Definition(s)
Bottom-Hole Assembly
That part of the drill string located directly above the drill bit. The components primarily include drill collars and other specialty tools such as stabilizers, reamers, drilling jars, bumper subs, heavy weight drill pipe, etc.
Source: API RP 64, Recommended Practice for Diverter Systems Equipment and Operations, Second Edition, November 2001 (March 1, 2007). Global Standards