A lightweight pressure- and gas-preserved coring tool for accurate gas content measurement in deep coal seams

Abstract

Accurately quantifying coal seam gas content is essential for disaster prevention, efficient resource management, and the advancement of sustainable and environmentally responsible mining practices. However, conventional methods struggle to preserve in-situ gas conditions and rely on empirical loss gas estimations, introducing estimation errors. This study proposes a pressure- and gas-preserved coring principle, emphasizing the benefits of maintaining in-situ pressure and water environments to stabilize gas occurrence states. The principle underscores that utilizing pressure-preserved coring technology for sampling, transferring, and storing high-fidelity coal cores can effectively eliminate errors arising from estimation-based gas content calculations. To implement this principle, we present an innovative lightweight pressure- and gas-preserved coring tool, specifically designed for deep coal seam sampling in confined underground environments. The coring tool features a high-strength threaded structure validated through 3D mesh simulation, a self-sealing pressure chamber, and a time-separated waterway, enabling stable sample retrieval, storage, and transfer under in-situ conditions. Comprehensive laboratory testing and field trials in underground coal mines confirm the tool’s effectiveness. Capable of operating in both horizontal and vertical boreholes with a 95 mm aperture, it reliably extracts high-quality 40 mm diameter coal cores under a maximum environmental pressure of 26 MPa. These advancements significantly enhance the accuracy of coal seam gas content assessments, reduce reliance on empirical loss gas estimations, and promote safer, more environmentally friendly mining operations.