According to the principles of rock destruction, mechanical drilling of wells can be carried out in several ways, differing in their physical nature. For medium- and high-strength rock, roller cone bits with milled cutting structure or reinforced with high-strength tungsten carbide pins are used. The roller cone method of drilling implements the principle of bottom-hole destruction due to static impingement of the cutting structure, the rock is destroyed mainly by a piercing, partially blocked chipping. From the energy point of view, such impact on the bottom hole is not optimal.
Fracture of rocks for industrial or other needs (hammering, drilling, extraction of piece rock, processing, etc.) regardless of the method and technology of loading is a local short-term intensive impact, proceeding according to the scheme: load application - deformation - growth of micro- and then macro-damages - growth of cracks - fracture. In this regard, the applied theory of rock failure should not take into account rheology and relaxation, i.e., the model of such failure does not take into account the evolution of micro- and macro-damages in the rock. These phenomena can be accounted for by the ultimate stress or strain in the current state of the fractured rock volume.
