Spontaneous imbibition is a fundamental fluid flow mechanism that plays a significant role in various applications of multiphase fluid flow in porous media, including oil extraction from subsurface reservoirs and underground carbon dioxide storage. Understanding the dynamics of imbibition, driven by capillary forces across multilayered systems, is essential for designing and optimizing field applications. Laboratory experiments with the traditional Amott cell, commonly used to quantify the imbibition performance by immersing an oil-saturated core plug in water and measuring the extracted oil, do not fully replicate actual reservoir conditions. Under reservoir conditions, imbibition occurs within the porous formations across different rock types, while in the Amott cell, imbibition occurs between the rock and the open surrounding water medium. This misrepresentation of field conditions may not replicate the true potential of imbibition. In this study, we use micro-CT and dynamic pore-scale imaging as an alternative approach to visualize and quantify rock-to-rock imbibition within heterogeneous porous media, which cannot be achieved with traditional methods. This work aims at introducing a new concept to evaluate the imbibition mechanism across different porous formations, reflecting the conditions of multilayer systems in the subsurface.

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