Discrete element simulation and dimensionless parameter-based optimization of near-wellbore fracture propagation during perforation fracturing of tight sandstone.

Abstract

Perforation fracturing is essential for stimulating unconventional reservoirs such as shale and tight sandstone. However, field monitoring techniques has revealed that many perforation clusters contribute little to post-fracturing production, indicating inefficient fracture initiation and limited stimulation effect. This study conducts a sensitivity analysis of key controlling engineering parameters for perforation fracturing based on the discrete lattice method, and introduces theoretically derived dimensionless parameters to bridge the gap between numerical simulation and multi-parameter engineering optimization. Single-cluster simplified perforation fracturing models under different perforation patterns are established to describe mesoscopic cross-scale fluid-solid coupling during fracture initiation and propagation, and are validated against near-wellbore simulation results and experimental observations. After model validation, a single-stage multi-cluster fracturing model is developed based on the validated model to reveal the competitive propagation mechanisms and geometrical evolution patterns of multiple fractures. The study found that helical perforation can produce the highest breakdown pressure and the largest volume of initiated crack compared to directional and fixed-plane perforation. Increasing the helical perforation diameter and perforation depth while reducing the perforation density can reduce breakdown pressure, increase stimulated reservoir volume (SRV), and reduce SRV standard deviation. For a fixed stage length, cluster length, cluster spacing, and cluster number have limited effects on breakdown pressure, whereas increasing cluster spacing and cluster length can reduce SRV standard deviation. Through quantitative statistics of simulation results and theoretical analysis, this study clarifies the relationships among dimensionless engineering parameters for the target sandstone reservoir and develops a construction optimization scheme, providing technical guidance and theoretical support for perforation fracturing in tight sandstone horizontal wells.