Direct-mud rotary drilling Mud pump is pumping drilling fluid with closed cycle. Rock particles under drilling bit are being set in a special sludge pit (sump) where rock parts stay at the bottom and the fluid free of heavy particles is sucked in by mud pump again. Drilling fluid is put to drilling bit under pressure. Drilling process is effected by washout during rotation produce. Drilling fluid is put to drilling bit through drilling rods. Rotation is effected by rotor (drilling gearbox) This method is used to drill wells 50m to 12000m deep.