Frictional Pressure Loss Components in the Rig Circulating System

Frictional Pressure Loss: Frictional Pressure Loss is pressure loss created by fluid flowing through the flow path. It is a function of fluid property (density, viscosity, gel strength), velocity of fluid, characteristic of flow path (hole size/drill string size). Frictional pressure loss affects on pump pressure because higher frictional pressure loss, higher pump pressure is required to maintain the pump rate.

In order to clearly demonstrate the pressure loss component in the drilling rig system, the diagram below describes pressure loss each flow path of drilling fluid in the total rig circulation system.

The Diagram of Frictional Pressure Loss in Circulation System

Parameters, which affect pump pressure, are as follows:

1. Fluid properties especially mud weight, viscosity, gel strength and yield point affects directly on pump pressure. Higher mud weight, viscosity, gel strength and yield point, higher pump pressure requires to maintain pump rate.

2. Pump rate is another factor that affects directly on pump pressure. This is a basic concept when higher pump rate is needed; higher pump pressure is required.

3. Hole size/drill string size: Smaller internal diameter of both hole and drill string, higher velocity of fluid flow is created at same pump rate. Higher velocity creates more frictional pressure loss. High pump pressure is required in order to maintain pump rate because there is additional pressure loss due to smaller hole size and drill string.

4. BHA and Bit: Due to small inner area, BHA and bit can cause majority of pressure loss.  Hence, BHA design/selection and bit nozzle selection are critical for hydraulic design.

5. Well Depth: The deeper of the well is, the more pressure loss will occur . It means we need more pump capacity to achieve the drilling goal.  Depth of the well is based on geological targets underneath the earth by geologists. This part will influence on how to select the proper rig capacity in order to meet hydraulic proposes of the wells.

I hope this post will help you understand more about pressure loss in the drilling rig : )

Any comments are always welcome.