Steam-water Relative Permeabilities for the Cerro Prieto Geothermal Reservoir

We have refined a method used previously by several authors to estimate water-steam relative permeabilities. Our version provides also reasonable estimates of the corresponding saturations. It relies on production output data obtained by means of short tests. This constitutes a distinct advantage over the previous variants, which require long-term production data, because it allows early accurate assessments of reservoir reserves and producibility. Applying the refined version to data from 5 Cerro Prieto wells we obtained the corresponding relative permeabilities. These results ind 1 ca t e that the re lat ive permeabilities are remarkably homogeneous over a wide area of the field, and over a considerable fraction of the reservoir thickness. They also provide independent evidence that fracture flow is important in Cerro Prieto. Finally, comparison of our results with those found for Wairakei shows that the relative permeabilities of geothermal reservoirs can be sensitively site-dependent.