Reynold number is the important figure because it demonstrates the flow regimes of drilling mud as laminar, transition or turbulent flow in annulus of the wellbore. In order to correctly calculate the Reynolds number, you need to use the effective viscosity, µea, which we already discuss about it from the previous topic.

The following equation is for Reynolds number in the annulus.

Where:

Rea = Reynold Number in the annulus

Va = Annular velocity, ft/min

Dh = Diameter of wellbore, inch

Do = Outside Diameter of tubular, inch

W = mud weight, ppg

µea = effective viscosity in the annulus, centi-poise

na = power law constant

**For more understanding, please following this example, Reynold number calculation.**

Va = 6 ft/min

Dh = 8.5 inch

Do = 5 inch

W = 9.5 ppg

µea = 42.53 centi-poise

na = 0.514

Rea = 3,781

The next topic will demonstrate you how to relate the Raynold’s number into flow regime.

**Reference: Drilling Hydraulic Books**

how we can know yeld point and plastic vescosity?

Hi Reben,

Please find the answer below.

Plastic Viscosity (PV) = Reading at 600 rpm – Reading at 300 rpm

Yield Point (YP) = Reading from a viscometer at 300 rpm – Plastic Viscosity (PV)

How recover the core sample (fully sand ) from the depth 500ft to 700ft ?

I don’t have an experience about this topic. Sorry about that.

I was looking at your example calculation. you list the annular velocity in the formula with dimentions of ft/minute but your example data in listed as ft/second. is that a whoops.

Hi Curtis,

Thanks for helping check my typo. It should be ft/min.

Regards,

Shyne

You were correct the first time. It should be ft/sec NOT ft/min.

Hey folks at DrillingFormulas,

I’ve been using your formula above to try and build an excel calc.

But i get the answer Rea 6430 from your example.

Could you show the calculation broken down further? or offer any other possible help.

Thanks

Matt.

Sorted it! 🙂