This paper considers anionic and nonionic surfactants, as candidates for crude oil production by enhancement applications. In this study some colloidal properties of surfactants were tested by conventional and new test methods. The oil in water type emulsions have great importance in the petroleum industry. The stability of crude oil in water emulsions are investigated in a wide range of physical and chemical circumstances. Investigations at 10 bar are needed to get knowledges on the real conditions of the given petroleum exploration processes. A special glass cell was used for the tests of the mixtures various crude oil-water emulsions under hydrocarbon gas atmosphere and for the oil disclapement efficiency. Based on the experimental results it was found that emulsifying capacity was changed significantly by the real process conditions. The decrease of the density of hydrocarbon phase was contributed to the overall reduction in the efficiency of emulsifiers also occurred. Based on the experimented data it is supported to pay more attention to apply the real test conditions or approximate the real values

Bartha, László

Elekes, Andrea

Nagy, Roland

Vágó, Árpád

English

Periodica Polytechnica (Budapest University of Technology and Economics)

508|https://doi.org/10.3311/PPch.12342Creative Commons Attribution bPeriodica Polytechnica Chemical Engineering, 63(3), pp. 508–512, 2019Cite this article as: Elekes, A., Nagy, R., Bartha, L., Vágó, Á. "Comparative Study on Surfactants Mixtures in Aqueous Solution at Atmospheric Pressure and 10 bar Reservoir Atmosphere", Periodica Polytechnica Chemical Engineering, 63(3), pp. 508–512, 2019. https://doi.org/10.3311/PPch.12342Comparative Study on Surfactants Mixtures in Aqueous Solution at Atmospheric Pressure and 10 bar Reservoir AtmosphereAndrea Elekes1*, Roland Nagy1, László Bartha2, Árpád Vágó31 Department of MOL Department of Hydrocarbon and Coal Processing, Faculty of Engineering, University of Pannonia, H-8200 Veszprém, Egyetem str. 10., Hungary2 Department of Department of Chemical Engineering Science, Faculty of Engineering, University of Pannonia, H-8200 Veszprém, Egyetem str. 10., Hungary3 MOL Plc., Research & Development Division, H-1117 Budapest, Október huszonharmadika str. 18, Hungary* Corresponding author, e-mail: elekesa@almos.uni-pannon.huReceived: 03 April 2018, Accepted: 21 August 2018, Published online: 12 November 2018AbstractThis paper considers anionic and nonionic surfactants, as candidates for crude oil production by enhancement applications. In this study some colloidal properties of surfactants were tested by conventional and new test methods. The oil in water type emulsions have great importance in the petroleum industry. The stability of crude oil in water emulsions are investigated in a wide range of physical and chemical circumstances. Investigations at 10 bar are needed to get knowledges on the real conditions of the given petroleum exploration processes. A special glass cell was used for the tests of the mixtures various crude oil-water emulsions under hydrocarbon gas atmosphere and for the oil disclapement efficiency. Based on the experimental results it was found that emulsifying capacity was changed significantly by the real process conditions. The decrease of the density of hydrocarbon phase was contributed to the overall reduction in the efficiency of emulsifiers also occurred. Based on the experimented data it is supported to pay more attention to apply the real test conditions or approximate the real values.Keywordsatmospheric pressure and 10 bar, crude oil, surfactant, emulsifying capacity, oil displacement efficiency1 IntroductionCrude oil is one of the most actively traded commodities in the world. Worldwide demand for crude oil has been steadily intensifying over the past 20 years, as world demand for crude has grown from 60 to 84 million barrels per day [1, 2]. In parallel with the rapid growth of energy demand the quantity of economically exploitable crude oil is contin-uously decreasing [3]. In order to further improve of the oil recovery efficiency the chemical enhanced oil recovery methods were developed [4]. Our research was dealt with the examination of emul-sions which may occur during enhancement of petroleum exploitation [5, 6]. In this process, the aqueous solution and the crude oil mixture get various stable emulsions. The oil in water type emulsions have great importance in the petroleum industry. The emulsification behavior of a crude oil-water system is greatly depends on the compo-sitions of a crude oil [7]. The formation of emulsions is common during the pro-duction and transportation process of crude oil, which can greatly affect the flow characteristics of multiphase flow [2, 8-10]. We published our first part of the work on the emulsification behaviors of crude-oil-water system. The natural surfactants in the crude oil, such as asphaltenes, resins, and acidic compounds etc., reducing the interfacial tension of oil-water and forming an interfacial film with certain mechanical strength, that plays a key role in the emulsion formation and stabilization. Therefore, the differences in compositions of crude oils may result in large difference in the emulsification behaviors [11]. The environmentally friendly and bio-degradable vegetable oil based nonionic