2-M Probe Survey

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Exploration Technique: 2-M Probe Survey

Exploration Technique Information
Exploration Group: Field Techniques
Exploration Sub Group: Data Collection and Mapping
Parent Exploration Technique: Data Collection and Mapping
Information Provided by Technique
Thermal: Identify and delineate shallow thermal anomalies
Cost Information
Low-End Estimate (USD): 200.0020,000 centUSD
0.2 kUSD
2.0e-4 MUSD
2.0e-7 TUSD
/ station
Median Estimate (USD): 300.0030,000 centUSD
0.3 kUSD
3.0e-4 MUSD
3.0e-7 TUSD
/ station
High-End Estimate (USD): 500.0050,000 centUSD
0.5 kUSD
5.0e-4 MUSD
5.0e-7 TUSD
/ station
Time Required
Low-End Estimate: 1.50 hours1.711157e-4 years
0.0625 days
0.00893 weeks
0.00205 months
/ job
Median Estimate: 2 hours2.281542e-4 years
0.0833 days
0.0119 weeks
0.00274 months
/ job
High-End Estimate: 3 hours3.422313e-4 years
0.125 days
0.0179 weeks
0.00411 months
/ job
2-M Probe Survey:
Probe surveys are used to physically identify and delineate thermal anomalies. A 2-m long hollow steel tube with a tungsten-carbide alloy tip is driven into the ground using a hammer drill. Then a high-precision resistive-temperature device is inserted into the tube. The probe is then left in place for at least one hour.
Other definitions:Wikipedia Reegle

The use of shallow temperature measurements has allowed for detection of deeper geothermal aquifers in many documented cases since the early 1980s. Also, these shallow measurements have successfully detected blind systems in the Great Basin without any surface manifestations. Collecting shallow temperatures between 1-2m is much lower in cost than drilling a temperature gradient well and much easier to complete because of fewer regulations.

2 m temperature probe survey being conducted via ATV. Photo featured on the Great Basin Center for Geothermal Energy website.[1]

Use in Geothermal Exploration
A 2m probe survey is a key field exploration technique. The results of a 2m probe survey are used to approximate the temperatures of deeper geothermal systems and to map thermal anomalies to find blind geothermal systems. These surveys are only effective if the geothermal system is not overlain by a cold groundwater aquifer which will mask the temperature anomaly that could be seen in a shallow survey. Shallow temperature surveys will often be conducted previous to drilling a temperature gradient well. The influence of solar radiation and seasonal temperature variations is mostly damped out past a depth of 1 m below the surface.
Related Techniques
A modified version of the 2 m temperature probe survey was tested at the Salt Wells Geothermal Area in 2005.[2] This technique was used to measure temperatures at relatively shallow depths of 30 cm, adapted for sites where the water table is at or near the land surface. The 30-cm probe survey technique uses a 1/8 inch diameter, 30-cm-long digital K-type thermocouple and probe to measure shallow temperatures at each sample point. Temperature measurements are taken by inserting the probe into the ground by hand, and require minimal equilibration times of 1-2 minutes owing to the small thermal mass of the device and the level of water saturation of the measured sediments. Temperature surveys at Salt Wells were conducted during the winter in February 2005, when background temperatures at 30 cm depth were near a seasonal minimum of 3 to 10°C. A continuous temperature test is also required for the application of this technique, in order to demonstrate the stability of temperatures at 30 cm depth and to provide a baseline dataset for distinguishing thermal anomalies from background temperature variations. At Salt Wells, the continuous 24 hour temperature test was conducted using a 3-wire Platinum Resistance Temperature Device (Pt-RTD) in February 2006, and showed that temperatures only varied by +/- 0.1°C during the day. From this data, it was determined that a temperature threshold of 12°C was sufficient to distinguish thermal anomalies from background temperatures at the site.

Environmental Mitigation Measures
The use of off road vehicles should avoid overland travel during periods when soils are moist or wet. Backfilling of excavated probe holes.

