Visual investigation of viscous cross-flow during foam injection in a matrix-fracture system

A micromodel setup has been implemented to visualize foam propagation into the matrix and recovery of the matrix's fluid. For simplicity, the experiments have been conducted in the absence of oleic phase; however, the achievements of this study can significantly affect the knowledge of foam flow in fractured reservoirs for enhanced oil recovery processes. New qualitative descriptions have been presented in terms of viscous cross-flow using well designed experiments and discussions. The effect of viscous cross-flow on the recovery of the matrix's fluid has been evidenced via a mechanistic study based on the comparison of the recovery variation versus the foam quality, injection rate, and injectant type. Meanwhile, generation and coalescence mechanisms have been investigated. The results of these experiments demonstrate that a convective viscous cross-flow orthogonal to the direction of the mainstream (flow direction in the fracture) has been generated during foam injection that can significantly recover the bypassed fluid. In addition, it has been shown that foam invasion within the matrix controls the amount of ultimate recovery factor and is proportional to the foam viscosity in the fracture. Furthermore, the amount of recovery of the bypassed fluid increases as the foam quality increases. However, increasing the total injection rate causes a decrease in fluid recovery due to shear thinning behavior of foam.