Assessing the potential of CO2 huff ‘n’ puff technology for enhanced oil recovery and CO2 sequestration in tight oil reservoirs

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Fossil fuels utilization will produce a large amount of CO2, which causes a series of environmental problems. However, the exhaust CO2 can be used to achieve oil recovery improvement (CO2 EOR), while simultaneously allowing for the geological storage of CO2. For the unconventional reservoir, CO2 huff ‘n’ puff (HNP) is a potential technology showing promising results in laboratory experiments, while its effectiveness in enhancing oil recovery and CO2 sequestration at the reservoir scale remains uncertain. Thus, further research is needed to evaluate the CO2 HNP performance for its implementation. In this paper, we conducted a numerical simulation of the CO2 HNP process in a real tight oil reservoir (1800 m × 350 m × 10m in size) to assess its potential for improving oil recovery, CO2 injectivity, and CO2 sequestration. The results show that the accumulative oil production increased by more than 20% after the implementation of CO2 HNP. Meanwhile, CO2 HNP in tight oil reservoirs is proven capable to achieve CO2 injectivities of more than 4×107 SCm3 and CO2 storages of more than 5×106 SCm3. We designed 3 CO2 HNP schemes and found that the largest CO2 storage does not occur in the optimal scenario for oil production. A new type of CO2 HNP evaluation system considering oil production and storage capacity needs to be established. The results of the article suggest that CO2 HNP can achieve an oil production increase and CO2 storage in tight reservoirs, which has a positive significance for the sustainable development of environmental protection.