Bottomhole Assembly (BHA)

Definition - What does Bottomhole Assembly (BHA) mean?

Bottomhole Assembly, abbreviated as BHA, is a complex combination of several drilling tools including directional drilling assembly. It is one of the components of a drilling rig. It consists of a string below the drill pipe in a drill string. It is primary made up of drill collars, stabilizers and the bit. The Bottomhole Assembly affects the trajectory of the bit and the wellbore.

Petropedia explains Bottomhole Assembly (BHA)

The design objective of BHA for directional drilling is to provide the directional drilling tendency in-line with the planned trajectory of oil or gas well. There are various factors that determine the BHA’s directional drilling tendency. They are:

  • The force created by the bit that breaks the rock.
  • Tiltness of the bit
  • Hydraulics mechanism of BHA
  • Formation dip
  • The rock properties of the hydrocarbon formation.

The following are the functions performed by the Bottomhole Assembly:

  • It provides weight for the bit (WOB)
  • It provides the strength needed to run in compression.
  • It helps in minimizing bit stability problems from vibrations, wobbling and jumping.
  • It helps in minimizing directional control problems by providing stiffness to the BHA.
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