Patent ID: 9157285
Filing Date: 2015-10-13
Classification: E21B

Abstract:
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.