Apparatus for drilling with a gaseous drilling fluid

Claim 1

APPARATUS FOR INJECTING FLUID INTO THE LOWER PORTION OF A BOREHOLE IN THE EARTH COMPRISING: A TUBULAR DRILL STRING SECTION; A FLUID EXPANSIBLE ANNULAR PACKER AFFIXED TO THE OUTER SURFACE OF SAID DRILL STRING SECTION, CONSTRUCTED AND ARRANGED SO THAT FLUID PRESSURE EXERTED ON THE INNER SURFACE THEREOF WILL EXPAND THE PACKER TO THE WALLS OF THE BOREHOLE; FIRST AND SECOND FLUID PASSAGEWAYS IN SAID DRILL STRING SECTION CONNECTED IN PARALLEL BETWEEN THE BORE OF SAID DRILL STRING SECTION AND THE EXTERIOR OF SAID DRILL STRING SECTION UNDER THE PACKER; A THIRD FLUID PASSAGEWAY IN THE DRILL STRING SECTION BETWEEN THE BORE AND THE EXTERIOR OF THE DRILL STRING SECTION OPENING TO THE EXTERIOR OF THE DRILL STRING SECTION BENEATH THE LEVEL OF SAID PACKER; FIRST VALVE MEANS POSITIONED IN SAID FIRST PASSAGEWAY AND HAVING A PORTION THEREOF EXPOSED TO BOREHOLE PRESSURE AROUND SAID DRILL STRING SECTION IN THE VICINITY OF THE PACKER, CONSTRUCTED AND ARRANGED TO CLOSE SAID FIRST PASSAGEWAY UNTIL PRESSURE IN SAID DRILL STRING SECTION BORE IS GREATER BY A FIRST PREDETERMINED DIFFERENTIAL PRESSURE THAN THE BOREHOLE PRESSURE ABOVE SAID PACKER; SECOND VALVE MEANS CONNECTED TO SAID FIRST VALVE MEANS AND ACTUATED BY SAID FIRST VALVE MEANS, CONSTRUCTED AND ARRANGED TO CLOSE SAID THIRD FLUID PASSAGEWAY UNTIL SAID FIRST VALVE MEANS IS SUBJECTED TO PRESSURE IN SAID DRILL STRING BORE THAT IS GREATER BY A SECOND PREDETERMINED DIFFERENTIAL PRESSURE THAN THE PRESSURE IN SAID BOREHOLE ABOVE SAID PACKER;