Microsoft Word - 36-2538_s


Engineering, Technology & Applied Science Research Vol. 9, No. 1, 2019, 3859-3862 3859 
 

www.etasr.com Iqbal et al.: An Experimental Study on the Performance of Calcium Carbonate Extracted from … 

 

An Experimental Study on the Performance of 

Calcium Carbonate Extracted from Eggshells as 

Weighting Agent in Drilling Fluid 
 

Raheel Iqbal 

Institute of Petroleum & Natural Gas 

Engineering, Mehran University of 

Engineering & Technology, 

Jamshoro, Pakistan 

15PG46@students.muet.edu.pk 

Muhammad Zubair 

Institute of Petroleum & Natural Gas 

Engineering, Mehran University of 

Engineering & Technology, 

Jamshoro, Pakistan 

13pet04@students.muet.edu.pk 

Fawad Pirzada 

Institute of Petroleum & Natural Gas 

Engineering, Mehran University of 

Engineering & Technology,  

Jamshoro, Pakistan 

fawadpirzada8@gmail.com 

Faisal Abro 

Institute of Petroleum & Natural Gas 

Engineering, Mehran University of 

Engineering & Technology, 

Jamshoro, Pakistan 

faisal.abro@hotmail.com 

Muhammad Ali 

Institute of Petroleum & Natural Gas 

Engineering, Mehran University of 

Engineering & Technology, 

Jamshoro, Pakistan 

muhamadali5014@gmail.com 

Avinash Valasai 

Department of Mining Engineering, 

Mehran University Of Engineering & 

Technology, 

Jamshoro, Pakistan 

amvalasai@gmail.com 
 

 

Abstract—Drilling mud density is an important factor in drilling 

operations. The cost of the drilling mud used for oil and gas well 

drilling can be 10%-15% of the total drilling cost, and the deeper 

the well, the more the needed drilling mud. This research aims to 

prepare a mud that provides performance similar to the 

conventional mud and to lower down the dependency of 

primordial CaCO3 technology by exploring it from trash/polluted 

and naturally occurring materials. For that purpose, a mud was 

prepared by replacing primordial CaCO3 with CaCO3 derived 

from eggshells, as eggshells contain CaCO3 in high amounts 

ranging from 70% to 95%. The success of this project will 

provide an affordable solution and an alternative way to explore 

new methodologies of obtaining CaCO3. The obtained results of 

this research are quite satisfactory. CaCO3 obtained from 

eggshells is used in high amounts, 275–410g to achieve density 

ranges from 9.5 to 11.0 pounds per gallon whereas, the needed 

quantity of pure CaCO3 is 150g to obtain density of 10.5 pounds 

per gallon. Apart from this, it is also observed that eggshell based 

CaCO3 samples are more efficient in rheological properties 

compared to the market samples of CaCO3. The pH of pure 

CaCO3 sample of 10.5 pounds per gallon density is almost the 

same with the sample of eggshell CaCO3 of 10.5 pounds per 

gallon density. 

Keywords-drilling fluid; weighting agent; mud balance; 

calcium carbonate; rheological properties 

I. INTRODUCTION 

Drilling fluid has obligatory properties like carrying out 
rock cutting towards the surface, cleaning and cooling the pit, 
decreasing resistive forces, stabilizing wellbore, and preventing 
fluids to flow from pores into the borehole. Various methods 

for designing suitable drilling muds are developed for avoiding 
problems encountered during drilling. The drilling mud should 
be user friendly, cost effective and economically viable. 
Therefore drilling muds are basically formulated to decrease 
the effect of damage and to ensure the possibility and 
economically viability of rotary drilling in hydrocarbon 
containing formations. The filter cakes which are formed after 
the intrusion of drilling mud in the pore space of pay zone are 
compressible and contain varying porosity and permeability 
characteristics, with low void spaces at the filter channel 
surface and maximum void spaces on cake surface. In order to 
reduce filtrate invasion, fluid loss additives such as organic 
polymers which prohibit water invasion are used. During the 
formulation of the mud, the microscopic structure and 
composition of the filter cake related to it and the information 
of the characteristics of filtration are of main importance [1]. 
During drilling and completion varying drilling muds in the 
borehole are used. The most significant factor is the physical 
and chemical compatibility of the mud with the reservoir rock. 
By formation damage these muds can reduce the productivity 
of the well by invasion. Consequently additives are used i.e. 
CaCO3,which can reduce the chance of these damages in the 
formations by forming a filter cake of low permeability 
(optimum thickness) that reduces further invasion of solids and 
filtrate the pore spaces of rock. After drilling these cakes are 
washed by for maximizing the flow in the wellbore. Fluid loss 
and viscosity of mud are important factors which must be 
investigated throughout the drilling of a well [2]. For that 
reason, mud is treated with several types of additives i.e. 
different polymers and chemicals, to achieve requirements 
important for the particular well such as rheology, control of 

