The application of microfluidics in the study of multiphase flow and transport in porous media of improved hydrocarbon recovery methods

Fundamental investigation of the underlying physics in multiphase flow and transport phenomena in porous media is crucial for many engineering processes, including environmental remediation, geological sequestration, and improved hydrocarbon recovery. Microfluidics are widely used to provide direct, in-time visualization of multiphase flow behavior at the pore-scale and sometimes extend to the representative elementary volumes (REV) scale. Qualitative and quantitative analysis are obtained from microfluidic experiments and are used for mechanisms interpretations. In this work, microfluidics and micromodels are designed to explore fundamental mechanisms in several enhanced/improved oil recovery processes by performing systematic experiments. First, a study of the low salinity effects in improved oil recovery by microfluidics experiments is presented which explains a type of low-salinity effect with delayed oil recovery and without the presence of clay. Experiments were performed from single-pore microfluidics to a REV scale reservoir-on-a-chip model. A time-dependent, oil-water interaction controlled by diffusion was proposed based on the pore-scale observations. Second, the time-dependent behaviors and the role of surfactant during the low salinity waterflood is further investigated by systematic experiments in a 2.5D, inch-long micromodel using mineral oils with different surfactant concentrations and water with different salinities. It is found that the low salinity effects are significant when the surfactant concentration is sufficiently high. The surfactant also dominates the time-dependent behaviors, where higher surfactant concentration leads to shorter delay time. Third, three inch-long “reservoir-on-a-chip” micromodels were utilized to probe the impacts of the microfracture connectivity on the displacement efficiency and sweep patterns when the mobility ratio is unfavorable and the displacement is unstable. It was observed the presence of microfractures do not necessarily improve the displacement efficiency, but the microfracture connectivity, capillary number and wettability altogether impact on the displacement patterns and the ultimate recovery. Last, the role of viscoelasticity’s effects in reducing residual oil saturation is investigated by performing microfluidic experiments in foot-long (30 cm), heterogeneous glass micromodels (“coreflood-on-a-chip”). Significant redistribution and reconnection of residual ganglia occur due to viscoelasticity induced instabilities during high-viscoelasticity polymer floods, which results in residual ganglia remobilization that ultimately reduces residual saturation