Offshore drilling is only typically carried out in order to extract a substance which lies in plant formations.
In industry, virtually all drilling is done by automated machines, and the bits are often automatically replaced by the equipment as they wear, as even solid carbide bits do not last long in constant use
 Primarily in onshore oil and gas fields once a well has been drilled, the drilling rig will be moved off of the well and a service rig (a smaller rig) that is purpose-built for completions will be moved on to the well to get the well on line

