Deviation:

The amount of deviation is a function of the drift angle and hole depth.

The term is sometimes used to indicate the angle from which a bit has deviated from the vertical during drilling.

See drift angle.

Terms Related to Deviation

• Deviation survey

  An operation made to determine the angle from which a bit has deviated from the vertical during drilling. There are two basic deviation-survey, or drift-survey, ...

• Drift angle

  The angle at which a wellbore deviates from the vertical, expressed in degrees, as revealed by a directional survey. Also called angle of deviation, angle ...

• Directional drilling

  1. Intentional deviation of a wellbore from the vertical. Although wellbores are normally drilled vertically, it is sometimes necessary or advantageous to drill at an ...

• Directional survey

  A logging method that records rift angle, or deflection from the vertical, and direction of the drift. A single-shot directional-survey instrument makes a single photograph ...

• Deflection

  A change in the angle of a wellbore. In directional drilling, it is measured in degrees from the vertical

• Packed-hole assembly

  A bottomhole assembly consisting of stabilizers and large-diameter drill collars arranged in a particular configuration to maintain drift angle and direction of a hole.

• Inclination (wellbore)

  The measurement of a wells deviation from vertical. When used with fluids, a positive number indicates upflow and a negative number may represent downflow.