Corresponding author: R. Iqbal



Engineering, Technology & Applied Science Research Vol. 9, No. 1, 2019, 3859-3862 3860 
 

www.etasr.com Iqbal et al.: An Experimental Study on the Performance of Calcium Carbonate Extracted from … 

 

fluid loss, weight of mud etc. Starch and calcite are the most 
important materials used to control fluid loss and to increase 
the weight of mud by forming mud cake respectively [3]. 

II. EXPERIMENTAL WORK 

A. CaCO3 Analysis in Eggshells by Titration Technique 

Calcite is a major component of eggshells ranging from 
70% to 95%. The technique of titration named as back titration 
is used for the reaction of acids with calcium present in the 
blended powder of eggshells. Calcium dissolves in acids rather 
than pure water: 

CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) 

This reaction is slow mostly when it reaches completion 
hence this technique cannot be directly used. Sufficient amount 
of acid must be added to dissolve all the calcium carbonate. 
Then, sodium hydroxide will be added that will react with the 
remaining HCl. The unreacted amount is calculated by 
determining the difference between the amount of HCl that was 
added initially and the amount of HCl that remained after the 
titration. The CaCO3 amount present in the sample is calculated 
as discussed. Given equation is used to determine the amount 
of CaCO3 in the sample: 

NaOH(aq) + HCl(aq) → H2O(l) + NaCl(aq) 

B. Drilling Fluid Preparation and Properties 

A few additives along with Barite BaSO4, Calcite CaCO3 
are commonly used in water-based drilling mud. The three 
main factors which affect drilling fluid performance are 
density, viscosity and pH. Fluid samples preparation at 
laboratory scale is obtained by adding chemicals taken in 
grams into 350ml barrels (standard laboratory barrel). This 
research involves the preparation of five water-based drilling 
fluid samples which contain bentonite as a filtration controller 
and viscosifier, caustic soda for pH control, and starch for 
filtration control. Along with them, soda ash and Xanthan gum 
are also used as hardness and rheology control materials 
respectively. The composition of all these additives is constant 
for all prepared samples except Calcite. The most important 
part of these samples is the concentration of CaCO3 as a 
weighting agent. It is used to increase densities of samples 
from 9.0 to 11 pounds per gallon (ppg). The required amount of 
CaCO3 as a weighting agent is determined by: 

945 2 1
Weighting Agent Sacks/100 Barrels)

22 5 2
(

( )

.

W W

W

−
=

−
 (1) 

And the formula to determine the required amount of Barite 
as a weighting agent can be written as: 

( )
2

Weighting Agent Sacks/100 Ba
1470 2 1

5
rrels

3

( )W W

W

−
=

−
  (2) 

where, W1 is indicating the initial weight of mud (ppg) and W2 
is indicating the required weight of mud (ppg). 

C. Density of Mud 

Mud density is the main parameter to consider during study 
as it directly affects the formation of filter cake. The most 
common additive to increase the mud weight in production 

zones is mostly calcite (CaCO3) which is widely used during 
drilling of zone of interest. Five drilling mud samples by 
formulating both calcites (pure calcium carbonate, eggshell 
calcium carbonate) are prepared in this study to achieve 
densities ranging from 9.5 to 11.0 ppg. The amount used for 
the formulation of pure calcite base sample is 150g as shown in 
Table I, and the amount for the formulation of eggshells based 
samples ranges from 275g to 410g as shown in Figure 1 to 
achieve mud density from 9.5 to 11.0 ppg. 

