Investigating the Dependency of Liquid Bridge and Two-Phase Pressure Difference inside Fracture on Fractured Rock Properties in Gravity Drainage

In fractured reservoirs under the gravity drainage, the oil transfer between adjacent matrix blocks is one of the main factors in determining the degree of oil recovery. Communication between matrix blocks can occur by forming a liquid bridge between two adjacent matrices. Therefore, in this study, by modeling and simulating in Comsol, we investigated the characteristics of the liquid bridge formed inside the fracture and the dependency of the liquid bridge shape and the pressure difference on the fracture properties such as the fracture aperture, matrix permeability and wettability. Moreover, the initial and boundary conditions in the problem are set such that it can show physically the flow exchange between the matrix and fracture in reservoir conditions. Furthermore, the results of this simulation showed that the liquid bridge throat decreases with the size of the fracture aperture. In addition, this change in the liquid bridge causes the two-phase pressure difference to decrease with the increase of the fracture aperture, and after a critical value (for example, 1.7 mm), it becomes negative. Also, the results showed that as the contact angle increases toward neutral wettability, the more vertically liquid bridge formed and it leads to small changes (40 psi) for two phase pressure difference inside the fracture. In addition, with the increase in rock permeability and more flow entering the fracture, the throat radius of the formed liquid bridge increased from about 0.03 mm to about 0.05 mm, which it is consistent with the published laboratory data. The findings of this research can be used for better understanding how the liquid bridge changes and its effect on the of the two-phase pressure difference, which is a controlling parameter for two phase interface inside fracture.