Numerical Simulation Of CO₂ Geological Migration And Sequestration In Jingbian Qiaojiawa Region

The burning of fossil fuels has caused a large amount of carbon dioxide emissions,which causing global warming to many ecological disasters.How to deal with the large amount of carbon dioxide emissions is urgent.Effective measures must be taken to achieve large-scale emission reductions of carbon dioxide in order to meet the urgent needs of sustainable economic and social development.At present,carbon dioxide capture and storage(CCS)has become one of the important carbon dioxide emission reduction technologies.The geological storage of CO₂ in sandstone reservoirs lasts for hundreds to thousands of years.If leakage occurs,it will threaten surface organisms,buildings,and human life.In the process of carbon dioxide injection into underground,the space occupied by carbon dioxide is the remaining space after the movable oil is displaced.The effect of carbon dioxide flooding is very obvious in reservoirs with higher permeability.The injected CO₂ states in a supercritical state,which has the characteristics of low viscosity,high density,and good fluidity.It is conducive to storage in the formation.Low permeability sandstone reservoirs have good CO₂ storage performance,but the storage scale is small.Therefore,it is very necessary to carry out CO₂ flooding,storage,migration and leakage risk assessment in low permeability sandstone reservoirs.This paper has a target on the low permeability sandstone reservoirs of the Yanchang Formation in the Qiaojiawa area of Jingbian,Ordos Basin.On the basis of the previous research,a three-dimensional geological modeling of the reservoir and cap rock was established through comparative modeling methods according to the stratigraphic data controlled by sedimentary facies.The reservoir numerical simulation method is used to study the characteristics of carbon dioxide migration,simulation the final state,and discuss the influence of stratum rock physical properties and particle size distribution on the geological storage and migration of carbon dioxide.The study found that CO₂ migrates in a typical plume shape in the reservoir,in both horizontal and vertical directions.The farther away from the wellbore,the less saturated CO₂is vertically,and it is mainly concentrated around the wellbore at the top of the storage body.CO₂ has a larger lateral transport range at the top than at the bottom.CO₂ is gradually moved upwards by buoyancy,and eventually gathers toward the top.The CO₂ saturation increased rapidly in the early stage of injection,but gradually flattened in the later stage.After the injection is stopped,the horizontal migration of CO₂ plume is mainly driven forward by the diffusion effect caused by the difference in CO₂ concentration and the moving speed is slow.There are many factors that affect the migration characteristics of CO₂ in the reservoir,such as formation thickness,porosity,permeability,pressure,salinity and so on.The main driving force of CO₂ migration comes from the density difference between the CO₂ dissolved in the formation water and the original formation water.The migration path is mainly affected by the distribution of rock properties.There is a high correlation between the CO₂concentration in the formation and the porosity.When the injection is stopped,the binding storage mechanism and the dissolution storage mechanism are still in effect.The influence of permeability on various parameters is mainly reflected in the initial stage,which mainly affects the injection efficiency.It can increase the amount of carbon dioxide trapped in the reservoir and its dissolved amount.