| With the development of world economy, there is a growing demand for energy, while the amount of recoverable conventional crude oil and its production is declining; therefore, making full use of heavy oil has become a worldwide irreversible trend. The characteristics of high viscosity and waxy of heavy oil lead to its poor mobility, which brings great difficulties to pipeline and limits its exploitation and transportation.This restraint has become increasingly prominent in China. To solve these problems above, many countries in the world use the technology of pour point depression and viscosity reduction according to the characteristics of heavy oil, but the original technology can not meet the current needs. As a result, to develop a new technology of pour point depression and viscosity reduction has been a forefront and hot issue that the international area for research on oil field chemicals concerns.Based on the summary and exploration of the mechanism of pour point depression and viscosity reduction, the author used molecular dynamics simulation methods to design the the molecular of heavy oil viscosity reducer, and used solution polymerization to synthesize Dodecyl Methacrylate-Styrene-maleic acidAnd methyl octadecyl acrylate-styrene-maleic anhydride, the Heavy copolymer viscosity reducer. The author discussed ester monomer's preparation conditions, and studied polymerization temperature, initiator dosage, catalyst dosage, the ratio of reactants and other conditions on the properties of the polymer viscosity. Taken the heavy oil of Sheng li Oil Field as study sample, the author studied the synthesis and viscosity reduction properties of long-chain ester methacrylate copolymer viscosity reducer.The findings are as follows:(1) According to the characteristics of "resin and asphaltene molecular structure of the surface pile of overlapping binding force for the hydrogen bond, and the distinction and diversity of hydrogen bonds that Constitute such a binding", and the principles of molecular design "carboxyl hydrogen bonding force is stronger than hydrogen bonding in the hydroxy", in the design of heavy oil viscosity reducer molecular, we should synthesize and choose hydrogen bond strength that is greater than or less than the original form of glial, asphaltene molecular structure of the surface pile of overlapping hydrogen bonding, and special assembly materials that can adsorbe on the resin and asphaltene molecules prior to others. Then let the special assembly materials combine with the resin and asphaltene molecules, while the other side of the special assembly with non-polar hydrogen won't combine with it, therefore, break or to improve the resin and asphaltene molecular plane pile of overlapping structures, which is the direction of the design of heavy oil viscosity reducer molecular.(2) By the contrast of the simulation of four different architectures, I found that interaction occurred between polar groups of and and glial of viscosity reducer molecular and aroups in the asphaltene, and they combined together. At the same time, it can be seen clearly that the thermodynamic and kinetic data of crude oil changed after adding viscosity reducer. Because polymer viscosity contained maleic anhydride functional groups, which is hydrolyzed and generated carboxyl after adding heavy oil. The carboxyl and resin as well as asphaltene produced a strong association of carboxyl-type hydrogen bonding, and as a result, it changed the structure of the original heavy oil and develops toward the direction in favor oflower viscosity. But the long-chain ester methacrylate copolymer should be the focus of the synthesis of heavy oil viscosity reducer, who's the polymer molecular weight and degree of esterification should be at 1×1004～5×104 for a 95% and 90% range.(3) In the preparation of dodecyl methacrylate and octadecyl methacrylate, the best parameters is:toluene as solvent for the transesterification reaction; Molar ratio of higher alcohols and acrylic acid isl.5:1; the amount of catalyst is 1.0% of the total reactants; the amount of hydroquinone inhibitor accounts for 0.6% of the total reactant; reaction temperature 120℃; reaction time 6h; acrylic yield more than90%. FTIR analysis on the product structure showed that the product was methyl acrylate and that there were no other by-products within it on the whole.(4) Taking twelve methacrylate esters, styrene and maleic anhydride asmonomer, azobisisobutyronitrile as initiator and by using radical solution polymerization in toluene synthesized twelve methacrylate ester copolymer heavy viscosity reducer. The experiment showed that under the conditions of the amount of initiator 1.0%, reaction temperature 80℃-9℃, and reaction time 6 hours, molar ratio of monomers of dodecyl methacrylate:styrene:maleic anhydride 7:1:2, which constitute the optimal conditions for the polymerization. Under the conditions of molar ratio of monomers of dodecyl methacrylate: styrene:maleic anhydride 6:2:3, Initiator dosage 1.2%, In toluene at 90℃for 6h's reaction, the yield of the polymer could be more than 94.7%, FTIR analysis showed that three monomers copolymerized and generated much pure copolymer.(5) By using solution polymerization, the author researched polymerization technology of dodecyl methacrylate copolymer and finished the test of viscosity reducing effect to Sheng li heavy oil. The result showed that when the dosage of viscosity reducer was 800ppm, the effect of viscosity reduction attained the best. At the same time, it can be seen that the heavy oil which was adding 800ppm viscosity reducer, whose viscosity-temperature curve have undergone significant changes in contrast to that without viscosity reducer. At 35℃to 50℃, after adding 800×10-6 viscosity reducer, the viscosity-temperature curve of crude oil tis bacically150 mPa·s smooth curve, Especially at 35℃1 the apparent viscosity of crude oil declined from 315mPa·s to 150 mPa·s after the process of viscosity reduction of crude oil processed, viscosity reduction rate reached to52.38%. It can be seen that Dodecyl Methacrylate based ternary heavy oil viscosity reducer has a good effect to Sheng li heavy oil.(6) For the methyl octadecyl ester copolymer system:all the monomer ratio, initiator dosage, reaction temperature and reaction time affect the yield of octadecyl methacrylate copolymer system, also strongly affect the viscosity reducing effect. The yield and viscosity of the effect of showing a linear relationship. After comprehensive comparison and optimization. Optimal parameters of octadecyl methacrylate-based copolymer system was finally set: molar ratio of three monomers is 6:2:3; appropriate dosage of initiator was 1.2%; reaction temperature was 90℃; reaction time was 6 hours. Viscosity reduction rate increased rapidly with the increasing dosage of viscosity reducer, but when the dosage reach to a certain amount, viscosity reducing effect increase slowly, and finally, viscosity reduction rate decrease with the increasing concentration of viscosity reducer. The reason may be related to viscosity reducer's polymer solubility in heavy oil. For the Sheng li heavy oil, it has been tested that when the dosage was 500μg·g-1, the viscosity reduction rate reached to 74.3%.These results aboveindicate that as a viscosity reducer for heavy oil, Long-chain ester methacrylate copolymer has a potential value of industrial applications. |
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