Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Emulsification of Indian heavy crude oil using a novel surfactant for pipeline transportation

Emulsification of Indian heavy crude oil using a novel surfactant for pipeline transportation Pet. Sci. (2017) 14:372–382 DOI 10.1007/s12182-017-0153-6 ORIGINAL PAPER Emulsification of Indian heavy crude oil using a novel surfactant for pipeline transportation 1 1 Shailesh Kumar Vikas Mahto Received: 1 June 2016 / Published online: 12 April 2017 The Author(s) 2017. This article is an open access publication Abstract The most economical way to overcome flow Keywords Heavy crude oil  Oil-in-water emulsion assurance problems associated with transportation of heavy Pipeline transportation  Sunflower oil  Rheology crude oil through offshore pipelines is by emulsifying it Stability with water in the presence of a suitable surfactant. In this research, a novel surfactant, tri-triethanolamine monosun- flower ester, was synthesized in the laboratory by extract- 1 Introduction ing fatty acids present in sunflower (Helianthus annuus) oil. Synthesized surfactant was used to prepare oil-in-water In past decades, a progressive decrease in conventional oil emulsions of a heavy crude oil from the western oil field of reserves has led to a dramatic increase in production of India. After emulsification, a dramatic decrease in pour heavy crude oil. However, transportation of such highly point as well as viscosity was observed. All the prepared viscous crude oil through pipelines is a major challenge for emulsions were found to be flowing even at 1 C. The petroleum industries especially in offshore conditions. emulsion developed with 60% oil content and 2wt% sur- Heavy crude oils have viscosities of more than 1000 mPa s factant showed a decrease in viscosity of 96%. The sta- at room temperature. However, viscosity of crude oil bility of the emulsion was investigated at different should be less than 200 mPa s at 15 C for its transporta- temperatures, and it was found to be highly stable. The tion through pipelines (Kessick and Denis 1982). The effectiveness of surfactant in emulsifying the heavy oil in flowability of crude oil at the pumping temperature is an water was investigated by measuring the equilibrium important factor that affects pipeline transportation. Heavy interfacial tension (IFT) between the crude oil (diluted) and crudes usually have higher pour points due to high content the aqueous phase along with zeta potential of emulsions. of high molecular weight components, such as waxes, 2wt% surfactant decreased IFT by almost nine times that of asphaltenes and resins. In conditions where the atmo- no surfactant. These results suggested that the synthesized spheric temperature is below the pour point, crude oil gels surfactant may be used to prepare a stable oil-in-water completely and causes severe transportation problems. emulsion for its transportation through offshore pipelines Especially in the cold offshore environment, waxes and efficiently. asphaltenes deposit over inner surfaces of pipelines and eventually clog the pipelines, which further increases the pumping cost. Therefore, several methods are employed by petroleum industries to transport crude oils through pipelines, dilu- & Vikas Mahto tion/blending of crude with lighter oil or organic solvents, vikas.ismpe@hotmail.com preheating of crude and subsequent heating of pipelines, Department of Petroleum Engineering, Indian Institute of use of pour point depressants (PPDs), application of drag Technology (Indian School of Mines), Dhanbad, Jharkhand, reducing additives and development of core annular flow India (CAF) and in situ oil upgrading (Martı´nez-Palou et al. 2011). However, each of these methods has economic, Edited by Yan-Hua Sun 123 Pet. Sci. (2017) 14:372–382 373 technical and logistical drawbacks when it comes to market in Kolkata, India. Polythene ethylene glycol (PEG) transportation of heavy crude oil through offshore pipe- and triethanolamine (TEA) were obtained from Loba lines. Another pipeline technique favourable for cold off- Chemie Pvt. Ltd. (Mumbai, India). n-heptane, n-decane, shore environments is the transportation of heavy crudes as toluene, HCl and chloroform were procured from Merck oil-in-water (O/W) emulsions. Specialties Pvt. Ltd. (Mumbai, India). Methanol, sodium Oil-in-water emulsions are thermodynamically unsta- chloride, sodium carbonate, acetone, p-toluene sulphonic ble dispersions of the oil phase in the water phase. They are acid, acetic acid, petroleum ether (40–60 C) and ace- subjected to several breakdown processes like flocculation, tonitrile were received from Avantor Performance Mate- coalescence, Ostwald ripening and creaming (Langevin rials India Ltd. (New Delhi, India). et al. 2004). In order to make these emulsions kinetically stable, a suitable surfactant (or mixture of surfactants) is 2.2 Synthesis of surfactant always added, which adsorbs at the oil/water interface and forms a strong interfacial film (Jiang et al. 2013). However, Hydrolysis of sunflower oil (SO) Sunflower oil (50 g) was a particular surfactant may not be suitable for different reacted with 10% NaOH solution (250 mL) at 150 C crude oils due to variation in physicochemical properties. under constant stirring (450 rpm) in a three-necked flask Fatty acids (FAs), derived from different vegetable oils, are along with gradual addition of water (400 mL) for 2 h. raw materials for preparation of surfactants through ester- After reaction, a hot solution of 30% HCl (150 mL) was ification or polymerization. Surfactants synthesized using added and the mixture was kept in a water bath at 80 C vegetable oils have various advantages. They are cheaper, until the oily layer became clear. The oily layer was then biodegradable and cause no adverse effect on nature. In separated and collected as hydrolysed sunflower oil (HSO), this study, we used sunflower oil to synthesize a novel a mixture of several free fatty acids. surfactant. Sunflower oil is a triglyceride obtained from Synthesis of tri-triethanolamine TEA (149 g) was con- pressing sunflower (Helianthus annuus) seeds. Alkaline densed in the presence of NaOH (1.6 g) as a catalyst. The hydrolysis of these triglycerides produces FAs and glyc- reaction was carried at 260 C under constant stirring erol. Fatty acids from sunflower oil consist of 6.8% pal- (450 rpm) in a three-necked flask until 36 g of water was mitic, 5.0% stearic, 19.6% oleic and 68.6% linoleic acids collected in a Dean and Stark trap. The used catalyst was (Harrington and D’Arcy-Evans 1985). Hydrolysed sun- then neutralized by washing the obtained product with 5% flower oil was esterified with a trimer of triethanolamine to acetic acid solution. To further wash out impurities, the develop a new surfactant as ester and further evaluated as product was dissolved in petroleum ether (b.p. 40–60 C) emulsifier for preparation of heavy oil-in-water emulsions. and an organic layer was separated. The remaining solvent The estimated cost of the synthesized surfactant is very low was distilled off using a Soxhlet apparatus to give tri-tri- as compared to the cost of commercial surfactants. Con- ethanolamine (TTEA) (Hafiz and Abdou 2003). sidering the economy, it is very important for petroleum Esterification of HSO and TTEA HSO (36 g) was reac- industries to maximize the oil content as well as minimize ted with TTEA (51 g) in the presence of a catalyst, p- the requirement of surfactant to prepare a stable emulsion toluene sulphonic acid (0.0108 g). The reaction was carried with acceptable viscosity and pour point. at 150 C with continuous stirring, and water was removed The objective of current research is to synthesize a azeotropically as it was formed. The product was then cheap natural surfactant from sunflower oil that is suit- washed with a hot solution of 5% Na CO to remove the 2 3 able for preparing an oil-in-water emulsion of an Indian catalyst and then dissolved in petroleum ether (b.p. heavy crude oil to facilitate its transportation through off- 40–60 C). After separating the organic layer, the solvent shore pipelines. Oil content and the amount of surfactant was distilled off to obtain purified tri-triethanolamine required were further optimized by investigating their monosunflower ester (TMSE) as a desired surfactant (Hafiz effect on pour point, viscosity, stability, droplet size dis- and Abdou 2003). Physical state of the surfactant is tribution, interfacial tension and zeta potential of the pre- semisolid at 25 C and brownish-black in colour. It has a pared emulsions. density of 1.102 gm/cm at 15 C. 2.3 Characterization of crude oil 2 Experimental Heavy crude oils are usually produced in the form of water- 2.1 Materials in-oil emulsion (Dicharry et al. 2006), so the initial water content in crude oil was measured using the Dean and Stark Heavy crude oil sample was collected from a Rajasthan oil method (ASTM D4006-11 2011). Water was then sepa- field, India. Sunflower oil was procured from a local rated with aid of a commercial demulsifier (PEG 200) and 123 374 Pet. Sci. (2017) 14:372–382 heating to obtain pure heavy crude oil. Further, the density measurement of rheology of the crude oil and prepared (ASTM D1480-15 2015) and pour point (ASTM D5853-11 emulsions, respectively. 