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USING LINEAR ALKYL BENZENE SULFONATE TO REDUCE
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INTERFACIAL TENSION OF CRUDE OIL
Pipat Pipatpongsanon* and Akkhapun Wannakomol
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Running head: Using LAS to Reduce IFT of Crude Oil (ใส่ เป็ นชื่ อเรื่ องแบบย่อๆ)
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Abstract
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Interfacial tension (IFT) is one of main causes of crude oil movement obstruction
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in oil reservoir. To enhance oil recovery, reduction in crude oil interfacial tension
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is needed. This research aimed to study the reduction of interfacial tension by
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adding the surfactant solution into crude oil. Linear Alkyl Benzene Sulfonate
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(LAS) was selected to use as IFT reducing additive. The effects of LAS
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concentration (5%, 10%, and 15% of concentration by volume) and temperature
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(40◦C-90◦C) on IFT of crude oil samples from Sansai oil field, located in Fang
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basin, were measured by Ring and Plate Method based on ASTM D971-99
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standard. As a result, it was found that the maximum of 20% crude oil IFT
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reducing occurred after adding LAS solution at 10% by volume at 70◦C. IFT was
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decreased from 26.53 dynes/cm to 21.1 dynes/cm.
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Keywords: Linear Alkyl Benzene Sulfonate, Interfacial Tension, Surfactant,
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Crude Oil, Fang’ Oil Fields
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School of Geotechnology, Institute of Engineering, Suranaree University of Technology, 111
University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand.
Email: man_pipat@hotmail.com
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Corresponding Author
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Introduction
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Secondary oil recovery methods have been developed and applied to many reservoirs
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around the world. Waterflooding is a widely used method caused from its low cost,
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availability and well known. It can improve and give more oil recovery compared to
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primary production. However, some wells can be produced only one-third of residual
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oil after primary production and still left the two-thirds behind. To solve this problem,
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the enhanced oil recovery (EOR) is the applicable method. Surfactant flood is a kind of
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EOR that has been employed for more than 40 years in particular of USA mostly in
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depleted oil reservoirs after waterflooding. This technology has been increasing
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interested and developed in many countries because of the oil price increasing. Though
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there are many of researches for finding the new agents to bring the residual oil up from
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the reservoir, almost used agents have hazards to the environment and still so expensive.
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Therefore, chemical flood is the process that is unattractive in some countries. However,
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chemical flood is still needed for some oil reservoirs.
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The most common surfactants used in micellar/polymer flooding are sulfonated
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hydrocarbon. The term “crude oil sulfonates” refers to the product when a crude oil is
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sulfonated after it has been topped. Petroleum sulfonates are sulfonates produced when
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an intermediate-molecular-weight refinery stream sulfonated, while “synthetic
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sulfonates” are products when a relative pure organic compound is sulfonate. In general,
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crude oil and petroleum sulfonates have been used for low salinity application (< 2 to 3
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wt% NaCl). These surfactants have been widely used because they are effective at
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attaining low IFT, relatively inexpensive, and reported to be chemically stable (Green
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and Willhite, 1998).
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Some Researches and Experiments which used Surfactant to Reduce
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IFT are Listed as Follows
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Chen et al. (2005) investigated IFT between oil solutions of cationic gemini
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surfactants. It was found that gemini surfactant were more effective and efficient than
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corresponding conventional surfactants in reducing IFT and could lower the tension of
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kerosene-water interface to ultra-low at very low concentration without other additives.
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The additional of salt resulted in more effectiveness of surfactant in reducing the tension
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of kerosene-water interface and also showed that gemini surfactant had synergism with
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salt. This experiment used crude oil from Zhongyuan oil field of China.
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Iglauer et al. (2009) investigated four different types of surfactants for their
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effectiveness in tertiary oil recovery (TOR). They used basic screening analysis, which
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included IFT measurements, adsorption measurements and phase behavior studies.
