Enhancing Frac Fluid Recovery in Unconventional Shale and Tight Gas Fracturing with Eco-Friendly Flowback Aids

Hydraulic fracturing, a method used to stimulate oil and gas from shale and tight formations, faces challenges like fluid blockage and fast declining oil or gas production rates due to the significant impact of capillary forces on water retention. To address this, surfactants and microemulsions are commonly employed as flowback additives to reduce surface and interfacial tension, enhancing water recovery during hydraulic fracturing. The effectiveness of a flowback additives is highly impacted by the harsh subsurface conditions, such as high salinity and high temperature. This study aims to assess the performance and effectiveness of methylimidazolium chloride based ionic liquids as flow back additives at high salinities and temperatures and compare it to commercially used flowback additives. Different experimental analysis was conducted to screen different concentrations of methylimidazolium chloride based ionic liquids (X1,X2,X3). Surface tension measurements were conducted to estimate the critical micelles concentrations (CMC). Spinning drop tensiometer was utilized to measure interfacial tension (IFT), in addition to contact angle measurements were used to evaluate the impact of the flowback additive on the wettability and the displacing behavior. Seawater was used as the base fracturing fluid with a salinity of 57,000 ppm and temperatures up to 90°c for all experiments. Different formulations were used and yielded surface tension values varied from 30 to 45 mN/m with CMC values ranging between 0.5 to 1 gpt which is similar to commercial flowback additives. The different formulations showed different IFT values with the lowest IFT value of 3 mN/m in the case of X3. In addition, contact angle measurements showed changing the rock surface to be more water-wet after treating the rock with the flowback additives. According to our results, methylimidazolium chloride-based ionic liquids can be used as environmentally friendly flowback additives especially in harsh conditions of high temperature and high salinity where the conventional additives are not suitable. This will contribute to the development of more sustainable and environmentally conscious practices in hydraulic fracturing operations. Ultimately, the utilization of these additives can help minimize water blockage, and formation damage impacts, and enhance shale gas production.