Underwater well drilling method

Claim 1

IN A METHOD OF DRILLING AN UNDERWATER WELL FROM A VESSEL AT THE SURFACE OF A BODY OF WATER, THE OPERATION OF RUNNING A CASING STRING DOWN INTO AXIAL REGISTER WITH THE WELL ALREADY CONTAINING A DRILL STRING MOVABLY POSITIONED THEREIN, SAID OPERATION COMPRISING THE STEPS OF: FORMING HOLE IN THE GROUND BENEATH SAID BODY OF WATER WITH A DRILL STRING AND LEAVING SAID DRILL STRING IN SAID HOLE; RAISING THE DRILL STRING PARTIALLY OUT OF THE WELL SO THAT ITS UPPER END IS ABOVE WATER IN THE VICINITY OF THE VESSEL AND ITS LOWER END IS OFF THE BOTTOM OF THE WELL A DISTANCE AT LEAST GREATER THAN THE DEPTH OF WATER UNDER VESSEL; HANGING THE UPPER END OF SAID DRILL STRING AT THE VESSEL FROM THE INTERIOR OF A CASING STRING SUPPORTED AT THE VESSEL SO THAT THE PIPE STRING IS ADAPTED TO BE MOVED UPWARDLY WITHIN SAID CASING STRING; LOWERING THE COMBINED CASING STRING AND DRILL STRING HANGING THEREFROM INTO THE WELL UNTIL AT LEAST THE LOWER END OF THE CASING STRING HAS ENTERED THE TOP OF THE WELL, GUIDING AND LOWERING A RETRIEVING TOOL FROM THE VESSEL DOWN THROUGH THE CASTING STRING; ENGAGING THE UPPER END OF SAID DRILL STRING WITH SAID RETRIEVING TOOL; AND PULLING THE RETRIEVING TOOL AND DRILL STRING UP THROUGH SAID CASING STRING TO THE VESSEL.