The drill string transmits mechanical and hydraulic power from drilling rig at surface to the bit at bottom of hole
the drilling string is rotated and slowly lower as the bit penetrates formation, so the proper amount of weight mainting on the bit
Drilling mud is pumped down inside of the drill string and output nozzles in the bit.
The bit drilling action creats one fragments called cuttings which are washed away from bits face by the jetting mud
the mud then transports the cuttings of annular space on the outside of drill string to the surface where they are removed by solid control equipment
the following sections will describe each of commonly use componets of the drill string.
