This articles demonstrates how to determine pressure losses through drill string.

To determine pressure drop while the drilling mud is passing through a circular pipe (drill pipe and drill collar), you can calculate pressure loss with the following equation:

**Assumptions:**

Turbulent viscosity = 3 cp

Friction factor = 0.378(Q/D)^{-0.14}

The first equation has a coefficient (C) to take into account the friction and the geometry of the bore ID.

Where:

P = pressure loss, psi

L = length of pipe, ft

W = mud density, ppg

Vf = viscosity correction factor

PV = plastic viscosity, centipoises

Q = flow rate, gpm

Di = inside diameter of pipe, inch

C = general coefficient for internal diameter of pipe

**Determine the pressure loss in the drill string based on the following information**

Drill pipe length = 5000 ft

ID of drill pipe = 3.34 inch

Drill collar length = 500 ft

ID of drill collar = 2.8 inch

Mud Weight = 9.5 ppg

Plastic Viscosity = 12 centipoise

Flow rate = 600 gpm

Pressure loss in the drill string composes of two parts which are pressure loss in **drill pipe** and **drill collar**.

We can write the relationship like this:

**Pt = Pdp + Pdc**

Where; Pt = total pressure loss in drill string

Pdp = pressure loss in drill pipe

Pdc = pressure loss in drill collar

**Determine pressure loss in drill pipe with following steps:**

Pdp = 1254

**Determine pressure loss in drill collar with following steps:**

Pdc = 295

Pt = 1254 + 295 = 1,549 psi

**Total pressure loss in the drill string equates to 1,549 psi.**

**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 Engineers.

Hi,

The above formula is valid for all units?, for example the MW in sg and length of DP in meter, can we still use the above formula to calculate the pressure loss in drill pipe?

Thanks.

Luis

This is specially for oilfield unit. If you want to calculate pressure loss in the drill string, please follow the following equation. Pressure Losses Through Drill String Calculation

i think this advance step i need the first step

because i’m training

please help me

Thanks & Best Regards