The Problem
Since there isn't a single reference or measurement system for calculating the depth in sub-surface environments, two engineers talking about a single drilling might give different answers when asked to give a measurement of depth.
The two main depth references used in the "downhole" (i.e. sub-surface) environment are Driller's Depths and Logger's Depths (also called Wireline Logger's Depths). These measurement systems are recorded quite differently and generally Logger's Depths are considered the more accurate of the two:
- Driller's Depth measurement is tied to drilling operations and other closely associated activities such as logging while drilling (LWD), measurement while drilling (MWD) and coring.
- Driller's Depth is always recorded, and it constitutes the primary depth system, unless it is later superseded by a more accurate measurement such as the depth from an open- or cased-hole wireline log.
- Driller's Depth should always have 1) a unit of measurement e.g. meter or feet, 2) a datum reference e.g. rig floor.
Read more about this topic: Driller's Depth
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