Casing pipe patching relay type cement paste replacement device

The invention provides a casing pipe patching relay type cement paste replacement device. When cement paste in an oil pipe is replaced, a rubber plug and the inner wall of the oil pipe are sealed in a matched mode, the rubber plug is pushed by pressure to move downwards, cement paste in the oil pipe and under the rubber plug is also replaced to an annular space between a patching pipe and a casing pipe, the rubber plug and a valve ball move downwards to a valve seat, a channel of the valve seat is blocked, a cutting pin is pressed and broken by push force generated by pressure, an expansion packing cup replaces a rubber plug sealing channel so that cement paste in the patching pipe and under the expansion packing cup can be replaced into the annular space between the patching pipe and the casing pipe continuously, the damaged position, corresponding to the patching pipe, of the casing pipe is blocked, and after replacement is completed, a locking device is matched with a locking connector to lock the expansion packing cup to the lower portion of the patching pipe, so that a patched oil-water well can be normally used. By means of the casing pipe patching relay type cement paste replacement device, cement paste in the oil pipe and the patching pipe can be totally replaced into the annular space between the patching pipe and the casing pipe, patching quality of the casing pipe can be improved, engineering accidents cannot occur, and remarkable economic benefits are achieved.