Drill bit (well)

Subsurface formations are broken apart mechanically by cutting elements of the bit by scraping, grinding or localized compressive fracturing.

The cuttings produced by the bit are most typically removed from the wellbore and continuously returned to the surface by the method of direct circulation.

Extremely hard tungsten carbide material is often applied to the surfaces of the teeth by a welding process to improve durability.

This bit employed two conical steel rolling elements with milled teeth that engaged the formation, when the device was rotated, to produce the cutting action.

Regardless of type, drill bits must satisfy two primary design goals: maximize the rate of penetration (ROP) of the formation and provide a long service life.

It might cost hundreds of thousands of dollars to mobilize the equipment and manpower resources required for drilling to the site.

The ability of a bit design to satisfy the two primary goals is constrained by a number of factors, most importantly the wellbore diameter.

Other constraints are dictated by its intended use: formation type (hardness, plasticity, abrasiveness) to be drilled, operating environment at depth (temperature, pressure, corrosiveness), the capabilities of the equipment used in the operation (rotating speed, available weight on bit, pump horsepower) and the angle of the wellbore (vertical, directional, horizontal).