A novel supramolecular deep eutectic solvent enhancer for fracturing-oil expulsion fluids

Crude oil remains the predominant energy source today. Clean fracturing fluids (CFFs) have great potential to overcome the challenges of unconventional oil reservoir development due to their integrated fracturing-oil expulsion characteristics. The performance of CFFs is closely related to oil production. In this work, a novel β-cyclodextrin (β-CD)-based supramolecular deep eutectic solvent (SDES) was developed as a promising enhancer for CFF performance. The SDES facilitates the formation of high-strength micelle networks through hydrogen bonds and host–guest interactions to significantly improve the rheological properties, temperature resistance and drag reduction performances of CFFs. The ion–dipole interactions between SDES components and salt cations restrain micelle disassembly, thereby enabling remarkable resistance of CFFs to salt. SDES could further increase the imbibition efficiency to 45.4 % in 62 h because of its interface activity. SDES also endowed CFF with superior gel breaking performance and reusability. Moreover, SDES hardly resulted in the reduction of reservoir permeability. The β-CD in SDES further enhanced the interactions between compounds in CFFs, making it a more effective option compared with traditional DES. This work demonstrates the substantial potential of SDES as a new and green medium for improving the CFF performance, offering promising prospects for the industry.