College of Science and Technology

School of Computing, Science and Engineering

Petroleum and Gas Engineering

LABORATORY REPORT

MODULE: Petroleum Exploration and Production LABORATORY TITLE: Laboratory Preparation of Drilling Mud

MODULE LECTURER: Dr. Lateef Akanji

REPORTED BY FULL NAME: Dakeipirim Wokoma

ROLL NUMBER: @00361272

SUBMISSION DATE: 11/04/2014 ACADEMIC SESSION: 2013/2014

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Abstract

Drilling fluid is a very crucial composite of the drilling operation. Performance and quality of fluid must

be constantly monitored if the drilling process is expected to run smoothly. This experiment discusses the

steps required to prepare a drilling fluid and how to test for certain quality indicators such as mud density

and other rheological properties.

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Table of ContentsAbstract.............................................................................................................................................i

List of Figures.................................................................................................................................iv

List of Tables..................................................................................................................................iv

Drilling Fluid Preparation................................................................................................................1

1.1 Introduction.....................................................................................................................1

1.2 Theory..............................................................................................................................2

1.3 Materials/Apparatus for Water Base Mud (WBM) Preparation...............................3

1.4 Experimental Procedure for WBM Preparation.........................................................3

Experiment 1....................................................................................................................................4

2.1 Objective..........................................................................................................................4

2.2 Mud Weight or Density – Theory..................................................................................4

2.3 Test equipment – Mud balance......................................................................................4

Calibration of Mud Balance...................................................................................................5

2.4 Test Procedure.................................................................................................................5

2.5 Marsh Funnel Viscosity – Theory..................................................................................5

Calibration..............................................................................................................................6

2.6 Test Procedure.................................................................................................................6

2.7 Hydrogen Ion Concentration (pH) – Theory................................................................6

The pH Paper:.........................................................................................................................7

The pH Meter.........................................................................................................................7

2.8 Data Analysis and Results..............................................................................................8

2.9 Discussion of Results.......................................................................................................8

Sources of Error......................................................................................................................8

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Questions................................................................................................................................8

Solution..................................................................................................................................9

2.10 Conclusion....................................................................................................................9

EXPERIMENT 2...........................................................................................................................10

3.1 Objectives.......................................................................................................................10

Introduction..........................................................................................................................10

3.2 Theory............................................................................................................................10

Mud Rheology......................................................................................................................10

3.3 Determination of Mud Viscosity – Theory.................................................................11

Fluid Characterization..........................................................................................................11

3.4 Test Equipment.............................................................................................................12

3.5 Procedure.......................................................................................................................12

3.6 Determination of Gel Strength – Theory....................................................................12

3.7 Procedure.......................................................................................................................13

3.8 Data and Analysis of Results........................................................................................13

3.9 Discussion of Results.....................................................................................................14

Sources of Error....................................................................................................................15

Questions..............................................................................................................................15

Solutions...............................................................................................................................15

Conclusion................................................................................................................................18

References......................................................................................................................................19

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List of FiguresFIGURE 1 - MUD BALANCE..............................................................................................................4

FIGURE 2 - MARSH FUNNEL.............................................................................................................5

FIGURE 3 - PH PAPER.......................................................................................................................7

FIGURE 4 - PH METER......................................................................................................................7

FIGURE 5 - SCHEMATIC OF FLUIDS................................................................................................11

FIGURE 6 - OFITE MODEL 800 VISCOMETER.................................................................................12

FIGURE 7 - GRAPH OF SHEAR STRESS VS RATE SHOWING CLASS OF FLUID AND YIELD POINT.....14

FIGURE 8 - VISCOSITY VS TEMPERATURE RELATIONSHIP FOR NAPHTHALENE.............................17

FIGURE 9 - VISCOSITY-TEMPERATURE RELATIONSHIP FOR WATER..............................................17

List of TablesTABLE 1 - TABLE OF RESULTS FOR DENSITY, MARSH FUNNEL AND PH READINGS.......................8

TABLE 2 - TABLE OF RESULTS FOR VISCOMETER READING..........................................................13

TABLE 3 - DIFFERENCE BETWEEN GEL STRENGTH AND YIELD POINT..........................................17

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Drilling Fluid Preparation

1.1 Introduction

Drilling fluids are an essential part of any drilling process with its primary function to remove the drilled

cuttings from the borehole whilst drilling and to prevent fluids from the formations being drilled into the

bored hole.

