With the increasing mining depth of mineral resources, the temperature and pressure of the underground environment are also on the rise, which puts forward strict requirements for the performance of fidelity coring tools. To promote the development of such tools, a comprehensive high-temperature and high-pressure test platform for deep in-situ fidelity coring tools was constructed, and its working principle was described in detail. In addition, four key functional modules of the test platform were developed. On the basis of the principle of gas-liquid pressurization and the burst failure criterion of pressure vessel, a mechanical module integrating the functions of pressurization and pressure maintaining was designed. The heating and insulation module was developed by using a U-shaped high-speed heater and electromagnetic induction heating technology. The innovation utilized coil cooling technology to achieve effective cooling and pressure relief. Furthermore, the working performance of the test platform was studied experimentally. The designed test platform could run stably for more than 110 min under test conditions of high pressure and temperature of 140 MPa and 150 ℃, respectively, and it could maintain a stable pressure and temperature at 200 MPa and 160 ℃ for more than 182 min. Under the high pressure condition of 220 MPa, the pressure remained stable within 140 min, without any fluid leakage. Therefore, the test platform designed in this study can provide experimental conditions of high pressure and high temperature for the research of fidelity coring tools, which is of great significance for the accurate evaluation and safe exploitation of deep mineral resources.

The accurate measurement of coal seam gas content is essential for several aspects of deep coal mining, including disaster management, resource allocation and sustainability. However, obtaining in-situ coal samples while preserving gas content under challenging conditions, such as high stress, temperature fluctuations, and drilling fluid environments, remains a significant challenge. To overcome this difficulty, we present an innovative in-situ pressure- and gas-preserved coring tool specifically designed for deep coal mining applications. This device enables the collection of coal seam samples under in-situ conditions while ensuring that both pressure and gas content are preserved, thereby preventing gas escape during sample transfer and providing more accurate parameters for evaluating coal and natural gas reserves. In the demanding environment of deep coal seams, the performance of the pressure-preserved chamber of the corer relies on the reliability of its remote triggering mechanism. The presence of drilling fluid introduces medium resistance, which can impair the triggering process–an issue largely overlooked in previous research. Herein, we propose a robust method to calculate remote triggering forces within liquid media and optimize its key parameters to improve operational stability. Laboratory tests and field validations in coal mining environments are conducted, which confirm the effectiveness of the optimized design and demonstrate the tool’s practical applicability. This study offers valuable insights into addressing key challenges in deep coal reservoir exploration and gas resource preservation.

Using pressure-preserved coring technique to determine in-situ gas content provides a more precise assessment of gas resource reserves and safeguard of mining safety in coal seams. How coring technique and depth affect the determination of gas content is unclear due to borehole zoning rupture caused by roadway excavation and drilling disturbance. To this end, a proposed coupling model of stress distribution and gas migration was simulated and validated by FLAC^3D and COMSOL Multiphysics considering superposition effects of roadway excavation and drilling disturbance. The findings indicate that the roadway surrounding rock displays distinct zoning features including stress relief zone, stress concentration zone that is composed of plastic zone, elastic zone, and original stress zone; and the broken situations depending on the borehole peeping are consistent with the corresponding simulation results. On this basis, this study proposes a set of drilling coring depth calculation and prediction model for the gas desorption affected area under engineering disturbance. Optimal depth of coring drilling is not only approach to the in-situ coal bulk, but also can get the balance of the drilling workload and cost controlling. According to the typical mine site geological conditions and the numerical simulation results in this study, if the roadway excavation time is ~1 year, it is recommended that the pressure-preserved coring depth should be greater than 17 m.