The bits in the underground work after a certain time, drag bit blade diameter became small, short, blunt, the rock breaking ability becomes weak, slow progress; roller bit tooth wear due to erosion, bearing damage, will cause the cone roller rotation is not flexible or stuck, so that the torque increased, if not timely play that will happen cone off accident; diamond bit due to formation heterogeneity caused by PDC bit on the occurrence of crack, break, drop, also make slow drilling footage. In order to speed up the drilling speed of the whole well, it is necessary to replace the old bit in time, while the drill bit is hundreds of meters to thousands of meters. How do the drilling workers change the drill bit?

        If the cone bit has been worn, it is necessary to stop drilling immediately and replace the drill bit. After drilling, the drilling fluid circulation should be maintained for a period of time, and routine inspection of drilling equipment should be carried out. Drilling workers use the crane, moving block and hook on the derrick, and drill out all the drilling tools from the well according to the height of the derrick. After pulling out the pipe column sequentially discharged inside the derrick, the downhole drilling string at the same time, to use the drilling pump continuously to the annular space of drilling fluid, is maintained within the wellbore liquid height decreased, the wellbore pressure to balance formation pressure, to prevent fluid borehole collapse or underground strata enter the wellbore. At the same time, the operator should strictly control the speed of ascension. When all the drill pipe and drill collar in the shaft are lifted out, the drill bits need to be replaced simultaneously. The workers will unload the old bit and install a new cone bit, and then drill into the well according to the original column and then resume drilling