Top drive well drilling apparatus

Claim 1

Well drilling apparatus comprising: a drilling unit including an element adapted to be connected to the upper end of a drill string for rotation therewith about the axis of the string, and a motor operable to drive said element and the connected string rotatively about said axis; an elongated guide structure which extends generally vertically parallel to said axis and which guides the drilling unit, in a predetemined active position thereof in which the unit is aligned with said axis, for movement upwardly and downwardly relative to and along said guide structure and along said axis to drill a well; a traveling block which is suspended above the drilling unit and is power actuable upwardly and downwardly along said axis; a connector carried by said traveling block and detachably connectable to said drilling unit in a relation suspending the drilling unit from the traveling block in said active position of the drilling unit for movement upwardly and downwardly with the traveling block along said axis to drill a well; an upper first carriage engaging said guide structure and guided thereby for movement relative to the guide structure parallel to said axis and which is connected to said traveling block to locate it in alignment with said axis as the traveling block moves upwardly and downwardly; a lower second carriage engaging said guide structure at a location beneath said upper carriage and guided by said guide structure for movement relative thereto along said axis and connected to said drilling unit to locate it in alignment with said axis and said traveling block as the two carriages and said traveling block and said drilling unit all move upwardly and downwardly together to drill a well; and means mounting said drilling unit including said element and said motor thereof for movement laterally relative to said upper carriage and said traveling block between said active position in which the drilling unit is aligned with said axis and suspended from the traveling block for vertical movement therewith and an inactive position in which the drilling unit is detached from said connector and traveling block and is offset to a side of the axis, while the traveling block is retained by said upper carriage and guide structure in alignment with said axis to suspend a drill string independently of the drilling unit for movement upwardly and downwardly with the traveling block along said guide structure and relative to the laterally offset drilling unit.