1.1.1      
Additives for Synthetic Based Drilling Fluids

As being observed by Boyd P. A. et al.
(1985), it is remarkable for a drilling fluid to be complex in order to carry
out its numerous basic functions. Each additive has specific characterization
and function to perform which each of it may exhibit different behavior when interact
with the drilling fluids. Table 2.5 shows several of additives that have been
studied based on their function.  Before
going deeper into the specific additives, one must first know the common
additives for drilling fluid; in this case; synthetic-based drilling fluids
(Fatimah, H. et al. 2016).

 

Table 2.5

Common Additives for
Synthetic-Based Mud

Types of
Additives

Example Products

Functions

Emulsifiers

Confi-Mul P
Confi-Mul S

Act as primary and secondary emulsifier

Lime

Lime

Activate emulsion and control pH of
drilling fluid

Viscosity control

Confi Gel HT

Act as viscosifier

Filtration Control

Confi Trol HT

HPHT Filtration Control

Density Control

Calcium Chloride

Soluble weighting agent and Ca2+
inhibition

Water Content

Water

Internal phase

Control of solids

Barite

Weighting agent

Source:
Fatimah, H. A., Noraini, S. (2016). Evaluation of Nanoparticles in Enhancing
Drilling Fluid Properties. International
Journal of Scientific & Engineering Research, 7(10), 1489-1497.

 

 

1.2           
Lost
Circulation Materials

 

1.2.1      
Types of Lost Circulation

Lost circulation material (LCM) is a
newly-formulated solid additive added into the drilling fluid in order to
mitigate the lost circulation problem (Schlumberger Oilfield Glossary). One of
the critical drilling problem is lost circulation where drilling fluids usually
lost into either natural or induced formation fractures (Nayberg, T. M., 1987).
The losses may be varied for each drilling condition and these problems may be
worsen if the drilling operators does not take initiative to prevent it which
also led to loss of expensive drilling fluids and loss of well control as being
discovered by Nayberg T. M. (1987). Therefore, application of an immediate
solution to mitigate the lost circulation problem have been conducted by numerous
researchers. Their findings regarding lost circulation material is summarized
in Table 2.6. There are three types of lost circulation material which will
briefly discussed; fibrous, flaky and granular materials.

 

Table 2.6

Previous researches of lost
circulation material

Types of LCM

Examples

Major Findings

Reference(s)

Fibrous

Durian Rind

The
results demonstrate that durian rind has the potential to act as LCM and
performed in sealing the simulated fractures.

Issham, I. et al. (2015)

Peanut hulls, bagasse and sawdust

This
paper proves that the fibrous material =, in this case, peanut hulls
(containing crude fibre 60%) shows magnificent performance in reducing loss
circulation of drilling fluids as compared to the bagasse and sawdust. In
fact, sawdust is the worse types of LCM due to the high content of cellulose
which makes it more friable under high pressure.

Ahmad M. A. et al. (2015)

 

 

Table 2.6 (Continued)

Types of LCM

Examples

Major Findings

Reference(s)

Granular

Based
from these studies, granular material exhibits extraordinary characteristic
to be as one of LCM. However, it can only be applicable as maximum size of
the fracture have been determined. In fact, certain physical properties must
first determine before designing the optimum fracture sealing
characteristics.

Scott, P. P. et al. (1955) and Rogers,
W. F. (1953)

 

Limestones

Limestone
has been used in this experiment based on the common material used in well
that have moderate losses; in this case, 120 bbl/hr. However, regarding the
lost circulation test, the granular limestone did not achieve as an
outstanding LCM with the aid of polymers. In fact, from the suspension test,
this type of LCM is not able to seal even small fracture of 2mm.

Calcada, L. A. et al. (2015)

Flakes

Oyster Sea Shells (OSS)

Fine
size of OSS has performed excellently in controlling lost circulation for WBM
when compared to other conventional LCM, in this case, ground walnut shells
and a blend of fibres, flakes and granules at same drilling fluid condition.

