Temperature logs, which have been run routinely in The Geysers geothermal wells, have been used to indicate the depth corresponding to the top of the steam zone. This steam chest is marked by temperatures which exceed 400ºF and by a sharp change in temperature gradient. Above the steam chest heat transfer is largely by conduction, so that the gradient depends on heat flux and thermal conductivity. Within the steam chest, which is highly fractured, heat is transferred via the vertical fractures by convective reflux as well. This being a much more effective mechanism, the temperatures are more nearly isothermal. The …
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Temperature logs, which have been run routinely in The Geysers geothermal wells, have been used to indicate the depth corresponding to the top of the steam zone. This steam chest is marked by temperatures which exceed 400ºF and by a sharp change in temperature gradient. Above the steam chest heat transfer is largely by conduction, so that the gradient depends on heat flux and thermal conductivity. Within the steam chest, which is highly fractured, heat is transferred via the vertical fractures by convective reflux as well. This being a much more effective mechanism, the temperatures are more nearly isothermal. The existence of this abrupt gradient change has been confirmed directly in U.S. Geothermal C-4 and C-5, where the temperature was logged from the surface into the upper unproductive portion of the steam chest. This report describes a model of the heat transfer within the steam chest. By comparing the model with temperature gradient data from a well, one can estimate the average vertical permeability within the reflux system. The model suggests that the average vertical permeability at The Geysers is less than 1 md in the upper unproductive portion of the steam chest. Temperature data taken from this portion of the steam chest indicates that the reservoir is considerably less isothermal than previously assumed. The dynamic effects of the reflux system should be included in any study of transient well behavior or in any estimate of deliverable reserves. 3 refs., 2 figs.
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Hite, J.R. & Fehlberg, E.L.Steam Zone Temperature Gradients at The Geysers,
article,
December 1, 1976;
United States.
(https://digital.library.unt.edu/ark:/67531/metadc885796/:
accessed June 6, 2024),
University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu;
crediting UNT Libraries Government Documents Department.
