Occurrence and Geological Controls of Coal Mine Gas in Hujiahe Well Field of Binchang Mining Area

Based on geological exploration, gas parameters testing and underground mining data, the geological control factors of the gas occurrence in Hujiahe Coal Mine are synthetically analyzed from the aspects of geological structure, lithology of the coal seam roof, buried depth of coal seam, overlying bedrock thickness, coal seam thickness and coal scouring zone. The research shows that the dry ash-free gas content of Hujiahe Coal Mine is between 0.02 m³/t and 5.71 m³/t with an average of 2.87 m³/t. The relative enrichment zone of gas is mainly distributed in the northern and southern of the coal mine. The main gas zoning is mainly nitrogen-methane zone. However, due to the use of top-coal caving technology, the mine has been identified as a high-gas mine for many years since it was put into production. The gas distribution in the area is mainly controlled by the geological structure, and the lithologic seal is easily formed in the anticline and syncline wing zones. The greater the effective bedrock thickness and the thickness of the coal seam over the coal seam, the more favorable the relative enrichment of gas. The influence of coal seam scouring zone on coal seam gas content is not obvious, but the coal bed scrub zone contains a large amount of free gas, which can easily increase the gas emission during the coal mining process of coal mining, and should be taken precautions during mining and excavation.