Types of Drilling Fluids

Water – Based Mud

Oil – Based Mud

Gaseous Drilling Fluids

Water –Based Mud: These are drilling fluids composed of water as the continuous phase of the system

and could be fresh water or salt water.

Oil –Based Mud: The continuous phase in this system is oil and they are mostly used for troublesome

formations.

Gaseous Drilling Fluids: This involves the use of pure gas or gas-liquid mixtures for drilling operation.

The use of this drilling fluid is not common and they are used for areas where formations are

impermeable

Functions of Drilling Fluids

Remove cuttings from wellbore

Prevent formation fluids flowing into the wellbore

Maintain wellbore stability

Cool and lubricate the bit

Transmit hydraulic horsepower to bit

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The ability of drilling mud to carry cuttings from the borehole to the surface and also avoid influx of

formation fluid into the borehole is determined by its density and viscosity. Hence the expected range for

these properties must be met in order to design a good drilling fluid.

1.2 Theory

This report discusses the preparation of water based mud (water being the continuous phase) with a

volume ratio of (80% water + 20% oil) liquids 370ml + 22.5g bentonite giving values as follows:

Precise volume of water: 0.8 x370=296 ml

Precise volume of oil: 0.2 x370=74 ml

Where two substances having different densities are mixed then the density of the mixture is a function of

the volume and density (weight) of the components of the mixture. Mathematically this relationship can

be expressed as follows:

V 1 D 1+V 2 D 2=(V 1+V 2 ) ( DR )=M 1+M 2

Where V1 = Volume of the 1st substance

V2 = Volume of the 2nd substance

D1 = Density of the 1st substance

D2 = Density of the 2nd substance

DR = Density of the resulting mixture

M1 = Mass of 1st Substance

M2 = Mass of 2nd Substance

From Density= MassVolume

In the case of a drilling mud, increasing the weight with a material such as barite can also be related in the

same manner.

V 1W 1+V 2W B=(V 1+W 2)(W 2)whereW B=Weight of barite

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1.3 Materials/Apparatus for Water Base Mud (WBM) Preparation

Water

Bentonite

Oil

Emusifying agent

Flocculant

Stirrer

Mud Balance

pH meter

pH strips

Marsh Funnel

Weighing scale

Mud mixer

Thermometer

1.4 Experimental Procedure for WBM Preparation

74ml of oil was added to 296ml of distill water in a conical flask or the cup of the stirrer to make

370ml of liquid, after which 22.5g of bentonite was added to the mixture.

The final mixture was stirred with the standard stirrer for 30mins. After 25mins stirring, the

lumped material adhering to the spindle of the stirrer or inside of the cup/container was scraped

down into the cup, then the stirring continued for another 5mins to make up 30mins.

After mixing the pH of the mud was checked and recorded as 8.6.

4ml of emulsifying agent (Vasaclean VB) and 4g of flocculant (NaCl) was added to the mixture

and stirred for about 2mins and recorded pH again as 7.1.

The pH of the mud was then adjusted to 9.5 ± 0.1 using phosphoric acid to reduce or caustic soda

to increase the pH and the mud sample was weighed in the mud balance.

At the end of the stirring time we transferred the samples to a sealed jar and aged the mixture for

16hrs at room temperature in the laboratory

After aging, the pH of mud was readjusted to 9.5, stirred for 5 minutes and the tests done.

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Experiment 1

2.1 Objective

The purpose of this laboratory work is to determine certain properties of a laboratory prepared drilling

mud such as;

Mud Weight or Density

Marsh funnel viscosity

Hydrogen ion concentration(pH)

2.2 Mud Weight or Density – 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 in order not to cause loss of circulation or adversely affect the drilling

rate and damaging or fracturing the formation. Normal pressure gradient by water is equal to 0.433psi/ft,

which is equivalent to 433psi/1000ft.

A mud balance can be used to determine the density of a drilling mud and is usually reported in pounds

per gallon (ppg), Ib/ft3, psi/1000ft and specific gravity (s.g). The density of a drilling mud must be

controlled to provide the necessary hydrostatic pressure to prevent influx of formation fluids.

2.3 Test equipment – Mud balance

The mud balance is used to measure the weight of a drilling fluid and consists of a constant volume cup

with a lever arm and rider calibrated to directly read the density of the fluid in ppg, specific gravity, and

pressure gradient (psi/1000ft).

