Enhanced Shale Oil Recovery Through Chemical Huff and Puff Using Surfactants, Nanoparticles, and Ketones

Shale oil is one of the most important oil resources in the United States, yet recovery remains challenging due to its extremely low permeability. Horizontal drilling and multi-stage hydraulic fracturing improve productivity, but depressurization recovery remains below 10% of OOIP, leaving substantial oil unrecovered and many horizontal wells on the verge of abandonment. This study systematically evaluates and compares the effectiveness of water-based chemical EOR agents-including surfactants, nanoparticles, and ketones-for enhancing shale oil recovery under reservoir conditions. A comprehensive experimental workflow was implemented, in which chemical candidates were first screened for aqueous stability and compatibility under high-temperature, highsalinity (HTHS) conditions, followed by evaluation of oil/water interfacial tension reduction and wettability alteration. Static spontaneous imbibition and dynamic Huff-n-Puff experiments were performed using Mancos shale outcrops (5% porosity, 100-200 nD permeability), supported by nuclear magnetic resonance (NMR) analysis employed to support pore-scale interpretation of recovery mechanisms. Four surfactants and two nanoparticles were selected based on aqueous stability and compatibility; one anionic and one zwitterionic surfactant were selected due to their wettability alteration capabilities. The spontaneous imbibition experiments demonstrated that the anionic surfactant achieved higher oil recovery than the zwitterionic one, while the surfactant/nanoparticle blend and the ketone exhibited slightly superior performance. Consistent recovery trends were observed during the Huff-n-Puff experiments, indicating similar chemical effectiveness under dynamic conditions. This work advances understanding of chemical EOR in shale reservoirs by providing a unified evaluation of surfactants, nanoparticles, and ketones under identical shale-relevant thermobaric conditions. The results highlight key differences in recovery behavior among these chemical agents and clarify their relative effectiveness in enhancing shale oil recovery. While laboratory-scale improvements were observed, further investigation is recommended to assess scalability and performance under field conditions.