Evaluation of surfactant performance in fracturing fluids for enhanced well productivity in unconventional reservoirs using Rock-on-a-Chip approach

Proper application of surfactants during hydraulic fracturing operations not only enhances initial production of a reservoir, but also helps sustain its long-term production. The most commonly used surfactant for low-permeability reservoirs is a non-emulsifying surfactant (NES). This study shows that a weakly emulsifying surfactant (WES) is better in solubilizing oil globules via self-association, and appears to be more efficient at mobilizing oil through tight pore throats than NES. The fundamental difference between these two surfactant types was found to be the emulsion tendency. The performance of the two surfactants was compared using a microfluidic based Rock-on-a-Chip (ROC) device with pore sizes comparable to shale formation rocks. The ROC allowed direct visualization of oil recovery by surfactants with controlled pore geometries and surface chemistry. Results showed that the WES yielded higher oil recovery efficiency at equal driving pressure compared to a non-surfactant-bearing control fluid and the NES. As a result of the laboratory testing indications, a multiple well trial program was conducted in two separate areas of the Eagle Ford shale. Early production results suggest that wells treated with the WES exhibited enhanced productivity compared to those treated with the NES.