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* Corresponding author: Krengkrai.M@chula.ac.th
Wax inhibitor performance comparison for waxy crude oil from
Fang oilfield
Kreangkrai Maneeintr*, Tanapol Ruengnam, Thodsaporn Taweeaphiradeemanee and Treetasase Tuntitanakij
Carbon Capture, Storage and Utilization Research Laboratory, Department of Mining and Petroleum Engineering, Faculty of Engineering,
Chulalongkorn University, Bangkok 10330, Thailand.
Abstract. In petroleum chemistry, waxy oil from paraffins can cause operating problems for oil production. The
chemical method is used to remove by using chemicals or additives to prevent the wax problem. In this study, the
performance of wax inhibitor are evaluated by the measurement of pour-point reduction and wax deposition of crude
oil from Mae Soon area, Fang oilfield. Wax deposition is determined by cold finger technique. Wax inhibitors,
hexane, Poly(maleic anhydride-alt-1-octadecene) (PMAO) and monoethanolamine (MEA) are mixed in oil sample
at various concentrations. From the experiment, it is presented that hexane is used to reduce pour-point temperature
up to 19.55 % and to reduce wax deposit up to 92.56 %. Moreover, MEA and PMAO have less effect on pour-point
reduction. However, they have high efficiency to prevent wax deposition. PMAO provide the better wax deposition
performance than MEA. The amount of wax deposit is lower at the same conditions. The percentage of wax deposit
is from 39.19 % to 83.02 % for MEA and from 58.54 % to 88.51 % for PMAO. Furthermore, from the results, the
preferred concentration of hexane can be at 10 % and PMAO can be 7500 ppm at low temperature or 5000 ppm for
higher temperature. The results of this research can be applied to the practical way for wax deposition prevention
operation in Mae Soon area in Fang oilfield to reduce the wax problem in the future.
1 Introduction
In petroleum chemistry, paraffins can cause waxy crude
oil which is a complex mixture of many different
components including paraffins, aromatics, resins,
asphaltenes and other light hydrocarbons [1-2]. Among
these components, the high molecular weight paraffins
are responsible for the various problems encountered
during production, transportation and storage of waxy
crude oils [3]. During the prolonged shut-down of
pipeline transporting waxy crude oils, the paraffin
crystals form continuously in the oil phase due to the
gradual decrease of temperature [4].
Crude oil contains dissolved waxes that can deposit
under the appropriate environmental conditions. These
can build up in production equipment and pipelines,
potentially restricting flow and creating other problems
[3]. For wax mitigation and remediation, there are three
methods that are commonly used, thermal, mechanical
and chemical methods. For this study, the chemical
method is choosen due to the continuous oil production
operation [5-6]. The chemicals used in this study are
hexane, Poly(maleic anhydride-alt-1-octadecene) or
ZPMAO. These are the potential chemicals as inhibitors
to prevent wax formation [7-8]. Also, monoethanolamine
or MEA used as a surfactant to reduce interfacial tension
of oil and water can be applied for this study [9].
In addition, Mae Soon area in Fang oil field,
Chiangmai, Thailand is the brown field area for
petroleum production more than 60 years. Oil from this
area contains waxy components and it has many
operation problems especially when temperature and
conditions change.
Therefore, the main objectives of this study are to
compare the performance of 3 wax inhibitors on original
crude oil and to investigate the effects temperature and
chemical concentration of each inhibitor on wax
deposition of original crude oil from Mae Soon at Fang
oil field and to measure pour point temperature of oil at
various conditions.
This research will investigate the 3 chemical
additives that can reduce Mae Soon crude oil pour point
temperature or wax deposition. Therefore, the benefits
from this project is the performance comparison of wax
inhibitors at various conditions in order to select and
apply the better inhibitor in the real field at the working
conditions in the future.
