Calculate Equivalent Circulation Density (ECD) with complex engineering equations

These formulas below are used for complex calculation for annular pressure loss and equivalent circulating density. I think this calculation will give you more accurate result than a simple equation. Please follow steps how to calculate annular pressure loss and ECD.

1. Determine n:
2. Determine K:
3. Determine annular velocity (v) in ft/min: v = (24.5 x Q) ÷ (Dh² – Dp²)

4. Determine critical velocity (Vc) in ft/min:

5. Pressure loss for laminar flow (Ps), psi:

6. Pressure loss for turbulent flow (Ps), psi:

7. Determine equivalent circulating density (ECD), ppg:

ECD in ppg = Ps ÷ 0.052 ÷ TVD in ft + MW in ppg

Abbreviation meaning

?300: viscometer dial reading at 300 rpm
?600: ?viscometer dial reading at 600 rpm
Q: Flow rate in gpm
Dh: Diameter of hole
Dp: Diameter of drill pipe, drill collar or BHA in ft
v: annular velocity in ft/min
L: length of drill pipe, drill collar or BHA in ft
MW: Mud Weight
PV: Plastic viscosity

Example: Equivalent circulating density (ECD) in ppg by using following data:

Mud weight = 9.5 ppg
?300? = 30
?600 = 60
Plastic viscosity = 22 cps
Circulation rate = 320 gpm
Hole diameter = 8.5 in.
Drill collar OD = 6.5 in.
Drill pipe OD = 5.0 in
Drill collar length = 650 ft
Drill pipe length = 11,500 ft
True vertical depth = 12,150 ft

1. Determine n:

2. Determine K:
3. Determine annular velocity (v) in ft/min around drill pipe: v = (24.5 x 320) ÷ (8.5² – 5² ) = 165.9 ft/min

4. Determine critical velocity (Vc) in ft/min around drill pipe:

The annular velocity around drill pipe is more than the critical velocity around drill pipe so this is turbulent flow. The equation #6 (for turbulent flow) must be applied in this case.

Pressure loss for turbulent flow (Ps), psi:

5. Determine annular velocity (v) in ft/min around drill collar: v = (24.5 x 320) ÷ (8.5² – 6.5²) = 261.3 ft/min

6. Determine critical velocity (Vc) in ft/min around drill collar:

The annular velocity around drill collar is less than the critical velocity around drill collar so this is laminar flow. The equation #5 (for laminar flow) must be applied in this case.

Pressure loss for laminar flow (Ps), psi:

Total annular pressure loss = annular pressure loss around drill pipe + annular pressure loss around drill collar

Ps=69.2+12.7 = 81.9 psi

7. Determine equivalent circulating density (ECD), ppg:

ECD in ppg = (81.9 ÷ 0.052 ÷ 12,150) + 9.5 = 9.63 ppg

Please find the Excel sheet for calculating ECD (engineering calculation)