2011) of the heavy crude oil were also determined using standard ASTM methods. SARA analysis was performed to 2.7 Measurement of emulsion stability characterize crude into four major components: saturates, aromatics, resins and asphaltenes (Jha et al. 2014). Wax Immediately after preparation of emulsions, each emulsion content was determined using the modified Universal Oil was transferred to three separate 10-mL glass tubes (0.1- Products (UOP) 46-64 method (Sharma et al. 2014), and mL graduation) and tightly stoppered with a glass lid. wax appearance temperature (WAT) was determined using These three separate groups of emulsion samples were then the viscosity method (Dantas Neto et al. 2009). kept at 15, 25 and 35 C to allow separation of water over time from these emulsion samples. The amount of water separated at the end of six days was noted and the emulsion 2.4 Preparation of emulsions stability was calculated using the following equation. An aqueous phase was first prepared by dissolving the S ¼ðÞ 1  V=V 100% ð1Þ surfactant in distilled water at 65 C. The heavy crude oil where S is the emulsion stability; V is the water volume in sample was preheated to 65 C to improve its fluidity the initial emulsion, mL; and V is the volume of water before adding it to the aqueous phase. Emulsions were then separated from the emulsion, mL. prepared using a Hielscher ultrasonic homogenizer with an UP200Ht processor at a working frequency of 26 kHz and 2.8 Interfacial tension and zeta potential 100% amplitude for a fixed irradiation time of 10 min. In measurements this study, the oil content was varied in the emulsion, keeping the volume of the surfactant constant (2wt%) with A Texas-500 spinning drop tensiometer (Data-Physics, respect to the total volume of the emulsion. Again for Model No: SVT 15 N) was used to measure interfacial specific series of experiments, at the optimized oil content, tension (IFT) between the oil and the aqueous phase at the surfactant concentration in the emulsion was varied to different surfactant concentrations at 25 C. Due to the obtain an optimum surfactant concentration. very high viscosity of the crude oil, it was impossible to inject a drop of oil using a microlitre syringe in the cap- 2.5 Fourier transform infrared (FT-IR) illary tube filled with the aqueous phase. Therefore, crude spectroscopy oil had to be diluted with n-decane (40% v/v) to make it flowable (Zhao et al. 2013). During measurement, the Infrared spectra of both crude oil and the synthesized capillary tube was rotated at 2000 rpm for 600 s to obtain surfactant were recorded using a Perkin-Elmer spectrum 2 equilibrium IFT values. spectrophotometer assisted by Spectrum-10 software to Zeta potential of emulsions was measured using a Zeta- analyse the functional groups present. Software collected Meter System 4.0 (Zeta-meter, INC., Staunton, VA) to spectra, in absorbance mode, in the spectral region of from study the charge properties of oil droplets in the emulsion -1 4000 to 400 cm . Further infrared spectra of emulsion at room temperature. To prepare samples for measurement, systems were also recorded to compare and analyse the 0.1 mL of each emulsion was diluted with 100 mL of functional groups. distilled water. At least five different particles of each sample were tracked to obtain the average value of zeta potential. 2.6 Measurement of pour point and rheology of the crude oil and emulsions 2.9 Measurements of oil droplet size and size distribution The main objective of the emulsification process is to decrease the pour point and enhance the flowability of the Size and distribution of oil droplets in prepared emulsions heavy crude oil. Pour points of emulsions were measured were determined using a Zetasizer Nano S90 particle size using the ASTM method (ASTM D5853-11 2011). The analyser procured from Malvern Instruments Ltd. at 25 C. rheological flow behaviour of crude oil and emulsions was Dynamic light scattering was conducted at a 90 scattering investigated at 25 C using a Bohlin Gemini 200 rheometer angle to measure particle sizes with this particle size (Gemini 200 software), supplied by Malvern instruments. analyser. This instrument analyses the diffusion of particles Cone-plate (25-mm plate diameter, 2.5 cone angle and moving under Brownian motion by measuring the scattered 70-lm gap) and parallel-plate (25-mm plate diameter at light intensity and converts this to size and a size two gaps, 750 and 500 lm) geometries were used for 123 Pet. Sci. (2017) 14:372–382 375 distribution using the Stokes–Einstein relationship. In order attributed to its high wax content. As reported, the crude oil to make the emulsion sample optically clear and to avoid was found to be highly asphaltinic in nature and very rich the effect of multiple scattering, 0.1 mL of emulsion was in the resin fraction, which makes crude oil heavier and diluted with 15 mL of distilled water. Tests were run three restricts its flowability. A very high fraction of saturates times, and the test duration was shortened to 10 s to avoid (66.5%) was present in crude oil, which provides an effect of coalescence of droplets during measurement. asphaltene-hostile environment and assists in deposition of asphaltenes (Alcazar-Vara and Buenrostro-Gonzalez 2011). 3 Results and discussion 3.2 Infrared spectroscopic analysis In the present investigation, a surfactant was synthesized by extracting free fatty acids from sunflower oil and FT-IR spectra of heavy crude oil, TMSE and O/W emul- evaluated as an emulsifier. Oil-in-water emulsions were sion are shown in Fig. 1, and the observed peaks with prepared to optimize oil content and surfactant concentra- associated functional groups are given in Table 2. Char- tion by investigating their effects on pour point, rheology acteristic peaks of alkyl groups (CH and CH ) due to 3 2 and stability of emulsions. Effects of droplet size distri- stretching vibration and bending vibration with strong -1 bution in emulsions on their viscosity and stability were absorbance at 2919, 2850 and 1462 cm were observed also examined along with discussion of interfacial prop- for heavy crude oil. Such high absorbance can be attributed erties, IFT and zeta potentials of emulsions at various to high contents of saturates and wax in heavy crude oil. -1 surfactant concentrations. Combination of the multiple bands around 1114 cm and -1 the band at 1736 cm confirms the presence of ester in the 3.1 Analysis of crude oil synthesized surfactant. Presence of aromatic nuclei observed in the crude oil may be due to the presence of The results of water content, API gravity, pour point, wax asphaltenes and resins (Quiroga-Becerra et al. 2012). Peaks -1 content, WAT and SARA analysis of crude oil are reported around 719 and 666 cm in heavy crude oil and TMSE, in Table 1. The Dean and Stark method confirmed the respectively, represent rocking vibration of the backbone of presence of a large amount (45%) of dispersed water in the carbon chains having six or more carbon atoms (Quiroga- crude oil (W/O emulsion) sample. API gravity of heavy Becerra et al. 2012). In spectra of the emulsion system, a -1 crude oil is 21.27, so it can be classified as heavy crude oil very strong and broad absorption band at 3443 cm was according to API convention. A large amount of wax is observed due to the presence of hydroxyl groups from H O present in heavy crude oil, which is a major factor in after formation of the O/W emulsion. The absorption bands resisting flow as these wax crystals start appearing at of alkyl groups were greatly weakened, suggesting the temperature around 55 C. These wax crystals grow at breaking of C–C bonds and shortening of C-chains thus further decreasing temperatures, start to precipitate and improving the flowability of heavy crude oil. Also the band -1 form a solid phase. A very high pour point (42 C) was due to rocking vibration of C-chains shifted to 495 cm observed for this particular heavy crude oil which can be that can also suggest that the number of C-atoms in the chain has been reduced due to emulsion formation. Table 1 Physicochemical properties of heavy crude oil 3.3 Depression in pour point Parameter Observed value Method Water content, % (v/v) 45 ASTM D4006-11 In order to avoid flow assurance problems in pipelines -3 under offshore conditions, the pour point of emulsions Density at 15 C, g cm 0.9254 ASTM D1480-15 should be very low. Ahmed et al. (1999) found the pour Specific gravity at 15 C 0.9262 ASTM D1480-15 point to be 6 and 9 C, respectively, for emulsions with oil API gravity at 15 C 21.27 content of 60% and 70%, respectively, when the pour point Pour point, C 42 ASTM D5853-11 of the crude oil was 18 C. Zaki (1997) also reported a Wax content, % (w/w) 11 Modified UOP 46-64 decrease in the pour point of crude oil from 13 to 7 C after WAT, C 55 Viscosimetry emulsification with 70% oil content. Pour point is a very SARA analysis, % (w/w) important flow parameter, and for all the prepared emul- Saturates 66.5 sions in our study, the measured pour point was found to be Aromatics 10.5 remarkably low compared to the pour point of heavy crude Resins 8.5 oil (42 C). All the emulsions prepared were flowing at Asphaltenes 6.5 even 1 C, which is highly suitable for offshore conditions. 123 376 Pet. Sci. (2017) 14:372–382 Crude oil O/W emulsion Surfactant 1650 916 2925 666 4000 3500 3000 2500 2000 1500 1000 500 -1 Wavelength, cm Fig. 1 FT-IR spectra of heavy crude oil, synthesized surfactant and prepared emulsion -1 Table 2 Wave number (cm ) a Functional group Type of vibration Crude oil Surfactant Emulsion for dominant peaks detected from FT-IR O–H in water Stretching – 3417 3443 =C–H in aromatics Stretching – 3010 – C–H in CH ,CH Asymmetric stretching 2919 2925 2917 3 2 C–H in CH ,CH Symmetric stretching 2850 2853 2849 3 2 C=C in alkene/aromatic nuclei Stretching 1606 1650 1632 Unsaturated C=C In-plane bending 1017 916 – C=O in ester Stretching – 1736 – C–O in ester Stretching – 1114 – C–H in CH ,CH Symmetric bending 1462, 1377 1409 1463 3 2 –(CH ) – Rocking 719 666 495 2 n Emulsion with 60% oil content and 2wt% surfactant 3.4 Rheological behaviour of heavy crude oil behaviour of the shear-thinning profile was observed for and prepared emulsions heavy crude oil. For parallel-plate measurements at two gaps, instead of coinciding, lower apparent viscosity values Flow behaviour of the heavy crude oil and emulsions was were observed at lower gap size (at 500-lm gap) for each investigated in a rate-controlled (CR) mode over a shear emulsion over the range of shear rate studied due to -1 rate range of 100–1000 s . The rheometer provided flow occurrence of the wall slip effect. However, all data points behaviour curves as both shear stress vs. shear rate and from both gaps appeared to fall close to a single curve, apparent viscosity vs. shear rate, along with respective indicating the slight possibility of wall slip. Apparent wall data. Figure 2 shows the rheological behaviour of heavy slip or wall depletion effects are observed for concentrated crude oil and prepared emulsions by varying the oil content emulsion systems in rheometers due to displacement of the at a constant surfactant concentration (2wt%), measured at dispersed phase away from the solid boundaries (walls), two gaps using parallel-plate geometry. Non-Newtonian and this displacement of the dispersed phase is caused due Transmittance, % Pet. Sci. (2017) 14:372–382 377 gap sizes are comparatively presented in Table 3 as the 100% -1 40% degree of viscosity reduction at 546 s shear rate. Up to 50% 50% oil content, emulsions showed close to Newtonian 55% behaviour, whereas, when the oil content further increased, 60% they started to behave as non-Newtonian shear-thinning 1 fluids. Shear-thinning behaviour suggests that the emulsion viscosity decreased as the pumping pressure increased. At -1 high shear rate (546 s ), the apparent viscosity of heavy 0.1 crude oil was found to be 5081 mPa s, whereas, after an emulsion was formed with 40% oil content, the emulsion viscosity reduced dramatically