Experimental study on the updated selection criterion for particle size distribution of lost circulation materials

Abstract Fractures are a double-edged sword in energy applications, which can lead to fluid loss and reduced efficiency in some cases. Bridging plugging is one of the most commonly used methods for controlling working fluid loss in fractured formations. The size and particle size distribution (PSD) of the lost circulation materials (LCMs) are critical factors influencing the success rate of bridging plugging. However, existing methods for designing the PSD of LCMs remain controversial. Through an applicability study of fracture plugging using an experimental device for bridging plugging, this study conducted dynamic fracture plugging experiments under millimeter-scale fracture widths with various PSDs and established optimized rules for the PSD of LCMs. The results indicate that the ratio R of bridging particle size D 90 to fracture width ranges from 0.5 to 0.75, and with PSD coefficients S 90 ≥ 1.6 and S 75 ≥ 1, forming a dense plugging zone with high bearing capacity. Experiments on optimal material concentration, involving different types of LCMs, revealed that the suitable ratio for rigid particles, elastic particles, and fiber materials in on-site plugging operations is 2:1:0.15. Compared to existing PSD rules, the plugging particles formulated using the rules proposed in this study create a plugging zone with the highest pressure-bearing capacity (PBC) and result in relatively low cumulative fluid loss. The findings can provide theoretical guidance for optimizing plugging formulas for both energy extraction and storage in fractured subsurface formations.