Research On Gas Injection And Methane Drainage Numerical Simulation Of Low-permeability Coal Seams

China is a big coal industry country ,the coal-bed methane resources very rich,however,coal-bed methane reservoirs are low-permeability reservoir,which is different from the U.S coal-bed geological conditions,and the traditional coalbed methane exploitation methods are lower productivity,longer recovering period and poor economic are poorer.The direct consequences of low recovery ratio of coal-bed methane are gas disaster-prone,inefficient mining,resources waste and environmental pollution. based on the low permeability characteistic of most coal-bed and corrent ststus of low recovery ratio of coal-bed methane in china,the corbon dioxide enhanced coal-bed methane technology has been suggested for the purpose of enhancing coal-bed mehtane recovery ratio.Gas injection and methane drainage technology is considered a better prospect coal-bed methane exploitation technology.This paper applied the gas geology, multiphase gas seepage and diffusion, solid mechanics, numerical analysis theory in the summary of the existing research results of predecessors, based on the gas reservoir property, will double porosity coal abstracted as dual medium model of single permeability, studies the gas desorption, diffusion, percolation mechanism, and in research note gas extraction mechanism is established, on the basis of the dual medium coal seam gas injection extraction simulation of two-dimensional model of gas flow characteristic, and the changes were analyzed. Main obtains the research achievements and known as follows:(1) In combination with the actual, low permeability coal seam gas extraction gas injection is a kind of very effective means to be hurting the gas reservoir premise improve gas extraction effect, a hydraulic fracturing effect is good; (2) In the gas extraction in the influential factors, gas pressure gradient and concentration gradient is the important factors, gas recorery gas pressure gradient to remain in a certain range, can make more gas recorery out. (3) Establish a low permeability coal seam gas extraction gas injection, considering the model, without note gas extraction conditions and note gas extraction gas conditions, proved two conditions can improve gas injection gas extraction, and analyzes the effect of gas gas injection pressure and concentration of influence. Note gas extraction coal gas measures aiming at characteristics of low permeability and has a good effect.