The reduction of anthropogenic carbon dioxide (CO₂) in the atmosphere is crucial for mitigating the climate change. CO₂ capture and storage (CCS) is considered as one of the most promising options for carbon reduction. The main means is injection of CO₂ into structural reservoirs in deep, permeable geologic formations. The aim of this paper is to identify the main research needs and gaps in trapping mechanisms of geological carbon sequestration. Trapping mechanisms for geological sequestration include hydrodynamic trapping, solubility trapping, and mineral trapping. The properties of the CO₂-water/brine system as well as the hydrodynamics, geophysics, and geochemistry of the reservoir rock/fluid system are discussed.