Development of CO2/N2 responsive nano-dispersion system for channeling blocking during CO2 flooding in low-permeability reservoirs

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    To address the low CO2 sweep efficiency and gas channeling in low-permeability reservoirs,this paper synthesized the CO2/N2 responsive nano-SiO2 to control gas channeling and fingering and increase the swept range of CO2 flooding.The synthesized responsive nano-SiO2 was characterized by infrared spectroscopy,thermogravimetric analysis,and other methods. Systematic research was conducted on its particle size,responsiveness,adsorption capacity,and dispersion stability under dispersion conditions. Moreover,a core flow device was employed for the simulation experiment of oil displacement in the presence of the CO2/N2 responsive nano-dispersion system. The results show that the CO2/N2 responsive nanoSiO2 meets the expected design. Under the dispersion conditions,the average particle size of the responsive nano-SiO2 is 58.8 nm,which is responsive to CO2/N2. The CO2 adsorption capacity reaches 196.8 mmol/g,which indicates dispersion stability. The 3 PV nano-dispersion system has a blocking rate of 89.38% in a core with permeability of 5.8 mD and realizes enhanced oil recovery(EOR)of 15.15% and ultimate recovery of 53.44%. In the simulated core experiment,the gas channeling channel in the formation is blocked owing to particle agglomeration of the responsive nano-SiO2 dispersion system at the deprotonation state,and thereby the oil displacement effect of the low-permeability channel is increased. In short,the developed CO2/N2 responsive nano-SiO2 dispersion system is capable of both effectively blocking gas channeling channels in formations and enhancing the sweep efficiency of CO2 flooding.

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  • Online: June 21,2022
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