Figure 1 - Mud Balance (Source: www.petroleumsupport.com retrieved April 4, 2014 from

http://petroleumsupport.com/drilling-fluid-test-on-field/mud-balance/)

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Calibration of Mud Balance

The lid from cup was removed and the cup completely filled with water.

The lid was replaced and wiped dry.

The balance arm was placed on the base with knife-edge resting on the fulcrum.

The level vial was centered when the rider was set on 8.33ppg as should be for water.

2.4 Test Procedure

The lid from the cup was removed and the cup completely filled with the mud to be tested.

The lid was replaced and rotated until it was firmly seated, making sure excess mud was expelled

through the hole in the cup

The mud around the lid and cup was wiped off and the balance arm placed on the base with the

knife-edge resting on the fulcrum

The rider was moved until the graduated arm was level, as indicated by the level vial on the

beam.

At the left-hand edge of the rider read the density on either side of the lever was all desired units

without disturbing the rider

2.5 Marsh Funnel Viscosity – Theory

A very simple device for measuring viscosity and apparent viscosity is measured in seconds by allowing

the mud to flow out of the funnel. The time it takes a volume of mud to flow from a cone through the

short tube is recorded.

Figure 2 - Marsh Funnel(Source: www.petroleumsupport.com retrieved April 4, 2014 from

http://petroleumsupport.com/drilling-fluid-test-on-field/marsh-funnel-and-graduated-cup/)

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Calibration

A very simple calibration was done by filling funnel to the bottom of the screen (1500ml) with water at

70ºF (plus or minus 0.5ºF) time of outflow of the quart (946ml) was 26seconds plus or minus ½ second.

This consists of a cone 6 inches (152 mm) across and 12 inches in height (305 mm) to the apex of which

is fixed a tube 50.8 mm long and 4.76 mm internal diameter. A 10-mesh screen is fixed near the top

across half the cone. And also there is a calibrated cup to take the fluid flowing from the orifice of the

funnel. The cup is calibrated to take 1-quart of the fluid (946ml).

2.6 Test Procedure

The apparatus was first calibrated with water. The funnel was filled up with water up to the

maximum level (1500ml) with the orifice blocked, at room temperature. Then this was released

and the time of outflow of the quart (946ml) was taken, this was 26 seconds.

A finger was used to cover the orifice while freshly collected mud sample was poured through the

screen into a clean, dry funnel until the fluid reached the bottom of the screen (1500ml).

The finger was immediately removed from the outlet and time the mud used to fill the receiving

vessel to the 1-quart (946ml) level is measured.

The result is reported to the nearest second as marsh funnel viscosity at the temperature of the

measurement in degrees Fahrenheit or centigrade.

2.7 Hydrogen Ion Concentration (pH) – Theory

The degree of acidity and alkalinity of drilling fluids can be measured by the concentration of the H + ion

or OH- concentration.

The pH of 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 in determining the solubility of organic thinners and dispersion of clays present

in the mud.

Mathematically, the pH of a solution the logarithm of the reciprocal of the H+ concentration in grams

moles per litre; this is:

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pH = log[1

H+¿¿ ] = -log[H+]

To get accurate measurements for pH, a pH paper or a pH meter is required.

The pH Paper:

The pH paper strips have dyes absorbed to display certain colours in certain pH ranges. It is an

inexpensive method of determining pH in fresh water or drilling muds. The main disadvantage is that

high concentration of salts (10, 000 ppm chloride) will alter the colour change and cause inaccuracy.

This indicator can be used to determine the acidity or basicity of a mixture.

Figure 3 - pH Paper(Source: Picture taken from Drilling Fluid Laboratory)

The pH Meter

This is a more accurate device than the pH paper. It is an electronic device utilizing glass

electrodes to measure a potential difference and indicate directly by dial reading the pH of the

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Figure 4 - pH Meter(Source: www.hg-hydroponics.co.uk retrieved April 4, 2014 from

http://www.hg-hydroponics.co.uk/hm-digital-ph-200-ph-meter-2558-p.asp)

sample.

2.8 Data Analysis and Results

Room Temperature - 23ºC

Mud Temperature - 27.5ºC

Table 1 - Table of Results for Density, Marsh Funnel and pH readings

Sample Balance Weight Marsh Funnel Viscosity 1500ml(seconds)

Marsh Funnel Viscosity 700ml (seconds)

pH (Hydrogen Ion Conc.)

