Sealing nipple for floating lower casing

The invention belongs to the technical field of petroleum drilling, and discloses a sealing short section for floating casing running, which comprises a short section cylinder and a sealing assembly, the two ends of the short section cylinder are respectively connected with a first casing and a second casing, and the inner wall of the short section cylinder is provided with a bulge. The sealing assembly is arranged in the short section cylinder and comprises a soluble plug, one end of the soluble plug abuts against the protrusion, and the soluble plug divides an inner cavity of the short section cylinder into two independent cavities. The first sleeve is located on the side, away from the protrusion, of the soluble plug, the first sleeve is filled with dissolving liquid, and the dissolving liquid can dissolve the soluble plug within set time. During casing running, dissolving liquid and drilling fluid are poured into the first casing, the second casing is filled with air, the second casing is firstly put into