This experiment aimed to determine the viscosity of a drilling mud composed of bentonite and water using a viscometer. A mud was prepared and mixed, then tested using a rotational viscometer to obtain readings at 600 RPM and 300 RPM. Equations were used to calculate the apparent viscosity, plastic viscosity, and yield point from the readings. The results found the apparent viscosity was 77.5 cP, plastic viscosity was 3 cP, and yield point was 149 lb/ft2. In conclusion, a rotational viscometer can be used to determine important rheological properties of drilling mud.

1. Soran University
Faculty of Engineering
Department of Petroleum Engineering
Drilling Engineering I [ PETE 308]
Title: Drilling Fluid Viscometer
Experiment No.: 5
Name: Muhammad Sulaimon Rasul
Group: B2
Date: 14 OCT 2019
Supervisors: Jagar Ali, Fouad Yossifi, Rawezh Najat

2. Contents
Aim………………………………………………………………………………………….…….1
Theory…………………………………………………………………………………….…….…1
Apparatus…………………………………………………………...…………………………..…3
Procedure………………………………………………………………………………………….4
Calculation………………………………………………………………………………...………5
Result and Discussion……………………………………………………………………………..6
Conclusion………………………………………………………………………………………...6
References…………………………………………………………………………………………7
List of Figures
Figure 1. Bingham plastic model fluid behavior..……………………. ………………………….2
Figure 2. Electronic mud mixer………….…………………………………...….………….….…3
Figure 3. Mud balance………………………………………………..………….……….……….3
Figure 4 Beaker. …………………………………………….………..........…………….….…….3
Figure 5 Lab Spatula ……………….…….….…………………….…………………………..….3
Figure 6 Rotational Viscometer …...…………………………….……………….……………….3
Figure 7 Rotational Viscometer Diagram……..…………………………………………………..4
List of Tables
Table 1: Experimental and Theorical Results……………………………………………………..6

3. Aim
The aim of experiment is finding a drilling mud viscosity which composed of bentonite and water
using a viscometer.
Theory
Drilling mud is a mixture of water and mud (Clay) addition to some other minerals and special
chemical materials called “additives” (Kate, 1998), that used with water and mixed to maintain
well stability during the process of drilling. Sometimes mud can be non-aqueous regarding to well
condition that can be Oil-Base Mud used. A Successful drilling operation is requiring a good
quality of drilling fluid (Darley et al.,1988).
Rheology is a science which deals with the deformation, flow, and the viscosity of material under
the stress condition. Rheology can integrate the study of liquid and solid phases but most cases it
will deal with problems which related to thick liquids or pasty solids. One of the most important
properties that rheology deals with is viscosity. Viscosity is a of fluid to flow; which determines
the movement speed of the fluid, the higher fluid viscosity means slow movement of that fluid.
The small additional amount of a substance in suspension or solution can increase the viscosity of
fluid. The highly fluid viscosity of fluid which greater than gas viscosity is due to the molecular
attraction and closer in liquid phases. Also, should note that the viscosity is inversely varies with
temperature (Björn, 2012).
Drilling fluids can be classified into two groups: Newtonian and Non-Newtonian fluids (Balhoff
et al, 2011).
1. Newtonian Fluids: The fluid used to call Newtonian when its independent of pressure
applied, in other words the deformations are directly proportional to the stresses. Perfect
Newtonian fluid do not exist in real life, it should be assumed a fluid such as water are
common conditions in Newtonian or approaching which water becomes non-Newtonian in
height pressure case. Fore Newtonian fluids the apparent viscosity maintains a liner
relationship between applied stress and strain.
2. Non-Newtonian Fluids: unlike Newtonians, they are fluids that do not show a liner
relationship between applied stress and strain (Björn, 2012).
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4. Viscosity measurement:
Rheological properties such as apparent viscosity, plastic viscosity, yield point and gel strengths
of a non-Newtonian fluid in oil industry; can be measured using the Bingham Plastic mathematical
model (Bingham, 1922). Equations above can calculate these three rheological properties (Yield
point, Apparent viscosity, Plastic Viscosity) from VG meter reading (e.g., R300 and R600).
…………………………...………………………………………………(1)
………………………..……………………..……………………………..(2)
………………………………………….……………………...………….(3)
Where:
PV = plastic viscosity (cP)
YP = yield point (lb/100 ft2)
µa = apparent viscosity (cP).
Figure 1. Bingham plastic model fluid behavior. the curve intercept point with the shear stress,
which is called the yield point, should be more than zero (Azar, 2007).
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5. Apparatus and Materials
Apparatus
• Electronic mud mixer: Is a device used to mix liquid with solid particles. Shown in figure
2.
• Lab Spatula: Used to mix mud and water manually. Shown in Figure 5.
• Beaker: is a cylindrical container used to measure volume of a liquid. Shown in Figure 4.
• Mud balance: is a device used to measure mud density. Shown in Figure 3
• Rotational Viscometer set: Is a device used to measure viscosity of drilling fluid using
rotational technic. Shown in Figure 6 and Figure 7.
Materials
• Water.
• Mud.
Figure 2. Electronic
mud mixer
Figure 4. BeakerFigure 3. Mud balance
Figure 5. Lab Spatula
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Figure 6. Rotational
Viscometer.

6. Procedure
1. A drilling mud should be prepared and for being sure its fully mixed, should bring it to
mud mixer, if it was about to stuck; add some water to the mud for lowering density.
2. After mud was good mixed, clean and dry all viscometer parts such as rotor, bop, and cup
(to remove rotor: rotate clockwise and pull down, to replace rotor: align slot and groove
with lock pin, then push upward and lock into place by turning anti-clockwise).
3. Now fill the mud into the cup until the marked line on the cup.
4. Tight rotor and inner cylinder shaft.
5. Then put the cup on the stand and be sure all pines have fixed to the holes.
6. Now raise the cup using a stand base until the mud covers the line mentioned on the rotor.
7. Turn on gear switch and give 600-300 RPM on rotary speed setting.
8. Now using the motor speed switch (toggle) make it on 600RPM.
9. Read number on Deflection Dial and record it.
10. Now switch the speed to 300 RPM.
11. Read the Deflection Dial and record it.
12. Use the equations 1, 2, and 3 to find the rheological properties value.
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Figure 7. Rotational viscometer diagram. There are some main parts such as (Torsional
spring, Inner cylinder shaft bearing, Rotor, Cup, and Bob) and some others can be varying
between the device models.

7. Calculation
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8. Result and Discussion
Table 1: Experimental and Theorical Results
Materials Volume (cc) Density (Ib/gal)
Deflection Dial
No
Drilling Mud 400 8.55 -
At 600 RPM - - 155
At 300 RPM - - 152
Viscosity Measurements
Apparent Viscosity 77.5 cP
Plastic Viscosity 3 cP
Yield Point 149 Ib/ft2
Regarding to the table 1, a drilling mud was prepared with the volume of 400 cc using a beaker
and the density measured with a mud balance (Figure 3) in ppg`s. For the deflection dial number
at 600 RPM was measured using a viscometer while switch on 600-300 RPM, and also for the 300
RPM has the same procedure. The section of “Viscosity Measurements” in the Table 1, the
apparent viscosity has the value of 77.5 cP which calculated by putting 600RPM deflection dial
number to the equation (1). The plastic viscosity has measured regarding to both 600-300 RPM
values by putting to the equation (2) which gives a value in cP. Measuring yield point is another
rheological property which experimentally calculated using a viscometer by putting the values of
300 RPM and plastic viscosity to the equation (3) which gives a number in Ib/ft2
. It should be
noted that the deflection dial while its measuring must be fixed on a value then being recorded and
the viscometer can be calibrated before.
Conclusion
This experiment can conclude that, rheological properties such as mud viscosity and yield point
are a very important parameters for a drilling mud and by using a rotational viscometer with some
equations as mentioned can determine apparent and plastic viscosity and also the yield point.
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9. References
Azar, J.J., (2007): Samuel, G.R. Drilling Engineering; PennWell books: Tulsa, OK, USA.
Balhoff, M.T.; Lake, L.W.; Bommer, P.W.; Lewis, W.E.; Weber, M.J.; Calderin, J.M.,
(2011). Rheological and yield stress measurements of non-Newtonian fluids using a
Marsh Funnel. J. Pet. Sci. Eng., 77, 393–402. [CrossRef]
Bingham, (1922). E.C. Fluidity and Plasticity; McGraw-Hill: New York, NY, USA;
Volume 2.
Björn, A., Segura de La Monja, P., Karlsson, A., & Ejlertsson, J. (2012): Rheological
Characterization.
Darley, H.C.H. and Gray, G.R. (1988): The composition and Properties of Drilling and
Completion Fluids. 5th Ed. Gulf Publishing Company, Houston Texas. pp 110.
Kate, V.D. (1998): Drilling Fluids, Mud Pumps and Conditioning Equipment.
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