Ppg Psi/1000 LB/ft3 Specific gravity

Phydrion pH Meter

1. Water 8.33 435 62.5 1.0 26 22 7.0 7.12. WBM 8.2 400 57.5 0.92 27 (350ml mud,

350ml H2O)7.0 9.5

2.9 Discussion of Results

The density, marsh funnel viscosity and pH of a normal drilling fluid is between 9 -10ppg, 32 - 36

seconds, 7 – 9.5 respectively. From results obtained, it can be deduced that the density of 8.2ppg, the mud

prepared does not seem to exhibit properties that a good drilling fluid should. But can only be confirmed

after subjected to further tests like the Mud Rheology and Filtration tests which would shed more light on

additional properties of the mud.

Sources of Error

Error due to improper calibration of mud balance.

An error resulting from not stirring the sediments of the mud very well after it has aged.

Unavailability of a pH meter to confirm the pH reading taken from the pH strips.

Impurities in water used for mixing mud.

Human errors while taking readings.

Questions

Using the mud weights (ppg) obtained, calculate:

1. The hydrostatic pressures that will be exerted on a formation at a depth of 10,000ft

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2. The mud weight needed to balance a formation pressure equivalent to 10,000ft. Depth with

0.561psi/ft. pressure gradient.

Solution

1. Wellbore Pressure: P=0.052 x MW xTVD

Where: P = Hydrostatic Pressure

MW = Mud Density or Mud Weight = 8.2ppg

TVD = True Vertical depth of point of interest = 10,000ft

Therefore:

P=0.052 x 8.2 x 10000

¿4264 psi

2. If a pressure gradient of 0.561psi per ft is given therefore calculating for pressure for 10000ft will

be:

Pressure=Pressure gradient x TrueVertical Depth

¿0.561 x10000

¿5610 psi

Therefore the mud weight required will be

MW = P0.052x Tvd

MW= 56100.052 x 10000

¿5610/520

¿10.79 ppg

2.10 Conclusion

This properties of a drilling fluid mentioned in this experiment should be regularly measured by a mud

engineer. The measurements will determine if the mud will fulfill its tasks and perform drilling operation

and also determine if the quality of the mud has deteriorated and requires treatment.

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EXPERIMENT 2

3.1 Objectives

The aim of this experiment is to learn how to operate and take reading with an Ofite Viscometer, in order

to:

Investigate the fluid character being Newtonian or Non-Newtonian

Viscosity determination as a function of Temperature

Gel Strength determination of the drilling mud

Introduction

Drilling operations cannot be successful without proper rheology. Rheological measurement of drilling

fluids (such as viscosity, gel strength, yield point) help determine how the fluid will flow under a variety

of conditions. It is an important aspect of drilling fluid properties required to accomplish certain desired

objectives in drilling operations.

3.2 Theory

Mud Rheology

Rheology refers to the deformation of all forms of matter. Rheologic measurement of drilling fluids such

as viscosity, gel strength and yield point helps determine how the fluid will flow under a variety of

conditions. It is imperative to perform certain required tests to confirm if a particular drilling fluid is in

proper condition to perform the functions mentioned above. These tests will be used to determine if the

quality of the mud is intact or requires treatment.

These tests include:

Viscosity

Gel Strength

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Fluid Loss

For laboratory experiments the Fann V-G meter, a direct indicating rotational multi-speed instrument, is

used. It allows measurement of: plastic viscosity, yield point, gel strength.

3.3 Determination of Mud Viscosity – Theory

Viscosity of a fluid as we know is the measure of the internal resistance of that fluid to flow. The desired

viscosity for a particular drilling operation is affected by several factors such as mud density, hole size,

pumping rate, pressure, etc

The indicated viscosity as obtained by any instrument is valid only for the rate of shear and will

differ to some degree when measured at different shear rate.

Fluid Characterization

Drilling fluids are characterized into:

Newtonian Fluids (True Fluids) where the ratio of the shear stress to shear rate or viscosity is

constant e.g water, lights

Non-Newtonian (Plastic Fluids) where the viscosity is not constant e.g Drilling muds, colloids

etc.

