Offshore drilling method
First Claim
1. A drilling method comprising the steps of:
- connecting an injection conduit externally to a riser string, so that the injection conduit is communicable with an internal flow passage extending longitudinally through the riser string;
installing an annular seal module in the flow passage, the annular seal module being positioned in the flow passage between opposite end connections of the riser string;
conveying a tubular string into the flow passage;
sealing an annular space between the tubular string and the riser string utilizing the annular seal module;
rotating a drill bit at a distal end of the tubular string, the annular seal module sealing the annular space during the rotating step;
flowing drilling fluid from the annular space to a surface location; and
injecting a fluid composition having a density less than that of the drilling fluid into the annular space via the injection conduit.
1 Assignment
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Accused Products
Abstract
An offshore universal riser system may include a valve module which selectively permits and prevents fluid flow through a flow passage extending longitudinally through a riser string. An anchoring device may releasably secure the valve module in the passage. A method of constructing a riser system may include the steps of installing the valve module in the passage, and installing at least one annular seal module in the passage. The annular seal module may prevent fluid flow through an annular space between the riser string and a tubular string positioned in the passage. Drilling methods may include injecting relatively low density fluid compositions into the annular space, and selectively varying a restriction to flow through a subsea choke in a drilling fluid return line. The riser string, including housings for the various modules and external control systems, may be dimensioned for installation through a rotary table.
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Citations
17 Claims
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1. A drilling method comprising the steps of:
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connecting an injection conduit externally to a riser string, so that the injection conduit is communicable with an internal flow passage extending longitudinally through the riser string; installing an annular seal module in the flow passage, the annular seal module being positioned in the flow passage between opposite end connections of the riser string; conveying a tubular string into the flow passage; sealing an annular space between the tubular string and the riser string utilizing the annular seal module; rotating a drill bit at a distal end of the tubular string, the annular seal module sealing the annular space during the rotating step; flowing drilling fluid from the annular space to a surface location; and injecting a fluid composition having a density less than that of the drilling fluid into the annular space via the injection conduit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A drilling method comprising the steps of:
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connecting a drilling fluid return line externally to a riser string, so that the drilling fluid return line is communicable with an internal flow passage extending longitudinally through the riser string; installing an annular seal module in the flow passage, the annular seal module being positioned in the flow passage between opposite end connections of the riser string; conveying a tubular string into the flow passage; sealing an annular space between the tubular string and the riser string utilizing the annular seal module; rotating a drill bit at a distal end of the tubular string, the annular seal module sealing the annular space during the rotating step; and flowing drilling fluid from the annular space to a surface location via the drilling fluid return line, the flowing step including varying a flow restriction through a subsea choke externally connected to the riser string to thereby maintain a desired downhole pressure. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification