Drilling-free sizing collar and process

The invention belongs to a well cementation underground tool, in particular to a drilling-free sizing collar and a process. The drilling-free sizing collar comprises an outer sleeve, a gravity plug seat, an upper joint, a lower slide sleeve, a closing sleeve and a rubber plug sleeve. The invention has the technical scheme that the process comprises the following steps: carrying out the primary cement filling operation according to the well cementation procedure; putting a gravity plug after the primary well cementation pressure building is completed so that the gravity plug seat and the lowerslide sleeve can synchronously go down; opening a circulation hole for establishing secondary circulation; then, implementing the secondary cement filing operation; completing the pressure building when a secondary rubber plug moves to the rubber plug sleeve of the sizing collar after the secondary cement filling operation is completed; pressurizing the well for shearing off the closing sleeve and a second nail pin group; pushing the closing sleeve and the rubber plug sleeve to synchronously move down; closing the circulation hole; then, continuously carrying out pressurization; controlling the pressure variation so that the gravity plug seat, the gravity plug, the rubber plug sleeve and the secondary rubber plug are connected into a whole body to be sunk into the well bottom; and completing the secondary cement filling operation. The invention provides the drilling-free sizing collar and the process with the advantages of low cost, good manufacturability and short time.