Research on the plugging mechanism of shear thickening fluid in porous formations for energy geological drilling

Abstract:

To address the challenges of lost circulation control in porous formations during unconventional geo-energy drilling， as well as the shortcomings of traditional plugging materials such as poor adaptability and difficult performance control， a shear thickening fluid （STF） was prepared using nano-SiO? as the dispersed phase and polyethylene glycol as the continuous phase. Experiments were conducted using an API static plugger and marble beds to simulate porous formations， systematically investigating the influence mechanisms of three key parameters-critical shear rate， shear thickening intensity， and shear thickening ratio-on the plugging performance of STF. The results indicate that the critical shear rate dominates the pressure response characteristics and the timing of thickening triggering. Within the marble bed pore size range of 0.15~1.66 mm， samples with a lower critical shear rate readily triggered the thickening effect under low pressure， reducing the leakage rate to below 2 mL/min. The shear thickening intensity determines the compactness and ultimate pressure-bearing capacity of the plugging layer； samples with high shear thickening intensity achieved a minimum leakage rate of 0.38 mL/min and maintained excellent plugging effectiveness even under high pressure. The shear thickening ratio affects the stability of the plugging morphology and pressure sensitivity. A high shear thickening ratio facilitated the formation of effective "throat-plugging" or "waist-plugging" structures， reduced a low leakage rate of 1.71 mL/min at pressures exceeding 3.0 MPa and demonstrating good pressure-bearing capacity. This study reveals the mechanisms by which the core thickening parameters of STF affect pore plugging performance， providing theoretical support and a technical basis for its engineering application in porous lost circulation formations.