Away from the Range Front: Intra-Basin Geothermal Exploration

GeoGlobal Energy LLC (GGE) proposes to integrate several well-established rock mechanical technologies from mining, geotechnical, and academic practice but novel to geothermal exploration, to locate blind geothermal resource upflow along faults oriented for permeability away from the range front.

The project applies the known relationship between fault permeability and the mechanics of rocks under stress to reduce risks in exploration well targeting. Although the concept has been applied before, the project would innovate by dramatically increasing the detail and types of information on the mechanical state of the target area using a variety of low-cost measurements in advance of deep drilling. In addition to the mechanical data, holes into the shallow warm aquifer related to the thermal anomaly will allow analysis of chemical indicators of upflow as a more direct measure of the location of fault permeability.

The rock mechanics measurement strategy applies several stress and strain or offset measurement methods in order to more fully constrain the stress field and its variation across the area. Mechanical relationships between stress and strain will be used to integrate the field measurements and predict the orientation of permeable faults.

Project technologies include:

• Highly detailed and precise digital topography from airborne scanning laser data (LiDAR) to reveal recent fault offset patterns

• Over-coring stress measurement in 30 meter (100 ft.) holes into outcropping rock

• A laser trilateration strain network across the active fault zone to measure deformation

• Push-core holes to 30 m (100 ft.) into unconsolidated sediments to obtain temperature gradients, fluid samples, and stratigraphic markers at very low cost

• Trenching in a few selected locations to map recent offset history and fault dip

• Analyses of helium, oxygen, and standard fluid chemistry from shallow hole samples to identify upflow along with the shallow temperature data

• Slim well drilling followed by borehole image and permeability logging

Faults will be targeted with slim wells to discover a deep geothermal system in a prospect away from the range front in Gabbs Valley, Nevada. The exploration project will discover a resource expected to have temperatures from 150 to 260°C (300 to 500°F) and a capacity of about 30 MW.

Gabbs Valley is a blind prospect in an actively-faulted sedimentary basin with a very large geothermal heat anomaly in rural Nye and Mineral Counties.