| Abstract |
Fluid Inclusion Stratigraphy (FIS) is a new technique developed for the oil industry in order to map borehole fluids. This method is being studied for application to geothermal wells and is funded by the California Energy Commission. Fluid inclusion gas geochemistry is analyzed and plotted on well log diagrams. The working hypothesis is that select gaseous species and species ratios indicate areas of groundwater and reservoir fluid flow and reservoir seals. Analyses from multiple boreholes should show the stratigraphy of subsurface fluids. Analyses are performed by a commercial laboratory, Fluid Inclusion Technologies. The FIS method modified for use on the Coso geothermal system has produced preliminary results indicating that reservoir assessment is possible. Approximately 1,700 samples from three producing and one non-producing well have been analyzed. Preliminary results show megascopic trends and much fine scale detail when the logs are analyzed in detail. Select species including carbon dioxide, nitrogen, argon, methane, and hydrogen sulfide show distinct differences between producing and non-producing wells as well as indicating fluid flow and locations of major fracture zones. Additional interpretation of the preliminary results and method will include consistency of results from one borehole to another, agreement of FIS with well logs, and appraisal of FIS analyses on well testing decisions, well completion strategies, and in resource calculations. |