 
Fig. 1.  Amount of calcium carbonate vs densities 

D. Drilling fluid rheological properties 

Rheological properties are categorized in gel strength, yield 
point and apparent viscosity. Rheology is the basis of all 
investigations ranging from hydraulics of wellbore to the 
evaluation of mud system functionality. Mud rheological 
properties are continuously tested throughout the drilling 
operation. Mud rheological properties are very critical to 
maintain control while tackling the wellbore problems, because 
inappropriate rheological properties may result in loss of time 
and money. Besides rheological properties, filtration, pH, 
chemical analysis (alkalinity and lime content, chloride 
content, calcium content, etc.), and resistivity are also tested 
throughout the drilling. In the laboratory (as in the drilling site), 
a rotational viscometer is frequently used to measure the 
rheological properties of mud. Readings are taken on 600, 300, 
200, 100, 60, 30 and 6rpm (rotations per minute). Later these 
readings are plotted on a chart of shear stress and shear rate 
which are used to determine viscosity and appropriate viscosity 
model. Rotational viscometer also provides the information 
about other rheological properties, including effective 
viscosities (µa, µp, and µe), gel strength (Gel) and yield point 
(Yp) as shown in Table II. 

Given equations are utilized for these purposes: 

Apparent Viscosity µa, (cp) =
∅���

�
  (3) 

Plastic Viscosity µp, (cp)= ∅600 � ∅300  (4) 

Effective Viscosity µe,(cp) = 

��	�∅

�
  (5) 

Yield Point Yp, (lb/100ft
2
)=∅300 � µ�  (6) 

Shear Stress τ, (lb/100ft
2
) = 1.065 * Ø  (7) 

Shear Rate ɣ, sec
-1
= 1.7023 * ω   (8) 



Engineering, Technology & Applied Science Research Vol. 9, No. 1, 2019, 3859-3862 3861 
 

www.etasr.com Iqbal et al.: An Experimental Study on the Performance of Calcium Carbonate Extracted from … 

 

where, Ø indicates the reading of dial, lb/100ft
2
 and ω indicates 

rotation of rotor speed (rpm). Bingham plastic model is a basic 
two-parameter model used in drilling industry widely to 
identify the properties related to flow for the different mud 
types. It is known as the most common fluid model to estimate 
non-Newtonian fluids’ rheology. Shear stress is a straight line 
function of shear rate which is the basic supposition of this 
model. Yield point is also named as threshold stress, it is the 
point where shear rate is zero. By the reduction in colloidal 
solids, the optimum plastic viscosity (PV) is achieved. 

TABLE I.  DRILLING MUD SAMPLES AND ITS COMPOSITION 

Product Per lab barrel (350 ml) 

Sample number 1 2 3 4 5 

Water (ml) 325.50 325.50 325.50 325.50 325.50 

Bentonite (g) 24.50 24.50 24.50 24.50 24.50 

Barite - - - - - 

Pure CaCO3 (g) 150 - - - - 

Eggshell CaCO3 (g) - 275 320 365 410 

Starch (g) 0.40 0.40 0.40 0.40 0.40 

Caustic soda (g) 0.20 0.20 0.20 0.20 0.20 

Soda ash (g) 0.25 0.25 0.25 0.25 0.25 

Xanthanum (g) 1.00 1.00 1.00 1.00 1.00 

TABLE II.  RHEOLOGICAL PROPERTIES OF MUD SAMPLES 

Sample number 1 2 3 4 5 

Plastic Viscosity (cp) 22 10.5 17.1 23 32 

Apparent Viscosity (cp) 38 20.5 33 39.25 50 

Yield Point (lb/100 ft
2
) 32 20 31.8 32.5 36 

Gel Strength@10 min 

(lb/100 ft
2
) 

16.5 12.8 19.5 20 20.6 

θ600 76 41 66 78.5 100 

θ300 54 30.5 48.9 55.5 68 

θ200 45 26.5 42 46 56 

θ100 35 21.5 33 35.5 42 

θ60 29 19 29 31 36 

θ30 19.5 17 25 26 29 

θ6 15 13 19 19.5 21 

 
To carry cuttings out of the hole, yield point should be high 

enough, but not very much because pump pressure would 
become incompatible with drilling operation. For both low and 
high shear rates ranges, Bingham plastic model has its own 
limitations. The physical/solid reason behind this behavior is 
that the liquid generally contains particles (clay) or large 
molecules (polymers) which generally have some kind of 
interaction, while creating a weak solid structure, known as a 
false body, and at that point a certain amount of stress is 
required to break it. Under viscous forces the particles tend to 
move as the structure breaks. The results which are acceptable 
for a drilling mud diagnosis are produced by Bingham plastic 
model. But, for hydraulic calculations its accuracy is not very 
high. A Bingham body doesn’t begin to flow until a shearing 
stress, corresponding to the yield value, is exceeded. The 
results for the Bingham plastic model are obtained by the graph 
between shear stress and shear rate in Figure 2, plotted with the 
use of (6) and (7). 

