Influence Of CO₂ Hydrate Formation On The Properties Of CO₂ Permeating And Flooding In Porous Media

Storage of CO₂ in seabed sediments is a potential method of mitigating climate warming,especially in the form of hydrate.In the seabed geological conditions of high pressure and low temperature,CO₂ hydrate is easily formed,which gets interstitial flowing pores choked,thus blocking continuous injection process.Hereby,glass beads were tightly packed in a fixed bed to simulate seabed sediments.Then CO₂ was injected into the fixed bed both in one-time and continuous injection modes.The effects of temperature,pressure,initial water saturation,particle sizes and inhibitors on hydration were investigated by injecting gaseous and liquid CO₂ into the packed bed for one time,and amounts of CO₂ hydrate were calculated.It was demonstrated that,the rate of hydration and hydrate conversion rate were reduced with water saturation range from 10% to 60%,the bath temperature ranging from 275 K to 279 K,the particle sizes ranging from 0.105 mm to 0.5 mm,or mass concentration of inhibitor ranging from 0.1% to 0.5%.Additionally,time of hydration equilibrium was prolonged on condition that mass transfer of liquid CO₂ got impeded in porous media,with relatively high pressure ranging from 8 MPa to 14.5 MPa,which suited the inhibitor-added system with pressure ranging from 6 MPa to 8 MPa.Therefore,hydrate formation was greatly influenced by mass transfer,especially when liquid CO₂ was injected into porous media.The process of CO₂ permeating and flooding in the packed bed was blocked because the rapidly formed hydrate might get pores choked,which in return impeded hydrate formation.It could be concluded that hydrate formation process and CO₂ permeating process were interacted.When liquid CO₂ was continuously injected in a constant flow rate,the influence of CO₂ hydrate formation on the injection process was investigated with injection directions,temperature and injection rates varied.When injected vertically downwards,more CO₂ was injected,and more water was ejected,with the injection rates increasing from 1 ml/min to 5 ml/min,while permeability increased though more hydrate was formed.When injected horizontally,less CO₂ was injected,and less water was ejected,with the injection rates increasing from 1 ml/min to 5 ml/min,and permeability increased because less hydrate was formed.Similarly,permeability increased when ambient temperature was raised from 277 K to 279 K,because hydration rate became slower.Injection directions might influence the layout and distribution of CO₂ hydrate in the porous media,when CO₂ was continuously injected into sediments.Hydration rate and dimensional distribution of CO₂ hydrate affected injection and permeating-flooding process of liquid CO₂.When liquid CO₂ was injected vertically downwards and injection rate was properly increased,more CO₂ could be stored in the seabed sediments,because the retroaction of hydrate formation on permeating process of liquid CO₂ was eliminated and blockage in the sediments was mitigated.