DOUBLE ADVECTIVE EFFECTS CONTROLLING LIQUID INJECTION IN GEOTHERMAL RESERVOIRS

We examine the motion of liquid injected into a liquid dominated geothermal reservoir, focusing on the situation in which the injected liquid has different temperature and composition from the reservoir fluid. As a result of these differences, the injected liquid will typically be of different density to the reservoir fluid, and will therefore spread through the reservoir under gravity. Owing to the thermal inertia of porous rock, as the injected liquid spreads through the rock, the thermal front lags behind the actual fluid front associated with the injected liquid. As a result, the density of the injected fluid changes across the thermal front: fluid ahead of the front has density different from that in the reservoir only as a result of differences in composition; fluid behind the front has density which is different owing to contrasts in temperature and composition. This leads to a change in the structure of the current across the thermal front, and we examine a range of different situations which may develop depending on the initial temperature and compositional contrasts