1.1 a petroleum exploration and development phase are depending

1.1           
Introduction

The most widely procedure that were conducted
in extracting the hydrocarbon is by applying rotation method which require a
weight over drillstring. This method will affect the original geological
formation until the reservoir is reached. However, in certain cases, the most
prevalent problem that occurs in drilling operation is lost circulation.

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As far as this proposal
has been discussed, lost circulation is crucial drilling problems especially
when in highly fractured formation, cavernous formation and not to mention,
highly permeable depleted reservoirs also tend to have high possibilities in
lost circulation during drilling.  In
fact, during cementing operation, lost circulation could also happen in cement
slurries which fractures in the wellbore are widened by drilling fluid
pressure.

The complications that
occurred during the drilling operation can be very costly. Even with the best
drilling practices, lost circulation still able to occur. Lost circulation not
only change the permeability and wettability of rocks but also affect
management and production time including cost. The oil and gas industry reflect
and serves an extraordinary revolution in both materials science and in
engineering practices.

Well, to put it in a
nutshell, the main point will be discussing in this chapter specifically owing
to the study of Citrus Sinensis as lost circulation material in synthetic based
mud.

 

1.2           
Drilling
Fluids

1.2.1      
Function of Drilling Fluids

Exploration of oil and gas field might to
be difficult to achieved without the drilling fluids. Table 1 summarized the basic
function of drilling fluid in oil and gas industry. Drilling fluid is key
performance drilling operation where without proper planning, catastrophic
event might have occurred.  In fact, the
successful completion of a petroleum exploration and development phase are
depending on the properties of drilling fluid (Williamson, D. et al., 2013).

 

Table 2.1

Basic Function of Drilling fluids

Function

Descriptions

Controlling
formation pressure

The
specialized formulated drilling fluid that pumped into the wellbore will help
to control the formation pressure by using specific additives

Removing
cutting from borehole

The
drilling fluid the circulates will brings up the cutting while promoting good
hole cleaning. Sayindla S. et al (2017) studies that insufficient hole
cleaning may can cause in reducing rate of penetration (ROP) formation
fracturing and stuck pipe.

Cooling
and lubricating the bit

The
drilling fluid will help to cool down the drilling bit. This is due to the
excessive friction force applied on the drilling bit will tend to further
wear the bit.

Source:
Williamson, D. (2013). Drilling Fluid Basics. Oilfield Review Spring, 25(1).
Retrieved on October 20, 2017 from www.slb.com/resources/oilfield_review/~/media/Files/…/defining_fluids.ashx

 

1.2.2      
Types of Drilling Fluid

There are two different system in drilling
fluid, which are continuous phase (consist of liquid) and discontinuous phase
(consist of solids). The continuous phase can be further divided into two
different categories; aqueous and non-aqueous drilling fluids. Figure 2.1 shows
the types of drilling fluid that have been used recently in the industry.

Drilling fluids are
commonly used in transporting the cuttings to the surface and it is crucial for
the drilling operator to be able to decide an appropriate fluid for each
drilling condition, including the decision of using a specific types of
drilling fluids. Each of these types have its own advantages and disadvantages,
as being studied by Apaleke et al. (2012). Currently, the drilling fluids have
become more complex in term of formulation and expensive due to the diverse
requirement that need to be fulfil so that the drilling fluid may cater all its
basic functions (Sayindla, S. et al., 2017).

Many researches have been
working with these types of drilling fluids; water-based mud, oil-based mud and
synthetic-based mud, but conclusions differ. Table 2.2 lists the previous
studies that have been conducted in determine the behavior of drilling fluid.
There are no standard requirements available which recommend the types of
drilling fluid to be used for a particular drilling condition or a particular
well.

 

Figure
2.1 Types of Drilling Fluid

Source:
Jack (2015). Types of Drilling Fluid. Retrieved on October 11th,
2017 from http://www.oilngasdrilling.com/wp-content/uploads/2015/04/types-of-drilling-fluids.jpg

 

 

 

Table 2.2

Previous studies of drilling
fluids

Types of
Drilling Fluid

Authors

Conclusions

Oil-Based
Mud (OBM)

Sayindla,
S. et al. (2017)

This
paper also states that the same rheological properties OBM to WBM is much
better that WBM when it comes to its basic function of hole cleaning. Field
studies demonstrates that by using OBM might improving the rate of
penetration (ROP), however, laboratory studies indicate that it is not
obvious that ROP improves with OBM.

Oil-Based
Mud (OBM)

Sasen
and Loklingholm (2002)

In
his study, it is found that the OBM have better efficiency as compared to
water-based drilling fluid when they evaluating field data.

Sorgard
et al (2001)

However,
despite its superior hole cleaning, OBM become less favorable types of
drilling fluid under extremely cold-water conditions. This due to the OBM
become sluggish and increase in viscosity with results in increased of
equivalent circulating density (ECD) which can cause fracture of formation.

