oa Potential of CO2–polyether Mixed Fluid for Enhanced Oil Recovery and CO2 Storage in Shale Reservoirs

This study highlights the potential of a CO2-surfactant mixed fluid, formulated with a low-molecular-weight, non-fluorinated nonionic surfactant C4(PO)3, to enhance both shale oil recovery and CO2 sequestration. The surfactant C4(PO)3 showed excellent solubility in CO2 and significantly reduced the IFT and MMP of the CO2-shale oil system, while promoting wettability alteration from oil-wet to CO2-wet. Core-scale experiments showed that the application of 0.5 wt% CO2–C4(PO)3 mixed fluid improved oil mobilization in nanopores by up to 15.2%, enhanced ad-/absorbed oil recovery by 14.1%, and increased CO2 storage by 25.5%. These findings demonstrate that the CO2-surfactant system effectively addresses key limitations of conventional CO2 huff-n-puff, offering a promising strategy for efficient shale oil development and geological carbon storage.