Key Project Information

Purpose: Geothermal Exploration for Electric Power Generation (six areas)
Method: Double Blind Magnetotelluric (MT) / Survey Broadband Magnetotellurics (BMT) and Low-frequency Magnetotellurics (LMT)
Location: Basin and range Province and Mohave Desert, Nevada, USA
Client: Sunrise Engineering, Inc.
End-User: Southern Nevada Water Authority (SNWA), 100 City Parkway, Suite 700, Las Vegas, NV 89106
Dates: 2009 - 2010
Main Survey Area: 45 km2
Extended Survey Area: 85 km2
Total number of MT Stations: 533
Client Reference: Charles C. Rehn, P.E., formerly with Sunrise, now with AMEC, 9865 South 500 West, Sandy, Utah 84070 US Telephone: +1 801 999 2002

Project Summary

The Dewhurst Group (DG) was competitively selected by Sunrise Engineering, Inc. to conduct geothermal exploration within the Basin and Range Province and at the edge of the Mojave Desert in eastern, southern, and central Nevada. Comprehensive, double-blind LMT and BMT soundings were taken at over 500 stations across 6 independent survey sites, covering a total surface area of 45km2. The DG provided all of the resistivity data collection and analysis (1-D, 2-D, 2.5-D, and 3-D OCCAM inversions), as well as geologic interpretation for the project. Results included the identification of multiple drilling target locations and perhaps the longest observed magnetotelluric profile available for this area, covering a distance of over 85km. Expert DG personnel from Finland and Russia were included in the work. Results were delivered in near-real time, and the entire survey was completed in 135 days. Following the survey, Sunrise submitted results to their client, a large Nevada utility, who has successfully test-drilled and confirmed target sites identified by the DG.

Statement of Work

Work was performed using a phased approach:

™™Phase 1: Test and Design

  • Calibration, geo-electric strike and dimensionality analysis
  • Survey Design

™™Phase 2: Field Work

  • 449 BMT stations (soundings)
  • 84 LMT stations
  • Near-real time processing in the field

™™Phase 3: Data Analysis

  • Calculation of transfer functions
  • 1-D station inversions
  • 2-D profile inversions
  • 39 BMT Profiles
  • 33 LMT Profiles

™™Phase 4: 3-D modeling and Final Report

  • 3-D renderings from 1-D results
  • 3-D renderings from 2-D results (e.g., 2.5-D inversion)
  • 3-D unconstrained inversions
  • Comparison of all results for robust resistivity imaging and interpretation

Final products and deliverables included:

  • ™™Written Project Report
  • ™™Drilling Recommendations
  • ™™Digital Data

All MT data were acquired using DG proprietary (e.g., non-commercial) instrumentation, techniques, analysis tools and software.

Environment, Safety, and Cultural Awareness

The DG is committed to minimally disrupting the land, stimulating the local economy, and respecting local culture. DG’s methods: 1) Are non-ground-disturbing; 2) Do not require an Environmental Impact Statement under the National Environmental Policy Act of 1969; and 3) Qualified for a Finding of No Significant Impact (FONSI). Further, the DG coordinated all field work with the Southern Nevada District Office of the US Bureau of Land Management, client-provided archeologists and botanists. All members of the field crew received site-specific training from the BLM and were debriefed on noninvasive procedures for respecting local fauna, including such endangered species as the Mojave Desert tortoise. This was an injury-free survey despite the hazardous environments encountered.

Schedule and Budget

All field work was completed within 135 days and final results were delivered within 60 days of data acquisition. Work was completed well within budget, with a savings of approximately 23% below the initial estimate.