Drilling fluid bypass for marine riser
AssigneeStandard Oil Company (Indiana)
InventorPierre A. Beynet
Life of this patent
Estimating the term…
Abstract
Method and apparatus are described to reduce the tension required on a riser pipe used in offshore drilling between a floating vessel and a subsea wellhead. Heavy drilling fluid is circulated down a drill pipe and up the annulus between the drill pipe and the borehole wall to a point just above a subsea wellhead. From this point, a separate drilling fluid return conduit extends to the floating vessel. Means are provided to maintain a constant level of an interface between the heavy returning drilling fluid and the lightweight fluid which can be confined within the riser pipe.
Claims18
A method of drilling a subsea well from a vessel floating on a body of water in which a drilling fluid is circulated down a drill pipe through a drill bit and returned up the annulus between a drill string and the borehole wall, the improvement which comprises:
- providing a riser pipe from said wellhead to said vessel,
- maintaining a lightweight fluid in said riser on top of the drilling fluid in said annulus, said lightweight fluid having a density less than said drilling fluid
- maintaining a selected pressure on said lightweight fluid by use of pressure generating means;
- and
- connecting the annulus below said lightweight fluid to a return conduit extending to said vessel.
A drilling system in which a subsea well is drilled from a floating vessel by circulating a drilling fluid down a drill pipe, the improvement which comprises:
- a riser pipe having a slip joint at its upper end and connected at its lower end to said subsea well;
- tensioning means supporting the top of said riser pipe in said vessel;
- a seal sealing the annular space between said drill pipe and the internal side of said riser pipe below said slip joint;
- a return conduit exterior said riser pipe and extending from the interior of the lower end of said riser pipe to said vessel;
- a lightweight fluid in said annular space below said seal;
- pump means to maintain said lightweight fluid under pressure;
- and
- a pump in said return conduit.
A method of drilling a subsea well from a vessel floating on a body of water in which a drilling fluid is circulated down a drill pipe through a drill bit and returned up the annulus between the drill string and the borehole wall, the improvement which comprises:
- providing a riser pipe from said wellhead to said vessel;
- maintaining a lightweight fluid in said riser on top of the drilling fluid in said annulus, said lightweight fluid having a density less than said drilling fluid;
- connecting the annulus below said lightweight fluid to a return conduit extending to said vessel;
- providing an interface detector between said drilling fluid and said lightweight fluid and controlling the pumping of drilling fluid to the vessel external of said riser in response to the output of said interface detector.
A drilling system in which a subsea well drilled from a floating vessel by circulating a drilling fluid down a drill pipe, the improvement which comprises:
- a riser pipe having a slip joint at the upper end and connected at its lower end to said subsea well;
- tensioning means supporting the top of said riser pipe to said vessel;
- a seal sealing the annuluar space between said drill pipe and the internal side of said riser pipe below said slip joint;
- a return conduit exterior of said riser pipe and extending from the interior of the lower end of said riser pipe from said vessel;
- a lightweight fluid in said annular space below said seal;
- a pump in said return conduit;
- level control sensors to determine the interface between said lightweight fluid and said circulating drilling fluid;
- and
- means to control said pump and said return conduit in response to said detected interface.
A drilling system in which a subsea well is drilled from a floating vessel by circulating a drilling fluid down a drill pipe, the improvement which comprises:
- a riser pipe having a slip joint as its upper end and connected at its lower end to said subsea well;
- tensioning means supporting the top of said riser pipe to said vessel;
- a return conduit exterior said riser pipe and extending from the interior of the lower end of said riser pipe to said vessel;
- a lightweight fluid in said annular space above said drilling fluid;
- a pump in said return conduit;
- means to maintain the upper level of said lightweight fluid at a selected elevation.
A method of drilling a subsea well from a vessel floating on a body of water in which a drilling fluid is circulated down a drill pipe to a drill bit and returned up the annulus between a drill string and the borehole wall, the improvement which comprises:
- providing a riser pipe from said wellhead to said vessel;
- maintaining a lightweight fluid other than air in said riser on top of the drilling fluid in said annulus;
- said lightweight fluid having a density less than said drilling fluid;
- and
- connecting the annulus below said lightweight fluid to a return conduit extending to said vessel.
Dependencies are inferred from the claim text.