Flow,heat Transfer And Phase Behavoir Of CO₂ Involved In CO₂ Transport,storage And Utilization

Carbon Capture,Utilization and Storage（CCUS）technology has attracted many attentions due to the contribution to lowering CO₂ emission on a large scale.This thesis investigates flow,heat transfer and phase behavior of CO₂ in the transport pipeline,injection well and reservoir by experimental measurements,theoretical analyses and numerical simulations.The results are important for the design and safety control of CO₂ transportation,injection and utilization on a large-scale.An experimental study and theoretical analysis were conducted on CO₂ leakage from high-pressure transport pipeline to the atmosphere.The phase behavior of CO₂during the leakage and the cooling effect in the pipe after suddenly closing the valve were measured and analyzed.Multi-phase formation,water hammer effect and highly underexpanded jet structure were observed using visualization measurement facilities such as schlieren apparatus and high-speed camera.The pseudo-steady state injection and transient shut-in and start-up operations of CO₂ injection well were numerically simulated and theoretically analyzed.Four factors were found to contribute CO₂ temperature increase along the wellbore:heat extraction from surrounding rocks,natural convection of the annular fluid,potential energy change of CO₂ and compressibility of CO₂.Simulation was carried out to quantify the proportional contribution of each factor to CO₂ temperature increase.The pressure balance relationship of CO₂ in the wellbore was proposed and CO₂ equivalent density was obtained.The mechanisms of CO₂ temperature and pressure decline at the wellhead during well shut-in and start-up operations were analyzed and the optimal transient operation for minimizing low-temperature damage was proposed.An experimental investigation on the natural convective heat transfer of the annular fluid in the injection well was carried out.The fitted correlation of natural convective heat transfer of fluid in the vertical annulus was obtained.The fitted correlation of the overall averaged natural convective heat transfer of the annular fluid and correlations at different circumferential positions were obtained for the inclined annulus with an angle of 30^o compared with the vertical line.The calculated equivalent thermal conductivity and net effect parameter of natural convection of the annular fluid were presented.Knowledge of phase behavior and thermodynamic properties of mixtures containing hydrocarbons,CO₂ and water under reservoir conditions plays an essential role in the design and operation of CO₂ storage and utilization processes.Experimental data of phase equilibrium of the（toluene+CO₂+water）system in the region where three fluid phases coexist at temperatures from 338.15 to 413.15 K and at pressures from 3.03 to 16.36 MPa were obtained and the isothermal triangular phase diagrams were plotted.The critical opalescence phenomena at the critical point between the toluene-rich and CO₂-rich phases were observed.Results showed that the presence of CO₂ significantly increased the toluene solubility in the water-rich phase.Experimental data of pH for CO₂-saturated NaHCO₃ solution at pressures from 0.2 to 15.35 MPa at temperatures from 308 to 353 K were reported and the results were compared with the geochemical equilibrium model.The results provided fundamental thermodynamic data for the completion of the database after CO₂ injection in the reservoir and were helpful for the large-scale simulation.