2 Materials and methods
2.1. Materials
Waxy crude oil is obtained from Mae Soon area, Fang
oilfield in Chaingmai. The physical characteristics of
crude oil contain high amount wax which becomes solid
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0
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E3S Web of Conferences 294, 06005 (2021) https://doi.org/10.1051/e3sconf/202129406005
ICSREE 2021
state in room temperature. The crude oil pour point
temperature is 35.3 °C. Hexane with 95% purity and
PMAO with 95% are purchased from Sigma Aldrich
Company. MEA with a purity of > 99.0 % is purchased
from Sadara Chemical Company.
2.2. Experimental procedures
Pour-point temperature of crude oil is measured
following ASTM standard of ASTM D 5853 [10]. First,
the test tubes are filled with warm crude oil.
Thermocouple is placed in the tube to measure the
temperature. The prepared test tubes in the water bath are
hold by a lab stand.
For wax dposition prevention test, wax deposition
determination is conducted with cold finger technique
[11-12]. The test tube is rested in water bath for 3 hours.
The experimental temperatures are from 25 °C, 35 °C
and 45 °C. The wax inhibitors concentrations are 5%, 10%
and 15% by weight for hexane and 2,500 ppm, 5,000
ppm and 7,500 ppm for MEA and PMAO.
3 Results and discussion
3.1. Effect of Hexane on wax deposition
In this study, hexane is used as a solvent. It has been
investigated the ability on pour-point reduction with
varying concentrations from 5-15%. From the result as
shown in Figure 1, the pour-point temperatures are
35.3 °C, 34.5 °C, 29.4 °C and 28.4 °C at 0% or original
oil, 5%, 10% and 15% hexane concentration,
respectively. The high rate of reduction is from 5% to 10%
hexane and the percent reduction can be up to 19.55% for
15% hexane concentration compared to original oil.
Fig 1. Result of hexane concentration on pour point.
Fig 2. Result of hexane concentration on wax deposition.
For wax deposition of hexane, the experimental
temperature is performed from 25 °C to 45 °C and the
hexane concentration is from 0-15 %. As shown in
Figure 2, the results present that at 25 °C, the amount of
wax has been reduced to 83.38 %, 91.78 % and 92.56 %
for 5 %, 10 % and 15 % hexane, respectively compared
to original oil. Also, at higher temperature like 35 °C and
45 °C, the amount of wax is lower because wax becomes
more liquid and at 45 °C, the amount of wax is at 53.99 %,
54.75 % and 55.37 % lower than original for 5 %, 10 %
and 15 % hexane, respectively. However, it is intereting
that, there is less significant change in wax deposition
prevention after adding more hexane higher from 5%
concentration at 45°C. It can be concluded that for
hexane the preferred hexane concentration can be 10%
because the pour-point reduction and high wax
prevention. This condition is the important data to apply
hexane for wax deposition prevention in the practical
work for the future.
3.2. Effect of MEA on wax deposition
Figure 3 illustrates the results of the effect of MEA for
wax deposition by using MEA from 2500 ppm to 7500
ppm and temperature from from 25 °C to 45 °C. From
the results, MEA has no effect on pour-point reduction
because the pour-point temperature at different MEA
concentrations does not change. Nevertheless, for wax
deposition, the figure shows that adding more MEA or
applying higher temperature can reduce the amount of
wax deposition. At 25 °C, the wax deposit can be reduced
to 79.36 %, 80.76 % and 83.02 % for MEA concentration
at 2500, 5000 and 7500 ppm, respectively. Also, 45°C,
the amount of wax is reduced to 39.19 %, 57.44 % and
63.84 % at 2500, 5000 and 7500 ppm, respectively.
3.3. Effect of PMAO on wax deposition
PMAO is a wax crystal modifier. The addition of PMAO
in crude oil also has less effect on pour-point reduction.
On the other hand, as shown in Figure 4, PMAO has
ability to reduce wax deposition. At 25 °C, the amount of
wax can be reduced for 74.52 %, 78.25 % and 88.51 %
for PMAO at 2500, 5000 and 7500 ppm, respectively.
