This study investigates the behavior of bentonite, used as a buffer material in deep geological disposal systems, in the context of pore morphology under the influence of field-collected groundwater conditions. The bentonite was processed into block form using cold isostatic press (CIP) and subsequently analyzed for its pore morphology in situ using synchrotron X-ray computed tomography (CT) within the field-collected groundwater environment. Bentonite buffers play a critical role in deep geological disposal systems by preventing contact between disposal containers and groundwater. Bentonite typically exhibits swelling upon contact with water, forming few layers of water molecules between its structural layers. However, the presence of ions such as K+ and Cl- can lead to a sharp reduction in swelling pressure. Loss of swelling pressure could negatively impact the integrity of future deep geological disposal systems, making its assessment crucial. This study involves processing various types of bentonite, including natural Na-type bentonite, into block forms and subjecting them to exposure in both deionized water and field-collected groundwater conditions. Internal pore morphology changes were measured using Xray CT technology.