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Lag Calculations.
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Post: #1
Toungue  Lag Calculations.

This is a formula for calculating lag or comparing your own numbers....Big Grin

.zip File  lag (Size: 28.22 KB / Downloads: 200)

What does not kill us, makes us stronger.....

12-17-2006 11:26 PM
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Darryl Maddox
Junior Rockhound

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Post: #2
RE: Lag Calculations.

First of all, thanks for putting this up. I am sure it is used by many.

Nlow to the reason I am replying -
Why so many decimals in the results boxes?

Generally one doesn't have more significant digits in an answer than in the least precisely known input variable. You listed bit size as 8.75 so that is 3 significant digits and that limits all answers involving this variable to 3 significant digits.

I know the 8.75 is the exact (to any disired number of sig digits) equivalent of the 8 3/4 stated on the bit but to use that argument to justify even a 4th significant digit is to argue that the bit is in gauge +/- 0.0005 inch and is that really reasonable for a bit that has drilled a few thousand feet?

Also I noticed you had slippage at 0.95 - a guesstimate? is it really good to +/- 0.005? If it isn't then it becomes even less precise than the 2 digits you gave it.

Looks like these answers should be rounded back to about 2 or 3 digits (at most) meaning most will have either one or no decimals.

I don't think anyone else in the oil field worries about such things but it is just one of my picky points.

I had a geologist tell me after spending 2 hours correlating logs and calculating something or other that the core point was going to be 5222.5 feet. I choked back the laughter because I had been told he was a very good geologist and I wanted to work with him again. And he did it!! He called TD at 5222.5 on the Pason, tripped out, put on core barrel and got within a foot on either end of the section he wanted. The nearest well was over a mile away. Now that is luck, not accuracy. And I saw a geophysicst predict a formation top within 2 feet at more than 6000 feet. More luck than justifiable accuracy.
But decimals seem to make us feel better about things so I am used to seeing them - justified or not.


02-15-2013 08:10 PM
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