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Points to Ponder
The most important lesson from this section is that North must be defined. Whether True, Grid, Magnetic, or Local, it must be referenced in some way to True North. If these numbers are not correct, the well will be drilled in the wrong direction, which may not be detectable on site.
Do not rely on anything other than documented evidence and, if still uncertain, a survey company must be brought in to establish the North Reference relationships.
Because they sometimes do not demand that the reference be included, it is important to be thorough when submitting data to regulators because it can otherwise be impossible to establish, after the event, which North was used.
4 h E h’sM gn cF ld
4.1 Basic Outline
A h h ofh pln s n nomousmgn cco h g sh E h’sn g os usful f nc. h lns of magnetic force run from south to north and these provide a reference for our compasses.
Figure 25: Basic Earth internal layers.
ofullyd fn h E h’sM gn cF ld ng h, usually measured in nano Teslas or micro Teslas, the Declination Angle defined as the True Direction of Magnetic North and the Dip Angle defined as the vertical dip of the Earth vector below horizontal. For computing reasons, this vector is often defined as three orthogonal magnetic field components pointing towards True North, East, and vertical referred to as Bn, Be and Bv. A fundamental law of physics relating magnetic field strength to electric current is known as the Biot-Savart Law and this is our best explanation for why B is used to denote magnetic field strength. If you know better, please contact the author - details at the front of this publication. ny loc on, w n d h compon n s of co. h F ld
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