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Performance in terms of EOR showed that the surfactant generated a low IFT and also
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showed low adsorption on the reservoir rock material. Used surfactants as a) di-tridecyl
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sulfosuccinic acid ester, b) coconut diethanolamide, c) alkylpolygycosides and d) alkyl
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propoxy sulfate sodium salts were tested for their enhanced oil recovery performance by
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using coreflood tests on Berea Sandstone. Consequently, due to reductions of IFT, this
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led to significant additional incremental oil recovery for 40% TOR, 15% TOR, 75%
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TOR and 35-50% TOR, respectively.
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Due to its properties that can reduce crude oil interfacial tension, easily soluble
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in water, inexpensive and affable with environment, this research selected LAS as an
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IFT reducing agent to study. The expected result of this study is that this surfactant
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would reduce crude oil IFT and can be an alternative IFT reducing agent to use in oil
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flooding process in the future.
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Materials and Methods
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Materials
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Crude oil samples were from Sansai oil field, located in Fang basin, which
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provided by Northern Petroleum Development Center, Defence Energy Department,
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Fang district, Chiang Mai province, Thailand. Properties of crude oil of Sansai oil field
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were collected from previous study of Chumkratoke (2004) and were showed in Table
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1.
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Linear Alkyl Benzene Sulfonate (LAS), used as IFT reducing agent in this study, is
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synthetic anionic surfactant. It was introduced in the 1960 as more biodegradable and
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was used instead of highly branched alkyl benzene sulfonate in general. LAS are
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nonvolatile compounds produced by alkylation and sulfonation of benzene,
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(Sablayrolles et al., 2009). LAS chemical structure is illustrated in Figure 1.
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Method
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IFT test conducted in this study was a static test by ignoring influence of high
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pressure and salinity. IFT of LAS solution and crude oil were measured by Du-Nouy
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ring method and Wilhelmy plate method with KRUSS K10ST tension meter based on
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ASTM D971-99 standard. In Wilhelmy plate method, as illustrated in Figure 2, when
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the bottom of a vertically-oriented detection plate makes contact with a liquid surface,
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the liquid wets the plate surface upward and meniscus is created. At this moment, the
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surface area of the liquid is expanded and IFT tends to contract the surface area as a
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counteraction, and immerse the plate downward. This method determines surface
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tension or interfacial tension by measuring the force bringing the plate downward via a
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counter balance. The KRUSS K10ST tension meter used in this study has range of
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solution between 1 and 999 dyne/cm and range of temperature between 0 and 100◦C.
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Then IFT can be calculated by the following equation.

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
F
L cos 
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where ℓ
=
interfacial tension (mN/m)
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L
=
wetted perimeter of plate (mm)
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Ө
=
the contact angle between the liquid phase and the plate (◦)
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F
=
force (mN/m)
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In this study IFT test processes were conducted as following steps:

Prepared LAS solution in various ratios between LAS and water as 5%, 10%,
and 15% by volume respectively.
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Mixed LAS solution and crude oil sample in 30 cc. glass cups with the ratio of
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5%, 10%, and 15% by volume concentration. Stirred compounds until they were
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dissolved into the solvent and then cooled down to room temperature.
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
Measured IFT of crude oil at range of temperature between 40◦C and 90◦C. This
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was because at the temperature below approximately 40◦C crude oil samples were
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became a wax which could not be measured.
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Results and Discussions
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Measured IFT (dynes/cm) of crude oil at various concentration and temperature (◦C)
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were showed in Table 2 and also graphically illustrated in Figure 3. IFT of crude oil
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measured at 40◦C at 0%, 5%, 10%, and 15% by volume LAS concentration was 31.87,
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29.96, 29.1, and 27.9 dynes/cm respectively. After temperature had been elevated, it
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was found that IFT of every LAS solution concentration tended to decrease (Table 2 and
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Figure 3).
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From Figure 3 it is clearly indicated that when the LAS surfactant was added to
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solvent at 5% by volume concentration, the dissolved surfactant molecules were
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dispersed as monomers. However, when the concentration of surfactant increased to
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10% by volume concentration, the molecules tended to aggregate. This is because,
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above a specific concentration called the critical micelle concentration (CMC), further
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addition of surfactant to 15% by volume concentration compound tended to result in the
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formation of micelle.
