Development of a Shear-Responsive Gel for Lost Circulation Control Tailored to Enhance Drilling Rate of Penetration

Lost circulation of wellbore fluids within fissured zones constitutes a primary factor contributing to increased non-productive time (NPT) and restricted rate of penetration (ROP). Conventional gel-based lost circulation materials (LCMs) inherently suffer from a tradeoff between pumpability and in situ fracture retention, and they lack a design methodology quantitatively correlated with drilling engineering parameters. In this study, a shear-responsive gel with a dual physically crosslinked network—combining hydrophobic association and Fe3+-mediated ionic coordination—was prepared through a single-step water-based radical polymerization process, utilizing commercially available monomers. By systematically tuning the hydrophobic monomer and Fe3+ contents, the gel’s fracture-sealing efficacy, autogenous healing ability, and shear rheological characteristics were evaluated, establishing a quantitative correlation between the critical shear rate and drilling parameters. The empirical data demonstrate that with an increase in the hydrophobic monomer dosage from 0.4 wt% to 1.2 wt%, the critical shear rate decreases from 22.5 s−1 to 8.6 s−1, exhibiting an exponential decay relationship. The optimized formulation, G0.8F0.5, demonstrates a low initial viscosity of 245 mPa·s under high shear conditions, which surges to 6180 mPa·s at a shear rate of 14.2 s−1, achieving a thickening factor of 29.4. Upon incubation at 80 °C for a duration of 12 h, the formulated gel restores 94.9% of its mechanical tensile strength and 96.3% of its fracture strain, whereas the Fe3+-free control sample fails to heal. In dynamic plugging tests using a 3 mm fracture plate, G0.8F0.5 achieves a breakthrough pressure of 12.8 MPa with a minimal fluid loss of 98 mL. The LCM forms a monolithic gel block positioned at the middle-to-rear section of the fracture, outperforming conventional gel counterparts. Drilling hydraulics simulations reveal that deploying this gel reduces the annular equivalent circulating density (ECD) by 0.06 g/cm3. Furthermore, under idealized conditions, this approach is calculated to enhance the ROP by approximately 26%. The proposed molecular design of a shear-responsive, dual physically crosslinked network provides a viable technical pathway for quantitatively tailoring the shear-responsive properties of while-drilling LCMs.