by 99.8% and reached 0.01 9.5 mPa s. Furthermore, an increase in the oil content led to an increase in the emulsion viscosity. At 60% oil con- 0 200 400 600 800 1000 -1 tent, the emulsion viscosity increased to 81.2 mPa s, where Shear rate, s the degree of viscosity reduction was around 98.4%. Fur- Fig. 2 Influence of oil content on the rheology of the emulsions at ther increase in the oil content led to an inversion of the 2wt% surfactant, measured at 25 C. Solid and dashed lines represent O/W emulsion into a W/O emulsion. From the results data at 750- and 500-lm gaps, respectively observed and considering the maximum throughput of oil through pipelines, it is clear that the optimum volume of oil to action of various physicochemical forces (Barnes 1995). was 60% for preparing a stable emulsion with The presence of wall slip poses a special problem while acceptable viscosity. measuring actual rheological properties of emulsions. At 60% oil content, the optimum amount of surfactant During rheological measurement of oil-in-water emulsions, required to stabilize emulsions with acceptable viscosity depletion of the oil phase with an increase in shear stress was determined by measuring the rheology of emulsions of leaves the low-viscosity liquid (continuous phase) adjacent various surfactant concentrations. Figure 3 shows the to the boundary; thus, viscosities observed in such condi- effect of surfactant concentration on the rheology of tions are much lower than the actual ones (Pal 2000). emulsions, measured at two gaps using the parallel-plate However, during pipeline transportation of emulsions, due geometry. Results obtained at both gap sizes are compar- to slip, dispersed particles will be displaced away (towards atively presented in Table 4, and results at 750 lm are centre, region of low shear) from the smooth solid wall of further discussed. As the surfactant concentration pipelines and facilitate the flow; therefore, estimation of decreased from 2wt% to 1wt%, the apparent viscosity of actual rheological properties of an emulsion is important emulsions also decreased. At 1wt% surfactant, the emul- for industries involved in pipeline transportation. Apart sion viscosity was reduced to approximately 99.3%. from the geometry and shear rate used for measurement, However, at higher concentrations (3wt% surfactant), the possibility of wall slip also depends on the size of dispersed emulsion viscosity was 98.6 mPa s, reduced by 98.0%. droplets in an emulsion. Lower dispersed droplet size les- This could be attributed to the fact that higher emulsifier sens the chances of occurrence of wall slip inside the concentration decreases the interfacial tension between oil rheometer (Barnes 1995). All emulsions studied in this and water, which leads to formation of smaller oil droplets. work possessed droplet sizes lower than 400 nm, discussed As a result of a decrease in droplet sizes, the number of in Sect. 3.8, which also suggests lower chances of wall slip. droplets contacting water surface increases which ulti- Zahirovic et al. (2009) utilized the parallel-plate mately increases the emulsion viscosity (Azodi and Nazar geometry at different gap sizes for very low apparent shear 2013b). It is not economical to use a large amount of -1 rate up to 1.0 s and the vane geometry for shear rate surfactant. On the other hand, stability of the emulsion at -1 further up to 100 s , in their study of ammonium nitrate- lower surfactant concentration is another important factor in-diesel oil emulsion. We have considered the high shear to choose an optimum concentration. rate in our study because in most crude oil transportation pipelines actual flow takes place at shear rates around 3.5 Interfacial tension analysis -1 500 s , where the shear rate near or on the pipe wall may be even higher (Azodi and Nazar 2013a; Johnsen and Surfactant effectiveness as an emulsifier is most impor- Rønningsen 2003). Since rheological measurement carried tantly evaluated by its ability to decrease the IFT between out at a bigger gap size is relatively less prone to wall slip crude oil and water. Figure 4 demonstrates the equilibrium (Pal 2000), results obtained at higher gap size (750 lm) are IFT values between heavy crude oil (diluted) and the further discussed here. However, results obtained at both aqueous phase at various surfactant concentrations. It was Apparent viscosity, Pa s 378 Pet. Sci. (2017) 14:372–382 -1 Table 3 Viscosity reduction in emulsions of different oil contents at two gap sizes and 546 s shear rate Oil content, % Parallel-plate geometry 750-lm gap 500-lm gap Apparent viscosity, mPa s Viscosity reduction, % Apparent viscosity, mPa s Viscosity reduction, % 60 81.2 98.4 75.4 98.5 55 57.2 98.9 48.3 99.0 50 19.4 99.6 12.4 99.7 40 9.5 99.8 7.9 99.8 Apparent viscosity of heavy crude oil is 5081 mPa s 1.3 -40 1.0 wt% IFT 1.2 1.5 wt% -45 Zeta potential 2.0 wt% 1.1 2.5 wt% 1.0 3.0 wt% 0.9 -55 0.8 0.1 0.7 0.6 -65 0.5 0.4 0.3 -75 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.01 Surfactant concentration, wt% 0 200 400 600 800 1000 -1 Shear rate, s Fig. 4 IFT between crude oil and the aqueous phase and zeta potential as a function of surfactant concentration Fig. 3 Influence of surfactant concentration on the rheology of emulsions of 60% oil content, measured at 25 C. Solid and dashed 0.5wt% surfactant addition. At 2wt% surfactant, the IFT lines represent data at 750- and 500-lm gaps, respectively value decreased to 0.69 mN/m, whereas at 3wt%, IFT reached to 0.37 mN/m. The decreased IFT value con- observed that with increasing surfactant concentration in tributed largely to a subsequent decrease in the drop size of the aqueous phase, IFT values decreased efficiently. IFT dispersed crude oil. As a result of decreased particle size between diluted crude and water with no surfactant was distribution, viscosity as well as the stability of the emul- around 6.15 mN/m and decreased to 1.10 mN/m after sion increased. -1 Table 4 Viscosity reduction in emulsions of different surfactant concentrations at two gap sizes and 546 s shear rate Surfactant concentration, wt% Parallel-plate geometry 750-lm gap 500-lm gap Apparent viscosity, mPa s Viscosity reduction, % Apparent viscosity, mPa s Viscosity reduction, % 1.0 34.4 99.3 28.9 99.4 1.5 46.1 99.1 45.8 99.1 2.0 81.2 98.4 75.4 98.5 2.5 56.2 98.9 55.9 98.9 3.0 98.6 98.0 82.8 98.4 Apparent viscosity of heavy crude oil is 5081 mPa s Apparent viscosity, Pa s ITF, mN/m Zeta potential, mV Pet. Sci. (2017) 14:372–382 379 3.6 Zeta potential analysis increases in both oil content as well as surfactant concen- tration led to an increase in the emulsion stability. On the The zeta potential measurement helps in predicting emul- other hand, temperature also played a very important role sion stability by predicting the tendency of the emulsion to in the emulsion stability. Emulsion samples kept at lower coalesce or flocculate. It characterizes distance between the temperatures showed higher stability than at higher tem- emulsion droplets by calculating the electric charge on the peratures. As the oil content in emulsion increased from surface of droplets. A higher absolute value of the zeta 40% to 60% at 2wt% surfactant, the emulsion stability potential (either negative or positive) is interpreted as increased from 51.7% to 85% at 35 C. When the tem- meaning there is higher charge on the droplets, which perature decreased from 35 to 15 C, the stability of the results in greater chances of them repelling each other and emulsion of 40% oil increased from 51.7% to 83.3% and avoiding coalescence and flocculation. A lesser charge on for the emulsion of oil content above 40%, 100% stability the droplets allows them to come closer and coalesce/ was achieved. The effect of temperature can be explained flocculate (Jha et al. 2015). Figure 4 summarizes the effect by the fact that a decrease in temperature leads to a on zeta potential of O/W emulsions with increasing sur- decrease in interfacial tension between oil and water. As a factant concentration. It was observed that the absolute result, the decrease in internal energy of the molecules may value of zeta potential increased from 44.3 to 71.2 mV as decrease the pressure required to induce the interfacial film the surfactant concentration increased from 1wt% to 3wt% thinning and ultimately increases the coalescence time in the emulsion. These results suggest that with an increase (Liyana et al. 2014). in the surfactant concentration, the charge concentration on The emulsions with 60% oil content were completely emulsion droplets also increased which led to production of stable at 15 C, despite variation in surfactant concentra- a stable emulsion. tion from 1wt% to 3wt%. However, when the temperature increased to 25 C, the stability of emulsion with 1wt% surfactant reduced to 82.5%, and furthermore reduced to 3.7 Stability of emulsions 70% at 35 C. Again, an increase in the stability at higher temperatures was achieved by increasing the surfactant Emulsion stability is a very important parameter which concentration. The emulsion with 3wt% surfactant was depends on factors like concentrations of oil/water and found to achieve stability around 95.0% and 92.5% at 25 their density difference, water phase viscosity, salinity and and 35 C, respectively. An increase in the surfactant pH, choice and amount of surfactant, size of dispersed oil concentration results in an increasing number of surfactant droplets, preparation method and duration and temperature molecules absorbed at the oil/water interface which pro- of homogenization (Lim et al. 2015). Based on water vides a barrier to the coalescence of dispersed oil droplets, separation observed after 6 days at different temperatures, thus stabilizing the emulsion (Zaki 1997). Additionally, the emulsion stability is plotted in Figs. 5 and 6, respec- application of ultrasonic waves causes formation of dro- tively, against variations in oil content and surfactant plets with smaller sizes, which increases the total interfa- concentration. It was observed from the results that cial area allowing more particle-to-particle interaction, and 15 °C 15 °C 25 °C 25 °C 35 °C 35 °C 40 45 50 55 60 1.0 1.5 2.0 2.5 3.0 Oil content, % Surfactant concentration, wt% Fig. 5 Emulsion stability as a function of oil content at different Fig. 6 Emulsion stability as a function of surfactant concentration at temperatures (2wt% surfactant) different temperatures (60% oil content) Emulsion stability, % Emulsion stability, % 380 Pet. Sci. (2017) 14:372–382 finally leads to enhancing the emulsion stability. Consid- 1.0 wt% ering the stability as well as viscosity of the emulsion of 1.5 wt% 60% oil content, 2wt% surfactant can be used to prepare an 2.0 wt% efficient emulsion at 25 C. However, for lower tempera- 2.5 wt% tures, the surfactant concentration can also be less than 3.0 wt% 2wt%. 