PURPOSE: To surely close a side discharge port of a casing against a cement flow by rotating a drive tool to form a passage passing through a cement cured in a chamber of a stage collar, and abutting the tool on a sleeve to move the sleeve to the position where a secondary discharge port can be closed.

CONSTITUTION: A control sleeve drive tool 56 is lowered while turned, and cooperated with a stage collar 14 to crush and remove a solidified cement contained in a casing. When the drive tool 56 is advanced downwardly, at least one part of an annular projecting part 37a for sealing of an upper sleeve segment 29 is removed. Then, the drive tool 56 is brought into contact with the upper segment 29 of a compound sleeve, and the segment is advanced to the downwardly moved position, i.e., the intended closing position. An internal chamber of a casing, i.e., a center passage is isolated from a wellbore 10 by closing a side cement discharge port 27.