Study On Reaction Mechanism Of Hydrogenous Catalytic Pyrolysis Modified Superheavy Oil For In-Situ Combustion

In-situ combustion is an important method to enhance oil recovery,and has obvious advantages compared with other technologies.It involves injecting air to the reservoir,generating a series of oxidation reactions at different temperature ranges by chemical interaction between oil and oxygen.The oxidation reaction can release a large amount of heat;the oxygen reacts with a coke like material formed by thermal cracking,they are responsible of generating the heat necessary to sustain and propagate the combustion front,sweeping the heavy oil and upgrading it due to the high temperatures.In the synergy of heat and other driving forces,the purpose of enhanced oil recovery is achieved.However,failures often occur due to the complex reaction mechanism,and therefore have not been widely used.In general,the combustion process consists of a low temperature oxidation stage,a fuel deposition stage,and a high temperature oxidation stage.One of the key factor of success for in-situ combustion is the amount of fuel consumption.it may result in bad combustion and failure to maintain the continuous combustion of the combustion front when the amount of fuel is too low.When the amount of fuel is higher,the amount of oxygen consumed is increased,a large amount of air needs to be injected,and the operating cost is increased.Therefore,cost saving is also one of factors to be considered.In view of the problems existing in the in-situ combustion,different catalysts and hydrogen donors were used to study the in-situ combustion process.Using thermal analysis technology,crude oil is mixed with catalysts and hydrogen donors,and then mixed with simulated sand to form oil sands for thermal analysis.The combustion process is divided into4 stages by TG/DTG and DSC curves.In the low-temperature oxidation stage,the heat release of the oil sands is very low,and the heat release during the high-temperature oxidation stage is huge,mainly relying on the heat of the high-temperature oxidation stage for displacement.The kinetic parameters of each stage were studied using the conversion method of FOW and the Kissinger method.It was found that after the catalyst was added,the activation energy of the fuel deposition stage decreased during the low-temperature oxidation stage,and the activation energy of the high-temperature oxidation stage did not decrease significantly.After adding the catalyst and the hydrogen donor,the activation energy in the fuel deposition stage is greatly reduced,and the activation energy in the high-temperature oxidation stage is slightly reduced.After addition of catalysts and hydrogen donors,the heat release at the low temperature oxidation stage increases.The temperature range of each reaction stage of the oil sand moves to the low temperature area.The pyrolysis of crude oil in porous media undergoes three overlapping stages:distillation,visbreaking and coking.The expressions that control the rate of the two crackingreactions are derived and a technique is outlined to obtain initial estimates of their parameters from experimental data.Distillation of crude oil at temperatures below 280 ? plays an important role in the formation of the nature and extent of the cracking reaction.It was found that the operating pressure and the heating rate of the sand oil sample only affected the fuel formation process through the influence on the distillation.At the same time,catalysts and hydrogen donors have a significant impact on the combustion frontal speed and recovery.