Preparation and Performance of Microencapsulated Sealing Material for Coal Mine Gas Drainage

Abstract

The performance of coal mine gas extraction borehole sealing material plays an essential role in the efficiency of gas extraction. Microcapsule technology was proposed to delay the expansion time of sealing materials to address the ineffective expansion of cement-based sealing materials in hydration. Based on conventional cement-based sealing materials, delayed-expansion microcapsules were prepared by phase separation with ethyl cellulose (EC) as the capsule wall material and montmorillonite (MMT) as the core material. A single-factor experiment showed that the delayed-expansion microcapsule had the best comprehensive effect when the EC content was 3%, the stirring rate was 400 rpm, the MMT content was 3.5%, and the core–wall ratio (CWR) was 10:3. Second, the slow release effect of the cement samples under the action of microcapsules is remarkable through physical tests. In addition, the triaxial compression test results show better mechanical properties of the delayed-expansion sealing materials. Then, nuclear magnetic resonance scanning was applied to the coal samples injected with different sealing materials. It was found that the proportions of macropores and mesopores in the total pore volume in the coal sample at 50 and 100 mm from the borehole wall decreased by 12.28 and 11.82%, respectively, indicating that the delayed-expansion sealing material has a better sealing effect.

Environmental-Friendly, Long-Lastingly Moist Phase Change Gel with Tunable Cross-Linking Time for Effective Borehole Sealing

“…With the development of the coal industry into deeper areas with frequent gas outburst accidents and complex coal seam gas situations, effective borehole sealing is a simple strategy to eliminate coal mine accidents, reduce environmental pollution, and utilize the extracted gas resource. − Borehole sealing materials, which could block the borehole leaking channels and strengthen the rock surrounding the boreholes, occupy a dominant position in extraction efficiency and are related to the concentration and volume of extracted gas. , Accordingly, it is urgently desired to develop sealing materials with excellent sealing performance for high performance borehole sealing and improving gas extraction. Recently, abundant prominent research on mining sealing materials has been reported, − but it is still challenging to simultaneously realize low expense, environmentally friendly, superior fluidity and nontoxic, making them fail to seal the drill holes tightly, which severely limited the practical applications in high-performance sealing mine drilling holes. The borehole sealing materials comprised of polyurethane mostly possess high reaction heat, complicated operation, and short completed time, resulting in low construction efficiency and an increased mine risk.…”