Method and apparatus for drilling offishore wells

Claim 1

AN OFFSHORE STRUCTURE FOR CARRYING OUT WELL OPERATIONS GENERALLY ABOVE SUBMERGED WELLHEAD MEANS, SAID STRUCTURE ADAPTED TO BE POSITIONED AT A SELECTED OFFSHORE LOCATION IN A MANNER SUFFICIENTLY STATIONARY TO CARRY OUT OPERATIONS WHEREIN PIPE MEANS PROJECTING GENERALLY UPWARDLY FROM SUBMERGED WELLHEAD MEANS MAY BE ENGAGED GENERALLY ABOVE SAID SUBMERGED WELLHEAD MEANS AT TWO VERTICALLY DISPLACED LEVELS, SAID STRUCTURE COMPRISING: AN OPERATING DECK HAVING A VERTICAL FIRST OPENING THERETHROUGH OF A SIZE SUFFICIENT TO PASS WELL TOOLS AND EQUIPMENT THERETHROUGH, AN AUXILIARY LOWER DECK POSITIONED BELOW SAID OPENING DECK, HAVING A VERTICAL SECOND OPENING THERETHROUGH OF A SIZE SUFFICIENT TO PASS WELL TOOLS AND EQUIPMENT THERETHROUGH, AND IN GENERAL VERTICAL ALIGNMENT WITH AT LEAST A PORTION OF SAID FIRST OPENING, FIRST PIPE-ENGAGING MEANS SUPPORTED BY SAID OPERATING DECK AND ARRANGED IN GENERAL ALIGNMENT WITH AT LEAST A PORTION OF SAID FIRST OPENING IN SAID OPERATING DECK, SECOND PIPE-ENGAGING MEANS, INDEPENDENT OF SUBMERGED WELLHEAD MEANS OVER WHICH SAID STRUCTURE IS ADAPTED TO BE POSITIONED, CARRIED BY SAID AUXILIARY DECK, AND ADAPTED TO BE POSITIONED IN GENERAL ALIGNMENT WITH AT LEAST A PORTION OF SAID SECOND OPENING IN SAID AUXILIARY DECK, SAID SECOND PIPE-ENGAGING MEANS BEING MOVABLY POSITIONED RELATIVE TO SAID AUXILIARY DECK FOR MOVEMENT INTO AND OUT OF GENERAL ALIGNMENT WITH AT LEAST A PORTION OF SAID SECOND OPENING IN SAID AUXILIARY DECK, AND PLATFORM MEANS, INTERPOSED BETWEEN SAID SECOND PIPEENGAGING MEANS AND SAID AUXILIARY DECK FOR SUPPORTING SAID SECOND PIPE-ENGAGING MEANS, SAID PLATFORM MEANS BEING REMOVABLE FROM PLACEMENT EXTENDING AT LEAST PARTIALLY ACROSS SAID OPENING.