The amount of wax is reduced less with higher
temperature from 58.54% to 75.41 % at 45 °C. In term
of the effect of temperature, It also can be seen clearly
25
30
35
40
0 5 10 15 20
Pour point (°C)
Concentration (%wt)
Hexane
0
0.5
1
1.5
20 25 30 35 40 45 50
Wax Deposition (g)
Temperature ( C)
Original oil
5% Hexane
10% Hexane
15% Hexane
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E3S Web of Conferences 294, 06005 (2021) https://doi.org/10.1051/e3sconf/202129406005
ICSREE 2021
that an increase in temperature from 25 °C to 45 °C can
decrease the amount of wax deposit to 89.61 % for
original oil and for 83.09%, 81.24 % and 77.77 % at 2500,
5000 and 7500 ppm, respectively. Therefore,
temperature has more effect on wax deposition.
3.4. Comparison of Wax Inhibitors
The performance of wax inhibitors can be compared
based on the pour-point reduction as well as the amount
of wax deposit. From the results of pour-point reduction,
it is obvious that hexane is the only one can reduced
pour-point temperature effectively for 19.55 %
compared to original oil. However, for wax deposition
prevention, it also performs well up to 92.56 % reduction.
However, the effective amount of hexane used is
comparatively higher than other inhibitors. Based on this
result, the suitable concentration is 10% of hexane for
both pour-point reduction and the amount of wax deposit
applications.
Fig 3. Result of MEA concentration on wax deposition.
Fig 4. Result of PMAO concentration on wax deposition.
Like MEA, PMAO has less effect on pour point
reduction and it is not reported here. On the contrary,
both inhobitors have very good performance on wax
deposition prevention. Wax deposit can be lowered with
the higher concentration especially at low temperature.
However, at higher temperature, the concentration of
inhibitors has less effect because wax can be formed less.
The percentage of wax reduction can range from 39.19 %
to 83.02 % for MEA and from 58.54 % to 88.51 % for
PMAO at the same conditions. From these results, it can
be concluded that PMAO has higher performance than
that of MEA at the same conditions. Also, the working
concentration of PMAO can be 7500 ppm at low
temperature or 5000 ppm for higher temperature.
Conclusions
In petroleum indusstry, waxy crude oil can be formed
and it can cause more problems for oil production. The
technology selected to remove the wax problem is the
chemical method with 3 inhibitors, hexane, Poly(maleic
anhydride-alt-1-octadecene) (PMAO) and
monoethanolamine (MEA). In this study, the
performance of wax inhibitor are assessed by the
measurement of pour-point reduction and wax deposition
prevention of crude oil from Mae Soon area, Fang
oilfield. Wax deposition is determined by cold finger
method. The wax inhibitors are combined in oil sample
at various concentrations from 5 % to 15% for hexane
and from 2500 ppm to 7500 ppm for both MEA and
PMAO. From the result, it is shown that hexane is used
effectively to reduce pour-point temperature up to 19.55%
and wax deposition up to 92.56 % reduction.
Furthermore, MEA and PMAO have less effect on pour-
point reduction but have high efficiency on wax
deposition prevention. Between them, PMAO can offer
the better wax deposition prevention performance than
MEA especially at low temperature and high
concentration. The amount of wax deposit is less at the
same conditions. The percentage of wax deposit is
reduced from from 39.19 % to 83.02 % for MEA and
from 58.54 % to 88.51 % for PMAO at the same
conditions. Moreover, based on the results, the working
concentration of hexane can be at 10 % and PMAO can
be 7500 ppm at low temperature or 5000 ppm for higher
temperature. This can be applied to the real field in Mae
Soon area in Fang oilfield to reduce the wax problem in
the future.
Acknowledgments
The authors would like to gratefully acknowledge the
Malaysia-Thailand Joint Authority (MTJA) for financial
support of this project.
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