Development and Characterization of a Novel Supramolecular Fracturing Fluid for Deep Shale Gas Reservoirs

Abstract

To enhance the fracturing efficiency of deep shale gas reservoirs, a novel supramolecular surfactant, SPU-2, was synthesized using long-chain fatty acid monomers, 3-dimethylaminopropylamine, and sodium 3-chloro-2-hydroxypropane sulfonate as raw materials. The molecular structure of SPU-2 was characterized by Fourier transform infrared spectroscopy. By combining SPU-2 with a hydrophobically associating polymer (HPA-1), a new supramolecular fracturing fluid system (0.5% SPU-2 + 0.2% HPA-1) suitable for deep shale gas reservoirs was developed, and its overall performance was systematically evaluated. The results indicate that the supramolecular fracturing fluid exhibits excellent thermal and shear resistance, maintaining a viscosity above 50    mPa · s after continuous shearing at 150°C for 120 min. The system also demonstrates remarkable salt tolerance, i.e., its viscosity remains stable even at a brine salinity of 204,200    mg / L . Further, the fluid displays favorable viscoelasticity, drag-reduction, and gel-breaking properties. The gel-broken fluid features low surface tension ( < 27    mN / m ), minimal residue content ( < 10    mg / L ), and a high clay-swelling inhibition rate ( > 90 % ). Its damage to the proppant-supported fracture conductivity is less than 10%. These findings suggest that the developed supramolecular fracturing fluid system can meet the operational requirements of hydraulic fracturing in deep shale gas reservoirs and holds significant potential for field application.