1.1 obtained throughout the experiments were analysed and

1.1           
Introduction

The planned procedures listed in the methodology section in this
proposal were successfully completed. Citrus Sinensis are prepared and used as
Lost Circulation Material additives. Different concentration and sizes of this
additive were tested for compatibility of this additives to prevent lost
circulation from occurring and how percent of it can be prevented. Following
section complying with the standard stipulated in API RP 13B-2; Recommended
Practice Standard Procedure for Field Testing Oil-Based Drilling Fluids. The
data obtained throughout the experiments were analysed and interpreted.
Summaries of results are generally presented in figures. Typical graph relating
to the experiments will be provided in this chapter, while all tables of raw
data and complete results relating to the experiments conducted are shown in
Appendices.

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1.2           
Mud
Data Analysis

Table 4.1 and Table 4.2 provide the data
obtained for all mud systems in this paper. The results were taken before the
samples undergo Before Hot Rolled (BHR) and After Hot Rolled (AHR) for the mud
rheological properties while HPHT filtration test and Sand Bed Test will be
only performed after the samples have been undergo AHR. The drilling fluid
samples were left for 16 hours in the oven at 150 ºF.

 

1.2.1      
Rheological Properties

The rheological properties for both
particle sizes were calculated in the Table 4.1 and Table 4.2. The graphical
data were shown as in Figure 1. The results were taken before the samples
undergo Before Hot Rolled (BHR) and After Hot Rolled (AHR) for the mud
rheological properties.

 

Table 4.1

Experimental data
result for fine size of CS

PROPERTIES

BASE

3 g

6 g

9 g

AMOUNT

BHR

AHR

BHR

AHR

BHR

AHR

BHR

AHR

600 rpm

59

65

65

84

71

89

65

93

300 rpm

40

45

45

55

49

58

48

61

200 rpm

34

39

44

53

39

54

55

63

100 rpm

29

30

35

40

28

42

37

43

6

20

25

25

30

15

22

18

23

3

15

18

20

27

14

19

18

20

PV

19

20

20

29

22

31

17

32

YP

21

25

25

26

27

27

31

29

GS 10 sec

14

15

16

16

16

17

17

19

GS 10 mins

18

18

17

19

18

20

19

21

 

Table
4.2

Experimental data
result for coarse size of CS

PROPERTIES

BASE

3 g

6 g

9 g

AMOUNT

BHR

AHR

BHR

AHR

BHR

AHR

BHR

AHR

600 rpm

59

65

68

77

80

90

87

93

300 rpm

40

45

49

56

62

64

65

66

200 rpm

34

36

43

48

55

57

53

59

100 rpm

29

30

37

44

40

45

44

52

6

20

25

18

19

19

20

19

20

3

15

18

15

18

14

15

15

17

PV

19

20

19

21

18

26

22

27

YP

21

25

30

35

44

38

43

39

GS 10 sec

16

15

15

17

18

19

18

20

GS 10 mins

18

18

17

20

20

22

19

24

 

1.2.1.1  Plastic Viscosity

Particle size and concentration of Citrus
Sinensis additives of lost circulation material determine the total mass of
drilling fluid. From the Figure 4.1 shown below, it can be observed the plastic
viscosity containing fine size is greater than plastic viscosity with coarse
size. Reducing the particle size of Citrus Sinensis will cause increase in the
fluid viscosity, as the percentage by volume of solids in the mud increasing,
in this case, it affects plastic viscosity as been investigated by Ogbeide, P.
O. et al. (2016).

From the Figure 4.1, it
was found that addition of Citrus Sinensis as lost circulation materials has
improved the rheological properties. It is identified that a relatively low
plastic viscosity is often necessary for having a greater efficiency during
drilling operation as the
viscosity of the drilling fluid increases when it is exposed to subsurface
cuttings (Jamal, J. A., et al., 2007). However, a high viscous mud may not be
really in demand when lost circulation material; in this case Citrus Sinensis
is added.

Figure 4.1 Plastic
Viscosity versus Concentration of CS

 

1.2.1.2  Yield Point

Figure 4.2 shows the graphical data of
yield point and concentrations versus Citrus Sinensis. Yield point is defined
as the ability of drilling fluid in bringing up the cuttings into the surface
(Ramezani, H. et l., 2015). Addition of Citrus Sinensis increases the yield
point of the drilling fluid which is similar to trend of its plastic viscosity
graph that have been discussed earlier.

 

Figure 4.2 Yield Point versus Concentration of
CS

 

From the figure above, YP
of fine particle size increased from 25 lb/100 ft2 to 29 lb/100 ft2
with increasing Citrus Sinensis concentration while YP of coarse particle size
increased significantly from 25 lb/100 ft2 to 39 lb/100 ft2.
As discussed in literature review part, high yield point will increase the
ability of drilling fluid to lift cuttings (Rabbani A et al., 2017). Hence,
adding Citrus Sinensis to the drilling fluid may improves the ability of
liftings subsurface cuttings compared to only adding barite into the formation.
This also has been proven in Nayberg L. et al.’s (2012) research that yield
point increases with increasing particle volume fraction which will occurred
when the applied stress is adequate to cause the network to break up. Besides,
the Citrus Sinensis were dispersed in synthetic based mud due to the absorption
of water into it and from time to time it becomes agglomerated. This phenomenon
was proven by Saikaew W. et al. (2010) that it will increase the viscosity of
drilling fluid.

 

1.2.1.3  Gel Strength

Figure 4.3 and Figure 4.4 shows gel
strength comparisons for 10 seconds and 10 minutes, respectively for both
cases; fine and coarse sizes. Gel strength is defined as the measurement of
shear stress at low shear rate under static condition for a certain period of
time, in this case 10 seconds and 10 minutes.

