Experimental Study on the Safety of Exhaust Gas in the Air Injection Process for Light Oil Reservoirs

Abstract

Air injection is a very important technique that is used to enhance the recovery of light oil. To investigate the safety of exhaust gas in an air injection process for light oil reservoirs, static low-temperature oxidation experiments were carried out on oil samples from a block of the Liaohe oilfield in northeast China. The effects of the temperature (80−140 °C) and pressure (10−20 MPa) on the oxygen content of the exhaust gas were studied. It was found that the oxygen consumption rate increases with the temperature. When the temperature rises to 130 °C, the oxygen content in the exhaust gas is much lower than the theoretical calculation of the safe oxygen content, and when the temperature reaches 140 °C, it is nearly exhausted. The effect of the pressure on the oxygen consumption rate is extremely low. Using a component analysis of the crude oil prior to and after the reaction, we observe that aromatic hydrocarbons are barely involved in the reaction at temperatures less than 120 °C. However, when the temperature increases above 130 °C, the aromatic hydrocarbons contribute to the reaction, which results in a large amount of oxygen consumption. Therefore, if the temperature can be controlled within 130−140 °C during the air injection process at the Liaohe oilfield, the oxygen content of the exhaust gas will remain in a safe range.

Chain Reactions Approach to the Initial Stages of Crude Oil Oxidation

“…The crude oil behavior in isothermal mode has a rather common time dependence like (). The parameters oxygen uptake and CO and CO 2 gas output have rising time dependence which strives for a constant value like that presented for coke formation and maltene and aspaltene reduction in refs and .…”

“…17 And kinetic parameters are mainly obtained according to this data. 18,19 In fact oil degradation and coke formation is observed. 20 Sometimes oil is so reactive that one can observe self-heating effects even under isothermal conditionslike in refs 21 and 22.…”

“…Both isothermal − and adiabatic − experiments performed for crude oils have the goal to explore initial stages of oxidation and possibility of self-ignition. This means that experiments are performed at reservoir conditions or not much different from the reservoir conditions.…”

“…The main difference between adiabatic and isothermal low temperature experiments is that in isothermal conditions one just examines the parameters of outgoing gases and differences in oil properties which vary with time . And kinetic parameters are mainly obtained according to this data. , In fact oil degradation and coke formation is observed . Sometimes oil is so reactive that one can observe self-heating effects even under isothermal conditionslike in refs and .…”

In Situ Combustion of Heavy, Medium, and Light Crude Oils: Low-Temperature Oxidation in Terms of a Chain Reaction Approach

“…Most likely, the features of light and heavy oil oxidation are associated with the presence of substances that affect the oxidation process at the stage of chain growth by a radical mechanism. 24 Generally speaking, we consider the following main inhibition reaction: Reaction 7 is an oxygenation reaction without further development of combustion, which leads to a high molecular residue. This process causes fuel formation at low temperatures; in fact, this process together with reaction 5 leads to the formation of inactive hydroperoxides or well-known oxygen addition reactions.…”