Study On Gas Occurrence Regularity Of No.4^-2 Coal Seam In Jiao Ping Mining Area

Jiaoping mining area is a rare mining area of China in which coal,oil and gas associate, the large amount of coal gas emission which have a large fluctuation range with the conducting of coal mining activities becomes the main factor that restricts mine safety and efficient production. Studying 4- 2 coal gas'storage characteristic from the point of gas geology is important guarantee of gas controlling of the mining area.Through analyzing physical parameters of coal seam and its surronding rock,gas materials from production and test, studied the basic characteristics of mining area of southern Jiaoping (Chenjiashan and Xiashijie) about gas occurrence. According to regional tectonic evolution theory, studied the control law of structure and its evolution to gas occurrence. It is concluded that: (1)Gas distribution is obviously consistent with the main fold distribution in this area; (2)Syncline axis part have higher gas content, while anticline is opposite; (3)Mining area located in the Ordos Basin which is a stability rigid block, to some extent offsets the effect of structural changes, that's why the main construction in this area is relief-fold, but multi-period structural changes made small faults, fissures developed over the region; (4)Roof rock stratum of coal seam lead to that immediate roof can not form an effective seal on the coal seam, meanwhile made main roof become good gas layer. Seam,immediate roof and main roof constitute a unity gas-bearing reservoir.On this basis, analyzed the actual condition of mining area using grey association theory, and finally got the relevant degree and relational series between each factor and coal gas content. Determined the main factors affecting coal-bed gas content, There are: oil intensity of the roof of coal seam,the thickness of coal measure above the roof of coal seam and sandstone under Zhiluo Formation which reflects sedimentary sequences, also the sandstone and mudstone ratio of the coal-bed top which reflects variation of depositional environment.Applying the method of Geographic Information Systems to forecast coal gas content and its distribution of mining area. Combined layers stacking technology of GIS and fuzzy mathematics evaluation method, establish coal seam gas content forecast method based on GIS. First, establish fuzzy evaluation system based on the idea of fuzzy mathematics, achieve processing of data and building database, and then integrate layers stacking technique into the evaluation system, establish GIS evaluation system of coal seam gas content. Finally, complete the forecast to coal gas content and distribution of the study area.