CO2 flooding in shale oil reservoir with radial borehole fracturing for CO2 storage and enhanced oil recovery

This study introduces a novel method integrating CO2 flooding with radial borehole fracturing for enhanced oil recovery and CO2 underground storage, a solution to the limited vertical stimulation reservoir volume in horizontal well fracturing. A numerical model is established to investigate the production rate, reservoir pressure field, and CO2 saturation distribution corresponding to changing time of CO2 flooding with radial borehole fracturing. A sensitivity analysis on the influence of CO2 injection location, layer spacing, pressure difference, borehole number, and hydraulic fractures on oil production and CO2 storage is conducted. The CO2 flooding process is divided into four stages. Reductions in layer spacing will significantly improve oil production rate and gas storage capacity. However, serious gas channeling can occur when the spacing is lower than 20 m. Increasing the pressure difference between the producer and injector, the borehole number, the hydraulic fracture height, and the fracture width can also increase the oil production rate and gas storage rate. Sensitivity analysis shows that layer spacing and fracture height greatly influence gas storage and oil production. Research outcomes are expected to provide a theoretical basis for the efficient development of shale oil reservoirs in the vertical direction.