Due to the increasing energy consumption and the promoting of the carbon neutral target, the exploitation of shale oil and gas, as well as carbon dioxide sequestration and hydrogen storage using shale as caprock, has received enormous attention. As a foundation for these hotspots, the characterization of pore structure in shale reservoirs has been widely studied. In this paper, the application of fluid intrusion and radiation methods in the characterization of pore structure in shale reservoirs was systematically reviewed, and the merits and limitations of both methods were highlighted. Taking the Fengcheng shale as an example, a detailed investigation of the fluid occurrence state was conducted, indicating that the fluid occurrence state significantly impacts the exploitation of hydrocarbon from shale reservoirs. Furthermore, there needs to be a systematic of investigation of how the pore structure characteristics and inorganic components of shale reservoirs control the integrity and safety of CO₂ and H₂ storage. Moreover, confinement effect of nanopores in shale should be paid attention to in future research on carbon and hydrogen storage.

Pore structure has a significant effect on the occurrence state of shale hydrocarbons and the hydrocarbon storage capability of shale reservoirs. Consequently, it is quite meaningful to clarify the shale pore structure evolution characteristics for understanding the migration and enrichment mechanisms of hydrocarbons within shale reservoirs during different geological stages. The abundant existence of organic matter within shales complicates the shale pore structure evolution process by hydrocarbon generation, migration and cracking. Many studies have been conducted to reveal the shale pore structure evolution characteristics and the controlling factors. Basically, these studies could be divided into two categories based on the sample source: comparing the pore structure of natural shale samples with different thermal maturities; obtaining shale samples with different thermal maturities by conducting thermal simulation experiments on low-mature shale samples and comparing the pore structure of these simulated shale samples. However, no consistent viewpoint on shale pore structure evolution has been reached. This review presents the state of the art of shale pore structure evolution studies. It is widely recognized in the literature that both the inorganic and organic diagenesis control the shale pore structure evolution process. However, it is found that the shale pore structure evolution models proposed in the literature were largely dependent on the samples used. And it is recommended to conduct the two categories of studies simultaneously in order to obtain more reliable shale pore structure evolution characteristics in future investigations.