Thermoresponsive Bentonite/Cyclodextrin Gel for High-Temperature Temporary Plugging

A snap-gate bentonite/β-cyclodextrin (B-CD) gel with thermoresponsive gating (102–137 °C) and acid-controlled unplugging capabilities that can be “switched on” at 200 °C is presented for on-demand temporary plugging of ultrahigh-temperature fractures. The material targets the dual challenge of fluid loss control and subsequent cleanup in tight-reservoir stimulation. A 30 min free-radical grafting route (65 °C, MBA cross-linker) yielded a clay–polymer network characterized by XRD, FTIR, SEM-EDS, rheometry, and HP/HT flow cells up to 200 °C and 4 MPa. The gel collapses cake porosity from 5.4% to 0.07% within 5 min, creating <0.5 μm throats and a breakthrough pressure of 4.1 MPa. Viscous modulus remains >65% after 72 h at 200 °C. Core-flooding (1.12 mD shale) extends plugging duration to 48 h and lowers permeability to 5 × 10 –3 mD. In a Sichuan field trial (4500 m, 98% water cut), 50 t of gel raised injection pressure by 2.9 MPa and delivered 35% cumulative oil gain in 90 days while water cut dropped 1.3%. Network disintegrates spontaneously at pH < 5, restoring 82% original permeability─no mechanical clean-out required. The study provides a rapid, reversible, and scalable chemical-engineering tool that can be dropped into existing water-flood lines without extra surface equipment, offering an immediate high-temperature plugging solution for enhanced oil recovery.