Tricone drill bit performance evaluation

The process of drilling can be addressed from the points of technique and technology. Technique means engineering, design and manufacture of rock-breaking drilling tools. Technology includes selection of the optimal drill tool designs in compliance with the physical and mechanical properties of rocks at the bottomhole, and in accord with the optimal modes of drilling. Roller bit drills are used in execution of 70 % of total exploration and production drilling in the world. The drill bits of this kind can actually and greatly enhance efficiency of the whole drilling process. Extremely complex kinematics of bit work in drilling, as well as high impacts applied to the bits in drilling in rocks of different hardness, viscosity, plasticity and abrasivity make the drill bit one the most complex and high-loaded mechanisms which operate under conditions of high vibrations, in a confined space and in the medium of abrasive drilling fluid. Extremely complex conditions also exist in operation of drill bits with removal of chippings and with cooling of the tool components by feeding compressed air to the bottomhole. In recent years, as the design basis is improved, and new materials and technologies appear, designers pay much attention to the design optimization and fabricability improvement of drill bits. To this effect, it is required to take into account the axial load, rotation frequency, hole diameter, rock hardness factor, as well as physical and mechanical properties of rocks a function of drilling depth. In estimation of energy inputs, it is required to validate a more effective design of a drill bit. The authors study a few operating modes of tricone drill bits, and give recommendations on their design improvement, productivity enhancement, reliability increase and life extension.