surfactants are used in the petroleum and petrochemical industry in many areas. The investigations under high-pressure can provide useful Elekes et al.Period. Polytech. Chem. Eng., 63(3), pp. 508–512, 2019|509information many industrial applications of surfactants implemented into the petroleum processing [12]. In this study the emulsion stability of the crude oil-wa-ter type emulsions were investigated both at the atmo-spheric and relatively high (10 bar) pressure conditions. Our aim is to present a test method to better approximate the actual conditions in the oil storage tank. The complex selection method of the surfactants can be supported by the described method. In addition, we investigate that, in the case of two different types of crude oil, the relationship between the emulsifying capacity and the oil displacement effect of each of the surfactant compositions.2 Materials For the preparation of emulsions the commercial surfac-tants (SPAN and LES marked) were used. The nonionic surfactants type materials were tech-nical grades of sorbitan monolaurate, monopalmitate, monostearate and mono-oleate, respectively, Span 20, 40, 60 and 80 used as received. The sodium lauryl ether sulfate (LES) is an important anionic surfactant used generally in many household and personal care products.The composition of the surfactant mixtures used for the experiments were 50w/w% nonionic and 50 w/w% anionic surfactant all mixtures.The surfactant mixtures were marked with M-1, M-2, M-3 and M-4.2.1 Preparation of model brine The synthetic brine was prepared, which contained 0.5 g/l NaCl, 0.2 g/l CaCl2⋅2H2O, 2.6 g/l NaHCO3 and 2.6 g/l CH3COONa⋅2H2O. There salts were dissolved in distilled water for the preparation of model brine [13].2.2 Preparation of the model hydrocarbon mixture Exactly 60 cm3 of n-heptane was mixed with 40 cm3 of toluene in a 250 cm3 conical flask. Before mixing, 0.1 g of 50/70 penetration grade bitumen was dissolved in 40 cm3 toluene. To prepare 0.05 % concentration of bitumen, 0.05 g of bitumen was dissolved in 40 cm3 of toluene and was made up to 100 cm3 with heptane, since bitumen are sol-uble in toluene [14].2.3 Crude oil The tests were performed with Hungarian paraffinic type crude oil and brine to compare model and real conditions. Anionic and non-ionic surfactants were used to reduce oil-water interfacial tension. The main properties of crude oil from South-East Hungary and model hydrocarbon mixture (model oil) were used as shown in Table 1.2.4 Preparation of emulsions Crude oil emulsions were prepared by dispersing 10 cm3 of model brine in 10 cm3 model hydrocarbon mixture or crude oil sample by using a mechanical shaker at speed of 500 rpm for 10 min. The emulsion portion was dis-pensed into a 20 cm3 measuring cylinder and its volume was recorded. Also the separation of the emulsion was also monitored at different time interval to determine the stability of the emulsion.3 Methods 3.1 Investigation of emulsifying capacity on high pressure The scheme of the special glass cell produced for the tests of the mixtures various crude oil-water emulsions under hydro-carbon gas atmosphere is shown in the Fig. 1. The high-pres-sure glass cell was used for simulation of the crude oil-water type emulsion storage in hydrocarbon atmosphere.Table 2 shows the composition of the reservoir gas used for the stability test of emulsions. Table 1 Properties of crude oil and model oilProperties Crude oil Model oilDensity, g/cm3 (20°C) 0.830 0.760Dynamic viscosity, mPa.s (20°C) 14.6 0.53Acid number, mg KOH/g 0.91 0.47Watson characterization factor 13.2 11.5Character of crude oil Paraffinic NaphthenicFig. 1 High-pressure glass cell for testing of the phase stability of emulsions510|Elekes et al.Period. Polytech. Chem. Eng., 63(3), pp. 508–512, 20193.2 Determination of the emulsifying capacity The stability of emulsions was assessed by monitoring the increase with the storage time the position of clear water-emulsion interface. The emulsion was allowed to stand in 20 cm3 measuring cylinder that the volume of water and hydrocarbon phase separation was recorded to evaluate the stability of the emulsions [15].3.3 Oil displacement efficiencyThe practical determination of the surface activity method has not been reported in the specific publications, which could be the extent to porous surfaces characterized by washing efficiency of the oil. It was developed a method for oil flushing effect, that based on the foundations of thin layer chromatography of organic chemical analysis has been used. The first step of the test procedure is the preparation of the thin layer. Then 4 µl of crude oil should be spotted on the thin layer at 2 cm from the base of the glass slab. Then the sample should be run in the emulsifier mixture at 80˚C for 3 hours. The oil displacement efficiency (ODE) of the surfactant composition can be evaluated by the distance from the centre of the oil spot to the upper edge of the spot measured in mm. The maximum difference between the parallel results was in the interval of ±10% [16].4 Results and discussion The emulsions were investigated according to the internal standard method and at atmospheric pressure. Furthermore the effects of emulsifiers were examined by influence of gas pressure from South-Hungary reservoir. The phase ratios of the resulting