Study on geologic control factors of gas occurrence in Lyutang Minefield of Qianbei Coalfield

In order to understand the gas occurrence law of Lyutang Minefield in Qianbei Coalfield,the paper had a study on the burial - hydrocarbon generation history of the mining seam and an analysis on the main geologic control factors of the gas occurrences. The results showed that the seam after the sedimentation in the study zone had three periodic tectonic evolution functions. Among them,the Indosinian tectonic deep burial depth and Yanshan Middle Period magma intrusion controlled the formation of the seam methane. The organic matters had two hydrocarbon generation processes,great methane were generated,the maximum vitrinite reflectivity of coal was 3.69%. The gas content was ranging from 5.43～28.93 m3/t and all seams were high gassy seams. The opening normal fault caused the gas migration and dissipation. The gas content of the coal was increased with the buried depth of the seam increased. The roof and floor of the seam mainly were the weak permeability mudstone,silty mudstone and siltstone and those stones could play a strong sealing function of the gas. The hydraulic connection between the different aquifers of the seam was poor and underground water activity would have a good sealing function to the dissipation of the seam gas.