Natural State Modeling, Structure, Preliminary Temperature and Chemical Synthesis of the Dixie Valley, Nevada Geothermal Field

Abstract

A number of geothermal systems in the Basin and Range Province, like the ones in Dixie Valley, have subsurface temperatures in excess of 200?C, and even 250?C by 2ñ3 km depth. These systems are typically associated with Quaternary normal faulting (Caskey et al., 2000). Many of these systems are non-magmatic in origin, based on the helium isotope ratios in the hot water (Kennedy et al., 2000).

The classical conceptual model for these systems is that meteoric water enters via the ranges or through valley fill, warms during deep circulation, and ascends along the nearest, highest permeable pathway, usually an active range-bounding fault. A recent seismic, gravity, magnetic, and thermal synthesis of the Dixie Valley, Nevada geothermal system has shown that the system is much more complex and 3-dimensional that previously thought.

We have utilized this integrated geophysical image to provide structural control on a regional fluid flow model for the Valley-Range systems as well as reservoir specific models for the Dixie Valley production area to investigate several outstanding issues related to fluid recharge, and pathways, the basement permeability heterogeneity, and the sustainability of the high temperature reservoir with respect to episodic seismicity