The standard method involves percussion drilling in which a drill is alternatively raised and dropped in the descending borehole. It is suited to the drilling of wells in any material from soft clay to the hardest rock.
[pdf] There are two separate but closely related parts of preparing for a drilling project—planning the well and designing the well. “Planning” means to list, define, schedule, and budget for all the multitud.
[pdf] Electric generators powered by large diesel engines (the prime movers) generate electricity that move the heavy rig equipment such as the rotary table (or top drive), mud pumps and drawworks. Electric drill rigs are more expensive than mechanical rigs, but offer some nice advantages in return.
[pdf] 