Oluwatoni, A. A., et al. (2014)

 

Limestone

Differ
from granular limestone results, laminar limestone in the form of flakes
exhibit a good performance in mitigating lost circulation. From the test
conducted in this research, there was no record of fluid loss in the fracture
when dealing with this type of LCM.

Calcada, L. A. et al. (2015)

 

1.2.2      
Citrus Sinensis

Sharifi-Rad J. et al. (2017) introduced
Citrus as one of the largest genes of Rutaceae family, including almost 70
species whose peel’s essential oil have a very complex composition., which
currently under study for its excellent broad spectrum physiological and
pharmacological properties. In fact, Citrus fruit is the most favorable fruit crop
in international crop (Defraeye T. et al., (2015); Gordon A. et al. (2015)).
There are basically four types of commercial Citrus species, among which Citrus
Sinensis (L.) Osbeck that currently being used throughout this study. Table 2.7
has summarized the early studies that using Citrus Sinensis as one of their
material.

Ho and Lin (2008) and
Khan et al. (2010) also signified that peels are the largest share of residue
of Citrus processing industries, of which major portion is wasted worldwide,
including Malaysia. The primary waste of Citrus peel is a good source of
molasses, pectin as been introduced by Chou and Uang (2003), which usually
dried and mixed with dried pulps and it can be sold as one of cattle feed
products (Bocco, A. et al., 1998).

In order to enhance the
functionality of a fibrous material, one method used for instances, in food
processing byproducts, is to expand their internal surface area which increase
its apparent viscosity as been investigated by Turbak, A. F. et al. (1983) and
Ruan, R. et al. (1996). However, there is no significance study of Citrus
Sinensis as Lost Circulation Material.

 

Table 2.7

Early studies regarding Citrus
Sinensis

Author(s)

Scope

Findings

Chatzimitakos,
T. et al. (2017)

Utilization
of Citrus Sinensis and Citrus limon peels in one-step synthetic procedures
via carbonization

Both
of these fruits peels have the advantages to serve as precursors for green
production of two kinds oh highly fluorescent carbon quantum dots via an
uncomplicated, easy and low-cost method.

Lundberg,
B. et al. (2014)

To
study the composition and rheology of citrus fibers

The
physical size of the citrus fibers has a significant impact on apparent
viscosity as well as their flow behavior. This studies also demonstrates that
the shape of rheology curved depending on the particle size which result in
linear rheograms as the fiber length decreased.

Samira,
L. and Khodir, M. (2013)

To
determine and to compare the content of phenolic compounds and the
antioxidant capacity of peels and leaves from seven selected orange varieties

This
research has found that they exhibit excellent efficiency as potent
antioxidants and the by-products of orange proves to have higher content of
phenolics.

 

Citrus Sinensis L. has a low Ph level,
approximately 3 to 4 and is characterized which compromised by 95% of total
solids and high-water content (approximately 80 to 90%) (Satari and Karimi,
2018). Table 2.8 summarized the composition of major citrus fruits’ byproducts
produced in citrus processing industries. This table also includes come fats,
organic acids, free sugars, carbohydrate polymers and pigments (Boukroufa et
al., 2015). In citruses, citric acid is the dominant organic acid which usually
have pH value approximately to 2.2 (Karadeniz, F., 2004). Due to this presence
of acid, drilling operator must deal with this by designing adequate of pH
control additives.

 

Table 2.8

Composition of some major citrus
fruits’ by-products (% of dry basis)

Waste

Ash

Sugar

Fat

Protein

Pectin

Lignin

Cellulose

Hemicellulose

Lemon
Peelsa

2.52

6.52

1.51

7.00

13.00

7.56

23.06

8.09

Sweet orange peelsb

2.56

9.57

4.00

9.06

23.02

7.52

37.08

11.04

Grapefruit peelsc

3.73

22.9

3.78

6.07

25.00

2.19

22.00

11.09

Citrus Wasted

4.75

33.09

15.30

1.95

8.82

7.96

Kinnow Mandarine

3.23

31.58

5.78

22.6

0.56

10.10

4.28

a,b Marin et al. (2007)

c Purbafrani et al. (2010)

d Satari et al. (2017)

e Oberoi et al. (2011)