The microstructure of coal reservoirs, especially the pore structure, alters as a result of physicochemical reactions between the CO₂ acidic fluid and coals. However, it is still unclear what controls this process and how the pore structure properties of coal alter by the action of CO₂ acid fluids change over time. The objective of this study is to identify the underlying mechanism by analyzing the changes in the mineral composition, surface roughness, as well as micropore and mesopore structure of anthracite and bituminous coal when exposed to supercritical CO₂ (ScCO₂)-H₂O. The results indicate that coal reservoirs primarily undergo processes of adsorption expansion and mineral dissolution/precipitation. Among these, adsorption expansion concluded or weakened after 7 days, with mineral precipitation gradually becoming the dominant factor, which results in more secure geological CO₂ storage (GCS). Furthermore, comparative analysis of anthracite and bituminous coal with untreated and long-term treatment demonstrates that anthracite exhibits higher CO₂ storage capacity and greater wettability. Consequently, anthracite is more suitable as a target reservoir for GCS compared to bituminous coal. These results, therefore, offer a theoretical foundation and a guide for choosing GCS sites in deep un-minable coal seams.

由于CO ₂酸性流体与煤之间的物理化学反应，煤储层的微观结构，特别是孔隙结构发生改变。_{然而，目前尚不清楚是什么控制了这一过程，以及煤的孔隙结构特性如何通过CO 2}酸性流体的作用随时间变化而改变。本研究的目的是通过分析无烟煤和烟煤暴露于超临界 CO ₂ (ScCO ₂ )-H ₂ O时矿物成分、表面粗糙度以及微孔和中孔结构的变化，以确定其潜在机制。结果表明，煤储层主要经历吸附膨胀和矿物溶解/沉淀过程。其中，吸附膨胀在7天后结束或减弱，矿物沉淀逐渐成为主导因素，从而导致更安全的地质CO ₂储存（GCS）。此外，对未经处理和长期处理的无烟煤和烟煤的比较分析表明，无烟煤表现出更高的CO ₂存储能力和更大的润湿性。因此，与烟煤相比，无烟煤更适合作为 GCS 的目标储层。因此，这些结果为深部不可开采煤层GCS选址提供了理论基础和指导。