Research On Gas Distribution Rule And Grading Units For Gas Extraction Of K₁² Coal Seam In Liziya Mine

Gas is a gaseous state geological body produced in the process of coal formation,and its occurrence and distribution in coal seam is controlled by geological processes.Accurate reveal of the distribution and occurrence regularity of coal seam gas is a precondition for the prevention and control of gas disaster and effective extraction of seam gas.The study object of this paper is Liziya Mine in Huayingshan Mining area in Sichuan Provine. Based on the theory of gas occurrence controlled progressively by geological structures, this paper makes a deep study on the geological tectonic evolution and tectonic stress field characteristics. Furthermore, this paper also analyzes the affact of regional structure and tectonic stress field on gas occurrence in different period.According to the characteristics of geological structure and gas data of Liziya Mine, this paper studies the geological factors which affects coal seam gas occurrence, including geological structure, coal thickness and structure change, buried depth of coal seam and thickness of coal seam and bedrock, coal seam occurrence, adsorption of coal, geologic history of strata. This study shows that the main factors influencing the K12 coal seam gas occurrence is the buried depth of coal seam and the geological structure. Meanwhile,according to the actual gas measurement of the mine, this paper established a corresponding relation between the buried depth of coal seam and gas content,predicated the gas content of coal seam K12 in Liziya Mine, and established the gas geological map of K12 coal seam.What’s more, this paper also studied the influence of natural factors on gas extraction. K12 coal seam is divided into 8 parts of gas extraction mainly according to gas content and geologic structure, and the gas resource and its abundance of each part is calculated. Based on gas occurrence and geological structure, 6 indicators of are selected for gas extraction block evaluation with the grey clustering analysis method.Finally we come to the conclusion that: block 3 and block 4 are classified into Grade I with better exploitability, block 2 into Grade II with medium exploitability, block 1,block 5 and block 6 into Grade III with poor exploitability.