Study on mechanical properties of high-strength casing milling and mechanisms of high-efficiency windowing drill bit

Abstract

During breaking window in deep and ultra-deep wells, the cutting teeth of the drill bit are prone to be blunted due to the thickness and high strength of the casing wall and the poor drillability of the rock. A new milling cone bit is innovatively designed. The bit has 9 cutter wings, and double rows of cutting teeth are staggered on each cutter wings to enhance the ability and stability of window breaking. The dynamics simulation model of sidetracking window was established to explore the law of window formation and verify the feasibility of the design of the drill bit and its whipstock. Drill bits and supporting tool structures are optimized with the aid of simulation. The prototypes of drill bit and whipstock were developed to carry out the windowing test of TP155V steel casing (yield strength up to 1068 MPa). It was revealed that the success rate of windowing is 100%. The similarity between the window shape obtained by the experiment and the window shape obtained by simulation is nearly 100%. The bit and its tools provide a new method of casing windowing in deep and ultra-deep wells. Its lays the foundation for further research on the sidetracking process.