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

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.