E. Drilling Fluid pH Determination 

It is important to know mud pH because it affects the 
solubility of the organic thinners, contaminant removal, 
corrosion mitigation, and the dispersion of clays present in the 

mud. pH is mostly used to express drilling fluid’s, especially 
water-based mud, acidity or alkalinity. Generally, its value 
ranges from 0 to 14. pH is expressed by (9): 

pH=-log[H]     (9) 

where, [H] is the hydrogen ion concentration in mol. pH value 
decreases as the acidity of the fluid increases by the addition of 
more hydrogen atoms. Generally, pH of the neutral fluid is 7. 
Values above 7 indicate alkaline pH below 7 indicate acidic 
pH. 

In drilling mud there are three main chemical components 
involved which are hydroxyl ions (OH

-
), carbonate ions (CO3

-2
) 

and alkalinity of drilling mud including (HCO3
-
) bicarbonates 

ions. For better pH measurement, pH meter is mostly used 
rather than the litmus paper, because pH meter provides 
quantitative information where litmus paper provides 
qualitative information about the acidity of the drilling mud. 

 

 

Fig. 2.  Bingham plastic model of samples 

III. RESULTS AND DISCUSSION 

A. CaCO3 Determination by Back Titration 

The outcomes from the back titration method for the CaCO3 
amount can be determined by washing, boiling, peeling off the 
membranes, and heating of the eggshells at 120°C, and the 
resulting value is showing 74% presence of CaCO3 in the 
eggshells blended powder. 

B. Characteristics of Drilling Fluids 

The densities of 5drilling fluid samples of both ordinary 
CaCO3 and eggshell CaCO3, ranging from 9.0 to 11.0 ppg are 
shown in Figure 1. Table II provides comprehensive 
information about the rheological properties of the prepared 
sample. Variations in rheological properties were observed 
with the increase of amount of CaCO3 of eggshells. Besides 
this, the purpose of increased density was achieved by 
increasing the amount of CaCO3 obtained from eggshells. In 
general, the increment in sample density causes increment in 
rheological properties’ values. Meanwhile, the drilling fluid 
sample No. 4 (based on 10.5 ppg eggshell CaCO3) exhibits 



Engineering, Technology & Applied Science Research Vol. 9, No. 1, 2019, 3859-3862 3862 
 

www.etasr.com Iqbal et al.: An Experimental Study on the Performance of Calcium Carbonate Extracted from … 

 

similar rheological property values with sample No. 1 (based 
on 10.5 ppg pure CaCO3). 

C. Bingham Plastic Model 

It is discussed that non-Newtonian fluids exhibit a 
relationship between shear rate and shear stress measured for 
the formulated samples as shown in Figure 2. According to the 
graphs which are plotted for 5 water-based drilling fluid 
samples, shear stress increases with increasing amount of 
eggshell CaCO3, while pure CaCO3 sample No. 1 is showing 
almost the same trend with the sample No. 4 of eggshell 
CaCO3. A general trend line is drawn for the Bingham plastic 
fluid and it is observed that the yield point of 36Ib/100ft

2
 is 

obtained for eggshell CaCO3 sample No. 5, and it is also 
measured by viscometer and discussed in Table II.  

D. pH Determination 

The pH of the prepared sample is determined by using pH 
meter and the obtained results are shown in Figure 3. If a 
comparison is generated between the Calcite based samples of 
same densities then it is observed that the sample No. 1 of pure 
CaCO3 has almost the same pH value with the sample No. 4 of 
eggshell CaCO3 with 10.5 ppg density, which indicates that 
there is no impact of the amount of CaCO3 on the pH of both 
samples. The required amounts for both samples are varying 
but as density reached 10.5 ppg for both samples, they show 
almost the same pH. 

 

 

Fig. 3.  pH of samples 

IV. CONCLUSION 

On the basis of laboratory measurements analysis and 
interpretation, the main concluded points are: 

• Mud density of 10.5lb/gal is optimum for the X well. It was 
selected among 5 prepared mud densities, considering that 
it can sustain formation pressure. By using another mud 
density the formation starts to create fractures in the well. 

