Modelling pressure and temperature profile in a CO2 injection well

Abstract

In cases where CO2 is transported over long distances onshore or locally compressed offshore the temperature at the wellhead will typically be below 31 °C. If the well head pressure is below the saturation pressure two phases will occur at the injection point. A model of the injection well, taking into account the phase changes, adiabatic heating and thermal exchange with the surrounding rock down through the well has been developed to predict the phases’ density, pressure and temperature profiles along the well. A practical application of the model on the injection well in the Sleipner CO2 storage project was used to constrain the independent variables in a case where neither the pressure nor temperature is measured in the well. Despite the fact that the well is long and strongly deviated allowing good thermal contact between the well fluids and the rock the flow approaches adiabatic condition within few months. Injection is regularly stopped in the well for one to two weeks for servicing the well but this is not sufficiently long period to change this situation. With small modifications the same model can also be used model the transient behaviour of a CO2 well blowout or to model a leakage flow from a reservoir to the surface.