Study Of CBM Reservior Properties In CiXi Area

Based on the existing coalfield geological data in western parts of Cixi area,I have studied the characteristics of CBM reservoirs,such as maceral components,coal rank,coal quality,sponginess,pore diameter distribution,specific surface area,adsorption and desporption characteristic,permeability,pressures of coal reservoirs by using theories such as coal and CBM geology,fuzzy mathematics,I have also analysed the control factors of CBM reservoir parameters.Recoverability of reservoir was evaluated using the fuzzy mathematics theory.First,through the laboratory analysis and analyzing the existing material,we obtain reservoir geological features.The research area is a fault-developed monocline.Hydrological geology condition is relatively complicated.Ro is between 1.35%and 1.48%;Vitrinite is a main maceral,inertinite take second place,exinite is less.Microlithotype is vitrite and inertite.Then,according to the mercury injection experiment,cryogenic nitrogen isothermal adsorption test,isothermal adsorption test and well test data,Reservoir physical properties were abtained,such as porosity,permeability,adsorption and desporption characteristic,pressures of coal reservoirs.Mercury injection experiment indicates that the reservoir is pore-fissure.Ealier stage is wide fractures,later stage is minute pore.Cryogenic nitrogen isothermal adsorption test indicates that pore structure of coal seam ?.The main pore is micropore and small pore.Pore size is between 3.4-4712.9nm.Pore value is between 0.0046 and 0.00146ml/g.Specific surface area is between 0.181m2/g and 1.840m2/g.Analysing the well test data,we know that the coal resevior is low permeability reservoirs,the desorption quantity is large,desorption speed is fast.Reservior is in anomalous pressure condition.At last,according to the evaluation system of CBM recoverability in Carboniferous and Permian coal seam of Northern China,using fuzzy mathematics theory,we get that fuzzy synthetical evaluation coefficient is 0.52.Reach area is hard to form industrial gas flow.