Study On The Development Types Of CBM Reservoir In Hegang Basin And Jixi Basin

This study is expected to explore a new method for CBM reservoir estimate from the view of CBM development based on the main coal seams in Hegang Basin and Jixi Basin.The changing rules of different reservoir characteristics and the indicative function to CBM reservoir are analyzed through geological analysis,descripition,experiment and fuzzy mathematics.Beisides.it is natural to define the CBM reservoir and classify the types of CBM reservoir based on the analysis of deictic function for reservoir characteristics to certain CBM reservoir.At the same time,the evaluation system and standard is established for judging the CBM reservoir in study area.Finally,the suggests for the study area are given to choose proper development models for different CBM reservoir.With the damage aggravation of coal,the solid coefficient of coal is reduced but increase in free radicals concentrations.At the same time,the number of exogenous pore are also increased,which lead to the increase of total volume,macropore and mesopore.The experiment of physisorption apparatus shows that the volumes and pore surface areas in micropore are increased a lot,resulting a stronger adsorption capability and storage capability.These parameters of pore reflect different CBM reservoir has different reservoir characteristics.Besides,the hard coal with higher ratio of critical desorption pressure and reservoir pressure,higher gas saturation,higher permeability and higher reservoir pressure gradient is more suitable for the development model of drainage and pressure lowering.However,the soft coal has the opposite reservoir parameters,which are the disadvantages for CBM development in-situ condition,but in fact,it is possessed of higher permeability,higher desorption ability and higher diffusivity when crustal stress is released.So,the CBM reservoir in coal can be developed effectively through mining and pressure unloaded and also represent another kind of CBM reservoir.The CBM reservoir characteristic and its development model shows some differentiation because of coal body structure.So,it is obvious that the CBM reservoir can be classified four kinds of types based on hard coal and soft coal,including type I of reservoir pressure can be transmitting freely in wide-range,type II of reservoir pressure can be transmitting freely in a wider range,type III of reservoir pressure can be transmitting freely in local range and type IIII of reservoir pressure can be transmitted freely only in a very small range.Then the index system and standard are eatablished for CBM reservoir estimate based on the solid coefficient of coal,free radicals concentrations of coal,langmuir volume,ratio of critical desorption pressure and reservoir pressure,desorption efficiency,gas saturation,permeability,langmuir pressure,diffusivity and reservoir pressure gradient.It is easy to have judged the CBM reservoir of sampling mine in study area on the basis of system and standard.Finally,some suggests about development models are proposed for the different CBM reservoirs in study area.