The Gyro Single Shot is used for orienting purposes only. While drilling, Gyro Single Shot surveys shall be taken instead of magnetic surveys or  MWD whenever magnetic interference may be present. Gyro Single Shot are also used for ‘tying-in’ MWD surveys.

Interference is likely to happen within 50 ft of steel fish or casing strings in adjacent wells and within 50 ft of the casing shoe or casing window in the same well.

Check Surveys

Magnetic check surveys should be taken to determine from which depth subsequent magnetic surveys shall be free from magnetic interference. The guideline for this determination is agreement between the grid azimuth results for the two types of surveys at two successive survey stations.

The following table shows the defined values required for agreement: