mud testing



The purpose of this manual is two fold: first to acquaint the Drilling engineering students with the basic techniques of formulating, testing and analyzing the properties of drilling fluid and oil well cement, and second, to familiarize him with practical drilling and well control operations by means of a simulator. To achieve this objective, the manual is divided into two parts.


The first part consists of seven experiments for measuring the physical properties of drilling fluid such as mud weight (density), rheology (viscosity, gel strength, yield point) sand content, wall building and filtration characteristics. There are also experiment for studying the effects of, and treatment techniques for, common contaminants on drilling fluid characteristics. Additionally, there are experiments for studying physical properties of Portland cement such as free water separation, normal and minim-um water content and thickening time.

In the second part, there are five laboratory sessions that involve simulated drilling and well control exercises. They involve the use of the DS-100 Derrick Floor Simulator, a full replica of an actual drilling rig with fully operations controls, which allow the student to become completely absorbed in the exercises as he would in an actual drilling operation. The simulator has realistic drilling rig responses that are synchronized to specific events, like rate of penetration, rotary table motion, and actual rig sounds such as accumulator recharge, break draw works, etc.

It is hoped that the material in this manual will effectively supplement the theory aspect presented in the main course.




















Preface …………………………………………………………………...…....i

Table of Contents …………………………………………………..………...ii

Laboratory Safety Instructions……………………………………………...iii

 Experiment No. 1: Mud Weight, Marsh Funnel Viscosity and pH...................................... 4

 Experiment No. 2: Mud Rheology Test ……………………………………....11

 Experiment No. 3: Filtration, Wall Building and Resistivity ………………..16

Experiment No. 4. Mud Weight Control ……………………………………..21

Experiment No. 5. Drilling Fluid Contamination Test………………………. 24

Experiment No. 6. Solid, Liquid Content and Emulsion Characteristic                                of Drilling Fluids………….…………………………………………………27

















Safety in the laboratory must be of vital concern to all those engaged in experimental science work. It is therefore the responsibility of everyone to adhere strictly to the basic safety precautions provided and to avoid any acts of carelessness that can endanger his life and that of others around him. It is equally important to always abide by all the instructions for conducting the experimental work during the laboratory sessions. Below are some guidelines for general laboratory safety and procedures:


1-All students must be familiar with the locations and operational procedures of the

Emergency Shower, Fire Extinguishers, Gas Masks and Fire Blankets. These safety

devices pictured below.


2- Laboratory coats, safety glasses and safety shoes MUST be worn at all times during the laboratory session  NOTHOABS and open sandals are allowed during the laboratory sessions.


3- Eating, drinking and smoking are strictly. PROHIBITED in the laboratory at all times. Laboratory glassware should NEVER be used for drinking purpose.


4- Report any injury immediately for First Aid treatment, no matter how small.


5- Report any damage to equipment or instrument and broken glassware to the laboratory instructor as soon as such damage occurs.



















       1.1.1.     MUD WEIGHT or DENSITY   TEST:

Theory :


The density of the drilling fluid must be controlled to provide adequate hydrostatic head to prevent influx of formation fluids, but not so high as to cause loss of circulation or adversely affect the drilling rate and damaging the formation.

Normal pressure gradient by water is equal to (0.433 psi/ft) and equal to 433 psi/1000 ft.


Test Equipment


The Baroid Mud Balance as shown below is used to determine density of the drilling fluid. The instrument consists of a constant volume cup with a lever arm and rider calibrated to read directly the density of the fluid in ppg (water 8.33), pcf (water 62.4), specific gravity (water = 1.0) and pressure gradient in psi/1000 ft. (water 433 psi/1000 ft.)




Figure 1.1: Typical Mud Balance




1.Remove the lid from the cup, and completely fill the cup with water.

2.Replace the lid and wipe dry.

3. Replace the balance arm on the base with knife-edge resting on the fulcrum.

4. The level vial should be centered when the rider is set on 8.33. If not, add to or remove shot from the well in the end of the bream.


Test Procedure

  1. Remove the lid from the cup, and completely fill the cup with the mud to be tested.


  1. Replace the lid and rotate until firmly seated, making sure some mud is expelled through the hole in the cup.


  1. Wash or wipe the mud from the outside of the cup


  1. Place the balance arm on the base, with the knife-edge resting on the fulcrum.


  1. Move the rider until the graduated arm is level, as indicated by the level vial on the beam.


  1. At the left-hand edge of the rider, read the density on either side of the lever in all desired units without disturbing the rider.


   7.     Note down mud temperature corresponding to density.





Theory :

The viscosity of a fluid is defined as its resistance to flow. The desired viscosity for a particular drilling operation is influenced by several factors, including mud density, hole size, pumping rate, drilling rate, pressure system and requirements, and hold problems. The indicated viscosity as obtained by any instrument is valid only for that rate of shear and will differ to some degree when measured at a different rate of shear. For field measurements the marsh funnel has become the standard instrument. For laboratory, the Fann V-G meter, a direct indicating rotational multi-speed instrument, has become the standard, allowing measurements of plasticviscosity, yield point, gel strength to be made

The Stormer viscometer is still, however, used to some extent for single point (apparent) viscosity and 0-10 min. gel.


Test Equipment

The Marsh Funnel is a device that is common to every drilling rig. Details of the Marsh Funnel and receiving cup are shown in Figures 1-2, and 1-3. The viscosity is reported in seconds allowed to flow out of the funnel. API specifications call for 1500 ml and one quart (946) ml out. For API water at 70 F + 0.5 oF  = 26 + 0.5 sec. The Marsh Funnel measures the apparent viscosity.


