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Offshore drilling method

  • US 9,157,285 B2
  • Filed: 07/06/2012
  • Issued: 10/13/2015
  • Est. Priority Date: 11/07/2006
  • Status: Active Grant
First Claim
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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.

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