Darcy's law

[@jeremiah7167]

Good evening sir. Why don't add minus in darcy law for radial flow?

[@BoffyBlunt]

You do, if you consider the flow out from the well - in the direction of increasing radius. However, we normally consider radial flow out of a production well, so oil flowing in the direction of decreasing radius is considered positive. Think about this - you need to define the terms so that flow is from high to low pressure.

[@jeremiah7167]

Thank you for your answer, sir.