| Abstract |
A mathematical model for vertical fluid and heat flow in two-phase geothermal reservoirs containing non-condensible gas is described. The equations for conservation of water, and energy are solved for steady-state conditions; binary diffusion effects in the gas phase are included. Cases with net mass throughflowsof water and are treated, as well as examples balanced liquid-vapour counterflow. In a typical case it is found that, at the top, a "wedge"of partial pressure is present; this partial pressure decreases with depth, decaying to zero if there is no net throughflowof gas. Where there is a net throughflow, the wedge tapers almost to zero but then increases slowly again at greater depths. The parameters which control the partial pressure deeper in the system are investigated in this paper. The inverseproblem of determining diffusion parameters and relative saturation relationships is also studied. It seems that accuracy in field measurements would have to be much greater than present instruments and techniques allow in order that useful relationships be deduced. Quantitative estimates are made of the accuracy required. |