Study On Maintaining Dispersive State Of Heavy Oil Asphaltene By Chemical Method

Heavy oil reserves are abundant,but its exploitation faces many challenges.Due to the high viscosity of heavy oil,it is necessary to resort to certain means during the exploitation,coupled with the change of external factors,which will lead to the asphaltene instability and aggregation in heavy oil.The asphaltene content of heavy oil is higher than that of conventional crude oil,so the asphaltene aggregation problems encountered during heavy oil exploitation will be more serious.Chemical methods are the most effective way to reduce,remedy,and prevent asphaltene deposition during oil and gas production and pipeline transportation.In this paper,the heavy oil in a western oil field is taken as an example,and four aspects are studied.Firstly,analyze the physical and chemical properties of the asphaltine isolated from the heavy oil and the plugging material taken back from the oil field,and to summarize the formation reasons of the plugging material.Secondly,screen the dispersant with the best performance.The method to evaluate the dispersant performance is to obtain the dispersion ability index by absorbance method.Comparing asphaltene deposition amount by asphaltene dispersion test.Micrographs of asphaltene aggregates in capillaries were captured using a microscope equipped with microscopic camera,and the particle size and particle size distribution of asphaltene aggregates were calculated using Toupview software.Thirdly,compare the differences between the new solvent and xylene in the asphaltene solubility performance.Matlab software is used to simulate the Hansen solubility sphere model of asphaltene and solvent and solve the solubility parameters.Fourthly,asphaltene dispersion system is developed and the behavior of asphaltene aggregates under dynamic conditions is studied by using microfluidic device.The results show that the poor stability of heavy oil is one reason for the formation of asphaltene plug,and the other reason is the influence of external factors,including temperature,pressure,gas-oil ratio,flow rate and solid particles.The best dispersant for asphaltene dispersion of heavy oil in this oilfield is a kind of biomass alkylphenol,namely cashew phenol.Cashew phenol can increase the stability of asphaltene,reduce the deposition of asphaltene,and reduce the size of asphaltene aggregates in microporous media.Cashew phenol can disperse asphaltenes because of the high aromaticity of asphaltenes in the structure of benzene ring,which contains polar groups of phenolic hydroxyl groups and alkyl side chains of carbon dioxane.The new asphaltene solvent is limonene,which not only has little difference with xylene in asphaltene solubility,but also comes from plants,and has a better application prospect because of its safety and environmental protection characteristics.Hansen solubility parameters of limonene and asphaltene were measured and the solubility spheres of limonene and asphaltene were simulated.The results show that the compatibility between limonene and asphaltene is about 90%.In order to play the synergistic effect of the two,the optimized dispersion system ADS-1 formula by orthogonal experiment was m(limonene): m(oil-soluble resin): m(auxiliary agent): m(cashew phenol)= 0.6: 0.1: 0.05: 1.Compared with the use of dispersants and solvents alone,ADS-1 has better performance in dissolving asphaltene,stabilizing asphaltene,reducing asphaltene precipitation and controlling asphaltene aggregate size.