Survey Calculations

The results of a directional survey are given in terms of azimuth and inclination of a borehole at a certain depth. In this chapter it will be assumed that all the necessary corrections (magnetic declination, gyro drift) have been applied to the survey results. This information must then be analysed to calculate the actual position of the wellbore at that survey station relative to the surface location. In order to do this the incremental distances ΔV, ΔE, ΔN between the successive survey stations must be calculated. With the coordinates of the upper station known, the coordinates of the lower station can be found by addition. The horizontal coordinates of a point are referred to as the “Northing” (or latitude) and the “Easting” (or departure).