Model for Predicting Wellbore Temperature and Pressure in Offshore CO2 Storage Wells and the Influencing Factors

The CO2 physical parameters are greatly influenced by the wellbore temperature and pressure during the offshore burial process, but the existing model does not take this into account resulting in poor calculation accuracy, which brings large errors to the later wellbore load calculation and wellbore integrity evaluation. Based on heat transfer and other basic theories, a wellbore temperature and pressure calculation model was established. the calculation method of CO2 physical parameters required for the model was determined, and finally the established model was solved by iterative calculations to obtain the temperature and pressure distribution of the wellbore and the change law of physical parameters, and the effect of injection parameters on the wellbore temperature and pressure was analyzed. Taking a buried well in the South China Sea as an example, the analysis found that as the well depth increased, the wellbore temperature and pressure increased approximately linearly, and constant pressure specific heat capacity, Nusselt number and convective heat transfer coefficient of CO2 fluid increased, while the density, viscosity, friction coefficient, thermal conductivity and Prandtl number decreased. An increase in injection temperature decreases the temperature gradient, but has little effect on the pressure gradient and bottomhole temperature and pressure; an increase in injection volume decreases the temperature gradient and increases the pressure gradient, and the bottomhole temperature can be effectively regulated by the injection volume; the injection pressure has a certain effect on the temperature gradient at low pressure, but has a most no effect on the pressure gradient, and the bottomhole pressure can be effectively regulated by the injection pressure.