From both figures, gel
strength obtained increased as the concentration of Citrus Sinensis is
increased. The coarse particle size shows a slightly greater value compared to
fine particle size. These both graph shows the typical yield point graph in
term of their trend.

Figure 4.3 Gel Strength 10 seconds

Figure 4.4 Gel Strength of 10 minutes

 

Furthermore, the drilling
fluid for both particle size showed comparatively higher gel strength value for
10 minutes measurement after the addition of Citrus Sinensis in compared to the
base drilling fluid. This is however an impressive indicator to improve
suspension of drilling cuttings at static condition especially when the
operation is halted due to maintenance, but too high of gel strength will cause
catastrophic problem (Nayberg, T.  M. et
al., 1984). In fact, previous research of Wu B. et al. (2006) states that the
10 minutes gel strength will have higher gel strength as compared to 10
seconds. This is because the particles will have more time to arrange and align
themselves in an appropriate manner in which both repulsive and attractive
forces best satisfied.

 

1.2.2      
Mud Cake Thickness and Filtrate

Figure 4.5 and Figure 4.6 shows a
relationship graph between filtration loss and concentration of Citrus
Sinensis. An impressive result of fluid loss is shown in Figure 4.5 with both
particle sizes show different trend. After the Citrus Sinensis were added,
fluid loss was slightly larger than of the base fluid.

Increasing Citrus Sinensis
concentrations in the formulation indeed helps reduce the amount of filtrate
produced, however, in this case, an optimum range of combination should be
investigated for better formulation in order to have an extraordinary lower
filtrate volume. It is seen that at 6 g concentration of Citrus Sinensis, the
filtrate volume was decrease to 5.6 mL in compared to the based case.

Figure 4.5 Filtration Loss

 

However, increasing the
concentration of 9 g Citrus Sinensis has caused the fluid loss to be increase
back. This indicated that increase the concentration of 9 g of Citrus Sinensis
in synthetic based drilling fluid was not enough to plug the pores, in this
case, filter paper. It is proven that the important factors in controlling the
permeability are the shape, the size and of course, the deformability of the
solids in the drilling fluid system (Windarto et al., 2011). Particles of one
micron or smaller size will enhance the extraordinary and impressive mud cake
composition as been demonstrates by Ibrahim N. et al. (2006) in his paper.

From the figure also, it
can be observed that for fine particle case, as the concentration of Citrus
Sinensis increases, the fluid loss is decreases. This encouraging result proves
that fine particle of Citrus Sinensis can be used as an alternative lost
circulation material with better formulation of drilling fluid. The theory also
proves the fact that as the amount of lost circulation material additives is
increasing, the viscosity is increases, thus cause the water to be less filtered.
The higher the viscosity of the drilling fluid, the better the formulation is,
the most desirable of Citrus Sinensis can be as lost circulation material
additive.

Figure 4.6 Mud Cake Thickness

 

The thickness was
measured where it ranged from 1.75 in to 2.4 in. It can be observed from the
figure above that there is a decrease in the thickness of the filter cake
formed as the concentration of Citrus Sinensis in the drilling fluid increased.
The synthetic based mud with 6 g concentration of Citrus Sinensis, has a small
value of thickness. It was found in earliear research that the filter cake
thickness is depend on the filter porosity and formation permeability (Jian H.
et al., 2013).

As expected, the new
approaches of nano-sized Tapioca starch brought by Mansoor Z. et al. (2016) has
been implemented in this paper where the sample with thicker filter cake
experienced more severe change in the permeability due to greater cumulative
volume of filtration. In normal conditions, the thick filter cake will enhance
the chance of drilling problems such as stuck pipe. Thus, based on this result,
the lower the filtrate volume, the thinner the filter cake formed, indicates
that good fluid loss control in drilling fluid, hence shows that Citrus
Sinensis has a potential to be an impressive fluid control additive not only
being as lost circulation material additives.

 

1.2.3      
Sand Bed Test

From the Figure 4.7, sand bed
test data shows that 6 g concentration of Citrus Sinensis has an astonishing
film-forming plugging ability. It can well prevent sandstone reservoir from
seepage and enhance the bearing capacity of the borehole wall. As it can be
seen from the figure, the base sample, the drilling fluid enter the formation
and within 5 minutes, it has already damaging the whole 10-cm formation
thickness.

 

Figure 4.7 Sand Bed Test

 

Adding more concentration
of this additive into the synthetic based mud can slow down the formation
damage as it can be observed for 9 g concentration of Citrus Sinensis. The
first minutes, the drilling fluid able to damage the formation around 2.3 cm
while 6 g concentration of Citrus Sinensis damaging the formation around 2.0 cm
for the first minute. If the mud cake permeability is low, then the filtration
velocity is low as for 6 g and 9 g concentration of Citrus Sinensis.

In actual conditions,
Mansoor Z. et al. (2016) identifies two causes of formation damage by drilling
mud are filtrate invasion and solid invasions. In this case, using incompatible
fluid loss control additive such as improper particle size with drilling fluid
will enhance the formation damage and increase lost circulation (Fathi, B., et
al., 2004). It can be observed from Figure 4.7, the invasion velocity of
drilling fluid filtrate for coarse particle size case is fast. The drilling
fluid invasion is due to absence of filter cake that prevents solid particles
invasion into the formation (Calcada, L. A. et al, 2015). In this case, 6 g and
9 g concentration of Citrus Sinensis of coarse size which is 6.00 mm are unable
to form a filter cake in order to prevent the drilling fluid from damaging the
formation.

Hence, it can be observed
that 6 g of Citrus Sinensis is the optimum concentration and most suitable lost
circulation material additive since it able to slow down and prevent the formation
from damage.