A Calculation Method of CO2 Storage Capacity in Low Permeability Reservoirs Based on"Four-zone"Method and Its Application
CO2 flooding and storage have the potential to significantly mitigate greenhouse gas emissions and contrib-ute to achieving carbon neutrality objectives.Nevertheless,current methods for calculating CO2 storage capacity primarily concentrate on rough estimates of static CO2 storage,neglecting variations in CO2 storage during actual production processes.In view of the above problems,the process of CO2 flooding and storage is divided into gas phase zone,two-phase or near-miscible phase zone,diffusion zone and oil phase zone by using CO2 dissolution,CO2 swept volume and oil displacement mechanism.Based on the four-zone method,the CO2 storage capacity is calculated,and the dynamic CO2 storage capacity under varying hydrocarbon pore volume multiples,injection pres-sure and gas injection rate is obtained.The research results are applied to the low permeability reservoir of W oil-field.The results show that the pore volume multiple,pressure and gas injection rate of injected hydrocarbons are positively correlated with the total storage capacity.When the pressure increases from 12 MPa to 30 MPa,the total amount of CO2 storage increases by 15.53×104 t;when the gas injection rate increases from 5 t/d to 30 t/d,the to-tal amount of peak CO2 storage increases from 3.51×104 t to 12.62×104t.The research results can provide new i-deas for the development of CO2 flooding and storage projects in similar reservoirs.
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