Drillability of a rock - the ability of a rock to resist the penetration of a drilling tool into it, or the rate of formation of a hole (well) in the rock under the action of forces arising from drilling . Drillability of the rock is characterized by the drilling speed (mm / min), less commonly, the drilling time of 1 m hole (min / m).
At present, a large number of classifications of rocks by drillability are known (Soyuzvzryvprom industry scale, Uniform drillability scale, scale of the USSR Ministry of Geology, Glavzolot scale, etc.) All of them are related to each other and with rock strength factors on the prof. M. M. Protodyakonova approximate correlation relationships.