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**Equivalent Circulating Density (ECD) **is the effective density that combines current mud density and annular pressure drop. ECD is vital for drilling engineering since it limits how depth of each section to be drilled and leads to losses.

The equivalent circulating density formula is shown below

**Equivalent Circulating Density (ECD) in ppg = (annular pressure loss in psi) ÷ 0.052 ÷ true vertical depth (TVD) in ft + (current mud weight in ppg)**

**Example:**

Annular pressure loss = 400 psi

True Vertical Depth = 8,000 ft

Current mud weight in ppg = 10 ppg

ECD in ppg = (400 psi ÷ 0.052 ÷ 8,000 ft) + 10.0 ppg

ECD = 11.0 ppg

Please find the Excel sheet to calculate equivalent circulating density (ECD)

**Ref books: **Lapeyrouse, N.J., 2002. Formulas and calculations for drilling, production and workover, Boston: Gulf Professional publishing.

Bourgoyne, A.J.T., Chenevert , M.E. & Millheim, K.K., 1986. SPE Textbook Series, Volume 2: Applied Drilling Engineering, Society of Petroleum Engineers.

Mitchell, R.F., Miska, S. & Aadny, B.S., 2011. Fundamentals of drilling engineering, Richardson, TX: Society of Petroleum Engineer

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I love well control and answers.

Why you only use annular pressure drop?

what about pressure loss inside the pipes?

Mahsun,

The reason why using annular pressure drop is the direction of pressure drop acting downward which cause additional pressure to the bottom hole. The drill pipe pressure loss is acting upward therefore it cannot be used for ECD calculation.

Regards,

Shyne.

How can we use this during cement to calculate the ECD especially during cement displacement.

If you want to use for cement displacement, you need to separate each section of fluid in the annuals in order to calculate annular pressure loss.

plenty thanks to you all. its great to be part of this group

Can we calculate the ECD if the surface pressure is not equal to zero? Or the surface pressure does not matter?

Yes. You can add surface pressure into the calculation. This concepth is used in managed pressure while drilling.

Whoa I love this platform. Please I would like to know the relationship between ECD and EMW