PHENOMENA RELATED TO THE STORAGE OF NATURAL-GAS IN UNDERGROUND CAVERNS

This contribution reports on a preliminary study of various phenomena, that may occur during storage of natural gas in underground salt cave rns. In these caverns the following substances are present: natural ga s from different origins at pressures up to 300 bar, residual blanket (diesel oil), water and sodium chloride. In the caverns temperatures a s high as 353 K have to be expected. Retrograde condensation may occur at pressure release, not only in the caverns, but also in the various operating facilities. The first part of this study focuses on the var ious aspects that govern the phase behavior inside the cavern. By mean s of well-chosen model systems representative for natural gas and dies el oil (octadecane), the main features of phase behavior have been stu died. Also liquid dropout calculations were performed. Because natural gas is stored in the caverns for only a limited period, it is plausib le that inside the caverns concentration and temperature gradients wil l be present, resulting in a variety of time-dependent processes. In t he underlying study attention was also given to these aspects. Process es like molecular diffusion and free convection applied for simplified conditions have been studied, resulting in an insight how the dew poi nt and liquid dropout may change in time.