| Title | 3D MT Resistivity Imaging for Geothermal Resource Assessment and Environmental Mitigation at the Glass Mountain KGRA, California |
|---|---|
| Authors | Cumming, William; Mackie, Randall |
| Year | 2007 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Exploration; exploration geophysics resistivity magnetotellurics |
| Abstract | MT and TDEM surveys acquired in 2005 were integrated with existing MT and TDEM data recovered from obsolete formats to characterize the geometry of the geothermal reservoir in the Glass Mountain KGRA. The objectives of this project were to mitigate the drilling costs and environmental impact of the ongoing geothermal development at Glass Mountain by more efficiently focusing exploration wells on the most promising target zones. Although the 1D and 2D inversions used for the initial review of the MT were superior to the MT analyses completed in the 1980’s at Glass Mountain, advances made in 3D MT inversion over the course of the project led to its use as the primary tool in the resistivity interpretation. The improved MT imaging supported a detailed correlation of MT resistivity with data from 5 exploration wells and 21 temperature gradient holes, validating both the 3D MT computation and the interpretation of resistivity in geothermal settings based on the temperature sensitive clay transitions. An interpretation based on the correlation of the 3D MT resistivity with well properties indicated that most of the previous exploration wells had been targeted close to but not in the center of areas that appeared most likely to be permeable. Such characterizations can be considered in the context of both potential environmental impacts and reservoir engineering analyses in assessing drilling target priorities. The details of this Glass Mountain MT project are elaborated in a report to the California Energy Commission, currently under review. |