Stable water-in-oil emulsions are produced in oil exploitation and cause many environmental and operational issues. In this paper, a co-polymer demulsifier is reported in detail; an emulsion polymerization method is used to prepare nano-P (MMA-AA-EA) with MMA, AA and EA as the monomers, DVB as the cross-linker and APS as the initiator. The resulting products are characterized by FT-IR. Furthermore, the surface tension and particles size analysis is investigated. The results show that the surface tension reduction is 10.66 mN/m at 20°C when the concentration of co-polymer is 1000 ppm and the average size is 76.99 nm. Moreover, the HLB of polymer is discussed specifically by changing the amount of AA. With the increase of AA, the HLB value of the polymer is increased accordingly. Besides, the demulsification performance of the co-polymer is also evaluated at different synthesis and demulsification conditions. It is showed that the maximum demulsification efficiency is 96% at 70°C for 60 min. The optimum concentration of demulsifier is 400 ppm when the amounts of AA and DVB are 1.4 g and 0.1 g, respectively. At last, the process of demulsification is showed under a microscope; the coalescence process of water droplets is indicated under the action of the demulsifier.
Enhanced oil recovery (EOR) using water injection is gradually getting mature in most of the oilfields worldwide. Although water and crude oil are two immiscible phases, highly stable water-in-oil (W/O) emulsions are likely to be produced due to the presence of interfacially active materials and fine solid particles accompanying with shear [
Chemical demulsification is a technique in which the film-thinning rate is enhanced and emulsion stability is lowered by using some chemicals called demulsifiers. According to their chemical structures and their applications, chemical demulsifiers will be classified into three different categories: polymeric surfactant, ionic liquids and nanoparticles [
In this paper, poly (methyl methacrylate-ethyl acrylate-acrylic acid) demulsifier was synthesized by emulsion polymerization. The optimum demulsification condition was performed to investigate the demulsifier performance. In detail, the influence of HLB and cross-linker of polymer on demulsification were discussed. Furthermore, optical microscope was used investigated demulsification process.
Methyl methacrylate (MMA), Methyl acrylate (EA), and Acrylic acid (AA), (AR grade) bought from National Chemicals Co., Ltd., are kept in brown bottles and stored in a refrigerator at below 5˚C. Ammonium persulfate (APS), divinylbenzene (DVB), methylbenzene all are bought from Tianli Chemicals Co., Ltd (Tianjing, China). Sodium alkylphenol ether sulfosuccinate (MS-1) and po1yoxyethylene octylphenol ether (OP-10) are supplied by Hainan Petrochemical Company (Jiangsu, China).
An emulsion polymerization method is used to prepare P (MMA-AA-EA) with MMA, AA and EA as the monomers, DVB as the cross-linker and APS as the initiator. First of all, 0.20 g MS-1 and 0.20 g OP-10 are added to 70 g deionized water in a 250 mL three-mouth flask which is properly assembled for heating under reflux, dropping funnel, thermometer. Afterwards, the flask is heated to 75˚C, 10 mL APS initiator solution is gradually added into the flask which is prepared by dissolving 0.2 g APS into 20 mL deionized water. Subsequently, the mixture of 0.5 g EA, 8.0 g MAA, and a certain amount of AA and DVB are dropped into flask with a constant pressure funnel. Finally, the reaction temperature is maintained at 75˚C for 3 h, and then gradually cooled to room temperature. And the correspond products is purified by using deionized water and vacuum freeze-drying.
Crude oil is supplied by Block115 in Fushan Oilfield. And the physical analysis of the crude oil was shown in
Viscosity/(mPa∙s−1) | Freezing point/˚C | Asphaltene/% | Colloid/% | Microcrystalline wax/% | S/% | Water content/% |
---|---|---|---|---|---|---|
200.4 | 25 | 16.5 | 9.3 | 16.8 | 0.12 | 1.56 |
The demulsification performance test is evaluated according to SY/t5281-2000 (Industrial standard). The polymer is dissolved in an organic solvent and prepared into a demulsifier solution with concentration of 10 g/L. The test is carried out in 25 ml graduated prescription bottles. Firstly, an amount of demulsifier is added into 20 mL of emulsion, and then the bottles are shaken vigorously 200 times by hand within 2 minutes. Afterward, the bottles are immediately returned into the as-settled water bath. The demulsifying efficiency is measured by calculating the amount of water removed from the emulsion sample.
D E = C o − C d C o × 100 % (1)
where Co is initial water concentration before water separation, Cd is water concentration after water separation.
