1. Index Line – the only accurate measuring technique
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2. Fixed distance from top of outer slip joint to Datum – top of 18 ¾” HPWH Datum – top of 18 ¾” HPWH Riser BOP Sea bed The index line is a very accurate measuring system which is independent of heave, tide and rig draft. It should be used for all wellhead operations and landing casing. It is also very important to use the index line when coring or milling or any other operation where accuracy is important or when progress is less than tide changes.
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3. The distance from the top of outer slip joint to the Datum – top of 18 ¾” HPWH is fixed. This does not change regardless of tide and rig draught.
Land wear bushing (or other tool in wellhead) and put down 10k lbs.
With pipe in the wellhead pull the index line taut to a set point (loop) and make a mark on the pipe (the most accurate method is to pull the line taut through the handle on the master bushing pin and make the mark when the rig moves up and you feel the line being pulled down).
The index line distance = distance from the datum to the mark on the pipe
The index line distance stays the same for the rest of the well
If a different tool is run to the wellhead or a different running string is used you work in reverse by taking the index line depth and subtracting the new usable tool length (from wellhead serviceman) to give a new drill pipe length to use. Make a mark at this measurement on the running string.
When using the index line ignore tide and heave as they do not play any part in this very accurate technique for measuring depth
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4. A. Urdevics 091225 HIGH TIDE LOW TIDE
Fixed distance from index line loop to Datum – top of 18 ¾” HPWH
Riser
Fixed distance from top of outer slip joint to Datum – top of 18 ¾” HPWH
BOP
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Datum – top of 18 ¾” HPWH
Sea bed

5. 1. Align the rotary bushing master pin to the rat hole
Index line next
to drill pipe
Master
bushing
pin
Riser
1. Align the rotary bushing master pin to the rat hole
2. Pull the index line through the rat hole and pull through the master bushing pin handle and then pull the loop taut in the line to a convenient height.
3. Make the mark when the rig moves up and the line feels like it is being pulled down
4. This technique can be done by a single person because the line is next to the drill pipe and therefore a long triangle is not needed
BOP
Datum – top of 18 ¾” HPWH
Sea bed
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