Nereidas Valley, Caldas, Colombia

Key Project Information

Purpose: Geothermal Exploration for Electric Power Generation
Method: Double Blind Magnetotelluric (MT) Survey / Broadband Magnetotellurics (BMT) and Low-frequency Magnetotellurics (LMT) Geologic Model Creation
Location: Nereida Valley, Caldas, Colombia
Client: Empresas Públicas Medellín(EPM)/Central Hidroeléctrica Caldas(CHEC)
End-User: Empresas Públicas Medellín
Dates: January - August 2013
Main Survey Area: 52 km2
Total number of MT Stations: 386
Client Reference: Mr. Santiago Villegas, Vice President CHEC

Project Summary

Dewhurst Group, L.L.C. (DG) was competitively selected by EPM/CHEC to conduct a high-resolution MT survey in the Nereidas Valley at the base of Volcan Nevado del Ruiz and provide drilling recommendations. DG exclusively provided all MT information used for the project. The Nereidas valley is located approximately 18 kilometers South East of the city of Manizales a region known for an abundance of recreational hot springs. Other project methods included geologic mapping, geochemistry, and reservoir modeling provided by Thermochem and a partnership with RESPEC. DG was responsible for all final resistivity imaging.

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

  • 384 BMT stations (soundings)
  • 33 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
  • 13 BMT Profiles
  • 14 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.

Health Safety and Environment

DG is committed to minimally disturb the land, stimulating the local economy and respect for indigenous culture through its EEC method for geothermal development. DG supported the local youth in and adjacent to the study area by organizing a "Children's Day" event that took place in the rural school of the sector. No personal injuries were incurred during this accident-free survey.

Schedule and Budget

All field work was completed within the scheduled time frame despite many impediments to field work and the final results delivered within approximately 60 days of data acquisition. All work was completed below DG's initial estimate.