Research advances on the in-situ pressure-preserved coring and gas parameter determination for deep coal seams

The in-situ gas pressure and content of coal seams are critical for the safe production of deep coal mines and the accurate evaluation of coalbed methane resources. To address the technical challenges of accurately determining in-situ gas content in deep coal seams, this study proposed brand-new principles of in-situ pressure coring and the tests of in-situ gas content and pressure. It also derived a calculation method for in-situ gas content in coal seams and a method for determining the in-situ gas pressure while considering the effects of moisture content and multiple gas components. Given the in-situ stress environment deep in mines and the demand for multi-direction coring, this study introduced independently developed pressure-preserved controllers using gravity, elastic force, and magnetic force. The authors of this study also independently developed a set of technology and equipment that integrates low-disturbance pressure-preserved coring and the gas content tests of samples. This set of technology and equipment allows for in-situ sample transfer, pulverization, and tests that are integrated with the pressure-preserved coring device and can unlock the coring device. This avoids gas escape and loss during in-situ coring and sample transfer, thus significantly improving the accuracy of the gas content determination. This study provides theoretical and technical support for accurately determining in-situ gas pressure and content in deep coal seams, aiming to reduce gas accidents and enhance the mining efficiency of mines with high outburst risks.