Pore-scale method for instantaneous assessment of total permeability including the pore geometry effect in microfluidic porous networks through the use of an analogous electrical circuit

Abstract

Permeability estimation is crucial for providing fundamental information isrequired to establish production and injection rates. Several experimental and numerical approaches have been developed to evaluate the permeability of rock reservoirs at large scales (core-, reservoir-, and field- scales). However, the evaluation of the permeability at the micro-scale has remained a challenge due to the small length scale, variety and complexity of the porous structure of the microfluidic devices. Increasing usage of microfluidic devices in the petroleum field to visualize the pore events and evaluate enhanced oil recovery (EOR) techniques necessitates characterization of permeability at the pore scale. Herein, by the combination of an integrated microfluidic set-up and the analogous electrical circuit, we upgraded the conventional methods to provide an accurate, reproducible, and practical on-chip approach to the real-time absolute permeability of pore networks. Based on the designed fluidic set-up, a sequential flow rate stepping scheme was optimized and used to estimate the permeability of the porous networks after thoroughly saturating them with a fluorescein solution that was driven to the system by a pressure controller. The permeability of the micromodels was obtained by applying Darcy’s law for laminar flow after estimating the differential pressure across the whole system and the pore networks by measuring the equivalent flow resistances of the fluidic circuit. The method is highly accurate, sensitive, and effectively predicts the absolute permeability of the micromodels. The use of a pressure controller and pressure sensors affords the potential of parallelization of the microfluidic set-up and delivers high throughput compared to the previous proposed techniques. The validation of the approach was based on its independence of the porous medium geology and by providing convergent results between the experimental and computed permeability in the microfluidic devices. Moreover, this approach will help in delivering qualitative and quantitative data to understand capillary phenomena and dominant mechanisms of different chemical EOR processes at the pore scale.