CO2 huff-n-puff combined with radial borehole fracturing to enhance oil recovery and store CO2in a shale oil reservoir

This study pioneers the integration of CO2 huff-n-puff and radial borehole fracturing, enhancing shale oil recovery and facilitating CO2 storage. To evaluate the performance of CO2 huff-n-puff with radial borehole fracturing, a numerical compositional model is developed, enabling a comparison of CO2 huff-n-puff performance between radial borehole and horizontal well fracturing, while assessing the influence of various parameters, including CO2 diffusion, lateral configuration, fracture parameters, cycle number, soak duration, production time, injection pressure, and production pressure on oil and gas production, as well as CO2 storage. The results indicate that increasing the number of layers in radial borehole construction can effectively enhance the vertical exploitation efficiency of oil reservoirs. The cumulative oil production of the three-layer, four-branch radial borehole fracturing pattern is 1.66 times higher than that of the horizontal fracturing with 20 fractures. Moreover, it also identifies the principle of enhancing the number of radial boreholes per layer and increasing fracture length to optimize horizontal reservoir exploitation. A 5% reduction in individual cyclic duration from the base case significantly influences the initial high-flow phase, yielding a hydrocarbon production 1.35 times higher. Further strategies to enhance CO2 huff-n-puff efficacy include diminishing the soak stage's proportion and adjusting the temporal proportion of the production stage to 75% for oil extraction and 30% for CO2 storage. Increasing the injection pressure impacts the storage capacity of CO2 significantly, whereas reducing production pressure affects oil and gas production. The findings of this study present a novel method and provide a theoretical foundation for the efficient and economical development of shale oil.