# Deep well drilling

Deep well drilling involves drilling (a well) to a desired "deep" depth of 10,000 ft or more.

## Overview

Deep well drilling is sometimes more importantly characterized by the requirement of having the drill bit finally positioned within a specified radius of its surface starting location. This sometimes requires maneuvering the direction (azimuth) of the drill bit by various techniques (kicking) so as to arrive at the desired location at both the desired depth and within a specified radius of the starting point. The angle of drilling at any arbitrary azimuth can be derived by knowing the TVD (true vertical depth) and the MD (measured depth or hypotenuse) of any given segment.

## Mathematics

This section demonstrates the formulae used to determine the current drill-bit location relative to its starting position given the azimuth, angle from vertical ("plumb angle") and either the TVD or MD of each drilling segment. If both the TVD and MD are known for any segment then the "plumb angle" for that segment is redundant. This section also provides the formula for a "straight line" solution to arrive at an arbitrary depth and radial location given its current position.

Assume:

Target is 11,560 ft down Best drilling access is 432 feet away Azimuth of 38° on the surface.

So, you should set your azimuth direction at: (38° + 180°) = 218°

Then applying the rules of trigonometry:

The angle is defined by using the arctan function to the ratio of horizontal and vertical$\arctan \frac{432}{11560}$ = 2.14°

If the drill bit doesn't get deflected then your target can be calculated by applying pythagorus' theorem$\sqrt {(11560^2+432^2)} =11568 ft.$