Study on the efficiency and mechanism of the active flushing fluid system for large-size borehole cementing

Abstract:

To address the challenge of poor cementing quality caused by low filter cake removal efficiency under large-diameter borehole annulus conditions with low return velocity， this study employs a high-temperature， high-pressure dynamic cleaning apparatus to evaluate the effectiveness of active flushing fluid. Experimental investigations focus on three key parameters： mixing ratio， flushing velocity， and formation permeability， with particular emphasis on enhancing slurry strength， improving flushing efficiency， and promoting interfacial bonding strength at the second interface， moreover， scanning electron microscopy analysis was conducted to examine the cement-formation interface after flushing. The results are as follows： （1） the active flushing system achieves over 100% improvement in slurry strength compared to conventional flushing fluids； （2） with 95% filter cake removal efficiency， the active system shows significantly superior performance compared to water-based and conventional flushing systems； （3） after different velocity simulation， the active flushing fluid achieves over 90% flushing efficiency under low-velocity. The field applications confirm that the active flushing system effectively enhances both slurry strength and secondary interfacial bonding quality， thereby substantially improving cementing quality in large-diameter wells， indicating promising practical potential.