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Conclusions and Recommendations
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It could be concluded that the descend changing in crude oil IFT resulted from the
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concentration and temperature of the solutions were ascend changed up to the critical
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micelle concentration (CMC).
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After the CMC had been reached, the more concentration LAS and higher
temperature would not significantly affect on crude oil samples IFT.
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For further study, to get more resolutions authors recommend IFT measurement
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method as the spinning drop method which has a wider range of IFT measurement at
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about 10−5 mN/m to 102 mN/m.
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Acknowledgement
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This research is supported financial and facilities by School of Geotechnology,
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Suranaree University of Technology. Authors would like to acknowledge the Northern
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Petroleum Development Center, Defence Energy Department, Fang, Chiang - Mai,
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Thailand for crude oil samples providing. Authors would like to express sincere
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appreciation and gratitude to Assoc. Prof. Kriangkrai Trisarn and Dr. Chongpan
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Chonglukmani for their valuable suggestions.
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References
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American Society of Testing Material. (1989). Standard test Method for Interfacial
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Tension of Oil against Water by Ring Method. ASTM: D971-99.
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Chumkratoke, C. (2004). Simulation study of oil recovery improvement by water
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flooding in Fang oil field, [Master Thesis]. School of Geotechnology. Suranaree
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University of Technology, p.78-95.
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Green, D.W. and Willhite, G.P. (1998). Enhanced Oil Recovery. Society of Petroleum
Engineers Textbook Vol. 6,. Soc. Petroleum Eng., Houston, TX, 545p.
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Chen, H., Han, L., Luo, P., and Ye, Z. (2005). The Ultralow Interfacial Tensions
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between Crude Oils and Gemini Surfactant Solutions. J. Colloid Interf. Sci.,
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285:872-874.
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Holmberg, K. (2002) Handbook of Applied Surface and Colloid Chemistry. Wiley and
Sons, NY, 219 p.
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Sablayrolles, C., Montréjaud-Vignoles, M., Silvestre, J., and Treilhou M. (2009) Trace
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Determination of Linear Alkylbenzene Sulfonates: Application in Artificially
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Polluted Soil-Carrots System. Int. J. Analyt. Chem., Article ID 404836, 6p.
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Iglauer, S., Wu, Y., Shuler, P., Tang, Y., Goddard III, W.A. (2009). New Surfactant
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Classes for Enhanced Oil Recovery and their Tertiary Oil Recovery Potential. J.
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Petrol. Sci. Eng., 71:23-29.
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Industry Coalition for the SIDS Assessment of LAS. (2005). Linear Alkyl Benzene
Sulfonate, Paris. Available from: www.chem.unep.ch/irptc/sids/oecdsids/las.pdf
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Figure 1. Chemical structure of Linear Alkyl Benzene Sulfonate basis substance in
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dishwashing liquid (Industry Coalition for the SIDS Assessment of LAS,
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2005)
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Figure 2. Wilhelmy plate method modified (Holmberg, 2002)
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0%
5%
10%
Interfacial Tensio(dynes/cm)
40
15%
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30
25
20
30
50
70
90
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Temperature(◦c)
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Figure 3. IFT of crude oil with and without adding surfactant solution at selected
ratio
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Table 1. Physical properties of Sansai’s crude oil (Chumkratoke, 2004)
Properties
Value
Density
0.86 (g/cc)
Viscosity
20.1 (cp)
API gravity
34 (°API)
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Table 2. Measured crude oil IFT from laboratory at various surfactant solution
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concentration and temperature
Temperature
LAS at 0%
LAS at 5%
LAS at 10%
LAS at 15%
(◦c)
concentration
concentration
concentration
concentration
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31.87
29.97
29.1
27.9
50
27.27
27.6
21.8
26.6
60
26.73
27.43
21.4
25.6
70
26.53
26.8
21.1
26.53
80
26.03
26.5
21.47
26.47
90
25.47
26.2
21.3
26.37
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