| Tectonic coal development zone refers to the coal seam type is givenpriority to with structure of coal. Tectonic coal is mainly due to the formation ofcoal under different degree of the effect of tectonic stress, resulting in a differentdegree of deformation, breakage, etc., its internal structure, mechanicalproperties, even the chemical composition change. The classification of tectoniccoal according to its structural characteristics can be divided into brittledeformation and brittle ductile transition deformation of coal and coal ductiledeformation of coal. Because of tectonic coal structure characteristics, leading toits internal micro pore development, provides favorable conditions for coalbedmethane reservoir, tectonic coal development area are generally areas of coaland gas outburst. Coal-bed gas is a clean energy on the other hand, can alleviatethe status quo of energy constraints, and coalbed methane is a greenhouse gas,serious damage to the ozone layer, if direct emissions into the air it will causeserious air pollution. So for coalbed methane development and utilization for the mine safety production, relieve the strain on energy and environmentalprotection is fully staffed. But low degree of industrialized production ofcoalbed methane exploration in China, the main reason is that low permeabilityof coal, coal bed methane output efficiency and yield is low.Especially thetectonic coal development zone high coal seam has the characteristics of thereservoir is low, so improve the permeability of coal seam, and improve theextraction efficiency of coal-bed gas, increase the output of coalbed methane isfirst this CBM development urgently needs to solve the problem.In view of theabove questions this article mainly done the following work.(1) Based on different types of tectonic coal (coal fracture, crushed grain ofcoal, coal scales and mylonite) mercury injection experiment was carried out,and get different coal samples of mercury injection curves, and by usingmercury injection curve analysis of different types of tectonic coal and porosity,pore structure for four kinds of porosity of coal sample size from big to small inthe order: mylonite coal coal>scales the broken coal> cataclastic coal. ThroughKozenny-Carman formula of calculation of different types of tectonic coalpermeability, through calculating the four kinds of permeability of coal samplesize from big to small in the order: mylonite coal>the broken coal>rupture scalescoal, has large discrepancy with actual, this paper argues that the main reason isthat the equation does not take into account of tectonic coal structure features,the factors that determine the permeability of coal size for coalbed fissuresystem development degree, and this equation is only considering the pore structure of coal, and does not take into account the coal cleat fissure system.(2) The use of CT scanning technology, this article respectively to thenative structure of coal, coal fragmentation and mylonite CT scans, get adifferent structure types of lump coal sample fracture space distribution andinternal structure. Through the results can be found in the three kinds of coalsample, the native structure of coal fracture distribution rules, face cleat cleatalmost positively pay distribution and end, but the internal crack width is small,resulting in poor communication; Cataclastic coal crack and endogenous systemvisible fractures, including endogenous fractures is more filling, fracturesfracture width, and the fracture width has obvious change; Mylonite damage tothe native structure of coal, the most serious distribution less coal to the internalcracks of coal instable development, crack width is small, have crumpled coaland rock deformation. So three since the childhood to arrange for thepermeability of coal sample, mylonite coal <primary structure coal <fragmentation of coal.(3) Using the self-developed coal adsorption and desorption of completesets of equipment, the structure of different types of lump coal sample, theadsorption desorption experiment for the isothermal adsorption curve ofdifferent coal samples and analytical curve, isothermal and analyze variousadsorption desorption law of coal samples, and their different structuralcharacteristics caused by the differences of different types of coal adsorptiondesorption. By comparing the different structure types of high rank CBM curve of coal seam is proposed the guiding significance of the trial of CBM extraction:mainly primary structure coal coal reservoir is not good for CBM development;Mylonite coal area of CBM development has yet to find a more reasonablemining method and technology; Is given priority to with coal fracture and scalesof coal reservoir, the gas content is high, the fracture system, goodcommunication is very beneficial to CBM development.(4) Through the establishment of mathematical coupling model, usingCOMSOL Multiphysics commercial numerical simulation software, respectivelyof downhole drilling and extraction of coalbed methane, the ground mining coalbed methane extraction of coalbed methane and the hot water injection threeextraction methods were simulated and the simulation results are compared.Simulation, the author found out that the underground extraction gas due tostress concentration phenomenon, near the borehole formation compaction area,has a negative effect on coal seam permeability, hindered the coalbed methaneseepage, adverse effects on the efficiency of coalbed methane extraction;Hydraulic fracturing method of mining exploitation of coalbed methane in lateextraction, extraction efficiency of this method will reduce gradually, also can’tefficient mining of coal bed methane; Hot water extraction of coalbed methane,through to the high temperature and high pressure water injection of coal seam,improve the coal bed temperature, promote the coalbed methane desorption, andimproves the permeability of coal seam, promoted the coalbed methane seepageis suitable for the high reservoir and low permeability of coal and coal-bed methane development zone construction. |
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