Abstract:

To promote carbon dioxide （CO₂） emission reduction and achieve carbon neutrality， we analyze recent technical advances in carbon capture， utilization， and storage （CCUS）， highlighting existing challenges and future directions. The findings indicate that the global CCUS industry is undergoing rapid growth， with the number of large-scale CCUS projects worldwide reaching up to 392 by the end of 2023， twice the number in 2022， demonstrating the preliminary commercial viability of CCUS. Significant progress have been made in the research and application of the geological storage and utilization of CO₂， including （1） the use of representative elementary volume （REV） in the characterization and modeling of geological CO₂ storage reservoirs， enabling the application of microscopic properties to macroscopic geological models； the utilization of strain tensors in the dynamic characterization and monitoring of storage reservoirs； the comprehensive application of many techniques， including geochemical imaging， micro-seismic， fiber optics， and geothermal and atmospheric monitoring for leakage detection of the CO₂ storage reservoirs； and the development of simulation techniques to simulate various CO₂ plume migration scenarios and sequestration potentials in the storage reservoirs， tailored to the various types of sedimentary reservoirs； （2） the wide application of big data technologies and artificial intelligence （AI） in CCUS， including the development of proxy models for the rapid risk assessment of CO₂ sequestration based on deep learning and coupled geomechanics and the utilization of machine learning to predict or assess the CO₂ enhanced oil recovery （EOR） and storage efficiency in residual oil zones； （3） significant progress in the new techniques for CO₂ EOR and their application in new fields. Emerging techniques， such as alternating injection of CO₂ and low mineralized water， CO₂ micro-nano bubble flooding， thickener-assisted CO₂ flooding， and CO₂ foam flooding， have shown promising results in field tests. Furthermore， the application of CO₂ flooding has expanded from medium- to low-permeability sandstone oil reservoirs and tight sandstone oil reservoirs to residual oil zones （ROZs）， and shale oil and gas reservoirs. However， there are still challenges related to the safety of the long-term sequestration of captured CO₂， economic viability， and technical uncertainties. Therefore， it is necessary to further improve existing laws and regulations while vigorously developing new techniques for the geological storage and utilization of CO₂ by conducting multidisciplinary research and technological innovation， and promoting international cooperation， with a view to ensuring the safety of the long-term storage of captured CO₂ and enhancing the economic viability of commercial operations.

Key words: safety assessment, representative elementary volume （REV）, micro-nano bubble, residual oil zone（ROZ）, geological storage reservoir, CO? flooding, carbon capture and storage （CCS）, CCUS