This example that I got from my junior member is very simple but it helps you a lot to understand about how to determine pressure loss during normal circulation.
Information given is listed below;
Circulate at 3 bottom up through open end tubing (Down tubing and up annulus) with 12.7 ppg mud.
Pump pressure = 1000 psi
Annulus friction loss = 50 psi
Inside tubing friction loss = 925 psi
Surface line friction loss = 25 psi
Calculate the pressure in the well at 10,000’ (tubing tail).
What would ECD at 10,000’ TVD be?
The concept of calculation that you should know : total pressure at bottom = pumping pressure + hydrostatic pressure – pressure loss in the opposite way of fluid flowing.
If I reference to the drill string site, I will get the equation like this.
Pressure at bottom hole= Hydrostatic Pressure at bottom hole + Pressure from pump- Pressure Loss in surface line – Pressure loss in tubing
Pressure in the well at 10,000’ = 0.052×12.7×10000 + 1000 – 25 – 925 = 6654 psi
If I reference to the annulus site, I will get the equation like this.
Pressure at bottom hole= Hydrostatic Pressure at bottom hole +Annular pressure loss
Note: Hydrostatic pressure and annular pressure loss force downward.
Pressure in the well at 10,000’ = 0.052×12.7×10000+ 50 = 6654 psi
Note: It doesn’t matter which site of u-tube you refer to the bottom hole pressure is still the same.
ECD (Equivalent Circulating Density) is calculated by this following equation:
ECD = Current mud weight in PPG + (annular pressure loss /(0.052xTVD))
ECD = 12.7 + (50/(0.052 x 10000))
ECD = 12.8 ppg