3.8 Size distribution of oil droplets in emulsions Droplet size distribution is one of the important parameters that influence the rheology as well as the stability of the emulsion. This parameter is greatly affected by oil/water 100 150 200 250 300 350 400 ratio, selection and concentration of surfactant and emul- Droplet size, nm sification technique. Several authors previously have reported that the use of ultrasonic waves leads to produc- Fig. 8 Droplet size distribution of emulsions as a function of tion of emulsion with relatively smaller dispersed phase surfactant concentration droplets than by a mechanical homogenizing method (Abismaı¨l et al. 1999; Lin and Chen 2006). Results of the volume droplet size distribution of O/W emulsions at resulted in a decrease in IFT between oil and water, which various oil content and surfactant concentration are plotted further reduced the surface free energy required to increase in Figs. 7 and 8, respectively. the interfacial area and allowed the easier production of Figure 7 shows that as the oil content of the emulsion smaller oil droplets. A decrease in oil droplet size resulted increased, the size of dispersed oil droplets in the emulsion in an increase in emulsion stability but also increased the decreased. The emulsion with 40% oil had droplet sizes in emulsion viscosity, as seen in stability and viscosity a range of 164–342 nm in diameter, whereas, when the oil results. Many authors previously have found the same content increased to 60%, the size range of droplets effects of droplet size on viscosity and stability of emul- decreased to 122–295 nm. From Fig. 8, it is clear that an sions (Kumar and Mahto 2016; Pal 1996; Zaki 1997). It increase in the surfactant concentration allowed the pro- was also noted that all the prepared emulsions had droplet duction of smaller oil droplets in the emulsion. The sizes less than 400 nm. emulsion with 1wt% surfactant had droplet sizes in a range of 164 to 396 nm, whereas, when the surfactant concen- tration increased up to 3wt%, the size of dispersed droplets 4 Conclusions tended to decrease to 105–255 nm. As been discussed previously, an increase in the surfactant concentration 1. Surfactant (TMSE) synthesized using sunflower oil was found to be a very effective emulsifying agent for preparation of O/W emulsions, and it may be consid- 40% ered for use in heavy oil transportation processes in 50% offshore. 55% 2. The emulsions prepared with TMSE were found to be 60% still flowing at even 1 C, which can be highly suitable for flow in cold environments. 3. Flow behaviour of heavy crude oil and most of the emulsions within the experimental range were non- Newtonian shear thinning. 4. Formation of an O/W emulsion caused a tremendous decrease in the viscosity of crude oil. All emulsions showed viscosity lower than 200 mPa s at 25 C and higher shear rate, which is adequate for flow in 100 150 200 250 300 350 offshore conditions. Droplet size, nm 5. Synthesized surfactant decreased the IFT between oil (diluted) and the aqueous phase by the order of tenfold Fig. 7 Droplet size distribution of emulsions as a function of oil and led to preparation of highly stable emulsions. content (2wt% surfactant) Droplet volume fraction, % Droplet volume fraction, % Pet. Sci. (2017) 14:372–382 381 rheology. J Colloid Interface Sci. 2006;297(2):785–91. doi:10. 6. Use of ultrasonic waves led to production of emulsions 1016/j.jcis.2005.10.069. with oil droplets size less than 400 nm, which Hafiz AA, Abdou MI. Synthesis and evaluation of polytri- promotes an increase in emulsion stability. ethanolamine monooleates for oil-based muds. J Surfactants 7. For this particular heavy crude oil, 60% oil content and Deterg. 2003;6(3):243–51. doi:10.1007/s11743-003-0268-z. Harrington KJ, D’Arcy-Evans C. Transesterification in situ of 2wt% surfactant concentration were found to be sunflower seed oil. Ind Eng Chem Prod Res. 1985;24(2):314– optimum values to produce a flowable and 8. doi:10.1021/i300018a027. stable O/W emulsion using the synthesized surfactant Jha NK, Jamal MS, Singh D, Prasad US. Characterization of crude oil at 25 C. For lower temperatures, a stable emulsion of upper Assam field for flow assurance. In: SPE Saudi Arabia section technical symposium and exhibition, 21–24 April, Al- can also be produced even at the surfactant concen- Khobar, Saudi Arabia; 2014. doi:10.2118/172226-MS. tration less that 2wt%. Jha PK, Mahto V, Saxena VK. Effects of carboxymethyl cellulose and tragacanth gum on the properties of emulsion-based drilling fluids. Can J Chem Eng. 2015;93(9):1577–87. doi:10.1002/cjce. Acknowledgements Authors would like to gratefully acknowledge the Indian Institute of Technology (Indian School of Mines), Dhanbad Johnsen EE, Rønningsen HP. Viscosity of ‘‘live’’ water-in-crude-oil for providing necessary laboratory facilities and financial support. emulsions: experimental work and validation of correlations. J Pet Sci Eng. 2003;38(1–2):23–36. doi:10.1016/S0920-4105(03) Open Access This article is distributed under the terms of the 00020-2. Creative Commons Attribution 4.0 International License (http://crea Jiang J, Mei Z, Xu J, Sun D. Effect of inorganic electrolytes on the tivecommons.org/licenses/by/4.0/), which permits unrestricted use, formation and the stability of water-in-oil (W/O) emulsions. distribution, and reproduction in any medium, provided you give Colloids Surf A Physicochem Eng Asp. 2013;429:82–90. doi:10. appropriate credit to the original author(s) and the source, provide a 1016/j.colsurfa.2013.03.039. link to the Creative Commons license, and indicate if changes were Kessick MA, Denis CES. Pipeline transportation of heavy crude oil. made. 1982. U.S. Patent No. 4,343,323. Kumar S, Mahto V. Emulsification of Indian heavy crude oil in water for its efficient transportation through offshore pipelines. Chem References Eng Res Des. 2016;115:34–43. doi:10.1016/j.cherd.2016.09.017. Langevin D, Poteau S, Henaut I, Argillier JF. Crude oil emulsion Abismaı¨l B, Canselier JP, Wilhelm AM, Delmas H, Gourdon C. properties and their application to heavy oil transportation. Oil Emulsification by ultrasound: drop size distribution and stability. Gas Sci Technol. 2004;59(5):511–21. Ultrason Sonochem. 1999;6(1–2):75–83. doi:10.1016/S1350- Lim JS, Wong SF, Law MC, Samyudia Y, Dol SS. A review on the 4177(98)00027-3. effects of emulsion on flow behaviours and common factors Ahmed NS, Nassar AM, Zaki NN, Gharieb HK. Formation of fluid affecting the stability of emulsion. J Appl Sci. heavy oil-in-water emulsions for pipeline transportation. Fuel. 2015;15(2):167–72. 1999;78(5):593–600. doi:10.1016/S0016-2361(98)00157-4. Lin C-Y, Chen L-W. Emulsification characteristics of three- and two- Alcazar-Vara LA, Buenrostro-Gonzalez E. Characterization of the phase emulsions prepared by the ultrasonic emulsification wax precipitation in Mexican crude oils. Fuel Process Technol. method. Fuel Process Technol. 2006;87(4):309–17. doi:10. 2011;92(12):2366–74. doi:10.1016/j.fuproc.2011.08.012. 1016/j.fuproc.2005.08.014. ASTM D1480-15. Standard test method for density and relative Liyana M, Nour A, Rizauddin D, Gimbun J, Nurdin S. Stabilization density (specific gravity) of viscous materials by Bingham and characterization of heavy crude oil-in-water (O/W) emul- pycnometer. 2015. doi:10.1520/D1480-15. sions. IJRET Int J Res Eng Technol. 2014;3(2):489–96. ASTM D4006-11. Standard test method for water in crude oil by Martı´nez-Palou R, Mosqueira ML, Zapata-Rendo´n B, Mar-Jua´rez E, distillation. 2011. doi:10.1520/D4006-11. Bernal-Huicochea C, Clavel-Lo´pez JC. Transportation of heavy ASTM D5853-11. Standard test method for pour point of crude oils. and extra-heavy crude oil by pipeline: a review. J Pet Sci Eng. 2011. doi: 10.1520/D5853-11. 2011;75(3–4):274–82. doi:10.1016/j.petrol.2010.11.020. Azodi M, Nazar ARS. Experimental design approach to investigate Pal R. Effect of droplet size on the rheology of emulsions. AIChE J. the effects of operating factors on the surface tension, viscosity, 1996;42(11):3181–90. doi:10.1002/aic.690421119. and stability of heavy crude oil-in-water emulsions. J Dispers Sci Pal R. Slippage during the flow of emulsions in rheometers. Colloids Technol. 2013a;34(2):273–82. doi:10.1080/01932691.2011. Surf A Physicochem Eng Asp. 2000;162(1–3):55–66. doi:10. 1016/S0927-7757(99)00239-3. Azodi M, Nazar ARS. An experimental study on factors affecting the Quiroga-Becerra H, Mejia-Miranda C, Laverde-Catano D, Hernan- heavy crude oil in water emulsions viscosity. J Pet Sci Eng. dez-Lopez M, Gomez-Sanchez M. A kinetic study of esterifica- 2013b;106:1–8. doi:10.1016/j.petrol.2013.04.002. tion of naphthenic acids from a Columbian heavy crude oil. Barnes HA. A review of the slip (wall depletion) of polymer CT&F Cienc Technol Futuro. 2012;4:21–32. solutions, emulsions and particle suspensions in viscometers: its Sharma S, Mahto V, Sharma VP. Effect of flow improvers on cause, character, and cure. J Nonnewton Fluid Mech. rheological and microscopic properties of Indian waxy crude oil. 1995;56(3):221–51. doi:10.1016/0377-0257(94)01282-M. Ind Eng Chem Res. 2014;53(12):4525–33. doi:10.1021/ Dantas Neto AA, Gomes EAS, Barros Neto EL, Dantas TNC, Moura ie403050y. CPAM. Determination of wax appearance temperature (WAT) in Zahirovic S, Lubansky AS, Yeow YL, Boger DV. Obtaining the paraffin/solvent systems by photoelectric signal and viscosime- steady shear rheological properties and apparent wall slip try. Braz J Pet Gas. 2009;3(4):149–57. velocity data of a water-in-oil emulsion from gap-dependent Dicharry C, Arla D, Sinquin A, Graciaa A, Bouriat P. Stability of parallel plate viscometry data. Rheol Acta. 2009;29:48(2):221–9. water/crude oil emulsions based on interfacial dilatational doi:10.1007/s00397-008-0343-7. 123 382 Pet. Sci. (2017) 14:372–382 Zaki NN. Surfactant stabilized crude oil-in-water emulsions for Zhao RB, Tang GQ, Kovscek AR. Modification of heavy-oil rheology pipeline transportation of viscous crude oils. Colloids Surf A via alkaline solutions. J Pet Sci Eng. 2013;103:41–50. doi:10. Physicochem Eng Asp. 1997;125(1):19–25. doi:10.1016/S0927- 1016/j.petrol.2013.02.009. 7757(96)03768-5. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Petroleum Science Springer Journals

Emulsification of Indian heavy crude oil using a novel surfactant for pipeline transportation

Kumar, Shailesh; Mahto, Vikas
Petroleum Science , Volume 14 (2) – Apr 12, 2017
Download PDF
11 pages

Loading next page...