Calibration :

Fill the funnel to the bottom of the screen (1500 ml) with water at 70 F (plus or minus 0.5 F) time of outflow of the quart (946 ml) should be 26 seconds plus or minus 1/2 second



Figure 1.2: Marsh Funnel and One-liter Cup







Fann VG Meter


Test Procedure



1.    With the funnel in an upright position, cover the orifice with a finger and pour the freshly collected mud sample through the screen into a clean, dry funnel until the fluid level reaches the bottom of the screen (1500 ml).

2.   Immediately remove the finger from the outlet and measure the time required for the mud to fill the receiving vessel to the 1-quart (946 ml) level.

3.    Report the result to the nearest second as Marsh Funnel Viscosity at the temperature of the measurement in degrees Fahrenheit or Centigrade.



Theory :

The acidity and the alkalinity of the drilling fluid can be measured by the concentration of the (H+) ion in the fluid. As for instance, if H+ is large
(I x 10-1), then the (OH-) hydroxyl concentration is very low (1 x 10­13),the solution is strongly acidic. If the (OH-) concentration is (1 x 10­1)very high then (H+) concentration is very low then the solution is strongly alkaline. The pH of a solution is the logarithm of the reciprocal of the (H+) concentration in grams moles per liter, expresses as:

PH = 

Example: If the solution is neutral then H+ and OH- concentrations are the same equal to 1 x 10-7.

PH = log


Therefore, if the pH of a mixture drops from 7.0 to 6.0, the number of (H+) increase ten times.

The pH of a mud seldom is below 7 and in most cases fall between 8 and 12.5 depending upon the type of mud. The pH is important because the pH affects the solubility of the organic thinners and the dispersion of clays presents in the mud.



Methods of measuring pH in the laboratory:


1.      The pH Paper: The pH papers strips have dyes absorbed into the paper display certain colors in certain pH ranges. It is useful, inexpensive method to determine pH in fresh water muds. The main disadvantage is that high concentrations of salts (10,000 ppm chloride) will alter the color change and cause inaccuracy.


2.       The pH Meter: The pH meter is an electric device utilizing glass electrodes to measure a potential difference and indicate directly by dial reading the pH of the sample. The pH meter is the most accurate method of measuring pH.


Figure 1.3 : Hydrion pH Dispensers .



Figure 1.4 : pH Meter



The Laboratory Test:


1-           Take 2 samples of mud from each of the mud tanks.


2-           Stir the samples for 2 minutes and determine:

                          (a)       The Mud Weight

                        (b)      Marsh Funnel Viscosity in seconds

                          (c)      pH value using      - pH meter

-          Hydrion papers



(Density, Viscosity, pH)

Room Temp :            °F/          °C



Mud Weight



(Marsh Funnel)


(Hydrogen Ion Conc.')








PH Meter




















Answer the following:

1..         List any five (5) very important functions of the drilling fluid?



2.        What requirements should a drilling fluid meet?



3.           Using the mud weights (ppg) obtained for Samples #1 and 2 of your experiment, calculate, how much hydrostatic pressure that each sample will exert on a formation at a depth of 10,000 ft.



4.        What is the difference between Over-balance and Under-balance?



5.        Estimate the mud weight needed to balance a formation pressure equivalent to 10,000 ft. depth with 0.561 psi/ft. pressure gradient

2.  EXPERIMENT   NO. 2  


2.1.            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



2.1.1.      VISCOSITY:


          Theory :


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.


                                    300                           600

 RPM SETTING            

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.



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.



  1. 1.              Plastic viscosity (in centipoises-up):



Plastic Viscosity = PV= 600 RPM reading  -  300 RPM Reading


  1. 2.              Apparent Viscosity (in centipoises-cp):



    Apparent Viscosity = AV = 600 RPM Reading    2



  1. 3.              Yield Point (in lb/100 ft2):



Yield Point = Y.P = 300 RPM Reading  -   Plastic Viscosity


2.1.2.      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.


Gel Strength Measurement Procedures

  1.    Stir a sample at 600 RPM for about 15 seconds.
  2.    Turn the RPM knob to the STOP position.
  3.    Wait the desired rest time (normally 10 seconds or 10 minutes).
  4.    Switch the RPM knob to the GEL position.
  5.    Record the maximum deflection of the dial before the Gel breaks, as the

Gel strength in lb/ 100 ft2.        (lb/100 ft25.077 = Gel strength in dynes/cm2).


2.1.3.     YIELD POINT(YP):



This is the measure of the electro-chemical or attractive forces in the mud under flow (dynamic) conditions. These forces depend on (1) surface properties of the mud solids, (2) volume concentrations of the solids and (3) electrical environment of the solids. The yield point of the mud reflects its ability to carry drilled cuttings out of the hole.






                                    YP = 300 RPM - Plastic Viscosity






Experimental Procedure

1.     Obtain a recently agitated mud sample from each of mud tanks (1) and


2.       Using the Baroid Rheometer, obtain dial readings at 3, 300 and 600



3.   By means of the Theological calculations procedure, determine the Apparent and Plastic Viscosities, Yield Point and initial 10 sec. and final 10-minute Gel Strength parameters.


4.    Tabulate your results as in the given table below:
















Gel strength lb/ 100 ft2








lb/100 ft2



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