Techniques of long milling operation on large sized casing at BZ13-1-XX Well
BZ131-XX Well is an abandoned well in Bozhong 13-1 Oilfield.To tap into its remaining reservoir,a milling operation of 222 m is conducted on its 339.7 mm casing to drill the well into a new one by sidetracking.This paper analyzes the reasons for shallow sidetracking selection at the XX Well.Based on the experiences of XX Well milling operations,the paper summarizes the operation specialty of milling tools,operating points,milling technology,and challenges in the milling process.It is indicated in the paper that,for shallow milling casing,the equipment failure rate can be reduced if the drilling tool is equipped with a bidirectional shock absorber.After milling to the design depth,a bit of the same size as the sidetracked wellbore should be used for drifting before subsequent cement plug sidetracking operation.Soil slurry with high viscosity and high gel strength should be used for plugging.The displacement rate should be as high as possible to achieve effective iron filing carrying.In every 3 m of milling,the drilling string should be moved twice up and down at a high displacement rate in large amplitude to prevent drill pipe sticking caused by severe cutting accumulation.
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