Lattice Boltzmann Method Simulation Of CO₂/Brine Multiphase Migration In Random Porous Media

CO₂ storage in saline aquifers is considered as the most promising method for CO₂ geological sequestration and attracts wide attention of governments and research institutes owing to its widely distributed storage site and huge storage capacity.Understanding the CO₂ multiphase mitigation process in porous media is a significant basis to forecast the long-term CO₂'s storage capacity.The CO₂ multiphase mitigation phenomenon in porous media is a complex fluid dynamic problem related to multi-component multi-phase fluid flow in complex geometry,and it is influenced by various factors include the structure of porous media,surface wettability and fluid properties.The study of these factors on CO₂ /brine multiphase mitigation process presents a significant theoretical research value.Fluid properties and surface wettability are key factors that influence multiphase mitigation processes in the porous media.The simulation on the effect of various impact fators,such as capillary number?Ca?,viscosity?M?and surface wettability?contact angle ??,on CO₂/brine multiphase mitigation is carried out by the Lattice Boltzmann method?LBM?in the paper firstly.The result reveals: 1)Increasing Ca will reduce the breakthrough time of mitigation process when the viscosity ratio is constant,and enhance the CO₂ saturation in steady state;2)Enhancing M will enhance the breakthrough time and the CO₂ saturation in steady state when the inject velocity is constant;3)With the increasing of ?,the fingering phenomenon is more and more obvious,and the breakthrough time and CO₂ saturation in steady state are reduced.Pore structure heterogeneity in porous media is a key factor that controls the multiphase mitigation process of the CO₂ local storage.This paper adopts the method of four parameters to reconstructed the three-dimensional heterogeneous porous media,simulates the process of CO₂/brine multiphase mitigation in three-dimensional porous media by using LBM.The influence of regional dense pore structure in porous media on the CO₂/brine multiphase mitigation process has been analyzed,and we unite the macroscopic physical parameters to analyze the influence of capillary pressure on the CO₂ local accumulation phenomenon.The analytical results reveals: 1)The pore with small diameter and irregular shape has higher capillary pressure,and it cause that the mitigate path of CO₂ plume has obvious selectivity on the porous media,the CO₂ finger is prior to formed in the lower capillary pressure area;2)The high capillary pressure of dense layer cause the CO₂ local accumulation in the porous media,it is the dominated factor that influence CO₂ saturation's distribution in the whole porous media.