Application of Fluid Inclusion Stratigraphy Analysis to Geothermal Systems

Abstract

We report on the application to geothermal systems of Fluid Inclusion Stratigraphy (FIS) analysis developed for the oil industry. Borehole cuttings are collected at 6 m spacing and fluid inclusion gases analysed in vacuum by mass spectrometry; the cost is comparable to other logging methods at about US$6,000 to US$10,000 per well. Geothermal system FIS analyses show fracture locations and indicate general fluid inclusion gas chemistry and gas ratios from which fluid type, seal locations and fluid boiling are inferred. Locations of fluids with elevated H2S and benzene are determined. Fence diagrams are constructed that show geothermal system fluid stratigraphy.