CO2 injection in low pressure depleted reservoirs

Abstract

Re-using depleted fields (and platforms and wells) offers advantages over developing storage projects in saline formations. However, with reservoir pressures after production sometimes below 20 bar, there can be a large pressure difference between the reservoir and the transport pipeline at the surface, which will be typically at pressures in the range of 80 - 120 bar. This pressure difference must be carefully managed to ensure that the temperature of the CO2, the surface installations and the well, remain within materials specifications and within proper operating boundaries. Pressure drops of the CO2 result in potentially large decrease in temperature, due to its high Joule-Thomson coefficient; in addition, the temperatures and pressures that occur in a typical CO2 transport and storage system are such that two-phase flow is likely to occur. Pipeline pressure and temperature management can easily be done in a single source- single sink scenario as the pipeline pressure is a free parameter. However, if the pipeline must act as a backbone for multiple wells at different reservoir pressure, pressure and flow management must be balanced carefully. In this paper, the differences between a pipeline as transport and a pipeline as backbone will be discussed in detail.