The application of transient pressure analysis methods to vapor-dominated geothermal systems has generally been done using methods developed for noncondensable gas reservoirs. These methods have been satisfactory in many cases; however, because they neglect effects of vaporization and condensation, the results may be misleading. The study presented here was motivated by a perceived potential need to incorporated phase changes into the analysis of pressure drawdown and recovery data. It is hoped that this will allow for an increased understanding of the processes occurring in geothermal systems where steam and liquid water are thought to coexist: A finite - difference model for the horizontal, radial flow of steam in the presence of an immobile vaporizing or condensing liquid phase was adapted from the model of Moench (1976). Results were generated for real physical parameters, and are presented in terms of standard dimensionless pressure ( actually pressure squared) and time groupings. The analysis assumes an initial constant temperature and pressure in the aquifer and an initial uniform liquid-water distribution which partially fill s the void space. It is also assumed that the steam and liquid water in the reservoir are in local thermal equilibrium with the reservoir rocks and t h at temperature changes occur only in response to phase changes. In the examples which follow permeability, porosity, and well discharge are constant.

Press the Back button in your browser, or search again.

Copyright 1977, Stanford Geothermal Program: Readers who download papers from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the original publisher.