Study On Changes Rule Of Crude Oil Composition And Gas Composition By Air Low Temperature Oxidation

Air injection is a new technology for improved oil recovery. Air and crude oil can occur low temperature oxidation(LTO) at the oil reservoir temperature(over 70℃generally),.Most of oxygen is consumed and some of carbon dioxide, carbon monoxide and methane are produced to achieve a nitrogen flood or flue gas flood by LTO reactions. The oil composition and gas composition are changed and the properties of crude oil also are changed by LTO reactions. If crude oil can be driven is related with the composition and chemical properties of crude oil. It is important for the study about the oil composition and the gas composition. Oil reservoir that is low permeability light oil reservoir in our project fits to exploit by air injection LTO. The reservoir temperature is 90℃～110℃.In this thesis IR heater is adopted for the LTO experiments of oil alone and oil saturated core at the different temperature and pressure. The changes of pressure are recorded during LTO experiments, the oil composition and the gas composition are analyzed. Then we can draw a conclusion on the law of changes of the oil composition and the gas composition, and we can provide reliable basis for the test of oil field.The contents of the thesis mainly consist of several sections:(1) LTO experiment of oil alone: Air and oil (without core) occur LTO reactions at reservoir temperature. The results demonstrate that the gas composition is changed by LTO,O₂ content decreases,CO₂ content and CH₄ content increase a little, the oil composition is also changed by LTO, the saturates content is unchanged, the aromatics content decreases, the resins content increases, the asphaltenes content is unchanged. The viscosity of oil increases by LTO.(2) LTO experiment of oil saturated core: Simulating reservoir conditions. we carry out LTO experiment of oil saturated quartz sand or crushed reservoir core in some oil saturation. The results demonstrate that core and pressure can affect LTO reactions. For core, during the LTO experiment of crushed reservoir core ,more O₂ is consumed, and more CO₂ and CH₄ are produced than the experiment of quartz sand; More saturates and aromatics participate in LTO reactions and more resins and asphaltenes are produced; The extent of oil oxidation raises. There are some catalytic agents promote LTO reactions in reservoir core. For pressure, more O₂ is consumed and more oil are oxidized if the initial pressure of the experiment is higher.(3)Temperature experiment of oil oxidation: Air and oil occur oxidation reactions at the different temperatures. The results demonstrate that the saturates content and aromatics content decrease gradually, the resins content and asphaltenes content increase gradually with the rise of the experiment temperature; Most of O₂ is consumed and some CO₂ and CH₄ are produced at the different temperatures; The viscosity of oil increases by oxidation reactions.