Study On The Migration Of Carbon Dioxide In Deep Salt Water Layer

Since the industrial revolution,the content of carbon dioxide in the air continues to increase,and carbon dioxide geological storage is an important means to achieve energy saving and emission reduction.The injection and migration of carbon dioxide changes the initial stress field and pore pressure field of the formation,which may lead to the surface uplift and deformation,and may also cause the formation of new fractures in the caprock,or cause the opening and dislocation of the existing fractures,which will affect the mechanical integrity of the caprock.Therefore,exploring the migration law of carbon dioxide in deep saline water layer will provide important technical support for carbon dioxide emission reduction.Taking Shiqianfeng Formation of Ordos Shenhua carbon capture and storage project as the research object,two-dimensional supercritical carbon dioxide salt water gas-liquid two-phase flow simulation and three-dimensional seepage mechanics coupling simulation are carried out.The influence factors of carbon dioxide plume migration in saline water and cap rock deformation are studied.The main research contents and achievements are as follows:(1)Considering the influence of temperature and pressure changes on supercritical carbon dioxide migration analysis,the density and viscosity of supercritical carbon dioxide were interpolated,and the function expressions of density and viscosity with temperature and pressure were obtained.(2)Considering the compressibility of carbon dioxide,the two-dimensional supercritical carbon dioxide salt water gas-liquid two-phase flow was simulated.The influence of different injection rate,formation confining pressure,reservoir temperature,reservoir porosity,salt water salinity and other influencing factors on reservoir pore pressure and carbon dioxide migration are studied.(3)According to the research results of influencing factors of two-dimensional gas-liquid two-phase flow simulation,the unfavorable factors are compared.The fluid solid coupling model of reservoir and caprock is established,and the coupling simulation of three-dimensional seepage field and stress field is carried out to obtain the distribution of displacement,stress and strain of caprock.In Ordos reservoir,the carbon dioxide plume migrates radially around the injection well,accompanied by vertical migration under the effect of density difference.Reservoir porosity has a great influence on carbon dioxide flow,followed by temperature and pressure,and salt water salinity has the least effect.The upper overburden of Shiqianfeng Formation uplifts upward under the action of gas pore pressure,but the displacement and strain of rock mass are small,which does not affect the safety of Ordos project.This study provides a theoretical basis for the early site selection of carbon dioxide storage project.