Factors and applications of carbon dioxide huff-and-puff technology in small toothbrush-shaped oil reservoirs

Abstract Carbon dioxide (CO2) flooding is an effective method for enhanced oil recovery. However, its application in complex, small-block reservoirs presents significant challenges owing to their limited size and intricate oil–water systems. This study investigates the potential and effectiveness of CO2 huff-and-puff technology for improving oil recovery in such reservoirs, with a focus on identifying key influencing factors. A “toothbrush-shaped” reservoir in the Shulu Sag was selected for a case study. Its geological framework, sand body types, and pore types were characterized, and a three-dimensional geological model was constructed. Based on the CO2 flooding theory, a mathematical model tailored to the study area was developed to simulate CO2 huff-and-puff processes. Numerical simulations were conducted to investigate the impact of various parameters and influencing factors on oil recovery. The predicted oil recovery from CO2 huff-and-puff in the toothbrush-shaped reservoir was then calibrated against production data from existing CO2 huff-and-puff wells. The study found that heterogeneous reservoirs with moderate heterogeneity and oil saturation greater than 0.5 are suitable candidates for CO2 huff-and-puff. Furthermore, a soaking period of 20 days yielded favorable development outcomes. These findings provide valuable insights for enhancing oil recovery in similar reservoirs.