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Enhanced Oil Recovery (EOR) through various methodologies has been an active research for many years seeking efficient methods to increase the crude oil recovery efficiency from oil reservoirs. Among different gas injection scenarios, carbon dioxide (CO2), natural gas (mainly methane (CH4)) and nitrogen (N2) injection are considered as promising EOR agents. Asphaltene precipitation and deposition during EOR methods cause severe problems, which affect the recovery efficiency and increase the cost of the incremental oil production. This study is aimed to investigate the effects of CH4 and N2 injection compared with CO2 injection on asphaltene precipitation and deposition. The different mole percent of the mentioned gases were introduced into the high-pressure cell, then the amount of precipitated asphaltene was measured at the reservoir condition. The evolution of asphaltene deposition was monitored through a high-resolution microscope. Moreover, Image processing software was utilized to check the amount of deposited asphaltene and its size distribution under different conditions. The most apparent finding to emerge from this study is that both CO2 and natural gas increase the amount of precipitated asphaltene whereas the nitrogen as an inert gas has no considerable effect on the amount of precipitated asphaltene. According to the results, the increment of precipitated asphaltene by CO2 is much higher than natural gas. Further, the thermodynamic solid model used in this study reasonably predicted the trend of asphaltene precipitation process for the mentioned EOR scenarios.

Asphaltene deposition during enhanced oil recovery (EOR) processes is one of the most problematic challenges in the petroleum industry, potentially resulting in flow blockage. Our understanding of the deposition mechanism with emphasis on the rate of the asphaltene deposition is still in its infancy and must be developed through a range of experiments and modelling studies. This study aims to investigate the rate of asphaltene deposition through a visual study under different gas injection scenarios. To visualise the asphaltene deposition, a high-pressure setup was designed and constructed, which enables us to record high-quality images of the deposition process over time. Present research compares the effects of nitrogen (N2), carbon dioxide (CO2) and methane (CH4) on the rate of asphaltene deposition at different pressures. The experimental results in the absence of gas injection revealed that the rate of asphaltene deposition increases at higher pressures. The results showed that the rate of asphaltene deposition in the case of CO2 injection is 1.2 times faster than CH4 injection at 100 bar pressure. However, N2 injection has less effect on the deposition rate. Finally, it has been concluded that the injection of CO2 leads to more asphaltene deposition in comparison with CH4 and N2. Moreover, the experimental results confirmed that gas injection affects the mechanism of asphaltene flocculation and leads to the formation of bigger flocculated asphaltene particles. The findings of this study can help for a better understanding of the mechanism of the asphaltene deposition during different gas-EOR processes.

Miscible carbon dioxide (CO2) flooding has become the most commonly and favorable approach in Enhanced Oil Recovery (EOR) because of its high oil reservoir sweep efficiency and contribution to the reduction of greenhouse gas emissions. Despite this, it can significantly favor the asphaltene deposition, which leads to the wettability reversal and formation damage. A novel experimental setup was utilized to study asphaltene deposition on the model rock at reservoir condition. The evolution of asphaltene deposition was monitored by a microscope; then analyzed by image processing software to check the amount of deposited asphaltene and its size distribution at different conditions. The amount of asphaltene deposition during natural pressure depletion and CO2 injection was measured experimentally and modeled using the thermodynamic solid model. The results indicated that during the pressure depletion process, asphaltene particles tend to dissolve in the solution. It is shown that the amount of asphaltene deposition increases as more CO2 is injected. Further, the thermodynamic solid model used for this case study included many empirical parameters required to match the experimental data comprehensively. A range of sensitivity analysis is carried out to investigate the effects of dominant parameters in this study. The proposed model used in this study reasonably predicted the trend of the asphaltene precipitation process for both pressure depletion and CO2 injection processes as oil recovery processes.