Research On The Characteristics And Thermal Effects Of Oxidation Reactions Of Heavy Oil During In-situ Combustion

In-situ combustion?ISC?is one of the technologies of heavy oil thermal recovery.It has several advantages,such as high displacement efficiency,wide application range,high heat utilization rate,high quality of oil,etc.However,complex physical and chemical reactions and displacement mechanism are involved in the process of ISC,which result in unclear recognition on the oxidation characteristics of ISC.Also,the thermal effects during the oxidation process of ISC are difficult to be determined.Hence,the reasonable design of displacement schemes faces great challenges,limiting ISC`s application in oil field.Thus,in this paper,the oxidation characteristics of heavy oil during ISC process are systematically studied and the thermal effects are quantified accurately,whic h can provide a theoretical foundation for the successful application of ISC technology.Du 66 Shu 1-49-K028 heavy oil from Liao he oil field was selected as the feedstock.Firstly,the main properties of the feedstock were measured and the crude oil was ranked as ordinary heavy oil.Then the main properties of reaction products under the specific reaction conditions were measured and the characteristics of low and high temperature oxidation reactions were summarized.The mechanism of low temperature oxidat ion reaction and the kinetics of high temperature oxidation reaction were also investigated.On this basis,the influence of additives on the low and high temperature oxidation characteristics was discussed.Finally,the thermal effect of low and high temp erature oxidation reactions were determined by using Differential Scanning Calorimetry?DSC?.Low temperature oxidation reaction was studied at four kinds of different reaction conditions of 150°C,200°C,250°C and 300°C respectively.With the increasing of reaction temperature,the density and average molecular weight of heavy oil increase gradually.The viscosity of heavy oil increases at first and then decreases.The content of saturates and aromatics decrease gradually.O n the contrary,the content of asphaltenes increases gradually and the polymerization degree of aromatic rings increases dramatically.Tetralin,which has the structures of benzene and naphthenic,promotes low temperature oxidation reaction.It is inferred that the low temperature oxidation reaction follows the free radical reaction mechanism.Then DSC was carried out to calculate the heat of low temperature oxidation reaction,which is only 183.60 kJ/kg.High temperature oxidation reaction was studied at different reaction conditions.The reaction conditions have significant influences on the molar ratio of CO and CO ₂ in the gaseous products,the distribution of the different distillation liquid fractions and the element composition of petroleum coke.9,10-Dihydroanthracene could affect the high temperature oxidation reaction.The kinetics of high temperature oxidation reaction was studied by Friedman and Sharp methods.The obtained kinetics parameters by both methods are almost the same.Then,the heat of high temperature oxidation reactio n of coke was calculated by DSC,which is basically consistent with the theoretical calculation result.The reaction heat of petroleum coke is correlated well with the atomic ratio of H/C,presenting a logarithm correlation.The heat of high temperature oxidation reaction presents a theoretical maximum,which is 4.48×10⁴ kJ/kg.One-dimensional heat conduction model was explored initially during ISC.