Microfluidics As a Tool for Rapid Testing of Chemicals for Supercritical CO2 Foams

Sequestering CO₂ in underground oil reservoirs is helping to improve recovery of oil from porous structure of the reservoir rock. However, the low density and viscosity of supercritical CO₂ (sc-CO₂) does not allow for efficiently sweeping the whole reservoir area and displacing water and oil which occupies space in the reservoir. This leads to early breakthrough of the CO₂ from producing wells and to inefficient sequestration. To improve sweep efficiency, surfactant additives are among chemicals being studied to increase viscosity of the sc-CO₂ flood as they allow production of viscous foams/microemulsions when the sc-CO₂ and aqueous phases are mixing. A large number of reservoirs have harsh conditions with high salinity brines and temperatures exceeding 90 ⁰C. Developing surfactants for such conditions requires testing of a large number of candidates. Conventionally used techniques, like core flooding and foam loop rheometer experiments are expensive, complex, consume hundreds of mL formulations, and can take days to perform a measurement. This is not desirable when a large number of samples need to be screened. This work presents results performed on a microfluidics device used to screen a large number of samples and to evaluate the strength of the foam in the presence of sc-CO₂. Conventional foam rheometer testing was also used to compare results. The study suggests that the microfluidics device provides the capability to perform rapid screening of chemicals with one measurement taking less than an hour. Among other advantages are the utilization of only a small volume of sample, ability to visualize flow in pore spaces under the microscope, and increased safety due to reduced size of the highly pressurized instrument. Core flooding and conventional rheometer measurements are still of great importance and should be used to further evaluate best performing chemicals that have been downselected from the larger list of formulations.