Study On The Storage Capacity Evaluation Methodology Of Injecting Supercritical CO₂ Into Anthracite Reservoir

Taking the Zhengzhuang block in Qinshui Basin as the research area,based on the No.3 coal of anthracite reservoir in the area as the research object,and combined with the actual geological parameters of Zhengzhuang block,the geological models of different units in the study area are established.Through the adsorption,displacement and solubility experiments simulation of injecting supercritical CO₂ into deep anthracite reservoir,the calculation models of adsorption capacity,free volume and water-soluble volume of supercritical CO₂ in the anthracite reservoir are initially established under the geological conditions.And the theoretical storage capacity and effective storage capacity of supercritical CO₂ in deep coal seam of Zhengzhuang block in Qinshui Basin are calculated and statically evaluated.The main results are as follows:（1）According to the actual geological characteristics of Zhengzhuang block in Qinshui basin,Zhengzhuang block can be divided into three calculation units,namely,three kinds of geological models: In model 1,the coal seam is buried deep and the geological structure is mainly composed of fold.In model 2,the structure is complex and the geological structure is developed includes folds and faults.In model 3,the buried depth of coal seam is relatively shallow and the geological structure is given priority to with fault.（2）It is found that under the high temperature and pressure condition,only the BET-3,D-R and Lattice equations can better characterize the adsorption characteristics of supercritical CO₂.Compared with the standard deviation,the result shows that the fitting degree of BET-3 equation is better.It is shown that the equation based on the Langmuir monolayer adsorption theory can not characterize the adsorption curve of supercritical CO₂ under high temperature and pressure,and also shows the adsorption of supercritical CO₂ under high temperature and pressure should be consistent with the multi-molecular layer adsorption theory.（3）Under the condition of coal reservoir,the increase of temperature or injection pressure are beneficial to improve the efficiency of CO₂ displacing coalbed methane.（4）According to the experimental datas of CO₂ solubility in water under high temperature and pressure,by comparing four widely used solubility calculation models（PR-HV model,Furnival model,Duan,Chang model）,it is found that under the condition of high temperature and pressure,the PR-HV model can better characterize the solubility characteristics of CO₂ in pure water or different mineralization water,especially in the case of high salinity water.The water-soluble volume of supercritical CO₂ in deep coal seam is a function of coal seam depth,water saturation,coal density and CO₂ solubility.（5）Based on the results of three experiments,the calculation model of supercritical CO₂ adsorption capacity,free volume and water-soluble volume were established.Through calculated the storage capacity of each model,it is found that the adsorption gas content is more than 80%,followed by the free gas content of about 15%,and the water-soluble content is less than 5%.The theoretical analysis shows that the establishment of the calculation of the phase storage model is reliable and consistent with the geological characteristics of Zhengzhuang block.