Window-opening taper mill is a new type of window-opening tool in the casing, which can complete window-opening and window repairing operations only once in the well. It has high efficiency, flat windows, smooth, easy to pass through the drill string, it is an ideal side drilling tool. For on-site operations, first lower the tool to the top of the deflector to check whether the depth is accurate. After calibrating the depth, slowly rotate, the initial weight on bit control is zero, slow idle is beneficial for future drilling. The speed should be controlled at 20-30.5 r / min, and the drilling weight 15-30KN. After the window is opened, continue drilling to a certain depth to start drilling.