For paper calculations:
(Pipe OD)^2 / 1029.4 = Displacement/Ft * Depth = Total pipe displacement
(Hole Dia)^2 /1029.4 = Capacity/Ft * Depth = Total Hole capacity
Hole Cap - Pipe Disp = Annular Volume / Pump output = Bottoms UP
After you do this for a while, you'll memorize capacities and displacements per foot when using different sizes, and it will be a lot faster. You can layer this as many times as necessary for BHA, cased sections, etc. to improve accuracy. I know the programs are a lot easier, but everyone should be able to do it by hand...it can save your ass.
If anybody notices a mistake, let me know. Been a long time since I actually wrote it out....
Your right, everyone should know how to do this. I was never very good at math. Can you give us an "easier" calculation example? For me it just about has to be spelled out.
Welcome to the Forum, Troy.
[(outer pipe diamer x outer pipe diamer) / 1029.4] x Depth = Barrels to subtract
[(Bit Diameter x Bit Diameter)/ 1029.4] x Depth = Open Hole Volume in Barrels
the 1029.4 is the conversion factor if you are using inches and you want barrels.
(Open Hole volume - Barrels to subtract)= Annular Volume
Annular Volume (bbl) / Pump Output (bbl/stroke) = stroke to B/U
you do a similar dimensional analysis for the Pipe ID if you want surface to bit, or surface to surface. You have to do it for different sections of the drill string if you have more than one size pipe, or if you have a lot of heavy weight pipe on the BHA. You also have to do the annular volume of the inside of the casing as seperate section from the annular volume of the open hole. You calculate the annular volume's for each of the sections that need to be considered, add them up to get a total annular voulme before you can do the final calculation for B/U. Or, if you are in a huury and ou don't trust the pump efficiency or think there's so much wash out, you do a quick and dirty estimate of the annular volume and the pump output and BS it until you can get a good connection gas or a carbde drop.
But at some point durring your shift you really should know your theoretical lag. The comparison between your theoretical lag and your actual lag are pretty important if you are paying attention to the hole. It could get you run off the location if you can't do this.
I usually use a spreadsheet because I can never remember te constant and because I can play with the pump output to see if I suspect the rig pump is the bad lag culprit. Sometimes you can get bad pipe figures, or a pipe could be washed out, or a number of other things could be going on.
You ave to also be able to trust your stroke counters.. another unnpleasant topic..
man, I'm kinda glad I laid off.