Factors Influencing CO₂ Huff-and-Puff for Increasing Its Storage Capacity and Shale Oil Recovery

For clarifying the effect of shale oil CO₂ huff-puff on recovery and storage, the nuclear magnetic resonance (NMR) device was employed to conduct huff-puff experiments, investigating the effects of formation pressure, huff-puff cycles, soaking time and core permeability on the role of shale oil CO₂ huff-puff. The results demonstrate that under miscible conditions, the increase in recovery form macropores and mesopores decreases with increasing formation pressure, the increase in recovery from macropores and mesopores rises rapidly under non-miscible conditions, while the recovery from micropores always rises linearly with increasing formation pressure. The improvement of CO₂ huff-puff recovery is more significant when the formation pressure is lower than the minimum miscible pressure, while the improvement of huff-puff recovery is weaker when the formation pressure is higher than the miscible pressure. The recovery enhancement rate of large and mesopores slows down during soaking time, while the recovery enhancement rate of micropores was on a trend of increasing and then decreasing; When the number of throughput rounds increases, the recovery enhancement of mesopores and puffs are more significant, while the increase of micropores is relatively small; the formation pressure is positively correlated with the huff-puff effect, and the number of huffs-puffs decreases with the increase of pressure; The greater the permeability of the core, the higher the pore recovery. This investigation is a guideline for improving the recovery of shale oil CO₂ huff-puff and effectively implementing storage.