Related Oil & Gas Terms

• 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, instruments: one reveals the drift angle; the other indicates both the angle and the direction of deviation....

• Deviation

  Departure of the wellbore from the vertical, measured by the horizontal distance from the rotary table to the target. 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...

• 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 of a compass reading of the draft direction and the number of degrees the hole is off vertical. a multishot survey instrument obtains numerous readings in the hole as the...

• Deflection

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

• Azimuth

  (az) the compass direction of a directional survey or of the wellbore as planned or measured by a directional survey. the azimuth is usually specified in degrees with respect to the geographic or magnetic north pole....