• CaCO3 obtained from eggshells is used in higher amounts 
from 275g to 410g to achieve densities ranging from 9.5 to 
11.0lb/gal. Pure CaCO3 took only 150g to obtain density of 
10.5lb/gal. Apart from this, it is also observed that eggshell 
CaCO3 samples are more efficient in rheological properties 
than the samples from market CaCO3. 

• It is observed that the pH of pure CaCO3 sample of 
10.5lb/gal has almost the same value with the sample of 
eggshell CaCO3 of 10.5lb/gal density.  

• It was observed that the prepared samples of eggshells 
CaCO3 are producing unpleasant smell after 1-2 days of 
preparation.  

• However, by heating the eggshells at a temperature ranging 
from 300°C to 500°C, better results for the amount of 
CaCO3 will be obtained. By doing this the efficiency of the 
CaCO3 is improved as the acids which are present in the 
shells are removed and the smell dissipates. 

REFERENCES 

[1] K. A. Fattah, A. Lashin, “Investigation of mud density and weighting 
materials effect on drilling fluid filter cake properties and formation 
damage”, Journal of African Earth Sciences, Vol. 117, pp. 345-357, 
2016 

[2] S. Gogoi, P. Talukdar, “Use of Calcium Carbonate as bridging and 
weighting agent in the non damaging drilling fluid for some oilfields of 
Upper Assam Basin”, International Journal of Current Research, Vol. 7, 
No. 8, pp. 18964-18981, 2015 

[3] T. Hudson, M. Coffey, “Fluid loss control through the use of a liquid 
thickened completion and work over brine”, Journal of Petroleum 
Technology, Vol. 35, No. 10, pp. 1776-1782, 1983 

[4] M. Sajjadian, E. E. Motlagh, A. A. Daya, “Laboratory Investigation to 
Use Lost Circulation Material in Water Base Drilling Fluid as Lost 
Circulation Pills”, International Journal of Mining Science, Vol. 2, No. 
1, pp. 33-38, 2016 

[5] N. Gaurina-Medimurec, “Laboratory Evaluation of Calcium Carbonate 
particle size selection for drill-in fluids”, Rudarsko-Gcolofko-
Naftnizbomik, Vol. 14, pp. 47- 53, 2002 

[6] A. Odabasi, An Experimental Study of Particle Size and Concentration 
Effects of Calcium Carbonate on Rheological and Filtration Properties 
of Drill-in fluids, MSc Thesis, Middle East Technical University, 2015 

[7] R. Samavati, N. Abdullah, T. K. Nowtarki, S. A. Hussain, D. R. A. Biak, 
“Rheological and Fluid Loss Properties of Water Based Drilling Mud 
Containing HCl-Modified Fufu as a Fluid Loss Control Agent”, 
International Journal of Chemical Engineering and Applications, Vol. 5, 
No. 6, pp. 446-450, 2014 

[8] M. Amani, J. K. Hassiba, “The Effect of Salinity on the Rheological 
Properties of Water Based Mud under High Pressures and High 
Temperatures for Drilling Offshore and Deep Wells”, SPE Kuwait 
International Petroleum Conference and Exhibition, Kuwait City, 
Kuwait, 10-12 December, 2012 

[9] P. K. Jha, V. Mahto, V. K. Saxena, “Emulsion Based Drilling Fluids: An 
Overview”, International Journal of Chem Tech Research, Vol. 6, No. 4, 
pp. 2306-2315, 2014 

[10] P. Talalay, Z. Hu, H. Xu, D. Yu, L. Han, J. Han, L. Wang, 
“Environmental considerations of low-temperature drilling fluids”, 
Annals of Glaciology, Vol. 55, No. 65, pp. 31-40, 2014 

[11] P. O. Ogbeide, S. A. Igbinere, “The Effect of Additives on Rheological 
Properties of Drilling Fluid in Highly Deviated Wells”, Futo Journal 
Series, Vol. 2, No. 2, pp. 68–82, 2016 

[12] N. Al-Malki, P. Pourafshary, H. Al-Hadrami, J. Abdo, “Controlling 
bentonite-based drilling mud properties using sepiolite nanoparticles”, 
Petroleum Exploration and Development, Vol. 3, No. 4, pp. 717-723, 
2016 

[13] C. Kelessidis, “Drilling fluid challenges for oil-well deep drilling”,  
nternational Multidisciplinary Scientific GeoConference SGEM 2009, 
Albena, Bulgaria, June 14-19, 2009