Data Access and Acquisition
The temperature at 1-2 m below the ground is measured by a thermocouple probe or a thermistor. There are different methods to create the hole in which the thermocouple probe or thermistor is inserted into to acquire the data. Some examples include using a hand soil auger or using a hammer drill. The best method is dependent on the soil type at the site and any time constraints.
Best Practices
Probes can be arrayed in any manner desirable, but initial reconnaissance should be in a grid or in transects across and along faults, if known.
Potential Pitfalls
The potential problems with drilling the hole using a hand soil auger are that the temperature measurement could be influenced by shallow soil entering the hole, rocky soils are difficult to penetrate, and the holes may collapse if drilled in loose ground. The potential problems with using a thermistor instead of a thermocouple probe is that it is much more delicate and could be damaged during the creation of the 2m hole.

NEPA Analysis
This exploration technique may be approved on federally managed lands by conducting a categorical exclusion (CX) analysis. Off road travel can be accomplished using existing roads and ways using ATV's and off road transportation. Access can be accomplished by using horses or by foot in areas closed to off road vehicles. An EA may be required in project areas that contain resources with a potential for impacts.
Additional References
Mark F. Coolbaugh,Chris Sladek,James E. Faulds,Richard E. Zehner,Gary L. Oppliger. 2007. Use of Rapid Temperature Measurements at a 2-Meter Depth to Augment Deeper Temperature Gradient Drilling. In: Proceedings of Thirty-Second Workshop on Geothermal Reservoir Engineering. Thirty-Second Workshop on Geothermal Reservoir Engineering; 2007/01/22; Stanford, CA. Stanford, CA: Stanford University, Stanford Geothermal Program; p. 109-116

Christopher Kratt,Mark F. Coolbaugh,Bill Peppin,Chris Sladek. 2009. Identification of a New Blind Geothermal System with Hyperspectral Remote Sensing and Shallow Temperature Measurements at Columbus Salt Marsh, Esmeralda County, Nevada. In: Transactions. GRC Annual Meeting; 2009/10/04; Reno, NV. Davis, CA: Geothermal Resources Council; p. 481–485

Chris Sladek,Mark F. Coolbaugh,Christopher Kratt. 2009. Improvements in Shallow (Two-Meter) Temperature Measurements and Data Interpretation. In: Transactions. GRC Annual Meeting; 2009/10/04; Reno, NV. Davis, CA: Geothermal Resources Council; p. 535–541

Justin Skord,Patricia H. Cashman,Mark Coolbaugh,Nicholas Hinz. 2011. Mapping Hydrothermal Upwelling and Outflow Zones: Preliminary Results from Two-Meter Temperature Data and Geologic Analysis at Lee Allen Springs and Salt Wells Basin. In: Transactions. GRC Annual Meeting; 2011/10/23; San Diego, CA. Davis, CA: Geothermal Resources Council; p.

  1. Great Basin Center for Geothermal Energy: Facilities Overview
  2. Mark F. Coolbaugh,Chris Sladek,Chris Kratt,Lisa Shevenell. 2006. Surface Indicators of Geothermal Activity at Salt Wells, Nevada, USA, Including Warm Ground, Borate Deposits, and Siliceous Alteration. In: Transactions. GRC Annual Meeting; 2006/09/10; San Diego, California. Davis, CA: Geothermal Resources Council; p. 399-405

Page Area Activity Start Date Activity End Date Reference Material
2-M Probe At Desert Peak Area (Sladek, Et Al., 2007) Desert Peak Area 2007 2007

2-M Probe Survey At Chena Geothermal Area (Wescott & Turner, 1982) Chena Geothermal Area 1973 1974

2-M Probe Survey At Coso Geothermal Area (1977) Coso Geothermal Area 1977 1977

2-M Probe Survey At Coso Geothermal Area (1979) Coso Geothermal Area 1979 1979

2-M Probe Survey At Coso Geothermal Area (2007) Coso Geothermal Area 2007 2007

2-M Probe Survey At Dixie Valley Geothermal Area (Skord, Et Al., 2001) Dixie Valley Geothermal Area 2010 2011

2-M Probe Survey At Salt Wells Area (Coolbaugh, Et Al., 2006) Salt Wells Geothermal Area 2005 2006

2-M Probe Survey At Salt Wells Area (Skord, Et Al., 2011) Salt Wells Geothermal Area 2011 2011

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