 
/lp/springer-journals/emulsification-of-indian-heavy-crude-oil-using-a-novel-surfactant-for-SeoXhdrYUW

References (36)

Publisher
Springer Journals
Copyright
Copyright © 2017 by The Author(s)
Subject
Earth Sciences; Mineral Resources; Industrial Chemistry/Chemical Engineering; Industrial and Production Engineering; Energy Economics
ISSN
1672-5107
eISSN
1995-8226
DOI
10.1007/s12182-017-0153-6
Publisher site
See Article on Publisher Site

Abstract

Pet. Sci. (2017) 14:372–382 DOI 10.1007/s12182-017-0153-6 ORIGINAL PAPER Emulsification of Indian heavy crude oil using a novel surfactant for pipeline transportation 1 1 Shailesh Kumar Vikas Mahto Received: 1 June 2016 / Published online: 12 April 2017 The Author(s) 2017. This article is an open access publication Abstract The most economical way to overcome flow Keywords Heavy crude oil  Oil-in-water emulsion assurance problems associated with transportation of heavy Pipeline transportation  Sunflower oil  Rheology crude oil through offshore pipelines is by emulsifying it Stability with water in the presence of a suitable surfactant. In this research, a novel surfactant, tri-triethanolamine monosun- flower ester, was synthesized in the laboratory by extract- 1 Introduction ing fatty acids present in sunflower (Helianthus annuus) oil. Synthesized surfactant was used to prepare oil-in-water In past decades, a progressive decrease in conventional oil emulsions of a heavy crude oil from the western oil field of reserves has led to a dramatic increase in production of India. After emulsification, a dramatic decrease in pour heavy crude oil. However, transportation of such highly point as well as viscosity was observed. All the prepared viscous crude oil through pipelines is a major challenge for emulsions were found to be flowing even at 1 C. The petroleum industries especially in offshore conditions. emulsion developed with 60% oil content and 2wt% sur- Heavy crude oils have viscosities of more than 1000 mPa s factant showed a decrease in viscosity of 96%. The sta- at room temperature. However, viscosity of crude oil bility of the emulsion was investigated at different should be less than 200 mPa s at 15 C for its transporta- temperatures, and it was found to be highly stable. The tion through pipelines (Kessick and Denis 1982). The effectiveness of surfactant in emulsifying the heavy oil in flowability of crude oil at the pumping temperature is an water was investigated by measuring the equilibrium important factor that affects pipeline transportation. Heavy interfacial tension (IFT) between the crude oil (diluted) and crudes usually have higher pour points due to high content the aqueous phase along with zeta potential of emulsions. of high molecular weight components, such as waxes, 2wt% surfactant decreased IFT by almost nine times that of asphaltenes and resins. In conditions where the atmo- no surfactant. These results suggested that the synthesized spheric temperature is below the pour point, crude oil gels surfactant may be used to prepare a stable oil-in-water completely and causes severe transportation problems. emulsion for its transportation through offshore pipelines Especially in the cold offshore environment, waxes and efficiently. asphaltenes deposit over inner surfaces of pipelines and eventually clog the pipelines, which further increases the pumping cost. Therefore, several methods are employed by petroleum industries to transport crude oils through pipelines, dilu- & Vikas Mahto tion/blending of crude with lighter oil or organic solvents, vikas.ismpe@hotmail.com preheating of crude and subsequent heating of pipelines, Department of Petroleum Engineering, Indian Institute of use of pour point depressants (PPDs), application of drag Technology (Indian School of Mines), Dhanbad, Jharkhand, reducing additives and development of core annular flow India (CAF) and in situ oil upgrading (Martı´nez-Palou et al. 2011). However, each of these methods has economic, Edited by Yan-Hua Sun 123 Pet. Sci. (2017) 14:372–382 373 technical and logistical drawbacks when it comes to market in Kolkata, India. Polythene ethylene glycol (PEG) transportation of heavy crude oil through offshore pipe- and triethanolamine (TEA) were obtained from Loba lines. Another pipeline technique favourable for cold off- Chemie Pvt. Ltd. (Mumbai, India). n-heptane, n-decane, shore environments is the transportation of heavy crudes as toluene, HCl and chloroform were procured from Merck oil-in-water (O/W) emulsions. Specialties Pvt. Ltd. (Mumbai, India). Methanol, sodium Oil-in-water emulsions are thermodynamically unsta- chloride, sodium carbonate, acetone, p-toluene sulphonic ble dispersions of the oil phase in the water phase. They are acid, acetic acid, petroleum ether (40–60 C) and ace- subjected to several breakdown processes like flocculation, tonitrile were received from Avantor Performance Mate- coalescence, Ostwald ripening and creaming (Langevin rials India Ltd. (New Delhi, India). et al. 2004). In order to make these emulsions kinetically stable, a suitable surfactant (or mixture of surfactants) is 2.2 Synthesis of surfactant always added, which adsorbs at the oil/water interface and forms a strong interfacial film (Jiang et al. 2013). However, Hydrolysis of sunflower oil (SO) Sunflower oil (50 g) was a particular surfactant may not be suitable for different reacted with 10% NaOH solution (250 mL) at 150 C crude oils due to variation in physicochemical properties. under constant stirring (450 rpm) in a three-necked flask Fatty acids (FAs), derived from different vegetable oils, are along with gradual addition of water (400 mL) for 2 h. raw materials for preparation of surfactants through ester- After reaction, a hot solution of 30% HCl (150 mL) was ification or polymerization. Surfactants synthesized using added and the mixture was kept in a water bath at 80 C vegetable oils have various advantages. They are cheaper, until the oily layer became clear. The oily layer was then biodegradable and cause no adverse effect on nature. In separated and collected as hydrolysed sunflower oil (HSO), this study, we used sunflower oil to synthesize a novel a mixture of several free fatty acids. surfactant. Sunflower oil is a triglyceride obtained from Synthesis of tri-triethanolamine TEA (149 g) was con- pressing sunflower (Helianthus annuus) seeds. Alkaline densed in the presence of NaOH (1.6 g) as a catalyst. The hydrolysis of these triglycerides produces FAs and glyc- reaction was carried at 260 C under constant stirring erol. Fatty acids from sunflower oil consist of 6.8% pal- (450 rpm) in a three-necked flask until 36 g of water was mitic, 5.0% stearic, 19.6% oleic and 68.6% linoleic acids collected in a Dean and Stark trap. The used catalyst was (Harrington and D’Arcy-Evans 1985). Hydrolysed sun- then neutralized by washing the obtained product with 5% flower oil was esterified with a trimer of triethanolamine to acetic acid solution. To further wash out impurities, the develop a new surfactant as ester and further evaluated as product was dissolved in petroleum ether (b.p. 40–60 C) emulsifier for preparation of heavy oil-in-water emulsions. and an organic layer was separated. The remaining solvent The estimated cost of the synthesized surfactant is very low was distilled off using a Soxhlet apparatus to give tri-tri- as compared to the cost of commercial surfactants. Con- ethanolamine (TTEA) (Hafiz and Abdou 2003). sidering the economy, it is very important for petroleum Esterification of HSO and TTEA HSO (36 g) was reac- industries to maximize the oil content as well as minimize ted with TTEA (51 g) in the presence of a catalyst, p- the requirement of surfactant to prepare a stable emulsion toluene sulphonic acid (0.0108 g). The reaction was carried with acceptable viscosity and pour point. at 150 C with continuous stirring, and water was removed The objective of current research is to synthesize a azeotropically as it was formed. The product was then cheap natural surfactant from sunflower oil that is suit- washed with a hot solution of 5% Na CO to remove the 2 3 able for preparing an oil-in-water emulsion of an Indian catalyst and then dissolved in petroleum ether (b.p. heavy crude oil to facilitate its transportation through off- 40–60 C). After separating the organic layer, the solvent shore pipelines. Oil content and the amount of surfactant was distilled off to obtain purified tri-triethanolamine required were further optimized by investigating their monosunflower ester (TMSE) as a desired surfactant (Hafiz effect on pour point, viscosity, stability, droplet size dis- and Abdou 2003). Physical state of the surfactant is tribution, interfacial tension and zeta potential of the pre- semisolid at 25 C and brownish-black in colour. It has a pared emulsions. density of 1.102 gm/cm at 15 C. 2.3 Characterization of crude oil 2 Experimental Heavy crude oils are usually produced in the form of water- 2.1 Materials in-oil emulsion (Dicharry et al. 2006), so the initial water content in crude oil was measured using the Dean and Stark Heavy crude oil sample was collected from a Rajasthan oil method (ASTM D4006-11 2011). Water was then sepa- field, India. Sunflower oil was procured from a local rated with aid of a commercial demulsifier (PEG 200) and 123 374 Pet. Sci. (2017) 14:372–382 heating to obtain pure heavy crude oil. Further, the density measurement of rheology of the crude oil and prepared (ASTM D1480-15 2015) and pour point (ASTM D5853-11 emulsions, respectively. 