Microfluidic Device for Fast Pre-Screening of EOR Chemicals at Close to Reservoir Conditions

Microfluidic devices allow manipulations with the flow of fluids at sub-millimeter scales. The advantages of this technology include a significantly reduced volume of fluids required for certain physical and chemical characterizations; reproducible and enhanced mixing of flowing phases; better control over the heat exchange; access to imaging of the pore-scale flow phenomena; reduced cost of characterization methods when compared to some conventionally used methods and devices; and more. This work reports on an innovative approach to study the recovery of crude oil from microfluidic devices. This approach was designed to closely mimic the environment within pores of carbonate rocks.

Commonly used techniques to study the recovery of crude from saturated core plug samples are coreflooding and imbibition experiments using an Amott cell. Coreflooding is labor intensive, does not provide pore-scale imaging, takes close to a week or longer to operate, uses liters of solvents, and is also cost intensive. Imbibition experiments also do not provide a visual understanding of the oil recovery process at the pore scale. To address some of these challenges, transparent microfluidic devices made of glass that are capable of operating at close to reservoir conditions were developed to improve and complement conventionally used devices. These devices contain patterned channels representing carbonate pore networks. The interior surface of the channels are fully coated by growing a thin layer of calcite nanocrystals, which closely represent a carbonate reservoir’s rock chemistry. The surface is then treated by crude oil aging to generate appropriate wettability resembling the natural reservoir carbonates. The fabricated device was used to study the recovery of oil from porous networks and to successfully prescreen candidate surfactants for enhanced oil recovery (EOR) applications.

The microfluidic devices developed here allowed us to effectively differentiate between three in-house developed surfactant formulations. Data obtained by image analysis of the oil recovery process from within the porous microfluidic channels using various surfactants provided quantitative oil recovery for each chemical and served as a useful benchmark to differentiate the best candidate formulations. Results also were used to compare efficiency of surfactants based on interfacial tension and potential effects related to wettability alteration. The high-temperature microfluidics platform allows us to rapidly prescreen a large number of formulations for applications in EOR, visualize mobilization of the oil from porous structure at close to carbonate reservoir conditions, and allow cost savings by facilitating processes in developing best EOR formulations.