Study On The Oxidation Characteristics Of Heavy Oil

Nowadays,more and more attention has been paid to the recovery of heavy oil resources as the conventional reserves decline significantly.The conventional mining technology is not suitable for heavy oil reservoir.In-situ combustion is an obvious advanced and favorable oil recovery technology with the advantage of high recovery ratio,low cost and wide reservoir adaption.But there are many problems in in-situ combustion technology,for instance,it is very difficult to judge combustion situation and monitor or control the combustion front. In-situ combustion is based on oxidation properties of heavy oil.It isrelated to the temperature field,gas injection,combustion rate and some other aspects.This study is conducted to explore the oxidation characteristics of heavy oil from Du-66 in Liaohe oilfield,in order to provide basic data and theoretical basis for the implementation of fire flooding.In this article,high temperature and pressure reaction system is designed.This reaction system is used to perform experiment of crude oil,light medium and heavy oil fraction under high(300℃) and low(90℃) temperature in different oxygen content atmosphere respectively.Temperature and pressure changes are recorded in the course of the experiment,and exhaust gas is collected to be analysed.The characteristers of oils before and after oxidation are analysed through infrared spectrum,SARA composition,element analysis,physical and chemical properies testing,gas chromatography.The conclusions on the law of the changes of the oil characteristers and the exhuast gas composition are as follows:The results demonstrate that saturated hydrocarbon is 29.78%,aromatic 28.13%,resin 35.68% and asphaltene component 6.14% in Du-66 heavy oil.Three main reaction intervals were observed on thermograms known as low temperature oxidation(LTO) fuel deposition(FD) and high temperature oxidation(HTO).The weight loss of crude oil is 91.4% and oil begins to burn at 376℃.The viscosity of the crude oil increase form 2635 m Pa·s(50℃) to 7330 m Pa·s(50℃) within the effect of oxidation.After the reaction of oxidation, saturated hydrocarbon decrease from 29.78% to 14.98%,aromatic from 28.13% to21.37%,resin increase from 35.68% to 49.29% and asphaltene component from 6.14%to 14.36%.In the paper,crude oil is distilled to light,medium and heavy fraction.Then the Oxidation reaction of crude oil and these three fractions is taken under different temperature in different oxygen content. The results also shows that during oxidation reactions,aromatic tends to be oxidated to generate resin at low temperature.But at high temperature, saturated hydrocarbon and aromatic tends to genetate resin but hard to asphaltene The activation energy is the highest(477.42 k J/mol) in combustion sector and the lowest(7.61 k J/mol) in low temperature oxidation period.The activation energy increases in low temperature oxidation period but decreases in fuel deposition and combustion sector with the rise of experiment temperature and oxygen content atmosphere.