METHOD OF DRILLING WITH A STRING SEALED IN A RISER AND INJECTING FLUID INTO A RETURN LINE

摘要

A drilling method comprising the steps of: sealing an annular space between a tubular string and a riser string; flowing drilling fluid from the annular space to a surface location via a drilling fluid return line; and injecting a fluid composition having a density less than that of the drilling fluid into the drilling fluid return line via an injection conduit.