Figure 5 - Schematic of Fluids(Source: Akanji, 2014 Drilling Engineering Operation)

Calculations

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Determination of the viscosity of the mud and related formulas for solutions of readings from the

Fann Viscometer are as follows:

Plastic Viscosity(PV), cp = 600rpm reading – 300rpm reading

Yield Point(YP), ib/100ft2 = 300rpm reading – PV

Apparent Viscosity(AV), cp = 600rpm reading/2

3.4 Test Equipment

This is a cylindrical rotational viscometer, used to determine single or multi-point viscosities. The OFITE

800 Viscometer determines the flow characteristics of oils and drilling fluids in terms of shear rate and

shear stress over various times and temperature ranges at atmospheric pressure. The eight precisely

regulated test speeds, i.e. shear rates in RPM are: 3(Gel), 6, 3, 60, 100, 200, 300 and 600. A stir speed is

also provided.

Figure 6 - Ofite Model 800 Viscometer

3.5 Procedure

We mixed the mud sample on the “STIR” setting for 10seconds while cooling the fluid and

monitored the temperature steadily with a thermometer. Continued mixing until the sample

reached the target temperature

We then rotated the knob to a speed sting. When the dial reading stabilized, recorded the reading

and also took the temperature. Repeated this step for 600rpm, 300rpm, 200rpm, 100rpm, and

60rpm with varying temperature.

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3.6 Determination of Gel Strength – Theory

The gel strength of a drilling mud can be described as the strength of any internal structure formed in the

mud when it is static. An initial 10-sec. gel and a 10-min. gel strength readings gives an indication of the

amount of gel that will occur after circulation ceased and the mud remains static. The more the mud gels

during shutdown periods, the more the pump pressure that will be required to initiate circulation again.

Calculations

Determination of the gel strength of drilling mud is as follows:

Gel Strength, 10 second, ib/100 ft2 = The maximum dial deflection after 10sec

Gel Strength, 10 minute, ib/100 ft2 = The maximum dial deflection after 10min

3.7 Procedure

We mixed the sample on the “STIR” setting for 10seconds

Rotated the knob to “GEL” and immediately shut off the power

As soon as the sleeve stopped rotating, we waited 10seconds and turned the power back on while

looking at the dial and recorded the maximum dial deflection before the gel broke. That gave us

the 10sec. gel strength.

We re-stirred the fluid and waited 10minutes before recording the maximum dial deflection for

the 1m minute gel strength.

Estimation of Yield Point

Yield point indicates the ability of the drilling fluid to carry cuttings to the surface. It is as well the

measure of the electro-chemical or attractive forces in the mud under flow (dynamic) conditions. These

forces depend on the following

Surface properties of the mud solids

Volume concentrations of the solids

Electrical environment of the solids

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3.8 Data and Analysis of ResultsTable 2 - Table of Results for Viscometer Reading

ɸ600 ɸ300 ɸ200 ɸ100 ɸ60 ɸ30 ɸ6 µp µa YP(Ib/100ft2) Initial 10sec. Gel(Ib/100ft2)

Viscosity 300 265 250 232 220 215 165 35 150 230 110Temperature 28 27 27.5 28 28.4 28.6 29 25.5

Calculations

1. PlasticViscosity (PV ∨µ p) , cp=600 RPM reading – 300 RPM reading

¿300−265=35

2. Yield Point (YP) , lb /100 ft2=300 RPM – PV

¿265−35=230

3. Apparent Viscosity ( AV∨µa ) , cp=600 RPM READING2

¿ 3002

=150

0 100 200 300 400 500 600 7000

50

100

150

200

250

300

350

f(x) = 0.148056828452281 x + 215

Graph of Shear Stress vs Shear Rate

Shear Rate (RPM Settings)

Shea

r Str

ess (

Dia

l Defl

ectio

n)

Figure 7 - Graph of Shear Stress vs Rate showing class of fluid and yield point

Percentage Error

Pecentage Error= Analytical Solution−Graphical SolutionGraphical Solution

× 100

% Error=230−215215

×100=6.98 %

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3.9 Discussion of Results

A normal drilling fluid is Non-Newtonian and when compared with water or diesels which are Newtonian

fluids, it should have a shear stress versus shear rate graphical representation similar to the Bingham

model as shown in Fig 5 above. Non-Newtonian fluids have a yield point not equal to zero, denoted as the

intersection from the shear stress versus shear rate plot.

From the Experiment, the dial readings can be used to generate a plot of shear stress versus shear rate

given a yield point of 215 Ib/ft3 which can be compared with the yield point 230 Ib/ft3 as calculated

directly from the readings. This gives a percentage error of 6.98% which may be as a result of certain

factors as highlighted below and a slope of 0.1481.