emulsions were read after one hour, 4 hours and after 24 hours at 80°C. The next step the phase ratios of the resulting emulsions were read after 1 hour, 4 hours and after 24 hours at 80 °C. Upper phase can contain crude oil or crude oil in the form of water in crude oil type emulsion (W/O). The mid-dle phase can be crude oil in water emulsion (W/O). The preferred emulsion type of enhancement of petroleum exploitation is the crude oil in water emulsion.4.1 Atmospheric emulsifying capacity at 80°CThe Fig. 2 and Fig. 3 displays the phase separation of sur-factant solution containing real crude oil–water type and model crude oil-water type emulsions.Based on measurements it was found that there were different in the volume of emulsion phases when using model and real oil. The emulsions phases were more stable in the case of emulsions contained model crude oil than the real crude oil. It was found that the volumes of middle emulsion phases were decreased over time. Mixture M-1. had the highest emulsifying capac-ity at atmospheric pressure. The largest middle phase (40 V/V%) was in the sample M-1 from a model crude oil after 4 hours of storage. Emulsions from real oil separated almost completely after 4 hours settling time.4.2 High pressure emulsifying capacity at 10 bar reservoir gas and 80°CThe high-pressure glass cell (Fig. 1) was used for sim-ulation of the crude oil/water type emulsion storage in hydrocarbon atmosphere. Fig. 4 and Fig. 5 shows the Table 2 Composition of the reservoir gasComponent Concentration, v/v%*Methane 82.7Ethane 9.1Propane 5.1Butane 3.1*applied method: GCFig. 2 Phase ratio of crude oil-water emulsions at 80°C and atmospheric pressureFig. 3 Phase ratio of model oil-water emulsions at 80°C and atmospheric pressureElekes et al.Period. Polytech. Chem. Eng., 63(3), pp. 508–512, 2019|511phase separation of surfactant solution containing real crude oil–water and model crude oil-water emulsions at a pressure of 10 bar.Based on the results of the emulsifying capacity tests at a pressure of 10 bar it was found that the sign M-1 and M-2 surfactant mixtures were the most effective for 24 hours. However the M-4 emulsion separated totally after 1 hour already.The viscosity of emulsions changed due to reservoir gas dissolving therefore the value of the emulsifying capac-ity also changed. Since the stability of emulsions has improved, so there is no correlation between the results at the atmospheric and higher pressure. However, correlation can be observed between emul-sion stability and the surfactant sructure. Contrary to the literature, the mixture containing the shorter chain surfac-tant had an emulsifying effect better than that of the lon-ger chain. This effect is due to the synergistic effect of the anionic and nonionic surfactants.Overall we found higher amount of middle phases resulted by tests at higher pressure.4.3 Oil displacement efficiencyAnother important property of the surfactants is the deter-gency. Fig. 6 shows the oil displacement efficiency of sur-factants in aqueous solution at atmospheric and 10 bar.Fig. 7 shows the oil displacement efficiency of surfac-tant aqueous solution at model crude oil.The oil displacement efficiency was different at differ-ent pressures and other crude oils. The sign M-1 surfactant mixture was the most effec-tive regarding the oil displacement efficiency both atmo-spheric and at 10 bar pressures. In most cases it was found that the higher pressure and the lighter model oil is advantageous to removing crude oil from rock.5 ConclusionEmulsions were prepared by using synthetic and real brine, synthetic and real crude oil and surfactants and examined by atmospheric and 10 bar pressure conditions. It was found that emulsifying effect was changed signifi-cantly by the real conditions. In the most cases it was observed that higher amount of middle phase related to the emulsifying capacity was resulted in the tests at higher pressures. Furthermore the higher pressure seemed to be advantageous to remove the crude oil from rock. Fig. 4 Phase ratio of crude oil-water emulsions at 80°C and 10 barFig. 5 Phase ratio of model oil-water emulsions at 80°C and 10 barFig. 6 Oil displacement efficiency of surfactant aqueous solution at 80°C, atmospheric and at 10 bar (real crude oil)Fig. 7 Oil displacement efficiency of surfactant aqueous solution at 80°C, atmospheric and at 10 bar (model crude oil)512|Elekes et al.Period. Polytech. Chem. Eng., 63(3), pp. 508–512, 2019Among the tested surfactants mixtures containing SPAN-20 and SPAN-40 surfactants had the most stable emulsions and the best oil displacement efficiency. This effect is due to the synergistic effect of the anionic and nonionic surfactants.Because of the differences in the surfactant effects at high pressure it was suggested to supplement the complex selection system of the surfactants with the described method.References [1] Hasan, S. W., Ghannam, M. T., Esmail, N. 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Comparative Study on Surfactants Mixtures in Aqueous Solution at Atmospheric Pressure and 10 bar Reservoir Atmosphere

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Comparative Study on Surfactants Mixtures in Aqueous Solution at Atmospheric Pressure and 10 bar Reservoir Atmosphere

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