RE:A question to the wsie: Am I right in my understanding that I was a Drilling Eng 25 years ago so things may have changed, but in general:
1) Faster drilling does not impact amount of fluid.
2) Longer wells does increase amount of fluid.
3) Invert fluids are generally rented and renturened and rejuvinated for next customer, vs non-invert muds which are dumped after each well.
4) Deeper wells mean bigger holes in vertical section require more mud.
5) More over-pressured reservoirs mean more weighting up, means more barite used and consumed.
6) Faster wells mean harder on equipment, ie directional drilling motors take huge beating.
Hope helps.