Ning
et al. (2013)

In
hydrate formation condition, OBM is more favourable due to lover induction
time for hydrate formation as compared to water-based mud. This investigation
has been conducted by Srungavarapu, M. et al. (2017) in his studies. It
states gas is readily dissolvable in oil than water cause the induction time
of hydrate formation in OBM is low.

Werner,
B. et al. (2017)

These
researches have compared the performance between OBM and WBM and it is completely
proved by laboratory results that OBM has shows a magnificent
cuttings-transport ability to the WBM.

Oil-Based
Mud (OBM)

Abduo,
M. I. et al. (2015)

Differ
from the Sorgard’s research, Abduo demonstrates in his studies that OBM have
numerous advantages; for instances OBM has faster penetration rates, shale
stability and providing better gauge hole. Moreover, an excellent drilling
fluid is the one that can drill under excessively high temperature and high
pressure. In his case, OBM able to withstand high temperature over a long
period of time.

 

Table 2.2
(Continued)

Water-Based
Mud (WBM)

Abdua
M. I. et al. (2015)

The
high level of toxicity of OBM gave urgency to the environmental issues. Not
only, OBM can be harmful to environment, it also can be damaging the
equipment especially the rubber type of equipment. Due to these concerns, the
study of WBM in high-temperature and high-pressure have been favorably
preferred than OBM. From the results of this paper, it can be observed that
OBM is the most appropriate drilling fluid in dealing with such conditions if
not violating the environment regulations. In fact, it is crucial to design
an eco-friendly WBM for HPHT drilling.

Patel,
A. et al. (2009) and Lal, M. (1999)

Even
though WBM is less toxicity as compared to OBM and SBM, there are numerous
typical issues encountered with WBM, for instances, swelling of shale formation
which consequently led to lost circulation and hole collapse.

Synthetic
Based Mud (SBM)

Stout,
S. A. et al. (2017), Neff et al. (2000), American Chemistry Council (2006)

These
papers have proven that synthetic-based mud provide spectacular advantages
than OBM in terms of environmental concerns. This is due to the fact that SBM
are designed to be low in toxicity level and rapid degradation process in
marine sediments.

Subhash,
N. et al (2010)

The
difference between OBM and SBM is the type of base fluid used, for instances,
SBM used synthetic material instead of oil. This paper also demonstrates that
the toxicity level of SBM is low because the aromatic content in SBM is low.
Besides, in this study, SBM base fluids and degradation products also exhibit
low in toxicity level which passes local acceptance criteria in Europe.
Hence, SBM is proven to be environmentally friendly.

Akbar
A. et al. (2016), Samira, B. H. et al. (2009), Environmental Protection
Agency Part III (1999)

In
oil well drilling operations, these paper approaches ester-based drilling
fluids which it had been recognized for magnificent performance of any
synthetic-based mud. Besides, they are full bio-degradable drilling fluids, in
other words, they able to improve drilling performance efficiency without
polluting the environment.

 

 

 

Based from the Table 2.2, it shows that
each system of drilling fluid has their advantages and disadvantages related to
environmental impact, cost and reliability in extreme conditions. Drilling
operator must have decided the best in order to minimize the drilling problem
later on. Besides, the main point of select drilling fluid is fluid that have
impressive rheological properties and should be allow to drill at controlled
penetration rate along with low filtration loss as being suggested by
Srungavarapu M. et al. (2017). The typical characterization of synthetic-based
mud has been tabulated in the Table 2.3 and Table 2.4 which were provided by
Baroid and Baker Hughes (Ali, A. D. et al., 2016). These mud property
specifications is the one of the SBM system that currently being utilized in
Gulf of Mexico deep-water drilling operations.

 

Table 2.3

Synthetic-Based Drilling Fluid
Specifications Recommended by Baker Hughes

Mud Weight,
lb/gal

Plastic
Viscosity, cp

Yield Point,
lb/100ft2

Emulsion
Stability, Volts

10.5 – 10.9

35 – 45

15 – 20

>400

10.9 – 14.1

45 – 55

12 – 18

>400

14.1 – 15.1

50 – 60

10 – 15

>500

15.1 – 15.2

50 – 60

10 – 15

>500

15.2 – 15.5

50 – 60

10 – 15

>500

Source:
Ali, A. D. et al. (2016). Experimental investigation of new additive to
optimize the properties of synthetic-based drilling fluid. Journal of Mining and Metallurgy, 52A (1), 37-43.

 

Table 2.4

Synthetic-Based Drilling Fluid
Specifications Recommended by Baroid

Mud Weight,
lb/gal

Plastic
Viscosity, cp

Yield Point,
lb/100ft2

Gel Strength,
lb/100ft2

HPHT Fluid Loss

10.5 – 10.9

35 – 45

15 – 20

8, 15, 18