Experimental Research On CO₂ Transport In Unsaturated Zone

As a new way to dispose CO₂ more and more people pay attention to Carbon Dioxide Ground Storage.Also we should take a full consideration in the risk and jeopardy it may cause.Unsaturated zone connect to the ground and underground which is closely related to human's life.This paper study the migration of CO₂ gas in the unsaturated zone under a background of gas leakage from CGS and migrates into vadose zone.As we design a whole set of apparatus which is use to simulate the CO₂ movement process in different situation.By changing the media,CO₂ inject pressure,CO₂ inject concentration and moisture content.Then discuss the different elements infects in escape process.Through build mathmatic model and work it out,it shows the same law and have a good fitness with measured valve.This model also vertify the viscosity resistance factor caculated by empirical equation.The main conclusions in study are obtained as follows.?1?There is no record for simulating the CO₂ migration by using independent development equipment.Whole equipment divided to five parts.There are CO₂ modulation system,supply and exhaust system,water supply and sewage system,testing column and monitor system separately.This equipment can running stably in different situations.All the data can be got in equal distance probes in the same time?2?The CO₂ migration form was controlled by pressure gradient.The higher pressure gradient products faster speed.The CO₂ concentration in same position would rise as the inject pressure rise when it is at dynamic balance.Concentration shows subordinate influence to CO₂ movement.The diffusion was enhance near-surface and the CO₂ concentration changed fast.The media's size and moisture content changed the media's porosity.The concentration would rise in the same position as porosity become small.The moisture content shows greater influence in gas movement.?3?The CO₂ runs smoothly in homogeneous media and pressure gradient shows linear relationship.The CO₂ concentration change rate was slow in near-surface because diffusion effect strengthened.Heterogeneous media controls gas movement by grain size.Fine particle medium has more obvious control over the migration of the gas than coarse particle.As gas enter into coarse particle from fine particle,the concentration in same position increase at same trend around the ground surface,particularly above 0.5m depth of soil that we can observe the CO₂ concentration rising significantly.?4?Building a mathematic model to simulate the CO₂ intrude vadose zone.Comparing the simulated result with the measured value,they shows the same law and fit well.It is convinced that this model is suitable for studying CO₂ migration in unsaturated zone.Equally,it also can be used to evaluate the risk in gas transmission pipeline.