The plastic viscosity PV of 35 shows the mud produced exhibits enough property to enable suspend any

solid or cutting during the drilling operation. Notwithstanding as shown in experiment 1, the density of

mud doesn’t meet the expectation of a good drilling fluid hence it must be weighted with the appropriate

additive.

Sources of Error

Sources of error for the Fann Viscometer readings may be as a result of:

Not making sure the dial was positioned at zero before experiment began.

Not taking the dial reading as soon as it stabilized for each rpm setting.

Error due to parallax.

Questions

1. How well does the assumption of a Newtonian fluid fit your results?

2. How well do your results fit published data for this drilling fluid sample?

3. What do you predict the viscosity to be at 290 deg. F?

4. What is the difference between Gel Strength and Yield Point of a drilling mud?

Solutions

1. From the graphical representation between Deflection Reading against Rpm Setting below we

could tell that intercept doesn’t cut at the origin as Newtonian fluids do. From the knowledge

of fluid viscosity profile using shear stress versus shear-rate relationship, the drilling mud

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prepared exhibits the characteristics of a Bingham plastic fluid. Therefore the drilling fluid

prepared is Non-Newtonian as shown by figure 5 and figure 7 above.

2. Results from my prepared water-based mud could not be matched with any reachable published

data. This I believe is as a result of the unique preparation of this water based mud which is done

to meet pressure demands of various formation types.

3. The viscosity at 290ºF can be predicted from a graphical representation of Plastic Viscosity vs

Temperature in Fahrenheit. Converting all temperatures from Celsius to Fahrenheit using the

formula 9/5C + 32 = ºF. From a plot of plastic viscosity versus temperature, and extrapolation can

be made for 290oF, but time was insufficient to take several shear stress readings for series of

temperature.

From previous studies and works done by fluid mechanics engineer, it is understood that

temperature and viscosity have an inverse relationship. An increase in temperature would give a

reduction in the viscosity of a substance. Therefore at high temperatures such as 290oFthere will

be a drastic reduction in the viscosity of fluid. Notwithstanding, this relationship may be non-

linear and is dependent the characteristics of the fluid.

Hence if linearity is assumed, an equation can be deduced to estimate the viscosity of fluid. This

can be given by:

T1

T2=

μ2

μ1

Where T1 = Reference Temperature = 28oC = 82.4oF

T2 = Estimate Temperature = 290oF

μ1 = Apparent viscosity at temperature T1 = 150cp

μ2 = Apparent Viscosity at Temperature T2

Hence:

82.4290

= x150

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x=82.4 ×150290

=42.6 cp

Below are graphs showing the relationship between viscosity and temperature for some

substances.

Figure 8 - Viscosity vs Temperature Relationship for Naphthalene

Figure 9 - Viscosity-Temperature Relationship for Water

4. Difference between Gel Strength and Yield Point of a Drilling Mud

Table 3 - Difference between Gel Strength and Yield Point

Gel Strength Yield Point

1. Gel Strength of a mud is the shear stress

of drilling mud that is measured at low

shear rate after the drilling mud is static for

Yield Point of a mud is the yield stress

extrapolated to a shear rate of Zero

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a certain period of time

2. Gel strength demonstrates the ability of

the drilling mud to suspend drill solid and

weighting material when circulation is

ceased

Yield point is the period at which the

drilling fluid is too weak to carry cuttings to

surface

3. Gel Strength can be increased by over

treatment with organic gelling material in

oil based mud

Low temperature in oil based mud system

will increase the yield point.

Conclusion

In conclusion fluid tests on drilling fluids are inevitable and must be carried out by the drilling engineer to

access fluid qualities for successful drilling operations.

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References

1. Akanji, L. (2014). Drilling Fluid Properties. Salford: University of Salford.

2. Akanji, L. (2014). Laboratory Manual on Drilling Fluid Properties. Salford: Petroleum and Gas

Engineering, School of Computing, Science and Engineering.

3. Bourgoyne, A. (1986). Drilling Fluid. In A. Bourgoyne, M. Chinevert, K. Millheim, & Young,

Applied Drilling Engineering (pp. 42-62). Texas: Society of Petroleum Engineers, Richardson

TX.

4. Concept of Viscosity. (n.d.). Retrieved April 3, 2014, from www.columbria.edu.

5. Oil Field Glossary. (n.d.). (Slumberger) Retrieved April 4, 2014, from www.slb.com:

http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=yield

%20point

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