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How a wellbore is drilled from surface to reservoir — the rotary rig, the drill string, bits, drilling mud, and how modern wells turn horizontal through the pay zone.
Drilling is the process of boring a wellbore from the surface down to a hydrocarbon reservoir that may sit two miles or more underground. Virtually all modern wells use rotary drilling: a bit on the end of a rotating drill string grinds through rock while drilling fluid (mud) is pumped down to clean the hole, cool the bit, and control pressure.
This guide breaks down every part of the operation — the rig and its components, the drill string and bit types, drilling fluids, well control, and the directional and horizontal techniques that made the shale revolution possible.
Land, jackup, semi-submersible, drillship and more.
Read →The rotary drilling process, step by step.
Read →Steering the bit through the reservoir.
Read →Drill pipe, collars, BHA and stabilizers.
Read →Roller cone vs PDC bits and how they cut.
Read →What mud does and the main systems.
Read →Kicks, blowouts and the role of the BOP.
Read →How drilling at sea differs from land.
Read →
Built by the team behind OpsFlo — field service & billing software for oilfield service companies. Capture tickets at the wellsite and bill in days, not weeks.
Mud weight creates hydrostatic pressure that balances the formation's pore pressure. Too light risks a kick or blowout; too heavy can fracture the rock and cause lost circulation. Engineers keep mud weight inside this 'mud weight window.'
Both rotate the drill string. A rotary table on the rig floor turns a kelly to spin the string from below, while a top drive is a motor suspended in the derrick that rotates the string from above — giving better control and faster connections.
Onshore wells commonly reach 5,000–15,000 ft true vertical depth, with horizontal laterals adding several thousand more feet of measured depth. The deepest wells exceed 30,000 ft.