Pore-scale Study On The Fluid Flow,Heat And Mass Transfer In Heterogeneous Porous Media

The reactive transport process in heterogeneous porous media is widely used in energy,environment and chemical industry fields,such as rock acidification,CO₂fracturing and storage under subsurface.The process involves multi-component fluid flow,heat transfer,mass transfer,chemical reaction and solid structure evolution.Based on the lattice Boltzmann method,a pore-scale model is established to simulate the coupled flow,heat and mass transfer process in simplified and complex porous media,in which the immiscible fluid flow,solute transport,heat transfer and solid structure evolution are solved by the Shan-Chen multi-component lattice Boltzmann model,mass transfer lattice Boltzmann model,heat transfer lattice Boltzmann model and VOP method,respectively.A high temperature and high pressure reaction system is designed and built to study the interaction between CO₂ and rock,and the pore-scale simulation is used to interpret and analyze the experimental results.Results show that the flow,heat transfer,mass transfer,immiscible phase distribution and solid structure evolution in porous media are highly coupled.The presence of immiscible phase can inhibit solid dissolution,reduce the temperature decreasement rate and increase the penetration depth of acid in porous media.The solid dissolution,temperature decreasement and acid total breakthrough rates increase with increasing immiscible phase saturation.The lateral distribution of immiscible phase facilitates the development of preferential channel in porous media.The heterogeneity of porous media has significant influence on the heat and mass transfer process.The existence of undissolved component around dissolvable solid component suppresses the dissolution process significantly.Increasing the porosity gradient of porous media promotes the solid dissolution and immiscible phase escape.The increasing velocity,concentration and temperature can accelerate the solid dissolution process.According to the reaction experiment between CO₂ and rock,as well as the mineral acid corrosion simulation at pore scale,it is found that the time required to reach reaction equilibrium is different in different reaction systems.The mineralization reaction between CO₂ and rock can change the pore structure and the mineralization degree of formation water,increase the rock porosity by 2.53%-5.54%.