Study on Flowback Characteristics and Parameter Optimization of Fracturing in Tight Gas Reservoirs: A Case Study of Shenmu Gas Field, Ordos Basin

The flowback stage after fracturing in tight gas reservoirs is a critical phase influencing stimulation effectiveness. Factors such as flowback rate and flowback duration significantly impact the final fracturing flowback performance. Based on geological evaluation of tight gas reservoirs and engineering characteristics, this study investigates the effects of choke size, tubing/casing pressure, and flowback time on flowback efficiency, conducting flowback performance evaluation and parameter optimization research. According to choke and pressure variation patterns, the post-fracturing flowback process in the study area can be divided into three stages: controlled flow period, initial open-flow period, and shut-in flow period. The dynamic flowback characteristics in the study area manifest as three types: early-stage flowback, late-stage replenishment, and continuous flowback. The initial open-flow period represents the main flowback phase, while the shut-in flow period serves as a supplementary stage. Key parameters during the controlled flow period—including choke size, pressure, and duration—are crucial for flowback effectiveness. Optimization results indicate: The optimal controlled flow duration should be 6.0–9.0 h with properly sized chokes Wellhead pressure before open-flow should be maintained ≤3.0 MPa; Recommended open-flow duration should not exceed 75 h with injected fluid volume <1000 m3; The shut-in flow period should last 50–240 h, terminating when three consecutive shut-in operations show no significant flowback volume changes. The proposed multi-stage collaborative flowback parameter design methodology provides valuable guidance for enhancing flowback efficiency during tight gas reservoir development and production.