Rotary Drilling Fluids - An Overview
Most large holes in large quarries, open pit mines, petroleum extraction, and other industries are drilled using rotary drilling. Rotary cutting can also be used in soft rocks to drill small boreholes. For instance, small holes of 25 millimeters in coal mines are frequently drilled using rotary drilling. In soft rocks, rotary cutting is used, while rotary crushing is used in medium to hard rocks. Three-cone drill bits with numerous teeth or buttons that freely rotate like planetary gear and crush the rock as the drill bit rotates are the most common bits used in rotary crushing. The weight of the drill rig provides the downward thrust, and the drill pipe's end causes the rotation. A hydraulic or electric motor drives the rotation, typically at speeds ranging from 50 to 120 revolutions per minute. Cuttings are frequently discharged from the bottom of the hole using compressed air. The flushing of drill cuttings is correlated with the size of the gap that exists between the drill pip