Passing ability of medium/short-radius whipstocking screw drill tools inside casing

Because build angle rates of sidetracked medium-short radius horizontal wells are higher than conventional horizontal wells with medium-long radius,their structural bent angles are very high.This paper analyses how the whipstocking screw drill tools easily trip in casing.On the basis of minimum deformation principle,deformation of the drill tools in casing is analysed,undetermined boundary problem during deformation is solved.Meanwhile,running of 120 and 95 double tilted screw drill tools in 178 casing are verified.The result shows 120 double tilted screw drill tools must be changed to 95 drill tools in order to easily pass through 178 casing.Feasibility and effectiveness of energy analysis method are also verified.