Thermoresponsive in Situ Generated Proppant Based on Liquid–Solid Transition of a Supramolecular Self-Propping Fracturing Fluid

A thermoresponsive in situ generated proppant based on liquid–solid transition of a supramolecular self-propping fracturing fluid was developed. At lower temperatures (below gas/oil reservoir temperature), the supramolecular fracturing fluid is in the liquid state; with the increase of temperature, the self-propping fracturing fluid becomes a solid proppant during the phase transition. This particular conversion was characterized by scanning electron microscopy, nuclear magnetic resonance, viscosity, viscoelasticity, leak-off, friction, mechanical properties, and conductivity tests. All test results indicated that noncovalent interactions between the components led to the supramolecular proppant generated. These scientific findings showed that the self-propping fracturing fluid is a proppant solid-particle-free liquid with good fluidity at lower temperatures. After injection to a fracture in reservoir formation, the self-propping fracturing fluid gradually transformed into solid proppant particles with good mechanical strength stimulated by the reservoir high temperature. The critical phase transformation temperature and time could be adjusted by a change in the composition. This novel self-propping fracturing fluid is solid ceramsite and quartz proppant free, and there is no need to add thickeners and cross-linkers. Comparisons with existing proppant-carrying fluid mixture of a solid proppant and high viscosity fracturing fluid, damage by fracturing fluid gel residues, abrasion of the pumping equipment and tubes are reduced. Besides, the self-propping fracturing fluid could enter any narrow fracture, increasing the effective propped area. All experimental results proved that the novel fracturing fluid has potential use in conventional reservoir fracturing and unconventional reservoir network fracturing.