d) hydraulic valve control means including a hydraulic pilot valve operatively connected to each of said valve members and a hydraulic line extending from the surface to each of said pilot valves, each pilot valve being operative to move said valve member to a closed position in response to delivery of a predetermined hydraulic pressure in said hydraulic line and being operative to enable said valve member to move to said open position in response to loss of said predetermined pressure in said hydraulic line, said cans being spaced along said riser such at least one valve member will move to the open position within one second from loss of said predetermined pressure of said hydraulic control means.
2 more elements
Dependencies are inferred from the claim text.