Mechanical analysis of drill bit during dual-casing sidetracking

During dual-casing sidetracking, it is found that the hardness values of productive casing, cement sheath, protective casing and rock stratum are different from each other, and the contact surfaces between the drill bit and the whipstock, productive casing, cement sheath, protective casing and rock stratum are also different. In consideration of the actual conditions of contact between the drill bit and the whipstock, productive casing, cement sheath, protective casing and rock stratum During dual-casing sidetracking, we built a mathematic model for describing the moment of dual-casing sidetracking drill bit, and then, on the basis of field engineering cases, obtained the curves by using the MATLAB software for describing the relations between the moments and horizontal moving distances of drill bit under three different working conditions. We thereupon discussed, in the view of metal cutting mechanics, the cutting force and torque of drill bit during the sidetracking, verified the strength of sidetracking drill bit, and further provided the technical suggestions for avoiding the bit jamming and breaking accidents During dual-casing sidetracking. Although the mechanics analysis model of the window drill does not fully explain the bit damage seen in the field, but the related analyses and calculations can be used as references for determining the parameters for both design and drilling of dual-casing sidetracking drill bit.