Study on the Experimental Method for Evaluating the Seepage-Blocking Performance of Curable Plugging Materials

Summary Gas well safety hazards primarily involve shallow gas leakage and casing annulus pressure, which pose significant challenges in remediation due to high technical complexity, elevated costs, and operational risks. Uncontrolled gas migration through cement sheath defects or along weakened cement-rock interfaces can lead to formation crossflow or surface leakage, compromising well integrity. Permanent sealing of gas migration pathways is critical to prevent gas influx into the wellbore or adjacent permeable formations. Internationally accepted plugging materials must demonstrate ultralow permeability, long-term structural stability, and minimal shrinkage. While cement-based slurries remain the conventional choice, latex-modified cement systems have emerged as alternatives, though field practices in some regions still rely on basic cementitious materials. To address these challenges, we developed a high-temperature/high-pressure squeeze-injection testing apparatus to simulate downhole conditions and to reveal the action mechanism of the curable plugging material in the leakage channel. We propose an evaluation method of dynamic sealing performance of sealing materials based on the entropy weight method, and evaluate comprehensively the flow behavior and performance of four candidate materials in fractures with different widths. The results demonstrate that WellLock® resin outperformed time-temperature setting (TTS) resin, cement slurry, and resin-cement blends, achieving a viscosity of 45 mPa·s, a sustained pressure resistance of 20 MPa, and no degradation after 60 days of aging at 80°C. Its advantages in pumpability, high-pressure tolerance, and long-term effectiveness highlight the superior adaptability of resin-based materials for sealing gas migration channels. With this study, we provide a technical foundation for optimizing gas well remediation strategies.