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25. om Gud ln sfo s c c
25.1 Required Data
Experience has shown that the most common cause of an unexpected collision is lack of awareness of the very existence of the hazard well! It is essential that the following questions are asked before well planning commences;
1. What are the sources of the client survey data? 2. How can we be sure that the data set is complete? 3. How does the database compare with the data held by the geoscientists, in-house surveyors and the regulatory authorities? 4. Are we sure that all surveys are complete to TD? 5. Are all possible offset wells within reach of the current well included? (Be sure to include wells from other sites if necessary and exploration wells). 6. Does the reference data agree with those held in other in-house databases and is it what the site surveyors used when establishing site coordinates and directions?
The following information should be gathered and considered in detail prior to beginning the actual well planning design process.
25.2 Position and Referencing Data
Clearly it is essential that all data required to fully define the location of a well and its adjacent hazard wells must be available to the well planner. These must include;
Required Data:
Example:
The field or project name The name of the well site
Orkney West Alpha Platform
The units of measure used at this site Ft The geographic location of the Site Centre in Latitude and Longitude
56 o 26’ 18.32” 11 o 32’ 56.78” W
The Geographic Datum on which Latitude and Longitude are defined
WGS 84
The map coordinates of the Site Centre
6257790.50 North 342842.46 East
The map units used
m
The coordinate system in which the Map Coordinates are defined
UTM Zone 29 North
The accuracy of this point (surface uncertainty) The clients preferred North Reference True or Grid
+/- 5 m
Grid
The Grid Convergence
-2.12o 120 ft
The height of the drill floor above Field Datum
The Definition of Field Datum
Mean Sea Level
The Depth BDF to the Ref Point from which uncertainty accumulates
270ft
The Definition of the Reference Point
Mud Line
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