Wellbore Surveying
This same principle as that above is applied to wellbore surveying. In the case of wellbore surveys however the procedure must include consideration of the following:
• The process must be applied in three dimensions
• The trajectory between the survey points (the path of the wellbore) is not generally a straight line
The three dimensional aspect of the problem is not a significant issue since the same process as that outlined above can be applied to the vertical displacement as well as the horizontal displacement of the survey points (stations). The procedure is described below in section 2.7. The fact that the trajectory of the wellbore is not generally defined by a straight line is accommodated by assuming that the trajectory of the wellbore follows a simplified geometrical model. The only information that is required to determine the co-ordinates of all points in the well trajectory are therefore:
• The position of the initial, reference point (generally the Rotary Table)
• The measured depth (AHD) of the survey station
• The direction (Degrees from North) in which the wellbore is oriented at the survey station
• The inclination (Degrees from the vertical) of the wellbore at the survey station
• A mathematical model of the wellbore trajectory