Depth Referencing

This article describes the various depth references used for drilling onshore and offshore wells: Reference Datum, Chart Datum (CD), Mean Sea Level (MSL), High Tide (HT), Low Tide (LT), Water Level (WL), Lowest Astronomical Tide (LAT), Depth Subsea (SS)

Reference Datum

For operations involving a rig, either onshore or offshore, all depths (either along hole or true vertical) are referred to the drill floor of the rig which initially drilled the well (original drill floor).