Experimental Investigation of Enhanced Oil Recovery Mechanisms of Air Injection under a Low-Temperature Oxidation Process: Thermal Effect and Residual Oil Recovery Efficiency

Abstract

The air injection process (AIP) has been applied as an enhanced oil recovery (EOR) method in the light oil reservoir for decades. When high-temperature combustion reactions cannot be achieved, the low-temperature oxidation (LTO) reactions will dominate the AIP. The exothermic intensity of LTO reactions is much milder than that of high-temperature combustion reactions, which caused the thermal effect of the LTO reactions to be underestimated by researchers for a long time. Besides the thermal effect, questions such as whether LTO reactions could improve recovery efficiency and whether the LTO reactions could produce residual oil from the reservoir need to be answered. In this study, a series of isothermal core flooding tests under different environmental temperature conditions were applied to study the thermal effect on oil recovery. In addition, alternate injection of nitrogen and air was performed to study the LTO effect on oil recovery besides the thermal effect. The experimental results showed that the thermal effect can play a significant role on recovery performance because a higher temperature results in a higher oil recovery factor, where a temperature increment of 40 °C by the LTO reactions can result in a 10% recovery factor increase. On the other side, the LTO effect on producing residual oil was not observed in this study. Moreover, despite the thermal effect, the LTO-generated oxygenated compounds will increase the viscosity of the crude oil, which will decrease the recovery efficiency. Therefore, because the thermal effect of LTO works against the viscosity increment effect of LTO, the AIP is recommended only if the thermal effect is more significant compared to the increased viscosity effect in terms of recovery efficiency.

Dynamic Behaviors and Mechanisms of Air-Foam Flooding at High Pressure and Reservoir Temperature via Microfluidic Experiments

“…Therefore, the displacement performance is directly achieved by the flue gas, which is composed of CO 2 and N 2 generated in reservoirs and light components extracted from oil. 12,13 Generally speaking, air injection into lowpermeability and light oil reservoirs is an effective method that can improve oil recovery more economically and efficiently with important practical significance and broad market prospects. Nevertheless, it is not easy to obtain ideal oil displacement performance in strong heterogeneous reservoirs by merely applying air injection.…”

“…In the oxidation processes, the generated heat can increase the reservoir temperature and promote the volatilization of light components in oil. Therefore, the displacement performance is directly achieved by the flue gas, which is composed of CO 2 and N 2 generated in reservoirs and light components extracted from oil. , Generally speaking, air injection into low-permeability and light oil reservoirs is an effective method that can improve oil recovery more economically and efficiently with important practical significance and broad market prospects.…”

Feasibility study on further enhanced oil recovery by ISC of remaining oil after polymer flooding

“…[9][10][11][12] If the ISC is introduced into a light oil reservoir and oxygen is rapidly consumed using a high-temperature combustion front, it can solve the problem of oxygen safety in the light oil injection air on the one hand, and improve the crude oil recovery factor on the other hand. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Therefore, the ISC technology can be used as a polymer-ooding technology replacement method to further improve oil recovery. However, studies on whether the ISC technology is suitable for thin oil reservoirs aer polymer ooding are limited.…”

“…9–12 If the ISC is introduced into a light oil reservoir and oxygen is rapidly consumed using a high-temperature combustion front, it can solve the problem of oxygen safety in the light oil injection air on the one hand, and improve the crude oil recovery factor on the other hand. 13–28…”

Quantification of low‐temperature oxidation of light oil and its SAR fractions with TG‐DSC and TG‐FTIR analysis

“…However, both the main components involved in the LTO reaction and the differences associated with the oxidation characteristics among different components have not been well understood. To quantify the oxidation characteristics of crude oils, thermal analysis such as thermogravimetric analysis and differential scanning calorimetry (TG‐DSC), pressure differential scanning calorimetry (PDSC), and thermogravimetric analysis coupled with Fourier transform infrared spectrometer (TG‐FTIR) have been applied to investigate the oxidation properties of crude oil and its SARA fractions, as summarized in Table . Also, this table tabulates the reaction modes and characteristics during the combustion of light and heavy oils, the kinetics and thermochemical parameters of each reaction mode, the differences of oxidation characteristics between light, medium, and heavy oils, the oxidation relationship of crude oil and SARA fractions during the combustion process, and the combustion process of asphalt binder and its SARA fractions, respectively.…”