Study On High-Temperature-Resistant Emulsion Viscosity Reducing Agent System For Marine Heavy Oil

Since heavy oil reserves are abundant in our country,exploitation and utilization of heavy oil has a great significance in solving the shortage of petroleum resources.Heavy oils have high viscosity,poor fluidity,and difficulties to exploitation.Therefore,multiple oil recovery methods are often adopted in heavy oil production.Commonly used methods are steam flooding injection and emulsion viscosity reduction combination of oil recovery methods,it’s required that emulsion viscosity have better temperature resistance.Therefore,it is important to development of high temperature emulsified viscosity reducer for heavy oil extraction.Currently,emulsified viscosity reducer has the characteristics of strongly selectivity and narrowly application.However,the nature of this phenomenon is not well understood.This paper attempts to explore this issue from the relationship between the composition of heavy oil and emulsified viscosity reduction.The Guantao and the LD2-2 heavy oils are used as raw materials.The research methods include fraction four components separation,elemental,nuclear magnetic and infrared spectra,interfacial tension between oil and water,and particle size of oil-in-water droplets.It was found that the content and structure of asphaltene is a main factors affecting emulsion viscosity reduction of heavy oil studied,and heavy oil with high asphaltene aromatic content is difficult to emulsify.This paper is belonged to laboratory test,using marine heavy oil as raw material,twenty-one kinds of surfactants with different ion types were subjected to emulsification and viscosity-reducing primary election;then,according to the characteristics of each ion,binary compounding and performance evaluation were carried out according to different proportions.Finally,found to meet the requirements of temperature-resistant emulsifying viscosity reducer formulations:AB2.The formula can maintain the viscosity-reducing performance unchanged after being treated at350℃for 12h;it can withstand a salinity value of 66000 mg/L,among that the Ca²⁺content is 6000 mg/L,it has good resistance to temperature and salt.After the 350°C treatment,the viscosity reduction rate of heavy oil reached 99%when the dosage was only 270ppm（0.09%wt）,and dehydration rate reached 80%when rest 1h.The stability of emulsion is important to the exploitation,transportation and processing of heavy oil.In this paper,the effects of salinity,pH value,temperature,concentration,oil-water ratio and other factors on the stability of emulsion were studied.The relationship between interfacial tension,Zeta potential and emulsion stability was also discussed.The results show that:the addition of salt is beneficial to the stability of the emulsion;the emulsion tends to be unstable first and then unstable with the increase of salinity;the emulsion is the most stable when the salinity is55000mg/L,When the interfacial tension reached a minimum of 7.74×10^-2mN/m.Emulsions are more stable in the alkaline range than in the acidic range,it’s consistent with the higher acid content of the oil sample.As the dosage of the formula decreases,the emulsion gradually becomes unstable.The temperature has less effect on the emulsion;it is directly related to the formulation of temperature resistant emulsified viscosity reducer.As the ratio of oil to water decreases,the emulsion gradually becomes unstable.By measuring the interfacial tension and Zeta potential of oil and water,the interfacial tension is an important factor to evaluate the stability of emulsion,The greater the interface tension,the higher the interface Gibbs free energy of the system and the poorer the stability of the system.Zeta potential is not necessarily the decisive factor to evaluate the stability of emulsion.