Study On The Control Effect Of Tectonics On Coal Seam Gas Occurrence And Prevention Techniques In Huaibei Mining Area

Huaibei mining area is one of the largest coal production bases in our country.There are abundant coal resources in the area,mainly including fertilizer coal,gas coal and coking coal.The complex and varied tectonic movement forms and the resulting differences in coal formation conditions in Huaibei coalfield have created complete coal types at present,but also brought great differences in gas occurrence and gas disasters.Based on the actual geological data and gas data of Huaibei mining area,this thesis systematically studies the control effect of geological structure on coal seam,gas occurrence and gas disaster by combining theoretical analysis,laboratory experiment and field practice.The main research results are as follows:1.The Huaibei coalfield was deposited in the Carboniferous and Permian period.The coal seams of Shanxi Formation are 10#,11#(lower group coal),5#,6#,7#,8#,9#(middle group coal)and 1#,2#,3#(Upper group coal).After the formation of coal seam,there were three major tectonic movements,which were nearly-SN extrusion in Indosinian period,forming nearly-EW trending fault structure.The squeezing of NWW-SEE direction in early Yanshan formed the Xushu arc structure.A large number of NNE-SSW directional normal faults were formed during the extrusion of NNE-SSW in Late Yanshan Epoch.2.The Huaibei mining area can be divided into four mining areas: Zhahe,Suxian,Linhuan and Guoyang,among which the Zhahe and Suxian mining areas were mainly controlled by Xushu thrust napper,while the Linhuan mining area was mainly characterized by fracture network,while the Guoyang mining area was mainly characterized by barrier and graben combination.Influenced by Yanshanian magma intrusion,the coal metamorphism in Zhahe mining area and Linhuan mining area is relatively high,and some coal seams reach the grade of lean,lean and anthracite,while others are dominated by gas and fat coal.3.The occurrence of gas in Huaibei mining area varies greatly,showing an overall trend of high in the south and low in the north,high in the east and low in the west.After the Late Cretaceous,the north wall of the Subei fault rose and the south wall fell,which controlled the Paleogene deposition and formed a pattern of high gas occurrence in the south and low in the north.The Suxian mining area in the southern part of Subei fault has good gas trap conditions in the southern part of Subei fault and the southern part of Sudong syncline,and the coal seam has the highest gas content and the most serious outburst risk.The fault structures,especially normal faults,were the most developed in Linhuan mining area.Influenced by magmatic intrusion and red bed coverage,gas occurrence in Linhuan mining area was different,but lower than that in Suxian mining area.The Guoyang mining area experienced the process of large uplift and then decline,and a large number of normal faults were developed at the same time.4.The coal and gas outburst in Huaibei mining area concentrated in Suxian mining area and Linhuan mining area.Influenced by overthrust and nappe,Suxian mining area suffered serious damage to coal seam and developed structural coal with high gas pressure and content.The outburst in Linhuan mining area was influenced mainly by the intrusion of magmatic rocks.The high temperature baking and extrusion stress of magmatic rocks reformed coal bodies and hindered the migration of gas,thus forming high gas conditions.According to the occurrence and actual outburst of gas,the 8 and 9coal seams of Luling Coal Mine are defined as strong outburst coal seams,and the other coal seams are generally outburst coal seams.5.The gas treatment of strong outburst coal seam follows the principle of step by step.Firstly,the gas pressure and gas content of coal seam are reduced by ground well fracturing and pumping,and the strong outburst coal seam is transformed into general outburst coal seam;Then,the protection layer mining and surface drilling are carried out to strengthen the extraction of pressure relief gas,completely eliminate the outburst risk of strong outburst coal seam.Finally,in the mining process of strong outburst coal seam,the use of bedding drilling,roof strike drilling,directional long drilling,ground L well,etc.,to ensure the safety of the mining process.6.At present,the gas control in Huaibei mining area adopts the form of both underground and surface.For the underground area,regional pre-drainage or pressurerelief drainage is mainly carried out through cross-measure borehole,regional predrainage or in-mining drainage is carried out through in-seam borehole,and in-mining drainage is carried out through roof strike high level borehole and directional long borehole.On the surface,vertical well fracturing and horizontal well fracturing are used to advance coalbed methane production,and L-shape well is used to extract fractured zone in the production.With the development and progress of surface well technology,gas control in mining areas is mainly transitioned to the well,with surface horizontal well and surface L-shape well becoming the main forms,and a small number of bedding drilling or directional long drilling are constructed underground.This thesis has 55 figures,21 tables and 88 references.