2011) of the heavy crude oil were also determined using standard ASTM methods. SARA analysis was performed to 2.7 Measurement of emulsion stability characterize crude into four major components: saturates, aromatics, resins and asphaltenes (Jha et al. 2014). Wax Immediately after preparation of emulsions, each emulsion content was determined using the modified Universal Oil was transferred to three separate 10-mL glass tubes (0.1- Products (UOP) 46-64 method (Sharma et al. 2014), and mL graduation) and tightly stoppered with a glass lid. wax appearance temperature (WAT) was determined using These three separate groups of emulsion samples were then the viscosity method (Dantas Neto et al. 2009). kept at 15, 25 and 35 C to allow separation of water over time from these emulsion samples. The amount of water separated at the end of six days was noted and the emulsion 2.4 Preparation of emulsions stability was calculated using the following equation. An aqueous phase was first prepared by dissolving the S ¼ðÞ 1  V=V 100% ð1Þ surfactant in distilled water at 65 C. The heavy crude oil where S is the emulsion stability; V is the water volume in sample was preheated to 65 C to improve its fluidity the initial emulsion, mL; and V is the volume of water before adding it to the aqueous phase. Emulsions were then separated from the emulsion, mL. prepared using a Hielscher ultrasonic homogenizer with an UP200Ht processor at a working frequency of 26 kHz and 2.8 Interfacial tension and zeta potential 100% amplitude for a fixed irradiation time of 10 min. In measurements this study, the oil content was varied in the emulsion, keeping the volume of the surfactant constant (2wt%) with A Texas-500 spinning drop tensiometer (Data-Physics, respect to the total volume of the emulsion. Again for Model No: SVT 15 N) was used to measure interfacial specific series of experiments, at the optimized oil content, tension (IFT) between the oil and the aqueous phase at the surfactant concentration in the emulsion was varied to different surfactant concentrations at 25 C. Due to the obtain an optimum surfactant concentration. very high viscosity of the crude oil, it was impossible to inject a drop of oil using a microlitre syringe in the cap- 2.5 Fourier transform infrared (FT-IR) illary tube filled with the aqueous phase. Therefore, crude spectroscopy oil had to be diluted with n-decane (40% v/v) to make it flowable (Zhao et al. 2013). During measurement, the Infrared spectra of both crude oil and the synthesized capillary tube was rotated at 2000 rpm for 600 s to obtain surfactant were recorded using a Perkin-Elmer spectrum 2 equilibrium IFT values. spectrophotometer assisted by Spectrum-10 software to Zeta potential of emulsions was measured using a Zeta- analyse the functional groups present. Software collected Meter System 4.0 (Zeta-meter, INC., Staunton, VA) to spectra, in absorbance mode, in the spectral region of from study the charge properties of oil droplets in the emulsion -1 4000 to 400 cm . Further infrared spectra of emulsion at room temperature. To prepare samples for measurement, systems were also recorded to compare and analyse the 0.1 mL of each emulsion was diluted with 100 mL of functional groups. distilled water. At least five different particles of each sample were tracked to obtain the average value of zeta potential. 2.6 Measurement of pour point and rheology of the crude oil and emulsions 2.9 Measurements of oil droplet size and size distribution The main objective of the emulsification process is to decrease the pour point and enhance the flowability of the Size and distribution of oil droplets in prepared emulsions heavy crude oil. Pour points of emulsions were measured were determined using a Zetasizer Nano S90 particle size using the ASTM method (ASTM D5853-11 2011). The analyser procured from Malvern Instruments Ltd. at 25 C. rheological flow behaviour of crude oil and emulsions was Dynamic light scattering was conducted at a 90 scattering investigated at 25 C using a Bohlin Gemini 200 rheometer angle to measure particle sizes with this particle size (Gemini 200 software), supplied by Malvern instruments. analyser. This instrument analyses the diffusion of particles Cone-plate (25-mm plate diameter, 2.5 cone angle and moving under Brownian motion by measuring the scattered 70-lm gap) and parallel-plate (25-mm plate diameter at light intensity and converts this to size and a size two gaps, 750 and 500 lm) geometries were used for 123 Pet. Sci. (2017) 14:372–382 375 distribution using the Stokes–Einstein relationship. In order attributed to its high wax content. As reported, the crude oil to make the emulsion sample optically clear and to avoid was found to be highly asphaltinic in nature and very rich the effect of multiple scattering, 0.1 mL of emulsion was in the resin fraction, which makes crude oil heavier and diluted with 15 mL of distilled water. Tests were run three restricts its flowability. A very high fraction of saturates times, and the test duration was shortened to 10 s to avoid (66.5%) was present in crude oil, which provides an effect of coalescence of droplets during measurement. asphaltene-hostile environment and assists in deposition of asphaltenes (Alcazar-Vara and Buenrostro-Gonzalez 2011). 3 Results and discussion 3.2 Infrared spectroscopic analysis In the present investigation, a surfactant was synthesized by extracting free fatty acids from sunflower oil and FT-IR spectra of heavy crude oil, TMSE and O/W emul- evaluated as an emulsifier. Oil-in-water emulsions were sion are shown in Fig. 1, and the observed peaks with prepared to optimize oil content and surfactant concentra- associated functional groups are given in Table 2. Char- tion by investigating their effects on pour point, rheology acteristic peaks of alkyl groups (CH and CH ) due to 3 2 and stability of emulsions. Effects of droplet size distri- stretching vibration and bending vibration with strong -1 bution in emulsions on their viscosity and stability were absorbance at 2919, 2850 and 1462 cm were observed also examined along with discussion of interfacial prop- for heavy crude oil. Such high absorbance can be attributed erties, IFT and zeta potentials of emulsions at various to high contents of saturates and wax in heavy crude oil. -1 surfactant concentrations. Combination of the multiple bands around 1114 cm and -1 the band at 1736 cm confirms the presence of ester in the 3.1 Analysis of crude oil synthesized surfactant. Presence of aromatic nuclei observed in the crude oil may be due to the presence of The results of water content, API gravity, pour point, wax asphaltenes and resins (Quiroga-Becerra et al. 2012). Peaks -1 content, WAT and SARA analysis of crude oil are reported around 719 and 666 cm in heavy crude oil and TMSE, in Table 1. The Dean and Stark method confirmed the respectively, represent rocking vibration of the backbone of presence of a large amount (45%) of dispersed water in the carbon chains having six or more carbon atoms (Quiroga- crude oil (W/O emulsion) sample. API gravity of heavy Becerra et al. 2012). In spectra of the emulsion system, a -1 crude oil is 21.27, so it can be classified as heavy crude oil very strong and broad absorption band at 3443 cm was according to API convention. A large amount of wax is observed due to the presence of hydroxyl groups from H O present in heavy crude oil, which is a major factor in after formation of the O/W emulsion. The absorption bands resisting flow as these wax crystals start appearing at of alkyl groups were greatly weakened, suggesting the temperature around 55 C. These wax crystals grow at breaking of C–C bonds and shortening of C-chains thus further decreasing temperatures, start to precipitate and improving the flowability of heavy crude oil. Also the band -1 form a solid phase. A very high pour point (42 C) was due to rocking vibration of C-chains shifted to 495 cm observed for this particular heavy crude oil which can be that can also suggest that the number of C-atoms in the chain has been reduced due to emulsion formation. Table 1 Physicochemical properties of heavy crude oil 3.3 Depression in pour point Parameter Observed value Method Water content, % (v/v) 45 ASTM D4006-11 In order to avoid flow assurance problems in pipelines -3 under offshore conditions, the pour point of emulsions Density at 15 C, g cm 0.9254 ASTM D1480-15 should be very low. Ahmed et al. (1999) found the pour Specific gravity at 15 C 0.9262 ASTM D1480-15 point to be 6 and 9 C, respectively, for emulsions with oil API gravity at 15 C 21.27 content of 60% and 70%, respectively, when the pour point Pour point, C 42 ASTM D5853-11 of the crude oil was 18 C. Zaki (1997) also reported a Wax content, % (w/w) 11 Modified UOP 46-64 decrease in the pour point of crude oil from 13 to 7 C after WAT, C 55 Viscosimetry emulsification with 70% oil content. Pour point is a very SARA analysis, % (w/w) important flow parameter, and for all the prepared emul- Saturates 66.5 sions in our study, the measured pour point was found to be Aromatics 10.5 remarkably low compared to the pour point of heavy crude Resins 8.5 oil (42 C). All the emulsions prepared were flowing at Asphaltenes 6.5 even 1 C, which is highly suitable for offshore conditions. 123 376 Pet. Sci. (2017) 14:372–382 Crude oil O/W emulsion Surfactant 1650 916 2925 666 4000 3500 3000 2500 2000 1500 1000 500 -1 Wavelength, cm Fig. 1 FT-IR spectra of heavy crude oil, synthesized surfactant and prepared emulsion -1 Table 2 Wave number (cm ) a Functional group Type of vibration Crude oil Surfactant Emulsion for dominant peaks detected from FT-IR O–H in water Stretching – 3417 3443 =C–H in aromatics Stretching – 3010 – C–H in CH ,CH Asymmetric stretching 2919 2925 2917 3 2 C–H in CH ,CH Symmetric stretching 2850 2853 2849 3 2 C=C in alkene/aromatic nuclei Stretching 1606 1650 1632 Unsaturated C=C In-plane bending 1017 916 – C=O in ester Stretching – 1736 – C–O in ester Stretching – 1114 – C–H in CH ,CH Symmetric bending 1462, 1377 1409 1463 3 2 –(CH ) – Rocking 719 666 495 2 n Emulsion with 60% oil content and 2wt% surfactant 3.4 Rheological behaviour of heavy crude oil behaviour of the shear-thinning profile was observed for and prepared emulsions heavy crude oil. For parallel-plate measurements at two gaps, instead of coinciding, lower apparent viscosity values Flow behaviour of the heavy crude oil and emulsions was were observed at lower gap size (at 500-lm gap) for each investigated in a rate-controlled (CR) mode over a shear emulsion over the range of shear rate studied due to -1 rate range of 100–1000 s . The rheometer provided flow occurrence of the wall slip effect. However, all data points behaviour curves as both shear stress vs. shear rate and from both gaps appeared to fall close to a single curve, apparent viscosity vs. shear rate, along with respective indicating the slight possibility of wall slip. Apparent wall data. Figure 2 shows the rheological behaviour of heavy slip or wall depletion effects are observed for concentrated crude oil and prepared emulsions by varying the oil content emulsion systems in rheometers due to displacement of the at a constant surfactant concentration (2wt%), measured at dispersed phase away from the solid boundaries (walls), two gaps using parallel-plate geometry. Non-Newtonian and this displacement of the dispersed phase is caused due Transmittance, % Pet. Sci. (2017) 14:372–382 377 gap sizes are comparatively presented in Table 3 as the 100% -1 40% degree of viscosity reduction at 546 s shear rate. Up to 50% 50% oil content, emulsions showed close to Newtonian 55% behaviour, whereas, when the oil content further increased, 60% they started to behave as non-Newtonian shear-thinning 1 fluids. Shear-thinning behaviour suggests that the emulsion viscosity decreased as the pumping pressure increased. At -1 high shear rate (546 s ), the apparent viscosity of heavy 0.1 crude oil was found to be 5081 mPa s, whereas, after an emulsion was formed with 40% oil content, the emulsion viscosity reduced dramatically by 99.8% and reached 0.01 9.5 mPa s. Furthermore, an increase in the oil content led to an increase in the emulsion viscosity. At 60% oil con- 0 200 400 600 800 1000 -1 tent, the emulsion viscosity increased to 81.2 mPa s, where Shear rate, s the degree of viscosity reduction was around 98.4%. Fur- Fig. 2 Influence of oil content on the rheology of the emulsions at ther increase in the oil content led to an inversion of the 2wt% surfactant, measured at 25 C. Solid and dashed lines represent O/W emulsion into a W/O emulsion. From the results data at 750- and 500-lm gaps, respectively observed and considering the maximum throughput of oil through pipelines, it is clear that the optimum volume of oil to action of various physicochemical forces (Barnes 1995). was 60% for preparing a stable emulsion with The presence of wall slip poses a special problem while acceptable viscosity. measuring actual rheological properties of emulsions. At 60% oil content, the optimum amount of surfactant During rheological measurement of oil-in-water emulsions, required to stabilize emulsions with acceptable viscosity depletion of the oil phase with an increase in shear stress was determined by measuring the rheology of emulsions of leaves the low-viscosity liquid (continuous phase) adjacent various surfactant concentrations. Figure 3 shows the to the boundary; thus, viscosities observed in such condi- effect of surfactant concentration on the rheology of tions are much lower than the actual ones (Pal 2000). emulsions, measured at two gaps using the parallel-plate However, during pipeline transportation of emulsions, due geometry. Results obtained at both gap sizes are compar- to slip, dispersed particles will be displaced away (towards atively presented in Table 4, and results at 750 lm are centre, region of low shear) from the smooth solid wall of further discussed. As the surfactant concentration pipelines and facilitate the flow; therefore, estimation of decreased from 2wt% to 1wt%, the apparent viscosity of actual rheological properties of an emulsion is important emulsions also decreased. At 1wt% surfactant, the emul- for industries involved in pipeline transportation. Apart sion viscosity was reduced to approximately 99.3%. from the geometry and shear rate used for measurement, However, at higher concentrations (3wt% surfactant), the possibility of wall slip also depends on the size of dispersed emulsion viscosity was 98.6 mPa s, reduced by 98.0%. droplets in an emulsion. Lower dispersed droplet size les- This could be attributed to the fact that higher emulsifier sens the chances of occurrence of wall slip inside the concentration decreases the interfacial tension between oil rheometer (Barnes 1995). All emulsions studied in this and water, which leads to formation of smaller oil droplets. work possessed droplet sizes lower than 400 nm, discussed As a result of a decrease in droplet sizes, the number of in Sect. 3.8, which also suggests lower chances of wall slip. droplets contacting water surface increases which ulti- Zahirovic et al. (2009) utilized the parallel-plate mately increases the emulsion viscosity (Azodi and Nazar geometry at different gap sizes for very low apparent shear 2013b). It is not economical to use a large amount of -1 rate up to 1.0 s and the vane geometry for shear rate surfactant. On the other hand, stability of the emulsion at -1 further up to 100 s , in their study of ammonium nitrate- lower surfactant concentration is another important factor in-diesel oil emulsion. We have considered the high shear to choose an optimum concentration. rate in our study because in most crude oil transportation pipelines actual flow takes place at shear rates around 3.5 Interfacial tension analysis -1 500 s , where the shear rate near or on the pipe wall may be even higher (Azodi and Nazar 2013a; Johnsen and Surfactant effectiveness as an emulsifier is most impor- Rønningsen 2003). Since rheological measurement carried tantly evaluated by its ability to decrease the IFT between out at a bigger gap size is relatively less prone to wall slip crude oil and water. Figure 4 demonstrates the equilibrium (Pal 2000), results obtained at higher gap size (750 lm) are IFT values between heavy crude oil (diluted) and the further discussed here. However, results obtained at both aqueous phase at various surfactant concentrations. It was Apparent viscosity, Pa s 378 Pet. Sci. (2017) 14:372–382 -1 Table 3 Viscosity reduction in emulsions of different oil contents at two gap sizes and 546 s shear rate Oil content, % Parallel-plate geometry 750-lm gap 500-lm gap Apparent viscosity, mPa s Viscosity reduction, % Apparent viscosity, mPa s Viscosity reduction, % 60 81.2 98.4 75.4 98.5 55 57.2 98.9 48.3 99.0 50 19.4 99.6 12.4 99.7 40 9.5 99.8 7.9 99.8 Apparent viscosity of heavy crude oil is 5081 mPa s 1.3 -40 1.0 wt% IFT 1.2 1.5 wt% -45 Zeta potential 2.0 wt% 1.1 2.5 wt% 1.0 3.0 wt% 0.9 -55 0.8 0.1 0.7 0.6 -65 0.5 0.4 0.3 -75 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.01 Surfactant concentration, wt% 0 200 400 600 800 1000 -1 Shear rate, s Fig. 4 IFT between crude oil and the aqueous phase and zeta potential as a function of surfactant concentration Fig. 3 Influence of surfactant concentration on the rheology of emulsions of 60% oil content, measured at 25 C. Solid and dashed 0.5wt% surfactant addition. At 2wt% surfactant, the IFT lines represent data at 750- and 500-lm gaps, respectively value decreased to 0.69 mN/m, whereas at 3wt%, IFT reached to 0.37 mN/m. The decreased IFT value con- observed that with increasing surfactant concentration in tributed largely to a subsequent decrease in the drop size of the aqueous phase, IFT values decreased efficiently. IFT dispersed crude oil. As a result of decreased particle size between diluted crude and water with no surfactant was distribution, viscosity as well as the stability of the emul- around 6.15 mN/m and decreased to 1.10 mN/m after sion increased. -1 Table 4 Viscosity reduction in emulsions of different surfactant concentrations at two gap sizes and 546 s shear rate Surfactant concentration, wt% Parallel-plate geometry 750-lm gap 500-lm gap Apparent viscosity, mPa s Viscosity reduction, % Apparent viscosity, mPa s Viscosity reduction, % 1.0 34.4 99.3 28.9 99.4 1.5 46.1 99.1 45.8 99.1 2.0 81.2 98.4 75.4 98.5 2.5 56.2 98.9 55.9 98.9 3.0 98.6 98.0 82.8 98.4 Apparent viscosity of heavy crude oil is 5081 mPa s Apparent viscosity, Pa s ITF, mN/m Zeta potential, mV Pet. Sci. (2017) 14:372–382 379 3.6 Zeta potential analysis increases in both oil content as well as surfactant concen- tration led to an increase in the emulsion stability. On the The zeta potential measurement helps in predicting emul- other hand, temperature also played a very important role sion stability by predicting the tendency of the emulsion to in the emulsion stability. Emulsion samples kept at lower coalesce or flocculate. It characterizes distance between the temperatures showed higher stability than at higher tem- emulsion droplets by calculating the electric charge on the peratures. As the oil content in emulsion increased from surface of droplets. A higher absolute value of the zeta 40% to 60% at 2wt% surfactant, the emulsion stability potential (either negative or positive) is interpreted as increased from 51.7% to 85% at 35 C. When the tem- meaning there is higher charge on the droplets, which perature decreased from 35 to 15 C, the stability of the results in greater chances of them repelling each other and emulsion of 40% oil increased from 51.7% to 83.3% and avoiding coalescence and flocculation. A lesser charge on for the emulsion of oil content above 40%, 100% stability the droplets allows them to come closer and coalesce/ was achieved. The effect of temperature can be explained flocculate (Jha et al. 2015). Figure 4 summarizes the effect by the fact that a decrease in temperature leads to a on zeta potential of O/W emulsions with increasing sur- decrease in interfacial tension between oil and water. As a factant concentration. It was observed that the absolute result, the decrease in internal energy of the molecules may value of zeta potential increased from 44.3 to 71.2 mV as decrease the pressure required to induce the interfacial film the surfactant concentration increased from 1wt% to 3wt% thinning and ultimately increases the coalescence time in the emulsion. These results suggest that with an increase (Liyana et al. 2014). in the surfactant concentration, the charge concentration on The emulsions with 60% oil content were completely emulsion droplets also increased which led to production of stable at 15 C, despite variation in surfactant concentra- a stable emulsion. tion from 1wt% to 3wt%. However, when the temperature increased to 25 C, the stability of emulsion with 1wt% surfactant reduced to 82.5%, and furthermore reduced to 3.7 Stability of emulsions 70% at 35 C. Again, an increase in the stability at higher temperatures was achieved by increasing the surfactant Emulsion stability is a very important parameter which concentration. The emulsion with 3wt% surfactant was depends on factors like concentrations of oil/water and found to achieve stability around 95.0% and 92.5% at 25 their density difference, water phase viscosity, salinity and and 35 C, respectively. An increase in the surfactant pH, choice and amount of surfactant, size of dispersed oil concentration results in an increasing number of surfactant droplets, preparation method and duration and temperature molecules absorbed at the oil/water interface which pro- of homogenization (Lim et al. 2015). Based on water vides a barrier to the coalescence of dispersed oil droplets, separation observed after 6 days at different temperatures, thus stabilizing the emulsion (Zaki 1997). Additionally, the emulsion stability is plotted in Figs. 5 and 6, respec- application of ultrasonic waves causes formation of dro- tively, against variations in oil content and surfactant plets with smaller sizes, which increases the total interfa- concentration. It was observed from the results that cial area allowing more particle-to-particle interaction, and 15 °C 15 °C 25 °C 25 °C 35 °C 35 °C 40 45 50 55 60 1.0 1.5 2.0 2.5 3.0 Oil content, % Surfactant concentration, wt% Fig. 5 Emulsion stability as a function of oil content at different Fig. 6 Emulsion stability as a function of surfactant concentration at temperatures (2wt% surfactant) different temperatures (60% oil content) Emulsion stability, % Emulsion stability, % 380 Pet. Sci. (2017) 14:372–382 finally leads to enhancing the emulsion stability. Consid- 1.0 wt% ering the stability as well as viscosity of the emulsion of 1.5 wt% 60% oil content, 2wt% surfactant can be used to prepare an 2.0 wt% efficient emulsion at 25 C. However, for lower tempera- 2.5 wt% tures, the surfactant concentration can also be less than 3.0 wt% 2wt%. 