Mud Rheology Test

Viscosity, Gel Strength and Yield Point


Rheology refers to the deformation and flow behavior of all forms of matter. Certain rheologic measurements made on fluids, such as viscosity, gel strength, etc. help determine how this fluid will flow under a variety of different conditions. This information is important in the design of circulating systems required to accomplish certain desired objectives in drilling operations.


Viscosity is defined as the resistance of a fluid to flow and is measured as the ratio of the shearing stress to the rate of shearing strain.

Two types of fluid characterizations are:

  1. Newtonian (true fluids) where the ratio of shear stress to shear rate or viscosity is constant, e.g. water, light oils, etc. and
  2. Non-Newtonian (plastic fluids) where the viscosity is not constant, e.g. drilling muds, colloids, etc.
Types Gel Strength Mud


Figure 2.1: Flow Curves of Newtonian and non-Newtonian Fluids


Figure 2.1: Flow Curves of Newtonian and non-Newtonian Fluids

Test Equipment

The Baroid (Model 286) Rheometer is a coaxial cylindrical rotational viscometer, used to determine single or multi-point viscosities. It has fixed speeds of 3 (GEL), 100, 200, 300 and 600 RPM that are switch selectable with the RPM knob.

Viscosity Measurement
Figure 2.2: Variable Speed Rheometer

Additionally, the same switch set to the VAR position enables speed selection of between 3 and 625 RPM, by manual adjustment of the variable knob.


  1. Place a recently agitated sample in the cup, tilt back the upper housing of the rheometer, locate the cup under the sleeve (the pins on the bottom of the cup fit into the holes in the base plate), and lower the upper housing to its normal position.
  2. Turn the knurled knob between the rear support posts to raise or lower the rotor sleeve until it is immersed in the sample to the scribed line.
  3. Stir the sample for about 5 seconds at 600 RPM, then select the RPM desired for the best.
  4. Wait for the dial reading to stabilize (the time depends on the sample's characteristics).
  5. Record the dial reading and RPM. RHEOLOGICAL CALCULATIONS
  6. Plastic viscosity (in centipoise-up):

Plastic Viscosity = j p = 600 RPM reading - 300 RPM Reading

2. Apparent Viscosity (in centipoise-cp):

Apparent Viscosity = ja = 600 RPM Reading

Yield Point = Y. P. = 300 RPM Reading - Plastic Viscosity (B) GEL STRENGTH: Theory

The Baroid Rheometer is also used to determine the Gel strength, in lb/100 sq. ft., of a mud. The Gel strength is a function of the inter-particle forces. An initial 10-second gel and a 10-minute gel strength measurement give an indication of the amount of gellation that will occur after circulation ceased and the mud remains static. The more the mud gels during shutdown periods, the more pump pressure will be required to initiate circulation again.

Most drilling muds are either colloids or emulsions which behave as plastic or non-Newtonian fluids. The flow characteristics of these differ from those of Newtonian fluids (i.e. water, light oils, etc.) in that their viscosity is not constant but varied with the rate of shear, as shown in Figure 2.2. Therefore, the viscosity of plastic fluid will depend on the rate of shear at which the measurements were taken.

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  • arnor
    How mud test drilling?
    9 years ago
  • luisa davide
    How to measure the viscisity at 600 rpm?
    8 years ago
  • iggi
    How to test mud rheology?
    8 years ago
  • geoffrey
    How to check mud rheology?
    8 years ago
  • ciaran mcintyre
    Why plastic viscosity is 600rpm300rpm?
    8 years ago
  • teigan
    What kind of fluid is used in drilling / non newtonian or newtonian fluid?
    8 years ago
  • gianni davide
    How to measure mud rheology in oil well?
    6 years ago
  • christian
    How to check rheology of drilling mud?
    4 years ago
  • max
    How to take gel strength readings from rheology test 3, 6,100, 200, 300, & 600 rpm?
    4 years ago
  • may
    Is gel strength & plastic viscosity related?
    4 years ago
  • jessika
    What are the procedures of determining apparent plastic and yield point viscosity?
    3 years ago
  • Sonja
    What is the significance for determining the rheological property of mud?
    3 years ago
  • Milton
    How to do theology test and gel strength of a drilling mud?
    2 years ago
  • jennifer klug
    What is the standard mud viscocity?
    2 years ago
  • semret
    How to find viscosity of mud using rheometer at 600rpm?
    2 years ago
  • Karly
    Can rheometer used to measure mud properties?
    2 years ago
  • Alessandra
    Why it is that the plastic viscosity, Yield point, and gel strength of the mud samples?
    2 years ago
  • ABI
    What is the importance of plastic viscosity in drilling fluid?
    2 years ago
  • Daniel
    How viscometer is used to determine the viscosity of drilling fluid?
    2 years ago
  • klaus
    How do we conclude mud Rheology test experiment?
    2 years ago
  • kaija
    Why viscometer is used in drilling engineering?
    2 years ago
  • lucas
    How to determine rheological properties on 8speed viscometer?
    1 year ago
  • mark kocher
    How does rheology deteremine the performance of drilling mud?
    1 year ago
  • sebhat isaias
    What is the significance of yield point in drilling?
    1 year ago
  • markus
    What are the aims and objective of mud rheology experiment?
    1 year ago
  • veli
    What is the determination of rheological properties of mud?
    9 months ago
  • teresa
    What does dial reading on rheology test tell you?
    7 months ago
    What is reheology of oil based mud?
    7 months ago
  • kevin
    What speed are mud gels recorded at?
    7 months ago
  • zack
    What is rheology of a drill in fluid?
    6 months ago
  • meaza
    What is the importance of a 10 sec gel strength test in mud lab for pertroleum engineers?
    6 months ago
    How to check rheology of drilling fluids?
    6 months ago
    What is the unit of yield point in viscometer?
    5 months ago
  • matthias
    How to check mud type oilfield?
    3 months ago
  • daisy
    How to perform viscosity test on drilling fluids?
    2 months ago
  • quintilio
    What is the laboratory aim of determining mud rheological properties?
    2 months ago
  • fulvus
    What is the inroductory /theory note in laboratory in determining mud rheological properties?
    2 months ago
  • Flavus
    What is the aims of determining mud rheological properties?
    1 month ago
  • Kirstin
    Why do you have to adjust your mud pH in rheology practical?
    1 month ago

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