The infrared spectrometer is equipped with a 15 cm optical path and a ZnSe gas pool. The scanning spectrum range is 4000 - 400 cm−1. Each sample is scanned by mid-infrared DTG detector for 16 times. The samples are made by KBr compression. The IR spectra of the copolymer are shown in
The surface tension of the polymer is tested by hanging piece methods (platinum plate size: 19.9 mm × 10 mm × 0.2 mm, accuracy: 0.01 mN/m) at 20˚C. The sample is synthesized by using 1.4 g AA, 8.0 g MMA and 0.5 g EA as monomers. The relationship of surface tension and concentration of P (MMA-AA-EA) is shown in
The size of the polymer is tested at Malvern nano ZS laser particle size analyzer at 25˚C. The particle size distribution of P (MMA-AA-EA) is shown in
When the amount of AA is 1.4 g, different amount of demulsifiers are added into the W/O emulsion at 70˚C. The results are shown in
The demulsification of different amount of polymers in W/O emulsion is shown in
It is shown in
The demulsifying performance of polymer in W/O emulsion is tested by using the same synthesis conditions with different amount of AA at 70˚C under the concentration of 400 ppm. It indicates that the demulsification efficiency is influenced by the different amount of AA (
The HLB of the emulsifier is the most important parameter, which shows its simultaneous attraction to oil and water [
Alsabagh et al. pointed out that the HLB value was estimated by:
w ( HLB ) = 20 [ m ( MH ) m ( MH ) + m ( ML ) ] (2)
where m(MH) is formula weight of the hydrophilic portion of the molecules and m(ML) is the formula weight of the lipophilic (hydrophobic) portion of the molecules [
The w(HLB) of the polymer of different amount of AA is shown in
Weight/g | mole/mol | w(HLB)/1 | ||||
---|---|---|---|---|---|---|
AA | MMA | EA | AA | MMA | EA | |
0.6 | 8 | 0.5 | 0.0083 | 0.08 | 0.005 | 1.78 |
1.0 | 8 | 0.5 | 0.0139 | 0.08 | 0.005 | 2.81 |
1.4 | 8 | 0.5 | 0.0194 | 0.08 | 0.005 | 3.72 |
1.8 | 8 | 0.5 | 0.0250 | 0.08 | 0.005 | 4.55 |
The solubility of the polymer in an oily solvent is also adjusted while improving the attractiveness of the polymer to the aqueous phase of the W/O emulsion droplets.
When HLB is low, the system is difficult to form the sharp interface separation. Similarly, when HLB is too high, too much of demulsifier is dissolved in the water phase leading to the reduction of oil/water separation ability. Therefore, the two different trends will inevitably result in the best suitable HLB.
The effect of different amount of cross-linkers on the demulsifying performance of polymer in W/O emulsion is investigated at 70˚C. Four kinds of polymers with different amount of cross-linker are obtained by using 0 g, 0.1 g, 0.2 g and 0.3 g cross-linkers respectively. The demulsification performance of polymers is shown in
Polymers of 300 ppm are added into W/O emulsion at 70˚C for 10 minutes. A drop of the emulsion is magnified 100 times under the microscope. The bright spot in the picture is the water phase. Pictures of the emulsion are taken every two minutes three times. It is shown in
A drop of emulsion with demulsifier of 300 ppm is magnified 100 times under the microscope. It is heated at 70˚C for 5, 10, 15 and 20 min, respectively. As it is shown in
1) In summary, a fast and efficient way is reported to separate water from W/O emulsion by using nano-P (MMA-AA-EA) as a demulsifier. It is found that 96% water is removed from the W/O emulsion within 60 min under the optimal conditions. The optimal reaction conditions are as follows: the amount of AA is 1.4 g; the amount of cross-linker is 0.1 g. And the demulsification conditions are as follows: the temperature is 70˚C; the amount of demulsifier is 400 ppm.
2) The surface tension reduction is 10.66 mN/m at 20˚C when the concentration of copolymer is 1000 ppm and the average size is 76.99 nm.
3) The process of demulsification is observed under a microscope. It is believed that a coalescence process of water droplets is taken place when the polymer is added into the W/O emulsion.
This study is supported by the Open Project Program of State Key Laboratory of Petroleum Pollution Control (Grant No. PPC2016006), CNPC Research Institute of Safety and Environmental Technology.
The authors declare no conflicts of interest regarding the publication of this paper.
Jiang, X., Huang, Z.M., Mi, Y.Z., Kuang, J.Z. and Ye, F. (2019) Emulsion Polymerization of P (MMA-AA-EA) and Its Demulsifying Performance in Water/Oil Emulsion. Open Journal of Yangtze Gas and Oil, 4, 212-224. https://doi.org/10.4236/ojogas.2019.43016