Research On Microwave-assisted Thermochemical Demulsification And Dehydration Of Aged Oil In Liuhua Oilfield

In recent years,various chemical measures of increasing oil production were successively applied with the major oil fields of China,which entering into the middle and later of development and achieving sustainable energy development,which lead to a change in chemical and physical properties of ground produced fluids,formed considerable amount of stably emulsification aged crude oil.Aged oil brought the various problems which restricted normal production,including the decrease of crude oil production,the increase cost of treatment,the unqualified of separation water,and environmental pollution.It is great significance to develop demulsification treatment technology of aged oil for solving three major problems,those are the increased of production,cost reduction and environmental protection.Through comparative analysis of physical properties,emulsion form and interfacial film strength,Zeta electric potential between CNOOC Liuhua oilfield aged oil and crude oil,the results showed that the density,viscosity,acid number,mechanical impurity content of the aged oil were higher than those of normal crude oil,and same to the strength and electrical properties of interfacial film.Meanwhile,there was a blurred boundary between mutual wrapped oil and water phases,the water droplets size was uniform and large distance between each other.These changes made aged oil more stability and difficult to dehydration.Thermo-chemical method was used for the dehydration of aged oil,and separated by centrifuge.The screening experiment results showed that the effect of the existing demulsifiers was all poor.Based on the physical properties of aged oil,SP169 and AE16 were modified to the polysiloxane polyether demulsifiers by two-step process,and the optimum conditions were obtained.The demulsification performance of polysiloxane polyether demulsifiers was evaluated,and the optimum conditions of demulsification were obtained by univariate optimization and orthogonal experiments.Under these conditions,the dehydration rate of aging oil reached to 86.87%which was significantly higher than other types of demulsifiers,also increased by 30%compared to the unmodification SP169 and AE16.The results of the comparative analysis for the demulsification mechanism of polysiloxane polyether demulsifiers,SP169 and AE16 with QCM-D showed that the adsorption and diffusivity properties of polysiloxane polyether demulsifiers on the oil-water interface were superior to SP169 and AE16,and therefore they could quickly adsorb,diffuse and fill vacancy parts in water interfacial film,reduced the interfacial tension,improved the drainage property of the interfacial film,and then released droplets.Microwave radiation was used to study the demulsification of aged oil and separated by centrifuge,and the optimum conditions of demulsification were obtained by univariate optimization and orthogonal experiments,under these conditions,the highest rate of dehydration of aging oil reached to 76.82%,and oil-water interface was tidy after breaking,and the separation water was clear.In addition,the test found that the strength and Zeta potential of the interfacial film of oil-water considerably reduced compared with the undemulsified aged oil,which confirmed that the microwave demulsification was the result of thermal effects and athermal effects.The demulsification and dehydration of aged oil by Microwave combined with thermo-chemical method were discussed in thermochemical-microwave radiation,microwave radiation-thermochermical,and microwave thermochemical.The results of thermochemical-microwave radiation experiments showed that the highest rate of microwave radiation on the remaining aging oil was 10.94%after thermochemical pretreatment,and the total value for two-step process was reached to 88.31%.The results of microwave radiation-thermochemical experiments suggested that the biggest value for thermochemical acted on remaining aged oil was 58.86%after pretreatmenting by thermo-chemical method.However,it took to a long time to demulsification and dehydration,and required centrifugation speed,so the total rate for two-step process was 90.46%.The maximum dehydration rate of microwave thermochemical method was 94.05%at the follwing conditions:microwave radiation power was 406 W,irradiation time was 4 min,the demulsifier content was 125 mg/L,centrifugal velocity was 4000 r/min,and centrifugal time was 10 min.In addition,the microwave thermochemical method also had the follwing significant advantages:the less demulsification and centrifugal time,the less demulsifier content,low centrifugal velocity,the trim oil-water interface and the clear separation water.