Combined casing head

The utility model discloses a combined type casing head which is especially suitable for drilling a well and extracting oil. A main body of the casing head of the utility model is a combined type structure, the upper part of the main body is provided with flanges, and the lower part of the main body is provided a shell, wherein the flanges are sheathed on the shell, the flanges are locked by a locking block and is sealed by a sealing ring. A plurality of keys are arranged on the matching surface of the flanges and the shell in order to prevent the corresponding rotation of the flanges and the shell, and the flanges are designed to two kinds specifications which are respectively a well drilling flange and an oil extraction flange. When a well is drilled, the well drilling flange is sheathed on the shell of the casing head; after the well is drilled, the utility model can be changed into an oil extraction wellhead by operation, the well drilling flange is disassembled, and the oil extraction flange is assembled, and the oil extraction flange is directly connected with the oil extraction wellhead in order to offer convenience for assembling an oil extraction unit.