Funnel Viscosity and Rheology of Drilling Mud

The funnel viscosity is time in second of drilling mud flowing through the Marsh Funnel. The Marsh funnel is dimensioned so that the outflow time of one quart of freshwater (956 cc) at a temperature of 70 F +/- 5 F (21 C +/- 3 C) in 26 +/- 0.5 seconds. For all drilling mud, especially oil base mud, temperate affects on the viscosity of base fluid. The base fluid will be less thick once the temperature increases. It means that the funnel viscosity will decrease. The funnel viscosity measures at only one rate of shear but the temperature each time of measurement is not constant. This is the reason why the viscosity measured from the Marsh Funnel does not represent the true mud viscosity. On the drilling rig, this measurement of the mud viscosity is still useful because it is a quick and simple test for observing trends of drilling fluids.

In order to use the funnel viscosity effectively, clickfunnels review 2018 personnel must record the values frequently. Please remember that only single point of the funnel viscosity cannot tell you anything about a condition of drilling fluid in the well.

Rheology is the study of flow and deformation of fluid. There are several rheology values such as gel strength, plastic viscosity (PV), and yield point (YP).

This following information is determined by the rheological measurements from a mud test.

• Equivalent circulating density

• Hydraulic efficiency

• Hole cleaning efficiency

• Surge and Swab pressure

• Pressure loss in the system

• Pressure required to break circulation

Typically, the plastic viscosity (PV) and the yield point (YP) will increase as mud weight increases. In addition, mud weight has more effect on PV than YP.

These two parameters have a direct relationship. If you have high funnel viscosity, you will have high rheology. Therefore, for good drilling practices, you need to keep tracking these two parameters closely and try to keep the drilling mud in a specification otherwise you may have bad drilling problems.

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