The invention relates to a method for replacing a producing well shaft casing
pipe. The method sequentially includes the steps of firstly, using a packer to block the inner cavity of a residual casingpipe; secondly, using a hydraulic inner cutter to
cut off the abraded casing
pipe on the upper portion of the residual casing
pipe; thirdly, pulling out the
cut casing pipe; fourthly, mounting a casing pipe mill shoe at the bottom of a drilling tool to mill a fish top outer chamfer at the fish top of the residual casing pipe; fifthly, mounting a float collar and a new casing pipe at the upper endof a cementing tool; sixthly, lowering the drilling tool to allow the fish top to smoothly enter an externally-inserted guide shoe, continuously lowering the drilling tool to allow the fish top to reach a lengthening cylinder, and starting a pump to circulate
workover fluid; seventhly, injecting
cement slurry after the circulation is normal to allow the
cement slurry to enter the annulus throughcement injection holes; eighthly, putting in a rubber plug, and pushing the rubber plug to the top of the float collar to achieve setting; ninthly, lowering the drilling tool again until the fish topouter chamfer and a
butt joint connector inner chamber are connected in an embedded manner, and pressing down 500kN to achieve casing pipe
butt joint and sealing. The method is simple, practicable, convenient to operate, low in production cost and downhole risks, simple in
butt joint and setting operation and high in sealing reliability.