Flotation collar is used for completion operation in extended reach well.It seals the light weight liquid and gas in casings by the sealing device to reduce the casing string weight in drilling fluid,so that the friction between casings and well wall can be reduced effectively, so  it  solves  the  difficult  problems when running  in  casing  in  completion  operation  of extended reach well.It has simple structure,utility,reduce friction and make the casing run into place smoothly,it can be widely used in completion operation of extended reach well.