3.8 Size distribution of oil droplets in emulsions Droplet size distribution is one of the important parameters that influence the rheology as well as the stability of the emulsion. This parameter is greatly affected by oil/water 100 150 200 250 300 350 400 ratio, selection and concentration of surfactant and emul- Droplet size, nm sification technique. Several authors previously have reported that the use of ultrasonic waves leads to produc- Fig. 8 Droplet size distribution of emulsions as a function of tion of emulsion with relatively smaller dispersed phase surfactant concentration droplets than by a mechanical homogenizing method (Abismaı¨l et al. 1999; Lin and Chen 2006). Results of the volume droplet size distribution of O/W emulsions at resulted in a decrease in IFT between oil and water, which various oil content and surfactant concentration are plotted further reduced the surface free energy required to increase in Figs. 7 and 8, respectively. the interfacial area and allowed the easier production of Figure 7 shows that as the oil content of the emulsion smaller oil droplets. A decrease in oil droplet size resulted increased, the size of dispersed oil droplets in the emulsion in an increase in emulsion stability but also increased the decreased. The emulsion with 40% oil had droplet sizes in emulsion viscosity, as seen in stability and viscosity a range of 164–342 nm in diameter, whereas, when the oil results. Many authors previously have found the same content increased to 60%, the size range of droplets effects of droplet size on viscosity and stability of emul- decreased to 122–295 nm. From Fig. 8, it is clear that an sions (Kumar and Mahto 2016; Pal 1996; Zaki 1997). It increase in the surfactant concentration allowed the pro- was also noted that all the prepared emulsions had droplet duction of smaller oil droplets in the emulsion. The sizes less than 400 nm. emulsion with 1wt% surfactant had droplet sizes in a range of 164 to 396 nm, whereas, when the surfactant concen- tration increased up to 3wt%, the size of dispersed droplets 4 Conclusions tended to decrease to 105–255 nm. As been discussed previously, an increase in the surfactant concentration 1. Surfactant (TMSE) synthesized using sunflower oil was found to be a very effective emulsifying agent for preparation of O/W emulsions, and it may be consid- 40% ered for use in heavy oil transportation processes in 50% offshore. 55% 2. The emulsions prepared with TMSE were found to be 60% still flowing at even 1 C, which can be highly suitable for flow in cold environments. 3. Flow behaviour of heavy crude oil and most of the emulsions within the experimental range were non- Newtonian shear thinning. 4. Formation of an O/W emulsion caused a tremendous decrease in the viscosity of crude oil. All emulsions showed viscosity lower than 200 mPa s at 25 C and higher shear rate, which is adequate for flow in 100 150 200 250 300 350 offshore conditions. Droplet size, nm 5. Synthesized surfactant decreased the IFT between oil (diluted) and the aqueous phase by the order of tenfold Fig. 7 Droplet size distribution of emulsions as a function of oil and led to preparation of highly stable emulsions. content (2wt% surfactant) Droplet volume fraction, % Droplet volume fraction, % Pet. Sci. (2017) 14:372–382 381 rheology. J Colloid Interface Sci. 2006;297(2):785–91. doi:10. 6. Use of ultrasonic waves led to production of emulsions 1016/j.jcis.2005.10.069. with oil droplets size less than 400 nm, which Hafiz AA, Abdou MI. Synthesis and evaluation of polytri- promotes an increase in emulsion stability. ethanolamine monooleates for oil-based muds. J Surfactants 7. For this particular heavy crude oil, 60% oil content and Deterg. 2003;6(3):243–51. doi:10.1007/s11743-003-0268-z. Harrington KJ, D’Arcy-Evans C. Transesterification in situ of 2wt% surfactant concentration were found to be sunflower seed oil. Ind Eng Chem Prod Res. 1985;24(2):314– optimum values to produce a flowable and 8. doi:10.1021/i300018a027. stable O/W emulsion using the synthesized surfactant Jha NK, Jamal MS, Singh D, Prasad US. Characterization of crude oil at 25 C. For lower temperatures, a stable emulsion of upper Assam field for flow assurance. In: SPE Saudi Arabia section technical symposium and exhibition, 21–24 April, Al- can also be produced even at the surfactant concen- Khobar, Saudi Arabia; 2014. doi:10.2118/172226-MS. tration less that 2wt%. Jha PK, Mahto V, Saxena VK. Effects of carboxymethyl cellulose and tragacanth gum on the properties of emulsion-based drilling fluids. Can J Chem Eng. 2015;93(9):1577–87. doi:10.1002/cjce. Acknowledgements Authors would like to gratefully acknowledge the Indian Institute of Technology (Indian School of Mines), Dhanbad Johnsen EE, Rønningsen HP. Viscosity of ‘‘live’’ water-in-crude-oil for providing necessary laboratory facilities and financial support. emulsions: experimental work and validation of correlations. J Pet Sci Eng. 2003;38(1–2):23–36. doi:10.1016/S0920-4105(03) Open Access This article is distributed under the terms of the 00020-2. Creative Commons Attribution 4.0 International License (http://crea Jiang J, Mei Z, Xu J, Sun D. Effect of inorganic electrolytes on the tivecommons.org/licenses/by/4.0/), which permits unrestricted use, formation and the stability of water-in-oil (W/O) emulsions. distribution, and reproduction in any medium, provided you give Colloids Surf A Physicochem Eng Asp. 2013;429:82–90. doi:10. appropriate credit to the original author(s) and the source, provide a 1016/j.colsurfa.2013.03.039. link to the Creative Commons license, and indicate if changes were Kessick MA, Denis CES. Pipeline transportation of heavy crude oil. made. 1982. U.S. Patent No. 4,343,323. Kumar S, Mahto V. Emulsification of Indian heavy crude oil in water for its efficient transportation through offshore pipelines. Chem References Eng Res Des. 2016;115:34–43. doi:10.1016/j.cherd.2016.09.017. Langevin D, Poteau S, Henaut I, Argillier JF. Crude oil emulsion Abismaı¨l B, Canselier JP, Wilhelm AM, Delmas H, Gourdon C. properties and their application to heavy oil transportation. Oil Emulsification by ultrasound: drop size distribution and stability. Gas Sci Technol. 2004;59(5):511–21. Ultrason Sonochem. 1999;6(1–2):75–83. doi:10.1016/S1350- Lim JS, Wong SF, Law MC, Samyudia Y, Dol SS. A review on the 4177(98)00027-3. effects of emulsion on flow behaviours and common factors Ahmed NS, Nassar AM, Zaki NN, Gharieb HK. Formation of fluid affecting the stability of emulsion. J Appl Sci. heavy oil-in-water emulsions for pipeline transportation. Fuel. 2015;15(2):167–72. 1999;78(5):593–600. doi:10.1016/S0016-2361(98)00157-4. Lin C-Y, Chen L-W. Emulsification characteristics of three- and two- Alcazar-Vara LA, Buenrostro-Gonzalez E. Characterization of the phase emulsions prepared by the ultrasonic emulsification wax precipitation in Mexican crude oils. Fuel Process Technol. method. Fuel Process Technol. 2006;87(4):309–17. doi:10. 2011;92(12):2366–74. doi:10.1016/j.fuproc.2011.08.012. 1016/j.fuproc.2005.08.014. ASTM D1480-15. Standard test method for density and relative Liyana M, Nour A, Rizauddin D, Gimbun J, Nurdin S. Stabilization density (specific gravity) of viscous materials by Bingham and characterization of heavy crude oil-in-water (O/W) emul- pycnometer. 2015. doi:10.1520/D1480-15. sions. IJRET Int J Res Eng Technol. 2014;3(2):489–96. ASTM D4006-11. Standard test method for water in crude oil by Martı´nez-Palou R, Mosqueira ML, Zapata-Rendo´n B, Mar-Jua´rez E, distillation. 2011. doi:10.1520/D4006-11. Bernal-Huicochea C, Clavel-Lo´pez JC. Transportation of heavy ASTM D5853-11. Standard test method for pour point of crude oils. and extra-heavy crude oil by pipeline: a review. J Pet Sci Eng. 2011. doi: 10.1520/D5853-11. 2011;75(3–4):274–82. doi:10.1016/j.petrol.2010.11.020. Azodi M, Nazar ARS. Experimental design approach to investigate Pal R. Effect of droplet size on the rheology of emulsions. AIChE J. the effects of operating factors on the surface tension, viscosity, 1996;42(11):3181–90. doi:10.1002/aic.690421119. and stability of heavy crude oil-in-water emulsions. J Dispers Sci Pal R. Slippage during the flow of emulsions in rheometers. Colloids Technol. 2013a;34(2):273–82. doi:10.1080/01932691.2011. Surf A Physicochem Eng Asp. 2000;162(1–3):55–66. doi:10. 1016/S0927-7757(99)00239-3. Azodi M, Nazar ARS. An experimental study on factors affecting the Quiroga-Becerra H, Mejia-Miranda C, Laverde-Catano D, Hernan- heavy crude oil in water emulsions viscosity. J Pet Sci Eng. dez-Lopez M, Gomez-Sanchez M. A kinetic study of esterifica- 2013b;106:1–8. doi:10.1016/j.petrol.2013.04.002. tion of naphthenic acids from a Columbian heavy crude oil. Barnes HA. A review of the slip (wall depletion) of polymer CT&F Cienc Technol Futuro. 2012;4:21–32. solutions, emulsions and particle suspensions in viscometers: its Sharma S, Mahto V, Sharma VP. Effect of flow improvers on cause, character, and cure. J Nonnewton Fluid Mech. rheological and microscopic properties of Indian waxy crude oil. 1995;56(3):221–51. doi:10.1016/0377-0257(94)01282-M. Ind Eng Chem Res. 2014;53(12):4525–33. doi:10.1021/ Dantas Neto AA, Gomes EAS, Barros Neto EL, Dantas TNC, Moura ie403050y. CPAM. Determination of wax appearance temperature (WAT) in Zahirovic S, Lubansky AS, Yeow YL, Boger DV. Obtaining the paraffin/solvent systems by photoelectric signal and viscosime- steady shear rheological properties and apparent wall slip try. Braz J Pet Gas. 2009;3(4):149–57. velocity data of a water-in-oil emulsion from gap-dependent Dicharry C, Arla D, Sinquin A, Graciaa A, Bouriat P. Stability of parallel plate viscometry data. Rheol Acta. 2009;29:48(2):221–9. water/crude oil emulsions based on interfacial dilatational doi:10.1007/s00397-008-0343-7. 123 382 Pet. Sci. (2017) 14:372–382 Zaki NN. Surfactant stabilized crude oil-in-water emulsions for Zhao RB, Tang GQ, Kovscek AR. Modification of heavy-oil rheology pipeline transportation of viscous crude oils. Colloids Surf A via alkaline solutions. J Pet Sci Eng. 2013;103:41–50. doi:10. Physicochem Eng Asp. 1997;125(1):19–25. doi:10.1016/S0927- 1016/j.petrol.2013.02.009. 7757(96)03768-5.

Journal

Petroleum Science – Springer Journals

Published: Apr 12, 2017

There are no references for this article.