Study On The Low-temperature-oxidation Kinetics And Characteristics Of JiQi Heavy Oil

As one of the most important energy around the world,petroleum resource is closely related to our country’s economy.However,conventional oil and gas resource are facing shortages with continuous exploitation.On the country,the proportion of proven reserves of heavy oil is getting bigger.It is the key point of sustainable development that how to exploit the heavy oil resource environmentally and efficiently.However,it is hard to exploit the heavy oil resource with the conventional method because of its high viscosity and poor liquidity.In recent years,"In situ combustion" has become one of the most mainstream method to for heavy oil exploitation.It can not only exploit heavy oil effectively,but also avoid environmental pollution,which is in line with the new ideas of sustainable development advocated by the international community.However,this enhanced oil recovery technology started late,and the main research is focused on the high-temperature oxidation stage.There are few studies on the characteristics of the low-temperature oxidation stage of heavy oil,and there are many controversies in related theories.Therefore,it is necessary to carry out relevant research on the characteristics of the low-temperature oxidation stage of heavy oil.Firstly,the research and application status of the air flooding of heavy oil domestically and abroad were investigated,and the research ideas and work contents of this paper were determined.Subsequently,the kinetic characteristics of heavy oil were studied by TG-DSC.The effect of heating rate and quartz sand/cuttings on the thermal behavior of heavy oil was analyzed.The results showed:Heavy oil oxidation is divided into three stages:low temperature oxidation(LTO),fuel deposition(FD)and high temperature oxidation(HTO).The increase of heating rate will increase the temperature range,reduce the mass loss,and increase the activation energy of low temperature oxidation stage.Quartz sand/cuttings can promote the low-temperature oxidation of heavy oil.The promotion of cuttings on low-temperature oxidation of heavy oil mainly comes from the clay minerals.Based on the kinetic analysis,the reaction process of low-temperature oxidation of heavy oil was studied using thermostatic static oxidation experiments combined with gas chromatography,infrared spectroscopy,and group composition analysis.The results showed that the low temperature oxidation of heavy oil was mainly divided into two reactions:oxygenation and bond breaking reaction.At the same time,the sensitivity analysis of factors affecting low temperature oxidation was performed.The effect of quartz sand/cuttings,gas injection volume,pressure,and temperature on the low-temperature oxidation of heavy oil was investigated by analyzing the produced gas phase and the changes of heavy oil group composition.The results show that under the experimental conditions,the effect of temperature on the low temperature oxidation of heavy oil is the most significant;On the basis of sensitivity analysis,the heavy oil after oxidation of different temperature was selected for coke content analysis,thermogravimetric analysis,electron microscope scanning,and flammability.The analysis shows that the increase of temperature can promote the deposition of coke.When the temperature is 160℃,the coke content in the heavy oil after oxidation can reach about 35%.After the oxidation,the activation energy of the heavy oil is increased compared to the original heavy oil at low temperature oxidation stage.The activation energy of the high temperature oxidation stage is reduced and more heat is released.After the oxidation,there are more loose irregular particles on the surface of the heavy oil,and the coke is porous like "honeycomb",which has a large surface area that can increase contact area with air to make it easier to burnFinally,an adiabatic low-temperature oxidation experiment of heavy oil was conducted by using a "high-temperature and high-pressure thermal tracking compensation system" developed by the laboratory.The effect of the initial temperature,quartz sand/cuttings and the ratio of medium to heat release of low-temperature oxidation of heavy oil were studied.Based on the above tests,an adiabatic low-temperature oxidation experiment of dynamic injection of heavy oil was carried out.The results showed that the increase of initial temperature and the specific surface area of the medium and the addition of quartz sand/cuttings can promote the heat release of low-temperature oxidation of heavy oil.Although spontaneous combustion was not detected during the dynamic adiabatic oxidation process,the amount of heat released was substantially higher than static adiabatic oxidation.This article has gained some understanding on the low-temperature oxidation kinetics and low-temperature oxidation characteristics of heavy oil,which will promote the development of related theories of heavy oil oxidation,and provide certain reference value and guiding significance for the field application of heavy oil air injection.