Thanks for replying dcasto. In this situation pressure and volume will be fluctuating, so I don't believe Bernoulli's applies. I should have mentioned in my original post that this is for the purpose of rock formation fracturing, so not a simple case of just a gas flowing through a tube.
I'm trying to determine pipe friction pressure resulting from pumping N2 at 100 Mscfm through 4.5"(OD)/4.0" (ID), 11.6lb casing. Does anyone happen to know the governing equations?