PetengCalculators

EQUIVALENT CIRCULATION DENSITY

ECD Of Circulating Mud

THEORY & FORMULAE

Equivalent Circulation Density Of Mud

The equivalent circulation density can be interpreted as the density of a hypothetical fluid, which in static conditions and at any depth produces the same pressure as a given drilling mud in dynamic conditions.

ECD is calculated using the steady-state model based on the Bingham plastic behavior of drilling mud. The method involves estimating and summing the frictional pressure losses arising from the normal circulation of mud outside the drill string. These pressures losses are added to the mud's hydrostatic pressure and converted to density using the true vertical depth.

The annular velocity around the drillpipe is calculated, followed by the critical velocity. If the annular velocity is less than the critical velocity, the laminar pressure losses equation is applied. If otherwise, the turbulent pressure loss equation is applied. The process is then repeated for the drillcollar section. The relevant equations are:

Where:

   Q_p = mud circulation rate, gallons/min.
   V_c = critical velocity, ft/min.
   v = annular velocity, ft/min
   ΔP = pressure loss, psi
   ρ = mud weight, ppg
   n = derived parameter of mud, dimensionless
   K = derived parameter of mud, dimensionless
   θ₃₀₀ = 300 viscometer dial reading
   θ₆₀₀ = 600 viscometer dial reading
   θ₃₀₀ = PV + YP
   θ₆₀₀ = θ₃₀₀ + PV
   PV = plastic viscosity of mud, cps
   YP = yield point of mud, lb/100ft²
   L = length of pipe or collar, ft
   TVD = true vertical depth, ft
   D_h = hole diameter, inches
   D_p = drill pipe or collar OD, inches

The total pressure can be converted to the equivalent circulation density via the expression:

ρ_ecd = 19.23*ΔP_total / TVD.

BIBLIOGRAPHY

Moore P.L.; Drilling Practices Manual; Pennwell Books, Tulsa, Oklahoma, 1986, chap. 7.

Lapeyrouse N.J.; Formulas & Calculations for Drilling, Production and Workover; Gulf Professional Publ. Co, Amsterdam, 2002, chap.5.

Mitchell B.; Advanced Oilwell Drilling Handbook; Mitchell Engineering, Lakewood, Colorado, 1995.

Mud weight		ppg
Plastic viscosity		cps
Yield point		lb/100ft²
Hole diameter		in
Drill pipe OD		in
Drill pipe length		ft
Drill collar OD		in
Drill collar length		ft
True vertical depth		ft
Circulation rate		gpm

	Pressure losses (psi)	Annular Velocity (ft/min.)	Critical Velocity (ft/min.)	Flow Regime
♦ Drill pipe
♦ Drill collar
♦ Total
♦ ECD (ppg)