Sensitivity Analysis Of Heat Transfer During Carbon Dioxide Injection In Wellbore And Storage In Saline Aquifer

CCS can help significantly reduce the net carbon dioxide emissions during the utilization process of fossil fuels, so that it becomes the technology as a bridge to connect the economic transformation to the future substantial energy. However, carbon dioxide geological storage is challengeable facing some problems from safety, environment and cost. Heat transfer is one of the vital factor which has great impact on the phase change of carbon dioxide, the leakage risk in storage reservoirs and storage efficiency in CCS process during the carbon dioxide injection and storage procedure. Therefore, the sensitivity analysis of heat transfer is the way to control the flow and change of carbon dioxide. So, this paper introduced simulation method to develop models and code to conduct the analysis.By developing the wellbore heat transfer model and saline aquifer heat transfer model and programming to conduct simulation tests, a thorough analysis was performed on each sensitive factor including injection conditions, geological parameters and Joule Thomson coefficient to find the flow and heat-transfer pattern of carbon dioxide during the injection and storage process.During the injection stage, there were two main findings.1) The distribution of fluid temperature had close relation with wellbore structure, earth temperature and change of Joule Thomson coefficient. Relative high injection pressure and temperature could make the temperature decrease a lot and densities of carbon dioxide be through a drastic pattern, which was absolutely against the fluid injection; 2) In Joule Thomson cooling tests, the maximum temperature drop by cooling effects was up to nearly 10K, which made the carbon dioxide phase change from super critical to liquid and add the risk of pressure change dramatically in injection wellbores. Therefore, it is necessary to take Joule Thomson cooling effects into consideration in the analysis of wellbore heat transfer.During the storage in saline aquifer, there were three main findings.1) The relative low temperature, high pressure and long injection time could expand the temperature cooling zones which was bad for the flow of carbon dioxide in porous media and decrease the injection of reservoirs; on the other hand, the impact of injection rate most influenced the maximum temperature drop. The higher the rate, the larger of the temperature drop was. So the phenomenon increases the possibility of the generation of carbon dioxide hydrate and reduces the permeability of reservoirs. The equation describing the relation of injection rate and maximum temperature drop was given in the specific sections; 2) The geological parameters, porosity and permeability, have reverse impact on the maximum temperature drop. With increasing permeability, the maximum temperature decreased, while the pattern for porosity was opposite. Comparatively, with the porosity dropping, the temperature remained positive, considering the model hypothesis, which indicated that permeability had greater influence on Joule Thomson coefficient; 3) without Joule Thomson coefficient, the temperature was higher than the one considering it. The simulation results showed, Joule Thomson cooling effects could possibly change the phase of carbon dioxide and the generation of carbon dioxide hydrate.