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Monitoring the Role of Fracture Geometrical Characteristics on Fingering Initiation/Development during Heavy Oil Miscible Displacements in Fractured Porous Media

Finger initiation/development at fluid-fluid interface during miscible floods can cause poor displacement efficiency, which is undesirable in enhanced oil recovery processes. In this work, a series of hydrocarbon injection experiments performed on 5-spot glass micromodels that were initially saturated with the heavy crude oil. The fractured micromodels with different fracture geometrical characteristics were used in the tests. High quality image analysis was applied to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that higher solvent dispersion in the fractures rather than matrix in both longitudinal and transversal directions cause the finger behavior to be affected by the fracture geometrical characteristics. It also diminishes and merges the fingers to a unit solvent front by increasing spreading in regions near fractures. Due to the heterogeneity induced by fractures in media, finger tip splitting initiates before solvent breakthrough. In fact, longitudinal dispersion improves shielding, while transversal dispersion increases the fingers spreading and splitting. In addition, it has been revealed that splitting, before and after breakthrough, as well as spreading in regions near fractures is directly proportional to the fracture scattering, fracture discontinuity, and fracture density of the medium. Also, it has been found that shielding phenomena is mostly affected by fracture orientation in which its maximum occurrence is for the case of zero degree to average flow path. The results of this work can be helpful for a better understanding of viscous fingering behavior, which is crucial for accurate prediction of oil recovery in fractured reservoirs during miscible displacements.